A Biobased Hydrogel Electrolyte for Stable Zinc Anodes via Regulation of the Local Water Environment

Abstract

Aqueous zinc metal batteries are attractive for safe and low-cost energy storage, yet their practical application remains limited by water-induced parasitic reactions and unstable zinc deposition at the anode/electrolyte interface. Herein, a bio-based gelatin/poly(γ-glutamic acid) hydrogel electrolyte is developed to regulate the local water environment and stabilize Zn plating/stripping behavior. The gelatin/PGA composite hydrogel integrates the mechanically supportive gelatin framework with the carboxyl-rich PGA component, providing a polymer environment that regulates water activity and interfacial behavior and is associated with more uniform Zn deposition. As a result, the Zn//Zn symmetric cell achieves stable cycling for over 3600 h at 0.5 mA cm–2 and over 1600 h at 1 mA cm–2. The Zn//I2 full cell exhibits high reversible capacity, low self-discharge, and long-term cycling stability, retaining 90.85% of its capacity after 5000 cycles at 1 A g–1. In addition, the hydrogel electrolyte shows good mechanical durability, cytocompatibility, and degradability under natural conditions. This work provides a sustainable biopolymer-based electrolyte strategy for improving Zn anode stability in aqueous energy storage systems.