Method of preparing positive electrode active material for lithium secondary battery and positive electrode active material for lithium secondary battery prepared thereby

Preparation of a Positive Electrode Active Material

[0044]In order to prepare an NCA positive electrode active material, a precursor represented by NiCoAl(OH)2 was produced in advance by a coprecipitation reaction.

[0045]A positive electrode active material for a lithium secondary battery was prepared by adding LiOH as a lithium compound and 1.4 mole of Al2O3 and 0.125 mole of Mg(OH)2 as compounds including a dopant M3 to the produced precursor, and heat-treating a mixture of the lithium compound, the compounds including the dopant M3 and the precursor.

[0046]After preparing distilled water and constantly maintaining temperature of the distilled water, the prepared positive electrode active material for the lithium secondary battery was injected into the distilled water to wash the positive electrode active material for the lithium secondary battery with the distilled water while maintaining temperature of the distilled water.

[0047]After mixing the washed positive electrode active materia

[0048]Positive electrode active materials of Examples 2 to 4 were prepared in the same manner as in Example 1 except that CeO2 as the M4-containing compound for coating was added at a mixing ratio as shown in the following Table 1.

TABLE 1M3, mol %M4, mol %ClassificationAlMgCeTiCeTiExample-11.40.1250.05Example-21.40.1250.1Example-31.40.1250.25Example-41.40.1250.5Example-51.40.1250.05Example-61.40.1250.050.05Example-71.40.1250.050.05Comparative1.40.125Example-1Comparative1.40.1250.1Example-2

[0049]A precursor represented by NiCoAl(OH)2 was produced by the coprecipitation reaction.

[0050]A positive electrode active material for a lithium secondary battery was prepared by adding LiOH as the lithium compound and 1.4 mole of Al2O3, 0.125 mole of Mg(OH)2 and 0.05 mole of CeO2 as the compounds including the dopant M3 to the produced precursor, and heat-treating a mixture of the lithium compound, the compounds including the dopant M3 and the precursor.

[0051]After preparing distilled water and constantly maintaining temperature of the distilled water, the prepared positive electrode active material for the lithium secondary battery was injected into the distilled water to wash the positive electrode active material for the lithium secondary battery with the distilled water while maintaining temperature of the distilled water.

[0052]Thereafter, a positive electrode active material of Example 5 was prepared by heat-treating the washed positive electrode active material at a second tem