Lithium ion batteries have been mainly hiring for electric vehicle from middle of 2000’s. In order to fulfill a driving distance of xEV cars, a demand for cathode material which has high specific capacity has been arisen. The most attractive cathode material is High-Ni layered oxide such as NCA and NCM. These materials have highest specific capacity of all the material which can be commercialized. In this thesis, by using LiNi0.88Co0.11Al0.01O2 which is recently developed cathode material, the effect of water washing on battery life was investigated. This study was regarded under two aspects. One is cycle life and the other one is calendar life. In case of cycle life, the structural change is happened during charging and discharging. Therefore, to monitor the washing effect in structural change, Synchrotron based X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) method were used. After 1C/1C 300cycles before washing sample retains 76% capacity compare to the first cycles while washed sample sustains 83% capacity. At the beginning of charge stage a different peak shifting was observed in In-situ XRD. In case of high temperature storage, to confirm an inner gas generation by reaction on the surface, Gas chromatography and Mass spectroscopy (GC-MS) has been carried out. After 100day at 60℃ with state of charge (SOC) 100%, before washing sample shows 78% of capacity retention, whereas after washing sample has 81% capacity compare to before storage. Before 60℃ storage, before washing sample and after washing sample showed similar amount of gas evolution with the same type of gas CO2, CO, H2, CH4, C2H6, O2, C2H4. The CO gas occupies 75.8% of gas evolution in both samples. After storage, before washing sample’s gases are increased from 1.167mL/g to 1.467mL/g(26% increased) whereas after washing sample shows change in gas from 1.154mL/g to 1.341mL/g(16% increased).