Low-temperature heat treatment enhances the structural stability of O2-type lithium-rich manganese-based materials

Abstract

Lithium-rich manganese-based cathode materials offer both high capacity and low cost. However, the O2 phase obtained by ion-exchange methods is prone to instability in practical applications. Therefore, we systematically investigated the phase-structure evolution and electrochemical properties of O2-type materials subjected to heat treatments in the range of 200–500 °C. The results indicate that low-temperature heat treatment at 200 °C facilitates lattice rearrangement of the O2 phase and helps maintain phase stability. The electrochemical performance is improved accordingly, with a capacity retention of 60.8% after 500 cycles at 1C within the voltage window of 2.0–4.8 V. In contrast, when the heat-treatment temperature exceeds 400 °C, the O2 phase transforms into an O3 phase, leading to a significant deterioration in capacity and rate capability. This study clarifies the influence of heat-treatment temperature on the structure and performance of O2-type lithium-rich manganese-based cathode materials and provides a theoretical basis for their optimization and application.