Strain and Kinetics Synergy in Octahedral High‐Entropy Cathodes Enables Ultra‐Durable Sodium‐Ion Batteries

High‐entropy oxides represent a paradigm shift in sodium‐ion battery cathodes by utilizing entropy‐driven structural stabilization to address the intrinsic challenges of lattice strain and sluggish ion kinetics. However, conventional high‐entropy oxides face challenges in synthesis complexity and insufficient mechanistic insights into strain‐kinetics coupling. Here, a high‐entropy O3‐type layered oxide, Na 0.9 Ni 0.2 Co 0.2 Fe 0.2 Mn 0.2 Zn 0.05 Cu 0.05 Ti 0.1 O 2 (NNCFMZCT), is proposed featuring seven transition metals in a single crystallographic site, to synergistically optimize Na⁺ diffusion and structural resilience. Density functional theory calculations reveal that configurational disorder mitigates anisotropic lattice contraction during O/P phase transitions, while X‐ray photoelectron spectroscopy and in situ X‐ray diffraction confirm stable TMO₆ octahedra and suppressed irreversible phase transitions. The NNCFMZCT cathode delivers a high reversible capacity (>130 mAh g −1 at 10 mA g −1 ), exceptional cycling stability (82.9% retention over 300 cycles at 500 mA g −1 ), and superior rate capability (>110 mAh g −1 at 1000 mA g −1 ) within 2.0–4.0 V. When paired with commercial hard carbon in ampere‐hour‐level cylindrical cells, the full cell achieves 84% capacity retention after 200 cycles. This work demonstrates scalable viability for grid storage by establishing a universal strain‐kinetics coupling strategy, which advances the rational design of entropy‐stabilized cathodes for sustainable energy systems.