A Study on SEI and Electrolyte Decomposition Products of SiOx/C Anode using Electrolyte Additives

초록

The continuous decomposition of the electrolytes and the formation of the SEI layer, resulting from the surface exposure of active materials caused by the rapid volume change of the electrode during the charging and discharging process, causes the consumption of the electrolytes, rapidly deteriorating the performance and stability of the lithium?ion batteries (LIBs). By adding the additives with a low LUMO level to the electrolytes, the additives are decomposed before the electrolytes to form a stable solid electrolyte interface (SEI) layer against volume changes and side reactions, thereby preventing continuous consumption of the electrolytes and pulverization of active materials.[1] However, although the electrolytes with additives that can decompose on the electrode surface contribute to the formation of the SEI layer, which has a significant impact on battery performances, there is insufficient studies on decomposition products, particularly in case of silicon anodes, which is attracting attention as a next-generation electrode material. In this study, the electrolyte of 1 M LiPF6 in EC:EMC (1:1, v/v) containing 2 vol.% of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) was applied in a half?cell configuration using CR2032 type coin?cells assembled in the Ar?filled glove box that maintains the oxygen content below 0.1 ppm using graphite or SiOx/C as anode electrode. The SEI layer was analyzed through a scanning electron microscope (SEM) and an X-ray photoelectron spectrometer (XPS). Furthermore, gas chromatography equipped with a mass selective detector (GC?MS) were performed to investigate the decomposition products prepared during cycling.