Designing rock salt phase enriched surface in Mn-based partially disordered spinel cathode materials for mitigating degradation in Li-ion batteries

Abstract

Mn-based materials show potential as next-generation candidates for lithium-ion battery (LIB) cathode materials owing to their cost-effectiveness, high energy density, and high power density. However, during repetitive charging/discharging processes, these materials undergo cation migration, structural evolution, and phase transition, resulting in sluggish kinetics, substantial voltage decay, and capacity degradation. Herein, we present a Mn-based partially disordered spinel cathode material decorated with a cation-disordered rock salt (DRX) phase-enriched surface to mitigate this voltage and capacity degradation. We demonstrate that a DRX-rich surface layer successfully suppresses the degradation associated with the unfavorable phase transition from the cubic spinel to tetragonal spinel phase. Instead, by harnessing a gradual phase transition from the rock salt to cubic spinel phase concentrated on the surface region, the capacity and voltage increase, delaying the degradation and leading to improved capacity retention. Our findings suggest a strategic approach to exploit Mn-based cathode materials for developing LIBs with superior cyclability and further highlight the potential of controlling the spatial distribution of each phase to enhance the battery performance in multi-phasic cathode materials.