Application to lithium battery electrolyte of lithium chelate compound with boron

The electrolytic conductivities and charge-discharge characteristics of Lit hium electrode are examined in propylene carbonate (PC)- and ethylene carbo nate (EC) tetrahydrofurans, such as 2-methyltetrahydrofuran (2-MeTHF) and 2 ,5-dimethyltetrahydrofuran (2,5-DMeTHF), binary solvent electrolytes contai ning lithium bis[1,2-benzenediolato(2-)-O,O ' ]borate (LBBB), Lithium bis[2 ,3-naphthalenediolato(2-)O,O ' ]borate (LBNB), lithium bis[2,2 ' -biphenyld iolato(2-)-O,O ' ]borate (LBBPB) and lithium bis[salicylato(2-)]borate (LBS B). The order of specific conductivities in PC- and EC-based equimolar bina ry solutions containing these organoborates is LBBB greater than or equal t o LBNB > LBSB > LBBPB. The conductivity in LBNB electrolyte with higher vis cosity than that in LBSB electrolyte becomes high. The PC-2-MeTHF and PC-2, 5-DMeTHF equimolar binary solutions containing LBSB and a mixed electrolyte (LBBPB + LiPF6) show very high cycling efficiencies more than 90% at a hig her range of cycle number. The EC-THF and EC-2-MeTHF equimolar binary solut ions are moderate electrolytes with about 80% cycling efficiencies. It is f ound by using scanning electron microscope (SEM) that the films formed on t he electrode in PC-2-MeTHF and PC-2,5-DMeTHF electrolytes with higher cycli ng efficiencies have a homogeneous surface with uniform grain size. (C) 200 1 Elsevier Science B.V. All rights reserved.