Design of a Teflon-Like Anion for Unprecedently Enhanced Lithium Metal Polymer Batteries

Rechargeable lithium metal polymer batteries (LMPBs) utilizing solid polymer electrolytes (SPEs) have gained increasing attention during the past five decades, owing to the superior flexibility, good process-ability, and no-leakage of SPEs versus traditional non-aqueous liquid and inorganic solid electrolytes. Undoubtedly, among all of the SPE components, salt anions have a significant impact on the overall performances of LMPBs. Yet, lithium bis(trifluoromethanesulfonyl)imide, being commonly applied in the prevailing SPEs shows relatively poor interphasial stability toward lithium metal (Li degrees) anode, which greatly impedes the long-term cycling stability of LMPBs. Herein, a Teflon-like sulfonimide salt, lithium bis(n-nonafluorobutanesulfonyl)imide (LiNFSI), is ingeniously selected for modulating the properties of solid-electrolyte-interphases on the anode side, in view of the peculiar film-forming ability of n-nonafluorobutanesulfonyl group. In-depth physical, chemical, and electrochemical characterizations demonstrate that the incorporation of the Teflon-like anion, NFSI-, results in a remarkably enhanced electrochemical stability between Li degrees anode and SPEs, with a negligible expense of ionic conductivities. The Teflon-like sulfonimide anion suggested in this work provides an elegant path toward the wider application of LMPBs in energy storage and electric vehicles in the near future.

Automated summary

Rechargeable lithium metal polymer batteries (LMPBs) with solid polymer electrolytes (SPEs) have gained attention for their flexibility, process-ability, and no-leakage properties. However, the commonly used lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt in SPEs shows poor interphasial stability towards lithium metal anode, affecting the cycling stability. In this study, a Teflon-like sulfonimide salt, lithium bis(n-nonafluorobutanesulfonyl)imide (LiNFSI), is used to modulate the solid-electrolyte interphases on the anode side, resulting in enhanced electrochemical stability without sacrificing ionic conductivity. The Teflon-like sulfonimide anion provides a promising route for the wider application of LMPBs in energy storage and electric vehicles.