POSITIVE ELECTRODE ACTIVE MATERIAL CONTAINING SOLID SOLUTION ACTIVE MATERIAL, POSITIVE ELECTRODE CONTAINING THE POSITIVE ELECTRODE ACTIVE MATERIAL, AND NON-AQUEOUS ELECTROLYTE SECONDARY BATTERY USING THE POSITIVE ELECTRODE

1 . A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising:

coating a surface of a solid solution active material represented by the composition formula (1):

Li 1.5 [Ni 0.40 Mn 0.60 Co 0.40 [Li] 0.1 ]O z   (1)

wherein X represents at least one selected from Ti, Zr and Nb, 0≤e≤0.5, a+b++c+d+e=1.5, 0.1≤d≤0.4, and 1.1≤[a+b+c+e]≤1.4, and z represents the number of oxygen atoms satisfying an atomic valence, with alumina; and

preparing the solid solution active material, wherein the preparing comprises:

a first step of mixing an organic acid salt of a transition metal having a melting point of 100° C. to 350° C.;

a second step of melting the mixture obtained in the first step at 100° C. to 350° C.;

a third step of subjecting the molten substance obtained in the second step to pyrolysis at a temperature equal to higher than the melting point; and

a fourth step of calcining the pyrolysate obtained in the third step.

2 . The method according to claim 1 , wherein a citrate of at least one of Ti, Zr and Nb is further mixed in the first step.

3 . The method according to claim 1 , wherein an organic acid salt of an alkali metal is further mixed in the first step.

4 . The method according to claim 1 , wherein the coating the surface of the solid solution active material with alumina comprises:

a fifth step of mixing the solid solution active material and an aluminum nitrate solution at pH of 7 to 8;

a sixth step of drying the solid solution active material precursor obtained in the fifth step; and

a seventh step of calcining the dry solid solution active material precursor obtained in the sixth step at a temperature of 450° C.±50° C.