Synthesis and Electrochemical Properties of Electrolytes Based on Phosphonium, Sulfonium and Imidazolium Ionic Liquids for Li-Ion Batteries

This work describes synthesis and characterization of three ionic liquids (IL) with imidazolium, phosphonium or sulfonium cations. These ILs were used as precursors for the preparation electrolytes by adding various types lithium salts. Thermal electrochemical properties studied to assess their feasibility usage in lithium-ion batteries (LIB). Ethylmethylimidazolium phosphonic acid ethyl ester [EtMeIm]+[EtPITE]– added Li salts showed very low conductivities about 0.02 mS cm–1 a rather narrow stability window 4.3 V. Of all under study, this imidazolium-based IL exhibited worst thermal both neat additional Li+ salt. Therefore, using an electrolyte LIB is unlikely. Methyl­tributylphosphonium bis(trifluoromethyl sulfonyl) imide [P1444]+[TFSI]– had already significantly higher 0.4–0.6 wide 7 TGA curves show excellent up 300 °C. DSC measurements semicrystalline behaviour [P1444]+[TFSI]–; unfavourable fact was overcome addition Potential high use LIB. At room temperature, trimethylsulfonium [S111]+[TFSI]– solid crystalline material, so it mixed [P1444]+[TFSI]–. The resulting mixture [P1444]+[S111]+[TFSI]– achieved highest 0.6–1.0 comparison other prepared ILs. also interesting, its ESW value being 5.5 are comparable those [P1444]+[TFSI]–, but does not behaviour. promising LIB.
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