Enhancement of electrochemical performance of LiCoO2 cathode material at high cut-off voltage (4.5 V) by partial surface coating with graphene nanosheets

LiCoO2 cathodes suffer from severe side reactions and rapid capacity fading under high-voltage operation. In this study, partial coating of LiCoO2 by small size graphene nanosheets was achieved to experimentally investigate the graphene modification mechanism in improving the electrochemical performances of LiCoO2 cathode under 4.5V cut-off voltage. Compared with pristine LiCoO2, G-LCO exhibited better cycling stability and rate capability between 2.5 and 4.5 V vs. Li+/Li. Further investigation demonstrated that partial coating with graphene nanosheets could effectively suppress the increase of cell impedance and alleviate the growth of cathode electrolyte interphase(CEI), leading to an outstanding electrochemical performance. This study gives new insights on enhancing cycling stability and rate capability of LiCoO2 under high cut-off voltage.