Difluorobenzene as an Antisolvent for Fluorinated Electrolyte to Achieve Unparalleled Cycle Life of Lithium Metal Battery
Pengfei Liu, Fei Luo, Yuxin Rao, Huasong Wang, Xue Li, Miaomiao Yu, Xiang Liu, Shangquan Zhao, Shan Fang
Abstract
Electrolytes play a crucial role in enhancing the cycling stability and overall lifespan of lithium metal batteries (LMBs). However, conventional electrolytes achieve ununiform and low ionic conductivity solid electrolyte interphase (SEI), leading to uncontrolled lithium dendrite growth and dead lithium formation, rendering them inadequate for meeting the performance of high energy density LMBs. Herein, a 1,2-difluorobenzene (1,2-dFBn) is introduced as antisolvent in fluorinated electrolyte which is composed of fluoroethylene carbonate (FEC) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The low energy level of the lowest unoccupied molecular orbital (LUMO) and the high fluorine-donating ability of 1,2-dFBn jointly modify the solvation structure and electrode/electrolyte interphase chemistry. As a result, this simple electrolyte formulation enables the Li||Li symmetric cells exhibit remarkable stability, enduring 700 h of continuous cycling under 2 mA cm –2 and Li||Cu cell achieve an impressive average Coulombic efficiency (CE) of 99.76%. Moreover, the full cell assembled with electrochemically deposited lithium capacity of 5 mAh cm –2 and LiFePO 4 (LFP) as cathode achieves exceptional performance, maintaining a discharge specific capacity of 134.9 mAh g –1 while retaining 95.1% capacity at 2C after 1000 cycles. This study offers a plausible ratio design for fluorinated electrolyte, which achieving high CE and long-life LMBs.