Electrochemical Conversion Reactions and Their Applications for Rechargeable Batteries

电化学转换反应作为一种新的电极反应机制，近年来受到相当多的关注. 转换反应不仅能够利用金属化合物的多价态氧化还原，大幅度提高电化学容量利用率，而且对于主体晶格的结构、嵌脱阳离子的尺寸并无特殊要求，可以应用于众多不同种类的金属化合物，针对不同的金属离子设计高容量正负极活性材料. 因此，基于转换反应构建高容量电极材料正成为二次电池发展的一个新方向. 本文简要分析了电化学转换反应的基本原理和实现条件，并结合作者课题组近年来的研究工作探讨了这类反应在锂离子及钠离子电池中的潜在应用.Electrochemical conversion reactions have received considerable interest as a new redox mechanism for constructing high capacity electrodes of rechargeable batteries. Without strict restrictions on the crystalline structure of the host lattice and the size of the associated ions, conversion reactions can take place in a variety of different metal compounds with different metal cations and deliver much higher reversible capacities through full utilization of all the oxidation states of the transition-metal compounds, opening up a new avenue for developing high capacity materials of rechargeable batteries. This paper briefly reviews the state of the art and challenges of conversion electrodes and also discusses the possible strategies for realizing high efficient electrochemical conversions and for establishing advanced Li-ion and Na-ion batteries.国家自然科学基金青年项目（No. 21403305）资助作者联系地址：1. 中南民族大学化学与材料科学学院，湖北 武汉 430074；2. 武汉大学化学与分子科学学院，湖北 武汉 430072Author's Address: 1. College of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan 430074, China; 2. Department of Chemistry, Wuhan University, Wuhan 430072, China通讯作者E-mail：[email protected]

Electrochemical Conversion Reactions and Their Applications for Rechargeable Batteries

电化学转换反应作为一种新的电极反应机制，近年来受到相当多的关注. 转换反应不仅能够利用金属化合物的多价态氧化还原，大幅度提高电化学容量利用率，而且对于主体晶格的结构、嵌脱阳离子的尺寸并无特殊要求，可以应用于众多不同种类的金属化合物，针对不同的金属离子设计高容量正负极活性材料. 因此，基于转换反应构建高容量电极材料正成为二次电池发展的一个新方向. 本文简要分析了电化学转换反应的基本原理和实现条件，并结合作者课题组近年来的研究工作探讨了这类反应在锂离子及钠离子电池中的潜在应用.Electrochemical conversion reactions have received considerable interest as a new redox mechanism for constructing high capacity electrodes of rechargeable batteries. Without strict restrictions on the crystalline structure of the host lattice and the size of the associated ions, conversion reactions can take place in a variety of different metal compounds with different metal cations and deliver much higher reversible capacities through full utilization of all the oxidation states of the transition-metal compounds, opening up a new avenue for developing high capacity materials of rechargeable batteries. This paper briefly reviews the state of the art and challenges of conversion electrodes and also discusses the possible strategies for realizing high efficient electrochemical conversions and for establishing advanced Li-ion and Na-ion batteries.国家自然科学基金青年项目（No. 21403305）资助作者联系地址：1. 中南民族大学化学与材料科学学院，湖北 武汉 430074；2. 武汉大学化学与分子科学学院，湖北 武汉 430072Author's Address: 1. College of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan 430074, China; 2. Department of Chemistry, Wuhan University, Wuhan 430072, China通讯作者E-mail：[email protected]

Electric Vehicles and Power Batteries

通过回顾电动汽车一百多年的发展历史，讨论了化学电源技术对电动汽车发展的影响。在简要介绍电动汽车种类和电动汽车对动力电池的技术要求之后，围绕动力锂离子电池应用的主要问题进行了讨论，包括电池安全性、环境适应性和成本。最后，简单分析了未来动力电池技术的发展之路。In retrospect of the historical development of Electric Vehicles (EV), the impact of battery technologies on the progress of EV was discussed. In consequence, it is concluded that the lack of advanced batteries was the main cause for the fluctuations of EV development and the sluggish commercialization of electric cars in the past century. After a brief introduction to the classification and the requirements of electric vehicles, the main issues of the batteries including safety, temperature range for operation and the cost as well as the effects of these factors on the applications of advanced batteries for electric vehicles were discussed. Finally, the hot areas for future development in EV battery technologies were discussed.国家973计划（No. 2009CB220103）、863计划（No. 2007AA03Z224），以及中央高校基本科研业务费专项资金（203275672）作者联系地址：湖北省化学电源材料与技术重点实验室，武汉大学化学与分子科学学院，湖北，武汉430072Author's Address: Department of chemistry, Hubei key lab. of electrochemical power, Wuhan university, Wuhan, 43007

Multi-electron Redox Materials for High Energy Density Electrodes

正在崛起的新能源技术为化学电源的发展提供了巨大机遇,同时也提出了巨大的技术挑战:即在现有基础上大幅度提升能量和功率密度,以满足各个层次高效储电的要求.利用多电子反应电池体系是成倍提高化学电源能量密度的有效途径.本文以作者所在课题组的研究工作为主,简要介绍了几类典型的多电子电极反应,包括金属硼化物多电子氧化反应、合金储锂反应、高价金属化合物结构转化反应等,以及这些反应体系用于构建高能量密度电池的关键问题,并试图分析解决这些问题的可能技术途径.Various new energy technologies being developed require electrochemical energy batteries to have a real breakthrough in energy density and rate capability,which imposes a great challenge for electrochemists and materials chemists. Multi-electron redox reactions seem to open a promising avenue to create new batteries with dramatically enhanced energy densities. This paper describes simply our research works on the multi-electron redox systems,including metal boride anode,lithium alloying compounds and electrochemical conversion materials, and also discusses the problems hindering these systems for battery applications.作者联系地址：湖北省化学电源材料与技术重点实验室,武汉大学化学与分子科学学院;Author's Address: Hubei Key Lab of Electrochemical Power Sources,College of Chemistry and Molecular Sciences, Wuhan University,Wuhan 430072,Chin

A Investigation of Hydrogen-storage Alloy as Catalytic Electrode for Hydrogenation of Nitrobenzene

贮氢合金用作硝基苯电解加氢的催化电极研究卢世刚，杨汉西，王长发（武汉大学化学系，武汉１３００７２）混合稀土贮氢合金是近年来发展起来的新型功能材料。在室温下它可以吸收比自身体积大几百倍的氢原子形成金属氢化物．这种金属氢化物可作为氢源提供高反应活性的氢原...Since hydrogen.storage alloy ean not only absorb hydrogen atoms to form highlyreactive metal hydride as hydrogen source by electrolysis but also possesses a certain catalytic activityfor hydrogenation,it is thus feasible to utilize the allov as a novel electrOde for electrolvtichydrogenation in organic electrored uction. This work employed misch metal AB_5 type alloy as acatalytic electrode and studied the electrochemical hydrogenation of nitrobenzene. The hydrogen-storage electrede(MH)was a plastic bonded electrede sheet made from a paste ofMm(NiCoMnAl)_5 alloy powder and teflon emulsion. The electrolysis was performed at constantcurrent and controlled potential in a three electrede cell of H-type configuration. The electrolyte was0.5 mol/L KOH aqueous solution and 0.5 mol/L KOH in CH_3OH+H_2O(80:20 by vol.). Changes in the concentrations of nitrobenzene(NB)and its reaction pred ucts were monitored bysampling at different d uration of electrolysis and then analysed by HPLC and UV spectroscopy. The CV cruve of a powder microelectrode of hydrogen-storage alloy in alkaline solution showed apair of distinct oxidation-reduction current peaks of hydride formation at E=-1.1V and hydrogendesorption at E=-0.9V.In addition of NB, a strong reduction peak appeared at E=-0.7 V oncathodic scan,and the anodic peak of hydride oxidation completely disappeared on reverse scan tosuggest the participation of absorbed hydrogen in the NB red uction(Fig.3). In the electrolysis of NB-saturated alkaline solution,we used UV spectroscopy monitoring the compositional changes of theelectrolvte. It was found that with increasing the electrolysis time the concentration of NB dropedsteadily and instead the concerntration of the main product aniline (AN)went up contineously as seenby the decreasing 278 nm and increasi ng 230nm UV peaks both characteristic of nitrobenzene andaniline. By HPLC seperation and analyse of the electrolyte after electrolysis,the electrolysis yield ofAN reached up to 90%and the current efficiency calculated also exceeded 85%. Except for a verysmall amount of azoxvbenzene and azobenzene(totally about 2%content)there were no any otherside reaction products or intermediates found in the course of electrolysis,indicating the high selectivityof MH electrede for nitrobenzene hydrogenation. In order to increase the dissolubility of NB in electrolyte,we tried to use the methanol-watermixed solvent instead of aqueous solvent for the electrolytic hydrogenation of NB. In the case of usingthe mixed solvent,the main electrolysis preduct was still AN,and the AN yield and current efficiencywere 86%and 85%both almost equal to the values measured in alkaline solution. Comparising of theMH electredes before and after electrolvsis there were no any discernible changes observed in thehydrogen-storage capacity and charge-discharge properties,suggesting a quite catalytic stability in theorganic media. In summay it could be concluded that the use of MH electrode in the electrochemicalhydrogenation of nitrobenzene offers a number of advantages of high selectivity,high currentefficiency and excellent catalytic stability,this shows a great promise for ind ustrial applications.作者联系地址：武汉大学化学系Author's Address: Department of Chemistry, Wuhan University, Wuhan 43007

Simple Analysis and Possible Solutions of the Unusual Interfacial Reactions in Li-S batteries

锂-硫电池是在现有锂离子电池基础上最可能实现储能密度大幅提升的实用二次电池体系. 然而，这一电池体系的电化学利用率与循环稳定性仍然难以满足应用要求. 造成锂-硫电池性能不稳定的原因在于硫正极和锂负极的材料结构和反应环境始终处于变化之中，如在充放电过程中，硫-碳反应界面的电化学阻塞、中间产物的溶解流失、正负极之间的穿梭效应等副反应导致正极与负极均难形成稳定的电化学反应界面。针对这些特殊问题，本文简要分析了影响能量利用率和循环稳定性的化学与电化学机制，并提出了构建稳定锂负极与高效硫正极的若干可行性技术.Rechargeable Li-S batteries are a promising power source with realizable energy densities several times higher than current Li-ion batteries. However, the capacity utilization and cycling stability of the existing Li-S technologies are still insufficient for battery applications. The causes for the electrochemical instability of this redox system arise probably from the changes in the surface structures and electrochemical microenvironments of the Li anode and sulfur cathode during charge-discharge reactions, which includes the frustrated electron transfer in the sulfur-carbon interface, the dissoluble diffusion of the polysulfide intermediates, and the shuttle reaction inbetween the sulfur and Li electrodes. To deal with these problems, this paper tries to reveal the underlying chemistry affecting the charge-discharge stability of Li-S system and describe possible strategies to construct electrochemically stable Li anode and sulfur cathode, so as to achieve high efficiency Li-S batteries.国家973计划项目（No. 2009CB220103）资助作者联系地址：武汉大学化学与分子科学学院，湖北 武汉 430072Author's Address: College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, Hubei, China通讯作者E-mail：[email protected]

Self-activating Safety Mechanisms for Li-ion Batteries

安全性问题是阻碍大容量和高功率锂离子动力电池应用的关键.本文以作者课题组近期研究工作为主,简要介绍了几种旨在提高锂离子电池安全性的自激发安全保护机制,包括氧化还原穿梭剂、电压敏感隔膜、温度敏感电极、阻燃性电解液,并分析了这些方法的应用特点.The safety concerns of LIBs are considered to be a main obstacle to their high rate or large capacity applications in electric vehicles.This paper describes briefly our research works on the development of self-activating safety mechanisms for LIBs,including redox shuttle,potential-sensitive separator,temperature-sensitive electrode,and fire-retardent electrolyte.The problems and future in this research area are also discussed.作者联系地址：湖北省化学电源材料与技术重点实验室武汉大学化学与分子科学学院;Author's Address: College of Chemistry and Molecular Sciences,Hubei Key Lab.of Eletrochemical Power Sources,Wuhan University,Wuhan 430072,Chin

Electrochemical Na-Storage Materials and Their Applications for Na-ion Batteries

大规模储能的二次电池不仅需要具有适宜的电化学性能，更需考虑资源、成本和环境效益等应用要求. 锂离子电池储能的大规模应用也将受到制约. 从资源与环境方面考虑，钠离子电池作为储能电池更具应用优势. 然而，从目前的技术现状来看，几类不同的嵌钠正极材料虽显现出可观的嵌钠容量与较好的循环性，但能量密度与功率密度尚待提高. 硬碳材料和合金负极最有希望用于钠离子电池，这类材料的初始充放电效率和循环稳定性仍有待改善. 本文简要分析了锂离子电池与钠离子电池在材料要求方面的差异，回顾了近年来钠离子电池材料探索中的突破性进展，并主要结合本课题组的研究工作讨论了钠离子电池及其关键材料的发展方向.Oncoming large scale electric energy storage (EES) requires battery systems not only to have sufficient storage capacity but also to be cost-effective and environmentally friendly. Li-ion batteries for widespread EES applications may be limited due to the constraint of global lithium resource. From the considerations of available resources and environmental impact, Na-ion batteries have potential advantages as next generation secondary batteries and an alternative to Li-ion batteries. However, in the present state of the art, the Na-storage cathodes reported so far are still deficient both in energy density and power capability, while the carbon and alloy anodes for Na-ion batteries have also the problem of insufficient cycling life for battery applications. This paper reviews briefly the recent advances in the development of Na-storage materials, analyses the different structural requirements for the materials in Li-ion and Na-ion batteries and discusses the possible strategies for development of low cost and pollution-free materials for rechargeable Na-ion batteries.国家973计划项目（No. 2009CB220103）和国家自然科学基金项目（No. 21273167）资助作者联系地址：1. 武汉大学化学与分子科学学院，湖北 武汉 430072；2. 南开大学新能源材料化学研究所，天津 300071Author's Address: 1. Department of Chemistry, Wuhan University, Wuhan, 430072，Hubei, China; 2. Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China通讯作者E-mail：[email protected]

A Study of Metal Borides as High Capacity Anode Materials for Aqueous Primary Batteries

　碱性溶液中,VB2和TiB2分别发生了 11电子和 6电子氧化反应,释放出 3 100mAh/g和 1 600mAh/g的超常电化学容量.对此,初步的解释是:在二硼化物中过渡金属与硼的电子转移使硼元素电负性增强,引起硼的电化学活化.使得合金的电极电势钳制在较负区域,导致某些过渡金属元素处于活化态,进而发生电化学氧化释放出电化学能量.The transition metal borides VB_2 and TiB_2 were tested as high capacity anode materials and their electrochemical behaviors were studied by cyclic voltammetry and discharge measurements. The experimental results indicated that transition metal borides VB_2 and TiB_2 electrodes can deliver exceptionally high discharge capacity of over 3100 mAH/g and 1 600 mAH/g respectively, corresponding to 11- and 6-electron oxidation reaction, although their parent elements V, Ti and boron, are almost completely electrochemically inert. The different electrochemical activitis were probably due to the electrochemical activation of boron, which clamp the potential to passivation for Ti and activity for V.作者联系地址：武汉大学化学与分子科学学院,武汉大学化学与分子科学学院,武汉大学化学与分子科学学院 湖北武汉430072 ,湖北武汉430072 ,湖北武汉430072Author's Address: *Department of Chemistry, Wuhan University, Wuhan 430072, Chin