Aqueous zinc batteries (AZBs) are considered one of the most promising candidates for grid-scale energy storage. However, achieving a stable electrode-electrolyte interface remains a challenge for developing high-performance AZBs. Herein, taking the Zn||phenazine (PNZ) system as a prototype, where the proton uptake/removal mechanism dominates in the cathode, a carboxylic acid-functionalized cellulose hydrogel electrolyte is designed to simultaneously solve the issues at both the anode and cathode interfaces. Specifically, the hydrogel electrolyte can not only regulate Zn