Cold‐Optimized Zinc‐Ion Batteries: Enhanced Stability at −5 °C

Aqueous zinc-ion batteries (AZIBs) have been extensively studied under room and ultralow temperature conditions. However, mechanism studies at intermediate temperature ranges remain limited. In this work, we investigate the electrochemical performance of an AZIB using a commonly employed 3 M ZnSO₄ electrolyte across the intermediate temperature range of 25 to -15 °C. Notably, we find that the battery with a double hydroxide cathode exhibits optimized performance at -5 °C, demonstrating significantly enhanced cycling stability compared to 25 °C. Mechanistic studies reveal that unfavorable H⁺-associated reactions at both the cathode and anode are effectively alleviated at -5 °C, contributing to improved cycling stability. Spectroscopic and theoretical analyzes show that changes in the electrolyte environment at -5 °C-such as reduced electrochemical activity of H₂O, increased H-bond strength, and decreased total number of H bonds-impede H⁺ diffusion through H-bond network via the Grotthuss mechanism. These effects collectively suppress harmful H⁺-associated reactions, allowing Zn²⁺ insertion/deinsertion to dominate the charge storage process. This work provides valuable insights into the enhanced performance of AZIBs at sublow temperatures and presents opportunities for extending battery operation in near-freezing environments.