Stable non-corrosive sulfonimide salt for 4-V-class lithium metal batteries

Lithium bis(trifluoromethanesulfonyl)imide is used as a conducting salt for rechargeable lithium metal batteries because of its stability, but corrosion with aluminium current collectors is an issue. A non-corrosive sulfonimide salt is shown to suppress anodic dissolution of an Al current collector at high potentials while improving cycling. Rechargeable lithium metal (Li-0) batteries (RLMBs) are considered attractive for improving Li-ion batteries. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) has been extensively used as a conducting salt for RLMBs due to its advantageous stability and innocuity. However, LiTFSI-based electrolytes are corrosive towards aluminium (Al-0) current collectors at low potentials (>3.8 V versus Li/Li+), thereby excluding their application in 4-V-class RLMBs. Herein, we report on a non-corrosive sulfonimide salt, lithium (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide (LiDFTFSI), that remarkably suppresses the anodic dissolution of the Al-0 current collector at high potentials (>4.2 V versus Li/Li+) and significantly improves the cycling performance of Li(Ni1/3Mn1/3Co1/3)O-2 (NMC111) cells. In addition, this sulfonimide salt results in the growth of an advantageous solid electrolyte interphase on the Li-0 electrode. The replacement of either LiTFSI or LiPF6 with LiDFTFSI endows a Li-0 parallel to NMC111 cell with superior cycling stability and capacity retention (87% at cycle 200), demonstrating the decisive role of the salt anion in dictating the electrochemical performance of RLMBs.

Automated summary

A non-corrosive sulfonimide salt is found to suppress corrosion of aluminum current collectors and improve the cycling performance of lithium metal batteries.