Self-adhesive polyzwitterionic hydrogel electrolytes for long-life flexible zinc-ion batteries

Abstract

Hydrogel electrolytes have a wide range of promising applications in flexible zinc-ion batteries (ZIBs) due to their high ionic conductivity and soft wetting properties. However, poor electrode/electrolyte interfacial compatibility leads to sluggish ion transport and interfacial side reactions that reduce the cycle life of the cell. Herein, a zwitterionic sulfobetaine/acrylamide hydrogel electrolyte with self-adhesive and stable electrochemical properties was investigated to address the above problems. This hydrogel electrolyte possesses excellent tensile properties (620%), self-adhesive properties, ionic conductivity (59.0 mS cm⁻¹) and Zn²⁺ transference number (0.81). Meanwhile, the special zwitterionic structure can construct separated anion and cation migration channels to promote ion transport and uniform deposition of Zn²⁺. The ZIBs assembled with the zwitterionic hydrogel electrolyte exhibit excellent electrochemical performance with a high specific discharge capacity of 292 mA h g⁻¹ at 5 A g⁻¹ and a capacity retention of 94.7% after 1000 cycles. In addition, flexible pouch ZIBs based on zwitterionic hydrogel electrolytes were designed, which can work properly when subjected to different types of damage and offer great potential in the field of flexible wearable energy storage.