A processable and recyclable gelatin/carboxymethyl chitosan hydrogel electrolyte for high performance flexible zinc-ion batteries.

Hydrogels are currently under extensive research as flexible quasi-solid electrolytes for zinc-ion batteries. However, the non-degradability and non-recyclability of hydrogel electrolytes pose significant issues, leading to resource wastage and plastic pollution. Moreover, the increasing needs of hydrogel electrolyte with various shapes to meet individual requirements of next-generation flexible battery raise significant challenges. In this study, we introduce the Hofmeister effect and multiple non-covalent interactions to fabricate an eco-friendly and recyclable multifunctional hydrogel electrolyte using biomass natural polymers. This is achieved by simply soaking primary hydrogel networks of carboxymethyl chitosan (CMCS) and gelatin in zinc sulfate (ZnSO4) aqueous solutions, abbreviated as GCZ-x. The GCZ-x hydrogels exhibit both stiffness and toughness due to the formation of crystalline domains and ionic crosslinks. The dynamic physical interactions and temperature and pH responsiveness of the GCZ-x hydrogels enable them excellent processability and recyclability. The zinc-ion battery with GCZ-x hydrogel as electrolyte exhibits high specific capacity and superior cyclic performance (2200 h at 0.1 A g) without the formation of zinc dendrites. The GCZ-x electrolyte is sustainable with high recycling rate (above 80 %). It is envisaged that the GCZ-x hydrogel electrolyte will initiate new prosperity of green zinc-ion batteries in energy-efficient and environmentally sustainable ways.