Co-reporter:Junjie Bao;Qingxia Du;Minghao Gao;Yu Shao;Zhongfeng Tang;Bangkun Zou
ACS Applied Materials & Interfaces December 21, 2016 Volume 8(Issue 50) pp:34879-34887
Publication Date(Web):November 29, 2016
DOI:10.1021/acsami.6b11431
A complete and ordered layered structure on the surface of LiNi0.815Co0.15Al0.035O2 (NCA) has been achieved via a facile surface-oxidation method with Na2S2O8. The field-emission transmission electron microscopy images clearly show that preoxidation of the hydroxide precursor can eliminate the crystal defects and convert Ni(OH)2 into layered β-NiOOH, which leads to a highly ordered crystalline NCA, with its (006) planes perpendicular to the surface in the sintering process. X-ray photoelectron spectroscopy and Raman shift results demonstrate that the contents of Ni2+ and Co2+ ions are reduced with preoxidization on the surface of the hydroxide precursor. The level of Li+/Ni2+ disordering in the modified NCA determined by the peak intensity ratio I(003)/I(104) in X-ray diffraction patterns decreases. Thanks to the complete and ordered layered structure on the surface of secondary particles, lithium ions can easily intercalate/extract in the discharging–charging process, leading to greatly improved electrochemical properties.Keywords: cation disorder; crystal defect; lithium-ion battery; lithium−nickel−cobalt aluminum oxide; sodium peroxodisulfate; surface oxidation;
Co-reporter:Xu-Yong Feng, Chen Shen, Hong-Fa Xiang, Han-Kang Liu, Yu-Cheng Wu, Chun-Hua Chen
Journal of Alloys and Compounds 2017 Volume 695() pp:227-232
Publication Date(Web):25 February 2017
DOI:10.1016/j.jallcom.2016.10.186
•Good electrochemical performances of the microwave assist cathode material.•A clear relationship between the structure and the electrochemical performances.•Fast discharge leads to partially over-discharge, which leads to a faster capacity decay.LiNi0.5Mn1.5O4 spinel samples are synthesized through a citric acid method using either microwave heating or oven heating to prepare the precursor gel. Contrast to the oven heating, the microwave heating is a fast way to obtain a homogenous precursor gel and remove all the crystal water with a higher heating temperature. The product synthesized with this method is of different fine structure and higher purity of LiNi0.5Mn1.5O4. As a result, the LiNi0.5Mn1.5O4 obtained from microwave heating shows better rate performance with a high capacity of about 122 mAh g−1 at 10C, which is 92% of the capacity at 1C (131 mAh g−1). The cycling performance of this product at the rate of 1C is also impressive with about 95% of its initial capacity retained after 200 cycles (125 mAh g−1). When the current increases to 10C rate, the cycling performance becomes worse due to the increase in impedance during cycling. At the same time, part of the sample is over-discharged and transformed to a tetragonal phase at a high discharge current of 10C and become electrochemical irreversible, resulting to the capacity loss. The energy density (521 Wh/kg) of the microwave assist sample is also pretty high at high rate of 10C, due to the good rate performance.
Co-reporter:He-Yang Wang, Jia-Ying Liao, Bang-Kun Zou, Zhong-Feng Tang, Xin Sun, Zhao-Yin Wen, Chun-Hua Chen
Materials Letters 2017 Volume 186() pp:326-329
Publication Date(Web):1 January 2017
DOI:10.1016/j.matlet.2016.10.027
•Na2Ti3O7 is successfully prepared by a facile moderate method.•In-situ carbon network without additional carbon sources can be obtained.•Na2Ti3O7/C shows remarkable long cycle life at 0.2 C, after 400 cycles without showing capacity or voltage decay.A sodium titanate-carbon (Na2Ti3O7/C) composite as an anode material for sodium-ion batteries (SIBs) is successfully synthesized via a moderate method (500 °C). It can deliver charge capacities of 161 mA h g−1 and 91 mA h g−1 at current densities of 0.05 C and 10 C, respectively. The material can be cycled at 0.2 C for 400 cycles without capacity or voltage decay. This low cost and environmentally friendly Na2Ti3O7/C exhibits excellent electrochemical performance.
Co-reporter:Miao-Miao Deng;Bang-Kun Zou;Yu Shao
Journal of Solid State Electrochemistry 2017 Volume 21( Issue 6) pp:1733-1742
Publication Date(Web):06 March 2017
DOI:10.1007/s10008-017-3545-z
The 5V-positive electrode materials LiNi0.45M0.05Mn1.5O4 (M = Cu, Mg and Zn) are synthesized via a thermopolymerization method. Scanning electron microscopy and X-ray diffraction analyses indicate that these doped LiNi0.45M0.05Mn1.5O4 samples remain their spinel structure with an octahedral morphology. According to the results of infrared spectroscopy, Cu2+ and Mg2+ ions take partially the place of Ni2+ ions and occupy the 4b sites of the P4332 space group, while Zn2+ ions occupy the 8a sites of the Fd3m space group by displacing some Li+ ions originally at the 8a sites into the 16d sites. The LiNi0.45Cu0.05Mn1.5O4 and LiNi0.45Mg0.05Mn1.5O4 samples exhibit excellent rate performance with specific capacities of 98.3 and 92.4 mAh g−1, respectively, at the charge–discharge rate of 10 C, while the LiNi0.5Mn1.5O4 sample delivers only 78.9 mAh g−1 at 10 C. Besides, the LiNi0.45Cu0.05Mn1.5O4 and LiNi0.45Mg0.05Mn1.5O4 samples show good capacity retention at high temperature (55 °C) with the capacities of 117.6 and 119.5 mAh g−1, respectively, after 100 cycles at 1 C.
Co-reporter:Ran Yu, Yi Sun, Bang-Kun Zou, Miao-Miao Deng, Jing-Ying Xie, Chun-Hua Chen
Journal of Power Sources 2017 Volume 340(Volume 340) pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.jpowsour.2016.11.084
•The slurry spray deposition (SSD) process for laminate preparation is developed.•A comparison is made between the SSD and blade coating samples.•The SSD sample exhibits improved mechanical and high rate properties.A slurry spray deposition (SSD) process is utilized to prepare a LiNi0.5Mn1.5O4-based composite electrode supported on an aluminum foil. The spray deposition process is performed at room temperature through the atomization and deposition of the composite electrode slurry. A comparative LiNi0.5Mn1.5O4-based composite electrode is also prepared by the traditional blade coating method. The surface morphology and elements mapping of the electrodes are measured by scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The adhesion between the composite electrode layers and the aluminum foil is also tested. A parallel evaluation on the mechanical and electrochemical performances of the two kinds of electrodes is conducted. The SSD electrode exhibits improved adhesion, cycling stability and rate capability. Therefore, the SSD process is an effective way to fabricate advanced electrodes for high performance lithium ion cells.
Co-reporter:Jiaying Liao;Qiao Hu;Yingtao Yu;Heyang Wang;Zhongfeng Tang;Zhaoyin Wen
Journal of Materials Chemistry A 2017 vol. 5(Issue 36) pp:19017-19024
Publication Date(Web):2017/09/19
DOI:10.1039/C7TA05460B
K-ion batteries, as an emerging battery system, have attracted tremendous attention in the research community. Herein, we report a K-ion full-cell based on a nano-sized K1.92Fe[Fe(CN)6]0.94·0.5H2O cathode, dipotassium terephthalate (K2TP)@carbon nanotube (CNT) anode and an optimized electrolyte. K1.92Fe[Fe(CN)6]0.94·0.5H2O delivers a high capacity of 133 mA h g−1 with 92.8% capacity retention after 200 cycles and high coulombic efficiency of 98.5%. The side reactions of K metal with the electrolyte are suppressed in KClO4/propylene carbonate (PC). The K2TP nanosheets grown in situ on the CNT show a high reversible capacity of about 250 mA h g−1 and an ultra-high rate capability. The full-cells based on them are well cycled in a DME-based electrolyte and show a great promise for large-scale energy storage.
Co-reporter:Ran Yu, Jun-Jie Bao, Tian-Tian Chen, Bang-Kun Zou, Zhao-Yin Wen, Xiang-Xin Guo, Chun-Hua Chen
Solid State Ionics 2017 Volume 309(Volume 309) pp:
Publication Date(Web):15 October 2017
DOI:10.1016/j.ssi.2017.06.013
•TPU-Li7La3Zr2O12 hybrid solid electrolyte exhibits a high ionic conductivity.•An all-solid-state cell based on TPU solid electrolyte is assembled and evaluated.•LFP/solid electrolyte/Li cells deliver a high capacity of 160 mAh g− 1.In this paper a new kind of solid polymer electrolyte (SPE) based on thermoplastic polyurethane (TPU) is fabricated. With the dispersion of Li7La3Zr2O12 powders, the lithium ionic conductivity of the SPE can be improved effectively. By optimizing the amount of Li7La3Zr2O12, an ionic conductivity of 8.89 × 10− 5 S cm− 1 at 80 °C is achieved. X-ray diffraction and scanning electron microscopy are employed to analyze the crystallinity and microstructure of the SPE samples. The all-solid-state lithium ion cells with the TPU-based SPE as solid electrolyte and LiFePO4 as active cathode material are assembled through a simple blade-coating method. Such all-solid-state cells exhibit a specific capacity (160 mAh g− 1) comparable with the traditional cells using organic liquid electrolyte at the current density of 5.3 μA cm− 2. To further investigate the electrochemical performances of the all-solid-state cells, the cyclic voltammetry and galvanostatic cycling are also performed and analyzed.
Co-reporter:Jun-Jie Bao, Bang-Kun Zou, Qin Cheng, Yi-Ping Huang, Fan Wu, Ge-Wen Xu, Chun-Hua Chen
Journal of Membrane Science 2017 Volume 541(Volume 541) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.memsci.2017.06.083
•Free-standing LiFePO4-based cathode is fabricated by a simple phase inverse technique.•The special pore structure in LFP/TPU/SP improves the rate capacity.•The LFP/TPU/SP electrodes exhibits flexibility and excellent dimensional stability.A series of flexible and free-standing cathodes with different mass ratios of LiFePO4, thermoplastic polyurethane (TPU) and super P (SP) (LFP/TPU/SP) are fabricated by a phase separation process. The obtained cathode membranes show highly porous and interwoven network structure, and possess excellent cycling stability and rate capability. The electrolyte uptake, electrochemical impedance spectra (EIS) and the apparent Li+ diffusion coefficient (DLi+) tests indicate that the porous polyurethane networks promote the electrolyte infiltration and accelerate Li ions transformation. Compared with the traditional cathode, the cathode prepared at the LFP/TPU/SP ratio of 4:5:1 (wt:wt) presents a much better rate capability than the traditional one. It delivers a discharge capacity of 153 and 93 mA h g−1 at 0.2C and 10C rates, respectively. The phase separation process is inexpensive and environmentally friendly, which provides a promising way to fabricate flexible and free-standing cathode.
Co-reporter:Xiang Ding 丁翔;Bangkun Zou 邹邦坤;Yuxuan Li 李禹宣;Xiaodong He 贺晓东
Science China Materials 2017 Volume 60( Issue 9) pp:839-848
Publication Date(Web):30 August 2017
DOI:10.1007/s40843-017-9083-9
Through meticulous design, a Li-lacking Cr2O5 cathode is physically mixed with Li-rich Li1.2Ni0.13Co0.13Mn0.54O2 (LNCM) cathode to form composite cathodes LNCM@xCr2O5 (x = 0, 0.1, 0.2, 0.3, 0.35, 0.4, mass ratio) in order to make use of the excess lithium produced by the Li-rich component in the first charge-discharge process. The initial coulombic efficiency (ICE) of LNCM half-cell has been significantly increased from 75.5% (x = 0) to 108.9% (x = 0.35). A novel full-cell comprising LNCM@Cr2O5 composite cathode and Li4Ti5O12 anode has been developed. Such electrode accordance, i.e., LNCM@Cr2O5//Li4Ti5O12 (“L-cell”), shows a particularly high ICE of 97.7%. The “L-cell” can transmit an outstanding reversible capacity up to 250 mA h g−1 and has 94% capacity retention during 50 cycles. It also has superior rate capacities as high as 122 and 94 mA h g−1 at 1.25 and 2.5 A g−1 current densities, which are even better in comparison of Li-rich//graphite full-cell (“G-cell”). The high performance of “L-cell” benefiting from the well-designed coulombic efficiency accordance mechanism displays a great potential for fast charge-discharge applications in future high-energy lithium ion batteries.本文将缺锂态的Cr2O5正极材料与Li1.2Ni0.13Co0.13Mn0.54O2(LNCM)富锂相正极材料进行物理混合, 形成了复合正极材料LNCM@xCr2O5(x = 0,0.1,0.2,0.3,0.35, 0.4), 从而在第一次充放电过程中达到有效利用富锂相所产生的不可逆的锂离子. 复合之后, LNCM半电池的首次库仑效率(ICE)得到显著提高, 从75.5(x = 0)提高到了108.9(x = 0.35). LNCM@Cr2O5复合正极材料和Li4Ti5O12负极材料匹配而成的新型锂离子全电池, 即LNCM@Cr2O5//Li4Ti5O12(L电池)表现出高达97.7的ICE. 不仅如此, L电池还表现出了高达250 mA h g—1的可逆容量, 并且 在循环50次之后仍具有94%的容量保持率. 此外, 在1.25和2.5 A g—1电流密度下, 它还具有高达122和94 mA h g—1的放电比容量, 远远优于LNCM//石墨全电池(G电池). L电池的高性能得益于精心设计的库仑效率匹配机制, 并且在未来高能量锂离子电池的快速充放电应用中表现出巨大的潜力.
Co-reporter:Qiao Hu, Bang-Kun Zou, Jia-Ying Liao, Mu-Fan Yu, Zhao-Yin Wen, Chunhua Chen
Journal of Alloys and Compounds 2017 Volume 717(Volume 717) pp:
Publication Date(Web):15 September 2017
DOI:10.1016/j.jallcom.2017.04.313
•A process to synthesize in-situ graphene-coated Li3V2(PO4)3 powders is developed.•Polyvinyl alcohol is a better carbon source than citric acid to result in graphene-like coating layers.•Li3V2(PO4)3@graphene exhibits superior electrochemical properties.A graphene-coated Li3V2(PO4)3 (LVP) powder (LVP@G) is synthesized via a two-step solid-state-reaction process. The graphene is converted in-situ from polyvinyl alcohol (PVA) or citric acid as a carbon source with the VOx-containing intermediate product as a catalyst. The results of two carbon sources (PVA and citric acid) are compared. X-ray diffraction, scanning/transmission electron microscopy and Raman spectroscopy are employed to study the compositions and structures. Cyclic voltammetry, galvanostatic cell cycling and electrochemical impedance spectroscopy are used to characterize the electrochemical performances. It is found that citric acid as a comparative carbon source leads to less amount of carbon residue than PVA. Also, the degree of graphitization of the carbon from citric acid is smaller than that from PVA. The LVP@G formed with PVA as the carbon source delivers a superb rate electrochemical performance with discharge capacity of 112.7 mAh·g−1 at 20C rate in the voltage range of 3.0–4.8 V.
Co-reporter:Bangkun Zou, Qiao Hu, Danqi Qu, Ran Yu, Yuting Zhou, Zhongfeng Tang and Chunhua Chen
Journal of Materials Chemistry A 2016 vol. 4(Issue 11) pp:4117-4124
Publication Date(Web):12 Feb 2016
DOI:10.1039/C6TA00069J
Nano-spherical Li-rich cathodes and MnxCo1−xO anodes are synthesized from as-solvothermal MnxCo1−xCO3 (x = 1, 0.8, and 0.5) precursors. Based on the half-cell studies of these materials, Li-rich 0.5Li2MnO3·0.5LiMn0.5Ni0.5O2 with a high reversible capacity of 247 mA h g−1 and binary transition metal oxide Mn0.8Co0.2O with a reversible capacity of 759 mA h g−1 are selected respectively as the optimal positive and negative electrodes to construct a full cell. Such an electrode match-up, i.e. Li-rich/Mn0.8Co0.2O full cell (“N-cell”), allows no need for pre-activation of the metal oxide anode. This “N-cell” can deliver a high reversible capacity of 205 mA h g−1 and particularly rather high volumetric energy density, which is about 31% higher than that of a Li-rich/graphite full cell (“T-cell”). The special coulombic efficiency match-up and tailored microstructures and compositions of the electrode materials are all crucial to achieve such a high energy density.
Co-reporter:Xin Sun, Xiao-Yang Ji, Yu-Ting Zhou, Yu Shao, Yong Zang, Zhao-Yin Wen, Chun-Hua Chen
Journal of Power Sources 2016 Volume 314() pp:35-38
Publication Date(Web):15 May 2016
DOI:10.1016/j.jpowsour.2016.03.011
•A cyanoferrate Ti0.75Fe0.25[Fe(CN)6]0.96·1.9H2O can be used as a new anode material.•The cynaoferrate reacts with lithium following a conversion reaction mechanism.•The cynnoferrate can store much more lithium than sodium.A novel air-stable titanium hexacyanoferrate (Ti0.75Fe0.25[Fe(CN)6]0.96·1.9H2O) with a cubic structure is synthesized simply by a solution precipitation method, which is first demonstrated to be a scalable, low-cost anode material for lithium-ion batteries exhibiting high capacity, long cycle life and good rate capability. Nevertheless, it has a low capacity of about 100 mAh g−1 as an anode material for sodium-ion batteries.
Co-reporter:Ran Yu, Qing-Xia Du, Bang-Kun Zou, Zhao-Yin Wen, Chun-Hua Chen
Journal of Power Sources 2016 Volume 306() pp:623-629
Publication Date(Web):29 February 2016
DOI:10.1016/j.jpowsour.2015.12.065
•The optimal composition is Li3/8Sr7/16Zr1/4Nb3/4O3.•Dense LSZN pellets can be prepared at a temperature below 1200 °C.•A dual dopants involved defect reaction is proposed.Stable solid electrolytes with high lithium ionic conductivity are crucial for all-solid-state lithium ion batteries. The compatibility with electrodes require a sintering temperature around 1000 °C. A perovskite-type (Li,Sr)(Zr,Nb)O3 system with A-site vacancy is designed and synthesized by a solid-state reaction route. Four compositions with different concentrations of A-site vacancy and several sintering temperatures between 1100 and 1300 °C are selected to find an optimal composition. X-ray diffraction and scanning electron microscope are employed to analyze the crystalline phases and the microstructure of the sintered samples. The ionic conductivities of the materials are measured by AC impedance spectroscopy. For the sample with the optimal composition Li3/8Sr7/16Zr1/4Nb3/4O3 and sintered at 1200 °C, its total ionic conductivity is 2.00×10−5 and 1.65×10−4 Scm−1 at 30 and 100 °C, respectively. Its activation energy for lithium ion conduction is 0.26 eV.
Co-reporter:Xin Sun, Xiao-Yang Ji, Hao-Yang Xu, Chen-Yu Zhang, Yu Shao, Yong Zang, Chun-Hua Chen
Electrochimica Acta 2016 Volume 208() pp:142-147
Publication Date(Web):1 August 2016
DOI:10.1016/j.electacta.2016.04.067
•Different cooling procedures lead to different phase compositions.•Mixed P2-O3 Na0.67[Ni0.4Co0.2Mn0.4]O2 shows excellent electrochemical properties.•Initial coulombic efficiency is below 100% despite of its Na-deficient composition.Layered-structured ternary oxide Na0.67[Ni0.4Co0.2Mn0.4]O2 is synthesized as cathode material for sodium-ion batteries. Using a liquid nitrogen quenching process during the synthesis procedure, a Na0.67[Ni0.4Co0.2Mn0.4]O2 powder with a mixed P2-O3 structure is obtained, and then characterized. The Na//Na0.67[Ni0.4Co0.2Mn0.4]O2 cell delivers a reversible capacity of 167 mA h g−1 and exhibits excellent cycling and rate performances without abnormal initial coulombic efficiency.
Co-reporter:Yu-Ting Zhou, Xin Sun, Bang-Kun Zou, Jia-Yin Liao, Zhao-Yin Wen, Chun-Hua Chen
Electrochimica Acta 2016 Volume 213() pp:496-503
Publication Date(Web):20 September 2016
DOI:10.1016/j.electacta.2016.07.089
Na0.44Mn1-xCoxO2 (x = 0, 0.01, 0.08, 0.11, 0.22, 0.33, 0.44) powders are synthesized as positive electrodes for sodium-ion batteries via a thermopolymerization method. X-ray diffraction and scanning electron microscopy are used to analyze their crystal structures and particle morphologies. Galvanostatic cell cycling is used to characterize the electrochemical properties. The Co-substitution can change the structure of Na0.44Mn1-xCoxO2 from T-type (x = 0) into layered P2-type (x = 0.11) or P3-type (x = 0.44). For the samples synthesized under our specific conditions, the particle morphology can be used as an indicator of their crystal structures: rod-like (T-type), plate-like (P2-type) and granules (P3-type). P2-type Na0.44Mn0.89Co0.11O2 allows more Na+ intercalation into the inter-layer spacing and results in a high discharge capacity with 220 mAh g−1 at 12 mA g−1 in initial cycle, 180 mAh g−1 after 40 cycles in the voltage range of 2.0-4.2 V and a good rate performance of 104 mAh g−1 at a rate of 600 mA g−1 in the voltage range of 2.0-4.0 V.
Co-reporter:Bang-Kun Zou, He-Yang Wang, Zi-Yue Qiang, Yu Shao, Xin Sun, Zhao-Yin Wen, Chun-Hua Chen
Electrochimica Acta 2016 Volume 196() pp:377-385
Publication Date(Web):1 April 2016
DOI:10.1016/j.electacta.2016.03.017
•Ascorbic acid acts as both an antioxidant and a first-time carbon coating source.•Reaction mechanisms of the synthesis are carefully studied.•Mixed-carbon-coated LiMn0.4Fe0.6PO4 nanopowders process excellent high rate and low temperature performances.A novel solvothermal approach with ascorbic acid as both an antioxidant and a first-time carbon coating source is developed to synthesize LiMn0.4Fe0.6PO4 nano-particles with a uniform particle size distribution around 150 nm. A calcination step for the second-time carbon coating and further crystallization is adopted following the solvothermal step. The structures and electrochemical properties of the obtained samples are studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transformation infrared, Infrared carbon-sulfur analyzer and galvanostatic cell cycling. Ascorbic acid plays a crucial role in the formation of uniform carbon layer and nano-particles. Compared with single-carbon-coated LiMn0.4Fe0.6PO4 without adding ascorbic acid, the mixed-carbon-coated LiMn0.4Fe0.6PO4 shows much better electrochemical performance. It can deliver specific capacities of 154.8 and 128.5 mAh g−1 at 1C and 20C, respectively, at 25 °C. Even at −20 °C, its specific capacities are 106.6 and 68.8 mAh g−1 at 0.2C and 5C, respectively.Ascorbic acid acts as both an antioxidant and a surfactant to form organic groups (first carbon source) on the surface of as-solvothermal products, in which the OH (or H2O) groups of glucose (second carbon source) are closely bonded to the surface to form a uniform adsorption layer. Uniform mixed-carbon-coated LiMn0.4Fe0.6PO4 nanopowders are formed after calcination, which demonstrate excellent electrochemical performances.
Co-reporter:Bangkun Zou, Ran Yu, Miaomiao Deng, Yuting Zhou, Jiaying Liao and Chunhua Chen
RSC Advances 2016 vol. 6(Issue 57) pp:52271-52278
Publication Date(Web):24 May 2016
DOI:10.1039/C6RA12472K
Mixed-carbon coated LiMn1−xFexPO4 (x = 0, 0.2, 0.5, 1) nano-particles are synthesized by a novel solvothermal approach. All of these powders possess a uniform particle size distribution around 150 nm and a carbon coating layer of about 2 nm. The LiMn1−xFexPO4@C samples with a carbon content of 2 wt% have an optimal electrochemical performance. The average voltage platform of LiMn1−xFexPO4@C increases with the increased Mn/Fe ratio, but declines gradually during electrochemical cycling. The LiMn0.5Fe0.5PO4 sample shows a high energy density (568 W h kg−1), good cycleability (97.1%, 100 cycles) and excellent rate capability (120.2 mA h g−1, 20C) at room temperature. Simultaneously, the LiMn0.5Fe0.5PO4 and LiFePO4 samples also show excellent low temperature electrochemical performance with specific capacities of 109.4 and 138.8 mA h g−1 with average discharge voltages of 3.476 V and 3.385 V, respectively, at −12 °C. Even at −20 °C, their discharge specific capacities are 71.7 and 82.3 mA h g−1 at 3C, respectively.
Co-reporter:Yong Zang, Xin Sun, Zhong-Feng Tang, Hong-Fa Xiang and Chun-Hua Chen
RSC Advances 2016 vol. 6(Issue 36) pp:30194-30198
Publication Date(Web):16 Mar 2016
DOI:10.1039/C6RA02472F
Fine powders of Li1.2Ni0.2Mn0.6−xVxO2 (x = 0, 0.002, 0.005, 0.01, 0.02) are prepared by a thermopolymerization method. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements are carried out to characterize these samples. The V-doped samples show great improvement in rate performance and cycling stability, as well as mitigation of voltage decline during cycling. For the optimal composition Li1.2Ni0.2Mn0.59V0.01O2, it exhibits a discharge capacity of 245 and 118 mA h g−1 at 0.1C and 10C rates, respectively. It retains a capacity of 234 mA h g−1 at 0.1C after 188 cycles with a capacity retention of 95.5%. This study suggests that the partial substitution of Mn4+ with V5+ can improve both the rate capability and cycle stability of this high-capacity cathode material.
Co-reporter:He-Yang Wang, Bang-Kun Zou, Zhong-Feng Tang, Zhao-Yin Wen, Chun-Hua Chen
Materials Letters 2016 Volume 177() pp:54-57
Publication Date(Web):15 August 2016
DOI:10.1016/j.matlet.2016.04.162
•Li2MoO4 is successfully prepared by a thermal polymerization method.•Polyvinyl alcohol is a good carbon source for particle coating.•Carbon coating improves cycle and rate performances of Li2MoO4.High capacity anode material Li2MoO4 powders with and without carbon coating are successfully synthesized via a thermal polymerization method. X-ray diffraction, scanning electron microscopy and transmission electron microscopy are employed to analyze their structures. Galvanostatic cell cycling is used to compare their electrochemical properties. The carbon-coated Li2MoO4 can deliver charge capacities of 669 mAh g−1 and 255 mAh g−1 at current densities of 90 mA g−1 and 1800 mA g−1, respectively, exhibiting much better electrochemical performance than the carbon-free Li2MoO4.
Co-reporter:Yong Zang, Chu-Xiong Ding, Xiao-Cheng Wang, Zhao-Yin Wen, Chun-Hua Chen
Electrochimica Acta 2015 Volume 168() pp:234-239
Publication Date(Web):20 June 2015
DOI:10.1016/j.electacta.2015.03.223
Fine powders of Li1.2Ni0.2Mn0.6−xMoxO2 (x = 0, 0.002, 0.005, 0.01, 0.05) are prepared by a thermopolymerization method. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements are carried out to characterize these samples. The maximum Mo-doping level to obtain a pure layered phase is 0.005. The Mo-doped samples show a great improvement in rate performance and cycling stability. For the optimal composition Li1.2Ni0.2Mn0.59Mo0.01O2, it exhibits a discharge capacity of 245 and 110 mA h g−1 at 0.1 C and 5 C, respectively. It retains a capacity of 229 mA h g−1 at 0.1 C after 204 cycles with a capacity retention of 93.2%. This study suggests that the partial substitution of Mn4+ with Mo6+ can improve both the rate capability and cycle performance of this high-capacity cathode material.
Co-reporter:Xiao-Hang Ma, Shuang-Shuang Zeng, Bang-Kun Zou, Xin Liang, Jia-Ying Liao and Chun-Hua Chen
RSC Advances 2015 vol. 5(Issue 71) pp:57300-57308
Publication Date(Web):23 Jun 2015
DOI:10.1039/C5RA10825J
CuO powders composed of different rod-like clusters or dandelion-like nanospheres are prepared by a low-temperature thermal decomposition process of Cu(OH)2 precursors, which are obtained via a catalytic template method. A tentative mechanism is proposed to explain the formation and transformation of different Cu(OH)2 nanostructures. X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, field-emission scanning electron microscopy, transmission electron microscopy, infrared spectra analysis, Brunauer–Emmett–Teller measurements, and galvanostatic cell cycling are employed to characterize the structures and electrochemical performance of these CuO samples. The results show that these CuO samples obtained after 500 °C calcination have a stable cycling performance with a reversible capacity of over 587 mA h g−1 after 50 cycles. The dandelion-like CuO electrode shows the best rate performance with a high capacity of 511 mA h g−1 at 4C.
Co-reporter:Qing-Xia Du, Zhong-Feng Tang, Xiao-Hang Ma, Yong Zang, Xin Sun, Yu Shao, Zhao-Yin Wen, Chun-Hua Chen
Solid State Ionics 2015 Volume 279() pp:11-17
Publication Date(Web):15 October 2015
DOI:10.1016/j.ssi.2015.07.006
•Pure phase LiNi0.5Co0.2Mn0.3 −xZrxO2 powders are synthesized when x ≤ 0.02.•Sintering in oxygen can decrease the degree of cationic mixing.•Optimized LiNi0.5Co0.2Mn0.29Zr0.01O2 electrode exhibits high capacity retention and a high rate capability.The powders of layered structured LiNi0.5Co0.2Mn0.3O2 cathode material are synthesized by a thermal polymerization method in the temperatures range from 750 °C to 950 °C in air and oxygen. It is found that the LiNi0.5Co0.2Mn0.3O2 powder sintered in oxygen has significantly decreased degree of cationic mixing. The discharge capacities of the samples sintered in oxygen are higher than those of the samples sintered in air. The sample sintered at 900 °C in oxygen has the highest ratio of I003/I104 and the highest initial discharge capacities of 200 mAh g− 1 at a rate of 0.1C in the voltage range of 2.8–4.5 V. In order to improve the cycling stability of the LiNi0.5Co0.2Mn0.3O2 electrode, a series of Zr-doped LiNi0.5Co0.2Mn0.3O2 electrodes (LiNi0.5Co0.2Mn0.3 −xZrxO2, x = 0.01, 0.02, 0.03, 0.04, 0.05) are also prepared. The LiNi0.5Co0.2Mn0.3 −xZrxO2 electrodes show much enhanced cycling performance compared to the un-doped LiNi0.5Co0.2Mn0.3O2 electrode. The LiNi0.5Co0.2Mn0.29Zr0.01O2 electrode exhibits the best electrochemical performance with the capacity retention of 93.92% after 100 cycles at 0.2C in the voltage range of 2.8–4.5 V, while the un-doped LiNi0.5Co0.2Mn0.3O2 electrode exhibits capacity retention of only 83.33% after 100 cycles. The LiNi0.5Co0.2Mn0.29Zr0.01O2 electrode also shows obvious improved rate capability relative to that of the un-doped electrode.
Co-reporter:Xin Sun, Yi Jin, Chen-Yu Zhang, Jian-Wu Wen, Yu Shao, Yong Zang and Chun-Hua Chen
Journal of Materials Chemistry A 2014 vol. 2(Issue 41) pp:17268-17271
Publication Date(Web):26 Aug 2014
DOI:10.1039/C4TA03828B
New electrode materials of layered oxides, Na[Ni0.4Fe0.2Mn0.4−xTix]O2, have been synthesized as positive electrodes for sodium-ion batteries. The partial substitution of Mn with Ti increases the lattice spacing without changing the lattice structure. A Na//Na[Ni0.4Fe0.2Mn0.2Ti0.2]O2 cell delivers a reversible capacity of 145 mA h g−1 with excellent long cycling performance.
Co-reporter:Bin Cheng, Xu-Dong Zhang, Xiao-Hang Ma, Jian-Wu Wen, Yan Yu, Chun-Hua Chen
Journal of Power Sources 2014 Volume 265() pp:104-109
Publication Date(Web):1 November 2014
DOI:10.1016/j.jpowsour.2014.04.046
•Nano-Li3V2(PO4)3 enwrapped into rGO sheets is synthesized.•Liquid nitrogen was used as a coolant in the freeze-drying method.•The material shows excellent rate performance in lithium ion batteries.Liquid nitrogen was used as a coolant in the freeze-drying method to synthesize nano-Li3V2(PO4)3/reduced graphene oxide (LVPGN) for the first time. In this material, reduced graphene oxide (rGO) (6.6 wt% in content) formed a 3D-framework and Li3V2(PO4)3 nanoparticles (30–150 nm) were strongly adhered to the surface of the rGO and enwrapped into the rGO sheets uniformly. The LVP nanoparticles can decrease the lithium ion diffusion length and the rGO can effectively improve the electronic conductivity. The material shows great rate performance with a capacity of 105.7 mAh g−1 at 20C for 3.0–4.3 V, and a good cycling performance with a discharge capacity of 123.2 mAh g−1 (96.7% of the first discharge capacity 127.4 mAh g−1) after 100 cycles at 0.1C.
Co-reporter:Jian-Wu Wen, Da-Wei Zhang, Chun-Hua Chen, Chu-Xiong Ding, Yan Yu, Joachim Maier
Journal of Power Sources 2014 Volume 264() pp:155-160
Publication Date(Web):15 October 2014
DOI:10.1016/j.jpowsour.2014.04.077
•A novel safety strategy to avoid overcharging, i.e. solid-state anti-overcharge additive, is proposed.•The strategy can provide a high-potential and a long-period of anti-overcharge performance.•The effectiveness of the solid-state anti-overcharge additives is confirmed in LiCoO2/C and LiMn2O4/C full cells.Overcharge safety is the most crucial problem facing especially large-sized lithium-ion batteries (LIBs) packs owing to the inevitable inhomogeneity of charge-state for each cell. We propose a fresh safety strategy to avoid overcharging, i.e. the use of a solid-state anti-overcharge additive to perform an intrinsic overcharge protection. The mechanism is triggered from a solid-state composite cathode obtained by typically mixing a pre-selected transition-metal oxide with a certain cathodes thus constituting a composite cathode. The effectiveness of this strategy is demonstrated with an example of LiCoO2/CuO (95:5 by weight) composite, which exhibits high-potential (up to 5 V vs. Li+/Li) and long-period (month-level) anti-overcharge performance. It is found that the additive does not hurt the electrochemical cycling performance under normal operational conditions. This novel safety strategy is simple and flexible, which may open a new window to develop safer LIBs systems.
Co-reporter:Bang-Kun Zou, Xiao-Hang Ma, Zhong-Feng Tang, Chu-Xiong Ding, Zhao-Yin Wen, Chun-Hua Chen
Journal of Power Sources 2014 Volume 268() pp:491-497
Publication Date(Web):5 December 2014
DOI:10.1016/j.jpowsour.2014.06.085
•A nanoplate-assembled MnO2 with a high surface area is synthesized.•The two-step hydrothermally synthesized LiMn2O4/carbon nanotube composite keeps the particle size of MnO2 precursor.•LiMn2O4/carbon nanotube composite shows a high rate capability and reversible cycling performance.A two-step hydrothermal approach is employed to synthesize LiMn2O4/carbon nanotube (LMO/CNT) composite powders. X-ray diffraction, scanning electron microscopy, thermal gravimetry and N2-adsorption/desorption are used to characterize their structures and compositions. Galvanostatic cycling in coin-cells is adopted to measure their electrochemical properties as cathode materials of lithium-ion batteries. A LiMn2O4 pure phase of high crystallinity is observed with CNT homogeneously dispersed in the composite network. The electrochemical properties of them are associated with two factors, i.e. the content of CNT in the hydrothermal process and the annealing temperature at the subsequent heat treatment step. Excellent rate capability of these LMO/CNT electrodes can be achieved.
Co-reporter:Yu Qiao, Yan Yu, Yi Jin, Yi-Biao Guan, Chun-Hua Chen
Electrochimica Acta 2014 Volume 132() pp:323-331
Publication Date(Web):20 June 2014
DOI:10.1016/j.electacta.2014.03.177
•Double-shelled Mn2O3 hollow microspheres are prepared by a multi-step.•synthesis procedure.•Solid, hollow and yolk-structured Mn2O3 spheres are prepared for comparison.•The double-shelled hollow Mn2O3 is superior in electrochemical properties.By means of a specially designed multi-step synthesis procedure involving steps of precipitation, controlled oxidation, selective etching and calcination, porous double-shelled Mn2O3 hollow microspheres are synthesized. Solid, hollow and yolk-structured Mn2O3 are also similarly synthesized for comparison. X-ray diffraction, scanning and transmission electron microscopies, IR spectroscopy, thermogravimetry, and Brunauer-Emmett-Teller measurements are employed to investigate their structures and compositions. Galvanostatic cell cycling and impedance spectroscopy are used to characterize the electrochemical properties of Mn2O3/Li cells. The results show that the hierarchical hollow structured (double-shelled, hollow and yolk-structured) Mn2O3 anode materials deliver higher reversible capacities and excellent cycling stabilities than the solid Mn2O3. Moreover, among the three hierarchical hollow structured samples, the double shelled sample possesses the best cycling performance, especially at a high current density.
Co-reporter:Xiao-Hang Ma, Qing-Yun Wan, Xiao Huang, Chu-Xiong Ding, Yi Jin, Yi-Biao Guan, Chun-Hua Chen
Electrochimica Acta 2014 Volume 121() pp:15-20
Publication Date(Web):1 March 2014
DOI:10.1016/j.electacta.2013.12.004
•An improved electrostatic spray deposition technique to prepare easily-oxidized electrode materials is developed.•3-D porous MnO thin films are prepared as anode materials for lithium-ion batteries.•The MnO thin-film electrode on nickel foam substrate shows optimal electrochemical properties.The three-dimensionally porous MnO thin-film electrodes supported on nickel foam and stainless steel substrates were prepared by the improved electrostatic spray deposition (ESD) technique. X-ray diffraction, scanning electron microscopy, and galvanostatic cell cycing are employed to characterize the structures and electrochemical performance of the MnO thin-film electrodes. The results show that these as-prepared MnO thin-film electrodes have a special three dimensional porous network structure and also have stable cycling performance with a reversible capacity of over 850 mAh g−1 after 50 cycles at a current density of 80 mA g−1. The MnO thin-film deposited on the nickel foam shows the highest initial columbic efficiency (83.9%), the lowest initial capacity loss (14.2%), and the best rate performance with a high capacity of 498.4 mAh g−1 at a current density of 1200 mA g−1. The experimental results suggest that such the MnO thin-film with a special structure is a promising anode material for lithium-ion batteries.
Co-reporter:Jian-Wu Wen, Da-Wei Zhang, Yong Zang, Xin Sun, Bin Cheng, Chu-Xiong Ding, Yan Yu, Chun-Hua Chen
Electrochimica Acta 2014 Volume 132() pp:193-199
Publication Date(Web):20 June 2014
DOI:10.1016/j.electacta.2014.03.139
•A unique bowl-like hollow spherical Co3O4 structure is prepared through a simple, low-cost and mass-yield method.•Such a bowl-like hollow Co3O4 microsphere demonstrates extraordinary rate and cycling performance for Li-storage.•The sodium-storage behavior of Co3O4 is investigated for the first time.Bowl-like hollow Co3O4 microspheres are prepared via a simple and low-cost route by thermally treating Co-containing resorcinol-formaldehyde composites gel in air. Scanning electron microscopy, transmission electron microscope and N2 adsorption-desorption measurements demonstrate that these bowl-like hollow Co3O4 microspheres are composed of hollow inner cavities and outer shell walls (70 nm thickness), on which a considerable amount of mesopores centered around 5-17 nm size are distributed. When employed as the anode material for lithium-ion batteries, these bowl-like hollow Co3O4 microspheres exhibit extraordinary cycling performance (111% retention after 50 cycles owing to capacity rise), fairly high rate capacity (650 mAh g−1 at 5 C) and enhanced lithium storage capacity. Meanwhile, the Na-storage behavior of Co3O4 as an anode material of Na-ion batteries is initially investigated based on such a hollow structure and it exhibits similar feature of discharge/charge profiles and a high initial discharge capacity but relatively moderate capacity retention compared with the Li-storage performance.
Co-reporter:Jian-Wu Wen, Da-Wei Zhang, Yong Zang, Xin Sun, Bin Cheng, Chu-Xiong Ding, Yan Yu, Chun-Hua Chen
Electrochimica Acta 2014 Volume 133() pp:515-521
Publication Date(Web):1 July 2014
DOI:10.1016/j.electacta.2014.04.018
•A one-step sol-gel route with resorcinol-formaldehyde resin is designed to synthesis LiNi0.5Mn1.5O4.•Fd-3 m phase delivers an excellent high rate performance and stable cycling retention.•A double “w”-shape R-V curve is a potential tool to indicate structure transition.Spinel LiNi0.5Mn1.5O4 (Fd-3 m) powders are synthesized by a facile one-step sol-gel approach with a resorcinol formaldehyde (RF) resin as a chelating agent. The cross-linked metal-containing RF xerogel particles are sintered at different high temperatures from 750 to 950 °C to produce several micron-sized LiNi0.5Mn1.5O4 powders. Electrochemical measurements suggest that the 850 °C-sintered (in air) sample (Fd-3 m phase) performs the best with a discharge capacity of 141 mAh g−1 at 0.1 C and 110 mAh g−1 at 10 C, and capacity-retention of 96.3% after 60 cycles at 0.25 C and 89% after 200 cycles at 1 C. For comparison, the LiNi0.5Mn1.5O4 sample sintered at 850 °C in O2 (P4332 phase) presents limited rate performance (45 mAh g−1 at 10 C) and higher values in both AC impedance and DC-method derived resistance. A characteristic double “w”-shape curve of DC resistance against cell potential can be possibly considered as an indicator to probe the material structure transition during the charge/discharge process of the cell.
Co-reporter:Xuyong Feng, Ning Ding, Yingchao Dong, Chunhua Chen and Zhaolin Liu
Journal of Materials Chemistry A 2013 vol. 1(Issue 48) pp:15310-15315
Publication Date(Web):21 Oct 2013
DOI:10.1039/C3TA13676K
A simple surface modification of Li4Ti5O12 powder is made with an aqueous CrO3 solution to improve its electrochemical properties. At a high current rate of 30 C, the specific capacity of the Li4Ti5O12 increases by about 60% from its original 80 to 130 mA h g−1. After the modification with the CrO3 solution, a few surface phases including lithium chromate (Li2CrO4), Cr2O5 and anatase are found to co-exist in the final product. Among these three phases, Li2CrO4 and Cr2O5 can improve while anatase deteriorates the rate performance of Li4Ti5O12. The AC impedance spectra and electron spin resonance (ESR) spectra reveal that the improvement of rate performance is correlated with the presence of Ti3+, which can increase the conductivity of the Li4Ti5O12 sample. Lithium chromate (Li2CrO4) and Cr2O5 react with lithium to form lithium rich phases (Li3+xCrO4 and LiyCr2O5) of low potential, which stabilize Li7Ti5O12 with high electric conductivity and result in better rate performance. Besides improved rate performance, the cycle performance of the modified Li4Ti5O12 samples is almost at the same level with the original Li4Ti5O12, suggesting that this proposed modification method is efficient and harmless.
Co-reporter:Yu Qiao, Si-Rong Li, Yan Yu and Chun-Hua Chen
Journal of Materials Chemistry A 2013 vol. 1(Issue 3) pp:860-867
Publication Date(Web):25 Oct 2012
DOI:10.1039/C2TA00204C
Yolk-structured microspheres of spinel LiMn2O4 are successfully prepared by a specially designed multi-step synthesis procedure involving precipitation, controlled oxidation, selective etching and chemical lithiation. Solid-structured and hollow-structured LiMn2O4 are also synthesized by a similar method for comparison. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller method and IR spectroscopy are employed to study their structures and compositions. The electrochemical properties of the LiMn2O4/Li cells are also tested. The results indicate that LiMn2O4 powder composed of yolk-structured microspheres possesses remarkable high rate capability and outstanding high capacity retention not only at room temperature but also at elevated temperatures. This study may provide significant new insight into restraining the capacity fading of LiMn2O4 electrodes and the yolk-structured LiMn2O4 may be used for the next generation of lithium ion batteries.
Co-reporter:Yi Sun, Linchao Zhang, Suqing Wang, Ingo Lieberwirth, Yan Yu, ChunHua Chen
Journal of Power Sources 2013 Volume 228() pp:7-13
Publication Date(Web):15 April 2013
DOI:10.1016/j.jpowsour.2012.11.095
Vanadium oxide films composed of porous walnut-like particles are fabricated by electrostatic spray deposition (ESD) with an oil-bathed suspension precursor. The micron-sized particles are constructed from vanadium oxide nanocrystals of size around 50–100 nm and the valence of vanadium is determined by electron energy loss spectroscopy (EELS). As a cathode material for rechargeable lithium batteries, it exhibits stable reversible specific capacity and ultra-high rate capability. It delivers a specific discharge capacity of 254 mAh g−1 in first cycle, and still maintains 200 mAh g−1 after 100 cycles in the voltage range of 2.1–4.0 V. When the cell is cycled between 2.5 and 4.0 V, its discharge capacity reaches 103 mAh g−1 at 50 C and reserves 85 mAh g−1 at 10 C even at −10 °C.Highlights► Fabrication of a nanoporous vanadium oxide film by using a suspension instead of usual solution as ESD precursor. ► The use electron energy loss spectrum (EELS) technique to determine vanadium valence in the nanocomposite film. ► Vanadium oxide film shows excellent electrochemical properties.
Co-reporter:Yi Sun, Shu-Bin Yang, Li-Ping Lv, Ingo Lieberwirth, Lin-Chao Zhang, Chu-Xiong Ding, Chun-Hua Chen
Journal of Power Sources 2013 Volume 241() pp:168-172
Publication Date(Web):1 November 2013
DOI:10.1016/j.jpowsour.2013.04.093
•RGO modified hydrated vanadium pentoxide nanoribbons are obtained by a facile hydrothermal process.•A free-standing VO2.07/RGO film is fabricated with these ribbons.•The binder-free free-standing VO2.07/RGO film electrode shows good electrochemical properties.Hydrated vanadium pentoxide (V2O5·0.86H2O) nanoribbons modified with reduced graphene oxide (RGO) are synthesized by a hydrothermal process. These ribbons are 30 nm thick, 200 nm to 1 μm wide and above 50 μm long. Binder-free films are prepared by using these ribbons and annealed at 300 °C in nitrogen as the cathode for rechargeable lithium cells. The intertwining network of this free-standing VOx/RGO film provides efficient conduction pathways for electrons and short diffusion distances for Li ions. The electrochemical tests exhibit that this cathode film delivers a high reversible specific capacity (160 mAh g−1) and good cycling stability (133 mAh g−1 after 200 cycles) in the voltage range between 2.0 and 3.5 V.
Co-reporter:Xu-Yong Feng, Ning Ding, Li Wang, Xiao-Hang Ma, Yong-Ming Li, Chun-Hua Chen
Journal of Power Sources 2013 Volume 222() pp:184-187
Publication Date(Web):15 January 2013
DOI:10.1016/j.jpowsour.2012.08.061
Co-reporter:Xiao-Hang Ma, Xu-Yong Feng, Chao Song, Bang-Kun Zou, Chu-Xiong Ding, Yan Yu, Chun-Hua Chen
Electrochimica Acta 2013 Volume 93() pp:131-136
Publication Date(Web):30 March 2013
DOI:10.1016/j.electacta.2013.01.096
The α-Fe2O3 powders composed of different flower-like or yarn-like clusters are prepared by a thermal decomposition process of iron alkoxide precursors, which are obtained via a simple reaction between iron acetylacetonate and ethylene glycol in an oil bath. X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, Brunauer–Emmett–Teller measurement, and galvanostatic cell cycling are employed to characterize the structures and electrochemical performance of these α-Fe2O3 samples. The results show that these α-Fe2O3 electrodes have stable cycling performance with a reversible capacity of over 800 mAh g−1 after 40 cycles. The sample with optimized structure shows the best rate performance with a high capacity of 622 mAh g−1 at the current density of 4687 mA g−1. The experimental results suggest that such an α-Fe2O3 powder is a promising anode material for high energy-density lithium-ion batteries.Highlights► The oil-bath process is simple and easy to control the structure of products. ► Ferric acetylacetonate is a good precursor for open-structured Fe2O3 clusters. ► The optimized flow-like Fe2O3 clusters exhibit excellent electrochemical properties.
Co-reporter:Lin Wang, Lin-Chao Zhang, Jian-Xiu Cheng, Chu-Xiong Ding, Chun-Hua Chen
Electrochimica Acta 2013 Volume 102() pp:306-311
Publication Date(Web):15 July 2013
DOI:10.1016/j.electacta.2013.04.035
Co-reporter:L.C. Zhang, C.L. Yang, Y.F. Jiang, F. Teng, C.X. Ding, Y. Yu, Z.Y. Wen, C.H. Chen
Electrochimica Acta 2013 Volume 114() pp:347-351
Publication Date(Web):30 December 2013
DOI:10.1016/j.electacta.2013.10.016
A novel and simple in-situ solid-state reaction route is developed to synthesize a three-dimensional (3D) porous carbon fiber film-supported Li3V2(PO4)3 membrane electrode. The carbon film is obtained via the carbonization of a bioproduct rice paper (RP). The carbon film can function as both a current collector and a 3D electronic conduction network for the loaded Li3V2(PO4)3 particles. The structure and electrochemical properties of the Li3V2(PO4)3 membrane electrode are characterized. As a free-standing membrane electrode, it exhibits good rate performance at room temperature with a specific capacity of 108 and 142 mAh g−1 at 10 C rate in the voltage range of 3.0–4.3 V and 3.0–4.8 V, respectively. It also shows good cycling performance with a specific capacity of 123 mAh g−1 after 500 cycles at 1 C rate in the voltage range of 3.0–4.8 V.Schematic illustration of the synthesis process of free-standing LVP@C laminates.
Co-reporter:Fei Teng, Zhi-Hao Hu, Xiao-Hang Ma, Lin-Chao Zhang, Chu-Xiong Ding, Yan Yu, Chun-Hua Chen
Electrochimica Acta 2013 Volume 91() pp:43-49
Publication Date(Web):28 February 2013
DOI:10.1016/j.electacta.2012.12.090
A plate-like carbon-coated Li3V2(PO4)3 (LVP/C) powder composed of nanoplates was synthesized by a hydrothermal route. The structure and electrochemical properties of the LVP/C are characterized by X-ray diffraction, scanning and transmission electron microscopy, and galvanostatic charge–discharge cycling. This LVP/C electrode exhibits good rate performance at room temperature with a specific capacity of 113.8 and 128.8 mAh g−1 at 6 C rate in the voltage range of 3.0–4.3 V and 3.0–4.8 V, respectively. The sample also shows good cycling performance with 91.4% and 85% of capacity retention after 200 cycles at 1 C rate. Even at −20 °C, the plate-like LVP/C delivers a stable cycling performance with a specific capacity of 120.7 mAh g−1, being 95.3% of the capacity at room temperature, and after 80 cycles, the capacity retention is 97.2%.Highlights► Plate-like carbon-coated LVP particles are synthesized by a hydrothermal method. ► High performances of this LVP/C in both 3.0–4.3 V and 3.0–4.8 V are achieved. ► The discharge capacity at even −20 °C is very close (95.3%) to that at 25 °C.
Co-reporter:L.C. Zhang, Z. Hu, L. Wang, F. Teng, Y. Yu, C.H. Chen
Electrochimica Acta 2013 Volume 89() pp:310-316
Publication Date(Web):1 February 2013
DOI:10.1016/j.electacta.2012.11.042
Rice paper (RP) is thermally carbonized in nitrogen to prepare three-dimensionally porous carbon films, which are used for the first time as both a free-standing active anode material and a current collector of a cathode (LiFePO4 here) for lithium-ion batteries. The latter is fabricated through a one-step co-sintering of a Li–Fe–P–O precursor top layer supported on the rice paper. The rate and cycling performances of both these electrodes are found to be rather good or even better than the traditional electrodes due to the three-dimensionally porous structure of the RP-derived carbon. We also design and fabricate an RP-based full cell constructed with the above mentioned anode and cathode together with an RP membrane as the separator. Without using traditional metallic current collectors and separator membranes, such a cell exhibits reversible cycling performance.Highlights► Carbonization of a rice paper (RP) results in a highly porous free-standing hard carbon film composed of carbon fibers. ► Free-standing LiFePO4@C laminate is prepared through a one-step co-sintering process. ► A RP-based full cell with reversible cycling characteristic is fabricated.
Co-reporter:Xuyong Feng, Chen Shen, Ning Ding and Chunhua Chen
Journal of Materials Chemistry A 2012 vol. 22(Issue 39) pp:20861-20865
Publication Date(Web):20 Aug 2012
DOI:10.1039/C2JM32673F
Lithium chromium titanium oxide (LiCrTiO4) spinel powders are synthesized by an acrylic acid polymerization method. The lithium intercalation capacity of the LiCrTiO4 sample synthesized in air is about 150 mA h g−1, which is very close to its theoretical capacity (157 mA h g−1). In addition to its very good cycle performance similar to that of Li4Ti5O12, the LiCrTiO4 shows excellent rate performance with no obvious capacity loss at the current density from 1C to 10C rates. By means of Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy, the LiCrTiO4 sample synthesized in air is found to contain a small amount of lithium chromium oxide (LiCrxOy, y > 1/2 + 3x/2) as an in situ produced modifier that can improve the conductivity of the electrode.
Co-reporter:G.B. Zhong, Y.Y. Wang, X.J. Zhao, Q.S. Wang, Y. Yu, C.H. Chen
Journal of Power Sources 2012 Volume 216() pp:368-375
Publication Date(Web):15 October 2012
DOI:10.1016/j.jpowsour.2012.05.108
A series of Al-substituted spinel powders LiNi0.5−xAl2xMn1.5−xO4 (0 ≤ 2x ≤ 1.0) have been prepared and the effects of Al concentration on the structural, electrochemical and thermal properties are investigated. The XRD patterns show that impurity arises when 2x ≥ 0.6. The FTIR and Raman spectra indicate that the introduction of Al in the LiNi0.5Mn1.5O4 increases the disordering degree of Ni/Mn ions, changing the spinel structure from P4332 to Fd3¯m. Cyclic voltammetry tests show that the voltage step between Ni2+/Ni3+ and Ni3+/Ni4+ have a sudden leap at 2x = 0.075, responding to the structural difference of the spinels. The Al concentration is optimized in the range of 0.05 ≤ 2x ≤ 0.1, in which the cyclic stability and rate capability of the LiNi0.5−xAl2xMn1.5−xO4 spinels are significantly improved. At room temperature the LiNi0.45Al0.10Mn1.45O4 presents the best cycle performance with the capacity retention of 95.4% after 500 cycles at 1C rate, and the best rate capability with the discharge capacity of 119 mAh g−1 at 10C rate, which is about 93.7% of its capacity at 0.5C. The thermal properties of the spinels have been tested by C80 calorimeter and the results show that introduction of Al in LiNi0.5Mn1.5O4 can effectively suppress the exothermic reaction below 225 °C, thus improve the safety of the high voltage cathode material.Highlights► Al-doped compounds LiNi0.5−xAl2xMn1.5−xO4 (0 ≤ 2x ≤ 1.0) with a wide doping range are prepared and characterized. ► The optimal Al concentration in the LiNi0.5−xAl2xMn1.5−xO4 is 0.05 ≤ 2x ≤ 0.10. ► The thermal stability of LiNi0.5−xAl2xMn1.5−xO4 electrodes before 225 °C is effectively improved by Al-doping.
Co-reporter:L.C. Zhang, X. Sun, Z. Hu, C.C. Yuan, C.H. Chen
Journal of Power Sources 2012 Volume 204() pp:149-154
Publication Date(Web):15 April 2012
DOI:10.1016/j.jpowsour.2011.12.028
A commercial rice paper (RP) is used for the first time as a separator membrane in lithium-ion batteries. It consists of interpenetrating cellulose fibers with a diameter of about 5–40 μm to form a highly porous structure. The RP is found to be electrochemically stable at a potential below 4.5 V vs. Li+/Li. Several kinds of electrode materials including graphite, LiFePO4, LiCoO2 and LiMn2O4 are used to test the compatibility of the RP in Li-ion batteries and to compare with a commercial polypropylene/polyethylene/polypropylene separator membrane. The RP separator with the same thickness gives rise to a lower resistance than the commercial separator. Due to the wonderful flexibility, high porosity, low cost and excellent electrochemical performance of the RP membrane, it is promising to partially replace commercial separators in lithium-ion batteries for low power applications.Highlights► It is the first time to use a rice paper in lithium-ion batteries. ► The investigated rice paper is found to be highly porous and compatible in battery conditions. ► We propose to use such a new separator in lithium-ion batteries for some low power applications.
Co-reporter:G.B. Zhong, Y.Y. Wang, Y.Q. Yu, C.H. Chen
Journal of Power Sources 2012 Volume 205() pp:385-393
Publication Date(Web):1 May 2012
DOI:10.1016/j.jpowsour.2011.12.037
LiNi0.5Mn1.5O4 and LiNi0.45M0.10Mn1.45O4 (M = Fe, Co, Cr) powders are prepared and systematically investigated as 5 V cathode materials for lithium-ion batteries. X-ray diffraction, Raman spectroscopy and scanning electron microscopy are employed to study their structures. The electrochemical cyclic performance and rate capability at room temperature and 55 °C are characterized and compared. The results indicate that the introductions of Fe, Co or Cr ions favor the crystal structure of the spinel in a Fd3¯m symmetry compared with a symmetry of P4332 for the un-doped LiNi0.5Mn1.5O4. Excellent cycle life is measured for these 5 V Co- and Fe-doped electrodes. When cycled at 1C rate, about 95.9%, 93.1% and 81.7% of their initial capacities can be retained after 500 cycles for LiNi0.45Co0.10Mn1.45O4, LiNi0.45Fe0.10Mn1.45O4 and LiNi0.45Cr0.10Mn1.45O4, respectively. Their electrochemical performances at 55 °C are also much better than the un-doped sample. Three possible capacity fading mechanisms including structural transformation, the dissolution of the spinel into the electrolyte, and the oxidation of the electrolyte are discussed. The decomposition of the electrolyte is regarded as the most important mechanism.Highlights► Trivalent transition metal elements Fe-, Co- and Cr-doped LiNi0.45M0.10Mn1.45O4 (M = Fe, Co and Cr) powders are prepared and investigated under the same conditions. ► LiNi0.45Fe0.10Mn1.45O4 and LiNi0.45Co0.10Mn1.45O4 show excellent cyclic and rate performances at room temperature and 55 °C. ► The Fe- and Co-doped spinels exhibit the best data in literature for this important 5 V cathode material.
Co-reporter:Si-Rong Li, Yu Qiao, Yi Sun, Si-Yuan Ge, Yi-Meng Chen, Ingo Lieberwirth, Yan Yu, Chun-Hua Chen
Electrochimica Acta 2012 Volume 81() pp:191-196
Publication Date(Web):30 October 2012
DOI:10.1016/j.electacta.2012.07.086
Micrometer Li1.05Mn1.95O4 has been synthesized by solid state reactions with the nano-Mn3O4 as a precursor. X-ray diffraction, scanning electron microscopy and laser particle sizer are employed to investigate the structures, morphologies and particle size distributions of the powder. The micrometer Li1.05Mn1.95O4 exhibits good rate performance at room temperature with a specific capacity of 98.4 mAh g−1 at 5 C. The Li1.05Mn1.95O4/Li half cell also shows good cycling performance at elevated temperature with 90.5% of its initial capacity retained after 100 cycles at 1 C. At −20 °C, the Li1.05Mn1.95O4 delivers a stable cycling performance with a specific capacity of 84.5 mAh g−1, being 84.1% of the capacity at room temperature. The cyclic voltammetry (CV) and rate performance measurements illustrate an increasing polarization with decreasing the temperature. In addition, the diffusion coefficients of lithium ions (DLi+)(DLi+) in Li1.05Mn1.95O4 at various temperatures (25, 0, −10 and −20 °C) are determined to be in the magnitude of 10−10 to 10−12 cm2 s−1 by cyclic voltammetry (CV) method.Highlights► Micrometer Li1.05Mn1.95O4 is synthesized by a solid state reaction method with nano-Mn3O4 as a precursor. ► The optimal Li1.05Mn1.95O4 sample shows good cycling stability at elevated temperature (90.5% of its initial capacity after 100 cycles at 1 C). ► The optimal Li1.05Mn1.95O4 sample shows high rate performance (98.4 mAh g−1 at 5 C at room temperature). ► Lithium ion diffusion coefficients are derived at −20, −10, 0 and 25 °C.
Co-reporter:Si-Rong Li, Si-Yuan Ge, Yu Qiao, Yi-Meng Chen, Xu-Yong Feng, Jun-Fa Zhu, Chun-Hua Chen
Electrochimica Acta 2012 Volume 64() pp:81-86
Publication Date(Web):1 March 2012
DOI:10.1016/j.electacta.2011.12.131
Three-dimensional (3D) porous V2O5 and Fe0.1V2O5.15 thin films have been prepared by electrostatic spray deposition technique. X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy are employed to investigate the structures and valence states of the films. Galvanostatic cell cycling, cyclic voltammetry and impedance spectroscopy are used to characterize their electrochemical properties. The Fe0.1V2O5.15 thin film shows much better cycling performance than the non-doped V2O5 thin film. Fe3+ can act as a stabilizing agent in the layered V2O5 and increase the reversibility of the charge and discharge processes towards deeper depth of lithium insertion/extraction. The dissolution of the active material in the electrolyte can also be significantly suppressed in the Fe-doped sample. Nevertheless, the Fe-doping causes a slight decrease in lithium ion diffusion coefficient.Highlights► The special 3D-porous structure is a main factor to achieve good rate capability in both V2O5 and Fe0.1V2O5.15 samples. ► Fe-doping improves the cycling stability (195 mAh g−1 after 48 cycles). ► Lithium ion diffusion coefficients are derived in V2O5 and Fe0.1V2O5.15 electrodes.
Co-reporter:XuYong Feng;Chen Shen;Xin Fang
Science Bulletin 2012 Volume 57( Issue 32) pp:4176-4180
Publication Date(Web):2012 November
DOI:10.1007/s11434-012-5248-2
Li1±xNi0.5Mn1.5O4 (x=0.05, 0) spinel powders were synthesized using a solid-state reaction. Their structures were characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Their electrochemical properties for use as active cathode materials in lithium-ion batteries were measured. The LiNi0.5Mn1.5O4, Li1.05Ni0.5Mn1.5O4 and Li0.95Ni0.5Mn1.5O4 samples crystallized in Fd\(\bar 3\)m,Fd\(\bar 3\)m and P4332, respectively. The LiNi0.5Mn1.5O4 and Li0.95Ni0.5Mn1.5O4 samples exhibited better cycle performance than the Li1.05Ni0.5Mn1.5O4 sample, while Li0.95Ni0.5Mn1.5O4 had the worst rate performance. Thus, it appears unnecessary to introduce nominal lithium nonstoichiometry in LiNi0.5Mn1.5O4 electrode materials.
Co-reporter:Suqing Wang, Sirong Li, Yi Sun, Xuyong Feng and Chunhua Chen
Energy & Environmental Science 2011 vol. 4(Issue 8) pp:2854-2857
Publication Date(Web):01 Jun 2011
DOI:10.1039/C1EE01172C
Three-dimensional (3D) porous vanadium pentoxide (V2O5) thin films were synthesized by electrostatic spray deposition followed by annealing at 350 °C in air. The interconnected pore networks facilitate the kinetics of lithium-ion diffusion and help the porous V2O5 with stable capacity, high energy efficiency and excellent rate capability as a cathode material for lithium batteries.
Co-reporter:Suqing Wang, Zhenda Lu, Da Wang, Chunguang Li, Chunhua Chen and Yadong Yin
Journal of Materials Chemistry A 2011 vol. 21(Issue 17) pp:6365-6369
Publication Date(Web):16 Mar 2011
DOI:10.1039/C0JM04398B
Monodisperse V2O5 microspheres with a porous structure were synthesized by a very simple hydrolysis method and subsequent reduction/oxidation treatment at high temperatures. The porous V2O5 used as a cathode material for lithium-ion batteries (LIBs) shows a stable and highly reversible capacity. It also shows excellent low-temperature behavior with a reversible capacity of 102 mA h g−1 at −20 °C. The excellent performance can be attributed to the porous structure of the V2O5 spheres, which are more electrochemically active due to a large interfacial contact area with the electrolyte. We believe the strategy of creating porosity may be extended to other electrode materials to improve the performance of lithium ion batteries.
Co-reporter:Y. Jin, C.P. Yang, X.H. Rui, T. Cheng, C.H. Chen
Journal of Power Sources 2011 Volume 196(Issue 13) pp:5623-5630
Publication Date(Web):1 July 2011
DOI:10.1016/j.jpowsour.2011.02.059
In addition to lattice doping and carbon-coating, surface modification with other metal oxides can also improve the electrochemical performance of LiFePO4 powders. In this work, highly conductive vanadium oxide (V2O3) is in situ produced during the synthesis of carbon-coated LiFePO4 (LiFePO4/C) powders by a solid state reaction process and acts as a surface modifier. The structures and compositions of LiFePO4/C samples containing 0–10 mol% vanadium are analyzed by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. Their electrochemical properties are also characterized with galvanostatic cell cycling and cyclic voltammetry. It is found that vanadium is present in the form of V2O3 that is incorporated in the carbon phase. The vanadium-modified LiFePO4/C samples show improved rate capability and low-temperature performance. Their apparent lithium diffusion coefficient is in the range of 10−12 to 10−10 cm2 s−1 depending on the vanadium content. Among the investigated samples, the one with 5 mol% vanadium exhibits the best electrochemical performance.Highlights► Introduction of a small amount of vanadium into the carbon-coated LiFePO4 particles leads to significant improvement in the rate capability and low-temperature performance. ► The modification mechanism is directly related to the formation of conductive V2O3 nano-grains. ► V2O3 increases the degree of graphitization of the carbon layer so that the composite conductivity is increased.
Co-reporter:X.H. Rui, Y. Jin, X.Y. Feng, L.C. Zhang, C.H. Chen
Journal of Power Sources 2011 Volume 196(Issue 4) pp:2109-2114
Publication Date(Web):15 February 2011
DOI:10.1016/j.jpowsour.2010.10.063
The electrochemical properties of the LiFePO4/C (LFP/C) and Li3V2(PO4)3/C (LVP/C) samples are investigated using Li-ion half cells at various low temperatures of 23, 0, −10 and −20 °C in the electrolyte 1.0 M LiPF6/EC + DMC (1:1 w/w). In the voltage range of 2.5–4.3 V at 0.3 C rate, the LFP/C electrode shows a stable reversible discharge capacity of 45.4 mAh g−1 at −20 °C, which is 31.5% of the capacity obtained at 23 °C. In the voltage range of 3.0–4.3 V at 0.3 C rate, the LVP/C electrode delivers a high stable reversible discharge capacity of 108.1 mAh g−1 at −20 °C, being 86.7% of the capacity at 23 °C. The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements illustrate that the resistance and cell polarization of LFP/C at various low temperatures are larger than those of LVP/C. In addition, using CV method, the apparent chemical diffusion coefficient of lithium ions (DLi+app) in LFP and LVP at various low temperatures are in the magnitude of 10−11 and 10−10 cm2 s−1, respectively, and the DLi+app decreasing rate of LFP as the temperature is much larger than LVP, meaning that the kinetics of the LFP electrode is relatively slow. The activation energies of LFP and LVP are calculated to be 47.48 and 6.57 kJ mol−1, respectively, which further indicates that the extraction/intercalation of Li+ in LVP is much easier than in LFP. The high reversible capacity of LVP/C at −20 °C makes it an attractive cathode for low-temperature lithium ion batteries.
Co-reporter:X.H. Rui, N. Yesibolati, C.H. Chen
Journal of Power Sources 2011 Volume 196(Issue 4) pp:2279-2282
Publication Date(Web):15 February 2011
DOI:10.1016/j.jpowsour.2010.09.024
The carbon coated monoclinic Li3V2(PO4)3 (LVP/C) powder is successfully synthesized by a carbothermal reduction method using crystal sugar as the carbon source. Its structure and physicochemical properties are investigated using X-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopy and electrochemical methods. The LVP/C electrode exhibits stable reversible capacities of 203 and 102 mAh g−1 in the potential ranges of 3.0–0.0 V and 3.0–1.0 V versus Li+/Li, respectively. It is identified that the insertion/extraction of Li+ undergoes a series of two-phase transition processes between 3.0 and 1.6 V and a single phase process between 1.6 and 0.0 V. The ex situ XRD patterns of the electrodes at various lithiated states indicate that the monoclinic structure can still be retained during charge–discharge process and the insertion/deinsertion of lithium ions occur reversibly, which provides an excellent cycling stability with high energy efficiency.
Co-reporter:Yi Sun, Xu-Yong Feng, Chun-Hua Chen
Journal of Power Sources 2011 Volume 196(Issue 2) pp:784-787
Publication Date(Web):15 January 2011
DOI:10.1016/j.jpowsour.2010.07.065
Cobalt oxide thin films composed of hollow spherical Co3O4 particles have been prepared by a two-step method. The first step involves in the synthesis of hollow cobalt alkoxide particles in a stable suspension from mixed polyalcohol solutions of cobalt acetate in oil bath at 170 °C. The second step includes the thin film fabrication by electrostatic spray deposition (ESD) and subsequent heat treatment in nitrogen. The obtained Co3O4 films with the unique hollow particle microstructure exhibit high reversible capacity of above 1000 mAh g−1 during up to 50 cycles and good rate capability. The films are promising negative electrodes for high energy lithium-ion batteries.
Co-reporter:G.B. Zhong, Y.Y. Wang, Z.C. Zhang, C.H. Chen
Electrochimica Acta 2011 Volume 56(Issue 18) pp:6554-6561
Publication Date(Web):15 July 2011
DOI:10.1016/j.electacta.2011.03.093
The effects of Al substitution for Ni or (and) Mn in LiNi0.5Mn1.5O4 spinel on the structures and electrochemical properties are investigated. Powders of LiNi0.5Mn1.5O4, Li0.95Ni0.45Mn1.5Al0.05O4, LiNi0.475Mn1.475Al0.05O4 and Li1.05Ni0.5Mn1.45Al0.05O4 are synthesized by a thermopolymerization method. Their structures and electrochemical properties are studied by X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, cyclic voltammetry and galvanostatic charge–discharge testing. The introduction of Al in these LiNi0.5Mn1.5O4 samples has resulted in structure variation, and greatly improved their cyclic performance and rate capability. The effects of Al substitutions for Ni and Mn in the LiNi0.5Mn1.5O4 are different. Compared with LiNi0.5Mn1.5O4, Li0.95Ni0.45Mn1.5Al0.05O4 demonstrates higher specific capacity at room temperature but faster capacity fading at elevated temperatures. Li1.05Ni0.5Mn1.45Al0.05O4 displays a lower discharge capacity but better capacity retention at 55 °C. Moreover, the cyclic performance and rate capability of the Ni-substituted Li0.95Ni0.45Mn1.5Al0.05O4, Ni/Mn co-substituted LiNi0.475Mn1.475Al0.05O4 and Mn-substituted Li1.05Ni0.5Mn1.45Al0.05O4 at room temperature are similar, and have improved substantially compared with the Al-free LiNi0.5Mn1.5O4 sample.Highlights► Aluminum doped LiNi0.5Mn1.5O4 powders are synthesized by a thermopolymerization process. ► The comparison of Al doping between Mn sites and Ni sites is made for the first time. ► Properly Al-doped LiNi0.5Mn1.5O4 shows excellent cycling stability at 55 °C with the fading rate as low as 0.015% per cycle. ► At room temperature, the capacity fading rate may be even slower (less than 0.01%) and the rate capability is very good (114 mAh g−1 at 10 C).
Co-reporter:H.F. Xiang, J.Y. Shi, X.Y. Feng, X.W. Ge, H.H. Wang, C.H. Chen
Electrochimica Acta 2011 Volume 56(Issue 15) pp:5322-5327
Publication Date(Web):1 June 2011
DOI:10.1016/j.electacta.2011.04.001
Electrochemical exfoliation of graphite in the flame-retarded electrolyte is used for the preparation of novel carbon materials for the first time. Graphitic platelets with submicron thickness are prepared by an electrochemical graphite exfoliation route in the trimethyl phosphate (TMP) based electrolyte. The morphology and size of the graphitic platelets can be controlled by adjusting the reaction temperature and current density. A possible mechanism is proposed for the interesting graphite exfoliation in the TMP-based electrolyte. Compared with common micrometer-scale graphite and graphene nanosheets, this novel graphitic material exhibits different voltage profiles but good rate capability as anode in the Li-ion batteries.Highlights► Graphitic platelets with submicron thickness are prepared by an electrochemical graphite exfoliation route in the trimethyl phosphate (TMP) based electrolyte for the first time. ► TMP is a special exfoliating agent for the electrochemical exfoliation of graphite. ► The dimension and morphology of graphitic platelets are dependent on the current density and reaction temperature. ► The graphitic platelets with submicron thickness are used as anode material for Li-ion batteries and exhibit good rate capability.
Co-reporter:X.H. Rui, N. Yesibolati, S.R. Li, C.C. Yuan, C.H. Chen
Solid State Ionics 2011 Volume 187(Issue 1) pp:58-63
Publication Date(Web):8 April 2011
DOI:10.1016/j.ssi.2011.02.013
The chemical diffusion coefficients of lithium ion (DLi+) in intercalation-type Li3V2(PO4)3 (LVP) anode material as a function of cell voltage between 3.0 and 0.0 V are systematically determined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). The true chemical diffusion coefficients (DLi+true) obtained from EIS and GITT for the single-phase region (1.6–0.0 V vs. Li+/Li) are in the range of 10−10 to 10−9 cm2 s−1 and 10−11 to 10−10 cm2 s−1, respectively, and exhibit a decreasing trend of the change of DLi+true vs. voltage as the discharge and charge proceeded. The apparent chemical diffusion coefficients (DLi+app) measured from CV and GITT for the two-phase regions (around 2.5–1.6 V) are in the range of 10−10 cm2 s−1 and 10−12 to 10−10 cm2 s−1, respectively. For GITT, DLi+app vs. voltage plots display a characteristic of “W” shape due to the strong interactions of Li+ with surrounding ions. Finally, the DLi+ values of LVP anode are compared with other anode materials, illustrating that LVP can also be used as a potential anode material to achieve high rate capability.► The Li3V2(PO4)3 is used as an intercalation-type anode material. ► The lithium transport property in Li3V2(PO4)3 at low potentials is investigated. ► True and apparent diffusion coefficients are measured by three different methods.
Co-reporter:C.X. Ding, Y.C. Bai, X.Y. Feng, C.H. Chen
Solid State Ionics 2011 Volume 189(Issue 1) pp:69-73
Publication Date(Web):6 May 2011
DOI:10.1016/j.ssi.2011.02.015
To improve the electrochemical properties of LiNi1/3Co1/3Mn1/3O2, powders of Zr-doped mixed transition metal oxides, LiNi1/3Co1/3Mn1/3-xZrxO2 (x = 0, 0.01, 0.025, 0.05) (LNCMZ), are synthesized via a thermal polymerization method. Their structure and electrochemical properties are investigated by X-ray diffraction, galvanostatic charge–discharge of LNCMZ/Li half cells, galvanostatic intermittent titration technique (GITT), direct current resistance measurement and AC impedance spectroscopy. All of the prepared LNCMZ samples have a hexagonal α-NaFeO2 structure whose lattice parameters increase monotonously with the Zr content. The Zr doping results in higher lithium diffusion coefficient in LNCMZ and more stable resistance during the electrochemical cycling of LNCMZ/Li cells so that the Zr-doped samples show notable improvement of cycling performance and rate capability. The sample LiNi1/3Co1/3Mn1/3-0.01Zr0.01O2 exhibits the best electrochemical performance with capacity retention of 92.7% during 100 cycles and a capacity of 133.9 mAh g−1 at 8 C rate, corresponding to 71.5% of its capacity at 0.1 C.Research highlights► l Cationic substitution of Mn4+ by Zr4+ in the lattice of LiNi1/3Co1/3Mn1/3O2. ► l Zr substitution causes higher diffusion coefficient and better rate performance. ► l Zr-doping stabilizes the lattice structure, resulting in better cycling stability.
Co-reporter:H. F. Xiang;Q. Wang;D. Z. Wang;D. W. Zhang
Journal of Applied Electrochemistry 2011 Volume 41( Issue 8) pp:965-971
Publication Date(Web):2011 August
DOI:10.1007/s10800-011-0323-y
The poor compatibility between dimethyl methylphosphonate (DMMP)-based electrolytes and carbonaceous anodes was improved by optimizing the compositions of the electrolyte and the electrode. In the electrolyte, the contents of DMMP and ethylene carbonate had significant effects on both the safety characteristic and the compatibility with carbonaceous anode. For the spherical mesocarbon microbeads, a conductive composite system containing the flake graphite and the carbon nanoparticles was beneficial to the highest reversible capacity (330 mAh g−1). In the common graphite anode, the water-soluble binder was the better choice than poly(vinylidene fluoride) to suppress the reductive decomposition of DMMP. In brief, the optimized compatibility indicated an extensive prospect of the flame-retarded electrolyte in the battery industry.
Co-reporter:H.F. Xiang, C.H. Chen, J. Zhang, K. Amine
Journal of Power Sources 2010 Volume 195(Issue 2) pp:604-609
Publication Date(Web):15 January 2010
DOI:10.1016/j.jpowsour.2009.07.036
Co-reporter:Suqing Wang, Jingying Zhang, Chunhua Chen
Journal of Power Sources 2010 Volume 195(Issue 16) pp:5379-5381
Publication Date(Web):15 August 2010
DOI:10.1016/j.jpowsour.2010.03.035
A magnetite (Fe3O4) powder composed of uniform sub-micrometer spherical particles has been successfully synthesized by a hydrothermal method at low temperature. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and galvanostatic cell cycling are employed to characterize the structure and electrochemical performance of the as-prepared Fe3O4 spheroids. The magnetite shows a stable and reversible capacity of over 900 mAh g−1 during up to 60 cycles and good rate capability. The experimental results suggest that the Fe3O4 synthesized by this method is a promising anode material for high energy-density lithium-ion batteries.
Co-reporter:L. Wang, C.X. Ding, L.C. Zhang, H.W. Xu, D.W. Zhang, T. Cheng, C.H. Chen
Journal of Power Sources 2010 Volume 195(Issue 15) pp:5052-5056
Publication Date(Web):1 August 2010
DOI:10.1016/j.jpowsour.2010.01.088
Electrospun carbon–silicon composite nanofiber is employed as anode material for lithium ion batteries. The morphology of composite nanofiber is optimized on the C/Si ratio to make sure well distribution of silicon particles in carbon matrix. The C/Si (77/23, w/w) nanofiber exhibits large reversible capacity up to 1240 mAh g−1 and excellent capacity retention. Ex situ scanning electron microscopy is also conducted to study the morphology change during discharge/charge cycle, and the result reveals that fibrous morphology can effectively prevent the electrode from mechanical failure due to the large volume expansion during lithium insertion in silicon. AC impedance spectroscopy reveals the possible reason of unsatisfactory rate capability of the nanofiber. These results indicate that this novel C/Si composite nanofiber may has some limitations on high power lithium ion batteries, but it can be a very attractive potential anode material for high energy-density lithium-ion batteries.
Co-reporter:H.F. Xiang, H.W. Lin, B. Yin, C.P. Zhang, X.W. Ge, C.H. Chen
Journal of Power Sources 2010 Volume 195(Issue 1) pp:335-340
Publication Date(Web):1 January 2010
DOI:10.1016/j.jpowsour.2009.06.096
The effect of activation temperature on Li-ion batteries with flame-retarded electrolytes containing 5 wt.% dimethyl methyl phosphonate (DMMP) and trimethyl phosphate (TMP) is investigated respectively. It is found that activation at elevated temperature promotes the formation of a stable solid electrolyte interface layer on the graphite electrode, which may significantly suppress the reductive decomposition of DMMP and TMP and avoid graphite exfoliation. But fierce oxidation of the electrolytes on the LiCoO2 electrode at elevated temperature is harmful to the cell performance. A procedure of so-called altered temperature activation (ATA) is adopted for LiCoO2/graphite full-cells. It can compromise the contradictive effects on the separate electrodes at the elevated temperature. High capacity and good rate capability are obtained for the cells with the flame-retarded electrolytes, especially for the TMP-containing electrolyte.
Co-reporter:Long Wang, Lin-Chao Zhang, Ingo Lieberwirth, Hong-Wei Xu, Chun-Hua Chen
Electrochemistry Communications 2010 Volume 12(Issue 1) pp:52-55
Publication Date(Web):January 2010
DOI:10.1016/j.elecom.2009.10.034
A monoclinic lithium vanadium phosphate (Li3V2(PO4)3) and carbon composite thin film (LVP/C) is prepared via electrostatic spray deposition. The film is studied with X-ray diffraction, scanning and transmission electron microscopy and galvanostatic cell cycling. The LVP/C film is composed of carbon-coated Li3V2(PO4)3 nanoparticles (50 nm) that are well distributed in a carbon matrix. In the voltage range of 3.0–4.3 V, it exhibits a reversible capacity of 118 mA h g−1 and good capacity retention at the current rate of 1 C, while delivers 80 mA h g−1 at 24 C. These results suggest a practical strategy to develop new cathode materials for high power lithium-ion batteries.
Co-reporter:H.F. Xiang, B. Yin, H. Wang, H.W. Lin, X.W. Ge, S. Xie, C.H. Chen
Electrochimica Acta 2010 Volume 55(Issue 18) pp:5204-5209
Publication Date(Web):15 July 2010
DOI:10.1016/j.electacta.2010.04.041
Room temperature ionic liquids (RTILs) with high safety characteristic usually have high viscosity and melting point, which is adverse for the application of RTIL-based electrolytes in Li-ion batteries. In this investigation, a promising RTIL, i.e. PP13TFSI consisting of N-methyl-N-propylpiperidinium (PP13) cation and bis(trifluoromethanesulfonyl)imide (TFSI) anion is synthesized. The effect of the content of Li salt in the electrolytes containing PP13TFSI and LiTFSI on the ionic conductivity and cell performance is investigated. The electrolyte of 0.3 mol kg−1 LiTFSI/PP13TFSI is recommended for its higher lithium transference number and discharge capacity in the LiCoO2/Li cell than other electrolytes. In addition, it is found that, by introducing 20% diethyl carbonate (DEC) as a co-solvent into pure RTIL electrolyte, the rate capability and low-temperature performance of the LiCoO2/Li cells are improved obviously, without sacrificing its safety characteristics. It suggests that a component with low viscosity and melting point, i.e. DEC, is necessary to effectively overcome the shortcomings of RTIL for the application in Li-ion batteries.
Co-reporter:X. Fang, Y. Lu, N. Ding, X.Y. Feng, C. Liu, C.H. Chen
Electrochimica Acta 2010 Volume 55(Issue 3) pp:832-837
Publication Date(Web):1 January 2010
DOI:10.1016/j.electacta.2009.09.046
Nano- and micro-sized LiNi0.5Mn1.5O4 particles are prepared via the thermal decomposition of a ternary eutectic Li–Ni–Mn acetate. Lithium acetate, nickel acetate and manganese acetate can form a ternary eutectic Li–Ni–Mn acetate below 80 °C. After further calcination, nano-sized LiNi0.5Mn1.5O4 particles can be obtained at an extremely low temperature (500 °C). When the sintering temperature goes above 700 °C, the particle size increases, and at 900 °C micro-sized LiNi0.5Mn1.5O4 particles (with a diameter of about 4 μm) are obtained. Electrochemical tests show that the micro-sized LiNi0.5Mn1.5O4 powders (sintered at 900 °C) exhibit the best capacity retention at 25 °C, and after 100 cycles, 97% of initial discharge capacity can still be reached. Nano-sized LiNi0.5Mn1.5O4 powders (sintered at 700 °C) perform the best at low temperatures; when cycled at −10 °C and charged and discharged at a rate of 1 C, nano-sized LiNi0.5Mn1.5O4 powders can deliver a capacity as high as 110 mAh g−1.
Co-reporter:X.H. Rui, C. Li, J. Liu, T. Cheng, C.H. Chen
Electrochimica Acta 2010 Volume 55(Issue 22) pp:6761-6767
Publication Date(Web):1 September 2010
DOI:10.1016/j.electacta.2010.05.093
The carbon coated monoclinic Li3V2(PO4)3 (LVP/C) cathode materials are synthesized via a sol–gel method using oxalic acid as a chelating reagent and maltose as a carbon source. The effect of carbon content on the synthesis of LVP/C composites is investigated using X-ray diffraction, scanning electron microscopy, galvanostatic charge/discharge and DC resistance measurements. The results show that, among the LVP/C powders with different carbon content (5.7, 9.6, 11.6 and 15.3 wt.%), the sample with 11.6 wt.% carbon content gives rise to the corresponding (LVP/C) ∥Li half cell with a low DC resistance and superior electrochemical performance, especially with excellent rate capability. Its discharge capacity decreases by only 7.2% from 125 mAh g−1 at 0.5 C to 116 mAh g−1 at 5 C between 3.0 and 4.3 V. The maltose-based sol–gel method is feasible for the preparation of LVP/C composites for high power lithium ion batteries.
Co-reporter:X.H. Rui, N. Ding, J. Liu, C. Li, C.H. Chen
Electrochimica Acta 2010 Volume 55(Issue 7) pp:2384-2390
Publication Date(Web):28 February 2010
DOI:10.1016/j.electacta.2009.11.096
The chemical diffusion coefficients of lithium ions (DLi+)(DLi+) in Li3V2(PO4)3 between 3.0 and 4.8 V are systematically determined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). The DLi+DLi+ values are found to be dependent on the voltage state of charge and discharge. Based on the results from all the three techniques, the true diffusion coefficients (DLi+true) measured in single-phase region are in the range of 10−9 to 10−10 cm2 s−1. Its apparent diffusion coefficients (DLi+app) measured in two-phase regions by CV and GITT range from 10−10 to 10−11 cm2 s−1 and 10−8 to 10−13 cm2 s−1, respectively, depending on the potentials. By the GITT, the DLi+DLi+ varies non-linearly in a “W” shape with the charge–discharge voltage, which is ascribed to the strong interactions of Li+ with surrounding ions. Finally, the chemical diffusion coefficients of lithium ions measured by CV, EIS and GITT are compared to each other.
Co-reporter:Jian-Wu Wen, Da-Wei Zhang, Yuan-Cheng Teng, Chun-Hua Chen, Ying Xiong
Electrochimica Acta 2010 Volume 55(Issue 7) pp:2306-2310
Publication Date(Web):28 February 2010
DOI:10.1016/j.electacta.2009.11.084
We present the mechanism for the synthesis of a layered Li(Ni1/3Co1/3Mn1/3)O2 compound by a modified radiated gel method. Pure-phase Li(Ni1/3Co1/3Mn1/3)O2 material was achieved when the polymer gel was calcined at 900 °C between 15 and 30 h. The unit cell parameter c decreased, and a varied slightly with increased sintering time. Electrochemical characterization revealed that the optimized sample (25 h) had a high initial discharge capacity of 188 mAh/g (2.8–4.5 V, 20 mA/g), an excellent capacity retention of 90.1% after 30 cycles and a good rate performance.
Co-reporter:G.Q. Yue, C. Liu, D.Z. Wang, Y. Wang, Q.F. Yuan, R. Xu, F.G. Zhao, C.H. Chen
Materials Research Bulletin 2010 45(9) pp: 1319-1323
Publication Date(Web):
DOI:10.1016/j.materresbull.2010.04.025
Co-reporter:Chunhua Chen, Ning Ding, Long Wang, Yan Yu, Ingo Lieberwirth
Journal of Power Sources 2009 Volume 189(Issue 1) pp:552-556
Publication Date(Web):1 April 2009
DOI:10.1016/j.jpowsour.2008.10.052
Transition metal oxides represent a new type of anode materials for lithium-ion batteries. Due to their high capacity (usually above 700 mAh g−1) and excellent cycleability, they have attracted much attention in recent years. Regarding the electrochemical reaction mechanism for this type of electrode, the conversion reaction mechanism proposed by Tarascon and co-workers is widely accepted, i.e. MOx + 2xLi ⇆ M + xLi2O. Nevertheless, in our recent explorations, we have found some new phenomena which may help us to further understand the electrode reaction mechanism, and even pose a necessity to modify the current conversion reaction mechanism. These new phenomena can be summarized as electrochemical milling, capacity rise and no-metal-formation effects.
Co-reporter:Ning Ding, Jing Xu, Yaxuan Yao, Gerhard Wegner, Ingo Lieberwirth, Chunhua Chen
Journal of Power Sources 2009 Volume 192(Issue 2) pp:644-651
Publication Date(Web):15 July 2009
DOI:10.1016/j.jpowsour.2009.03.017
Silicon working as anode for Li-ion batteries has attracted much attention due to its high capacity (∼4200 mAh g−1). However, due to the large volume expansion during lithiation, the capacity of silicon fades very fast. In this systematic study, we focus on the issue to fight the capacity fading. Results show that Si with sodium carboxymethyl cellulose (Na-CMC) as a polymer binder exhibits a better cyclability than that with poly(vinylidene fluoride) (PVDF). Yet differing from the system used in PVDF, the addition of vinylene carbonate (VC) does not improve or even worsens the performance of the system using Na-CMC. In addition, the small particle size of Si, a large amount of carbon black (CB), the good choice of electrolyte/conducting salt and charge–discharge window also play important roles to enhance the cyclability of Si. It is found that electrode consisting of 40 wt.% nano-Si, 40 wt.% carbon black and 20 wt.% Na-CMC (pH 3.5) displays the best cyclability, and in the voltage range from 0 to 0.8 V, after 200 cycles, its capacity can still keep 738 mAh g−1 (C/2, in 1 M LiPF6 ethylene carbonate/diethyl carbonate electrolyte, with VC-free), almost twice as that of graphite.
Co-reporter:L. Wang, H.W. Xu, P.C. Chen, D.W. Zhang, C.X. Ding, C.H. Chen
Journal of Power Sources 2009 Volume 193(Issue 2) pp:846-850
Publication Date(Web):5 September 2009
DOI:10.1016/j.jpowsour.2009.03.063
Iron oxide materials are attractive anode materials for lithium–ion batteries for their high capacity and low cost compared with graphite and most of other transition metal oxides. Porous carbon-free α-Fe2O3 films with two types of pore size distribution were prepared by electrostatic spray deposition, and they were characterized by X-ray diffraction, scanning electron microscopy and X-ray absorption near-edge spectroscopy. The 200 °C-deposited thin film exhibits a high reversible capacity of up to 1080 mAh g−1, while the initial capacity loss is at a remarkable low level (19.8%). Besides, the energy efficiency and energy specific average potential (Eav) of the Fe2O3 films during charge/discharge process were also investigated. The results indicate that the porous α-Fe2O3 films have significantly higher energy density than Li4Ti5O12 while it has a similar Eav of about 1.5 V. Due to the porous structure that can buffer the volume changes during lithium intercalation/de-intercalation, the films exhibit stable cycling performance. As a potential anode material for high performance lithium–ion batteries that can be applied on electric vehicle and energy storage, rate capability and electrochemical performance under high-low temperatures were also investigated.
Co-reporter:H.F. Xiang, H. Wang, C.H. Chen, X.W. Ge, S. Guo, J.H. Sun, W.Q. Hu
Journal of Power Sources 2009 Volume 191(Issue 2) pp:575-581
Publication Date(Web):15 June 2009
DOI:10.1016/j.jpowsour.2009.02.045
Thermal stability of LiPF6-based electrolyte (1 M LiPF6/EC + DMC) was studied by in-situ FTIR spectroscopy and C80 calorimetry, which indicated that the electrolyte underwent furious polymerization and decomposition reactions and sharp heat flow was generated below 225 °C. The thermal stability of the electrolyte in contact with various delithiated cathodes (LixCoO2, LixNi0.8Co0.15Al0.05O2, LixNi1/3Co1/3Mn1/3O2, LixMn2O4, LixNi0.5Mn0.5O2, LixNi0.5Mn1.5O4 and LixFePO4) was also investigated by C80 calorimetry. The results show that the cathode materials except for LixFePO4 usually have an enhancement effect on the decomposition of the electrolyte, but LixFePO4 exhibits a suppression effect on the reactions of the electrolyte. LixFePO4 is found to be with excellent thermal stability. Among the other cathodes, LixCoO2, LixNi0.8Co0.15Al0.05O2, LixNi0.5Mn0.5O2 and LixNi0.5Mn1.5O4 promote the decomposition of electrolyte by releasing oxygen and thus considered not favorable for safety, but LixNi1/3Co1/3Mn1/3O2 with a lesser reaction heat and LixMn2O4 with even less heat flow in the low temperature range (50–225 °C) are believed as promising cathodes for better safety. By comparing X-ray diffraction (XRD) patterns of these cathode materials at room temperature and those heated to 300 °C in the presence of the electrolyte, we have found that LixFePO4 only has experienced tiny structure change, which is greatly different from the other cathode materials.
Co-reporter:X. Fang, N. Ding, X.Y. Feng, Y. Lu, C.H. Chen
Electrochimica Acta 2009 Volume 54(Issue 28) pp:7471-7475
Publication Date(Web):1 December 2009
DOI:10.1016/j.electacta.2009.07.084
LiNi0.5Mn1.5O4 powders are prepared via a new co-precipitation method. In this method, chloride salts are used as precursors and ammonia as a precipitator. The impurity of chlorine can be removed via a thermal decomposition of NH4Cl in the subsequent calcination. X-ray diffraction pattern reveals that the final product is a pure spinel phase of LiNi0.5Mn1.5O4. Scanning electron microscopy shows that the powders have an octahedron shape with a particle size of about 2 μm. Electrochemical test shows that the LiNi0.5Mn1.5O4 powders exhibit an excellent cycling performance and after 300 cycles, the capacity retention is 83%. The lithium diffusion coefficient is measured to be 5.94 × 10−11 cm2 s−1 at 4.1 V, 4.35 × 10−10 cm2 s−1 at 4.75 V and 7.0 × 10−10 cm2 s−1 at 4.86 V. The mechanism of capacity loss is also explored. After 300 cycles, the cell parameter ‘a’ decreases by 0.54% for the quenched sample (LiNi0.5Mn1.5O4−δ) and by 0.42% for the annealed sample (LiNi0.5Mn1.5O4). Besides, it is the first time to identify experimentally that the Ni and Mn ions dissolved in the electrolyte can be further deposited on the surface of anode.
Co-reporter:Ning Ding, Xuyong Feng, Shuhua Liu, Jing Xu, Xin Fang, Ingo Lieberwirth, Chunhua Chen
Electrochemistry Communications 2009 Volume 11(Issue 3) pp:538-541
Publication Date(Web):March 2009
DOI:10.1016/j.elecom.2008.12.017
A VO2 · 0.43H2O powder with a flaky particle morphology was synthesized via a hydrothermal reduction method. It was characterized by scanning electron microscopy, electron energy loss spectroscopy, and thermogravimetric analysis. As an electrode material for rechargeable lithium batteries, it was used both as a cathode versus lithium anode and as an anode versus LiCoO2, LiFePO4 or LiNi0.5Mn1.5O4 cathode. The VO2 · 0.43H2O electrode exhibits an extraordinary superiority with high capacity (160 mAh g−1), high energy efficiency (95%), excellent cyclability (142.5 mAh g−1 after 500 cycles) and rate capability (100 mAh g−1 at 10 C-rate).
Co-reporter:X.H. Rui, C. Li, C.H. Chen
Electrochimica Acta 2009 Volume 54(Issue 12) pp:3374-3380
Publication Date(Web):30 April 2009
DOI:10.1016/j.electacta.2009.01.011
The carbon-coated monoclinic Li3V2(PO4)3 (LVP) cathode materials were synthesized by a solid-state reaction process under the same conditions using citric acid, glucose, PVDF and starch, respectively, as both reduction agents and carbon coating sources. The carbon coating can enhance the conductivity of the composite materials and hinder the growth of Li3V2(PO4)3 particles. Their structures and physicochemical properties were investigated using X-ray diffraction (XRD), thermogravimetric (TG), scanning electron microscopy (SEM) and electrochemical methods. In the voltage region of 3.0–4.3 V, the electrochemical cycling of these LVP/C electrodes all presents good rate capability and excellent cycle stability. It is found that the citric acid-derived LVP owns the largest reversible capacity of 118 mAh g−1 with no capacity fading during 100 cycles at the rate of 0.2C, and the PVDF-derived LVP possesses a capacity of 95 mAh g−1 even at the rate of 5C. While in the voltage region of 3.0–4.8 V, all samples exhibit a slightly poorer cycle performance with the capacity retention of about 86% after 50 cycles at the rate of 0.2C. The reasons for electrochemical performance of the carbon coated Li3V2(PO4)3 composites are also discussed. The solid-state reaction is feasible for the preparation of the carbon coated Li3V2(PO4)3 composites which can offer favorable properties for commercial applications.
Co-reporter:Da Wang, Hua-Yun Xu, Man Gu, Chun-Hua Chen
Electrochemistry Communications 2009 Volume 11(Issue 1) pp:50-53
Publication Date(Web):January 2009
DOI:10.1016/j.elecom.2008.10.029
Ti-based anode materials with the nominal compositions Li4Ti5CuxO12 + x (x = 0, 0.075, 0.15, 0.3, 0.6, 1.20 and 1.67) were synthesized at 800 °C by a solid-state reaction process. X-ray diffraction analysis indicated that the sintered samples were composed of intergrown spinel-type Li4Ti5O12 and Li2CuTi3O8, and a small amount of Li2O. Scanning electron microscopy, electrical resistance measurement and galvanostatic cell cycling were also employed to characterize the structure and properties of the double spinel samples. It is proposed that the first lithiation of the component Li2CuTi3O8 leads to the in situ production of Cu that can significantly improve the rate performance of Li4Ti5CuxO12 + x. The optimal nominal composition is Li4Ti5Cu0.15O12.15.
Co-reporter:Ning Ding, Shuhua Liu, Xuyong Feng, Haitao Gao, Xin Fang, Jing Xu, Wolfgang Tremel, Ingo Lieberwirth and Chunhua Chen
Crystal Growth & Design 2009 Volume 9(Issue 4) pp:1723-1728
Publication Date(Web):February 4, 2009
DOI:10.1021/cg800645c
V2O5 nanofibers and three vanadium-based oxides with different structures (MnV2O6 nanosheets, FeVO4·0.92H2O nanoneedles, and Sn2VO6·0.78H2O nanoparticles) were synthesized via a hydrothermal method. Field-emission scanning electron microscopy, transmission electron microscopy, electron diffraction, energy dispersive X-ray, and electron energy loss spectroscopy were employed to characterize their morphologies and crystal structures. Electrochemical tests in rechargeable lithium batteries show that among these vanadium-based oxides Sn2VO6·0.78H2O nanoparticles exhibit the highest capacity, more than 1700 mAh g−1, and can keep good capacity retention. The magnetic properties of MnV2O6 nanosheets and FeVO4·0.92H2O nanoneedles were also investigated.
Co-reporter:N. Ding, J. Xu, Y.X. Yao, G. Wegner, X. Fang, C.H. Chen, I. Lieberwirth
Solid State Ionics 2009 Volume 180(2–3) pp:222-225
Publication Date(Web):9 March 2009
DOI:10.1016/j.ssi.2008.12.015
The diffusion coefficients of lithium ions (DLi+) in nano-Si were determined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). DLi+ values are estimated to be ~ 10− 12 cm2 s− 1 and exhibit a “W” type varying with the lithium concentration in silicon. Two minimum regions of DLi+ (at Li2.1 ± 0.2Si and Li3.2 ± 0.2Si) are found, which probably result from two amorphous compositions (a-Li7Si3 and a-Li13Si4). Besides the two minimum regions, one maximum DLi+ is observed at Li15Si4, corresponding to the crystallization of highly lithiated amorphous LixSi.
Co-reporter:C.X. Ding, Q.S. Meng, L. Wang, C.H. Chen
Materials Research Bulletin 2009 44(3) pp: 492-498
Publication Date(Web):
DOI:10.1016/j.materresbull.2008.08.012
Co-reporter:N. Ding;X. Fang;J. Xu;Y. X. Yao;J. Zhu
Journal of Applied Electrochemistry 2009 Volume 39( Issue 7) pp:995-1001
Publication Date(Web):2009 July
DOI:10.1007/s10800-008-9747-4
Lithium-ion cells are potential energy storage devices in planetary exploration due to their high energy density and long lifespan. The high intensity of γ-ray radiation in outer space poses a great challenge to lithium-ion cells. In this study, radioactive Co-60 was applied as the radiation source to investigate the performance of lithium-ion cells with the electrolyte radiated by γ-rays. Two kinds of cathode (LiMn2O4, LiNi0.8Co0.15Al0.05O2) and three kinds of anode (Li, graphite, Li4Ti5O12) were examined. There are two new mechanisms in the cells with a radiated electrolyte which affect the cell voltage and cycling performance: (i) erosion of the lithium electrode in the radiated electrolyte in the cases of half cells and lithium symmetrical cells; and (ii) electrochemical reaction between carboxyl species and the lithium extracted from the cathode in the case of full cells.
Co-reporter:H.F. Xiang, Q.Y. Jin, R. Wang, C.H. Chen, X.W. Ge
Journal of Power Sources 2008 Volume 179(Issue 1) pp:351-356
Publication Date(Web):15 April 2008
DOI:10.1016/j.jpowsour.2007.12.089
The compatibility between dimethyl methylphosphonate (DMMP)-based electrolyte of 1 M LiPF6/EC + DMC + DMMP (1:1:2 wt.) and spinel materials Li4Ti5O12 and LiNi0.5Mn1.5O4 was reviewed, respectively. The cell performance and impedance of 3-V LiNi0.5Mn1.5O4/Li4Ti5O12 lithium-ion cell with the DMMP-based nonflammable electrolyte was compared with the baseline electrolyte of 1 M LiPF6/EC + DMC (1:1 wt.). The nonflammable DMMP-based electrolyte exhibited good compatibility with spinel Li4Ti5O12 anode and high-voltage LiNi0.5Mn1.5O4 cathode, and acceptable cycling performance in the LiNi0.5Mn1.5O4/Li4Ti5O12 full-cell, except for the higher impedance than that in the baseline electrolyte. All of the results disclosed that the 3 V LiNi0.5Mn1.5O4/Li4Ti5O12 lithium-ion battery was a promising choice for the nonflammable DMMP-based electrolyte.
Co-reporter:L. Wang, Y. Yu, P.C. Chen, D.W. Zhang, C.H. Chen
Journal of Power Sources 2008 Volume 183(Issue 2) pp:717-723
Publication Date(Web):1 September 2008
DOI:10.1016/j.jpowsour.2008.05.079
Carbon-based nanofibers can be used as anode materials for lithium-ion batteries. Both pure carbon nanofiber and C/Fe3O4 composite nanofibers were prepared by electrospinning and subsequent carbonization processes. The composition and structures were characterized by Fourier transformation infrared spectroscopy, X-ray diffraction, scanning and transmission electron microscopy. The electrochemical properties were evaluated in coin-type cells versus metallic lithium. It is found that after an annealing temperature of 500–700 °C, the carbon has disordered structure while Fe3O4 is nanocrystalline with a particle size from 8.5 to 52 nm. Compared with the pure carbon nanofiber, the 600 °C-carbonized C/Fe3O4 composite nanofiber exhibits much better electrochemical performance with a high reversible capacity of 1007 mAh g−1 at the 80th cycle and excellent rate capability. A beneficial powderization phenomenon is discovered during the electrochemical cycling. This study suggests that the optimized C/Fe3O4 composite nanofiber is a promising anode material for high performance lithium-ion batteries.
Co-reporter:H.F. Xiang, X. Zhang, Q.Y. Jin, C.P. Zhang, C.H. Chen, X.W. Ge
Journal of Power Sources 2008 Volume 183(Issue 1) pp:355-360
Publication Date(Web):15 August 2008
DOI:10.1016/j.jpowsour.2008.04.091
The effect of the capacity matchup between cathode and anode in the LiNi0.5Mn1.5O4/Li4Ti5O12 cell system on cycling property, choice of electrolyte, high voltage and overcharge tolerances was investigated by comparing the cells with Li4Ti5O12 limiting capacity with the cells with LiNi0.5Mn1.5O4 limiting capacity. The former exhibits better cycling performance and less limitation of electrolyte choice than the latter. Furthermore, the Li4Ti5O12-limited cell exhibits better tolerance to high voltage and overcharge than the LiNi0.5Mn1.5O4-limited cell, owing to taking advantage of the extra capacity of Li4Ti5O12 below 1 V. It is thus recommended that the LiNi0.5Mn1.5O4/Li4Ti5O12 cell whose capacity is limited by Li4Ti5O12 anode should be used to extend the application of the state-of-the-art lithium-ion batteries.
Co-reporter:X.L. Yao, S. Xie, H.Q. Nian, C.H. Chen
Journal of Alloys and Compounds 2008 Volume 465(1–2) pp:375-379
Publication Date(Web):6 October 2008
DOI:10.1016/j.jallcom.2007.10.113
The electrochemical behavior of Li1.33Ti1.67O4 was investigated as an anode material discharged to 0 V using X-ray diffraction (XRD), galvanostatic cell cycling and ac impedance spectroscopy. The XRD results indicate that the lattice framework of Li1.33Ti1.67O4 is almost unchanged even after it is discharged to 0 V. The Li1.33Ti1.67O4 electrode can be cycled in the voltage range between 0 and 3.0 V with excellent cyclability and a capacity of about 200 mAh/g. During the discharge process, a 0.75 V plateau is also observed in addition to the usual 1.5 V plateau. The capacity associated with the 0.75 V plateau varies with current density and temperature. The possible cause of this low potential plateau is discussed and attributed to a carbon-triggered-capacity (CTC) effect.
Co-reporter:H. Y. Xu;Q. Y. Wang;C. H. Chen
Journal of Solid State Electrochemistry 2008 Volume 12( Issue 9) pp:1173-1178
Publication Date(Web):2008 September
DOI:10.1007/s10008-008-0546-y
Layered Li[Li0.16Ni0.21Mn0.63]O2 and Li[Li0.2Ni0.2Mn0.6]O2 compounds were successfully synthesized by radiated polymer gel (RPG) method. The effect of deficient Li on the structure and electrochemical performance was investigated by means of X-ray diffraction, X-ray absorption near-edge spectroscopy and electrochemical cell cycling. The reduced Ni valence in Li[Li0.16Ni0.21Mn0.63]O2 leads to a higher capacity owing to faster Li+ chemical diffusivity relative to the baseline composition Li[Li0.2Ni0.2Mn0.6]O2. Cyclic voltammograms (CV) and a simultaneous direct current (DC) resistance measurement were also performed on Li/Li[Li0.16Ni0.21Mn0.63]O2 and Li/Li[Li0.2Ni0.2Mn0.6]O2 cells. Li[Li0.16Ni0.21Mn0.63]O2 shows better electrochemical performance with a reversible capacity of 158 mA hg−1 at 1C rate at 20 °C.
Co-reporter:Y. Yu;Y. Shi;C.-H. Chen
Advanced Materials 2007 Volume 19(Issue 7) pp:993-997
Publication Date(Web):12 MAR 2007
DOI:10.1002/adma.200601667
Thin-film anodes for Li-ion batteries prepared by using electrostatic spray deposition are reported. They consist of a tin-based amorphous oxide composite with a porous, spherical, multideck-cage morphology (see figure). The electrochemical properties of the thin-film electrodes are shown to be improved significantly by introducing Li2O and CuO, the ternary Li2O–CuO–SnO2 electrode being demonstrated to exhibit the best performance.
Co-reporter:H.F. Xiang, H.Y. Xu, Z.Z. Wang, C.H. Chen
Journal of Power Sources 2007 Volume 173(Issue 1) pp:562-564
Publication Date(Web):8 November 2007
DOI:10.1016/j.jpowsour.2007.05.001
Dimethyl methylphosphonate (DMMP) was used as a flame retardant additive to 1 M LiPF6/EC + DEC system. The flammability, electrochemical stability and cycling performance of electrolyte containing DMMP were studied. The addition of DMMP to electrolytes provides a significant suppression in the flammability of the electrolyte concluded from the measurements of self-extinguish time and limited oxygen index. The totally nonflammable electrolytes can be achieved with only 10 wt.% DMMP addition—the highly efficient retardant additive. The addition of DMMP causes little damage on the cell electrochemical performance. DMMP is a promising flame retardant additive to improve the safety of lithium-ion batteries.
Co-reporter:H.F. Xiang, Q.Y. Jin, C.H. Chen, X.W. Ge, S. Guo, J.H. Sun
Journal of Power Sources 2007 Volume 174(Issue 1) pp:335-341
Publication Date(Web):22 November 2007
DOI:10.1016/j.jpowsour.2007.09.025
Dimethyl methylphosphonate (DMMP) was used as a cosolvent to reformulate the nonflammable electrolyte of 1 M LiPF6/EC + DEC + DMMP (1:1:2 wt.) in order to improve the safety characteristics of lithium-ion batteries. The flammability, cell performance, low-temperature performance and thermal stability of the DMMP-based electrolyte were compared with the electrolyte of 1 M LiPF6/EC + DEC (1:1 wt.). The nonflammable electrolyte exhibits good oxidation stability at the LiCoO2 cathode and poor reduction stability at the mesocarbon microbead (MCMB) and surface-modified graphite (SMG) anodes. The addition of vinyl ethylene carbonate (VEC) to the DMMP-based electrolyte provided a significant improvement in the reduction stability at the carbonaceous electrodes. Furthermore, it was found that the addition of DMMP resulted in optimized low-temperature performance and varied thermal stability of the electrolytes. All of the results indicated the novel DMMP-based electrolyte is a promising nonflammable electrolyte to resolve the safety concerns of lithium-ion batteries.
Co-reporter:P.C. Wang, H.P. Ding, Tursun Bark, C.H. Chen
Electrochimica Acta 2007 Volume 52(Issue 24) pp:6650-6655
Publication Date(Web):1 August 2007
DOI:10.1016/j.electacta.2007.04.072
Nanosized α-Fe2O3 (ca. 50 nm) and Li–Fe composite oxides (ca. 29 nm) powders were synthesized via gel polymer route. The gels were obtained with thermal polymerization of acrylic acid solutions of iron and lithium nitrates. The calcination of these gels at temperatures from 300 °C to 500 °C results in α-Fe2O3 from Fe(NO3)3 precursor and Li–Fe composite oxides Li2O–Fe3O4–LiFeO2 from a mixed precursors of Fe(NO3)3 and LiNO3. Thermal gravimetric analysis, X-ray diffraction and transmission electron microscopy were used to investigate the precursors and products. The electrochemical performance of the Fe-based oxides was also evaluated. After 200 cycles, their capacity can be as high as 1300 mAh/g for α-Fe2O3 and 1400 mAh/g for Li–Fe oxide while the initial capacity loss is as low as 21.8%. The Li–Fe oxide electrodes exhibit better capacity retention than the α-Fe2O3 electrodes. They are interesting negative electrodes for high energy density lithium-ion batteries.
Co-reporter:S.Q. Wang, J.Y. Zhang, C.H. Chen
Scripta Materialia 2007 Volume 57(Issue 4) pp:337-340
Publication Date(Web):August 2007
DOI:10.1016/j.scriptamat.2007.04.034
Highly porous microspheres of CuO with a dandelion-like hollow structure were prepared by a hydrothermal synthesis method. X-ray diffraction, scanning electron microscopy, galvanostatic cell cycling and cyclic voltammetry were employed to characterize the structure and electrochemical performance of this unique CuO powder. This CuO electrode showed stable good capacity retention with a reversible capacity of over 600 mA h g−1 during up to 50 cycles. This method may be suitable for larger-scale production of these CuO hollow microspheres for practical applications.
Co-reporter:J. W. Wen;H. J. Liu;H. Wu;C. H. Chen
Journal of Materials Science 2007 Volume 42( Issue 18) pp:7696-7701
Publication Date(Web):2007 September
DOI:10.1007/s10853-007-1673-z
Layered LiCo1/3Ni1/3Mn1/3O2 as a lithium insertion positive-electrode material was prepared by a radiated polymer gel method. The synthesis conditions and microstructure, morphology and electrochemical properties of the products were investigated by XRD, SEM and electrochemical cell cycling. It was found that the positive-electrode material annealed at 950 °C showed the best electrochemical property with the first specific discharge capacity of 178 mAh/g at C/6 and stable cycling ability between 2.8 and 4.5 V versus Li/Li+. The optimized LiCo1/3Ni1/3Mn1/3O2 exhibited rather good rate capability with the specific capacity of 173 mAh/g at 0.2C and 116 mAh/g at 4C under a fast charge and discharge mode in rate performance test.
Co-reporter:Yan Yu;Yi Shi;Chun-Hua Chen
Chemistry – An Asian Journal 2006 Volume 1(Issue 6) pp:
Publication Date(Web):13 NOV 2006
DOI:10.1002/asia.200600157
Highly porous reticular Li2O/CoO composite thin films fabricated by electrostatic spray deposition were investigated by using X-ray diffraction, scanning electron microscopy, galvanostatic cell-cycling measurements, and AC impedance spectroscopy measurements. The results of the electrochemical tests indicate that the initial coulombic efficiency and capacity retention are dependent on Li2O content and the specific surface area of the deposited layer. Irrespective of the type of substrate, the electrode gave the best electrochemical performance when the molar ratio of Li to Co was controlled at 1:1. At the optimal composition, at 0.2 C the initial coulombic efficiency was as high as 81.9 % and 83.6 % for the film on Cu foil and on porous Ni, respectively. The Li2O/CoO (Li/Co=1:1) films on Ni foam and Cu foil had sustained capacities of up to 790 and 715 mAh g−1, respectively, at a rate of 1 C over 100 cycles at 25 °C. Similar cycling experiments carried out at 70 °C showed that the capacity is temperature-sensitive, and it exhibited reversible capacities as high as 1018 (Cu foil) and 1269 mAh g−1 (Ni foam) for up to 100 cycles. The thin-film electrodes on Ni foam always performed better than those on Cu foil. Cycling at elevated temperature (70 °C) also resulted in a significant increase in capacity.
Co-reporter:X.L. Yao, S. Xie, C.H. Chen, Q.S. Wang, J.H. Sun, Y.L. Li, S.X. Lu
Electrochimica Acta 2005 Volume 50(Issue 20) pp:4076-4081
Publication Date(Web):25 July 2005
DOI:10.1016/j.electacta.2005.01.034
The aim of this work was to compare the electrochemical behaviors and safety performance of graphite and the lithium titanate spinel Li1.33Ti1.67O4 with half-cells versus Li metal. Their electrochemical properties in 1 M LiPF6/EC + DEC (1:1 w/w) or 1 M LiPF6/PC + DEC (1:1 w/w) at room and elevated temperatures (30 and 60 °C) have been studied using galvanostatic cycling. At 30 °C graphite has higher reversible capacity than Li1.33Ti1.67O4 when using the LiPF6/EC + DEC as electrolyte. At 60 °C graphite declines in cell capacity yet Li1.33Ti1.67O4 remains almost unchanged. In a propylene carbonate (PC) containing electrolyte, graphite electrode exfoliates and loses its mechanical integrity while Li1.33Ti1.67O4 electrode is very stable. An accelerating rate calorimeter (ARC) and microcalorimeter have been used to compare the thermal stability of lithiated lithium titanate spinel and graphite. Results show that Li1.33Ti1.67O4 may be used as an alternative anode material offering good battery performance and higher safety.
Co-reporter:Y.F. Zhou, S. Xie, C.H. Chen
Electrochimica Acta 2005 Volume 50(Issue 24) pp:4728-4735
Publication Date(Web):30 August 2005
DOI:10.1016/j.electacta.2005.03.003
Carbon encapsulated graphite was prepared by coating polyurea on the surface of natural graphite particles via interfacial polymerization followed by a pre-oxidation at 250 °C in air and a heat treatment at 850 °C in nitrogen. FT-IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to investigate the structure of the graphite before and after the surface modification. Galvanostatic cycling, dc impedance spectroscopy, and cyclic voltammetry were used to investigate the electrochemical properties of the modified graphite as the anode material of lithium cells. The modified graphite shows a large improvement in electrochemical performance such as higher reversible capacity and better cycleability compared with the natural graphite. It can work stably in a PC-based electrolyte with the PC content up to 25 vol.% because the encapsulated carbon can depress the co-intercalation of solvated lithium ion. The initial coulombic efficiency of C-NG and NG in non-PC electrolyte is 74.9 and 88.5%, respectively.
Co-reporter:N. Ding, X.W. Ge, C.H. Chen
Materials Research Bulletin 2005 Volume 40(Issue 9) pp:1451-1459
Publication Date(Web):1 September 2005
DOI:10.1016/j.materresbull.2005.04.022
A new synthetic route, i.e. the radiated polymer gel (RPG) method, has been developed and demonstrated for the production of LiCoO2 powders. The process involved two processes: (1) obtaining a gel by polymerizing a mixed solution of an acrylic monomer and an aqueous solution of lithium and cobalt salts under γ-ray irradiation conditions and (2) obtaining LiCoO2 powders by drying and calcining the gel. Thermogravimetric analysis (TGA), X-ray diffraction (XRD) and electron scanning microscopy (SEM) were employed to study the reaction process and the structures of the powders. Galvanostatic cell cycling, cyclic voltammetry and ac impedance spectroscopy were used to evaluate the electrochemical properties of the LiCoO2 powders. It was found that a pure phase of LiCoO2 can be obtained at the calcination temperature of 800 °C. Both the particle size (micrometer range) and specific charge/discharge capacity of an RPG-LiCoO2 powder increase with increasing the concentration of its precursor solution.
Co-reporter:Y. Yu, J.L. Shui, C.H. Chen
Solid State Communications 2005 Volume 135(Issue 8) pp:485-489
Publication Date(Web):August 2005
DOI:10.1016/j.ssc.2005.05.045
Spinel Li4Ti5O12 thin films are important for the fabrication of rechargeable lithium microbatteries. Porous thin films of Li4Ti5O12 were prepared by electrostatic spray deposition (ESD) technique with lithium acetate and titanium butoxide as the precursors. The structures of these films were analyzed by scanning electron microscopy and X-ray diffraction. Coin-type cells with a liquid electrolyte were made with the Li4Ti5O12 films against metallic lithium. Their electrochemical performance was investigated by means of galvanostatic cell cycling, cyclic voltammetry and Ac impedance spectroscopy. It was found that pure spinel phase of Li4Ti5O12 was obtained. After annealing at the optimal temperature of 700 °C, the films can deliver a reversible specific capacity of about 150 mAh/g with excellent capacity retention after 70 cycles. Their electrochemical characteristics were quite comparable with those of the Li4Ti5O12 laminate electrodes containing carbon black additive.
Co-reporter:Yan Yu, Chun-Hua Chen, Jiang-Lan Shui,Song Xie
Angewandte Chemie International Edition 2005 44(43) pp:7085-7089
Publication Date(Web):
DOI:10.1002/anie.200501905
Co-reporter:Yan Yu;Chun-Hua Chen ;Jiang-Lan Shui;Song Xie
Angewandte Chemie 2005 Volume 117(Issue 43) pp:
Publication Date(Web):7 OCT 2005
DOI:10.1002/ange.200501905
Als inaktive Komponente betrachtetes Li2O übernimmt drei wichtige Aufgaben in neuen Kohlenstoff-freien CoO-Li2O-Kompositfilmen (siehe Rasterelektronenmikroskopiebild): Es verhindert die Bildung von CoO-Partikeln bei der Synthese, es oxidiert Co2+ zu Co3+ und es puffert die damit verbundenen Strukturänderungen ab. Die Filme wurden durch elektrostatische Sprayabscheidung auf leitenden Nickelschaum-Substraten erzeugt und zeigen große anfängliche Entladungskapazitäten und geringe Kapazitätsverluste im ersten Zyklus.
Co-reporter:S.Q. Zhang, S. Xie, C.H. Chen
Materials Science and Engineering: B 2005 Volume 121(1–2) pp:160-165
Publication Date(Web):25 July 2005
DOI:10.1016/j.mseb.2005.03.018
A new type of Li3PO4-based composite electrolyte films was fabricated with an approach similar to Bellcore technology. The films are composed of Li3PO4 fine powder, SiO2 nanoparticles, dibutyl(o-)phthalate (DBP) and a polymer matrix poly(vinyldiene fluoride). X-ray diffraction, scanning electron microscopy and photo scattering techniques were employed to analyze the Li3PO4 powder synthesized by a chemical precipitation method. AC impedance spectroscopy was used to measure the electrical properties of the composite electrolyte films. The effect of the addition of different concentration nanoparticles SiO2 and DBP on the conductivities of the Li3PO4-based composite electrolyte was analyzed. It is found that the optimized starting composition with a mass ratio Li3PO4:SiO2:DBP:Kynar 2801 (PVDF–12% HFP):acetone equal to 30:5:30:35:100 gives rise to the highest ionic conductivity of 2.4 × 10−8 S/cm at 30 °C and 1.7 × 10−7 S/cm at 100 °C with an activation energy of 0.32 eV. It is comparable with that of Li3PO4 thin films obtained from sputtering or electrostatic spray deposition (ESD) techniques. The presence of the plasticizer DBP and nanoparticles SiO2 plays an important role to minimize the resistance for lithium-ion conduction between Li3PO4 particles. In addition, for the graphite/composite/graphite measurement cell, the apparent conductivity for the charge-transfer process between the electrolyte film and the graphite electrode is about one order of magnitude lower than that of the composite electrolyte with an activation energy of 0.56 eV. The development of such composite films opens opportunities to thermally stable electrolytes for rechargeable lithium batteries.
Co-reporter:J. Zhang, S. Xie, X. Wei, Y.J. Xiang, C.H. Chen
Journal of Power Sources 2004 Volume 137(Issue 1) pp:88-92
Publication Date(Web):5 October 2004
DOI:10.1016/j.jpowsour.2004.05.041
In order to investigate the effect of copper oxide naturally formed on copper as the common anode current collector and as an electrode additive, the electrochemical behavior of lithium insertion in three naturally surface-oxidized copper powders and one copper foil was studied. Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), particle size distribution measurement, galvanostatic cell cycling and cyclic voltammetry were employed for structural and electrochemical characterization. Although the XRD analysis can only detect the presence of pure Cu phase, the XPS analysis reveals clearly the presence of a CuO layer on the copper powders or the copper foil. The thickness of this CuO layer is estimated as thick as 147 nm. The lithiation capacity associated with this CuO layer can reach 48 mAh/g for copper powders but only 1 mAh/g for the foil. This small capacity, or 5.2 × 10−3 mAh/cm2 per unit area of copper foil, is fortunately negligible compared with that of a common anode material in a lithium-ion cell; while the capacity associated with this CuO layer must be taken into account when using a copper powder as an additive to improve the cycling stability.
Co-reporter:J Zhang, Y.J Xiang, Y Yu, S Xie, G.S Jiang, C.H Chen
Journal of Power Sources 2004 Volume 132(1–2) pp:187-194
Publication Date(Web):20 May 2004
DOI:10.1016/j.jpowsour.2004.01.035
As the cathode materials for rechargeable lithium batteries, five commercial lithium cobalt oxide powders have been investigated for a comparative study. The X-ray diffraction analysis indicates that all these powders exhibit the α-NaFeO2 layered structure. The size distribution and morphology were analyzed by particle sedimentation method and scanning electron microscopy (SEM). Their electrochemical properties including cycleability and especially 3.6 V plateau efficiency, a recently required control parameter, are compared. Two kinds of modifications, i.e. Li2CO3 coating and high-temperature treatment, have been applied to improve the electrochemical performance of one of these five powders. After the high-temperature treatment in air, cobalt oxidation-state becomes higher and Li(LixCo1−x)O2 is formed. Both of the two modified means can significantly improve the 3.6 V-plateau efficiency through suppressing the cell impedance rise during cycling. A general discussion on the factors influencing the plateau efficiency is also given.
Co-reporter:C.H. Chen, J. Liu, M.E. Stoll, G. Henriksen, D.R. Vissers, K. Amine
Journal of Power Sources 2004 Volume 128(Issue 2) pp:278-285
Publication Date(Web):5 April 2004
DOI:10.1016/j.jpowsour.2003.10.009
Non-doped and aluminum-doped LiNi0.8Co0.2O2 cathodes from three industrial developers coupled with graphite anodes were made into lithium-ion cells for high-power applications. The powder morphology of the active cathode materials was examined by a scanning electron microscope. The electrochemical performance of these cells was investigated by hybrid pulse power characterization (HPPC) testing, accelerated aging, and AC impedance measurement of symmetric cells. Although all of the fresh cells are found to meet and exceed the power requirements set by PNGV, the power capability of those cells with non-doped LiNi 0.8Co0.2O2 cathodes fades rapidly due to the rise of the cell impedance. Al-doping is found very effective to suppress the cell impedance rise by stabilizing the charge-transfer impedance on the cathode side. The stabilization mechanism may be related to the low average oxidation state of nickel ions in the cathode. The powder morphology also plays a secondary role in determining the impedance stabilization.
Co-reporter:C.H. Chen, S. Xie, E. Sperling, A.S. Yang, G. Henriksen, K. Amine
Solid State Ionics 2004 Volume 167(3–4) pp:263-272
Publication Date(Web):27 February 2004
DOI:10.1016/j.ssi.2004.01.008
High lithium-ion conductivity, especially at room temperature, and chemical stability against reducing lithiated negative electrodes are two main requirements for a solid electrolyte in an all solid-state lithium battery. Perovskite-type materials ABO3 in which A=La, Li and B=Ti exhibit high lithium ion conductivities, with a bulk conductivity of 1.2 mS/cm at 30 °C and an apparent grain-boundary conductivity of 0.03 mS/cm; this solid electrolyte is only stable above 1.6 V (vs. Li°) because Ti(IV) can be reduced to Ti(III) below this voltage. In this study, we investigated a highly conducting perovskite-type Li–Sr–Ta–Zr–O structure, in which the A and B cations of SrZrO3 are partially substituted by Li and Ta, respectively. Four compositions were selected and synthesized to find an optimal composition. Sintering temperatures between 1200 and 1400 °C were used to determine the optimum synthesis conditions. X-ray diffraction (XRD) was used to identify the crystalline phases within the sintered products. The lithium-ion conductivity of these materials was measured by AC impedance spectroscopy. The sample with optimized composition, Li3/8Sr7/16Ta3/4Zr1/4O3, exhibited a bulk lithium-ion conductivity of 0.2 mS/cm at 30 °C and an apparent grain-boundary conductivity of 0.13 mS/cm. This solid electrolyte was found to be stable above 1.0 V against metallic lithium. Below 1.0 V, about 0.08 mol lithium can be inserted irreversibly per mol of Li3/8Sr7/16Ta3/4Zr1/4O3.
Co-reporter:J.L. Shui, B. Lin, W.L. Liu, P.H. Yang, G.S. Jiang, C.H. Chen
Materials Science and Engineering: B 2004 Volume 113(Issue 3) pp:236-241
Publication Date(Web):15 November 2004
DOI:10.1016/j.mseb.2004.08.012
A spray-drying process was used to coat a Li(Li0.033Mn1.967)O4 powder with a spinel-type Li–Mn–Co–O surface layer. After high-temperature (850 °C) annealing, the coated powder was made into a positive electrode for rechargeable lithium cells. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectrometry (EDAX) were applied to analyze the structure of the annealed powders. It is found that a spinel-type Li[Mn1.56(1−δ)Co0.44(1−δ)Li2δ]O4 layer was probably formed on the Li(Li0.033Mn1.967)O4 particles. The particle size distribution of the spray-treated powder becomes narrower than the original Li(Li0.033Mn1.967)O4 powder. As the active positive electrode material, the coated Li(Li0.033Mn1.967)O4 powder shows excellent electrochemical properties, especially in suppressing the capacity fading during elevated temperature cycling (with a fading rate of 0.045% per cycle). The rate capability of the cells is also improved as a result of this treatment.
Co-reporter:S.Q. Wang, J.Y. Zhang, C.H. Chen
Scripta Materialia (August 2007) Volume 57(Issue 4) pp:337-340
Publication Date(Web):1 August 2007
DOI:10.1016/j.scriptamat.2007.04.034
Highly porous microspheres of CuO with a dandelion-like hollow structure were prepared by a hydrothermal synthesis method. X-ray diffraction, scanning electron microscopy, galvanostatic cell cycling and cyclic voltammetry were employed to characterize the structure and electrochemical performance of this unique CuO powder. This CuO electrode showed stable good capacity retention with a reversible capacity of over 600 mA h g−1 during up to 50 cycles. This method may be suitable for larger-scale production of these CuO hollow microspheres for practical applications.
Co-reporter:Suqing Wang, Zhenda Lu, Da Wang, Chunguang Li, Chunhua Chen and Yadong Yin
Journal of Materials Chemistry A 2011 - vol. 21(Issue 17) pp:NaN6369-6369
Publication Date(Web):2011/03/16
DOI:10.1039/C0JM04398B
Monodisperse V2O5 microspheres with a porous structure were synthesized by a very simple hydrolysis method and subsequent reduction/oxidation treatment at high temperatures. The porous V2O5 used as a cathode material for lithium-ion batteries (LIBs) shows a stable and highly reversible capacity. It also shows excellent low-temperature behavior with a reversible capacity of 102 mA h g−1 at −20 °C. The excellent performance can be attributed to the porous structure of the V2O5 spheres, which are more electrochemically active due to a large interfacial contact area with the electrolyte. We believe the strategy of creating porosity may be extended to other electrode materials to improve the performance of lithium ion batteries.
Co-reporter:Xuyong Feng, Ning Ding, Yingchao Dong, Chunhua Chen and Zhaolin Liu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 48) pp:NaN15315-15315
Publication Date(Web):2013/10/21
DOI:10.1039/C3TA13676K
A simple surface modification of Li4Ti5O12 powder is made with an aqueous CrO3 solution to improve its electrochemical properties. At a high current rate of 30 C, the specific capacity of the Li4Ti5O12 increases by about 60% from its original 80 to 130 mA h g−1. After the modification with the CrO3 solution, a few surface phases including lithium chromate (Li2CrO4), Cr2O5 and anatase are found to co-exist in the final product. Among these three phases, Li2CrO4 and Cr2O5 can improve while anatase deteriorates the rate performance of Li4Ti5O12. The AC impedance spectra and electron spin resonance (ESR) spectra reveal that the improvement of rate performance is correlated with the presence of Ti3+, which can increase the conductivity of the Li4Ti5O12 sample. Lithium chromate (Li2CrO4) and Cr2O5 react with lithium to form lithium rich phases (Li3+xCrO4 and LiyCr2O5) of low potential, which stabilize Li7Ti5O12 with high electric conductivity and result in better rate performance. Besides improved rate performance, the cycle performance of the modified Li4Ti5O12 samples is almost at the same level with the original Li4Ti5O12, suggesting that this proposed modification method is efficient and harmless.
Co-reporter:Xuyong Feng, Chen Shen, Ning Ding and Chunhua Chen
Journal of Materials Chemistry A 2012 - vol. 22(Issue 39) pp:NaN20865-20865
Publication Date(Web):2012/08/20
DOI:10.1039/C2JM32673F
Lithium chromium titanium oxide (LiCrTiO4) spinel powders are synthesized by an acrylic acid polymerization method. The lithium intercalation capacity of the LiCrTiO4 sample synthesized in air is about 150 mA h g−1, which is very close to its theoretical capacity (157 mA h g−1). In addition to its very good cycle performance similar to that of Li4Ti5O12, the LiCrTiO4 shows excellent rate performance with no obvious capacity loss at the current density from 1C to 10C rates. By means of Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy, the LiCrTiO4 sample synthesized in air is found to contain a small amount of lithium chromium oxide (LiCrxOy, y > 1/2 + 3x/2) as an in situ produced modifier that can improve the conductivity of the electrode.
Co-reporter:Bangkun Zou, Qiao Hu, Danqi Qu, Ran Yu, Yuting Zhou, Zhongfeng Tang and Chunhua Chen
Journal of Materials Chemistry A 2016 - vol. 4(Issue 11) pp:NaN4124-4124
Publication Date(Web):2016/02/12
DOI:10.1039/C6TA00069J
Nano-spherical Li-rich cathodes and MnxCo1−xO anodes are synthesized from as-solvothermal MnxCo1−xCO3 (x = 1, 0.8, and 0.5) precursors. Based on the half-cell studies of these materials, Li-rich 0.5Li2MnO3·0.5LiMn0.5Ni0.5O2 with a high reversible capacity of 247 mA h g−1 and binary transition metal oxide Mn0.8Co0.2O with a reversible capacity of 759 mA h g−1 are selected respectively as the optimal positive and negative electrodes to construct a full cell. Such an electrode match-up, i.e. Li-rich/Mn0.8Co0.2O full cell (“N-cell”), allows no need for pre-activation of the metal oxide anode. This “N-cell” can deliver a high reversible capacity of 205 mA h g−1 and particularly rather high volumetric energy density, which is about 31% higher than that of a Li-rich/graphite full cell (“T-cell”). The special coulombic efficiency match-up and tailored microstructures and compositions of the electrode materials are all crucial to achieve such a high energy density.
Co-reporter:Yu Qiao, Si-Rong Li, Yan Yu and Chun-Hua Chen
Journal of Materials Chemistry A 2013 - vol. 1(Issue 3) pp:NaN867-867
Publication Date(Web):2012/10/25
DOI:10.1039/C2TA00204C
Yolk-structured microspheres of spinel LiMn2O4 are successfully prepared by a specially designed multi-step synthesis procedure involving precipitation, controlled oxidation, selective etching and chemical lithiation. Solid-structured and hollow-structured LiMn2O4 are also synthesized by a similar method for comparison. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller method and IR spectroscopy are employed to study their structures and compositions. The electrochemical properties of the LiMn2O4/Li cells are also tested. The results indicate that LiMn2O4 powder composed of yolk-structured microspheres possesses remarkable high rate capability and outstanding high capacity retention not only at room temperature but also at elevated temperatures. This study may provide significant new insight into restraining the capacity fading of LiMn2O4 electrodes and the yolk-structured LiMn2O4 may be used for the next generation of lithium ion batteries.
Co-reporter:Qiao Hu, Jia-Ying Liao, Bang-Kun Zou, He-Yang Wang and Chun-Hua Chen
Journal of Materials Chemistry A 2016 - vol. 4(Issue 43) pp:NaN16804-16804
Publication Date(Web):2016/09/16
DOI:10.1039/C6TA06936C
Graphene-decorated Na3V2(PO4)3 (NVP@G) material is synthesized through an in situ catalytic process using the intermediate product component VOx as a catalyst and polyvinyl alcohol as the graphene source. NVP@G shows a superb rate performance and an ultralong cycle life.
Co-reporter:Xin Sun, Yi Jin, Chen-Yu Zhang, Jian-Wu Wen, Yu Shao, Yong Zang and Chun-Hua Chen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 41) pp:NaN17271-17271
Publication Date(Web):2014/08/26
DOI:10.1039/C4TA03828B
New electrode materials of layered oxides, Na[Ni0.4Fe0.2Mn0.4−xTix]O2, have been synthesized as positive electrodes for sodium-ion batteries. The partial substitution of Mn with Ti increases the lattice spacing without changing the lattice structure. A Na//Na[Ni0.4Fe0.2Mn0.2Ti0.2]O2 cell delivers a reversible capacity of 145 mA h g−1 with excellent long cycling performance.
