Fluoropropanesultone as an SEI-forming additive that outperforms vinylene carbonate

Abstract

Vinylene carbonate (VC) has been the best performing solid electrolyte interphase (SEI) additive for the current lithium-ion batteries (LIBs). However, it is also true that the current LIB technology is being stagnated by the limit set by VC. This study introduces 3-fluoro-1,3-propane sultone (FPS) as a novel SEI additive to replace VC and another popular SEI additive, 1,3-propane sultone (PS). Both density functional calculations and electrochemical experiments confirm that the presence of an electron withdrawing fluorine group is favourable in terms of anodic stability and SEI forming ability. In the cyclability of LiCoO₂/graphite cells over a wide temperature range (25–60 °C), FPS exhibits remarkable enhancement compared with PS, and is even superior to VC. During elevated temperature (90 °C) storage of the cells, VC suffers from severe swelling, whereas FPS causes little thermal degradation. Considering the high anodic stability, the excellent cyclability, and the good thermal stability, FPS is an outstanding SEI additive that can expand the performance boundary of the current LIBs.