High performance Zn-I₂ battery with acetonitrile electrolyte working at low temperature

Large scale applications of metal-iodine batteries working at sub-zero degree have been challenged by the limited capacity and performance degradation. Herein, we firstly propose a Zn-I₂ battery working at low temperature with a carbon composite material/iodine (CCM-I₂) cathode, a Zn anode and an environmentally tolerable Zn(ClO₄)₂-ACN electrolyte. The CCM framework with hierarchical porous structure endows a powerful iodine-anchoring to overcome undesirable dissolution of iodine in organic electrolyte, and the Zn(ClO₄)₂-ACN electrolyte with low freezing point and high ionic conductivity enhances the low temperature performance. The synergies enable an efficiently reversible conversion of Zn-I₂ battery even at −40 °C. Therefore, the resultant Zn-I₂ battery delivers a high specific capacity of 200 mAh·g⁻¹, which is fairly approximate to the theoretical capacity of I₂ (211 mAh·g⁻¹) and a superior cycling stability with minimal capacity fading of 0.00043% per cycle over 7,000 times under 2C at −20 °C. Furthermore, even at −40 °C, this Zn-I₂ battery still exhibits a good capacity retention of 68.7% compared to the capacity at 25 °C and a rapid capacity-recover ability with elevating temperature change. Our results distinctly indicate this Zn-I₂ battery can be competent for the practical application under low temperature operation.