Regulating the solvation environment of hybrid electrolytes towards high-temperature zinc-ion storage

Zinc-ion batteries (ZIBs) are being explored as a potential alternative to lithium-ion batteries (LIBs) owning to the growing demand for safer, more sustainable, and cost-effective energy storage technologies. In such systems, electrolytes, as one of the key components, have a decisive impact on their electrochemical performance. However, Zn anodes in traditional aqueous electrolytes exhibit drawbacks such as severe hydrogen evolution reactions, Zn corrosion and passivation especially at high temperatures, leading to poor cycling performance of ZIBs. Herein, we designed and evaluated a series of hybrid electrolytes consisting of zinc tetrafluoroborate hydrate (Zn(BF₄)₂·xH₂O) as the solute and various organic solvents (tetraglyme (G4), propylene carbonate (PC), and dimethylformamide (DMF)) for high-temperature ZIBs. Comparative analysis revealed that G4-based hybrid electrolyte exhibit unique Zn²⁺ solvation structure primarily surrounded by organic solvent rather than H₂O, which substantially reduces H₂O-related side reactions and thus promotes more reversible Zn deposition than PC-based and DMF-based hybrid electrolytes. The superiority of G4-based hybrid electrolyte is further confirmed by long stable cycling life of the corresponding Zn||Zn symmetric cell (>  350 hours) and Zn-ion capacitor full cell (over 1,400 cycles with 90.7% capacity retention) at 60°C.