A Metal-Polymer Framework Electrolyte with Dual-State Zn2+ Ions for Durable Aqueous Zinc Metal Batteries

Aqueous zinc metal batteries (AZMBs) are promising for grid-scale storage due to their safety and low cost, but interfacial instability caused by high water activity and irregular ion flux hinders their progress. Metal-polymer frameworks offer potential through regulated ion channels, yet the distinct roles of zinc ions remain unclear. Herein, we fabricate a Zn2+-coordinated bacterial cellulose electrolyte (BC-Zn) featuring dual-state zinc ions. We demonstrate that stably coordinated Zn2+ forms ordered nanochannels for uniform ion distribution, while weakly adsorbed Zn2+ dynamically participates in Zn metal deposition. This synergy, coupled with confined channel effects, enhances fast ion transport and guides dendrite-free plating. The coordination network also reduces free-water activity, enabling stable operation while granting the membrane excellent mechanical robustness and reusability. Consequently, Zn ∥ Zn cells with BC-Zn achieve stable cycling for >1500 h at 1 mA cm-2 and >300 h at 0.5 mA cm-2 with 29.2 and 9.2 wt % water content. A Zn-I2 full battery delivers 220.07 mAh g-1 with 82.1% capacity retention after 1000 cycles with 29.2 wt % water content and sustains >800 cycles with 9.2 wt % water content at 2C. This work elucidates the critical role of dual-state ions in regulating ion transport and interfacial stability, providing a viable design strategy for durable, high-performance AZMBs.