| 摘要 |
Provided is a positive active material for a lithium secondary battery, which contains Li x MPO 4 (M is transition metal) and is capable of achieving high discharge capacity even when the atomic ratio of Mn in M of Li x MPO 4 is 85% or more (Mn is inexpensive and is capable of high operating potential). The positive active material is a positive active material for a lithium secondary battery, including a lithium transition metal compound that has an olivine crystal structure and contains at least Ni, Fe, and Mn as transition metal elements, wherein when the sum of mole atoms of Ni, Fe, and Mn of transition metal elements contained in the lithium transition metal compound is expressed as 1, and the mole atomic ratios of Ni, Fe, and Mn are represented by a, b, and c (a + b + c = 1, a > 0, b > 0, c > 0), respectively, the following is satisfied: 0.85 ‰¤ c ‰¤ 0.92 and 0.3 ‰¤ a/(a + b) ‰¤ 0.9, and the discharge capacity of a lithium secondary battery using the positive active material at the seventh cycle is 60 mAh/g or more, or wherein in the Ni a Fe b Mn c triangular phase diagram, (a, b, c) is represented by values on the sides of or within the octagon ABCDEFGH whose vertices are point A (0.09, 0.01, 0.9), point B (0.04, 0.04, 0.92), point C (0.03, 0.05, 0.92), point D (0.027,0.063, 0.91), point E (0.039, 0.091, 0.87), point F (0.075, 0.075, 0.85), point G (0.0915, 0.0435, 0.865), and point H (0.099, 0.011, 0.89). Further, a lithium secondary battery includes a positive electrode containing the positive active material, a negative electrode, and a nonaqueous electrolyte. |
