Decoupling Roles of Cationic Dimensionality and Valence‐Electron Compatibility on Structural Resilience and Kinetics in High‐Entropy Prussian Blue Cathodes for Sodium‐Ion Storage

High-entropy Prussian blue analogues (PBAs) have considered as high-performance cathodes for sodium-ion batteries (SIBs). However, the impact of high-entropy component compatibility on electrodes' lattice stress and kinetics remains underexplored. Herein, a series of high-entropy PBAs are served as cathode materials for SIBs. The tailoring Na₂Mn_0.2Fe_0.2Co_0.2Ni_0.2Cu_0.2[Fe(CN)₆] (HE-Cu) with superior mechanochemical compatibility shows superior phase stability without obvious lattice stress and faster electron/ion transfer kinetics. Intrinsic and accumulated lattice stresses can be obtained by ion-incompatible Sn-based high-entropy PBA (HE-Sn) and valence-electron mismatched Ti-based high-entropy PBA (HE-Ti), thereby exhibiting poor structure stability and dynamics. Serious Jahn-Teller structural distortion and unstable octahedron, observed in Na₂Mn[Fe(CN)₆] with complicated Na-ion storage phase evolution (monoclinic ↔ cubic ↔ tetragonal), can be entirely suppressed by high-entropy effect, appearing a zero-strain solid-solution reaction mechanism for HE-Cu employing Mn, Fe, and Co-ions as redox centers to involve in charge compensation. Consequently, HE-Cu presents high initial specific capacity of 120.4 mAh·g^-1, superior rate capability and outstanding cyclability with ultra-long cycling life of 9000 cycles with the lowest capacity-decay-rate of 0.0042% per cycle. Na-ion full cell demonstrates high initial energy density of 397.0 Wh·kg^-1 and perfect cycling stability with long lifespan over 2000 cycles.