Lithium tris[3-fluoro-1,2-benzenediolato(2-)-O,O′]phosphate as a novel lithium salt for lithium battery electrolytes

We have synthesized a novel lithium salt with a chelate compound of phosphorus, lithium tris[3-fluoro-1,2-benzenediolato(2-)-O,O']phosphate (3-FLTBP). The thermal stability and electrolytic properties of 3-FLTBP, and the coulombic efficiency of the deposition/dissolution cycling for a lithium metal (lithium electrode cycling efficiency! are investigated. 3-FLTBP is more thermally stable than lithium tris[1,2-benzenediolato(2-)-O,O']phosphate (LTBP) and lithium tris[4-methyl-1,2-benzenediolato(2-)O, O']phosphate (4-MLTBP), which we previously synthesized. The electrochemical stability in propylene carbonate solutions and the specific conductivities in ethylene carbonate-dimethyl carbonate (mole ratio 1: 1) binary solutions decrease in the following ascending order: 3-FLTBP, LTBP, and 4-MLTBP. The mixing of the lithium organophosphate and LiPF6 enhances the cycling efficiency over the range of high cycle numbers. (C) 2002 The Electrochemical Society.