Improved performance of Li-rich cathode materials by relaxing internal stress and promoting grain growth

Abstract

As one of the highest-capacity commercial cathodes, lithium-rich manganese oxide (LMNO) currently faces challenges related to suboptimal structural stability and capacity retention. We find that this challenge is attributed to internal stress caused by limited grain growth and inherent lattice strain within LMNO. A simple and effective heat treatment strategy, combining Zr doping, is proposed to address these issues. Zr doping increases lattice spacing, alleviating the inherent lattice strain in the two-phase region. Thermal shock promotes atomic diffusion and grain boundary migration, reducing the number of grain boundaries and phase interfaces, thereby alleviating internal stress and facilitating grain growth. Finally, this design with reduced internal stress results in superior structural stability and cycle retention. After 200 cycles at 0.5C current density, the capacity retention of LMNO reaches 93.02%, with significantly suppressed voltage decay. This work underscores the importance of internal stress management in achieving highly stable cathode materials, offering new insights for the design and optimization of cathode materials.