Electrolyte Design via Hydrogen Bonding Between Solvent and Non‐Solvating Cosolvent Enabling Stable Lithium Metal Batteries at −20°C
Chuncheng Yan, Houzhen Li, Xiaoru Zhao, Xinrui Ma, Hao Chen, Yuanhua Sang, Hong Liu, Shuhua Wang
Abstract
ABSTRACT Lithium metal batteries (LMBs) have great significance in enhancing energy density. However, low ion diffusion in bulk electrolytes, high desolvation energy of Li + , and sluggish ion transport kinetics in electrode interphases at low temperatures cause LMBs to have a short cycle life (usually below 300 cycles). In this study, we designed a low‐temperature electrolyte to overcome these issues. The medium‐chain length isopropyl formate (IPF) was employed as main solvent in the designed electrolyte. Especially, the hydrogen bonding between non‐solvating cosolvent (1,1,2,2‐tetrafluoroethyl‐2,2,2‐trifluoroethyl ether [TFE]) and IPF can be formed, leading to the weakened interaction between Li + and the solvents. Thus, a fast Li + desolvation can be achieved. Additionally, the designed electrolyte can maintain a high conductivity (6.37 mS cm −1 ) at −20°C and achieve higher Li + transference numbers (0.62). Finally, Li||LiFePO 4 full cells using the designed electrolyte exhibit a capacity of 113 mAh g −1 after 480 cycles at 0.1C under −20°C. Meanwhile, Li||LiFePO 4 can deliver 150 mAh g −1 after 120 cycles at 50°C. This study provides a novel pathway for optimizing electrolytes for next‐generation LMBs during low‐temperature operations.