Solid electrolyte interphase formation in propylene carbonate-based electrolyte solutions for lithium-ion batteries based on the Lewis basicity of the co-solvent and counter anion

Abstract

Propylene carbonate (PC) is widely regarded as the superior organic solvent for lithium-ion batteries used in cold areas owing to its low melting point. However, an effective solid electrolyte interphase (SEI) is not formed in PC-based electrolyte solutions and reversible intercalation and de-intercalation of the lithium ions at the graphite negative electrode do not proceed. This leads to decomposition of the electrolyte solution and exfoliation of the graphite electrode. One solution to this problem is to control the structure of the solvated lithium ions. In this study, we focused on the Lewis basicity of the co-solvent and counter anion in the lithium salt to control the solvation in a PC-based electrolyte solution and form an effective SEI. Triglyme and tetraglyme were used as the co-solvents, and lithium bis(fluorosulfonyl)amide and lithium trifluoromethanesulfonate were used as the anion sources. SEI formation was investigated by charge and discharge measurements and in situ scanning probe microscopy; the obtained results indicated that SEI formation is strongly influenced by the Lewis basicity of the co-solvent and counter anion.