Taming the chemical instability of lithium hexafluorophosphate-based electrolyte with lithium fluorosulfonimide salts

Abstract

Undesired chemical degradation of lithium hexafluorophosphate (LiPF6) in non-aqueous liquid electrolytes is a Gordian knot in both science and technology, which largely impedes the practical deployment of large-format lithium-ion batteries (LIBs) in emerging applications (e.g., electric vehicles). From a fresh perspective that the decomposition of LiPF6 in non-aqueous liquid electrolyte is likely to be induced by hydrogen fluoride (HF) and other protic impurities, we herein report the incorporation of lithium fluorosulfonimide salts (LFSs) as an effective and practical applicable strategy for stabilizing LiPF6-based electrolytes. Our results show that LFSs can dramatically stabilize both LiPF6 and carbonate solvents in the electrolyte through chemically removing HF impurities. The HF-removing impact of LFSs to effectively improve the capacity resilience of LIBs is further demonstrated by superior cycling performances of graphite || LiCoO2 cells utilizing the LFS-added electrolytes.