Carboxylic Acid‐Functionalized Cellulose Hydrogel Electrolyte for Dual‐Interface Stabilization in Aqueous Zinc‐Organic Batteries

Abstract 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 2+ ions at the Zn anode side but also supply H + ions at the PNZ cathode side to avoid the unfavored deposition of zinc sulfate hydroxides. Benefiting from the unique one‐gel‐for‐two‐electrodes strategy, the dendrite‐free and side reaction‐suppressed aqueous Zn||PNZ cells are developed with a high specific capacity (311 mAh g −1 , 99% utilization of the theoretical capacity) and a long cycle life (over 1500 cycles within 2 months). This study proposes a facile and low‐cost electrolyte strategy for stabilizing AZBs.