| abstract |
【Task】 Provided is a lithium secondary battery including a positive electrode having a “lithium-excess type” active material and having a high capacity and good charge / discharge cycle performance. [Solution] The positive electrode active material is a lithium transition metal composite oxide having an α-NaFeO 2 structure, and the molar ratio Li / Me between lithium (Li) and the transition metal (Me) containing Co, Ni, and Mn is Li / Me. > 1, and the Mn molar ratio Mn / Me in the transition metal is Mn / Me> 0.5, and the negative electrode active material is a material containing graphite, amorphous carbon and Si as constituent elements; The mass ratio in the negative electrode active material of the amount of Si of the substance containing Si as a constituent element is 0.6 to 1.9%, and the mixture density is 1.39 to 1.54 g / cc. A lithium secondary battery having a high capacity and excellent charge / discharge cycle performance is provided by combining with a negative electrode. [Selection] Figure 2 |