LITHIUM SECONDARY BATTERY
A lithium secondary battery includes a cathode formed from a cathode active material including a lithium metal oxide particle containing nickel (Ni) and manganese (Mn), an anode formed from an anode active material containing a graphite-based material having a crystal interplanar distance (d002) of 3.356 to 3.365 Å, and a separator interposed between the cathode and the anode. The lithium metal oxide particle includes a concentration gradient region formed between a center of the particle and a surface of the particle, and a ratio of a concentration (atomic %) of Ni with respect to a concentration (atomic %) of Mn at the surface of the lithium metal oxide particle is 0.29 or more and less than 6.
1 . A lithium secondary battery, comprising:
a cathode formed from a cathode active material including a lithium metal oxide particle containing nickel (Ni) and manganese (Mn),
an anode formed from an anode active material containing a graphite-based material having a crystal interplanar distance (d002) of 3.356 to 3.365 Å; and
a separator interposed between the cathode and the anode,
wherein the lithium metal oxide particle includes a concentration gradient region formed between a center of the particle and a surface of the particle, and
a ratio of a concentration (atomic %) of Ni with respect to a concentration (atomic %) of Mn at the surface of the lithium metal oxide particle is 0.29 or more and less than 6.
2 . The lithium secondary battery according to claim 1 , wherein the ratio of a concentration (atomic %) of Ni with respect to a concentration (atomic %) of Mn at the surface of the lithium metal oxide particle is 1.2 to 5.3.
3 . The lithium secondary battery according to claim 1 , wherein a Ni concentration continuously decreases and a Mn concentration continuously increases from the center toward the surface in the concentration gradient region of the lithium metal oxide particle.
4 . The lithium secondary battery according to claim 3 , wherein the lithium metal oxide particle further comprises cobalt (Co),
wherein a concentration of Co is constant from the center to the surface.
5 . The lithium secondary battery according to claim 1 , wherein each of Ni and Mn has a constant concentration gradient slope in the concentration gradient region.
6 . The lithium secondary battery according to claim 5 , wherein a difference in amounts between a concentration gradient slope of Ni and a concentration gradient slope of Mn may be 5% or less in the concentration gradient region.
7 . The lithium secondary battery according to claim 1 , wherein the lithium metal oxide particle includes a core region having constant concentrations of metal elements and embracing at least 50% of a radius of the lithium metal oxide particle from the center.
8 . The lithium secondary battery according to claim 7 , wherein the concentration gradient is extended from a surface of the core region.
9 . The lithium secondary battery according to claim 1 , wherein the lithium metal oxide particle further includes a peripheral portion extending from at least a portion of the surface toward the center and having a constant concentration of metal elements.
10 . The lithium secondary battery according to claim 9 , wherein the concentration gradient region is formed at a region between the core region and the peripheral portion.
11 . The lithium secondary battery according to claim 10 , wherein a distance (depth) in which the peripheral portion extends from a surface of the lithium metal oxide particle to a center is 10 nm to 200 nm.
12 . The lithium secondary battery according to claim 1 , wherein an overall average chemical composition the lithium metal oxide particle is represented by Chemical Formula1 below
Li x Ni a Mn b M3 c O y [Chemical Formula 1]
wherein, in Chemical Formula 1, M 3 includes at least one selected from a group consisting of Co, Na, Mg. Ca, Ti V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga and B, and
0 <x≤ 1.1, 2 ≤y≤ 2.02, 0 ≤a≤ 1, 0 ≤b≤ 1, 0 ≤c≤ 1, 0 <a+b+c≤ 1.
13 . The lithium secondary battery according to claim 1 , wherein the anode active material includes a natural graphite and an artificial graphite.
14 . The lithium secondary battery according to claim 13 , wherein a crystal interplanar distance (d002) of the natural graphite may be 3.356 to 3.360 Å and a crystal interplanar distance (d002) of the artificial graphite may be 3.361 to 3.365 Å.
15 . The lithium secondary battery according to claim 1 , wherein the anode active material includes a natural graphite and an artificial graphite in a weight ratio of more than 0:100 and 90:10 or less.
16 . The lithium secondary battery according to claim 15 , wherein a mixed weight ratio of the natural graphite and the artificial graphite is 10:90 to 50:50.