The Study on the Amorphous Oxides as Cathodes for Lithium Secondary Battery

从发展实用锂二次电池的角度出发，对各种正极、负极和电解质材料进行了研究。作为每个课题的主题，我们分别选择了(1)基于Cr_3O_8和V_2O_5的非晶态氧化物的研究，(2)开发替代LiClO_4的盐电解质，(3)锂-碳复合电极作为锂二次电池负极的研究。本项目期间的研究结果如下。(1)由Cr_3O_8晶体制备的非晶态Cr_3O_8具有优异的性能。它具有高能量密度、高功率密度和良好的可循环性。由于其无定形结构，其势能被扁平化，放电过程非常顺利，放电均匀。这种化合物的问题之一是很难使每个Cr_3O_8颗粒精细。这导致在高倍率放电时充放电特性变差。铜银矿型化合物CuV_<2-x>Mo_xO_6也表现出良好的循环性。此外，还有一个有趣的特征，即锂和铜的插入和脱嵌同时发生在交替的方向上。富钒组分与富钼组分相比具有非晶结构，并表现出良好的充放电特性。(2)在电流密度和可循环性方面，LiPF_6在PC: DME（1:1）电解质中的性能在所有电解质中最好。(3)锂碳复合电极抑制了锂基体上锂枝晶的形成。锂和碳之间的反应取决于碳的结构，即结晶度、取向等。结晶度越高，表明锂的容纳量越大。结果表明，碳晶体的取向对锂的插层速率有较大的影响。在此基础上，提出了最适合作为锂二次电池负极的结构。少

From the aspects of developing the practical lithium secondary battery, the various cathode, anode and electrolyte materials were investigated. As a theme for each subject, we selected (1) the study on the amorphous oxides based on Cr_3O_8 and V_2O_5, (2) developing the salty electrolyte salt substituted for LiClO_4, and (3) the study on the lithium-carbon composite electrode as anode for lithium secondary battery, respectively. The results for these studies during the term of this project were mentioned below.(1) The amorphous Cr_3O_8 prepared from crystal Cr_3O_8 showed the superior characteristics. It has high energy density, high power density and good cyclability. It is discharged homogeneously because of its amorphous structure, of which the potential energy is flattened and the discharge proceeds very smoothly. One of the problems of this compound was the difficulties of making fine of each Cr_3O_8 particle. This results in the worse charge-discharge characteristics at the high … More rate discharging. The brannerite type compound CuV_<2-x>Mo_xO_6 also showed the good cyclability. In addition, there is the interesting feature that the intercalation and deintercalation of lithium and copper occurred in alternate directions at the same time. And the vanadium rich composition compared with the molybdenum rich one has the amorphous structure and shows the good charge-discharge characteristics. (2) In respect of current density and cyclability, the LiPF_6 in PC : DME (1 : 1) electrolyte had the best properties among all electrolytes. (3) It was shown that lithium-carbon composite electrode restrained the formation of lithium dendrites on the lithium substrate. The reaction between lithium and carbon depends on the structure of carbon which means the crystallinity, orientation etc. The higher crystallinity showed the larger amount of lithium accommodation. It is proved that the orientation of carbon crystal has a large effect on the rate of lithium intercalation. From these knowledge, the most suitable structure as the anode of lithium secondary battery was proposed. Less