Binder-free electrodeposited Co-MnO₂ cathode with enhanced defect chemistry for high-performance aqueous zinc-ion batteries

Owing to its natural abundance, environmental compatibility, and high theoretical capacity, manganese dioxide (MnO₂) has generated significant interest as a potential cathode material for aqueous zinc-ion batteries (ZIBs). However, its real-world usage is limited by inadequate electrical conductivity, slow Zn2+ ion transport, and structural instability during repeated charge and discharge cycles. In this study, we present a one-step electrodeposition strategy for synthesizing cobalt-doped MnO₂ (Co-MnO₂) nanowires directly on graphite substrates, yielding cathodes with significantly enhanced electrochemical performance. Structural analysis of Co-MnO₂ confirmed that the MnO₂ framework was preserved, with an increased presence of oxygen vacancy-related species that modulate the Mn oxidation states, suggesting that defects were introduced due to cobalt incorporation. EIS indicates a notable decrease in charge-transfer resistance relative to the pristine MnO₂. The Co-MnO₂ electrode delivers a high discharge capacity of 372.6 mAh g−1 at 0.5 Ag-1, and excellent durability over 600 cycles (∼84% capacity retention at 1Ag-1), outperforming pristine MnO₂. The synergistic effects of cobalt-induced oxygen vacancies and nanowire architecture collectively enhance electronic conductivity, Zn2+ transport, and redox kinetics, resulting in improved rate capability and cycling stability. Overall, this study establishes cobalt doping via electrodeposition as an effective strategy to advance MnO₂-based cathodes for high-performance aqueous zinc ion batteries.