Si/C负极在实际应用中的失效原因分析

Analysis of the reason for capacity loss of Si/C anode

将一种Si/C复合负极材料应用于14500圆柱形电池体系中,对它与碳负极电池的基本性能进行了对比,并对该种Si/C负极材料在实际应用中存在的问题以及失效原因进行了分析。以Si/C为负极的电池,其200次循环后容量维持率仅为69.5%。经分析表明,造成其容量衰减的主要原因为:电极体积膨胀导致电极活性材料脱落,电接触性能变差;由材料体积膨胀导致固体电解质相界面(SEI)膜被破坏而造成的电解液不断的分解,使正、负极界面膜增厚,电阻增加;材料本身结构造成插入的Li无法全部脱出。

Si/C anode was used in 14500 cylindrical Li-ion battery. Some basic performance of the battery was studied by comparing the battery with carbon anode which used in the commercial battery widely. The existing problem in usage and the reason of the capacity loss of this material with cycle was studied. The retention of the 14500 battery with Si/C anode only was 69.5% after 200 cycles, the reason of why the capacity deteriorated quickly were： the active material peeled off from the current collector which was caused by the expansion of volume, and the electric contact became poor; SEI was destroyed due to volume expansion of the anode, and the electrolyte decomposed continuously resulting in the incrassation of passivation film and increasement of the resistance; it was not easy to extract all inserted lithium ions from Si.