High-Entropy-Inspired Trace Multi-cation Doping Enables Structural Reinforcement and Accelerated Na-Ion Transport in Mn-Based Layered Cathodes

Owing to their open Na+ diffusion pathways and high theoretical specific capacity, P2-type layered oxides are regarded as promising cathode materials for sodium-ion batteries (SIBs). In this study, we propose a high-entropy trace doping strategy and employ a high-temperature solid-state method to incorporate five metal elements (Mg, Al, Co, Zn, and Ti) into P2-Na0.67MnO2, successfully synthesizing the P2-Na0.67Mg0.02Al0.02Co0.02Zn0.02Ti0.02Mn0.9O2 (HE-NMO) cathode material. Structural characterizations reveal that high-entropy trace doping effectively regulates anisotropic grain growth, while the relatively homogeneous distribution of multi-element ions within the particles modifies the local ordering environment and regulates the TM–O bonding framework. Electrochemical measurements demonstrate that HE-NMO exhibits enhanced Na+ diffusion kinetics and a higher pseudocapacitance contribution compared with undoped NMO. Benefiting from the complementary effects of structural stabilization and accelerated ion transport, HE-NMO delivers a high discharge capacity of 169.6 mAh g–1 at 50 mA g–1 and maintains 80.1 mAh g–1 at 2 A g–1, together with 78.7% capacity retention after 300 cycles at 500 mA g–1. This work provides a high-entropy-inspired trace multi-cation doping strategy for designing structurally robust and kinetically favorable P2-type layered oxide cathodes toward advanced sodium-ion storage.