Exploring the graphene effect of graphene ball coating on Ni-rich layered oxide materials for high-performance Li-ion batteries

The research is conducted on the specific surface area changes and coating amount optimization of graphene in graphene ball (GB) using LiNi0.88Co0.08Mn0.04O2 (NCM88). Two different specific surfaces areas (100 and 300 m2 g−1) are used. The low surface area GB coated NCM88 shows better cycling performance than the high surface area NCM88 in tests at 25 and 60 °C. Due to the large specific surface area of GB, the side reactions that may be caused by excessive impregnation of the electrolyte occurred a little better. The more the coating amount, the less the transition metal ratio and the more the amount of residual lithium on the surface of cathode, so the capacity becomes lower. However, the cycle performance improved by preventing the side reaction between cathode and electrolyte. Considering the electrochemical performance of GB coated samples, the optimum coating weight is 1 wt% GB coated NCM88 with a specific surface area of 100 m2 g−1.