Chaotropic Anion and Fast-Kinetics Cathode Enabling Low-Temperature Aqueous Zn Batteries

Abstract Operating at low temperatures is a great challenge that hinders the practical application of aqueous batteries at subzero temperatures. The frozen electrolyte and the limited capacity of the cathode at low temperatures are the main reasons. Herein, we report synthetic electrolyte/cathode design strategies for low-temperature aqueous Zn batteries. The fundamental correlations between anion chemistries and freezing point depression of water are revealed by multi-perspective characterization. Coupled with the chaotropic anion, CF3SO3–, the 2 M zinc electrolyte features a low freezing point of −34.1 °C and high ionic conductivity of 4.47 mS cm–1 at −30 °C. With the benefits of the low-temperature electrolyte and fast-kinetics cathode, Zn||V2O5 batteries deliver a high specific capacity of 285.0 mAh g–1 at −30 °C with capacity retention of 81.7% after 1000 cycles. This work points out the fundamental understanding of anion chemistries and synthetic design strategies for developing low-temperature aqueous batteries.