Role of Hydroxyl Groups in Dehydrated Manganese Potassium Hexacyanoferrate for Enhanced Zinc‐Ion Storage

Prussian blue analogs (PBAs) are recognized as superior cathode materials for aqueous zinc‐ion batteries, commonly suffering from low capacity and poor cycle stability. While hydrogen thermal treatment is recognized as an effective approach to enhance performance of PBAs, the complex effects of thermally induced hydroxyl groups remain elusive. Therefore, this study modulates the content of hydroxyl groups via a series of thermal treatments to explore their effects on the electrochemical properties of PBAs. The results indicate that surface hydroxyl groups induce dual‐direction effects on the electrochemical reaction kinetics and cycling stability of dehydrated PBAs. Specifically, the optimal hydroxyl content exists due to the competition between the beneficial electrochemical activation for additional capacity and the adverse effect of accelerated Jahn–Teller distortion and Mn dissolution, leading to structural collapse and incapability of capacity recovery. The optimized sample delivers exceptional electrochemical performance, achieving the higher specific capacities of 79.2 mAh g −1 at 0.5 A g −1 and 50.7 mAh g −1 at 2.0 A g −1 . It also exhibits outstanding long‐term stability, retaining 94.3% capacity after 400 cycles at 1.0 A g −1 . This study provides new avenues for developing aqueous zinc‐ion batteries cathode materials with both high specific capacity and excellent cycling stability.