Surface-treated active materials and surface treatment method thereof

A surface treatment method of an active material, the surface treatment method comprising:

• a) preparing a precursor solution comprising a first precursor used to generate a first metal oxide containing lithium, wherein the first metal oxide is represented by the following Chemical Formula 1:
• LixMyOz [Chemical Formula 1]
• wherein M comprises at least two selected from the group consisting of P, V, S, and W, and x, y and z are 1 to 8;
• and
• a second precursor used to generate a second metal oxide, wherein the second metal oxide comprises at least one selected from the group consisting of P, S, W and V, and wherein the second precursor comprises at least one selected from the group consisting of an ammonium salt, an aniline salt, a pyridinium salt, a methylammonium salt and an ammonium carbonate salt that are used to generate an anion;
• and
• b) coating the active material with a precursor solution comprising the first precursor and the second precursor by mixing the active material with the precursor solution to generate a coating layer on said active material, wherein said coating layer comprises a mixture of said first metal oxide containing lithium and said second metal oxide;
• and
• heat-treating the active material comprising said coating layer at a temperature of 300° C. to 1000° C. for 30 minutes to 5 hours,
• wherein the anion comprises at least one of (XO4)n− wherein X is P, S, W or V, and n is 1 to 4.