Comparative Studies of the Electrochemical and Thermal Stability of Composite Electrolytes for Lithium Battery Using Two Types of Boron-based Anion Receptors

摘要

Comparative studies were done on two new types of boron based anion receptors, tris(pentafluorophenyl) borane (TFPB) and tris(pentafluorophenyl) borate (TFPBO), regarding conductivity enhancement electrochemical and thermal stability when used as additives in composite electrolytes for lithium batteries. Both additives enhance the ionic conductivity of electrolytes of simple lithium salts, LiF, CF(sub 3)CO(sub 2)Li and C(sub 2)F(sub 5)CO(sub 2)Li in several organic solvents. The electrochemical windows of TPFB based electrolytes in ethylene carbonate (EC)-propylene carbonate (PC)-dmethyl carbonate (DMC) (1:1:3, v/v) are up to 5, 4.76 and 4.96 V for LiF, CF(sub 3)CO(sub 2)Li and C(sub 2)F(sub 5)CO(sub 2)Li respectively. TPFBO has lower electrochemical stability compared to TPFB. The thermal stability of pure TFPB is better than TFPBO. The lithium salt complexes have higher thermal stability than these two compounds. TPFB based electrolytes showed high cycling efficiencies and good cycleability when they were tested in Li/LiMn(sub 2)O(sub 4) cells. The capacity retention of the cells using TFPB based electrolytes during multiple cycling is better than those using TFPBO based electrolytes.