Insight into the High-Temperature Cycling Stability of a Micro-nanostructured LiNi0.5Mn1.5O4/Graphene Composite Cathode for High-Voltage Lithium-Ion Batteries

LiNi0.5Mn1.5O4 (LNMO) cathode has drawn enormous interest for its extraordinarily high voltage and low cost. However, a high voltage leads to critical side reactions significantly degrading the cycling stability and safety, which will be accelerated by a high temperature. Graphene coating has been demonstrated to be a valid method to tackle these problems mentioned above. However, the enhancements mechanism on cycling stability remains unclear. Thus, we meticulously constructed hybrid sphere-nanorod-like micro-nanostructured LNMO/graphene composites and deeply explored the improvement mechanism on the cycle performance of LNMO. The results confirm that graphene coating contributes to protect the active substance from corrosion by electrolyte decomposition and helps stabilize the LNMO structure against structural deformation. Owing to graphene coating, LNMO/graphene composites present a better electrochemical performance. After circulation for 100 cycles at 55 degrees C, LNMO/graphene composite (1000:5 wt) maintained 99.4% of its initial discharge capacity under 2 C. Furthermore, such excellent electrochemical performance is also reflected in assembly LNMO/graphene/Li4Ti5O12 (LTO) full cells. This work reveals the origins and enhancement mechanisms for LNMO/graphene composites, which can be extended to other graphene composites to promote the application of graphene.