| abstract |
(57) [Abstract] [Purpose] In a lithium secondary battery using a graphite-based material as a negative electrode carbon material, a low-temperature discharge characteristic is obtained without deteriorating the charge / discharge efficiency at room temperature, the large current discharge characteristic, and the cycle characteristic. An excellent lithium secondary battery is provided. A positive electrode containing a lithium composite oxide containing at least one transition metal as an active material, a negative electrode containing a carbon material mainly containing graphite as an active material, and an electrolyte solution containing at least LiPF 6 dissolved in an organic solvent as an electrolyte. In the non-aqueous electrolyte lithium secondary battery having a separator, the organic solvent contains ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, the composition ratio of which is ethylene carbonate, dimethyl carbonate, and the total of ethyl methyl carbonate. The proportions of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate are x, y, and z (unit volume%), respectively. When expressed as 10 ≦ x ≦ 35, 10 ≦ y ≦ 85 and 5 A non-aqueous electrolyte lithium secondary battery, wherein ≦ z ≦ 80. |