| 摘要 |
PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery that exhibits excellent charge/discharge cycle characteristics at high temperatures and is excellent in high-temperature storage characteristics and overcharge characteristics.SOLUTION: In a lithium ion secondary battery, a positive electrode contains lithium-containing oxide containing Co and/or Mn as a positive electrode active material, a negative electrode contains, as a negative electrode active material, artificial graphite A having an average particle diameter from more than 15 μm to not more than 25 μm, graphite B having an average particle diameter from not less than 8 μm to not more than 15 μm, the surfaces of the graphite particles being coated with amorphous carbon, and a material S including at least one element selected from the group consisting of Si and Sn, when the sum of all the negative electrode active materials contained in the negative electrode is assumed as 100 mass%, the mixture mass percentage (A+B) of the artificial graphite A and the graphite B contained as negative electrode active materials ranges from not less than 40% to not more than 99%, the mass ratio (A/B) of the artificial graphite A to the graphite B ranges from not less than 0.5 to not more than 4.5, and non-aqueous electrolyte contains LiBFof 0.05 to 2.5 mass%, a nitrile compound of 0.05 to 5.0 mass% and LiPF.SELECTED DRAWING: None |
