Lithium-tin alloy/sulfur battery with a solvate ionic liquid electrolyte

Abstract

The electrochemical properties of a mechanochemically synthesized Li22Sn5 electrode in a solvate ionic liquid-based electrolyte were investigated. The electrolyte was composed of lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]), tetraglyme (G4), and a hydrofluoroether solvent (HFE) in a molar ratio of 1:1:6.2, in which Li+ and G4 formed a 1:1 complex cation of [Li(G4)]+. The Li22Sn5 electrode exhibited an initial discharge capacity of 500mAh g?1 in this electrolyte; however, the capacity decreased with increased numbers of charge-discharge cycles. This was attributed to the Li-Sn alloy's volume change in the electrode during the electrochemical reaction. To examine the behavior of the electrode material in a lithium-sulfur battery, a full cell consisting of a Li22Sn5 anode, S cathode, and [Li(G4)][TFSA]/HFE electrolyte was fabricated. The cell was discharged and charged stably without severe side reactions. The dissolution of lithium polysulfides, reaction intermediates with the sulfur cathode, was effectively suppressed in the electrolyte, leading to efficient charge-discharge cycling of the Li22Sn5-S cell.