Methyl 2,2‐Difluoro‐2‐(Fluorosulfonyl) Acetate as a Novel Electrolyte Additive for High‐Voltage LiCoO<sub>2</sub>/Graphite Pouch Li‐Ion Cells
Fuyou Xiang, Pipi Wang, Hao Cheng
Abstract
Herein, a novel sulfone‐based compound, methyl 2,2‐difluoro‐2‐(fluorosulfonyl) acetate (MDFA) is studied for its effects in improving LiCoO 2 /graphite pouch Li‐ion cell performance at high working voltage (4.45 V). Calculations based on density functional theory (DFT) and electrochemical tests reveal that MDFA can be reduced preferentially compared with the electrolyte solvent. It helps form a robust interface film with high lithium‐ion conductivity, which will greatly reduce the interfacial impedance of cells. The pouch cells containing 1 wt% MDFA show excellent discharge performance at low temperature (−10 °C) and such concentration of MDFA can also inhibit the deposition of lithium on the anode. Moreover, this additive can promote stability of cell cycling at high voltage. The overall results indicate that the MDFA is a low‐impedance additive that can be well applied to improve the property of high‐voltage lithium‐ion batteries.