N,N-Dimethyl fluorosulfonamide for suppressed aluminum corrosion in lithium bis(trifluoromethanesulfonyl)imide-based electrolytes

Effective passivation of aluminum (Al) current collector at high potentials (> 4.0 V vs. Li/Li⁺) is of essence for the long-term operation of lithium-based batteries. Unfortunately, the non-aqueous liquid electrolytes comprising lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and organic carbonates are corrosive toward Al current collector at high potentials (> 4.0 V vs. Li/Li⁺), despite their intriguing features (e.g., good chemical stability and high ionic conductivity). Herein, we propose the utilization of N,N-dimethyl fluorosulfonamide (DMFSA) as electrolyte solvent for suppressing Al corrosion in the LiTFSI-based electrolytes. It has been demonstrated that the electrolyte of 1.0 M LiTFSI-DMFSA shows decent ionic conductivities (1.76 mS·cm⁻¹ at 25 °C) with good fluidities (2.44 cP at 25 °C). In particular, the replacement of organic carbonates (e.g., ethylene carbonate and ethyl methyl carbonate) with DMFSA leads to significant suppressed Al corrosion. Morphological and compositional characterizations utilizing scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) reveal that DMFSA favors the formation of insoluble species (i.e., aluminum fluoride (AlF₃)) on the surface of Al electrode, which effectively inhibits continuous exposure of fresh Al surface to electrolyte during cycling. This work provides not only a deeper understanding on the Al corrosion in LiTFSI-based electrolyte but also an elegant path to stabilize the Al current collector at high potentials (> 4.0 V vs. Li/Li⁺), which may give an impetus into the development of lithium-based batteries.