Characteristics of the electrolyte with fluoro organic lithium salts

Some fluoro organic lithium salts have attractive features as organic electrolyte such as solubility, conductivity, and oxidation potentials. The fluoro organic lithium salts with SO2 groups show higher conductivities than those with CO groups. Methide (CF3SO2)3CLi and imide (RfSO2)2NLi salts show higher conductivities than oxide salts RfSO2OLi with only one RfSO2 group. The lithium salts with long fluoroalkyl groups and two or more RfSO2 groups show high oxidation potentials and high aluminum corrosion potentials over 4.3 V. The battery performances of modified imide salts such as (C2F5SO2)2NLi, (C4F9SO2)(CF3SO2)NLi, and ((CF3)2CHOSO2)2NLi are satisfactory. The cycle characteristics of the imide salt cells are better than those of the LiPF6 cell. Especially, the ((CF3)2CHOSO2)2NLi shows the best cycle characteristics. In XPS analysis the anode surfaces of the imide cells are covered with imide salt components.