| abstract |
[PROBLEMS] To provide a lithium secondary battery capable of obtaining a discharge capacity of 200 mAh / g or more even when a charging method in which the maximum potential of the positive electrode during charging is 4.3 V (vs. Li / Li + ) or less is adopted. A positive electrode active material is provided. An active material for a lithium secondary battery including a solid solution of a lithium transition metal composite oxide having an α-NaFeO type 2 crystal structure, wherein the composition ratio of the lithium element and the transition metal element contained in the solid solution is: In the composition formula Li 1 + p Co a Ni b Mn c (a> 0, b> 0, c ≧ 0), the value of 2a + b + 3c is 2 (miscalculation range ± 0.1), and when α = a + 2b, The value is (1-α) × 1/3 (error range ± 0.1), and the value of 1-α exceeds 1/3 and is 2/3 or less. Active material. [Selection] Figure 6 |