机械合金化法制备锂离子电池Si基负极材料及其电化学性能研究

Research of Si anode for lithium-ion batteries prepared by mechanical alloying method

Si具有高的储锂容量,但是其循环性能很差。采用机械合金化方法,对纯Si进行处理。同时以石墨、炭黑对纯Si进行掺杂以改善Si的循环特性。对于纯Si,随着球磨时间的延长,材料的非晶化程度增加;经过球磨后材料的平均粒径由原来的29μm变成0.2μm;由大的块状变为小的圆形颗粒。充放电结果表明未经球磨处理的纯Si的首次放电比容量较高,但放电比容量损失较大,循环性能差,而经过球磨的纯Si能增加首次放电比容量,循环性能变化不大;对纯Si采用石墨、炭黑掺杂后材料的首次放电比容量下降,循环性能有所提高;球磨和掺杂没有改变Si储锂的电位。经过阻抗分析发现,球磨后纯Si材料中Li的扩散系数增大。

In this paper, pure Si was as the main study object,mechanical alloying method for the preparation of materials, and in the latter part of the process of materials preparation graphite added and SP doped. For pure Si materials,with increasing of MA time, the degree of amorphous increased; after MA, size of materials particle changed from 29 to 0.2μm; and the shape of the particles changd from large block to small round. In the re- search the charge and discharge results of different MA time materials were discussed. The results showed that Si had a high capacity in first discharge,but had large capacity loss in later cycle and poor cycling performance, after MA, the first discharge capacity of Si had increased. For doped materials, first discharge capacity decreased but cycling performance increased. In dynamic analysis, we found that MA Si had loose structure, which lead to its diffusion coefficient increased.