Revealing the Electrochemical Mechanism of Cationic/Anionic Redox on Li-Rich Layered Oxides via Controlling the Distribution of Primary Particle Size.

Lithium-manganese-rich layered oxides have sparked intense interest on high-energy-density lithium-ion batteries because of their unique anionic redox. While making efforts to adjust the primary particle size for the improved electrochemical kinetics, current research is insufficient to explain how the anionic/cationic interplay governs the electrochemical behavior except for ion diffusion. Here, fully ordered LiMnNiCoO spheres of shortened primary particle size were synthesized via the coprecipitation method for use as cathodes. A high discharge capacity of 303.2 mA h g was achieved for the first cycle. Optimized nanostructures reduce the lithium ion diffusion length and increase electronic conductivity unsurprisingly, contributing to excellent electrochemical activity and rate capability. Furthermore, the decreased primary particle size accelerated the redox reactivity of cations and the reversibility of anionic redox on path dependence. This work clarifies the electrochemical mechanism of cationic/anionic redox of these Li-rich layered oxides and provides a new vision for a unique design of high-energy cathode materials with better application.