Unraveling the Proton Co-Insertion Chemistry through Electrolyte Hydrogen-Bond Intervention for Zinc-Manganese Dioxide Batteries

Aqueous Zn-MnO 2 batteries are promising for large-format energy deployment due to their inherent safety and environmental compatibility. Nevertheless, their commercial implementation is critically bottlenecked by the elusive proton co-insertion mechanism at the cathode, in contrast to the relatively well-understood anode stability. Herein, we unveil the underlying H + -storage phenomenon within MnO 2 via a tailored hydrogen-bond intervention strategy. Our findings reveal that the catastrophic capacity degradation originates squarely from the second discharge plateau, which is intrinsically governed by the hydrogen-bond network. By reinforcing the hydrogen-bond environment, we effectively modulate proton intercalation kinetics and suppress the excessive H + flux that otherwise triggers structural collapse. While traditional aqueous electrolytes lead to severe manganese dissolution and irreversible vacancy formation, our strategy preserves the structural integrity of the MnO 2 ’s 2 × 2 tunnel framework. Theoretical calculations confirm that the incorporation of H + into α-H x MnO 2 weakens the Mn─O bonds with notable vacancy formation. Leveraging these mechanistic insights, we demonstrate Zn-MnO 2 pouch cells under stringent practical conditions—high areal capacity (2.62 mAh cm −2 ), restricted N/P ratio (2.2), and lean electrolyte (30 µL mAh −1 )—yielding a specific energy of 167 Wh kg −1 . Meanwhile, this electrolyte demonstrates an excellent one-year cycling lifespan at −10°C. This work provides insight for high-performance aqueous batteries.