Solvation Regulation via Hydrogen Bonding to Mitigate Al Current Collector Corrosion for High‐Voltage Li‐Ion Batteries

Incorporating 2,2,2-trifluoroethyl methanesulfonate into a conventional lithium bis(fluorosulfonyl)imide (LiFSI)-based carbonate electrolyte can precisely tailor the Li⁺ solvation structure by hydrogen-bonding interactions with dimethyl carbonate (DMC) solvent. This interaction weakens the coordination between DMC and Li⁺ while increasing the participation of FSI⁻ anions in the primary solvation shell, effectively suppressing the aluminum corrosion caused by free FSI⁻ anions.

Abstract

The exceptional thermal stability and conductivity of lithium bis(fluorosulfonyl)imide (LiFSI) have made it a preferred salt for lithium-ion batteries (LIBs). However, the corrosion of aluminum (Al) current collectors by LiFSI at low potentials (3.8 V vs Li/Li⁺) poses a persistent challenge, hindering the application of LiFSI in 4 V-class LIBs. Herein, 2,2,2-trifluoroethyl methanesulfonate (TFMS) is proposed as a versatile co-solvent to address the issue of Al current collector corrosion. It is demonstrated that incorporating TFMS into a conventional LiFSI-based carbonate electrolyte can precisely tailor the Li⁺ solvation structure by hydrogen bonding interactions with dimethyl carbonate (DMC) solvent. This weakens the coordination between DMC and Li⁺ while increasing the participation of FSI⁻ anions in the primary solvation shell, effectively suppressing the Al current collector caused by free FSI⁻ anions attacking. Furthermore, TFMS and FSI⁻ synergically induce the formation of an inorganic-rich and compact cathode electrolyte interphase, significantly avoiding undesired side reactions. As a result, the TFMS-electrolyte enables 1.2 Ah-graphite||NCM811 (LiNi_0.8Co_0.1Mn_0.1O₂) pouch-cells to achieve 89.9% capacity retention with high average Coulombic efficiency of >99.9% for 200 cycles at a cut-off voltage of 4.4 V, opening up opportunities for the development of advanced high-voltage LIBs.