Sulfonated Hydrogel Electrolyte Enables Dendrite-Free Zinc-Ion Batteries

Metallic Zn anode is plagued by severe side reactions and dendrite growth, preventing the commercial development of Zn-ion batteries (ZIBs). Semi-solid state hydrogel electrolyte have received immense attention in aqueous Zn-ion batteries due to their intrinsic advantages (e.g., wider electrochemical windows, good interfacial compatibility and multi-functional applications). However, their inferior ionic conductivity and mechanical deformation tolerance are the main barriers to realizing the true application in ZIBs. Herein, a hydrogel electrolyte with high ionic conductivity and high flexibility is fabricated through sulfonating chitosan and further crosslinking with polyacrylamide. Accordingly, the ion conductivity of hydrogel electrolyte increases from 28.2 mS cm-1 to 38.1 mS cm-1, whilst tensile strength is elevated from 19.1 kPa to 54.2 kPa. With this hydrogel electrolyte, the Zn||Zn symmetric cells show exceptional cycle stability over 2600 h at the current density of 1 mA cm-2, and the Zn||Cu asymmetric cells demonstrate nearly 100% coulombic efficiency over 1200 cycles. In addition, NH4V4O10||Zn full cells enable to remain a capacity retention of as high as 96.1% even over 500 cycles, and the as-assembled flexible batteries can stand bending, twisting and cutting operation without comprising the electrochemical performance.