Electrochemical Characterization of Surface-modified LiMn2O4 Cathode Materials for Li-ion Batteries

To improve the performance, the surface of 12Mn2O4 was coated with very fine MgO , Al2O3 and ZnO by solgel method, respectively. The structure and morphology of the coated materials were investigated by X-ray diffraction （ XRD ）, X-ray photoelectron spectroscopy （ XPS ） and scanning electron microscopy （SEM）. The charge and discharge performance of uncoated and surfnce modified 12Mn2O4 spinel at 25℃ and 55 ℃ were tested, using a voltage window of 3.0-4.35 V and a current deasity of 0. 1 C rate. There is a slight decrease in the initial discharge capacity relative to that of uncoated UMn2 O4, bat the cycle ability of 12 12Mn2O4 coated by metal-oxide has remarkably been improved. The EIS measuremeuts of uncoated and Al2O3 -coated 12Mn2O4 were carried out by a model 273 A potentiostatl galvanistat controUed by a computer using M270 software, and using a freqnency response analyzer （ Zsimpwin ） combined with a potentiostate （ PAR 273）. Coaseqnently, the reason for the improved cycle properties is that the surface modification reduces the dissolution of Mn , which results from the suppression of the electrolyte decomposition, and suppresses the formation of passivation film that acts as an electronic insulating layer. In conclusion, the use of surface modification is an effective way to improve the electrochemical performance of 12Mn2O4 cathode material for lithium batteries.     

铝电池的开发与应用进展

铝元素在地壳中的储量丰富,来源广泛,并且金属铝的安全性高,在离子电池领域中具有广阔的应用前景.尽管铝金属在离子电池中具有如此诱人的优势,但铝离子电池的能量密度、稳定性以及所使用的电解液安全性和成本依然制约其发展.对铝离子电池的最新工作进行梳理、分析和总结,并进一步探讨其作为新型储能体系的机遇和挑战.主要从正极材料、电解液及铝金属负极3个方面对近期的铝离子电池相关工作进行了总结,为开展高能量密度、高稳定性铝离子电池的研究奠定基础.

     

Cu2O nanowires as anode materials for Li-ion rechargeable batteries

Li-ion batteries are a key technology for multiple clean energy applications.In this study,Cu2O nanowires were obtained by the reduction of cupric acetate with pyrrole.The resulting Cu2O nanowires exhibited excellent reversible capacities of 470mAh g-1 at rate of 1 C after 100 cycles.The results show that the Cu2O nanowires had more capacity than materials previously reported.No fading was observed over 100 cycles of charging and discharging.The compound metal Cu and incorporation of the conducting polymer polypyrrole(PPy)improved the conductivity of Cu2O and enhanced the stability of the electrode during cycling.The results from this study imply that Cu2O nanowires with high capacity and good cycle retention could be excellent candidates as anode materials for Li-ion rechargeable batteries.     

新型锂储藏合金负极材料研究进展

合金型锂离子电池负极材料由于容量高、安全性好而受到了极大的关注，最有希望取代碳材料在下一代高性能锂离子电池中得到应用．笔者着重介绍了以锡合金为代表的锂储藏合金的研究进展，以及最新的纳米技术和薄膜技术在研究过程中的应用．由于新技术的应用，解决了合金材料在充放电过程中由于体积膨胀而粉化的缺点，锂储藏合金材料的研究取得了突破性的进展，循环寿命已经达到了300周以上，离实际应用仅一步之遥．锡基合金负极材料是最有竞争力的下一代锂离子电池负极材料之一。     

Chemical extraction preparation of delithiated cathode materials of Li-ion battery

A method of conventional chemical reaction to prepare delithiated cathode materials of Li-ion battery was introduced. The cathode material of Li-ion battery was mixed with oxidizing agent Na₂S₂O₈ in water solution, and the solution was stirred continuously to make the chemical reaction proceed sufficiently, then the reaction product was filtered and finally the insoluble delithiated cathode material was obtained. A series of tests were conducted to verify the composition, crystal structure and electrochemical property of the delithiated cathode materials were all desirable. This method overcomes the shortcomings of battery charging preparation and chemical extraction preparation employing other oxidizing agents.     

低成本动力锂离子电池磷酸铁锂正极材料的合成及性能

磷酸铁锂作为动力锂离子电池的正极材料的首选,正逐渐走向市场.以廉价的Li₃PO₄,FePO₄,Fe粉为原料,一步合成了LiFePO₄/C正极材料,系统研究了葡萄糖、蔗糖和柠檬酸三种不同的碳源对磷酸铁锂性能的影响.采用TG-DTA,XRD,SEM,TEM等手段对产物进行了表征,并研究了其电化学性能.实验结果表明,以葡萄糖为碳源的LiFePO₄/C性能最好,样品颗粒呈球形,表面光滑,分散性好,颗粒表面包覆有2 nm厚的石墨碳层,颗粒之间有碳纤维连接.该样品在0.1 C充放电时首周放电容量达到162.1 mAh/g,20周之后仍然保持在155 mAh/g,显示出良好的循环性能.     

A Novel Modification Approach for Natural Graphite Anode of Li-ion Batteries

To improve the rate caqability and cyclability of natural graphite anode for Li-ion batteries, a novel modifwatio, approach was developed. The modification approach included two steps:(a) high-energy ball milling in a rotary aatoelave containing alumina balls, H3PO4 and ethanol;( b ) coating with pyrolytic carbon from phenlic resin. The treated graphite sluws obrious improvement compared with the original natural graphite in electroehemical properties such as cyclahility and rate capability, especially at high current density. The primaryreasons leading to the improvement in rate capability and cyclability are that the diffusion impedance of Li^ in graphite is reduced due to the fact that P filtered into graphite layers can mildly increase interlayer distances, and the fact that the structural stability of graphite surface is enhanced since the coated pyrolytic carbon can depress the co-intercalation of solvated lithium ion.     

5V锂离子电池正极材料的制备和电化学性能研究

用液相法合成出用锂和镍取代的尖晶石锂锰氧化物正极材料.用XRD和FTIR对其进行了表征,并探讨了其在有机电解液的电化学性能.研究结果表明:在锂锰氧化物掺入适量的镍(锰∶镍的摩尔比为1.4∶0.6)可以改善尖晶石LiMn2O4的循环性能,提高放电平台,使其大部分容量往高电位方向移动,电池的放电电压提高,这样的材料适合做5V电池的正极材料.     

储能电池用空心介孔碳/硫复合正极材料的制备及性能改进

针对高比能二次电池中,锂硫电池在反应过程中出现的中间产物溶解流失及体积膨胀等问题,采用模板法制备了一种具有空心结构的高孔容介孔碳球(标记为SiO_2~-空心碳),不仅提高了载硫量,而且可将多硫化物吸附在球体的空心结构和壳层的介孔孔隙中,从而抑制活性物质的溶解流失。扫描电子显微镜(SEM)和透射电子显微镜(TEM)、氮气吸脱附表征结果表明多孔碳呈空心球结构,壳层布满介孔孔隙,孔径约为2～4 nm; X-射线衍射(XRD)图谱说明单质硫均匀分散在空心碳孔隙结构中;热重分析结果显示,SiO_2~-空心碳/S复合材料的硫含量为74. 2%;电化学测试表明,其首周放电比容量增加至1608. 6(mA·h·g~(-1)),循环100周后仍保持在863. 4(mA·h·g~(-1))以上,说明SiO_2~-空心碳/S复合材料具有较好的电化学活性及循环稳定性。采用KS6为导电剂,可以使复合硫电极循环100周后的可逆比容量提高至961(mA·h·g~(-1)),容量保持率提高至61. 7%,可见KS6导电剂可以明显改善SiO_2~-空心碳/S复合材料的循环性能。     

Mild oxidation treatment of graphite anode for Li-ion batteries

1　INTRODUCTIONNumerous carbonaceous materials have beeninvestigated as anodes of lithium ion batteries dur ing the past several years[1 4]. Graphite is an at tractive material for anodes of lithium ion batteriesdue to its high reversible capacity (372 mA·h/g intheory), low and flat discharge potential (0.1 0.2 Vvs. Li)[5 8]. However, there are still some prob lems for the graphite in the application with respectto a low practically available capacity, and a largeir…     

Synthesis and properties of Li<Subscript>2</Subscript>MnSiO<Subscript>4</Subscript>/C cathode materials for Li-ion batteries

Carbon was coated on the surface of Li₂MnSiO₄ to improve the electrochemical performance as cathode materials, which were synthesized by the solution method followed by heat treatment at 700 °C and the solid-state method followed by heat treatment at 950 °C. It is shown that the cycling performance is greatly enhanced by carbon coating, compared with the pristine Li₂MnSiO₄ cathode obtained by the solution method. The initial discharge capacity of Li₂MnSiO₄/C nanocomposite is 280.9 mAh/g at 0.05 C with the carbon content of 33.3 wt%. The reasons for the improved electrochemical performance are smaller grain size and higher electronic conductivity due to the carbon coating. The Li₂MnSiO₄/C cathode material obtained by the solid-state method exhibits poor cycling performance, the initial discharge capacity is less than 25 mAh/g.     

The strategies of advanced cathode composites for lithium-sulfur batteries

Lithium-sulfur batteries have been widely nominated as one of the most promising next-generation electrochemical storage systems due to its low cost, high capacity and energy density. However, its practical application is still hindered by poor cycling lifetime, low Coulombic efficiency, instability and small scales. In the last decade, the electrochemical performances of the lithium-sulfur batteries have been improved by developing various novel nanoarchitectures as qualified hosts, and enhancing the sulfur loading with effective encapsulating strategies. The review summarizes the major sulfur cooperating strategies of cathodes based on background and latest progress of the lithium-sulfur batteries. The novel cooperating strategies of physical techniques and chemical synthesis techniques are discussed in detail. Based on the rich chemistry of sulfur, we paid more attention to the highlights of sulfur encapsulating strategies. Furthermore, the critical research directions in the coming future are proposed in the conclusion and outlook section.     

Purification process of coal-based coke powder as anode for Li-ion batteries简

A process of purification of coal-based coke powder as anode the treatment of coke powder with dilute hydrofluoric acid solution, for Li-ion batteries was attempted. The process started with followed by united-acid-leaching using sulfuric acid and hydrochloric acid. The effects of altering the hydrofluoric acid addition, hydrofluoric acid concentration, contact time, temperature and acid type were investigated. A minimum ash content of 0.35% was obtained when proper conditions were applied. The electrochemical performance of purified coke powder shows greatly improved electrochemical performance. The as-purified coke powder presented an initial reversible capacity of 257.4 mAh/g and a retention rate of 95% after 50 cycles. The proposed purification process paves a way to prepare a promising anode material with good performance with low cost of coke powder for Li-ion batteries.     

Damage and fracture with strain gradient plasticity for high-capacity electrodes of Li-ion batteries

Science China Technological Sciences - In consideration of the high-density dislocations from the lithiation process of high-capacity electrodes in Li-ion batteries, in this paper, a new...     

锂离子电池正极材料LiMn0.95Zn0.05PO4/C的固相合成及电化学性能

以PEG为新型碳源,采用简单固相法合成了锌离子掺杂的锂离子电池正极材料LiMn0.95Zn0.05PO4/C。采用XRD和电化学测试分别研究了预分解温度对LiMn0.95Zn0.05PO4/C结构及性能的影响。实验结果表明预分解温度为500℃合成的LiMn0.95Zn0.05PO4/C具有最好的放电性能,0.02 C首次放电比容量可以达到131.7 mA.h.g-1,达到文献较好水平。考察了最佳条件合成样品的倍率性能和循环伏安特性。     

Preparation and electrochemical studies of Y-doped LiVPO<Subscript>4</Subscript>F cathode materials for lithium-ion batteries

Y-doped LiVPO₄F cathode materials were prepared by a carbothermal reduction(CTR) process. The properties of the Y-doped LiVPO₄F samples were investigated by X-ray diffraction (XRD) and electrochemical measurements. XRD studies show that the Y-doped LiVPO₄F samples have the same triclinic structure as the undoped LiVPO₄F. The Li extraction/insertion performances of Y-doped LiVPO₄F samples were investigated through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Y is x=0.04 in LiY _x V_1−x PO₄F system. The Y-doped LiVPO₄F samples show a better cyclic ability. The electrode reaction reversibility is enhanced, and the charge transfer resistance is decreased through the Y-doping. The improved electrochemical performances of the Y-doped LiVPO₄F cathode materials are attributed to the addition of Y³⁺ ion by stabilizing the triclinic structure. Funded by the Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning(GuiJiaoRen [2007]71), Guangxi Natural Science Foundation(No.0832259), the Research Funds of the Guangxi Key Laboratory of Environmental Engineering, Protection and Assessment Program to Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning(GuiJiaoRen [2007]71)     

Synthesis and characterization of triclinic structural LiVPO4F as possible 4.2 V cathode materials for lithium ion batteries

A potential 4.2 V cathode material LiVPO4F for lithium batteries was prepared by two-step reaction method based on a carbon-thermal reduction （CTR） process. Firstly, V2O5, NH4H2PO4 and acetylene black are reacted under an Ar atmosphere to yield VPO4. The transition-metal reduction is facilitated by the CTR based on C→CO transition. These CTR conditions favor stabilization of the vanadium as V^3＋ as well as leaving residual carbon, which is useful in the subsequent electrode processing. Secondly, VPO4 reacts with ElF to yield LiVPO4F product. The property of the LiVPO4F was investigated by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and electrochemical measurement. XRD studies show that LiVPO4F synthesized has triclinic structure（space group p I ）, isostructural with the naturally occurring mineral tavorite, EiFePO4-OH. SEM image exhibits that the particle size is about 2μm together with homogenous distribution. Electrochemical test shows that the initial discharge capacity of LiVPO4F powder is 119 mA·h/g at the rate of 0.2C with an average discharge voltage of 4.2V （vs Ei/Li^＋）, and the capacity retains 89 mA·h/g after 30 cycles.     

Synergetic effects of blended materials for Lithium-ion batteries

LiNi_1/3Co_1/3Mn_1/3O₂, LiMn₂O₄ and LiCoO₂ are paired to make the blended materials for the cathode of lithium-ion batteries. The factors impacting on the characteristics of blended materials are studied using constant current charge/discharge measurement and electrochemical impedance spectroscopy. The results show that the three pairs of blended materials exhibit very different synergetic effects in high C-rate discharging. The mechanism of particle synergetic effect has a physical root on the compensating material property of blending components, which fundamentally correlates with their similarity and difference in crystalline and electronic structures. The AC impedance show the obvious changes that alternate the high C-rate performance, due to reduced particle impedance in blended materials. The pairs of LiNi_1/3Co_1/3Mn_1/3O₂-LiMn₂O and LiCoO₂-LiMn₂O₄ present obvious increases in high C-rate reversible capacities than does the pair LiCoO₂-LiNi_1/3Co_1/3Mn_1/3O₂.     

Synthesis and electrochemical properties of polyradical cathode material for lithium second batteries

A stable polyradical, poly (2 ,2,6,6-tetramethylpiperidinyloxy methacrylate)(PTMA) , was synthesized, and its structure was determined by infrared, ultraviolet-visible, and ESR spectroscopy. Cyclic voltammograms of the PTMA polyradical electrodes were obtained by using a three-electrode cell at a scan rate of 5 mV/s within a potential range of 3. 2-4. 0 V. The results show that the shape of oxidation peak is very similar to that of reduction peak, and oxidation peak current is equal to the corresponding reduction peak current, which suggest that PTMA possesses an excellent reversibility. The difference of the anodic peak potential (Ea,p = 3. 66 V, vs Li/Li+) and ca-thodic peak potential(Ec,p = 3. 58 V, vs Li/Li+ ) is estimated at 80 mV, which is extremely less than that of the other organic positive materials in lithium second batteries such as organosulfide compounds, leading to a capability for high current capability in the charging and discharging process of the battery. The maximum discharge specif