| abstract |
A lithium secondary battery comprising a positive electrode, a negative electrode and an organic electrolyte, and the electrolyte comprises a solvent mixture of at least one kind of fluorine substituted propylene carbonates used as a primary solvent and at least one kind of low viscous solvents for lowering the viscosity of fluorine substituted propylene carbonates, used as a secondary solvent, and at least one kind selected from a group of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate and methyl butyl carbonate is preferably used as the secondary solvent, so that there can be obtained the resultant electrolytes which is excellent in self-extinguishing ability, resulting in high safety and easy in handling, and also brings about such an improved battery that is excellent in battery performance, discharge characteristics at a low temperature, charge/discharge efficiency of the negative electrode at the initial stage of charge/discharge cycles, a larger energy density, a large effect of suppressing the deterioration of the characteristics of the positive electrode, which is made of one kind of lithium containing complex oxides, at the time of recharging cycles at a deep or large charging depth, etc., and when 4-trifluoromethyl-ethylene carbonate is used, the above-mentioned characteristics can be much more improved. |