Inhomogeneous Coordination in High‐Entropy O3‐Type Cathodes Enables Suppressed Slab Gliding and Durable Sodium Storage

Abstract O3‐type layered oxides are highly promising cathodes for sodium‐ion batteries (SIBs), however they undergo complex phase transitions and exhibit high sensibility to air, leading to subpar cycling performance and commercial viability. In this work, we report a layered cathode material (NaNi 0.29 Cu 0.1 Mg 0.05 Li 0.05 Mn 0.2 Ti 0.2 Sn 0.11 O 2 ) with a sate‐of‐the‐art high‐entropy compositional design. We unveil that such a configuration featuring inhomogeneous coordination environment of transition metal (TM) elements, can enable enhanced gliding energy (−0.38 vs −0.58 eV) of TMO 2 slabs upon desodiation both theoretically and experimentally, which underlies the fundamental origin of the outstanding structural stability of HEO materials. As a consequence, the complex phase transitions (O3−O′3−P3−P′3−P3′−O3′) of conventional O3‐type cathode have been eliminated, and the as‐obtained material demonstrates exceptional structural robustness and integrity with an ultra‐long cycle life in a quasi‐solid‐state cell (maintaining 73.2 % capacity after 1000 cycles at 2 C). Moreover, the material presents satisfactory air stability, with minimal structural and electrochemical degradation when directly exposed to the air. An Ah‐scale pouch cell based on the cathode material is constructed, demonstrating a capacity retention of 83.6 % after 500 cycles, signaling substantial promise for commercial applications.