Synthesis and characterization of polyzwitterionic hydrogel electrolytes for enhancing the interface stability of a Zn-metal anode

Zinc-ion batteries (ZIBs) based on hydrogel electrolytes have broad application prospects in wearable sensors, implantable devices, and soft robotics. However, designing a hydrogel electrolyte with high ionic conductivity and outstanding interface stability remains challenging. Especially, the dendrite and side reactions caused by unstable interfaces limit the application of ZIBs. Herein, the polyzwitterionic hydrogel electrolyte (P(AM-co-AMPS-co-DMC)) with dual-ion migration channels was developed based on the synergistic effect between the polyzwitterionic network and high-concentration saline. The resultant hydrogel electrolyte exhibited excellent ionic conductivity (46.19 mS cm-1), surpassing most reported single-ion hydrogels. The Zn–Zn symmetric cell with hydrogel electrolyte could maintain a long cycling lifespan of 2000 h at a current density of 1 mA cm-2 with a capacity of 1 mA h cm-2. Additionally, the Zn-Cu cell using the hydrogel electrolyte also exhibited more stable Coulomb efficiency with a high average value of 99.1%. This work provides a novel design philosophy for flexible electrolytes with exceptional long-term stability, which will facilitate the adoption of flexible ZIBs in emerging flexible electronics.