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 and having a secondary particle structure in which a plurality of primary particles are aggregated; and
at least one of a metal sulfate component, a metal carbonate component and a metal oxide component which is present between the primary particles in an inner region of the lithium-nickel composite metal oxide particle,
wherein the metal sulfate component, the metal carbonate component and the metal oxide component each contains M1 in 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,
M1 is at least one element selected from the group consisting of Sr and Ra, and M1 is present between the primary particles in the inner region of the secondary particle structure of the lithium-nickel composite metal oxide particle, and
M2 includes Mn and Co,
wherein the cathode active material is made by:
preparing an active material precursor obtained by mixing and reacting active material metal salts;
mixing the active material precursor, a sulfate remaining from the preparation of the active material precursor, M1 source and a lithium source; and
reacting the active material precursor, remaining sulfates, M1 source and a lithium source by a heat treatment to form the at least one of the metal sulfate component, the metal carbonate component or the metal oxide component present between the primary particles in the inner region of the lithium-nickel composite metal oxide particle.
2. The cathode active material for a lithium secondary battery according to claim 1 , wherein a weight ratio of M1 is from 0.01 wt % to 1.4 wt % based on the weight of Ni.
3. The cathode active material for a lithium secondary battery according to claim 1 , wherein, in Chemical Formula 1, 0.0002≤y≤0.02.
4. The cathode active material for a lithium secondary battery according to claim 1 , wherein, in Chemical Formula 1, 0.001≤y≤0.01.
5. The cathode active material for a lithium secondary battery according to claim 1 , wherein, in Chemical Formula 1, M2 further comprises at least one element selected from the group consisting of B, Al, Si, Ti, V, Fe, Cu, Zn, Y, Zr, Mo, Sn and W.
6. The cathode active material for a lithium secondary battery according to claim 1 , wherein, in Chemical Formula 1, 0.8≤x≤0.95.
7. A lithium secondary battery, comprising:
a cathode comprising the cathode active material layer for a lithium secondary battery of claim 1 ; and
an anode facing the cathode.