Positive electrode active material for secondary battery, and secondary battery including the same
The present invention provides a positive electrode active material for secondary battery and a secondary battery including the same. The positive electrode active material includes a core including a lithium composite metal oxide of Formula 1 below, a first surface-treated layer positioned on the surface of the core and including a lithium oxide of Formula 2 below, and a second surface treated layer positioned on the core or the first surface-treated layer and including a lithium compound of Formula 3. Thus, the present invention can improve capacity characteristics and output characteristics of a battery and also reduce the generation of gas, Li a Ni 1-x-y Co x M1 y M3 z M2 w O 2 [Formula 1] Li m M4O (m+n)/2 [Formula 2] Li p M5 q A r [Formula 3] (in formulae 1 to 3, A, M1 to M5, a, x, y, z, w, m, n, p, and q are the same as those defined in the specification).
1. A positive electrode active material for a secondary battery, the positive electrode active material comprising:
a core comprising a lithium composite metal oxide of Formula 1 below;
a first surface-treated layer positioned on a surface of the core, and including a lithium oxide of Formula 2 below; and
a second surface-treated layer positioned on the core or the first surface-treated layer, and including a lithium compound of Formula 3 below,
Li a Ni 1-x-y Co x M1 y M3 z M2 w O 2 [Formula 1]
(in Formula 1, M1 is at least any one selected from the group consisting of Al and Mn, M2 is any one or at least two elements selected from the group consisting of Zr, Ti, Mg, Ta and Nb, and M3 is any one or at least two elements selected from consisting of W, Mo, and Cr, and 1.0≤a≤1.5, 0<x≤0.5, 0<y≤0.5, 0.002≤z≤0.03, 0≤w≤0.02, 0<x+y≤0.7),
Li m M4O (m+n)/2 [Formula 2]
(in Formula 2, M4 is any one or at least two elements selected from the group consisting of W, Mo, and Cr, and 2≤m≤6, and n is an oxidation number of M4),
Li p M5 q A r [Formula 3]
(in Formula 3, M5 is any one or at least two elements selected from the group consisting of elements in Group 13 to Group 15, A is any one selected from the group consisting of O, OH, CO 3 , PO 4 , F, and SO 4 , and 1≤p≤10, 1≤q≤10, r=(p+s)/t where s is the absolute value of an oxidation number of M5 and t is the absolute value of an oxidation number of A).
2. The positive electrode active material for a secondary battery of claim 1 , wherein M4 in Formula 2 comprises at least any one among W and Cr.
3. The positive electrode active material for a secondary battery of claim 1 , wherein the lithium oxide of Formula 2 comprises any one selected from the group consisting of Li 2 WO 4 , Li 4 WO 5 , and Li 6 WO 6 , or a mixture of at least two thereof.
4. The positive electrode active material for a secondary battery of claim 1 , wherein the first surface-treated layer is formed to have a surface area of 25% or more to less than 100% with respect to an entire surface area of the core.
5. The positive electrode active material for a secondary battery of claim 1 , wherein the first surface-treated layer has an average thickness ratio of 0.001 to 0.1 with respect to a radius of the core.
6. The positive electrode active material for a secondary battery of claim 1 , wherein A in Formula 3 is any one selected from the group consisting of O, PO 4 , and F.
7. The positive electrode active material for a secondary battery of claim 1 , wherein M5 in Formula 3 is any one or at least two elements selected from the group consisting of B, Si, Sn, Bi, and Ge.
8. The positive electrode active material for a secondary battery of claim 1 , wherein the lithium compound of Formula 3 comprises any one selected from the group consisting of LiBO 2 and Li 2 B 4 O 7 , or a mixture of at least two thereof.
9. The positive electrode active material for a secondary battery of claim 1 , wherein the second surface-treated layer is formed to have a surface area of 25% or more to less than 100% with respect to an entire surface area of the core with the first surface-treated layer formed thereon.
10. The positive electrode active material for a secondary battery of claim 1 , wherein the secondary surface-treated layer has an average thickness ratio of 0.001 to 0.1 with respect to a radius of the core.
11. The positive electrode active material for a secondary battery of claim 1 , wherein the core is secondary particles obtained through agglomeration of two or more of primary particles.
12. The positive electrode active material for a secondary battery of claim 1 , wherein M4 element of the lithium oxide of Formula 2 is doped into the core, and the M4 element exhibits a concentration gradient in which an M4 concentration decreases from the surface of the core toward an inside thereof.
13. The positive electrode active material for a secondary battery of claim 1 , wherein at least any one of metal element among the nickel, M1, and cobalt exhibits a concentration gradient in which a concentration thereof varies inside the core.
14. The positive electrode active material for a secondary battery of claim 1 , wherein each of the nickel, M1, and cobalt exhibits a concentration gradient in which a concentration thereof independently varies over an entirety of the core,
the nickel has a concentration gradient in which a nickel concentration decreases toward the surface of the core from a center thereof, and
the cobalt and M1 have concentration gradients in which each of concentrations of the cobalt and M1 independently increases toward the surface of the core from the center thereof.
15. The positive electrode active material for a secondary battery of claim 1 , wherein the M1 is manganese (Mn).