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

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(Ni 1/3 Mn 1/3 Co 1/3 )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 LiPF 6 with LiDFTFSI endows a Li 0 ||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.