Insight into the effect of graphene coating on cycling stability of LiNi0.5Mn1.5O4: Integration of structure-stability and surface-stability

Graphene has presented promising features for application in lithium ion batteries(LIBs) due to its superior electronic conductivity and high surface area. It has been successfully used for modifying cathode materials to meet the increasing demand for LIBs with longer cycle life. However, the improving effect of graphene on cycling stability is still unclear, which restricts its further application in LIBs. Herein, graphene coated hollow sphere-like structure LiNi0.5Mn1.5O4(LNMO) wasdesigned and the improvement mechanism of graphene coating on LNMO's cycling stability was investigated. The results show that graphene coating not only contributes to suppress structural deformation from mechanistic reaction and extend solid-solution reaction, but also helps protect electrode from corrosion by the products from electrolyte decomposition and suppress the generation of surface defects, especially at high temperature. Owing to graphene coating, graphene coated LNMO can deliver a discharge capacity of 91 mAh g−1 with high capacity retention of 82.5% after 1000 cycles under 20C and 83.8 mAh g−1 with 94.5% capacity retention after 100 cycles under 2C at 55 °C. This work deeply explores the effect of graphene coating on cycling stability from crystal stability and surface stability, which will help a wider application of graphene in energy storage field.