Phosphorylation of Li-Rich Mn-Based Layered Oxides for Anion Redox and Structural Stability.

Abstract

Li-rich Mn-based layered oxides are proposed to be candidates for high-energy Li-ion batteries. However, their large-scale production is still hampered by poor rate capability and severe voltage decay. It was mainly attributed to the irreversible oxygen loss, which induces transition metal ion migration, electrolyte consumption, and structural evolution. Herein, we propose an effective strategy of phosphorylation, in which the phosphate ion is induced to remove the surface labile oxygen. It urges the Li2MnO3 component to transform to the spinel-like structure and promotes the anionic redox process, thus facilitating lithium-ion diffusion and improving structural stability. As a result, the Li2MnO3 component is more prone to be activated, with the capacity increased by 18% in comparison with the pristine one. It also exhibits a superior capacity retention of 86.1% after 150 extended cycles and better rate performance delivering a capacity of 148.1 mA h g-1 even at 10 C. The effective phosphorylation opens a new way to tune anion redox chemistry and obtain structurally stable materials.