High‐Entropy‐Based Micro‐Doping Enables High‐Energy‐Density and Stable Layered Sodium Oxide Cathodes

Abstract Transition metal layered oxides are regarded as commercially viable cathode materials for sodium ion batteries (SIBs), but the inadequate rate capability and cyclability significantly impede their practical application. Here, a high‐entropy‐based micro‐doping strategy has been proposed to prepare an O3‐type Na 0.9 (NiFeMn) 0.3 (CuMgAlTiSn) 0.02 O 2 (HE‐NFM) cathode, delivering an ultrahigh energy density of 442 Wh kg⁻¹ at 0.1 C. The HE‐NFM cathode simultaneously achieves high‐rate capability (104.4 mAh g⁻¹ at 2 C) and excellent cyclability (95% capacity after 100 cycles at 1 C), outperforming the undoped ternary counterparts (NFM). DFT calculations confirm reduced Na⁺ migration barriers and lower formation energy through entropy‐mediated stabilization engineering, synergistically enhancing phase stability and Na + migration kinetics. This strategy establishes a paradigm for concurrently optimizing capacity and cyclability in SIBs cathodes.