A natural solvent-based gel electrolyte for stable and sustainable zinc-ion batteries

Natural solvent-based electrolytes are increasingly sought for zinc-ion batteries (ZIBs) as they provide a sustainable and cost-effective means to regulate water activity and electrode–electrolyte interfacial chemistry while retaining the intrinsic safety of aqueous systems. Herein, a sustainable electrolyte formulation utilizing a chia seed (CS)-based hydrogel is reported as an effective approach to improve the electrochemical stability of ZIBs. Owing to its high content of hydroxyl-rich polysaccharides and phenolic compounds, the chia seed-derived gel electrolyte (CSGE) tailors the Zn2+ solvation environment, decreases free-water activity, and restrains parasitic hydrogen evolution as well as dendritic zinc growth. Benefiting from this regulated solvation environment, the CSGE achieved a remarkably high Zn2+ transference number of 0.84. Consequently, Zn//Zn symmetric cells demonstrated outstanding electrochemical stability exceeding 4000 h at 1.0 mA cm−2 and 1.0 mAh cm−2. Moreover, Zn//V2O5 cells achieved a high discharge capacity of 337.8 mAh g−1 at 0.1 A g−1 and maintained reliable rate performance between 0.2 and 10 A g−1. In addition, ex situ SEM and XRD analyses revealed homogeneous deposition of Zn with a preferred (002) orientation. These findings demonstrate that electrolytes derived from renewable resources provide a cost-effective route for stable and sustainable ZIBs.