Stabilizing oxygen by high-valance element doping for high-performance Li-rich layered oxides

Abstract

Lithium-rich layered oxides (LLOs) with high energy density and low cost are regarded as promising candidates for the next-generation cathode materials for lithium-ion batteries (LIBs). However, there are still some drawbacks of LLOs such as oxygen instability and irreversible structure reconstruction, which seriously limit their electrochemical performance and practical applications. Herein, the high-valence Ta doping is proposed to adjust the electronic structures of transition metals, which form strong Ta-O bonds and reduce the covalency of Ni-O bonds, thereby stabilizing the lattice oxygen and enhancing the structural/thermal stabilities of LLOs during electrochemical cycling. As a result, the optimized Ta-doped LLO can deliver a capacity retention of 80% and voltage decay of 0.34 mV cycle−1 after 650 cycles at 1C. This study enriches the fundamental understanding of the electronic structure adjustment of LLOs and contributes to the optimization of LLOs for high-energy LIBs.