アコースティックエミッション法を用いたリチウムイオン二次電池用アモルファスシリコン負極の初期劣化損傷評価に関する研究^†

Silicon is a promising anode material for lithium-ion battery applications because of its high specific capacity. When silicon is lithiated, it undergoes a volume expansion, which may lead to extensive damage. This is thought to be a primary cause of the rapid decay in the cell capacity. Amorphous silicon (a-Si) has been recently suggested to possess a higher resistance to the lithiation-induced cracking compared with crystalline silicon (c-Si). This paper presents some experimental results of charge-discharge tests conducted on a cell composed of a-Si negative electrode and Li metal. An acoustic emission (AE) technique was employed to carry out in-situ monitoring of the mechanical damage during the tests. A number of AE signals were detected on the first lithiation in the a-Si negative electrode and the AE activity decreased drastically on the subsequent cycles. Examination of frequency components of the AE signals obtained in the tests identified two types of events: one type from silicon cracking, and the other type from the gas generation. The AE results suggested that the mechanical damage due to the lithiation and delithiation took place primarily on the first cycle.