Cathode active material for lithium secondary battery and method of manufacturing the same
A cathode active material for a lithium secondary battery according to exemplary embodiments of the present invention includes a lithium metal oxide particle core part and an organic compound coating layer which includes a functional group containing a sulfur atom. The cathode active material may suppress side reactions with an electrolyte while maintaining the stability of the layered structure of the lithium metal oxide particles, suppress a gelation phenomenon of the slurry during manufacturing a cathode, and maintain the high energy, high output and long life-span characteristics of the lithium secondary battery.
1 . A cathode active material for a lithium secondary battery comprising:
a lithium metal oxide particle core part; and
an organic compound coating layer including an organic compound which includes a functional group containing a sulfur atom,
wherein the organic compound is directly formed on a surface of the lithium metal oxide particle core part,
wherein the organic compound is a disulfide compound represented by Structural Formula 1 or Structural Formula 2, or a compound represented by Chemical Formula 4 below:
wherein, in Structural Formula 1, R 1 to R 4 are each independently hydrogen; an alkyl group having 1 to 10 carbon atoms; an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen is substituted with a hydroxyl group; an alkoxy group having 1 to 10 carbon atoms; a hydroxyl group; an amine group in which at least one hydrogen is unsubstituted or substituted with an alkyl group having 1 to 10 carbon atoms; a mercapto group; or a carboxyl group,
wherein, in Structural Formula 2, R 5 and R 6 are each independently oxygen, and
R 7 and R 8 are each independently hydrogen; an alkyl group having 1 to 10 carbon atoms; an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen is substituted with a hydroxyl group; an alkoxy group having 1 to 10 carbon atoms; a hydroxyl group; an amine group in which at least one hydrogen is unsubstituted or substituted with an alkyl group having 1 to 10 carbon atoms; a mercapto group; or a carboxyl group,
wherein a weight ratio of the lithium metal oxide particles to the organic compound is 99.9:0.1 to 90:10.
2 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the organic compound is at least one selected from the group consisting of compounds of Chemical Formulae 1 and 2 below:
3 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium metal oxide particles include a lithium nickel-based metal oxide represented by General Formula 1 below:
Li x Ni y M y-1 O 2 [General Formula 1]
wherein, in General Formula 1, x and y are in a range of 0.95<x<1.08, and y≥0.5, respectively, and M is at least one element selected from the group consisting of Co, Mn, Al, Zr, Ti, B, Mg and Ba.
4 . The cathode active material for a lithium secondary battery according to claim 3 , wherein, in General Formula 1, y is in a range of 0.8≤y≤0.93.
5 . The cathode active material for a lithium secondary battery according to claim 3 , wherein in General Formula 1, M includes Co and Mn.
6 . The cathode active material for a lithium secondary battery according to claim 3 , wherein the lithium metal oxide particles include a doping or coating including at least one of Al, Zr and Ti.
7 . A lithium secondary battery comprising:
a cathode comprising the cathode active material for a lithium secondary battery according to claim 1 ;
an anode; and
a separation membrane disposed between the cathode and the anode.