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

Abstract 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.