| CPC H01M 4/131 (2013.01) [C01G 53/82 (2025.01); H01M 4/0402 (2013.01); H01M 4/136 (2013.01); H01M 4/366 (2013.01); H01M 4/58 (2013.01); H01M 10/0525 (2013.01)] | 4 Claims |

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1. A method of preparing a positive electrode active material for rechargeable lithium ion batteries, the method comprising:
primary heat-treating a precursor material and a lithium material to obtain a lithium metal oxide;
dissolving a sulfur material in water to prepare a washing solution;
immersing the lithium metal oxide in the washing solution to wash the lithium metal oxide; and
secondary heat-treating the washed lithium metal oxide,
wherein the positive electrode active material comprises:
a lithium metal oxide active material;
a coating layer on a surface of the lithium metal oxide active material,
wherein the coating layer comprises a sulfur compound,
wherein the rechargeable lithium ion batteries contains a liquid electrolytes,
wherein the sulfur compound is included in the coating layer in an amount ranging from 0.5 wt % to 5.0 wt % with respect to a total weight of the positive electrode active material,
wherein the sulfur compound in the coating layer comprises one or more selected from the group consisting of Li2S, Li2SO4, and Li2SnOx, wherein n is 1≤n≤8, and
wherein the sulfur material is a compound of M2SxOy wherein x ranges from 1 to 8, y ranges from 1 to 8, M is Na or K, and z ranges from 0 to 3.
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