Effects of non-equimolar lithium salt glyme solvate ionic liquid on the control of interfacial degradation in lithium secondary batteries

Abstract

Control of interfacial properties between the electrode and electrolyte is important for obtaining long life-cycle lithium-ion secondary batteries. To control interfacial degradation, we investigated the effect of changing the composition ratio of lithium salt (LiN(SO₂CF₃)₂) and low-molecular-weight ether (CH₃–O–(C₂H₄O)₃–CH₃) in the system. A highly electrochemically stable lithium salt glyme solvated ionic liquid electrolyte was realized, with long-lived, robust lithium solvation complexes by increasing the lithium salt composition ratio. Lithium secondary batteries using the electrolyte show notable suppression of the degradation of interfacial resistance at the interface of the electrolyte and the positive electrode (high oxidation state), which leads to a longer life-cycle of the batteries.