【作者】 王高军；

【导师】 吴宇平；

【作者基本信息】 复旦大学 ， 应用化学， 2008， 博士

【摘要】 人类很早就对化学电源产生了原始的认识，但是直到1800年，意大利人Volt发明了伏打电池，人们才对电池的原理有所了解并使电池得到应用。经过铅酸电池、Ni-Cd电池、镍氢电池直到20世纪90年代初出现的锂离子电池，电池在人类的生活领域中得到了广泛的应用，对人类的发展作出了不可磨灭的贡献。同时，由于人类的不断发展，对能源的需求，环境问题的日益突出，人们对化学电源的要求也越来越高，促使人们不断探索新的化学电源和能量存储系统。本论文旨在探索新型的化学电源方面做点有益的和富有启发性的工作。锂离子电池以其能量密度高、输出电压高、自放电小、无记忆效应等优点，自1991年诞生以来，得到了非常迅速的发展。目前，锂离子电池已成为许多高附加值电子产品如移动电话、笔记本电脑、便携摄像机等的首选动力源。锂离子电池也被认为是电动汽车的理想动力源之一，受到了广泛的关注。然而锂离子电池应用于电动汽车主要受制于是否安全、价廉。最近发生的一系列笔记本电脑、手机电池爆炸的事件，不仅造成了经济上的巨大损失，也揭示了锂离子电池存在严重的安全问题。锂离子电池所用的电解液、隔膜价格比较高，其制造过程复杂，需要严格控制水份，从而导致锂离子电池的价格较高，不能满足电动汽车市场的要求。以水溶液做电解质的电池由来已久，而且种类繁多，如常用的碱锰电池、氢镍电池、镍镉电池、铅酸电池，各种空气电池等等。虽然由于受到水的电化学窗口的限制，电池的电压比较低，但是采用水溶液做电解质也具有诸多的优点，如廉价易得、导电率高、安全性好、无需无水无氧的环境、对环境友好等。能否以水溶液作为电解质制备新型的水溶液可充锂电池（简称水锂电，ARLB）?嵌锂材料在水溶液中的电化学行为如何?与在有机电解质中的行为有什么不同?虽然有少量的文献探讨了这些问题，但是研究的不系统，不深入，而且所制备的水溶液可充锂电池的性能不好，尤其是循环性能。本论文首先通过阅读相关的一些文献，进行深入的思考和理论分析，试着归纳总结出水溶液可充锂电池的理论基础以及目前存在的问题。概述了现行的储能系统，并指出储能系统的发展趋势可能是建造小规模、分散式、投资少的储能体系及其必要性。在第三章中，采用传统的固相方法合成了几种常见的电极材料，如LiCoO₂、LiMn₂O₄、LiCo_1／3Ni_1／3Mn_1／3O₂、LiFePO₄等，采用X射线衍射（XRD）分析产物的结构，证实了其结构与文献报道的结构一致；采用扫描电子显微镜（SEM）观察了产物的形貌；详细研究了它们在水溶液中的电化学性能。循环伏安的研究表明，这些材料在水溶液中都能够进行锂离子的嵌入和脱出反应。由于过电位的作用，水溶液的电化学窗口可以比理论计算的更宽，氢气和氧气的析出不影响锂离子在这些材料中的插入和脱出。另外，采用交流阻抗的技术研究了材料的阻抗和界面行为，并计算了一些动力学参数。交流阻抗的测试表明，上述的电极材料在水溶液中不能在电极表面形成表面膜，这一点与电极材料在有机电解液中的行为不同，这也是导致水溶液可充锂电池循环性能不好的原因之一。在第四章中，采用传统的固相法合成了LiV₃O₈电极材料，采用慢速循环伏安扫描对LiV₃O₈在有机电解液中的电化学行为进行研究，发现在2．25V、2．21V、1．72V（vs．Li）左右分别出现三个还原峰。表明锂离子嵌入LiV₃O₈过程中，出现三种情况；而氧化峰只有两个，分别在2．36V和2．99V（vs．Li）左右，说明锂离子从LiV₃O₈中脱出时有两种情况。恒流充放电实验表明，所合成材料的比容量为150mAh／g，比文献报道中的其它合成方法得到的材料的比容量要低，但是它的充放电可逆性非常好，其库仑效率几乎是100％，而且具有很好的循环性能，在前十次的循环过程中，容量不衰减。对LiV₃O₈在水溶液中的循环伏安实验表明，锂离子在LiV₃O₈中的嵌脱行为与在有机电解液中类似，锂离子在其中的嵌脱电位处于水的电化学窗口范围内，很适合做水溶液可充锂电池的负极材料。采用交流阻抗法研究了锂离子嵌入LiV₃O₈过程中的电极过程动力学，并计算了动力学参数。第五章在前两章研究的基础上，选择不同的材料进行组装成实验电池，不同材料间的组合可以得到电压不同的电池。本章研究了LiV₃O₈／／LiCoO₂、LiV₃O₈//LiMn₂O₄、LiV₃O₈//LiCo_1／3Ni_1／3Mn_1／3O₂、LiV₃O₈／／LiFePO₄等水锂电池的充放电行为，发现采用LiV₃O₈做为负极材料，可以得到循环性能良好的水溶液可充锂电池。其循环性能远比文献中报道的以VO₂做为负极的电池的循环性能好，目前此类电池的充放电循环次数可以达到450次以上。然而，这类电池的容量在循环过程中依然不断衰减，对其原因做了初步的分析。第六章在前面的基础上，进一步探索合适的负极材料，经过研究发现，导电聚合物中的聚苯胺、聚吡咯不仅能够用做电池的正极材料，还可以用做电池的负极材料。根据嵌入理论和导电聚合物的掺杂／去掺杂机理，提出一种具有新型工作机理的水系可充锂电池，在概念上具有很大的创新，丰富了电化学理论知识，为化学电源家族增添了新的成员。更多还原

【Abstract】 Although people knew about chemical power sources long time ago, they did not understand the principles of batteries. Batteries were not application until 1800 when Volt Batteries were invented by an Italian Volt. Batteries, varing from lead-acid battery, Ni-Cd battery, nickel-metal hydride battery to lithium ion battery which was born in 1991, have been applied to broad fields in people’s lives and are quite significant to the development of society. Meanwhile, in response to the needs of modern society and emerging ecological concerns, it is essential to find new chemical power sources and energy storage systems. This paper aims to explore innovative chemical power sources.Rapid development has been achieved for LIBs since its birth in 1991, due to their advantages of high energy density, high output voltage, little self-discharge and no memory effect. It has been widely used not only in electronic devices, such as mobile phone, lap-top, portable camera, but also in some important fields for the contries’ development, such as transportation, military weapons, aerospace and so on. What is more, it is significant to develop electronic vehicles （EVs） to deal with problems caused by energy shortage and pollution. Lithium ion batteries are one of the most promising power sources for EVs. However, the further application of LIBs in EVs has been hindered by its safety and high price. For the commercial LIBs at present, carbon is used for anode and LiCoO₂ for cathode, with great amount of organic electrolyte. The organic electrolyte could cause combustion or even explosion due to improper usage. Such cases happened in Dell and Nokia products, gave rise to - large loss to the companies. And the safety problem would be more serious when adopting LIBs for EVs. Besides, high price of electrolyte and seperating membrane, complex process of organic electrolyte preparation and strict control of moisture, give rise to high price of LIBs.Various kinds of batteries with aqueous electrolyte have been researched since long time ago, such as alkaline manganese batteries, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid batteries, air batteries, and so on. Although there are still some limits for batteries with aqueous electrolyte, such as narrow electrochemical window, low voltage, they present a lot of advantages compared with organic electrolytes, such as low cost, easy preparation, high conductivity, safety, no restrict of moisture or oxgen, environmental evrionmental friendliness and so on. Efforts were made to develop aqueous reversible lithium ion batteries （ARLB） in previous work. However, there is no systematic and further deep investigation, in terms of electrochemical activities of Li-acitive materials in aqueous electrolyte, differences of their performance between in organic and aqueous electrolytes. Moreover, electrochemical performance of ARLB reported in the previous literatures needs further improvement, especially for its cycle performance.In chapterⅢ, Several electrode materials were synthesized by solid-state method, such as LiCoO₂, LiMn₂O₄, LiCo_1/3Ni_1/3Mn_1/3O₂, LiFePO₄, LiV₃O₈, and so on. XRD and SEM were used for the characteristic analysis of these materials mentioned above. XRD results reveal that the diffraction peaks are consistent to the previous reports. Cyclic Voltammogram（CV）, charge and discharge test system, and EIS were adopted to investigate their electrochemical performance. CVs present that all the materials mentioned can accommodate lithium in aqenous electrolyte. Because of the over-potential effect of the electrode, electrochemical window is wider compared with that of calculated theoretically. The oxygen and hydrogen do not affect insertion and extraction reaction into the electrode materials. By adjusting pH value, the electrochemical window could be adjusted, and more materials could be used in ARLB. Besides, results from ARLB indicate that there is no SEI film formed on the surface of the electrode materials, which is quite different from the phenomenon in organic electrolyte. We suppose that it is the explanation to that the poor cycle performance of ARLB.In chapterⅣ, LiV₃O₈ electrode material was synthesized by the traditional solid-state method. The result of slow scan cyclic voltammetry of LiV₃O₈ in organic electrolyte reveals that there are three redox peaks on the curve, i.e. 2.25 V, 2.21V and 1.72V （ vs. Li）, respectively, suggesting that there are three phase transition when lithium ions insert into LiV₃O₈, and only two oxidation peak, 2.36 V and 2.99 V （vs. Li） when lithium ions extract from LiV₃O₈. The results of constant current charge-discharge experiments show that the capacity of LiV₃O₈ is 150 mAh /g. The capacity is lower than that of LiV₃O₈ prepared by other methods reported in literature. However, its charge-discharge reversibility is very good and the coulombic efficiency is almost 100 percent. The as-prepared material has good cycling performance. The capacity did not decay during the first 10 cycles. The cyclic voltammetry experiments of LiV₃O₈ in aqueous solution showed that the behavior of lithium ion insertion/extraction in the LiV₃O₈ is similar with that in organic electrolyte. LiV₃O₈ is suitable for aqueous lithium rechargeable battery anode material because of the redox peaks potential of lithium-ion intercalated/deintercalated into and from LiV₃O₈ in aqueous solution within the electrochemical window of water. AC impedance method was employed to investigated the kinetics of lithium ion insertion in LiV₃O₈ and the kinetic parameters were calculated.In chapterⅤ, on the basis of the research above, we chose various materials to fabricate batteries with different voltages. The systems we investigated in this chapter are listed as following: LiV₃O₈//LiCoO₂, LiV₃O₈//LiMn₂O₄, LiV₃O₈// LiCo_1/3Ni_1/3Mn_1/3O₂, LiV₃O₈// LiFePO₄. We find that the batteries with LiV₃O₈ as anode materials present excellent cycle performance, which could cycle for 450 times without serious capacity fading. However, the capacities of above cells still decay with long charge/discharge cycle. The reasons were analyzed in this chapter.In chapterⅥ, We further investigated proper anode materials, and found that some conductive polymer such as polyaniline and polypyrrole, could used not only as cathode materials, but also as anode. For the first time, we proposed a new mechanism of ARLB based on intercalation theory and doping mechanism. The mechanism we proposed is a great innovation in electrochemisty.更多还原