Non-aqueous liquid electrolyte secondary battery

Abstract

A non-aqueous liquid electrolyte secondary battery including an anode formed of a carbon material capable of doping and de-doping of lithium, a cathode formed of a lithium-containing transition metal composite oxide and a non-aqueous liquid electrolyte is disclosed. The carbon material for the anode contains graphite and a non-graphitic carbon material formed of at least a non-graphitizable carbon material or a graphitizable carbon material. The non-graphitic carbon material preferably exhibits a discharge capacity per gram 80% or more of that of the graphite, measured in the first cycle of intermittent charging and discharging. The non-graphitic carbon material exhibits a ratio of a discharge capacity up to 0.3 V to a discharge capacity up to 1.5 V which is not smaller than 0.5, measured in the first cycle of intermittent charging and discharging with a standard of a lithium potential. Specifically, the graphite has a true density of 2.1 g/cm.sup.3 or greater, an interplanar distance of (002) of less than 0.340 nm found by X-ray diffraction, and a C-axis crystallite size of the (002) plane of 14.0 nm or greater. The non-graphitic carbon material has a true density of 1.70 g/cm.sup.3 or smaller, an interplanar distance of (002) plane of 0.37 nm or greater, and no exothermic peak observed at temperatures not lower than 700.degree. C. in differential thermal analysis in an air stream. The non-aqueous liquid electrolyte is a liquid electrolyte formed by dissolving an electrolyte into a non-aqueous solvent containing ethylene carbonate.