Furukawa Denchi Kabushiki Kaisha

Masahiro Yamamoto

Kenji Nakano

Toru Mangahara

Satoshi Tanno

Shigeru Sakai

Tomoki Kourakata

Hiroki Ohto

Akira Takamuku

A method of producing an electrode plate used for a lithium secondary battery and a lithium secondary battery containing such an electrode plate. The electrode plate is produced by coating a coating slurry of an active material mixture agent added with oxalic acid on a collector, drying and pressing, so as to obtain an electrode plate improved in charge-discharge cycle characteristics when used in a lithium secondary battery.

Method of producing an electrode plate used for a lithium secondary

A lithium secondary battery including a negative electrode having has been inserted an active material at least one member selected from the group of metallic lithium, lithium alloys and materials which are capable of electrochemically occluding and releasing lithium ions; a positive electrode having an active material consisting of at least one compound which is capable of electrochemically occluding and releasing lithium ions; and an organic electrolyte. The solvent for the organic electrolyte is composed mainly of a mixture solvent prepared by mixing an organic solvent indicated by Formula I, 4-trifluoromethyl-1,3-dioxolane-2-one, and one or two selected from the group of organic solvents indicated by Formula II, 1-trifluoroethylmethyl carbonate, and an organic solvent indicated by Formula III, di-1-trifluorethyl carbonate, as mentioned below. As a result of using the solvent which contains the above-mentioned mixture solvent as a main component for the electrolyte, a lithium secondary battery with improved high-rate discharge characteristics, cycle characteristics and safety characteristics is obtained. ##STR1##

Lithium secondary battery

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 first solvent and at least one kind of low viscous solvents for lowering the viscosity of fluorine substituted propylene carbonates, used as a second solvent. At least one solvent selected from a group of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate and methyl butyl carbonate is preferably used as the second solvent. There can be obtained resultant electrolytes which are excellent in self-extinguishing ability, resulting in high safety and easy in handling, and also 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, energy density, and suppression of the deterioration of the characteristics of the positive electrode, made of one kind of lithium containing complex oxides, during recharging cycles at a deep or large charging depth. When 4-trifluoromethyl-ethylene carbonate is used, the above-mentioned characteristics can be much more improved.

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Iwaki, Japan

Masahiro Yamamoto