Anion‐Exchange‐Enabled Hydrogel Electrolytes With High Zn ² ⁺ Transference for Dendrite‐Free Flexible Zinc‐Ion Batteries

Hydrogel electrolytes for flexible aqueous zinc‐ion batteries (ZIBs) are limited by unregulated anion mobility, which triggers concentration polarization, dendrite growth, and parasitic reactions. Herein, a high‐Zn 2+ ‐transference hydrogel electrolyte (ex‐PDADAM) is developed by exchanging Cl − with ClO 4 − at quaternary ammonium sites within a poly(diallyldimethylammonium)‐polyacrylamide co‐network. This single anion‐exchange step fulfills three functions simultaneously: (i) electrostatic immobilization of anions suppresses anion migration and promotes high Zn 2+ transference, increasing the transference number to 0.86; (ii) multivalent ionic crosslinks between ammonium cations and perchlorate anions reinforce the network toughness to 51.25 MJ m −3 ; and (iii) restructuring of the hydrogen‐bonding network of water within the hydrogel matrix suppresses parasitic reactions and widens the electrochemical stability window to 2.75 V. The ex‐PDADAM hydrogel delivers an ionic conductivity of 8.10 mS cm −1 at 25°C, enabling Zn||Zn symmetric cells to cycle stably for over 2000 h at 1 mA cm −2 (35 mV overpotential). Flexible 4 × 3 cm 2 pouch cells paired with vanadium oxide cathodes deliver ∼270 mAh g −1 under 0°–360° bending and retain 90.9% capacity after 300 cycles. This work establishes anion‐exchange chemistry as a versatile strategy for high‐Zn 2+ ‐transference hydrogel electrolytes toward mechanically robust flexible ZIBs.