Cathode active material for lithium secondary battery and method of manufacturing the same
A cathode active material for a lithium secondary battery includes a lithium metal oxide particle and a thio-based compound formed on at least portion of a surface of the lithium metal oxide particle. The thio-based compound has a double bond that contains a sulfur atom. Chemical stability of the lithium metal oxide particle may be improved and surface residues may be reduced by the thio-based compound.
1. A cathode active material for a lithium secondary battery, comprising:
a lithium metal oxide particle; and
a thio-based compound formed on at least portion of a surface of the lithium metal oxide particle, the thio-based compound including a thioamide compound represented by Structural Formula 1,
wherein the thio-based compound forms a coating layer, a ligand bond or a complex bond on the surface of the lithium metal oxide particle:
wherein, in the Structural Formula 1 above, R 1 represents hydrogen, halogen, a salt containing O − or S − , a C1-C10 hydrocarbon group capable of substituted with a substituent group, a C1-C10 alkoxy group, an amine group, an amine group substituted with a C1-C10 alkyl group, a C1-C10 thioalkyl group or a thioamide group,
wherein R 2 and R 3 are each independently hydrogen or a C1-C10 hydrocarbon group capable of substituted with a substituent group, R 2 and R 3 are capable of being fused together to form a ring, and
wherein the substituent group capable of being combined with R 1 , R 2 and R 3 includes halogen, a cyano group, a hydroxyl group or a carboxyl group.
2. The cathode active material for a lithium secondary battery according to claim 1 , wherein the salt containing O − or S − included in R 1 is a salt with an alkaline metal cation, an alkaline earth metal cation, N + R 4 or P + R 4 , and R 4 is hydrogen or a C1-C8 alkyl group.
3. The cathode active material for a lithium secondary battery according to claim 1 , wherein the hydrocarbon group included in R 1 , R 2 and R 3 is substituted or connected by at least one selected from a group consisting of a carbon-carbon double bond, —O—, —S—, —CO—, —OCO—, —SO—, —CO—O—, —O—CO—O—, —S—CO—, —S—CO—O—, —CO—NH—, —NH—CO—O—, —NH′—, >P═O, —S—S— and —SO 2 —, and R′ is hydrogen or a C1-C8 alkyl group.
4. The cathode active material for a lithium secondary battery according to claim 1 , wherein the thioamide compound includes at least one selected from a group consisting of compounds represented by Chemical Formulae 1 to 19:
5. The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium metal oxide particle includes a nickel-based lithium oxide represented by General Formula 1 below:
Li x Ni y M 1-y O 2 [General Formula 1]
wherein, in the General Formula 1 above, 0.95≤x≤1.08, y≥0.5, and M is at least one element selected from a group consisting of Co, Mn, Al, Zr, Ti, B, Mg or Ba.
6. The cathode active material for a lithium secondary battery according to claim 5 , wherein, in the General Formula 1, 0.8≤y≤0.93.
7. The cathode active material for a lithium secondary battery according to claim 5 , wherein, in the General Formula 1, M includes Co and Mn.
8. The cathode active material for a lithium secondary battery according to claim 5 , wherein the lithium metal oxide particle includes a doping or a coating which contains at least one of Al, Zr or Ti.
9. The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium metal oxide particle has a layer structure, and a grain boundary at a surface portion of the lithium metal oxide particle is coated by the thio-based compound.