Entropy Strategy for Stabilizing O′3-NaMnO₂-Layered Cathodes for Sodium-Ion Batteries

Layered transition-metal oxides are recognized for their substantial potential as cathode materials for sodium-ion batteries (SIBs), particularly in the context of large-scale energy storage systems. O′3-NaMnO2 (NMO) has received considerable attention due to its cost-effectiveness, high capacity, and adequate initial sodium content. However, its practical application is hindered by issues, such as Jahn–Teller distortion and the migration of Mn during cycling, which result in severe irreversible phase transitions and structural collapse. In this study, the entropy strategy was employed to synthesize O′3-NaMn0.8Mg0.06Ti0.06Fe0.04Al0.04O2 (NMO-MTFA), which not only stabilized the crystal structure but also enhanced both the bulk and surface/interface kinetics. NMO-MTFA delivers a high initial discharge capacity of 190 mA h g–1 and demonstrates a superior cycling performance and rate capability. The stabilization of the crystal structure is further reinforced by the strengthened Mn–O interaction, achieved through the trace doping of multiple elements. This research underscores the efficacy of the entropy strategy in optimizing the performance of layered oxide cathodes, thereby presenting a novel approach for the design of high-performance SIBs.