Lithium—manganese-type solid solution positive electrode material
Provided is a lithium-manganese-type solid solution positive electrode material capable of effectively suppressing gas generation in an initial cycle. Proposed is a lithium-manganese-type solid solution positive electrode material that includes a monoclinic structure of C2/m in a hexagonal structure of a space group R-3m. The lithium-manganese-type solid solution positive electrode material contains a solid solution expressed by a composition formula: xLi 4/3 Mn 2/3 O 2 +(1−x)LiMn α Co β Ni γ O 2 (in the formula, 0.2≦α≦0.6, 0≦β≦0.4, and 0.2≦γ≦0.6). In the composition formula, x is equal to or more than 0.36 and less than 0.50.
1. A lithium-manganese-type solid solution positive electrode material including a monoclinic structure of C2/m in a hexagonal structure of a space group R-3m, wherein the lithium-manganese-type solid solution positive electrode material comprises a solid solution expressed by a composition formula:
xLi4/3Mn 2/3 O 2 +(1−x)LiMn (1-β)/2 Co β Ni (1-β)/2 O 2 (in the formula, β is 0);
and in the composition formula, x is equal to or more than 0.36 and less than 0.48.
2. The lithium-manganese-type solid solution positive electrode material according to claim 1 , wherein in an XRD pattern, in addition to a peak that belongs to the hexagonal structure of the space group R-3m, a peak which does not belong to the hexagonal structure of the space group R-3m but belongs to the monoclinic structure of C2/m is present at 2θ=19.5 to 23.0°.
3. The lithium-manganese-type solid solution positive electrode material according to claim 1 , wherein a c-axis length of a crystal lattice in the hexagonal structure of the space group R-3m is 14.255 Å to 14.275 Å.
4. The lithium-manganese-type solid solution positive electrode material according to claim 1 , wherein in an XRD pattern that is obtained by XRD measurement, a ratio of the sum area of peaks located within a range of θ=19.5° to 23.5° to the total area obtained by adding the sum area of peaks located within a range of θ=18.0° to 19.5° and the sum area of peaks located within a range of θ=43.0° to 46.0° is 0.145 to 0.185.
5. The lithium-manganese-type solid solution positive electrode material according to claim 1 , wherein in the composition formula, as a substitution element of the metal elements other than Li, one or two kinds selected from a group consisting of Nb, V, Mg, Al, and Ti are contained, and the total content of the substitution element is 10% by mole or less of the number of moles of the metal elements other than Li.
6. The lithium-manganese-type solid solution positive electrode material according to claim 1 , wherein the lithium-manganese-type solid solution positive electrode material further contains B (boron).