Affiliation:
1. Key Laboratory for Green Chemical Technology of Ministry of Education School of Chemical Engineering and Technology Tianjin University 300072 Tianjin China
2. Cell Product Department Contemporary Amperex Technology Co., Ltd. 352100 Ningde China
3. State Key Laboratory of Metal Matrix Composites School of Materials Science and Engineering Shanghai Jiao Tong University 200240 Shanghai China
4. Zhang jiang Institute for Advanced Study Shanghai Jiao Tong University 200240 Shanghai China
Abstract
AbstractCoulombic efficiency of over 99 % is rarely achieved for Li metal anode below −40 °C, hindering the practical application of high‐energy‐density Li metal batteries under extreme conditions. Herein, limiting factors for Li metal reversibility are investigated utilizing ether‐based localized high‐concentration electrolytes of different solvent‐diluent combinations. We find that along with the desolvation barrier, bulk ion transport properties including ionic conductivity, transference number, and diffusivity are also crucial factors for low‐temperature Li deposition behavior. Superior Li metal reversibility was observed within the combination of the solvent with moderately weak solvating power and the diluent with minimal viscosity, highlighting the role of ion transport and the necessity for a trade‐off with desolvation. The optimized electrolyte composed of lithium bis(fluorosulfonyl)imide, methyl n‐propyl ether, and 1,1,2,2‐tetrafluoroethyl methyl ether delivers exceptional Coulombic efficiency of 99.34 % at −40 °C and 98.96 % at −60 °C under a current density of 0.5 mA cm−2. Furthermore, Li||LiCoO2 (2.7 mAh cm−2) cells demonstrate impressive reversible capacity and cycling stability at these temperatures. This work sheds light on the less‐recognized relevance of bulk ion transport to low‐temperature performance and provides guidelines for the electrolyte design of Li metal batteries operating in cold environments.