Cathode active material for secondary batteries and secondary battery including the same
Provided is a cathode active material including a complex coating layer, which includes M below, formed on a surface of the cathode active material through reaction of a lithium transition metal oxide represented by Formula 1 below with a coating precursor: Li x MO 2 (1) wherein M is represented by Mn a M′ 1-b , M′ is at least one selected from the group consisting of Al, Mg, Ni, Co, Cr, V, Fe, Cu, Zn, Ti and B, 0.95≤x≤1.5, and 0.5≤a≤1. The lithium secondary battery including the cathode active material exhibits improved lifespan and rate characteristics due to superior stability.
1. A cathode active material comprising a complex coating layer, over a surface of a lithium transition metal oxide represented by Formula (1):
Li x MO 2 (1)
wherein M represents Mn a M′ 1-b ,
wherein M′ is at least one selected from Al, Mg, Ni, Co, Cr, V, Fe, Cu, Zn, Ti or B,
wherein 0.95≤x≤1.5, 0.5≤a≤1, and b=a+x−1,
wherein the complex coating layer has at least one combination structure selected from Li-M-X, Li-M-m or Li-M-X-m,
wherein X is a halogen element derived from a first coating precursor,
wherein m is a metal element derived from a second coating precursor, and
wherein the first coating precursor is an organic or inorganic compound comprising a halogen element, X, and X is F, Cl, Br or I, and the second coating precursor is an oxide or organic matter comprising a metal, m, and the metal, m, is at least one selected from the group consisting of Al, Ba, Ca, Mg, Si, Ti, Zr, Zn, and Sr derived from the oxide.
2. The cathode active material according to claim 1 , wherein the complex coating layer is prepared by: mixing and reacting the lithium transition metal oxide with the first coating precursor and the second coating precursor, and
wherein the lithium transition metal oxide is mixed with the first coating precursor and the second coating precursor in a dry method.
3. The cathode active material according to claim 1 , wherein the organic compound is any one selected from PVdF, PVdF-HFP, PVF, PTFE or ETFE.
4. The cathode active material according to claim 1 , wherein the first coating precursor is PVdF.
5. The cathode active material according to claim 1 , wherein the second coating precursor is C 9 H 21 O 3 Al.
6. The cathode active material according to claim 1 , wherein the complex coating layer is formed on an area of 60% to 100% of the surface area of the lithium transition metal oxide particles.
7. The cathode active material according to claim 1 , wherein, in the complex coating layer, an amount of X is 0.01 to 1.00 wt % based on a total weight of the cathode active material, and an amount of m is 0.01 to 0.50 wt % based on a total weight of the cathode active material.
8. A cathode mixture comprising the cathode active material according to claim 1 .
9. A cathode for secondary batteries cathode, wherein the cathode mixture according to claim 8 is coated over a collector.
10. A secondary battery comprising the cathode for the secondary batteries according to claim 9 .
11. The secondary battery according to claim 10 , wherein the secondary battery is a lithium secondary battery.
12. The cathode active material according to claim 1 , wherein the first coating precursor is an inorganic compound comprising a halogen element, X, and X is F, Cl, Br or I, and
wherein the inorganic compound is a lithium salt or an ammonium salt comprising a halogen element.