High‐Performance MnOOH/ α ‐MnO ₂ Composite Cathode With Enhanced Capacity and Cycling Stability for Aqueous Zinc‐Ion Batteries

Manganese‐based cathode materials hold great promise for aqueous zinc‐ion batteries (AZIBs) due to their high operating voltage and low cost. Among these, manganese dioxide (MnO 2 ) cathodes exhibit particularly promising electrochemical characteristics but face critical challenges including insufficient electrical conductivity and rapid capacity fading. To address these issues, manganese oxyhydroxide (MnOOH) and α ‐MnO 2 have been studied. MnOOH offers excellent cycling stability but suffers from a relatively low specific capacity, whereas α ‐MnO 2 delivers high specific capacity but exhibits poor cycling stability. A rationally designed MnOOH/ α ‐MnO 2 composite was synthesized via a crystal phase transformation method, using δ ‐MnO 2 as the precursor. The composite features a unique nanowire and nanorod morphology and is employed as a cathode material for AZIBs. It outperforms its individual components, achieving a high specific capacity of 233.4 mAh g − 1 after 750 cycles at 1 A g −1 . At an elevated current density of 2 A g −1 , it maintains a stable specific capacity of 85.0 mAh g −1 after 17,000 cycles. Comprehensive mechanistic investigations reveal that the zinc storage process involves the co‐intercalation/extraction of Zn 2+ and H + ions, coupled with reversible MnO 2 dissolution and redeposition. These findings highlight the potential of MnOOH/ α ‐MnO 2 composites as high‐performance cathode materials for AZIBs, effectively addressing the challenges of capacity limitation and cycling stability.