Cathode active material for lithium secondary battery and lithium secondary battery including the same
The cathode active material for a lithium secondary battery includes lithium-transition metal composite oxide particles having a crystal grain size of less than 300 nm measured through XRD analysis and an XRD peak intensity ratio of 7% or more. The present invention provides a lithium secondary battery with improved life-span properties and output properties by controlling the crystal grain size and XRD peak intensity ratio of lithium-transition metal composite oxide particles.
1 . A cathode active material for a lithium secondary battery, comprising lithium-transition metal composite oxide particles having a crystal grain size measured through X-ray diffraction (XRD) analysis of 100 nm or more and less than 300 nm and having an XRD peak intensity ratio defined by Equation 2 of 9% to 11%,
wherein the lithium-transition metal composite oxide particles include nickel, cobalt and manganese, and
a molar ratio of nickel of the lithium-transition metal oxide particles based on total moles of metals excluding lithium is 0.8 or more:
XRD peak intensity ratio (%)=100× I (110)/{ I (110)+ I (003)} [Equation 2]
wherein, in Equation 2, I(110) is a maximum height of a peak of a (110) plane of the lithium-transition metal composite oxide particles by the XRD analysis, and I(003) is a maximum height of a peak of a (003) plane of the lithium-transition metal composite oxide particles by the XRD analysis, and
wherein the crystal grain size is measured through Equation 1:
L
=
0
.
9
λ
β
cos
θ
[
Equation
1
]
wherein, in Equation 1, L is the crystal grain size in nm, λ is an X-ray wavelength in nm, β is a full width at half maximum (rad) of the peak of the (003) plane, and θ is a diffraction angle in radian.
2 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium-transition metal composite oxide particles have the crystal grain size of 150 to 265 nm.
3 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium-transition metal composite oxide particles have an XRD peak area ratio defined by Equation 3 of 16% or more:
XRD peak area ratio (%)=100× A (110)/{ A (110)+ A (003)} [Equation 3]
wherein, in Equation 3, A(110) is a peak area of the (110) plane of the lithium-transition metal composite oxide particles by the X-ray diffraction (XRD) analysis, and A(003) is a peak area of the (003) plane by the XRD analysis.
4 . The cathode active material for a lithium secondary battery according to claim 3 , wherein the lithium-transition metal composite oxide particles have the XRD peak area ratio of 16 to 19%.
5 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium-transition metal composite oxide particles have a particle diameter (D 50 ) of 3 to 16 μm.
6 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium-transition metal composite oxide particles have a particle diameter of 10 to 15 μm.
7 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium-transition metal composite oxide particles have a composition represented by Formula 1 below:
Li x Ni 1−y MyO 2+z [Formula 1]
wherein, in Formula 1, x, y and z are in a range of 0.95x≤1.2, 0≤y≤0.2, and −0.1≤z≤0.1, respectively, and M is Co and Mn.
8 . The cathode active material for a lithium secondary battery according to claim 7 , wherein the lithium-transition metal composite oxide particles are prepared by reacting a transition metal precursor with a lithium precursor.
9 . The cathode active material for a lithium secondary battery according to claim 8 , wherein the transition metal precursor is a Ni—Co—Mn precursor.
10 . The cathode active material for a lithium secondary battery according to claim 7 , wherein y of Formula 1 is 0.1 or less.
11 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium-transition metal composite oxide particles have a coating element,
and the coating element includes at least one element selected from a group consisting of Al, Ti, Ba, Zr, Si B, Mg and P.
12 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium-transition metal composite oxide particles have a doping element,
and the doping element includes at least one element selected from a group consisting of Al, Ti, Ba, Zr, Si B, Mg and P.
13 . A lithium secondary battery comprising:
a cathode comprising a cathode active material layer including the cathode active material according to claim 1 ; and
an anode facing the cathode.
14 . The lithium secondary battery of claim 13 , wherein the anode comprises an anode current collector and an anode active material layer coating the anode current collector.