Co-reporter:Taolin Zhao, Na Zhou, Xiaoxiao Zhang, Qing Xue, Yuhua Wang, Minli Yang, Li Li, and Renjie Chen
ACS Omega September 2017? Volume 2(Issue 9) pp:5601-5601
Publication Date(Web):September 8, 2017
DOI:10.1021/acsomega.7b00689
As promising cathode materials for lithium-ion batteries (LIBs), Fe-containing Li-rich compounds of Li1+xFe0.1Ni0.15Mn0.55Oy (0 ≤ x ≤ 0.3 and 1.9 ≤ y ≤ 2.05) have been successfully synthesized by calcining the spherical precursors with appropriate amounts of lithium carbonate. The structures, morphologies, and chemical states of these compounds are characterized to better understand the corresponding electrochemical performances. With an increase of lithium content, Li1+xFe0.1Ni0.15Mn0.55Oy evolves from a complex layered-spinel structure to a layered structure. The lithium content also affects the average size and adhesion of the primary particles. At 0.1 C, sample x = 0.1 shows the highest first charge/discharge specific capacities (338.7 and 254.3 mA h g–1), the highest first Coulombic efficiency (75.1%), the lowest first irreversible capacity loss (84.4 mA h g–1), the highest reversible discharge specific capacity, and good rate capability. Notably, voltage fading can be alleviated through the adjustment of structural features. Such superior electrochemical performances of sample x = 0.1 are ascribed to the hierarchical micro-/nanostructure, the harmonious existence of complex layered-spinel phase, and the low charge-transfer resistance. An integral view of structure evolution from layered to spinel during synthetic control and cycling process is provided to broaden the performance scope of Li–Fe–Ni–Mn–O cathodes for LIBs.Topics: Adhesion; Batteries; Crystal structure; Diffraction; Electric properties; Heat treatment; Mass transfer; Mass transfer; Microstructure; Molecular structure; Nanostructures; Phase transition; Porosity; Semiconductors; Semiconductors; Spectra; Thermodynamic properties;
Co-reporter:Xiaoxiao Zhang;Qing Xue;Li Li;Ersha Fan;Feng Wu;Renjie Chen
ACS Sustainable Chemistry & Engineering December 5, 2016 Volume 4(Issue 12) pp:7041-7049
Publication Date(Web):October 10, 2016
DOI:10.1021/acssuschemeng.6b01948
The burst demand of lithium-ion batteries (LIBs) for energy storage leads to an increasing production of LIBs. The huge amount of electrode scraps produced during the industrial production cannot be overlooked. A sustainable and simple method was developed to regenerate Li(Ni1/3Co1/3Mn1/3)O2 electrode scraps as new cathodes for LIBs. Three different separation processes, including direct calcination, solvent dissolution, and basic solution dissolution, were applied to obtain the active materials. Then, a heat treatment was used to regenerate the scraps. The effects of separation methods and heat treatment temperatures were systematically investigated. The results show that the scraps regenerated with solvent dissolution and heat treatment at 800 °C deliver the highest reversible discharge capacities of 150.2 mA h g–1 at 0.2C after 100 cycles with capacity retention of 95.1%, which is comparable with commercial Li(Ni1/3Co1/3Mn1/3)O2 cathodes. When cycled at 1C, a highly reversible discharge capacity of 128.1 mA h g–1 can be obtained after 200 cycles. By contrast, scraps regenerated through a direct calcination method at 600 °C exhibit the best cycling performances, with the highest capacity retention of 96.7% after 100 cycles at 0.2C and 90.5% after 200 cycles at 1C. By characterizations of XRD, SEM, XPS, and particle size distribution analysis, the improved electrochemical performances of regenerated cathodes can be attributed to the uniform particle morphology and newly formed protective LiF composite. The simple and green regeneration process provides a novel perspective of recycling scraps from industrial production of LIBs.Keywords: Calcination; Lithium-ion batteries; Recycling; Regeneration; Scraps;
Co-reporter:Shoaib Anwer, Yongxin Huang, Jia liu, Jiajia Liu, Meng Xu, Ziheng Wang, Renjie Chen, Jiatao Zhang, and Feng Wu
ACS Applied Materials & Interfaces April 5, 2017 Volume 9(Issue 13) pp:11669-11669
Publication Date(Web):March 16, 2017
DOI:10.1021/acsami.7b01519
Low cycling stability and poor rate performance are two of the distinctive drawbacks of most electrode materials for sodium-ion batteries (SIBs). Here, inspired by natural flower structures, we take advantage of the three-dimensional (3D) hierarchical flower-like stable microstructures formed by two-dimensional (2D) nanosheets to solve these problems. By precise control of the hydrothermal synthesis conditions, a novel three-dimensional (3D) flower-like architecture consisting of 2D Na2Ti3O7 nanosheets (Na-TNSs) has been successfully synthesized. The arbitrarily arranged but closely interlinked thin nanosheets in carnation-shaped 3D Na2Ti3O7 microflowers (Na-TMFs) originate a good network of electrically conductive paths in an electrode. Thus, Na-TMFs can get electrons from all directions and be fully utilized for sodium-ion insertion and extraction reactions, which can improve sodium storage properties with enhanced rate capability and super cycling performance. Furthermore, the large specific surface area provides a high capacity, which can be ascribed to the pseudo-capacitance effect. The wettability of the electrolyte was also improved by the porous and crumpled structure. The remarkably improved cycling performance and rate capability of Na-TMFs make a captivating case for its development as an advanced anode material for SIBs.Keywords: 2D nanosheets; 3D microflowers architecture; sodium ion battery anode; sodium titanate; sodium-ion batteries;
Co-reporter:Feng Wu;Ji Qian;Weiping Wu;Yusheng Ye;Zhiguo Sun;Bin Xu
Nano Research 2017 Volume 10( Issue 2) pp:426-436
Publication Date(Web):2017 February
DOI:10.1007/s12274-016-1303-7
In this study, a boron-doped microporous carbon (BMC)/sulfur nanocomposite is synthesized and applied as a novel cathode material for advanced Li-S batteries. The cell with this cathode exhibits an ultrahigh cycling stability and rate capability. After activation, a capacity of 749.5 mAh/g was obtained on the 54th cycle at a discharge current of 3.2 A/g. After 500 cycles, capacity of 561.8 mAh/g remained (74.96% retention), with only a very small average capacity decay of 0.056%. The excellent reversibility and stability of the novel sulfur cathode can be attributed to the ability of the boron-doped microporous carbon host to both physically confine polysulfides and chemically bind these species on the host surface. Theoretical calculations confirm that boron-doped carbon is capable of significantly stronger interactions with the polysulfide species than undoped carbon, most likely as a result of the lower electronegativity of boron. We believe that this doping strategy can be extended to other metal-air batteries and fuel cells, and that it has promising potential for many different applications.
Co-reporter:Li Li, Lecai WangXiaoxiao Zhang, Qing Xue, Lei Wei, Feng Wu, Renjie Chen
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 2) pp:
Publication Date(Web):December 27, 2016
DOI:10.1021/acsami.6b13229
In this study, a hard-templating route was developed to synthesize a 3D reticular Li1.2Ni0.2Mn0.6O2 cathode material using ordered mesoporous silica as the hard template. The synthesized 3D reticular Li1.2Ni0.2Mn0.6O2 microparticles consisted of two interlaced 3D nanonetworks and a mesopore channel system. When used as the cathode material in a lithium-ion battery, the as-synthesized 3D reticular Li1.2Ni0.2Mn0.6O2 exhibited remarkably enhanced electrochemical performance, namely, superior rate capability and better cycling stability than those of its bulk counterpart. Specifically, a high discharge capacity of 195.6 mA h g–1 at 1 C with 95.6% capacity retention after 50 cycles was achieved with the 3D reticular Li1.2Ni0.2Mn0.6O2. A high discharge capacity of 135.7 mA h g–1 even at a high current of 1000 mA g–1 was also obtained. This excellent electrochemical performance of the 3D reticular Li1.2Ni0.2Mn0.6O2 is attributed to its designed structure, which provided nanoscale lithium pathways, large specific surface area, good thermal and mechanical stability, and easy access to the material center.Keywords: 3D reticular; cathode; hierarchy; Li1.2Ni0.2Mn0.6O2; lithium-ion battery;
Co-reporter:Feng Wu;Yi Xing;Jingning Lai;Xiaoxiao Zhang;Yusheng Ye;Ji Qian;Li Li;Renjie Chen
Advanced Functional Materials 2017 Volume 27(Issue 30) pp:
Publication Date(Web):2017/08/01
DOI:10.1002/adfm.201700632
The results obtained herein demonstrate that the oxygen electrode plays a critical role in determining the morphology and chemical composition of discharge products in Na–O2 batteries. Micrometer-sized cubic NaO2, film-like NaO2, and nano-sized amorphous spherical Na2-xO2 are characterized as the main discharge products on the surface of reduced graphite oxide (rGO), boron-doped rGO (B-rGO), and micrometer-sized RuO2 catalyst-coated B-rGO (m-RuO2-B-rGO) cathodes, respectively. The Na–O2 battery with m-RuO2-B-rGO as the cathode exhibits a much longer cycle life than those with the other cathodes, maintaining an unchanged capacity (0.5 mAh cm-2) after 100 cycles at a current density of 0.05 mA cm-2. A good rate capability and deep discharge–charge energy efficiency are also obtained. The excellent electrochemical performance of the battery is attributed to the effect of the micrometer-sized RuO2 catalyst. Owing to the high affinity of RuO2 for oxygen, the amorphous phase Na2-xO2 discharge product, which has good electrical contact with the RuO2 particles, can decompose completely under 3.1 V without a sudden voltage jump. Meanwhile, the micrometer-sized RuO2 catalysts also provide enough active sites and space for the reactions, and effectively minimize the occurrence of side reactions between discharge products and carbon defects.
Co-reporter:Yusheng Ye, Lili Wang, LiLi Guan, Feng Wu, Ji Qian, Teng Zhao, Xiaoxiao Zhang, Yi Xing, Jiaqing Shi, Li Li, Renjie Chen
Energy Storage Materials 2017 Volume 9(Volume 9) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.ensm.2017.07.004
Polysulfide shuttle effect and the formation of lithium metal dendrite during the discharge-charge process are two primary challenges that limit the application of lithium sulfur (Li-S) batteries. To solve them effectively, a modularly assembled interlayer was prepared by agglomerating Vulcan XC72 carbon black nanoparticles into ellipsoidal superstructures through a double Fischer esterification reaction. The MAXC interlayer can efficiently trap soluble intermediate polysulfides and provide space to store electrolyte and reaction products. More importantly, it can keep lithium anode compact and stable, enabling prolonged cell cycling. A Li/MAXC-MAXC/Li symmetrical cell sustained stable 180-cycles test and delivered only a 20 mV overpotential with a depositing/stripping capacity of 1 mA h/cm2 at 1 mA/cm2. At a high sulfur loading of approximately 5.3 mg/cm2, Li-S coin cells with the assembled MAXC interlayer maintained a high reversible capacity of 909.0 mAh/g and a high areal capacity of 4.75 mAh/cm2 after 100 cycles at 0.1 C. This multi-functional interlayer affords a viable strategy for the fabrication of high-energy-density batteries with protected metal anodes.The modular assembly of Vulcan XC72 nanoparticles to superstructure offers a predominant strategy to modify materials with new physicochemical functionalities. A modularly-assembled ellipsoidal-like superstructure was designed through a double “Fischer esterifications” and be used as an interlayer for high-areal-capacity lithium sulfur batteries. The obtained modularly assembled interlayer worked “hand-in-hand” between nanoparticles, efficiently trapped soluble intermediate polysulfides and provided the space to store electrolyte/products for long cell cycling.Download high-res image (368KB)Download full-size image
Co-reporter:Yongxin Huang, Man Xie, Jiatao Zhang, Ziheng Wang, Ying Jiang, Genhua Xiao, Shuaijie Li, Li Li, Feng Wu, Renjie Chen
Nano Energy 2017 Volume 39(Volume 39) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.nanoen.2017.07.005
•The border-rich Prussian blue particles were prepared via simple co-precipitation method.•The rhombohedral BR-FeHCF exhibited outstanding cycling stability and rate performance.•The activation process on interfaces could be observed in Prussian blue with this structure.•The advanced means were employed to investigate the reaction mechanism of sodium storage.•The pros and cons of rhombohedral phase of Prussian blue were revealed by the DFT method.The performance of a Prussian blue cathode is affected by its structure and stability. Through the inhibitor and temperature control, the border-rich structure was obtained, which provides a good contact between electrode-electrolyte interfaces and increases the transmission path for Na+ ions. In addition, the as-prepared sample with rhombohedral phase demonstrated lower band gap and lower energy barrier for Na+ ions insertion. Benefiting from the kinetics optimization, the as-prepared electrode exhibited initial capacity of 120 mA h g−1 and maintained nearly 80% after 280 cycles at current density of 100 mA g−1. This electrode also exhibited good rate performance about 60 mA h g−1 at rate of 10 C. The structural stability is also related to the formation of the passivation layer during the charge-discharge process. The optimized passivation layer not only protects the electrode form the adverse side reactions at high voltage but also delivers low interface impedance. It can be inferred that the passivation layer plays a positive role in long cycling performance. When the as-prepared electrode was measured in an electrolyte with FEC additive, it exhibited a high capacity retention rate of 79% after 500 cycles.The novel border-rich Prussian blue cathode with rhombohedral crystal structure was synthetized by the simple and environmental friendly aqueous precipitation method. Owing to the low energy barrier and stable interface for Na+ ions insertion and extraction, the electrode exhibited superior cycling stability and rate performance.Download high-res image (359KB)Download full-size image
Co-reporter:Feng Wu;Qing Xue;Li Li;Xiaoxiao Zhang;Yongxin Huang;Ersha Fan;Renjie Chen
RSC Advances (2011-Present) 2017 vol. 7(Issue 2) pp:1191-1199
Publication Date(Web):2017/01/03
DOI:10.1039/C6RA24947G
Different amounts of (NH4)3AlF6 (1, 3, and 6 wt%) are successfully coated on the surface of the layered lithium-rich cathode Li[Li0.2Ni0.2Mn0.6]O2 using a wet coating method. The morphology and structure of the as-prepared materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). It is confirmed that the (NH4)3AlF6 was uniformly coated onto the surface of the Li[Li0.2Ni0.2Mn0.6]O2. The electrochemical performance of the coated materials at room temperature and 50 °C is investigated systematically. The material coated with 3 wt% (NH4)3AlF6 exhibits the highest reversible capacity of 220.3 mA h g−1 (0.2C, 50 cycles) as well as the best cycling performance with a capacity retention of 83.4% (0.2C, 50 cycles), attributed to the suppression of unexpected surface side reactions by the protective layer of (NH4)3AlF6. Electrochemical impedance spectroscopy (EIS) analysis reveals that the lower charge transfer resistance of the coated sample may contribute to its excellent rate capability. Furthermore, the coated sample also shows enhanced cycling performance at elevated temperature owing to an improved thermal stability, confirmed by differential scanning calorimetry (DSC).
Co-reporter:Taolin Zhao;Na Zhou;Xiaoxiao Zhang;Qing Xue;Yuhua Wang;Minli Yang;Li Li;Renjie Chen
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 33) pp:22494-22501
Publication Date(Web):2017/08/23
DOI:10.1039/C7CP04092J
Surface modification is proved to be an effective strategy to improve the power density of lithium-ion batteries (LIBs) applied in electric vehicles. In this article, a protective modification layer (FeF3/LiF) is successfully deposited onto the surface of a low-cost cathode material, Li6/5[Fe1/10Ni3/20Mn11/20]O2, for realizing the improvement of ultrafast lithium storage. The reversible specific capacity and ultrahigh rate capability are effectively improved. The modified sample can achieve a higher reversible discharge specific capacity of 171.8 mA h g−1 at 0.2C. A discharge specific capacity of 150.4 mA h g−1 is delivered at 1C after 60 cycles. Even at 2C and 5C, the discharge specific capacities are still maintained at 135.7 and 124.5 mA h g−1. Notably, when charged and discharged at 20C, a discharge specific capacity of 73.4 mA h g−1 can be achieved after 200 cycles by the heterostructured Li–Fe–Ni–Mn–O cathode, almost twice that of the bare material. The good fast lithium storage capability can be ascribed to the effective suppression of interfacial side reactions, the conversion reaction from the FeF3 phase, and the harmonious coexistence of layered and spinel phases. The triple benefits from the heterostructured cathode provide a promising route for constructing advanced LIBs.
Co-reporter:Nan Chen;Yujuan Dai;Yi Xing;Lili Wang;Cui Guo;Renjie Chen;Shaojun Guo;Feng Wu
Energy & Environmental Science (2008-Present) 2017 vol. 10(Issue 7) pp:1660-1667
Publication Date(Web):2017/07/12
DOI:10.1039/C7EE00988G
The use of a rechargeable Li metal anode is one of the most favored choices for next-generation high energy density lithium batteries. Unfortunately, the growth of lithium dendrites during recharging hinders the practical application of Li metal anodes. Herein, we report a new biomimetic ionogel electrolyte with ant-nest architecture by the confinement of an ionic liquid within a chemically modified SiO2 scaffold for promoting the dendrite-free stripping/plating of Li anodes. The biomimetic ant-nest architecture not only has high ionic conductivity, but can also effectively restrain the Li dendrite growth by the spontaneous formation of a particle-rich protective layer on the lithium electrode during charge/discharge cycling. The solid-state full cells with LiNi1/3Mn1/3Co1/3O2 exhibit a very high energy density of ca. 390 W h kg−1. The as-prepared Li/Li4Ti5O12 full cells present excellent cycling stability up to 3000 cycles with excellent Coulombic efficiencies of >99.8%. The present work opens a new route for the use of the biomimetic concept for designing a new ant-nest ionogel electrolyte for developing high energy density Li metal batteries with high stability.
Co-reporter:Feng Wu, Nan Chen, Renjie Chen, Lili Wang, Li Li
Nano Energy 2017 Volume 31() pp:9-18
Publication Date(Web):January 2017
DOI:10.1016/j.nanoen.2016.10.060
•Epoxy group modified silica-supported ionogel as a novel solid-state electrolyte for lithium batteries.•The scaffold offers both a rigid framework of ordered inter-connected mesoporous and direct ion transport pathway features.•Epoxy groups grafted can promote the ionic dissociation of a lithium salt and IL.•Li/LiFePO4 and Li/Li4Ti5O12 solid-state battery displayed high cycling stability.A new solid-state ionogel electrolyte was synthesized using a silane coupling agent (SCA) that can spontaneously form a porous network to confine an ionic liquid electrolyte (ILE). We found that epoxy groups grafted on silica can promote the ionic dissociation of a lithium salt and ionic liquid. The ionogel with the optimal molar ratio (ILE/SCA=0.75) exhibited excellent thermal stability, a wide redox stability window, and ionic conductivity of 1.91×10−3 S cm−1 at 30 °C, which is higher than that of the pure IL electrolyte. The developed ionogel improved the operating temperature of batteries from room temperature to at least 90 °C. Furthermore, the good compatibility of the ionogel with a LiFePO4 cathode and Li4Ti5O12 anode indicates that it can be used as an electrolyte for full battery systems. More importantly, the SCA was employed as an organosilica precursor to synthesize a new solid-state ionogel electrolyte. This new ionogel electrolyte with high stability and capacity represents a considerable advance in solid-state electrolytes for lithium-ion batteries.
Co-reporter:Renjie Chen;Wenjie Qu;Ji Qian;Nan Chen;Yujuan Dai;Cui Guo;Yongxin Huang;Li Li;Feng Wu
Journal of Materials Chemistry A 2017 vol. 5(Issue 47) pp:24677-24685
Publication Date(Web):2017/12/05
DOI:10.1039/C7TA07653C
High safety is a long-sought-after goal in the energy storage field. We fabricate a high-safety solid-state electrolyte by in situ immobilizing ionic liquids within a nanoporous zirconia-supported matrix. This ionogel electrolyte provides a combination of the solid-like physical support and liquid-like ionic transport performance, which substantially improves the thermal stability and safety without sacrificing ionic conductivity. Both Raman spectra and density functional theory computations indicate that the zirconia skeleton interacts with the Li salts, promoting the dissociation and transport of Li+. The solid-state cell assembled with this electrolyte possesses excellent cycling performance, with a discharge capacity of 135.9 mA h g−1 after 200 cycles at 30 °C and works well in a wide operating temperature range from −10 to 90 °C. Moreover, the good compatibility and stable interface toward Li–metal anodes in a symmetrical cell demonstrates the usefulness of the electrolyte in Li–metal batteries. These results indicate that this ionogel electrolyte has great promise for application in the energy storage field because of its dramatically improved safety characteristic.
Co-reporter:Yusheng Ye;Feng Wu;Yuting Liu;Teng Zhao;Ji Qian;Yi Xing;Wanlong Li;Jiaqi Huang;Li Li;Qianming Huang;Xuedong Bai;Renjie Chen
Advanced Materials 2017 Volume 29(Issue 48) pp:
Publication Date(Web):2017/12/01
DOI:10.1002/adma.201700598
AbstractThe modular assembly of microstructures from simple nanoparticles offers a powerful strategy for creating materials with new functionalities. Such microstructures have unique physicochemical properties originating from confinement effects. Here, the modular assembly of scattered ketjen black nanoparticles into an oval-like microstructure via double “Fischer esterification,” which is a form of surface engineering used to fine-tune the materials surface characteristics, is presented. After carbonization, the oval-like carbon microstructure shows promise as a candidate sulfur host for the fabrication of thick sulfur electrodes. Indeed, a specific discharge capacity of 8.417 mAh cm−2 at 0.1 C with a high sulfur loading of 8.9 mg cm−2 is obtained. The large-scale production of advanced lithium–sulfur battery pouch cells with an energy density of 460.08 Wh kg−1@18.6 Ah is also reported. This work provides a radically different approach for tuning the performance of a variety of surfaces for energy storage materials and biological applications by reconfiguring nanoparticles into desired structures.
Co-reporter:Renjie Chen, Haiqin Zhang, Yuejiao Li, Guangbin Zhao, Chuanxiong Zhou, Meiling Cao, Man Xie, Shi Chen, Feng Wu
Solid State Ionics 2017 Volume 304(Volume 304) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.ssi.2017.03.015
•Li3V2(PO4)3 co-doped with anions and cations is synthesized using a rheological phase method.•Gd3+ and Cl− are successfully doped Li3V2(PO4)3 particles and no impurity.•Co-doped samples exhibited better electrochemical performance.•Cation–anion co-doping is a new method to improve the performance of Li3V2(PO4)3Lithium vanadium phosphate (LVP, Li3V2(PO4)3) composites co-doped with cations and anions were synthesized via a rheological phase method reaction. The effects of Gd3+–Cl− co-doping on the structure, morphology, and electrochemical performance of Li3V2(PO4)3 particles were then systematically investigated. This method of cation–anion co-doping did not change the structure of Li3V2(PO4)3. All co-doped samples exhibited better electrochemical performance than that of the undoped sample. The highest initial discharge capacity of co-doped samples was 169 mAh/g and a capacity of 72.8 mAh/g was obtained at 10C rate at 3.0–4.8 V. This synergistic mechanism of anion–cation co-doping is a promising approach to optimize the performance of Li3V2(PO4)3.
Co-reporter:Feng Wu, Rui Luo, Man Xie, Li Li, Xiaoxiao Zhang, Luzi Zhao, Jiahui Zhou, KangKang Wang, Renjie Chen
Journal of Power Sources 2017 Volume 362(Volume 362) pp:
Publication Date(Web):15 September 2017
DOI:10.1016/j.jpowsour.2017.07.050
•Porous nanocrystallite TiO2 synthesized via dilatory hydrolysis-calcination method.•C-TiO2 samples exhibited a symbiotic structure of mesoporous and macroporous.•Carbon-mediated samples show improved sodium storage capabilities.•C-TiO2 samples exhibit significantly decrease of electrochemical impedance.Porous carbon-mediated nanocrystallite anatase TiO2 composites are synthesized successfully via a simple dilatory hydrolysis-calcination method. The structural and morphological characterizations reveal that carbon-mediated TiO2 with a carbon content of 9.9 wt % (C2-TiO2) shows a combination of mesoporous and macroporous structures with a pore volume of 0.20 cm3 g−1 and surface area of 40.3 m2 g−1. Notably, C2-TiO2 delivered enhanced electrochemical performances of a high charge capacity of 259 mA h g−1 at 0.1 C and a high rate performance of 110 mA h g−1 after 150 cycles, even at 1 C. A significant decrease is also observed in the electrochemical impedance of the carbon-mediated samples, which explains superior electrochemical performance. Compared with the bare anatase TiO2 (B-TiO2), improved sodium storage capabilities of carbon-mediated samples are attributed to the participation of carbon to form a symbiotic structure with TiO2, which not only increases pore volume of the samples but serves as highly conductive network to provide a Na+ diffusion path during the insertion/de-insertion of sodium ions. All of these encouraging results suggest that carbon-mediated TiO2 has a great potential for improving sodium insertion capabilities with a facile and low-cost synthesis process.Download high-res image (193KB)Download full-size image
Co-reporter:Feng Wu, Nan Chen, Renjie Chen, Qizhen Zhu, Ji Qian, and Li Li
Chemistry of Materials 2016 Volume 28(Issue 3) pp:848
Publication Date(Web):January 5, 2016
DOI:10.1021/acs.chemmater.5b04278
Herein we present a new class of ionogel electrolyte for lithium-ion batteries, which can be prepared in either “liquid-in-solid” or “solid-in-liquid” form. The electrolytes are prepared by a nonaqueous self-assembly sol–gel process, in which ionic liquid electrolyte is immobilized within an inorganic gel. These electrolytes were found to exhibit high ionic conductivity, low electronic conductivity, and good thermal and mechanical stability. The inorganic gels weaken the interaction of anions and cations and thereby improve lithium salt dissociation and enhance transport of Li+. Also, the electrolytes are stable: no spontaneous phase separation occurs after 1 year of storage. In addition, their synthesis and shaping are very easy and cheap and form a new class of solid electrolytes, which offer exciting opportunities for preparation of in situ solid-state lithium-ion batteries. Cells with LiFePO4 cathodes and ionogel electrolyte attained a capacity of 150 mAh/g for more than 300 cycles, and even at the 2C rate, the capacity still stayed over 98 mAh/g. There are no prior reports of solid-state batteries employing ionogel electrolyte that exhibit high capacity.
Co-reporter:Feng Wu, Jianrui Liu, Li Li, Xiaoxiao Zhang, Rui Luo, Yusheng Ye, and Renjie Chen
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 35) pp:23095
Publication Date(Web):August 19, 2016
DOI:10.1021/acsami.6b07431
Composites of lithium-rich Li1.2Ni0.2Mn0.6O2 and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are synthesized through coprecipitation followed by a wet coating method. In the resulting samples, the amorphous conductive polymer films on the surface of the Li1.2Ni0.2Mn0.6O2 particles are 5–20 nm thick. The electrochemical properties of Li1.2Ni0.2Mn0.6O2 are obviously enhanced after PEDOT:PSS coating. The composite sample with an optimal 3 wt % coating exhibits rate capability and cycling properties that are better than those of Li1.2Ni0.2Mn0.6O2, with an excellent initial discharge capacity of 286.5 mA h g–1 at a current density of 0.1 C and a discharge capacity that remained at 146.9 mA h g–1 at 1 C after 100 cycles. The improved performances are ascribed to the high conductivity of the PEDOT:PSS coating layer, which can improve the conductivity of the composite material. The PEDOT:PSS layer also suppresses the formation and growth of a solid electrolyte interface. Surface modification with PEDOT:PSS is a feasible approach for improving the comprehensive properties of cathode materials.Keywords: cathode material; electrochemical properties; lithium-ion battery; PEDOT:PSS; surface modification
Co-reporter:Feng Wu, Yi Xing, Li Li, Ji Qian, Wenjie Qu, Jianguo Wen, Dean Miller, Yusheng Ye, Renjie Chen, Khalil Amine, and Jun Lu
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 36) pp:23635
Publication Date(Web):August 23, 2016
DOI:10.1021/acsami.6b05403
To improve the electrochemical performance of the high energy Li–O2 batteries, it is important to design and construct a suitable and effective oxygen-breathing cathode. Herein, a three-dimensional (3D) porous boron-doped reduction graphite oxide (B-rGO) material with a hierarchical structure has been prepared by a facile freeze-drying method. In this design, boric acid as the boron source helps to form the 3D porous structure, owing to its cross-linking and pore-forming function. This architecture facilitates the rapid oxygen diffusion and electrolyte penetration in the electrode. Meanwhile, the boron–oxygen functional groups linking to the carbon surface or edge serve as additional reaction sites to activate the ORR process. It is vital that boron atoms have been doped into the carbon lattices to greatly activate the electrons in the carbon π system, which is beneficial for fast charge under large current densities. Density functional theory calculation demonstrates that B-rGO exhibits much stronger interactions with Li5O6 clusters, so that B-rGO more effectively activates Li–O bonds to decompose Li2O2 during charge than rGO does. With B-rGO as a catalytic substrate, the Li–O2 battery achieves a high discharge capacity and excellent rate capability. Moreover, catalysts could be added into the B-rGO substrate to further lower the overpotential and enhance the cycling performance in future.Keywords: Boron-doped reduction graphite oxide; Catalytic substrate; Discharge capacity; Li−O2 batteries; Rate capability
Co-reporter:Renjie Chen, Yongxin Huang, Man Xie, Ziheng Wang, Yusheng Ye, Li Li, and Feng Wu
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 46) pp:31669
Publication Date(Web):October 31, 2016
DOI:10.1021/acsami.6b10884
The nucleation rate plays a critical role in the synthesis of Prussian blue analogs. Rapid precipitation may lead to a large number of vacancies and a large amount of interstitial water in the material, resulting in poor electrochemical performance in batteries. Hence, sodium citrate is used to compete with [Fe(CN)6]4– to slow down the coordination rates of Ni2+ and Mn2+ ions with ferrous cyanide ions. The feasibility of the experiment is also confirmed by theoretical analysis. Benefiting from stable crystal structure and the removal of interstitial water, the as-prepared Na2NixMnyFe(CN)6 sample exhibits a high reversible capacity of 150 mA h g–1. In addition, a high rate performance of 77 mA h g–1 is achieved at a current density of 1600 mA g–1. Most noteworthy, the Coulombic efficiency and specific capacity gradually increase in the first few cycles, which can be ascribed to the formation of a passivation layer on the surface of the electrode. Continuous testing in an electrolyte solution of 1 M NaPF6 dissolved in sulfone reveals that the presence of a passivation film is very important for the stability of the electrode.Keywords: cathode materials; electrolyte; kinetic activation; nucleation rate; Prussian blue analogues; sodium ion batteries
Co-reporter:Renjie Chen, Yongxin Huang, Man Xie, Qianyun Zhang, XiaoXiao Zhang, Li Li, and Feng Wu
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 25) pp:16078-16086
Publication Date(Web):June 6, 2016
DOI:10.1021/acsami.6b04151
Traditional Prussian blue (Fe4[Fe(CN)6]3) synthesized by simple rapid precipitation shows poor electrochemical performance because of the presence of vacancies occupied by coordinated water. When the precipitation rate is reduced and polyvinylpyrrolidone K-30 is added as a surface active agent, the as-prepared Prussian blue has fewer vacancies in the crystal structure than in that of traditional Prussian blue. It has a well-defined face-centered-cubic structure, which can provide large channels for Na+ insertion/extraction. The material, synthesized by slow precipitation, has an initial discharge capacity of 113 mA h g–1 and maintains 93 mA h g–1 under a current density of 50 mA g–1 after 150 charge–discharge cycles. After further optimization by a chemical etching method, the complex nanoporous structure of Prussian blue has a high Brunauer–Emmett–Teller surface area and a stable structure to achieve high specific capacity and long cycle life. Surprisingly, the electrode shows an initial discharge capacity of 115 mA h g–1 and a Coulombic efficiency of approximately 100% with capacity retention of 96% after 150 cycles. Experimental results show that Prussian blue can also be used as a cathode for Na-ion batteries.
Co-reporter:Feng Wu;Nan Chen;Renjie Chen;Qizhen Zhu;Guoqiang Tan;Li Li
Advanced Science 2016 Volume 3( Issue 1) pp:
Publication Date(Web):
DOI:10.1002/advs.201500306
The lack of suitable nonflammable electrolytes has delayed battery application in electric vehicles. A new approach to improve the safety performance for lithium battery is proposed here. This technology is based on a nanogelator-based solid electrolyte made of porous oxides and an ionic liquid. The electrolyte is fabricated using an in situ method and the porous oxides serve as a nonflammable “nanogelator” that spontaneously immobilizes the ionic liquid. The electrolyte exhibits a high liquid-like apparent ionic conductivity of 2.93 × 10−3 S cm−1 at room temperature. The results show that the nanogelator, which possess self-regulating ability, is able to immobilize imidazolium-, pyrrolidinium-, or piperidinium-based ionic liquids, simply by adjusting the ion transport channels. Our prototype batteries made of Ti-nanogeltor solid electrolyte outperform conventional lithium batteries made using ionic liquid and commercial organic liquid electrolytes.
Co-reporter:Man Xie, Yongxin Huang, Menghao Xu, Renjie Chen, Xiaoxiao Zhang, Li Li, Feng Wu
Journal of Power Sources 2016 Volume 302() pp:7-12
Publication Date(Web):20 January 2016
DOI:10.1016/j.jpowsour.2015.10.042
•A novel PBA-type cathode with titanium is used for sodium ion batteries.•The Ti2+/3+ and [Fe(CN)6]4−/3− couples provide two sites for Na+ ion storage.•An initial discharge capacity of 92.3 mAh g−1 is obtained at 50 mA g−1.A new type of Prussian blue analog, sodium titanium hexacyanoferrate, has been synthesized with good electrochemical performance using an environmentally friendly, solution precipitation method. Because of the hydrolysis reaction of titanium, it has been proved that the synthetic reaction is sensitive to heat, and the best reaction temperature is 60 °C. The resulting particles belong to a well-defined open framework with cubic structure. Because of the two sodium storage sites provided by the low-spin [Fe(CN)6]4−/3− couple and high-spin Ti3+/4+ couple, sodium titanium hexacyanoferrate exhibits a high specific capacity over 90 mAh g−1, and two pairs of clear charge/discharge platforms at 3.0 V/2.6 V and 3.4 V/3.2 V, respectively. The results show that this material can be applied as a low-cost cathode electrode with good electrochemical performance for sodium ion batteries.
Co-reporter:Yuejiao Li, Meiling Cao, Chuanxiong Zhou, Feng Wu, Shi Chen and Renjie Chen
RSC Advances 2016 vol. 6(Issue 34) pp:28624-28632
Publication Date(Web):10 Mar 2016
DOI:10.1039/C6RA03109A
We report here the synthesis of gadolinium (Gd)-doped Li3V2−xGdx(PO4)3/C (x = 0, 0.02, 0.05, 0.08, and 0.1) cathode materials using a rheological phase method. The X-ray diffraction patterns demonstrate that all the samples have the same monoclinic structure with space group P21/n. The scanning electron microscopy images show the uniform and optimized particle size of the doped samples. The Li3V1.98Gd0.02(PO4)3/C sample demonstrates the best cycling stability and discharge rate capability. Its initial discharge capacity is 110.9 mA h g−1, which can be maintained at 103.7 mA h g−1 after 80 cycles at a discharge rate of 0.2C, and the capacity retention rate is 93.5% (at 3.0–4.3 V) and 81% (at 3.0–4.8 V), while the corresponding capacity retention rates of the undoped sample are only 80.8% and 76%. According to rate performance, the Li3V1.98Gd0.02(PO4)3/C sample shows capacity retention rates of 94% (at 3.0–4.3 V) and 86% (at 3.0–4.8 V), while the pristine sample only achieves 91% and 81.6% at the 80th cycle at 0.2C. We believe that substitution with Gd3+ can reduce charge transfer resistance and improve the diffusion of Li+ ions. It is therefore useful for improving the electrochemical performance of Li3V2(PO4)3.
Co-reporter:Renjie Chen, Fan Liu, Yan Chen, Yusheng Ye, Yongxin Huang, Feng Wu, Li Li
Journal of Power Sources 2016 306() pp: 70-77
Publication Date(Web):29 February 2016
DOI:10.1016/j.jpowsour.2015.10.105
•The SN-based electrolytes show better thermal stability and wider electrochemical window.•The effects of SN on the electrochemical performances of LIBs have been investigated.•The 1 wt % SN-containing electrolyte improves cycle performance of LNMO batteries.Succinonitrile (SN) has been used as functional additive to improve the thermal stability and broaden the oxidation electrochemical window of commercial electrolyte 1 M LiPF6/EC/DEC (1:1, by volume) for high-voltage LIBs (cathode: Li1.2Ni0.2Mn0.6O2, anode: Li). 1 wt % SN-based electrolyte showed a wide electrochemical oxidation window of 5.4 V vs Li+/Li and excellent thermal stability demonstrated by thermogravimetry (TG) and X-ray photoelectron spectroscopy (XPS), as well as theoretical analysis according to molecular orbital theory. The LNMO (Li1.2Ni0.2Mn0.6O2) battery with 1 wt % SN-based electrolyte showed better cyclability and capacity retention when charged to higher cut-off voltage. The improved battery performance is mainly attributed to the formation of uniform cathode electrolyte interface (CEI) formed by interfacial reactions between the LNMO cathode and electrolyte. The outcome of this work and the continuous research on this subject can generate critical knowledge for designing thermal stability electrolytes for large format lithium-ion batteries.The excellent electrochemical performances of Li/Li1.2Ni0.2Mn0.6O2 half-cell with 1wt % SN-based electrolyte are attributed to the multifunctional SN additives and the formation of uniform cathode electrolyte interface.
Co-reporter:Feng Wu, Yusheng Ye, Renjie Chen, Ji Qian, Teng Zhao, Li Li, and Wenhui Li
Nano Letters 2015 Volume 15(Issue 11) pp:7431-7439
Publication Date(Web):October 26, 2015
DOI:10.1021/acs.nanolett.5b02864
Rechargeable lithium–sulfur (Li–S) batteries are attractive candidates for energy storage devices because they have five times the theoretical energy storage of state-of-the-art Li-ion batteries. The main problems plaguing Li–S batteries are poor cycle life and limited rate capability, caused by the insulating nature of S and the shuttle effect associated with the dissolution of intermediate lithium polysulfides. Here, we report the use of biocell-inspired polydopamine (PD) as a coating agent on both the cathode and separator to address these problems (the “systematic effects”). The PD-modified cathode and separator play key roles in facilitating ion diffusion and keeping the cathode structure stable, leading to uniform lithium deposition and a solid electrolyte interphase. As a result, an ultralong cycle performance of more than 3000 cycles, with a capacity fade of only 0.018% per cycle, was achieved at 2 C. It is believed that the systematic modification of the cathode and separator for Li–S batteries is a new strategy for practical applications.
Co-reporter:Feng Wu, Qizhen Zhu, Renjie Chen, Nan Chen, Yan Chen and Li Li
Chemical Science 2015 vol. 6(Issue 12) pp:7274-7283
Publication Date(Web):18 Sep 2015
DOI:10.1039/C5SC02761F
Lithium-ion batteries have been attracting much attention which enables the revolution of wireless global communication. Ionic liquids are regarded as promising candidates for lithium-ion battery electrolytes because they can overcome the limitations of high operating temperatures and flammability concerns of traditional electrolytes. However, at low temperatures they suffer from low ionic conductivity and phase transition. In this paper mixed electrolyte systems are described based on N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)-imide (Pyr1,2O1TFSI) and lithium difluoro(oxalate)borate (LiODFB) lithium salt, with ethylene sulphite (ES) or dimethyl sulphite (DMS) as a cosolvent. The mixed electrolyte system exhibits good ion transport properties (a conductivity of 8.163 mS cm−1), a wide electrochemical window (5.2 V), non-flammability, the ability to form films to protect the anode and a large operating temperature range (−40 °C to 60 °C). We compare the performance and function of the new mixed electrolyte system with a variety of ionic liquid/cosolvent electrolyte systems developed in previous studies. The ring-chain synergy takes advantage of the availability of both high permittivities based on the ring-like components and low viscosities based on the chain-like components in the mixed electrolyte system and causes the electrolyte to exhibit a good overall performance in safety, ion transport and compatibility with electrodes.
Co-reporter:Feng Wu, Xiaoxiao Zhang, Taolin Zhao, Renjie Chen, Yusheng Ye, Man Xie and Li Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 34) pp:17620-17626
Publication Date(Web):21 Jul 2015
DOI:10.1039/C5TA04673D
Hierarchical mesoporous/macroporous Co3O4 ultrathin nanosheets were synthesized as free-standing catalysts for rechargeable Li–O2 batteries. The Co3O4 nanosheets were directly grown on nickel foam through a simple hydrothermal reaction, followed by a calcination process. The impact of solvents used in the hydrothermal reaction on the morphology of catalysts has been investigated. The results showed that the prepared Co3O4 catalyst synthesized with ethylene glycol and deionized water (1:1 in volume) presented a much better electrochemical performance with a capacity of 11882 mA h g−1 under a current density of 100 mA g−1 during the initial discharge and good cycling stability (more than 80 cycles at 200 mA g−1 with the capacity limited to 500 mA h g−1). Meanwhile, the charge potential was significantly reduced to ca. 3.7 V. It is interesting to find that the morphology of the discharge product, Li2O2 could be changed by controlling the shape of catalysts. The impacts of the hierarchical mesoporous/macroporous nanosheet structure on the performance of Li–O2 batteries have been discussed.
Co-reporter:Renjie Chen, Yan Chen, Lu Zhu, Qizhen Zhu, Feng Wu and Li Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 12) pp:6366-6372
Publication Date(Web):06 Feb 2015
DOI:10.1039/C5TA00818B
Ionic liquid-based electrolytes are widely used in lithium-ion batteries to obtain wide electrochemical windows and fewer safety concerns. In order to enhance the energy density and rate capability, lithium difluoro(oxalato)borate (LiODFB) and dimethyl sulfite (DMS) have been introduced into N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI)-based electrolytes as lithium salt and co-solvent, respectively. The binary LiODFB–PYR14TFSI/DMS (7:3, m/m) electrolyte has been prepared and investigated. FTIR analysis has demonstrated that stretching of the functional groups CO and O–S–O plays a vital role in the solvation of the designed electrolyte, and elevate the ionic conductivity of the electrolyte by an order of magnitude. In comparison to when a LiTFSI–PYR14TFSI/DMS (7:3, m/m) electrolyte is used, Li/MCMB half-cells containing the novel electrolyte achieve excellent electrochemical performances, even superior to those of conventional organic electrolytes, maintaining a discharge capacity and coloumbic efficiency of 273.2 mA h g−1 and 99%, respectively, after 80 cycles. This tremendous improvement is ascribed to the joint reductive composition of DMS and LiODFB, resulting in the formation of a more robust solid-electrolyte interface (SEI) film at the MCMB electrode. Besides, the discharge capacity of Li/LiFePO4 half-cells with the LiODFB-based electrolyte could still reach up to 139 mA h g−1 at a rate of 1 C. All those characteristics make it a promising electrolyte material for safe and high-performance lithium-ion batteries.
Co-reporter:Renjie Chen, Teng Zhao and Feng Wu
Chemical Communications 2015 vol. 51(Issue 1) pp:18-33
Publication Date(Web):06 Aug 2014
DOI:10.1039/C4CC05109B
In terms of sustainable development and environmental issues, the design and fabrication of efficient energy storage devices will be more critical in the future than at any time in the past. Li–S batteries are promising candidates for such a purpose due to their high specific capacity and low environmental impact. This review has systematically retraced the advances in the field of Li–S batteries over the past half century and highlighted the main breakthroughs in a number of areas, covering the mechanism determination, cathode engineering, theoretical simulation, and electrolyte tailoring and anode protection. Furthermore, we discuss the remaining challenges towards their practical application. It is expected that Li–S batteries with 3D inter-connected or conformal assemblies will surpass new horizons in the coming years.
Co-reporter:Man Xie, Rui Luo, Renjie Chen, Feng Wu, Taolin Zhao, Qiuyan Wang, and Li Li
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 20) pp:10779
Publication Date(Web):May 1, 2015
DOI:10.1021/acsami.5b01061
Lithium manganese silicate (Li2MnSiO4) is an attractive cathode material with a potential capacity above 300 mA h g–1 if both lithium ions can be extracted reversibly. Two drawbacks of low electronic conductivity and structural collapse could be overcome by a conductive surface coating and a porous structure. Porous morphology with inner mesopores offers larger surface area and shorter ions diffusion pathways and also buffers the volume changes during lithium insertion and extraction. In this paper, mesoporous Li2MnSiO4 (M-Li2MnSiO4) prepared using MCM-41 as template through a hydrothermal route is compared to a sample of bulk Li2MnSiO4 (B-Li2MnSiO4) using silica as template under the same conditions. Also, in situ carbon coating technique was used to improve the electronic conductivity of M-Li2MnSiO4. The physical properties of these cathode materials were further characterized by SEM, XRD, FTIR, and N2 adsorption–desorption. It is shown that M-Li2MnSiO4 exhibits porous structure with pore sizes distributed in the range 9–12 nm, and when used as cathode electrode material, M-Li2MnSiO4 exhibits enhanced specific discharge capacity of 193 mA h g–1 at a constant current of 20 mA g–1 compared with 120.1 mA h g–1 of B-Li2MnSiO4. This is attributed to the porous structure which allows the electrolyte to penetrate into the particles easily. And carbon-coated M-Li2MnSiO4 shows smaller charge transfer resistance and higher capacity of 217 mA h g–1 because carbon coating retains the porous structure and enhances the electrical conductivity.Keywords: carbon coating; lithium ion batteries; M-Li2MnSiO4; porous structure; template-assisted;
Co-reporter:Feng Wu, Xiaoxiao Zhang, Taolin Zhao, Li Li, Man Xie, and Renjie Chen
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 6) pp:3773
Publication Date(Web):January 28, 2015
DOI:10.1021/am508579r
Layered Li-rich, Fe- and Mn-based cathode material, Li[Li0.2Fe0.1Ni0.15Mn0.55]O2, has been successfully synthesized by a coprecipitation method and further modified with different coating amounts of AlPO4 (3, 5, and 7 wt %). The effects of AlPO4 coating on the structure, morphology and electrochemical properties of these materials are investigated systematically. XRD results show that the pristine sample is obtained with typical Li-rich layered structure and trace amount of Li3PO4 phase are observed for the coated samples. The morphology observations reveal that all the samples show spherical particles (3–4 μm in diameter) with hierarchical structure, composed of nanoplates and nanoparticles. XPS analysis confirms the existence of AlPO4 and Li3PO4 phases at the surface. The electrochemical performance results indicate that the sample coated with 5 wt % AlPO4 exhibits the highest reversible capacity (220.4 mA h g–1 after 50 cycles at 0.1C), best cycling performance (capacity retention of 74.4% after 50 cycles at 0.1C) and rate capability (175.3 mA h g–1 at 1C, and 120.2 mA h g–1 at 10C after 100 cycles) among all the samples. Cycle voltammograms show good reversibility of the coated samples. EIS analysis reveals that charge transfer resistance after coating is much lower than that of the pristine sample. The excellent electrochemical performances can be attributed to the effects of multifunctional AlPO4 coating layer, including the suppression of surface side reaction and oxygen vacancies diffusion, the acceleration of lithium ions transport as well as the lower electrochemical resistance. Our research provides a new insight of surface modification on low-cost Li-rich material to achieve high energy as the next-generation cathode of lithium-ion batteries.Keywords: AlPO4 coating; iron−manganese oxide; lithium-ion battery; lithium-rich cathode
Co-reporter:Li Li, Lecai Wang, Xiaoxiao Zhang, Man Xie, Feng Wu, and Renjie Chen
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 39) pp:21939
Publication Date(Web):September 15, 2015
DOI:10.1021/acsami.5b06584
In this study, a facile nanoetching-template route is developed to synthesize porous nanomicrohierarchical LiNi1/3Co1/3Mn1/3O2 microspheres with diameters below 1.5 μm, using porous CoMnO3 binary oxide microspheres as the template. The unique morphology of CoMnO3 template originates from the contraction effect during the oxidative decomposition of Ca0.2Mn0.4Co0.4CO3 precursors and is further improved by selectively removing calcium carbonate with a nanoetching process after calcination. The as-synthesized LiNi1/3Co1/3Mn1/3O2 microsphere, composed of numerous primary particles and pores with size of dozens of nanometers, illustrates a well-assembled porous nanomicrohierarchical structure. When used as the cathode material for lithium-ion batteries, the as-synthesized microspheres exhibit remarkably enhanced electrochemical performances with higher capacity, excellent cycling stability, and better rate capability, compared with the bulk counterpart. Specifically, hierarchical LiNi1/3Co1/3Mn1/3O2 achieves a high discharge capacity of 159.6 mA h g–1 at 0.2 C with 98.7% capacity retention after 75 cycles and 133.2 mA h g–1 at 1 C with 90% capacity retention after 100 cycles. A high discharge capacity of 135.5 mA h g–1 even at a high current of 750 mA g–1 (5 C) is also achieved. The nanoetching-template method can provide a general approach to improve cycling stability and rate capability of high capacity cathode materials for lithium-ion batteries.Keywords: cathode; lithium-ion battery; mesopores; nanoetching-template; nanomicrohierarchical
Co-reporter:Feng Wu, Qizhen Zhu, Renjie Chen, Nan Chen, Yan Chen, Yusheng Ye, Ji Qian, Li Li
Journal of Power Sources 2015 Volume 296() pp:10-17
Publication Date(Web):20 November 2015
DOI:10.1016/j.jpowsour.2015.07.033
•We prepare an ionic liquid-based electrolyte with binary lithium salts for Li–S batteries.•Various molar ratios of electrolyte systems were thoroughly investigated.•The novel electrolytes show excellent discharge capacity and cycling performance.•The SEI-forming ability of LiODFB protect Li anode from suffering lithium dendrites.Rechargeable Li–S batteries have suffered several technical obstacles, such as rapid capacity fading and low coulombic efficiency. To overcome these problems, we design new electrolytes containing N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)-imide (Pyr1,2O1TFSI) and tri(ethylene glycol)dimethyl ether (TEGDME) in mass ratio of 7:3. Moreover, Lithium difluoro(oxalate)borate (LiODFB) is introduced for the modification. Although the addition of LiODFB as additive lead to extremely high viscosity of electrolyte and inferior performance of the cells, the electrolyte containing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 0.84 nm) and LiODFB (0.60 nm) mixture with a total molar concentration of 0.4 mol kg−1 as binary lithium salt shows excellent electrochemical performance. The Pyr1,2O1TFSI/TEGDME electrolyte with LiTFSI/LiODFB binary lithium salts in mole ratio of 6:4 is obtained after optimizing ratio. The Li–S cells containing this electrolyte system show excellent capacity and cycle performance, whose initial discharge capacity is 1264.4 mAh g−1, and retains 911.4 mAh g−1 after 50 cycles with the coulombic efficiency more than 95%. It can be attributed the solid-electrolyte interphase (SEI)-forming ability of LiODFB which protect Li anode from suffering lithium dendrites and prevent the shuttle phenomenon. The novel electrolytes provide good cycling stability and high coulombic efficiency for the Li–S batteries, which is suggested as a promising electrolyte for Li–S batteries.The Pyr1,2O1TFSI/TEGDME electrolyte with LiTFSI/LiODFB binary lithium salts in the optimum mole ratio of 6:4 synergistically afford acceptable capacity and coulombic efficiency for Li–S batteries. One of the reasons is that LiODFB can facilitate the SEI layer formation on the surface of the electrodes which prevents the shuttle phenomenon and protects the Li anode in the Li–S batteries.
Co-reporter:Man Xie, Menghao Xu, Yongxin Huang, Renjie Chen, Xiaoxiao Zhang, Li Li, Feng Wu
Electrochemistry Communications 2015 Volume 59() pp:91-94
Publication Date(Web):October 2015
DOI:10.1016/j.elecom.2015.07.014
•Na2NixCo1 − xFe(CN)6 was used as a new type cathode for sodium ion batteries.•The appropriate proportion of nickel and cobalt is 4:6.•PBN0.4C0.6 exhibits a discharge capacity of 91.8 mAh g− 1 at 50 mA g− 1.•Significantly increased rate performance with 68.5 mAh g− 1 at 800 mA g− 1A new class of Prussian blue analogs, Na2NixCo1 − xFe(CN)6 (0 ≤ x ≤ 1) with various nickel-to-cobalt ratios (from pure nickel to pure cobalt with a 10% increase in Co content for each sample) was prepared and tested as cathode materials for sodium ion batteries. The Na2Ni0.4Co0.6Fe(CN)6 sample showed the best electrochemical performance, with an initial discharge capacity of 90 mA h g− 1 and reversible capacity of 80 mA h g− 1 after 100 cycles. Even at a higher rate of 800 mA g− 1, a good initial discharge capacity of 74 mA h g− 1 was obtained.
Co-reporter:Feng Wu, Qizhen Zhu, Renjie Chen, Nan Chen, Yan Chen, Li Li
Electrochimica Acta 2015 Volume 184() pp:356-363
Publication Date(Web):1 December 2015
DOI:10.1016/j.electacta.2015.10.109
Lithium-sulfur battery, one of the most promising rechargeable electrochemical systems, has suffered several technical obstacles, such as rapid capacity fading and safety concerns. The former mainly result from the “shuttle” mechanism due to the dissolution of the reaction intermediates lithium polysulfides; the latter can be attributed to the highly flammable electrolyte. To overcome these problems, we prepared a series of Li-S battery electrolytes based on ionic liquid of (N-methoxyethyl-N-methylpyrrolidinium bis (trifluoromethanesulfonyl)-imide, P1,2O1TFSI) and cosolvents of tris(ethylene glycol) dimethyl ether (TEGDME) with lithium bis (trifluoromethanesulfonyl)-imide (LiTFSI) as lithium salt. The electrolyte provides a counterbalance between shuttle suppression and solubility of lithium polysulfides by combining the ionic liquid and TEGDME in the optimum mass ratio of 7:3. The 0.4 mol kg−1 LiTFSI-P1,2O1TFSI/(30wt%) TEGDME electrolyte exhibits good ion transport (room temperature ionic conductivity of 4.303 mS cm−1) and safety (self-extinguishing time of 4.8 s g−1). The Li-S batteries with the 0.4 mol kg−1 LiTFSI-P1,2O1TFSI/(30wt%) TEGDME electrolyte possess the high discharge capacity (1212.8 mAh g−1 for the first cycle at 0.1C), excellent rate capability (886.5 mAh g−1 at 1C) and good cycling performance (capacity retention of 93.3% after 100 cycles with the coulombic efficiency above 95% at 1C). Moreover, this electrolyte could operate at 80 °C in Li-S cells indicating the excellent high temperature performance. This research gives a new insight for designing ionic liquid-based electrolyte for the safe Li-S batteries with high performance.The Li-S batteries containing electrolyte with a counterbalance between nonflammable P1,2O1TFSI suppressing shuttle and TEGDME providing high capacities in the optimum mass ratio of 7:3 exhibit safety, improved rate behavior and good high temperature performance.
Co-reporter:Feng Wu, Wenhui Li, Lili Guan, Yusheng Ye, Ji Qian, Xiaoguang Yang, Yuhong Xu and Renjie Chen
RSC Advances 2015 vol. 5(Issue 114) pp:94479-94485
Publication Date(Web):26 Oct 2015
DOI:10.1039/C5RA19348F
Lithium–sulfur (Li–S) batteries with high theoretical capacities and low cost are a strong candidate for future energy storage, but their development is hindered by many shortcomings, such as high-rate capacity decay due to the “shuttle effect”. Herein, we increase the capacity retention and cycle life of the Li–S battery through the addition of an interlayer made of polypyrrole (PPy)-treated carbon paper (CP) in a Li–S battery. We first quantitatively investigate the effect of the thickness of the carbon paper and then optimize a novel interlayer prepared by using PPy adhered to the carbon paper. The results show that 300 μm CP is the best choice among the three thicknesses. The CP-300 samples deliver a reversible capacity of 490 mAh g−1 after 200 cycles with a 0.5 C rate and show the best rate performance. Because of the porous structure and conductivity of the as-prepared PPy interlayer, the battery incorporating the PPy interlayer exhibits more excellent cycle performance and better rate performance than the CP batteries. Surprisingly, the PPy-coated CP-200 battery displays a reversible capacity of 555 mAh g−1 after 200 cycles with a 0.5 C rate. This feasible way to modify a carbon paper interlayer may have promising prospects in the Li–S battery field.
Co-reporter:Taolin Zhao, Li Li, Renjie Chen, Huiming Wu, Xiaoxiao Zhang, Shi Chen, Man Xie, Feng Wu, Jun Lu, Khalil Amine
Nano Energy 2015 Volume 15() pp:164-176
Publication Date(Web):July 2015
DOI:10.1016/j.nanoen.2015.04.013
•Hierarchical cathode Li[Li0.2Ni0.2Mn0.6]O2 was coated with LiF/FeF3 layer.•A combination of conversion reaction and extraction/insertion reaction was explored.•LiF/FeF3 layer with different coating thickness exhibited respective merits.•Superior rate performance was obtained with an ultrathin layer.•A significantly improved cycling performance was realized with a thicker layer.Advanced lithium-ion batteries for renewable energy storage applications have become a major research interest in recent years. Much better performance can be realized by improvements in the material surface design, especially for the cathode materials. Here, we present a new design for a surface protective layer formed via a facile aqueous solution process in which a nano-architectured layer of LiF/FeF3 is epitaxially grown on bulk hierarchical Li-rich cathode Li[Li0.2Ni0.2Mn0.6]O2. Coin cell tests of this material in the voltage range of 2–4.8 V indicated a high reversible capacity (260.1 mA h g−1 at 0.1 C), superior rate performance (129.9 mA h g−1 at 20 C), and excellent capacity retention. Differential scanning calorimetry showed good thermal stability. The enhanced capacity and cycling stability are attributed to the suppression of interfacial side reactions as well as the conversion reaction resulting from the introduction of LiF/FeF3 as a surface protective layer.
Co-reporter:Feng Wu, Ji Qian, Renjie Chen, Teng Zhao, Rui Xu, Yusheng Ye, Wenhui Li, Li Li, Jun Lu, Khalil Amine
Nano Energy 2015 Volume 12() pp:742-749
Publication Date(Web):March 2015
DOI:10.1016/j.nanoen.2014.12.042
Co-reporter:Feng Wu, Qizhen Zhu, Renjie Chen, Nan Chen, Yan Chen, Li Li
Nano Energy 2015 Volume 13() pp:546-553
Publication Date(Web):April 2015
DOI:10.1016/j.nanoen.2015.03.042
•The electrolyte consists of ionic liquid and sulfone with difluoro(oxalate)borate (LiODFB) exhibit good compatibility with high voltage cathodes and carbonaceous anodes in lithium-ion batteries.•The electrodes exhibit high specific capacity and good cycling performance.•LiODFB can be preferably oxidized during charging and reduced in discharging process with products piling up to form the SEI layers on the surfaces of electrodes.The electrolyte based on ionic liquid and sulfone with lithium difluoro(oxalate)borate (LiODFB) was prepared for high voltage lithium-ion battery because of its high conductivity, wide electrochemical window and non-flammability. High voltage cathodes and carbonaceous anodes were used as electrodes to evaluate the electrochemical properties of cells with the electrolyte. Li/Li1.2Ni0.2Mn0.6O2 and Li/MCMB cells with LiODFB–PP14TFSI/TMS exhibit good cycling performance, which retain capacities of above 220 mA h g−1 and 338.6 mA h g−1 after 50 cycles, respectively. The solid-electrolyte interphase (SEI) formation were characterized by ab initio simulations and X-ray photoelectron spectroscopy. The results indicate that LiODFB can be preferably oxidized during charging and reduced during discharging process. The nano reaction products pile up to form the SEI layers on the surfaces of electrodes. The SEI layers which prevent the electrolyte and electrode materials ensure the good electrochemical performance of the cells.
Co-reporter:Feng Wu, Guoqiang Tan, Jun Lu, Renjie Chen, Li Li, and Khalil Amine
Nano Letters 2014 Volume 14(Issue 3) pp:1281-1287
Publication Date(Web):February 14, 2014
DOI:10.1021/nl404215h
The lithium-ion battery, a major renewable power source, has been widely applied in portable electronic devices and extended to hybrid electric vehicles and all-electric vehicles. One of the main issues for the transportation application is the need to develop high-performance cathode materials. Here we report a novel nanostructured cathode material based on air-stable polycrystalline Li0.28Co0.29Ni0.30Mn0.20O2 thin film with lithium deficiency for high-energy density lithium-ion batteries. This film is prepared via a method combining radio frequency magnetron sputtering and annealing using a crystalline and stoichiometric LiCo1/3Ni1/3Mn1/3O2 target. This lithium-deficient Li0.28Co0.29Ni0.30Mn0.20O2 thin film has a polycrystalline nanostructure, high tap density, and higher energy and power density compared to the initial stoichiometric LiCo1/3Ni1/3Mn1/3O2. Such a material is a promising cathode candidate for high-energy lithium-ion batteries, especially thin-film batteries.
Co-reporter:Renjie Chen, Teng Zhao, Weiping Wu, Feng Wu, Li Li, Ji Qian, Rui Xu, Huiming Wu, Hassan M. Albishri, A. S. Al-Bogami, Deia Abd El-Hady, Jun Lu, and Khalil Amine
Nano Letters 2014 Volume 14(Issue 10) pp:5899-5904
Publication Date(Web):August 27, 2014
DOI:10.1021/nl502848z
Transition metal dichalcogenides (TMD), analogue of graphene, could form various dimensionalities. Similar to carbon, one-dimensional (1D) nanotube of TMD materials has wide application in hydrogen storage, Li-ion batteries, and supercapacitors due to their unique structure and properties. Here we demonstrate the feasibility of tungsten disulfide nanotubes (WS2-NTs)/graphene (GS) sandwich-type architecture as anode for lithium-ion batteries for the first time. The graphene-based hierarchical architecture plays vital roles in achieving fast electron/ion transfer, thus leading to good electrochemical performance. When evaluated as anode, WS2–NTs/GS hybrid could maintain a capacity of 318.6 mA/g over 500 cycles at a current density of 1A/g. Besides, the hybrid anode does not require any additional polymetric binder, conductive additives, or a separate metal current-collector. The relatively high density of this hybrid is beneficial for high capacity per unit volume. Those characteristics make it a potential anode material for light and high-performance lithium-ion batteries.
Co-reporter:Feng Wu, Ji Qian, Renjie Chen, Jun Lu, Li Li, Huiming Wu, Junzheng Chen, Teng Zhao, Yusheng Ye, and Khalil Amine
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 17) pp:15542
Publication Date(Web):August 6, 2014
DOI:10.1021/am504345s
Lithium oxalyldifluoroborate (LiODFB) has been investigated as an organic electrolyte additive to improve the cycling performance of Li–S batteries. Cell test results demonstrate that an appropriate amount of LiODFB added into the electrolyte leads to a high Coulombic efficiency. Analyses by energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and the density functional theory showed that LiODFB promotes the formation of a LiF-rich passivation layer on the lithium metal surface, which not only blocks the polysulfide shuttle, but also stabilizes the lithium surface.Keywords: electrochemistry; electrolyte; LiODFB; lithium anode; lithium−sulfur batteries; passivation layer
Co-reporter:Man Xie, Rui Luo, Jun Lu, Renjie Chen, Feng Wu, Xiaoming Wang, Chun Zhan, Huiming Wu, Hassan M. Albishri, Abdullah S. Al-Bogami, Deia Abd El-Hady, and Khalil Amine
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 19) pp:17176
Publication Date(Web):September 5, 2014
DOI:10.1021/am5049114
Research on sodium batteries has made a comeback because of concern regarding the limited resources and cost of lithium for Li-ion batteries. From the standpoint of electrochemistry and economics, Mn- or Fe-based layered transition metal oxides should be the most suitable cathode candidates for affordable sodium batteries. Herein, this paper reports a novel cathode material, layered Na1+x(Fey/2Niy/2Mn1–y)1–xO2 (x = 0.1–0.5), synthesized through a facile coprecipitation process combined with subsequent calcination. For such cathode material calcined at 800 °C for 20 h, the Na/Na1+x(Fey/2Niy/2Mn1–y)1–xO2 (x = 0.4) electrode exhibited a good capacity of 99.1 mAh g–1 (cycled at 1.5–4.0 V) and capacity retention over 87% after 50 cycles. Optimization of this material would make layered transition metal oxides a strong candidate for the Na-ion battery cathode.Keywords: calcination; cathode; layered structure; Na-ion batteries; transition-metal oxide
Co-reporter:Li Li, Xiaoxiao Zhang, Renjie Chen, Taolin Zhao, Jun Lu, Feng Wu, Khalil Amine
Journal of Power Sources 2014 Volume 249() pp:28-34
Publication Date(Web):1 March 2014
DOI:10.1016/j.jpowsour.2013.10.092
•Re-synthesis of Li-rich cathode material Li1.2Co0.13Ni0.13Mn0.54O2 from spent LIBs.•Leaching solution from spent LIBs is successfully used as a source of Co and Li.•The re-synthesized material delivers a high initial discharge capacity of 258.8 mAh g−1.•The high capacity retention of 87% can be obtained after 50 cycles.•This technology can reduce the cost and realize cyclic utilization of spent LIBs.Li-rich layered oxide Li1.2Co0.13Ni0.13Mn0.54O2 has been successfully re-synthesized using the ascorbic acid leaching solution of spent lithium-ion batteries as the raw materials. A combination of oxalic acid co-precipitation, hydrothermal and calcination processes was applied to synthesize this material. For comparison, a fresh sample with the same composition has been also synthesized from the commercial raw materials using the same method. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements are carried out to characterize these samples. XRD results indicate that both samples have the layered α-NaFeO2 structures with a space group of R3¯m. No other crystalline phase was detected by XRD. The electrochemical results show that the re-synthesized and fresh-synthesized sample can deliver discharge capacities as high as 258.8 and 264.2 mAh g−1 at the first cycle, respectively. After 50 cycles, discharge capacities of 225.1 and 228 mAh g−1 can be obtained with capacity retention of 87.0 and 86.3%, respectively. This study suggests that the leaching solution from spent lithium ion batteries can be recycled to synthesize Li-rich cathode materials with good electrochemical performance.
Co-reporter:Li Li, Longyu Zhai, Xiaoxiao Zhang, Jun Lu, Renjie Chen, Feng Wu, Khalil Amine
Journal of Power Sources 2014 Volume 262() pp:380-385
Publication Date(Web):15 September 2014
DOI:10.1016/j.jpowsour.2014.04.013
•Ultrasonic-assisted leaching process is used to recover spent LiCoO2 material.•Citric acid works better than HCl and H2SO4 inorganic acids in the leaching process.•The mechanism of ultrasonic cavitation on leaching process is explained.•The recovery process is environmental-friendly, less costly and highly efficient.The anticipated significant use of lithium-ion batteries (LIBs) for energy storage applications in electric grid modernization and vehicle electrification shall generate a large quantity of solid waste that could become potential environmental hazards and waste natural resources. Recycling of the major components from spent LIBs is, therefore, considered desirable to prevent environmental pollution and to recycle valuable metals. This study reports on the application of ultrasonic-assisted technology to the leaching of cobalt and lithium from the cathode active materials of spent LIBs. Three acids were tested for the leaching process: two inorganic acids (H2SO4 and HCl) and one organic acid (citric acid, C6H8O7·H2O). The results show that the leaching of Co and Li is more efficient with citric acid than with the two inorganic acids. More than 96% Co and nearly 100% Li were recovered from spent LIBs. The optimal leaching conditions were 0.5 M citric acid with 0.55 M H2O2, a solid-to-liquid ratio of 25 g L−1, a temperature of 60 °C, leaching time of 5 h, and ultrasonic power of 90 W. The high leaching efficiency is mainly ascribed to the unique cavitation action of the ultrasonic waves. This ultrasonic-assisted leaching process with organic acid is not only effective but also environmentally friendly.
Co-reporter:Li Li, Wenjie Qu, Fang Liu, Taolin Zhao, Xiaoxiao Zhang, Renjie Chen, Feng Wu
Applied Surface Science 2014 Volume 315() pp:59-65
Publication Date(Web):1 October 2014
DOI:10.1016/j.apsusc.2014.07.090
Highlights
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A method is designed to synthesize a λ-MnO2 ion-sieve for lithium ions adsorption.
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Ultrasonic treatment with acid is highly efficient for lithium ions extraction.
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Surface modification by CeO2 is used to improve the adsorption capacity.
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A 0.5 wt.% CeO2-coated ion-sieve shows the best adsorption properties.
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λ-MnO2 ion-sieves are promising for recovering scarce lithium resources.
Co-reporter:Feng Wu, Qizhen Zhu, Li Li, Renjie Chen and Shi Chen
Journal of Materials Chemistry A 2013 vol. 1(Issue 11) pp:3659-3666
Publication Date(Web):10 Jan 2013
DOI:10.1039/C3TA01182H
A new binary electrolyte containing tetramethylene sulfone (TMS) and hexamethylene diisocyanate (HDI) with lithium difluoro(oxalate)borate (LiODFB) as the lithium salt has been prepared and investigated for physicochemical properties. A linear relationship between the frontier molecular orbital energies and the oxidation/reduction potentials is preliminarily confirmed. Compared to the pure TMS electrolyte, a mixture of TMS and HDI exhibits a wider electrochemical stability window, better wettability and an improved low temperature performance. Combined with the mixed electrolyte, LiCoO2 and LiNi1/3Mn1/3Co1/3O2 cathode materials show specific capacities of nearly 134.5 mA h g−1 and 168.3 mA h g−1 after 50 cycles, respectively, which is superior to those containing the traditional electrolyte. Furthermore, the composite electrolyte exhibits a good compatibility with the high voltage LiNi0.5Mn1.5O4 cathode material which has a specific capacity close to 120 mA h g−1 after 50 cycles. The enhanced battery performance is mainly due to HDI, which has a high oxidation potential (5.2 V), good wettability, a low melting point and an outstanding ability to form effective solid electrolyte interface layers. In addition, LiODFB makes a contribution to the compatibility of the electrolyte due to its passivation toward aluminum, its high solubility and its ability to support reversible metallic lithium cycling. All of the properties above indicate that the LiODFB/HDI/TMS mixed electrolyte is a promising material and can have applications in the field of lithium batteries.
Co-reporter:Jin Xiang, Feng Wu, Renjie Chen, Li Li, Huigen Yu
Journal of Power Sources 2013 Volume 233() pp:115-120
Publication Date(Web):1 July 2013
DOI:10.1016/j.jpowsour.2013.01.123
Novel binary electrolytes based on ionic liquid (N-butyl-methyl piperidinium bis(trifluoro-methylsulfonyl)imide, PP14-TFSI) and sulfone (tetramethylene sulfone, TMS) have been prepared and examined for use in lithium-ion batteries. The addition of sulfone is expected to improve the lithium salts solvability, ionic conductivity and electrode compatibility of the ionic liquid greatly. More importantly, the addition of sulfone is not expected to deteriorate the peculiar properties of the ionic liquid, such as the wide electrochemical window and non-flammability. Experimental results have shown that the reversible discharge capacities of the Li/LiFePO4 half-cell, which contains a 0.5 M LiTFSI/(60%) PP14-TFSI/(40%) TMS mixed electrolyte at a current density of 0.05 C and 1 C, can reach up to 160 and 150 mAh g−1, respectively, which are much higher than the discharge capacity achieved using the pure ionic liquid electrolyte under the same conditions. Furthermore, lithium difluoro(oxalato)borate (LiDFOB) has been found to have positive effects on the battery performance of the mixed electrolytes. The 0.5 M LiDFOB/(60%) PP14-TFSI/(40%) TMS mixed electrolyte exhibits better compatibility with the Li1.2Ni0.2Mn0.6O2 cathode than conventional electrolytes, where an initial discharge capacity of 255 mAh g−1 is obtained and a stable capacity of above 230 mAh g−1 is retained after 30 cycles.Graphical abstractMixed electrolytes based on ionic liquid and sulfone have been developed and demonstrated to show high safety, good electrochemical stability and good electrode compatibility.Highlights► Mixed electrolytes based on ionic liquid and sulfone. ► The electrolytes exhibit wide electrochemical windows and non-flammability. ► The addition of sulfone improve electrode compatibility of the electrolytes greatly. ► Lithium difluoro(oxalato)borate also has positive effects on the battery performance.
Co-reporter:Feng Wu, Yuelei Zheng, Li Li, Guoqiang Tan, Renjie Chen, and Shi Chen
The Journal of Physical Chemistry C 2013 Volume 117(Issue 38) pp:19280-19287
Publication Date(Web):August 22, 2013
DOI:10.1021/jp401964f
A novel electrolyte thin film has been prepared by radio-frequency magnetron sputtering using a Li–B–P–O target in a pure N2 atmosphere at various temperatures. The results indicate that the thin film deposited at room temperature is amorphous and its surface is smooth, dense, and uniform with the average thickness <1 μm, whereas that deposited at 400 °C shows the mixture of crystal and amorphous structure, which is more beneficial to the improvement on lithium ion motility in the network. The thin films exhibit an ionic conductivity of 3.5 × 10–6 S cm–1 and a electrochemical stability window of 7.8 V as well as outstanding chemical durability. Structural analyses suggest that their excellent chemical and electrochemical performances can be attributed to the combination of “mixed former” and “nitrogen incorporation” effects. The former produces nonbridging oxygen groups that provide vacant sites for lithium ions to move in or out of as well as expand the lithium ion conduction pathway. The latter leads to a more complicated cross-linked structure containing −N< and −N═ bonds instead of −O– and O═, which brings about more lithium ion transport channels in the network.
Co-reporter: Feng Wu;Dr. Junzheng Chen; Li Li;Teng Zhao;Zhen Liu; Renjie Chen
ChemSusChem 2013 Volume 6( Issue 8) pp:1438-1444
Publication Date(Web):
DOI:10.1002/cssc.201300260
Abstract
Polypyrrole–polyethylene glycol (PPy/PEG)-modified sulfur/aligned carbon nanotubes (PPy/PEG–S/A-CNTs) were synthesized by using an in situ polymerization method. The ratio of PPy to PEG equaled 31.7:1 after polymerization, and the PEG served as a cation dopant in the polymerization and electrochemical reactions. Elemental analysis, FTIR, Raman spectroscopy, XRD, and electrochemical methods were performed to measure the physicochemical properties of the composite. Elemental analysis demonstrated that the sulfur, PPy, PEG, A-CNT, and chloride content in the synthesized material was 64.6 %, 22.1 %, 0.7 %, 12.1 %, and 0.5 %, respectively. The thickness of the polymer shell was about 15–25 nm, and FTIR confirmed the successful PPy/PEG synthesis. The cathode exhibited a high initial specific capacity of 1355 mAh g−1, and a sulfur usage of 81.1 %. The reversible capacity of 924 mAh g−1 was obtained after 100 cycles, showing a remarkably improved cyclability compared to equivalent systems without PEG doping and without any coatings. PPy/PEG provided an effective electronically conductive network and a stable interface structure for the cathode. Rate performance of the PPy/PEG– S/A-CNT composite was more than double that of the unmodified S/A-CNTs. Remarkably, the battery could work at a very high current density of 8 A g−1 and reached an initial capacity of 542 mAh g−1; it also retained a capacity of 480 mAh g−1 after 100 cycles. The addition of PEG as a dopant in the PPy shell contributed to this prominent rate improvement. Lithium ions and electrons were available everywhere on the surfaces of the particles, and thus could greatly improve the electrochemical reaction; PEG is a well-known solvent for lithium salts and a very good lithium-ion catcher.
Co-reporter:Guoqiang Tan, Feng Wu, Li Li, Renjie Chen, and Shi Chen
The Journal of Physical Chemistry C 2013 Volume 117(Issue 12) pp:6013-6021
Publication Date(Web):March 8, 2013
DOI:10.1021/jp309724q
Novel coralline glassy lithium phosphate-coated LiFePO4 cathodes successfully prepared by radio frequency magnetron sputtering have been studied in lithium ion batteries. These coated LiFePO4 show higher reversible capacity, stable cycle performance, and improved power capability compared to the bare one. These favorable properties are considered to be attributed to the good conductivity and stability of the glassy lithium phosphate coating. The amorphous nature of the coating reduces the anisotropy of the surface properties of LiFePO4 electrode and enhances the Li+ ionic diffusion into the LiFePO4. The glassy lithium phosphate is an effective Li+ conductor, which increases the ionic and electronic transport on the surface and into the bulk of LiFePO4 electrode, extends the electroactive zone, and facilitates the transfer kinetics. It is also a stable Li-excess material, which provides an extra lithium capacity and maintains the electrode structural integrality. Radio frequency sputtering coating of stable Li+ conductors on the surface of nanosized LiFePO4 is an attractive way to improve its power capability, and these specific LiFePO4 cathodes have great potential for application in high-power lithium ion batteries.
Co-reporter:Feng Wu, Jin Xiang, Li Li, Junzheng Chen, Guoqiang Tan, Renjie Chen
Journal of Power Sources 2012 Volume 202() pp:322-331
Publication Date(Web):15 March 2012
DOI:10.1016/j.jpowsour.2011.11.065
p-Toluenesulfonyl isocyanate (PTSI) has been used as a novel film-forming additive in tetramethylene sulfone (TMS)-based electrolytes and the mixed electrolytes have been examined for use in rechargeable lithium-ion batteries. The ionic conductivities of the TMS/PTSI composite electrolytes with lithium salt are mostly in the order of 10−3 S cm−1 at ambient temperature and the electrochemical stability windows are in excess of 5.0 V versus Li/Li+. Compared with pure TMS-based electrolyte, the mixed electrolytes show lower melting points, better wettability and enhanced battery performance. The improved battery performance is mainly attributed to the formation of an effective solid electrolyte interface layer formed by the reductive decomposition of PTSI. The battery performance is influenced strongly by the presence of sulfonyl groups in isocyanate and the addition of different lithium salts. Moreover, the mixed electrolytes exhibit good thermal stability and low combustibility. All of the results show that the sulfonyl isocyanate/sulfone mixed electrolytes are a promising choice for use in rechargeable lithium-ion batteries.Graphical abstractThe sulfonyl isocyanate/sulfone binary electrolytes exhibit excellent compatibility with graphite anode, which is attributed to the fact that sulfonyl isocyanate can form an effective SEI layer on the anode surface due to the reduction of NCO and sulfonyl functional groups.Highlights► Sulfonyl isocyanate/sulfone binary electrolyte based on p-toluenesulfonyl isocyanate (PTSI) and tetramethylene sulfone (TMS). ► This mixed electrolyte can afford an effective SEI formation by PTSI decomposition on the surface of MCMB electrode. ► The sulfonyl group in PTSI has the ability to facilitate SEI formation. ► Excellent compatibility of the mixed electrolyte with LiCoO2 cathode, which is comparable with the state-of-the-art electrolyte. ► The new electrolyte also exhibits good thermal stability and low flammability.
Co-reporter:Li Li;RenJie Chen;XiaoXiao Zhang;Feng Wu;Jing Ge;Man Xie
Science Bulletin 2012 Volume 57( Issue 32) pp:4188-4194
Publication Date(Web):2012 November
DOI:10.1007/s11434-012-5200-5
A new idea for reuse of the cathode materials of lithium-ion batteries (LIBs) is investigated to develop an environmentally friendly process for recycling spent batteries. LiCoO2 is re-synthesized from spent LIBs by leaching and a sol-gel method calcined at high temperature. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are employed to study the reactions occurring calcination that are responsible for the weight losses. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to determine the structures of the LiCoO2 powders. It was found that a pure phase of LiCoO2 can be obtained by the re-synthesis process. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are used to evaluate the electrochemical properties of the LiCoO2 powders. The discharge capacity of re-synthesized LiCoO2 is 137 mAh g−1 at the 0.1 C rate, and the capacity retention of the re-synthesized LiCoO2 is 97.98% after 20 cycles at the 0.1 C rate, and 88.14% after 40 cycles. The results indicate that the re-synthesized LiCoO2 displays good charge/discharge performance and cycling behavior.
Co-reporter:Guoqiang Tan ; Feng Wu ; Li Li ; Yadong Liu ;Renjie Chen
The Journal of Physical Chemistry C 2012 Volume 116(Issue 5) pp:3817-3826
Publication Date(Web):January 9, 2012
DOI:10.1021/jp207120s
We report for the first time a new lithium ion conducting Li–Al–Ti–P–O–N thin film solid electrolyte for all-solid-state lithium ion batteries. It was prepared by radio frequency (RF) magnetron sputtering deposition using a NASICON structural Li–Al–Ti–P–O target in a N2 atmosphere at various temperatures. XRD and SEM test results showed that the thin film was composed of an amorphous structure and that its surface was smooth, dense, and homogeneous. FTIR and XPS analyses indicated that nitrogen atoms were actually incorporated into the Li–Al–Ti–P–O matrix framework. The substitution of nitrogen for oxygen in the thin film created more abundant cross-linking structures and decreased the electrostatic energy, which favored the higher mobility of lithium ions. A high Li ionic conductivity of 1.22 × 10–6 S/cm was obtained for the thin film deposited at room temperature. Moreover, the higher value of 1.22 × 10–5 S/cm for the thin film deposited at 500 °C indicated that some crystallites in the amorphous film might be beneficial in improving Li ionic conductivity. Therefore, different conductivity values are correlated with structural differences. The temperature dependence of the ionic conductivities fit the Arrhenius relation and the thin film deposited at 500 °C possessed of the lowest activation energy. Electrochemical analyses suggest that the high Li ionic conductivity is attributed to the reduced activation energy by the control of composition and structure. These properties make this thin film electrolyte a promising candidate material for use in all-solid-state thin film lithium ion batteries.
Co-reporter:Feng Wu;Guoqiang Tan;Renjie Chen;Li Li;Jin Xiang ;Yuelei Zheng
Advanced Materials 2011 Volume 23( Issue 43) pp:5081-5085
Publication Date(Web):
DOI:10.1002/adma.201103161
Co-reporter:Jin Xiang, Renjie Chen, Feng Wu, Li Li, Shi Chen, Qinqin Zou
Electrochimica Acta 2011 Volume 56(Issue 22) pp:7503-7509
Publication Date(Web):1 September 2011
DOI:10.1016/j.electacta.2011.06.103
We prepared 3 protic ionic liquids based on trifluoromethanesulfonic acid and an amide, namely isobutyramide (ITSA), n-butyramide(NTSA), and benzamide(BTSA). All of the protic ionic liquids exhibit excellent thermal stability (above 200 °C). ITSA has the highest ionic conductivity, which is 32.6 mS/cm at 150 °C. ITSA was used to prepare anhydrous, conducting composite membranes based on polymers of polyvinylidene-fluoride (PVDF) to serve as intermediate temperature proton exchange membrane fuel cells. This type of composite membrane possesses good thermal stability, high ionic conductivity and good mechanical properties. Increasing the polymer content leads to the improvement of mechanical properties, but is accompanied by a reduction in ionic conductivity. We made efforts to eliminate the trade-off between strength and conductivity of the ITSA/PVDF composite membrane by adding polyamide imide, which resulted in a simultaneous increase in strength and conductivity. A conductivity of 7.5 mS/cm is achieved in a membrane containing 60 wt.% ITSA and 5 wt.% PAI in PVDF at 150 °C.
Co-reporter:Feng Wu ; Junzheng Chen ; Renjie Chen ; Shengxian Wu ; Li Li ; Shi Chen ;Teng Zhao
The Journal of Physical Chemistry C 2011 Volume 115(Issue 13) pp:6057-6063
Publication Date(Web):March 16, 2011
DOI:10.1021/jp1114724
Novel sulfur/polythiophene composites with core/shell structure composites were synthesized via an in situ chemical oxidative polymerization method with chloroform as a solvent, thiophene as a reagent, and iron chloride as an oxidant at 0 °C. Different ratios of the sulfur/polythiophene composites were characterized by elemental analysis, FTIR, XRD, SEM, TEM, and electrochemical methods. A suitable ratio for the composites was found to be 71.9% sulfur and 18.1% polythiophene as determined by CV and EIS results. Conductive polythiophene acts as a conducting additive and a porous adsorbing agent. It was uniformly coated onto the surface of the sulfur powder to form a core/shell structure, which effectively enhances the electrochemical performance and cycle life of the sulfur cells. The initial discharge capacity of the active material was 1119.3 mA h g−1, sulfur and the remaining capacity was 830.2 mA h g−1 sulfur after 80 cycles. After a rate test from 100 to 1600 mA g−1 sulfur, the cell remained at 811 mA h g−1 sulfur after 60 cycles when the current density returned to 100 mA g−1 sulfur. The sulfur utilization, the cycle life, and the rate performance of the S−PTh core/shell electrode in a lithium−sulfur battery improved significantly compared to that of the pure sulfur electrode. The pore and thickness of the shell affected the battery performance of the lithium ion diffusion channels.
Co-reporter:Feng Wu ; Junzheng Chen ; Li Li ; Teng Zhao ;Renjie Chen
The Journal of Physical Chemistry C 2011 Volume 115(Issue 49) pp:24411-24417
Publication Date(Web):October 17, 2011
DOI:10.1021/jp207893d
Rapid in situ chemical oxidation polymerization of polyaniline was carried out to coat MWCNT-core/sulfur-shell structures. The S-coated-MWCNTs were obtained by ball-milling and thermal treatment. The polymerization was carried out by adding 2.6 g of dispersed S/MWCNT and 0.65 g of aniline hydrochloride to ethanol, and then mixing in a certain amount of ammonium peroxydisulfate dissolved in 0.2 M HCl. The addition of S/MWCNT reduced the polymerization time from 60 to 21 min. The composites were characterized by elemental analysis, FTIR, XRD, SEM, TEM, and electrochemical methods. A 70.0% sulfur, 20.2% emeraldine PANi salt and 9.8% MWCNT composite gave the typical two reduction peaks and two oxidation peaks; these are due to three polysulfide species. The initial discharge capacity was 1334.4 mAh g–1-S for the PANi-S/MWCNT electrode and the remaining capacity was 932.4 mAh g–1-S after 80 cycles. The columbic efficiency doubled to 92.4% compared to S-MWCNT-2. The rate of the reaction upon using PANi-S/MWCNT electrode was found to be almost twice that of the S/MWCNT composites. Because of the porous polymer, the diffusion distance of the lithium ion from the bulk liquid was reduced. The gel-like cathode composites and the higher conductivities improved the kinetics of the lithium sulfur redox reaction.
Co-reporter:Li Li, Renjie Chen, Ge Jing, Guiyou Zhang, Feng Wu, Shi Chen
Applied Surface Science 2010 Volume 256(Issue 14) pp:4533-4537
Publication Date(Web):1 May 2010
DOI:10.1016/j.apsusc.2010.02.042
Abstract
TiO2 electrodes are coated with NiO by DC magnetron sputtering, and their structural, optical and electrochemical performance has been investigated. X-ray diffractometry (XRD), UV–vis spectrophotometry, scanning electron microscopy (SEM), AC impedance, and linear sweep voltammetry (LSV) are used to characterize the TiO2/NiO electrodes. Their performance is evaluated with a computer controlled electrochemical workstation in combination with three conventional electrodes. The experimental results indicate that the surface modification of TiO2 electrodes with sputtered NiO reduces trap sites on TiO2 and improves the electrochemical performance of dye-sensitized solar cells (DSSCs). Sputtering NiO for 7 min, which is about 21 nm thick, on 6.5 μm thick TiO2 greatly improves the DSSC parameters, and the conversion efficiency increases from 3.21 to 4.16%. Mechanisms of the influence of the NiO coating on electrochemical performance are discussed.
Co-reporter:Feng Wu ; Jin Xiang ; Renjie Chen ; Li Li ; Junzheng Chen ;Shi Chen
The Journal of Physical Chemistry C 2010 Volume 114(Issue 47) pp:20007-20015
Publication Date(Web):November 5, 2010
DOI:10.1021/jp104905p
We prepared three series of novel protic ionic liquids (PILs) based on acetamide and a Brønsted acid (HX, where X is CF3COO−, CH3COO−, or HSO4−) by a simple atom-economic neutralization reaction. We investigated their physicochemical properties, such as acidic scale, viscosity, ionic conductivity, and thermal characteristics, as well as the structure−activity relationships of these PILs. Carboxylic acid formation is only observed in the acetamide sulfate complex system by FT-IR. The ionic conductivities for most of the samples are between 10−3 and 10−1 S/m at room temperature and at low viscosity. Acetamide trifluoroacetate (ATFA) with a molar ratio of 5/5 (acetamide/trifluoroacetic acid) has an ionic conductivity of 0.25 S/m, and its viscosity is only 10 cP at 25 °C. The samples exhibit better properties at higher temperatures. ATFA with molar ratios of 7/3 and 8/2 have ionic conductivities of 1.13 and 1.07 S/m at 80 °C, respectively. Moreover, most of the prepared samples possess relatively moderate thermal stabilities (up to 106 °C for ATFA) and a wide liquid range (down to −69 °C for ATFA). All these properties make these acetamide-based PILs of interest as reaction media, as catalysts in organic synthesis, or as electrolytes in fuel cells.
Co-reporter:Feng Wu, Yadong Liu, Renjie Chen, Shi Chen, Guoqing Wang
Journal of Power Sources 2009 Volume 189(Issue 1) pp:467-470
Publication Date(Web):1 April 2009
DOI:10.1016/j.jpowsour.2008.12.042
Novel Li–Ti–Si–P–O–N thin-film electrolyte was successfully fabricated by RF magnetron sputtering from a Li–Ti–Si–P–O target in N2 atmosphere at various temperatures. XRD, SEM, EDX, XPS, and EIS were employed to characterize their structure, morphology, composition and electrochemical performances. The films were smooth, dense, uniform, without cracks or voids, and possessed an amorphous structure. Their room temperature lithium-ion conductivities were measured to be from 3.6 × 10−7 S cm−1 to 9.2 × 10−6 S cm−1, and the temperature dependence of the ionic conductivities fits the Arrhenius relation. This kind of electrolyte possessed good properties is a promising candidate material for solid-state thin-film lithium batteries.
Co-reporter:Yue Jiao Li, Feng Wu, Ren Jie Chen
Chinese Chemical Letters 2009 Volume 20(Issue 5) pp:519-522
Publication Date(Web):May 2009
DOI:10.1016/j.cclet.2009.01.025
Composite polymer electrolytes based on mixing soft-segment waterborne polyurethane (WPU) and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (BMImTFSI) have been prepared and characterized. The addition of BMImTFSI results in an increase of the ionic conductivity. At high BMImTFSI concentration (BMImTFSI/WPU = 3 in weight ratio), the ionic conductivity reaches 4.27 × 10−3 S/cm at 30 °C. These composite polymer electrolytes exhibit good thermal and electrochemical stability, which are high enough to be applied in lithium batteries.
Co-reporter:Feng Wu, Yue Jiao Li, Ren Jie Chen, Shi Chen
Chinese Chemical Letters 2009 Volume 20(Issue 1) pp:115-118
Publication Date(Web):January 2009
DOI:10.1016/j.cclet.2008.09.060
The mixing soft-segment WPU (waterborne polyurethane) polymer electrolytes were synthesized by using PEO (poly(ethylene oxide)) and PDMS (polydimethylsiloxane) as the soft segments. These polymer electrolytes exhibit good thermal and electrochemical stability. The conductivity of the gel polymer electrolyte is 2.52 × 10−3 S/cm at 25 °C with the LiTFSI/(DMC + EC) content of 130%.
Co-reporter:Feng Wu, Sheng Xian Wu, Ren Jie Chen, Shi Chen, Guo Qing Wang
Chinese Chemical Letters 2009 Volume 20(Issue 10) pp:1255-1258
Publication Date(Web):October 2009
DOI:10.1016/j.cclet.2009.04.036
The structure and characteristic of carbon materials have a direct influence on the electrochemical performance of sulfur–carbon composite electrode materials for lithium–sulfur battery. In this paper, sulfur composite has been synthesized by heating a mixture of elemental sulfur and activated carbon, which is characterized as high specific surface area and microporous structure. The composite, contained 70% sulfur, as cathode in a lithium cell based on organic liquid electrolyte was tested at room temperature. It showed two reduction peaks at 2.05 V and 2.35 V, one oxidation peak at 2.4 V during cyclic voltammogram test. The initial discharge specific capacity was 1180.8 mAh g−1 and the utilization of electrochemically active sulfur was about 70.6% assuming a complete reaction to the product of Li2S. The specific capacity still kept as high as 720.4 mAh g−1 after 60 cycles retaining 61% of the initial discharge capacity.
Co-reporter:Feng Wu, Renjie Chen, Fan Wu, Li Li, Bin Xu, Shi Chen, Guoqing Wang
Journal of Power Sources 2008 Volume 184(Issue 2) pp:402-407
Publication Date(Web):1 October 2008
DOI:10.1016/j.jpowsour.2008.04.062
Binary room-temperature complex electrolytes have been synthesized based on lithium perchlorate (LiClO4) and organic molecules with acylamino groups, including acetamide, ethyleneurea, 2-oxazolidinone (OZO), urea, methylurea (NMU) and 1,3-dimethylurea (DMU). Both LiClO4 and all organic molecules with acylamino groups are solid at room-temperature, but their mixtures at the proper molar ratio are liquid with a liquidus temperature about below 25 °C characterized by differential scanning calorimetry (DSC). Infrared spectroscopic studies show that the organic molecules can coordinate with the Li+ cation and the ClO4− anion via their polar groups (the CO and NH groups). Such strong interactions lead to the dissociation of LiClO4 and the breakage of the hydrogen bonds among the organic molecules, resulting in the formation of the complex systems. Electrochemical performances of the complex electrolytes are evaluated with ac impedance spectroscopy, cyclic voltammetry (CV), and in a test electric double layer capacitor (EDLC), respectively. The LiClO4–acetamide electrolyte at molar ratio 1:5.5 exhibits the highest ionic conductivity, 1.25 × 10−3 S cm−1 at 25 °C and 11.5 × 10−3 S cm−1 at 80 °C. The analysis for the CV behavior indicates that the electrochemical stability window of these electrolytes is above 3 V. The results demonstrate that these complex systems are promising electrolyte candidates for supercapacitor and probably other electrochemical devices.
Co-reporter:Feng Wu, Ji Qian, Renjie Chen, Yusheng Ye, Zhiguo Sun, Yi Xing and Li Li
Journal of Materials Chemistry A 2016 - vol. 4(Issue 43) pp:NaN17041-17041
Publication Date(Web):2016/10/05
DOI:10.1039/C6TA06516C
A light-weight boron-functionalized reduced graphene oxide (B-rGO) layer (only 0.2–0.3 mg cm−2) coated on a separator is demonstrated to improve the cycling stability and rate performance of lithium–sulfur batteries. Such an enhanced performance is ascribed to: (i) the boron species in B-rGO can enhance the binding with polysulfides, which helps suppress the shuttle reactions, thus alleviating overcharge and self-discharge; (ii) a certain amount of the boron doped into the graphene matrix can improve the electrical conductivity of the coating layer, thus enhancing the utilization of sulfur and improving the rate performance of the cells. With the B-rGO coated separator, the severe self-discharge of Li–S batteries can be alleviated. More importantly, for the high sulfur loading cathodes (above 4.5 mg cm−2), an improved high areal capacity of 4.71 mA h cm−2 can be achieved using the B-rGO coated separator. The above results demonstrate the potential of the B-rGO coated separator for practical lithium–sulfur batteries, and such a strategy can be extended to other energy storage systems.
Co-reporter:Renjie Chen, Teng Zhao and Feng Wu
Chemical Communications 2015 - vol. 51(Issue 1) pp:NaN33-33
Publication Date(Web):2014/08/06
DOI:10.1039/C4CC05109B
In terms of sustainable development and environmental issues, the design and fabrication of efficient energy storage devices will be more critical in the future than at any time in the past. Li–S batteries are promising candidates for such a purpose due to their high specific capacity and low environmental impact. This review has systematically retraced the advances in the field of Li–S batteries over the past half century and highlighted the main breakthroughs in a number of areas, covering the mechanism determination, cathode engineering, theoretical simulation, and electrolyte tailoring and anode protection. Furthermore, we discuss the remaining challenges towards their practical application. It is expected that Li–S batteries with 3D inter-connected or conformal assemblies will surpass new horizons in the coming years.
Co-reporter:Feng Wu, Qizhen Zhu, Li Li, Renjie Chen and Shi Chen
Journal of Materials Chemistry A 2013 - vol. 1(Issue 11) pp:NaN3666-3666
Publication Date(Web):2013/01/10
DOI:10.1039/C3TA01182H
A new binary electrolyte containing tetramethylene sulfone (TMS) and hexamethylene diisocyanate (HDI) with lithium difluoro(oxalate)borate (LiODFB) as the lithium salt has been prepared and investigated for physicochemical properties. A linear relationship between the frontier molecular orbital energies and the oxidation/reduction potentials is preliminarily confirmed. Compared to the pure TMS electrolyte, a mixture of TMS and HDI exhibits a wider electrochemical stability window, better wettability and an improved low temperature performance. Combined with the mixed electrolyte, LiCoO2 and LiNi1/3Mn1/3Co1/3O2 cathode materials show specific capacities of nearly 134.5 mA h g−1 and 168.3 mA h g−1 after 50 cycles, respectively, which is superior to those containing the traditional electrolyte. Furthermore, the composite electrolyte exhibits a good compatibility with the high voltage LiNi0.5Mn1.5O4 cathode material which has a specific capacity close to 120 mA h g−1 after 50 cycles. The enhanced battery performance is mainly due to HDI, which has a high oxidation potential (5.2 V), good wettability, a low melting point and an outstanding ability to form effective solid electrolyte interface layers. In addition, LiODFB makes a contribution to the compatibility of the electrolyte due to its passivation toward aluminum, its high solubility and its ability to support reversible metallic lithium cycling. All of the properties above indicate that the LiODFB/HDI/TMS mixed electrolyte is a promising material and can have applications in the field of lithium batteries.
Co-reporter:Feng Wu, Xiaoxiao Zhang, Taolin Zhao, Renjie Chen, Yusheng Ye, Man Xie and Li Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 34) pp:NaN17626-17626
Publication Date(Web):2015/07/21
DOI:10.1039/C5TA04673D
Hierarchical mesoporous/macroporous Co3O4 ultrathin nanosheets were synthesized as free-standing catalysts for rechargeable Li–O2 batteries. The Co3O4 nanosheets were directly grown on nickel foam through a simple hydrothermal reaction, followed by a calcination process. The impact of solvents used in the hydrothermal reaction on the morphology of catalysts has been investigated. The results showed that the prepared Co3O4 catalyst synthesized with ethylene glycol and deionized water (1:1 in volume) presented a much better electrochemical performance with a capacity of 11882 mA h g−1 under a current density of 100 mA g−1 during the initial discharge and good cycling stability (more than 80 cycles at 200 mA g−1 with the capacity limited to 500 mA h g−1). Meanwhile, the charge potential was significantly reduced to ca. 3.7 V. It is interesting to find that the morphology of the discharge product, Li2O2 could be changed by controlling the shape of catalysts. The impacts of the hierarchical mesoporous/macroporous nanosheet structure on the performance of Li–O2 batteries have been discussed.
Co-reporter:Renjie Chen, Yan Chen, Lu Zhu, Qizhen Zhu, Feng Wu and Li Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 12) pp:NaN6372-6372
Publication Date(Web):2015/02/06
DOI:10.1039/C5TA00818B
Ionic liquid-based electrolytes are widely used in lithium-ion batteries to obtain wide electrochemical windows and fewer safety concerns. In order to enhance the energy density and rate capability, lithium difluoro(oxalato)borate (LiODFB) and dimethyl sulfite (DMS) have been introduced into N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI)-based electrolytes as lithium salt and co-solvent, respectively. The binary LiODFB–PYR14TFSI/DMS (7:3, m/m) electrolyte has been prepared and investigated. FTIR analysis has demonstrated that stretching of the functional groups CO and O–S–O plays a vital role in the solvation of the designed electrolyte, and elevate the ionic conductivity of the electrolyte by an order of magnitude. In comparison to when a LiTFSI–PYR14TFSI/DMS (7:3, m/m) electrolyte is used, Li/MCMB half-cells containing the novel electrolyte achieve excellent electrochemical performances, even superior to those of conventional organic electrolytes, maintaining a discharge capacity and coloumbic efficiency of 273.2 mA h g−1 and 99%, respectively, after 80 cycles. This tremendous improvement is ascribed to the joint reductive composition of DMS and LiODFB, resulting in the formation of a more robust solid-electrolyte interface (SEI) film at the MCMB electrode. Besides, the discharge capacity of Li/LiFePO4 half-cells with the LiODFB-based electrolyte could still reach up to 139 mA h g−1 at a rate of 1 C. All those characteristics make it a promising electrolyte material for safe and high-performance lithium-ion batteries.
Co-reporter:Feng Wu, Qizhen Zhu, Renjie Chen, Nan Chen, Yan Chen and Li Li
Chemical Science (2010-Present) 2015 - vol. 6(Issue 12) pp:NaN7283-7283
Publication Date(Web):2015/09/18
DOI:10.1039/C5SC02761F
Lithium-ion batteries have been attracting much attention which enables the revolution of wireless global communication. Ionic liquids are regarded as promising candidates for lithium-ion battery electrolytes because they can overcome the limitations of high operating temperatures and flammability concerns of traditional electrolytes. However, at low temperatures they suffer from low ionic conductivity and phase transition. In this paper mixed electrolyte systems are described based on N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)-imide (Pyr1,2O1TFSI) and lithium difluoro(oxalate)borate (LiODFB) lithium salt, with ethylene sulphite (ES) or dimethyl sulphite (DMS) as a cosolvent. The mixed electrolyte system exhibits good ion transport properties (a conductivity of 8.163 mS cm−1), a wide electrochemical window (5.2 V), non-flammability, the ability to form films to protect the anode and a large operating temperature range (−40 °C to 60 °C). We compare the performance and function of the new mixed electrolyte system with a variety of ionic liquid/cosolvent electrolyte systems developed in previous studies. The ring-chain synergy takes advantage of the availability of both high permittivities based on the ring-like components and low viscosities based on the chain-like components in the mixed electrolyte system and causes the electrolyte to exhibit a good overall performance in safety, ion transport and compatibility with electrodes.
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