Zn/MnO₂ Battery Chemistry With H⁺ and Zn²⁺ Coinsertion

Rechargeable aqueous Zn/MnO₂ battery chemistry in a neutral or mildly acidic electrolyte has attracted extensive attention recently because all the components (anode, cathode, and electrolyte) in a Zn/MnO₂ battery are safe, abundant, and sustainable. However, the reaction mechanism of the MnO₂ cathode remains a topic of discussion. Herein, we design a highly reversible aqueous Zn/MnO₂ battery where the binder-free MnO₂ cathode was fabricated by in situ electrodeposition of MnO₂ on carbon fiber paper in mild acidic ZnSO₄+MnSO₄ electrolyte. Electrochemical and structural analysis identify that the MnO₂ cathode experience a consequent H⁺ and Zn²⁺ insertion/extraction process with high reversibility and cycling stability. To our best knowledge, it is the first report on rechargeable aqueous batteries with a consequent ion-insertion reaction mechanism.