It is expected that waste LIB(lithium ion batteries) more than 1 million pieces will spill out of xEV from 2020, and various researches for recycling are under progress in world wide. Currently, recovery of valuable metal and high purification is conducting by disassembling and chemical decomposition of batteries. Recently there is motion to reuse waste LIB to ESS(Energy Storage System) considering economical value of CO2 reduction effects. To do this, a series of gathering, disassembling, analyzing, re-treatment, grading and reprocessing process of waste LIB have to be managed synthetically. Among them, chemical analysis of waste LIB using inert atmospheric condition is important to clarify degradation mechanism of lithium ion batteries. In this study, we fabricated the full cell with structure of LCO/EC:DEC in 1M LiPF6/graphite, and the surface characterization of SEI layer formed on LCO and graphite surface after charge/discharge test was analyzed under inert atmospheric conditions using XPS and AES techniques.The degradation mechanisms by change of SEI layer with cycling and surface characterization of different active materials will be discussed.