Dual-Co-Solvent Electrolyte Engineering for Robust Aqueous Zinc Metal Batteries at 60 °C.

Aqueous zinc metal batteries (AZMBs) with intrinsic high safety are a promising candidate for large-scale energy storage at high temperatures. However, the aggravated water-related side reactions (Zn corrosion, hydrogen evolution, etc.) at elevated temperatures enormously impair the reversibility and cycling stability of AZMBs. Herein, the dual co-solvents, triethyl phosphate and γ-valerolactone, are introduced into the aqueous electrolyte to prepare a hybrid electrolyte for high-temperature AZMBs. Besides the flame resistance, this hybrid electrolyte ensures a highly stable and reversible Zn anode at the high temperature of 60 °C, originating from the remarkably suppressed water reactivity and uniform Zn deposition without dendrites. Consequently, using this hybrid electrolyte and testing at the high temperature of 60 °C, the asymmetric Zn||Cu cell provides an average coulombic efficiency as high as 99.4% over 415 cycles, and the symmetric Zn||Zn cell offers a remarkably long cycle life (1354 h) at 0.5 mA cm^-2 and 0.5 mAh cm^-2. Furthermore, the assembled full cell achieves a decent cycling stability (77.6% capacity retention after 550 cycles) concomitant with an unprecedented duration of 910 h at 60 °C. This work offers new insight into electrolyte engineering strategy for high-performance AZMBs at high temperatures.