Co-reporter:Yuanlong Liu, Deying Mu, Ruhong Li, Quanxin Ma, Rujuan Zheng, and Changsong Dai
The Journal of Physical Chemistry C 2017 Volume 121(Issue 8) pp:
Publication Date(Web):February 13, 2017
DOI:10.1021/acs.jpcc.6b12970
As an indispensable part of lithium-ion batteries (LIBs), closed-loop recycling, reusing the electrolyte from spent LIBs, has not yet been fulfilled experimentally. Herein, this paper presents a LIB electrolyte recycling approach which consists of supercritical CO2 extraction, resin, and molecular sieve purification and components supplements. The resultant electrolyte exhibited a high ionic conductivity of 0.19 mS·cm–1 at 20 °C, which was very close to a commercial electrolyte with the same composition. Moreover, the electrolyte was also electrochemically stable up to 5.4 V (vs Li/Li+) in the linear sweep voltammetry (LSV) measurement. The application potential of reclaimed electrolyte was demonstrated by Li/LiCoO2 battery presenting the initial discharge capacity of 115 mAh·g–1 with a capacity retention of 66% after 100 cycles at 0.2 C. This investigation is a crucial break for electrolyte recycling and opens a bright route toward realizing closed-loop LIB recycling.
Co-reporter:Xiujuan Min;Deying Mu;Ruhong Li
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 8) pp:3163-3171
Publication Date(Web):2017/04/10
DOI:10.1039/C6NJ04029B
The problem of the decrease in cycling stability of Li3(V0.9Mg0.1)2(PO4)3/C limits its practical application in a broad electrochemical window. However, the cause of the cycling stability decrease in Li3(V0.9Mg0.1)2(PO4)3/C has not been studied in previous research. In this paper, to illustrate the cause of the decreased cycling stability of the Li3(V0.9Mg0.1)2(PO4)3/C samples, we investigated the crystal structure changes in the cathode materials in a broad electrochemical window. The structure of the Li3(V0.9Mg0.1)2(PO4)3/C samples was analyzed by XRD refinement, SEM and TEM. The results indicate that the higher the charge cut-off voltage is, the worse the cycling stability of the sample is. It was concluded that the cell volume of the Li3(V0.9Mg0.1)2(PO4)3/C samples expands irreversibly after cycling in different voltage ranges, and the bond lengths of Li(3)–O become longer while those of Li(2)–O and Li(1)–O become shorter. This means that the bond energy of the Li(3) ion increased, and the bond energy of the Li(1) and Li(2) ions decreased. This is not beneficial to the intercalation/deintercalation of Li ions with the increase in the charge cut-off voltage. The TEM test shows that the carbon layer of the samples is destroyed with the increase in the charge cut-off voltage. It is reasonably inferred that the crystal structure change in the Li3(V0.9Mg0.1)2(PO4)3/C samples causes poor cycling stability with the increase in the charge cut-off voltage.
Co-reporter:Deying Mu;Yuanlong Liu;Ruhong Li;Quanxin Ma
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 15) pp:7177-7185
Publication Date(Web):2017/07/24
DOI:10.1039/C7NJ00771J
Electrolyte solutions have a vital function in lithium-ion batteries. In consideration of their toxic and harmful characteristics and widespread applications in the EVs, the treatment or recovery of the electrolyte is of concern and accurate analysis is needed for the resource and environment benefits. In this work, we present a highly-selective electrolyte recovery method—transcritical CO2 extraction—that combined the extraction and separation processes together. The use of response surface methodology helps in obtaining a simplified and optimized extraction protocol at room temperature and low pressure saving time and reagents. In order to evaluate these extracts, various techniques like GC-MS, GC-FID, FITR and NMR were applied. The GC-FID quantitative analysis and calculation formula may help with realizing the oriented control of the extraction process, and hexafluorophosphate (PF6−), fluoride (F−) and difluorophosphate (PO2F2−) detected by both 19F and 31P spectra imply the degradation pathway.
Co-reporter:Rujuan Zheng, Wenhui Wang, Yunkun Dai, Quanxin Ma, ... Changsong Dai
Green Energy & Environment 2017 Volume 2, Issue 1(Volume 2, Issue 1) pp:
Publication Date(Web):1 January 2017
DOI:10.1016/j.gee.2016.11.010
With the rapid development of consumer electronics and electric vehicles (EV), a large number of spent lithium-ion batteries (LIBs) have been generated worldwide. Thus, effective recycling technologies to recapture a significant amount of valuable metals contained in spent LIBs are highly desirable to prevent the environmental pollution and resource depletion. In this work, a novel recycling technology to regenerate a LiNi1/3Co1/3Mn1/3O2 cathode material from spent LIBs with different cathode chemistries has been developed. By dismantling, crushing, leaching and impurity removing, the LiNi1/3Co1/3Mn1/3O2 (selected as an example of LiNixCoyMn(1−x−y)O2) powder can be directly prepared from the purified leaching solution via co-precipitation followed by solid-state synthesis. For comparison purposes, a fresh-synthesized sample with the same composition has also been prepared using the commercial raw materials via the same method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements have been carried out to characterize these samples. The electrochemical test result suggests that the re-synthesized sample delivers cycle performance and low rate capability which are comparable to those of the fresh-synthesized sample. This novel recycling technique can be of great value to the regeneration of a pure and marketable LiNixCoyMn(1−x−y)O2 cathode material with low secondary pollution.
Co-reporter:Rujuan Zheng, Li Zhao, Wenhui Wang, Yuanlong Liu, Quanxin Ma, Deying Mu, Ruhong Li and Changsong Dai
RSC Advances 2016 vol. 6(Issue 49) pp:43613-43625
Publication Date(Web):19 Apr 2016
DOI:10.1039/C6RA05477C
A new process is optimized and presented for the recovery and regeneration of LiFePO4 from spent lithium-ion batteries (LIBs). The recycling process reduces the cost and secondary pollution caused by complicated separation and purification processes in spent LIB recycling. Amorphous FePO4·2H2O was recovered by a dissolution-precipitation method from spent LiFePO4 batteries. The effects of different surfactants (i.e. CTAB, SDS and PEG), which were added to the solution on the recovered FePO4·2H2O, were investigated. Li2CO3 was precipitated by adding Na2CO3 to the filtrate. Then the LiFePO4/C material was synthesized by a carbon thermal reduction method using recycled FePO4·2H2O and Li2CO3 as the Fe, P, and Li sources. The as-prepared LiFePO4/C shows comparable electrochemical performance to that of commercial equivalents.
Co-reporter:Xiujuan Min, Hua Huo, Ruhong Li, Jigang Zhou, Yongfeng Hu, Changsong Dai
Journal of Electroanalytical Chemistry 2016 Volume 774() pp:76-82
Publication Date(Web):1 August 2016
DOI:10.1016/j.jelechem.2016.05.020
•This paper studied cycling stability of Li3V2(PO4)3/C cathode in a broad electrochemical window.•The structure performance of Li3V2(PO4)3/C was studied in different electrochemical windows.•The electrochemical performance of Li3V2(PO4)3/C was studied in different electrochemical windows.In this paper, Li3V2(PO4)3/C was synthesized using the carbon thermal reduction method. The electrochemical performance of Li3V2(PO4)3/C in a broad electrochemical window was studied. The fine structure of Li3V2(PO4)3/C after cycling in different charge and discharge ranges was investigated by X-ray powder diffraction (XRD) refinement, X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The results show that the cycling stability of this material decreases with the increase of charge cut-off voltages. After cycling, the unit cell volume of Li3V2(PO4)3/C expanded irreversibly, in which the lengths of the Li(3)–O and V–O bonds became longer while those of Li(2)–O and Li(1)–O bonds became shorter. In the meantime, the amount of V5 + in the material increased and the carbon layer coated on the surface of the material was destroyed as the charge cut-off voltage was increased from 4.3 to 4.8 V. It is therefore reasonable to infer that the changes in the crystal structure of Li3V2(PO4)3/C cause the poor cycling performance of Li3V2(PO4)3/C. This result provides a research idea for improving the cyclic performance of Li3V2(PO4)3/C in the future.
Co-reporter:Quanxin Ma, Deying Mu, Yuanlong Liu, Shibo Yin and Changsong Dai
RSC Advances 2016 vol. 6(Issue 24) pp:20374-20380
Publication Date(Web):15 Feb 2016
DOI:10.1039/C5RA26667J
A Lithium-rich cathode material Li1.2Mn0.56Ni0.16Co0.08O2 modified with nanogold (Au@LMNCO) for lithium-ion (Li-ion) batteries was prepared using co-precipitation, solid-state reaction and surface treatment techniques. Au@LMNCO was prepared by thermally spraying gold on the surface of the lithium-rich cathode material (LMNCO). X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) results indicate that Au was successfully integrated into the surface of LMNCO. The cyclic voltammogram of Au@LMNCO shows a significant reduction in the reaction overpotential compared to that of LMNCO, which was a result of the nanogold formation. The stable reversible capacity of the Au@LMNCO electrode was 249 mA h g−1, and it could be retained at 244 mA h g−1 (98% retention) after 100 cycles at 0.5C. The coulombic efficiencies were over 98% except for the first five cycles. Moreover, Au@LMNCO also exhibited excellent rate capability. Even at a 5.0C rate, its discharge capacity was about 190 mA h g−1. The superior electrochemical performance can be attributed to its unique nanoplate characteristics, its structural stability, and the electrocatalytic activity of nanogold.
Co-reporter:Xiujuan Min, Deying Mu, Ruhong Li, Changsong Dai
Materials Science and Engineering: B 2016 Volume 213() pp:114-122
Publication Date(Web):November 2016
DOI:10.1016/j.mseb.2016.05.010
•Sintering time of Li3V2(PO4)3 reduced to 6 hours by adding hydrogen peroxide.•Electrochemical performance of Li3V2(PO4)3 was improved by reducing sintering time.•The Li3V2(PO4)3 production process was simplified during material synthesis stage.Li3V2(PO4)3/C has stable structure, high theory specific capacity and good safety performance, therefore it has become the research focus of lithium-ion batteries in recent years. The facile synthesis technology of Li3V2(PO4)3/C was characterized by adding different amounts of H2O2. Structure and morphology characteristics were examined by XRD, TG, Raman Spectroscopy, XPS and SEM. Electrochemical performance was investigated by constant current charging and discharging test. The results revealed that the Li3V2(PO4)3/C electrochemical performance of adding 15 mL H2O2 was better after sintering during 6 h. At the charge cut-off voltage of 4.3 V, the first discharge capacity at 0.2 C rate reached 127 mAh g−1. Because of adding H2O2 in the ball-mill dispersant, the vanadium pentoxide formed the wet sol. The molecular-leveled mixture increased the homogeneity of raw materials. Therefore, the addition of H2O2 shortened the sintering time and significantly improved the electrochemical performance of Li3V2(PO4)3/C.
Co-reporter:Quanxin Ma, Fangwei Peng, Ruhong Li, Shibo Yin, Changsong Dai
Materials Science and Engineering: B 2016 Volume 213() pp:123-130
Publication Date(Web):November 2016
DOI:10.1016/j.mseb.2016.04.010
•A series of Li-rich layered oxide cathode materials (Li1.2Mn0.56Ni0.16Co0.08O2) were successfully synthesized via a two-step synthesis method.•The effects of calcination temperature on the cathode materials were researched in detail.•A well-crystallized layered structure was obtained as the calcination temperature increased.•The samples calcined in a range of 850–900 °C exhibited excellent electrochemical performance.Lithium-rich layered oxide cathode materials (Li1.2Mn0.56Ni0.16Co0.08O2 (LLMO)) were synthesized via a two-step synthesis method involving co-precipitation and high-temperature calcination. The effects of calcination temperature on the cathode materials were studied in detail. Structural and morphological characterizations revealed that a well-crystallized layered structure was obtained at a higher calcination temperature. Electrochemical performance evaluation revealed that a cathode material obtained at a calcination temperature of 850 °C delivered a high initial discharge capacity of 266.8 mAh g−1 at a 0.1 C rate and a capacity retention rate of 95.8% after 100 cycles as well as excellent rate capability. Another sample calcinated at 900 °C exhibited good cycling stability. It is concluded that the structural stability and electrochemical performance of Li-rich layered oxide cathode materials were strongly dependent on calcination temperatures. The results suggest that a calcination temperature in a range of 850–900 °C could promote electrochemical performance of this type of cathode materials.
Co-reporter:Wenhui Wang, Jiaolong Zhang, Yue Lin, Zheng Jia, Changsong Dai
Electrochimica Acta 2014 Volume 116() pp:490-494
Publication Date(Web):10 January 2014
DOI:10.1016/j.electacta.2013.11.074
The structural evolution of Li3V2(PO4)3/C upon cycling in different potential ranges was studied via XRD. The results reveal that the repeated charge/discharge processes would cause the loss of crystallinity and irreversible expansion of unit cell volume, both of which are related to the applied upper limit of potential. The highest degree of the crystallinity loss and irreversible expansion of unit cell volume of the Li3V2(PO4)3/C sample cycled in the range of 3.0-4.8 V is considered to be partially responsible for the worst cycling performance among the three operating potential regions. On the contrary, no marked expansion of unit cell volume is observed when the upper limit of potential is extended from 4.3 V to 4.6 V. Accordingly, the Li3V2(PO4)3/C sample cycled in 3.0-4.6 V delivers extra 17-37 mAh g−1 specific capacity over that of 3.0-4.3 V with reasonable cycling stability. Therefore, the potential range of 3.0-4.6 V would be the best operating potential region for the practical applications of Li3V2(PO4)3.
Co-reporter:Wenhui Wang, Jiaolong Zhang, Zheng Jia, Changsong Dai, Yongfeng Hu, Jigang Zhou and Qunfeng Xiao
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 27) pp:13858-13865
Publication Date(Web):30 Jan 2014
DOI:10.1039/C3CP55495C
A series of Li3V2−2/3xZnx(PO4)3/C phases were synthesized by carbon thermal reduction assisted by the ball-mill process. Scanning electron microscopy (SEM) showed that the irregular morphology of the pristine Li3V2(PO4)3/C could be transformed to spherical upon doping with a suitable amount of zinc. The structural stability of the pristine and the Zn doped Li3V2(PO4)3/C were investigated via X-ray absorption near edge structure (XANES) spectroscopy and X-ray diffraction (XRD). The results revealed that Zn doping not only improves the stability of the VO6 octahedral structures before electrochemical cycling, but also reduces the degree of irreversible expansion of the c axis and the crystal volume upon repeated cycles. Among the Li3V2−2/3xZnx(PO4)3/C (0 ≤ x ≤ 0.15) series, the sample doped with 0.05 Zn atoms per formula unit showed the best electrochemical performance. Excess Zn doping (x > 0.05) didn't result in further improvement in the electrochemical performance due to the segregation effect and the inactive nature of Zn.
Co-reporter:Yuanlong Liu, Deying Mu, Rujuan Zheng and Changsong Dai
RSC Advances 2014 vol. 4(Issue 97) pp:54525-54531
Publication Date(Web):29 Sep 2014
DOI:10.1039/C4RA10530C
Supercritical fluid extraction (SFE) was applied to reclaim organic carbonate-based electrolytes of spent lithium-ion batteries. To optimize the SFE operational conditions, the response surface methodology was adopted. The parameters studied were as follow: pressure, ranging from 15 to 35 MPa; temperature, between 40 °C and 50 °C and static extraction time, within 45 to 75 min. The optimal conditions for extraction yield were 23 MPa, 40 °C and was dynamically extracted for 45 min. Extracts were collected at a constant flow rate of 4.0 L min−1. Under these conditions, the extraction yield was 85.07 ± 0.36%, which matched with the predicted value. Furthermore, the components of the extracts were systematically characterized and analyzed by using FT-IR, GC-MS and ICP-OES, and the effect of SFE on the electrolyte reclamation was evaluated. The results suggest that the SFE is an effective method for recovery of organic carbonate-based electrolytes from spent lithium-ion batteries, to prevent environmental pollution and resource waste.
Co-reporter:Wenhui Wang, Zhenyu Chen, Jiaolong Zhang, Changsong Dai, Jiajie Li, Dalong Ji
Electrochimica Acta 2013 Volume 103() pp:259-265
Publication Date(Web):30 July 2013
DOI:10.1016/j.electacta.2013.04.066
In order to synthesize pure derivative of rhombohedral Li3V2(PO4)3 (LVP), lithium-ion batteries materials Li2.5Na0.5V(2−2x/3)Nix(PO4)3/C (x = 0.03, 0.06, 0.09) and its control, monoclinic Li3V2(PO4)3/C (LVP/C), were prepared by sol–gel method. The samples were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), Raman spectroscopy, and electrochemical methods. The XRD patterns of Li2.5Na0.5V(2−2x/3)Nix(PO4)3/C are in good agreement with that of rhombohedral LVP, which indicates that the Na+–Ni2+ composite doping can change the structure of monoclinic LVP. All the composite doping samples displayed a single flat plateau at 3.7 V in the charge/discharge voltage profile, which is caused by transformation of multi-phase mechanism to single-phase mechanism. For Li2.5Na0.5V1.98Ni0.03(PO4)3/C, a specific discharge capacity of 108 mAh g−1 was achieved at a 0.5 C charge rate and a 1 C discharge rate, and a 99.0% retention rate of the initial capacity was obtained after 50 cycles.
Co-reporter:Jie Zhang, Changsong Dai, Jie Wei, Zhaohui Wen, Shujuan Zhang, Chuang Chen
Colloids and Surfaces B: Biointerfaces 2013 Volume 111() pp:179-187
Publication Date(Web):1 November 2013
DOI:10.1016/j.colsurfb.2013.05.040
•Calcium phosphate/chitosan composite coating on the MAO-AZ91D Mg alloy was prepared.•The composite coating slowed down the corrosion rate of Mg alloy in the m-SBF.•The coating on the MAO-AZ91D Mg alloy showed a good bioactivity in m-SBF.The degradation behavior of a MAO-AZ91D with a calcium phosphate/chitosan composite coating in the modified simulated human body fluid (m-SBF) was investigated by immersion experiments and electrochemical impedance spectroscopy. The compositions of the composite coating soaked in the m-SBF for different time intervals were studied by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, thermo-gravimetric analysis and differential thermal analysis. The microstructures of the composite coating at different soaking stages were observed by using a scanning electron microscope. Results show that the as-prepared composite coating could slow down the corrosion rate of the AZ91D alloy and it demonstrated good bioactivity in the m-SBF. The coating's morphology changed from a flake-like one into a spherical-shaped one with the increase of immersion time in the m-SBF.
Co-reporter:Zhenyu Chen;Guohui Yuan;Xinguo Hu;Xinyao Luo
Ionics 2013 Volume 19( Issue 8) pp:1077-1084
Publication Date(Web):2013 August
DOI:10.1007/s11581-012-0841-6
Mg-doping effects on the electrochemical property of LiFePO4–Li3V2(PO4)3 composite materials, a mutual-doping system, are investigated. X-ray diffraction study indicates that Mg doping decreases the cell volume of LiFePO4 in the composite. The cyclic voltammograms reveal that the reversibility of the electrode reaction and the diffusion of lithium ion is enhanced by Mg doping. Mg doping also improves the conductivity and rate capacity of 7LiFePO4–Li3V2(PO4)3 composite material and decreases the polarization of the electrode reaction. The discharge capacity of the Mg-doped composite was 93 mAh g−1 at the current density of 1,500 mA g−1, and Mg-doped composite has better discharge performance than the original 7LiFePO4–Li3V2(PO4)3 composite at low temperature, too. At −30 °C, the discharge capacity of Mg-doped LFVP is 89 mAh g−1, higher than that of the original composite. Electrochemical impedance spectroscopy study shows that Mg2+ doping could enhance the electrochemical activity of 7LiFePO4–Li3V2(PO4)3 composite. Mg doping has a positive influence on the electrochemical performance of the LiFePO4–Li3V2(PO4)3 composite material.
Co-reporter:Zhaohui Wen, Liming Zhang, Chao Chen, Yibo Liu, Changjun Wu, Changsong Dai
Materials Science and Engineering: C 2013 Volume 33(Issue 3) pp:1022-1031
Publication Date(Web):1 April 2013
DOI:10.1016/j.msec.2012.10.009
Slow corrosion rate and poor bioactivity restrict iron-based implants in biomedical application. In this study, we design a new iron-foam-based calcium phosphate/chitosan coating biodegradable composites offering a priority mechanical and bioactive property for bone tissue engineering through electrophoretic deposition (EPD) followed by a conversion process into a phosphate buffer solution (PBS). Tensile test results showed that the mechanical property of iron foam could be regulated through altering the construction of polyurethane foam. The priority coatings were deposited from 40% nano hydroxyapatite (nHA)/ethanol suspension mixed with 60% nHA/chitosan-acetic acid aqueous solution. In vitro immersion test showed that oxidation-iron foam as the matrix decreased the amount of iron implanted and had not influence on the bioactivity of this implant, obviously. So, this method could also be a promising method for the preparation of a new calcium phosphate/chitosan coating on foam construction.Highlights► Biodegradable ferromagnetic bone implants have been studied for the first time. ► The mechanical properties of iron foam were similar to those of human bone. ► Application of oxidation-iron foam had not influence on the bioactivity, obviously. ► The suggested chemical surface modification induced in vitro apatite formation.
Co-reporter:Jie Zhang, Chang-Song Dai, Jie Wei, Zhao-Hui Wen
Applied Surface Science 2012 Volume 261() pp:276-286
Publication Date(Web):15 November 2012
DOI:10.1016/j.apsusc.2012.08.001
Abstract
In order to improve the bonding strength between calcium phosphate/chitosan composite coatings and a micro-arc oxidized (MAO)-AZ91D Mg alloy, different influencing parameters were investigated in the process of electrophoretic deposition (EPD) followed by conversion in a phosphate buffer solution (PBS). Surface morphology and phase constituents of the as-prepared materials were investigated by using X-ray diffractometer (XRD), Fourier-transformed infrared spectrophotometer (FTIR), Raman spectrometer, scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS), and a thermo gravimetric and differential thermal analyzer (TG–DTA). Scratch tests were carried out to study the bonding properties between the coatings and the substrates. In vitro immersion tests were conducted to determine the corrosion behaviors of samples with and without deposit layers through electrochemical experiments. In the EPD process, the acetic acid content in the electrophoresis suspension and the electrophoretic voltage played important roles in improving the bonding properties, while the contents of chitosan (CS) and nano-hydroxyapatite (nHA, Ca10(PO4)6(OH)2) in the suspension had less significant influences on the mechanical bonding strength. It was observed that the coatings showed the excellent bonding property when an electrophoretic voltage was in a range of 40–110 V with other reagent amounts as follows: acetic acid: 4.5 vol.%, CS ≤ 0.25 g, nHA ≤ 2.0 g in 200 ml of a CS–acetic acid aqueous solution and nHA ≤ 2.5 g in 300 ml of absolute ethanol. The morphology of the composite coating obtained under the above optimal condition had a flake-like crystal structure. The EPD in the nHA/CS–acetic acid/ethanol suspension resulted in hydroxyapatite, chitosan, brushite (DCPD, CaHPO4·2H2O) and Ca(OH)2 in the coatings. After the as-prepared coating materials were immersed into PBS, Ca(OH)2 could be converted into HA and DCPD. The results of the electrochemical tests manifested that the corrosion resistance of the Mg alloy was improved by coating this composite film.
Co-reporter:Changsong Dai, Zhenyu Chen, Haizu Jin, Xinguo Hu
Journal of Power Sources 2010 Volume 195(Issue 17) pp:5775-5779
Publication Date(Web):1 September 2010
DOI:10.1016/j.jpowsour.2010.02.081
In order to search for cathode materials with better performance, Li3(V1−xMgx)2(PO4)3 (0, 0.04, 0.07, 0.10 and 0.13) is prepared via a carbothermal reduction (CTR) process with LiOH·H2O, V2O5, Mg(CH3COO)2·4H2O, NH4H2PO4, and sucrose as raw materials and investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM) and electrochemical impedance spectrum (EIS). XRD shows that Li3(V1−xMgx)2(PO4)3 (x = 0.04, 0.07, 0.10 and 0.13) has the same monoclinic structure as undoped Li3V2(PO4)3 while the particle size of Li3(V1−xMgx)2(PO4)3 is smaller than that of Li3V2(PO4)3 according to SEM images. EIS reveals that the charge transfer resistance of as-prepared materials is reduced and its reversibility is enhanced proved by the cyclic votammograms. The Mg2+-doped Li3V2(PO4)3 has a better high rate discharge performance. At a discharge rate of 20 C, the discharge capacity of Li3(V0.9Mg0.1)2(PO4)3 is 107 mAh g−1 and the capacity retention is 98% after 80 cycles. Li3(V0.9Mg0.1)2(PO4)3//graphite full cells (085580-type) have good discharge performance and the modified cathode material has very good compatibility with graphite.
Co-reporter:Zhenyu Chen, Changsong Dai, Gang Wu, Mark Nelson, Xinguo Hu, Ruoxin Zhang, Jiansheng Liu, Jicai Xia
Electrochimica Acta 2010 Volume 55(Issue 28) pp:8595-8599
Publication Date(Web):1 December 2010
DOI:10.1016/j.electacta.2010.07.068
Li3V2(PO4)3/C composite cathode material was synthesized via carbothermal reduction process in a pilot scale production test using battery grade raw materials with the aim of studying the feasibility for their practical applications. XRD, FT-IR, XPS, CV, EIS and battery charge–discharge tests were used to characterize the as-prepared material. The XRD and FT-IR data suggested that the as-prepared Li3V2(PO4)3/C material exhibits an orderly monoclinic structure based on the connectivity of PO4 tetrahedra and VO6 octahedra. Half cell tests indicated that an excellent high-rate cyclic performance was achieved on the Li3V2(PO4)3/C cathodes in the voltage range of 3.0–4.3 V, retaining a capacity of 95% (96 mAh/g) after 100 cycles at 20C discharge rate. The low-temperature performance of the cathode was further evaluated, showing 0.5C discharge capacity of 122 and 119 mAh/g at −25 and −40 °C, respectively. The discharge capacity of graphite//Li3V2(PO4)3 batteries with a designed battery capacity of 14 Ah is as high as 109 mAh/g with a capacity retention of 92% after 224 cycles at 2C discharge rates. The promising high-rate and low-temperature performance observed in this work suggests that Li3V2(PO4)3/C is a very strong candidate to be a cathode in a next-generation Li-ion battery for electric vehicle applications.
Co-reporter:Zhaohui Wen, Changjun Wu, Changsong Dai, Feixia Yang
Journal of Alloys and Compounds 2009 Volume 488(Issue 1) pp:392-399
Publication Date(Web):20 November 2009
DOI:10.1016/j.jallcom.2009.08.147
The corrosion behaviors of pure magnesium (Mg) and three Mg alloys with different Al contents were investigated in a modified simulated body fluid (m-SBF) through immersion tests, Tafel experiments, and electrochemical impedance spectroscopic (EIS) experiments. The immersion results show that the corrosion rates (CRs) of the four samples were in an order of AZ91D < AZ61 < AZ31 < pure Mg after immersion for 1 day. With an increase in immersion time, their corrosion rates decreased and then a stable stage was reached after 16 days. The order of CRs of the four samples changed to AZ91D < pure Mg < AZ61 < AZ31 after immersion for 24 days. The results of EIS experiments indicate that the charge transfer resistance (Rct) of the three magnesium alloys initially increased and then decreased while the Rct of pure Mg was kept lower within 24 h. The results of a scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) show that pure Mg and three alloys were heterogeneously corroded in the m-SBF. The corrosion of pure Mg, which showed a more uniform corrosion appearance, resulted from localized corrosion over the entire surface. Alloy AZ91D (of 8.5–9.5 wt.% Al) showed relatively uniform corrosion morphology and the β-Mg12Al17 precipitates in alloy AZ91D were more homogeneously and continuously distributed along the grain boundaries. Obvious corrosion pits were found on the surface of alloy AZ61 and AZ31. The corrosion pits of alloy AZ61 were shallower than those of alloy AZ31. Alloy AZ61 (of 5.8–7.2 wt.% Al) possessed more Al8Mn5 and a little β-Mg12Al17 presented along the grain boundary heterogeneously and discontinuously. Al8Mn5 was the main phase of the AZ31 alloy (of 2.5–3.5 wt.% Al) dispersed into the matrix. In conclusion, the microstructure and the Al content in the α-Mg (Al) matrix significantly affected the corrosion properties of the alloys in the m-SBF. With the increase in Al content, the corrosion resistances of the samples were improved.
Co-reporter:C.S. Dai, B. Zhang, D.L. Wang, T.F. Yi, X.G. Hu
Materials Chemistry and Physics 2006 Volume 99(2–3) pp:431-436
Publication Date(Web):10 October 2006
DOI:10.1016/j.matchemphys.2005.11.014
Lead (alloy) foam was prepared via electrodeposition by using copper foam as the substrate and adding element cerium to the electrodepositing solution under ultrasonic treatment. The performances and morphology of the lead foam were investigated by means of SEM and AFM. The results show that because of the addition of cerium and the application of ultrasound, the distribution thickness ratio (DTR) of the lead foam is decreased. The lead foam has a uniform three-dimensional reticulate structure with a specific surface area of about 5700 m2 m−3, a porosity of about 88.1%, and an apparent resistivity of about 150 μΩ cm−1. The results of the cyclic voltammetry indicate that the lead foam has a good stability when it is used as the negative electrode material of a lead acid battery. The battery testing revealed that, at 5, 2 h and high current discharge rates, there are improvements of 28.5%, 29.5% and 20.4% in the negative active material utilization efficiencies with the lead-foam VRLAB compared with the cast grid one and the mass specific capacities of the lead foam negative electrode are 36%, 44% and 33% higher than those of the cast grid one.
Co-reporter:Wenhui Wang, Jiaolong Zhang, Zheng Jia, Changsong Dai, Yongfeng Hu, Jigang Zhou and Qunfeng Xiao
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 27) pp:NaN13865-13865
Publication Date(Web):2014/01/30
DOI:10.1039/C3CP55495C
A series of Li3V2−2/3xZnx(PO4)3/C phases were synthesized by carbon thermal reduction assisted by the ball-mill process. Scanning electron microscopy (SEM) showed that the irregular morphology of the pristine Li3V2(PO4)3/C could be transformed to spherical upon doping with a suitable amount of zinc. The structural stability of the pristine and the Zn doped Li3V2(PO4)3/C were investigated via X-ray absorption near edge structure (XANES) spectroscopy and X-ray diffraction (XRD). The results revealed that Zn doping not only improves the stability of the VO6 octahedral structures before electrochemical cycling, but also reduces the degree of irreversible expansion of the c axis and the crystal volume upon repeated cycles. Among the Li3V2−2/3xZnx(PO4)3/C (0 ≤ x ≤ 0.15) series, the sample doped with 0.05 Zn atoms per formula unit showed the best electrochemical performance. Excess Zn doping (x > 0.05) didn't result in further improvement in the electrochemical performance due to the segregation effect and the inactive nature of Zn.
