| 摘要 |
The present invention provides a lithium ion secondary battery which has high energy density and low internal resistance. The active material of a positive electrode (5) of a lithium ion secondary battery according to the present invention is represented by general formula LiaNibCocAdBeO2 (wherein a, b, c, d, e, A and B satisfy 1.0 ≤ a ≤ 1.1, 0.50 ≤ b ≤ 0.90, 0.05 ≤ c + d ≤ 0.5 and 0 ≤ e ≤ 0.005; A includes at least one of Mn and Al; and B includes at least one of Mg, Mo, W and Zr), and a negative electrode (6) comprises a first active material containing graphite and an Si alloy or a second active material containing graphite and SiOx. The ratio of the mass D of the graphite to the mass E of the Si alloy in the first active material, namely (D/E) satisfies 0.67 ≤ (D/E) ≤ 32.3, and the ratio of the mass F of the graphite to the mass G of the SiOx in the second active material, namely (F/G) satisfies 1.5 ≤ (F/G) ≤ 32.3. |
