Design of gelatin/zwitterionic hydrogel electrolytes based on chain–chain synergy for wide-voltage flexible zinc-ion hybrid capacitors

To enhance the energy density of aqueous zinc-ion hybrid capacitors (ZIHCs), broadening the electrochemical window of hydrogel electrolytes is crucial. However, persistent side reactions initiated by water molecules and the uncontrolled dendritic growth on the zinc anode surface severely limit the improvement of ZIHC operating voltage. To address this challenge, this study proposes a chain–chain synergistic regulation strategy and designs a unique semi-interpenetrating network zwitterionic hydrogel electrolyte (PGCTSE) based on PSBMA and gelatin. This electrolyte effectively regulates Zn 2+ migration behavior and suppresses free water activity, thereby significantly increasing the operating voltage of flexible ZIHCs. Experimental results show that the PGCTSE electrolyte expands the electrochemical stability window (ESW) of flexible ZIHCs to 2.2 V, achieves a Zn 2+ transference number as high as 0.76, and supports highly reversible deposition/stripping on the zinc anode. The flexible ZIHC employing this electrolyte delivers an energy density of 180.8 Wh kg −1 at a power density of 1100 W kg −1 . This study provides a new design concept and experimental foundation for developing gelatin-based hydrogel electrolytes for high-performance ZIHCs.