Superspreading-Photoinitiated In Situ Construction of Hydrogel Electrolyte Enabling High-Performance and Long-Cycling Zinc-Ion Batteries

Abstract

Hydrogel electrolytes have emerged as a research focus for flexible aqueous zinc ion batteries under extreme environment. This prominence arises from the synergistic effect between tunable functional groups within their polymer networks and confined solvent molecules, conferring unique properties including fast ionic conductivity, enhanced mechanical properties, and good flexibility. However, the weak-bonding interface between Zn anode and hydrogel electrolytes poses a challenge to achieve high electrochemical performance batteries. Herein, we prepared a carboxymethyl cellulose/polyacrylamide hydrogel electrolyte with a well-integrated electrode-electrolyte interface via superspreading of a pre-polymerization solution on a superhydrophilic-treated Zn anode surface, combining in situ photoinitiated polymerization. With high Zn2+ transference number (0.83) of the obtained hydrogel electrolyte, the interfacial Zn2+ concentration is largely improved, which effectively suppresses Zn dendrite growth. Consequently, the hydrogel electrolyte enables the Zn//Zn symmetric cell with stable zinc stripping/deposition up to 2400 hours at 0.5 mA cm-2 and 0.5 mAh cm-2. The assembled full cell exhibited significantly enhanced cycling stability, with a capacity retention rate as high as 91% after 2000 cycles even at low temperatures of -20 °C. This strategy realizes a robust interface and offers scalability potential, which provides a viable pathway toward the practical application of sustainable zinc-ion batteries.