Lithium Secondary Batteries Using a Lithium Nickelate-Based Cathode and Phosphonium Ionic Liquid Electrolytes

The charge-discharge properties of lithium-battery cells consisting of a LiNi0.8Co0.1Mn0.1O2 cathode and lithium-binary phosphonium ionic liquid electrolytes are reported. Triethyl(2-methoxyethyl)phosphonium bis(trifluoromethylsulfonyl) imide and triethyl-pentylphosphonium bis(trifluoromethylsulfonyl)imide were used as electrolytes. It was found that the cell containing triethyl(2-methoxyethyl) phosphonium bis(trifluoromethylsulfonyl)imide as electrolyte showed higher discharge capacities than that containing the corresponding ammonium ionic liquid electrolyte. Relatively low coulombic efficiencies for the phosphonium ionic liquid electrolytes were observed when compared to that for the corresponding ammonium ionic liquid electrolyte. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.3054290] All rights reserved.