Entropy Strategy for Stabilizing O′3-NaMnO<sub>2</sub>‑Layered Cathodes for Sodium-Ion Batteries

Layered transition-metal oxides are\nrecognized for their substantial\npotential as cathode materials for sodium-ion batteries (SIBs), particularly\nin the context of large-scale energy storage systems. O′3-NaMnO<sub>2</sub> (NMO) has received considerable attention due to its cost-effectiveness,\nhigh capacity, and adequate initial sodium content. However, its practical\napplication is hindered by issues, such as Jahn–Teller distortion\nand the migration of Mn during cycling, which result in severe irreversible\nphase transitions and structural collapse. In this study, the entropy\nstrategy was employed to synthesize O′3-NaMn<sub>0.8</sub>Mg<sub>0.06</sub>Ti<sub>0.06</sub>Fe<sub>0.04</sub>Al<sub>0.04</sub>O<sub>2</sub> (NMO-MTFA), which not only stabilized the crystal structure\nbut also enhanced both the bulk and surface/interface kinetics. NMO-MTFA\ndelivers a high initial discharge capacity of 190 mA h g<sup>–1</sup> and demonstrates a superior cycling performance and rate capability.\nThe stabilization of the crystal structure is further reinforced by\nthe strengthened Mn–O interaction, achieved through the trace\ndoping of multiple elements. This research underscores the efficacy\nof the entropy strategy in optimizing the performance of layered oxide\ncathodes, thereby presenting a novel approach for the design of high-performance\nSIBs.