Mixture of monoglyme-based solvent and lithium Bis(trifluoromethanesulfonyl)amide as electrolyte for lithium ion battery using silicon electrode

Abstract The electrochemical property of a silicon electrode in a half-cell was investigated using the mixture of monoglyme-based solvents and lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) with 2:1 stoichiometry. The solvents used in this study are monoglyme (G1), 1,2-diethoxyethane (DEE), 1,2-dibutoxyethane (DBE), and 1,2-dimethoxypropane (P-G1). When Li (DEE) 2 or Li(P-G1) 2 was used, the cell retained ca. 20% capacity at a rate of 3 C, while the other samples showed almost no capacity under the same conditions. Raman spectroscopy measurement revealed that Li + exists as two forms in the mixture, that is, a solvent shared ion pair (SSIP) [ Li + ··· solvent ··· TFSA – ] and a contact ion pair (CIP) [ Li + ··· TFSA – ]. According to the spectroscopic analysis, SSIP is the dominant species for Li (DEE) 2 and Li(P-G1) 2 , and CIP for Li (G1) 2 and Li (DBE) 2 . The order of the rate property was Li(P-G1) 2  ∼ Li (DEE) 2  > Li (DBE) 2  ∼ Li (G1) 2 , which is almost consistent with the stability of free energy levels of Li + in the respective monoglymes against CIP Li + ··· TFSA – evaluated from the Raman spectra.