Cathode active material
The inventive concept discloses a cathode active material containing crystal water and a manganese-based metal oxide.
1 . A cathode active material containing:
crystal water and a manganese-based metal oxide,
wherein the cathode active material includes a first crystal phase having a two-dimensional crystal structure and a second crystal phase having a three-dimensional crystal structure,
wherein the first crystal phase is a thermodynamically stable two-dimensional layered crystal structure where a unit lattice structure composed of the manganese-based metal oxide, and having manganese filling octahedral sites of a unit lattice where manganese and oxygen are bonded to each other is two-dimensionally extended,
wherein the second crystal phase is a thermodynamically metastable three-dimensional crystal structure where, as some manganese in the manganese-based metal oxide forming the layered structure is chemically bonded to oxygen in the crystal water, a unit lattice structure having manganese filling octahedral sites of a unit lattice and a unit lattice structure having manganese filling tetrahedral sites are mixed,
wherein the two-dimensional crystal structure includes two or more unit layers composed of a manganese oxide, and contains a first metal element and a second metal element disposed between the two or more unit layers,
wherein the first metal element is at least one metal element selected from a group consisting of an alkali metal element and an alkaline earth metal element, and the second metal element is at least one metal element selected from a group consisting of a post-transition metal element.
2 . The cathode active material of claim 1 , wherein the cathode active material is expressed by a following [Chemical Formula 1]
Me x Do y MnO 2 ·z H 2 O [Chemical Formula 1]
in Chemical Formula 1, the Me is the first metal element,
the dopant (Do) is the second metal element, and
0.23≤x≤1, 0.01≤y≤1, and 0.01≤z≤0.5.
3 . The cathode active material of claim 2 , wherein the Me is at least one element selected from Li, Na, and K.
4 . The cathode active material of claim 2 , wherein the dopant is at least one element selected from Al, Mg, Cu, Zn, and Fe.
5 . The cathode active material of claim 2 , wherein the Me and the dopant are composed of different elements.