Identifying Active Sites for Parasitic Reactions at the Cathode–Electrolyte Interface

Nickel-rich transition metal oxides are the most promising high-voltage and high-capacity cathode materials for high-energy-density lithium batteries. Improving the chemical/electrochemical stability of the cathode-electrolyte interface has been the major technical focus to enable this class of cathode materials. In this work, LiCoO 2 is adopted as the model cathode material to investigate the active sites for parasitic reactions between the delithiated cathode and the nonaqueous electrolyte. Both ab initio calculations and experimental results clearly show that the partially coordinated transition metal atoms at the surface are responsible for the parasitic reactions at the cathode-electrolyte interface. This finding lays out fundamental support for rational interfacial engineering to further improve the life and safety characteristics of nickel-rich cathode materials.