Aqueous Batteries Operated at −50 °C

Abstract Insufficient ionic conductivity and freezing of the electrolyte are considered the main problems for electrochemical energy storage at low temperatures (low T). Here, an electrolyte with a freezing point lower than −130 °C is developed by using dimethyl sulfoxide (DMSO) as an additive with molar fraction of 0.3 to an aqueous solution of 2 m NaClO 4 (2M‐0.3 electrolyte). The 2M‐0.3 electrolyte exhibits sufficient ionic conductivity of 0.11 mS cm −1 at −50 °C. The combination of spectroscopic investigations and molecular dynamics (MD) simulations reveal that hydrogen bonds are stably formed between DMSO and water molecules, facilitating the operation of the electrolyte at ultra‐low T. Using DMSO as the electrolyte additive, the aqueous rechargeable alkali‐ion batteries (AABs) can work well even at −50 °C. This work provides a simple and effective strategy to develop low T AABs.