Role of carbon coating in improving electrochemical performance of Li-rich Li(Li₀.₂Mn₀.₅₄Ni₀.₁₃Co₀.₁₃)O₂ cathode

Li-rich Li(Li₀.₂Mn₀.₅₄Ni₀.₁₃Co₀.₁₃)O₂ cathode coated with carbon layer has been prepared by a hydrothermal approach followed by a post annealing process. The cathode after surface modification exhibits both enhanced cyclability and improved rate capability compared with the pristine one without coating. The carbon coating process causes a phase transformation from Li₂MnO₃-like domain to cubic-spinel domain with Fd3m symmetry at surface regions of particles. As a consequence, the valence state of Mn on the surface accordingly varies. Such transformed surface spinels, as well as the wrapped carbon layers as a result of this coating strategy are believed to be responsible for the enhanced electrochemical performance.