CATHODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY INCLUDING THE SAME
A cathode active material for a lithium secondary battery according to embodiments of the present invention has a high-nickel composition and includes a lithium-nickel composite metal oxide particle in which lithium, nickel and a metal having an oxidation number of +2 are combined in a predetermined range. A cation disorder caused when a nickel ion is present at a lithium-ion site is reduced to improve structural stability of the cathode active material. An initial capacity and a battery efficiency of a lithium secondary battery can be improved using the cathode active material.
1 . A cathode active material for a lithium secondary battery comprising a lithium-nickel composite metal oxide particle represented by Chemical Formula 1:
Li a Ni x M1 y M2 1-x O b [Chemical Formula 1]
wherein, in Chemical Formula 1, 0<a≤1.1, 1.98≤b≤2.2, 0.8≤x≤0.98, y is a molar ratio of M1 corresponding to a weight greater than 0 wt % and 2.5 wt % or less of a weight of Ni, and
M1 is at least one element selected from the group consisting of Ca, Sr, Ba and Ra, and M2 is at least one element having a positive oxidation number excluding +2.
2 . The cathode active material for a lithium secondary battery according to claim 1 , wherein M2 comprises Co and Mn.
3 . The cathode active material for a lithium secondary battery according to claim 2 , wherein M2 further comprises at least one of Al and Ti.
4 . The cathode active material for a lithium secondary battery according to claim 2 , wherein M2 further comprises Al, and a content of Al based on a total weight of the lithium-nickel composite metal oxide particle is in a range from 3,000 ppm to 7,000 ppm.
5 . The cathode active material for a lithium secondary battery according to claim 1 , wherein M1 comprises at least one of Sr and Ba.
6 . The cathode active material for a lithium secondary battery according to claim 1 , wherein, in Chemical Formula 1, 0.83≤x≤0.98.
7 . The cathode active material for a lithium secondary battery according to claim 1 , wherein, in Chemical Formula 1, 0.88≤x≤0.98.
8 . The cathode active material for a lithium secondary battery according to claim 1 , wherein M1 comprises at least of Sr and Ba, and M2 comprises Al.
9 . The cathode active material for a lithium secondary battery according to claim 8 , wherein a ratio of a total content of Sr and Ba in the lithium-nickel composite metal oxide particle relative to a content of Al in the lithium-nickel composite metal oxide particle is in a range from 0.15 to 1.5.
10 . The cathode active material for a lithium secondary battery according to claim 1 , wherein M1 comprises Sr, and M2 comprises Al and Ti.
11 . The cathode active material for a lithium secondary battery according to claim 1 , wherein M1 comprises Sr, and M2 comprises Al and Zr.
12 . The cathode active material for a lithium secondary battery according to claim 1 , wherein M1 comprises Sr, and M2 comprises Al, Ti and Zr.
13 . The cathode active material for a lithium secondary battery according to claim 1 , wherein M1 comprises Sr and Ba, and M2 comprises at least one element selected from Al, Ti and Zr.
14 . The cathode active material for a lithium secondary battery according to claim 1 , wherein M1 comprises Sr and Ba, and M2 comprises Al, Ti and Zr.
15 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium-nickel composite metal oxide particle has a secondary particle structure in which a plurality of primary particles are aggregated.
16 . The cathode active material for a lithium secondary battery according to claim 15 , further comprising at least one of a metal sulfate component, a metal carbonate component and a metal oxide component which is present between the primary particles.
17 . The cathode active material for a lithium secondary battery according to claim 16 , wherein the metal sulfate component, the metal carbonate component and the metal oxide component each contains M1 of Chemical Formula 1.
18 . A lithium secondary battery, comprising:
a cathode comprising the cathode active material for a lithium secondary battery of claim 1 ; and an anode facing the cathode.