High Entropy Regulation of Electrostatic Repulsion and Structural Design in Layered Oxide Cathodes for Sodium-Ion Batteries.

Abstract

High entropy strategies have emerged as a promising approach for tailoring the structure and electrochemical performance of layered cathodes for sodium-ion batteries (SIBs). Although previous studies have mainly attributed these improvements to entropy-driven structural stabilization, the mechanisms governing phase formation and evolution remain poorly understood. Herein, we propose that electrostatic regulation, particularly the modulation of Na-Na and O-O repulsive interactions, provides an important mechanistic link between high entropy design and structural evolution. Compositional complexity reconstructs the TM-O bonding network, redistributes the charge compensation, alleviates local lattice distortion, and modulates interlayer interactions, thereby influencing the formation and evolution of P2- and O3-type structures during Na+ (de)intercalation. Based primarily on configurational entropy and elemental distribution, high entropy strategies can be divided into three operational categories: high entropy doping, entropy tuning, and high entropy structure. Their phase-dependent effects are then analyzed within P2, O3, and P2/O3 structural frameworks to clarify how entropy-related strategies address distinct electrostatic instabilities. The correlations among sodium content, entropy level, phase structure, and electrochemical behavior are further summarized to establish practical design principles for layered oxide cathodes.