Method of manufacturing lithium nickel composite oxide, lithium nickel composite oxide obtained using the same manufacturing method, and positive electrode active material obtained from the same composite oxide

A method of manufacturing a lithium nickel composite oxide, the method comprising:

• the following steps 1 to 7,
• wherein lithium carbonate is used as a lithium source, and
• the lithium nickel composite oxide is represented by the following Formula (1):
• LixNi1-y-zCoyMzO1.7-2.2 (1)
• (in Formula (1), 0.90<x<1.10, 0.01<y<0.15, 0.005<z<0.10, and M represents one or more metals selected from the group consisting of Al, Mn, W, Nb, Mg, Zr, and Zn),
• the steps 1 to 7 including:
• (Step 1) a dissolving step of dissolving nickel sulfate and cobalt sulfate in water to prepare a nickel sulfate aqueous solution and a cobalt sulfate aqueous solution;
• (Step 2) a precipitation step of mixing the nickel sulfate aqueous solution and the cobalt sulfate aqueous solution, which are obtained in Step 1, with each other and adding an alkali aqueous solution to prepare a coprecipitate of nickel hydroxide and cobalt hydroxide;
• (Step 3) a filtering step of obtaining a precursor cake containing nickel hydroxide and cobalt hydroxide from the coprecipitate which is obtained in Step 2;
• (Step 4) a drying step of drying the precursor cake, which is obtained in Step 3, to obtain precursor powder;
• (Step 5) a mixing step of mixing aluminum hydroxide and lithium carbonate with the precursor powder, which is obtained in Step 4, to obtain a mixture;
• (Step 6) a high-temperature firing step of firing the mixture, which is obtained in Step 5, at a high temperature of higher than 790° C. to obtain a fired product;
• and
• (Step 7) a low-temperature firing step of firing the fired product, which has undergone Step 6, at a low temperature of lower than 790° C.