Lithium secondary battery
A lithium secondary battery includes a cathode formed of a cathode active material including a lithium metal oxide particle having a concentration gradient, and a coating formed on the lithium metal oxide particle, the coating including aluminum, titanium and zirconium, an anode, and a separator interposed between the cathode and the anode. The cathode active material includes 2,000 ppm to 4,000 ppm of aluminum, 4,000 ppm to 9,000 ppm of titanium and 400 ppm to 700 ppm of zirconium, based on the total weight of the cathode active material. The performance of the secondary battery may be maintained under a high temperature condition.
1. A lithium secondary battery, comprising:
a cathode formed of a cathode active material including a lithium metal oxide particle having a concentration gradient, and a coating formed on the lithium metal oxide particle, the coating including aluminum, titanium and zirconium;
an anode; and
a separator interposed between the cathode and the anode,
wherein the cathode active material includes 2,000 ppm to 4,000 ppm of aluminum, 4,000 ppm to 9,000 ppm of titanium and 400 ppm to 700 ppm of zirconium, based on the total weight of the cathode active material.
2. The lithium secondary battery according to claim 1 , wherein the coating comprises a coating layer covering at least a portion of a surface of the lithium metal oxide particle, or a doping mingled inside the lithium metal oxide particle from a surface of the lithium metal oxide particle.
3. The lithium secondary battery according to claim 1 , wherein the lithium metal oxide particle comprises a core portion, a shell portion, and a concentration gradient region within at least a portion between the core portion and the shell portion.
4. The lithium secondary battery according to claim 1 , wherein the coating further comprises boron.
5. The lithium secondary battery according to claim 4 , wherein the boron is included in 100 ppm to 500 ppm based on the total weight of the cathode active material.
6. The lithium secondary battery according to claim 1 , wherein a ratio of the titanium to the aluminum in the cathode active material is 1.7 to 2.7.
7. The lithium secondary battery according to claim 1 , wherein a ratio of the aluminum to the zirconium in the cathode active material is 4 to 8.
8. The lithium secondary battery according to claim 1 , wherein the lithium metal oxide particle has a secondary particle structure in which primary particles are aggregated.
9. The lithium secondary battery according to claim 8 , wherein the primary particle has a rod shape.
10. The lithium secondary battery according to claim 1 , wherein the lithium metal oxide particle comprises nickel and manganese, and
a concentration of the nickel continuously decreases and a concentration of the manganese continuously increases, from a core portion to a shell portion.
11. The lithium secondary battery according to claim 1 , wherein the lithium metal oxide particle is represented by Chemical Formula 1 below:
Li x Ni a M1 b M2 c O y [Chemical Formula 1]
wherein, in Chemical Formula 1 above, each of M1 and M2 includes at least one selected from a group consisting of Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga and B, and
0<x≤1.1, 1.98≤y≤2.02, 0.6≤a≤0.95 and 0.05≤b+c≤0.4.
12. The lithium secondary battery according to claim 11 , wherein the lithium metal oxide particle is represented by Chemical Formula 2 below:
Li x Ni a Co d Mn e M3 f O y [Chemical Formula 2]
wherein, in Chemical Formula 2 above, M3 includes at least one selected from a group consisting of Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga and B, and
0≤x≤1.1, 1.98≤y≤2.02, 0.75≤a≤0.85, 0.08≤d≤0.12, 0.08≤e≤0.12 and 0.15≤d+e+f≤0.25.
13. The lithium secondary battery according to claim 12 , wherein the cathode active material includes 2,000 ppm to 3,000 ppm of aluminum, 4,000 ppm to 6,000 ppm of titanium and 400 ppm to 500 ppm of zirconium, based on the total weight of the cathode active material.
14. The lithium secondary battery according to claim 11 , wherein the lithium metal oxide particle is represented by Chemical Formula 3 below:
Li x Ni a Co d Mn e M3 f O y [Chemical Formula 3]
wherein, in Chemical Formula 3 above, M3 includes at least one selected from a group consisting of Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga and B, and
0<x≤1.1, 1.98≤y≤2.02, 0.86≤a≤0.9, 0.07≤d≤0.11, 0.01≤e≤0.05 and 0.1≤d+e+f≤0.14.
15. The lithium secondary battery according to claim 14 , wherein the cathode active material includes 2,500 ppm to 3,500 ppm of aluminum, 5,000 ppm to 9,000 ppm of titanium and 400 ppm to 700 ppm of zirconium, based on the total weight of the cathode active material.
16. A method of manufacturing a lithium secondary battery, comprising:
preparing a cathode active material in which a coating is formed on a surface of a lithium metal oxide particle by heat treating the lithium metal oxide particle having a concentration gradient between a core portion, and a surface, and a coating source particle including an aluminum oxide particle, a titanium oxide particle and a zirconium oxide particle, together;
forming a cathode by applying the cathode active material onto a cathode current collector; and
forming an anode to face the cathode with a separator interposed therebetween,
wherein the cathode active material is formed to include 2,000 ppm to 4,000 ppm of aluminum, 4,000 ppm to 9,000 ppm of titanium and 400 ppm to 700 ppm of zirconium, based on the total weight of the cathode active material.
17. The method of manufacturing a lithium secondary battery according to claim 16 , further comprising additional heat treating after mixing the cathode active material in which the coating formed on a surface of the lithium metal oxide particle with a boron source.
18. The method of manufacturing a lithium secondary battery according to claim 16 , further comprising washing the cathode active material before applying the cathode active material.