Asymmetric Polarization Enabled Robust Framework of Prussian Blue Analog Cathode for Ultrastable Sodiation Lifespan Over 50 000 Cycles

ABSTRACT Prussian blue Analogs stand out as a promising category of cathode materials for sodium‐ion batteries owing to their virtues of high theoretical capacity, low cost, and simple synthesis. However, the longstanding framework degradation caused by coordination bond breakage exacerbates the cycling lifetime, which has become a tremendous challenge. Herein, an asymmetric polarization strategy is demonstrated to reinforce the framework of Prussian blue Analogs for ultrastable sodium storage. Low‐electronegative Mg ²⁺ is meticulously implanted to drive electron migration and local accumulation surrounding Fe ²⁺ sites via cyanide bridges. Such asymmetric electron redistribution enables a robust lattice framework by strengthening the Fe─C bonding linkages, thus guaranteeing enhanced electrode reactivity and reversibility. Consequently, the as‐designed magnesium ferrocyanide cathode achieves a remarkable capacity of 91 mAh g ⁻¹ based on single‐electron sodiation and an unprecedented working lifespan exceeding 50 000 cycles. The underlying mechanisms for the boosted cyclability and reaction kinetics are comprehensively elucidated, which will afford a fresh electron‐mediated insight for rational design and development of high‐performance cathode materials for sodium‐ion batteries.