Preparation method of lithium-metal composite oxides

Disclosed is a method for preparing a lithium-metal composite oxide, the method comprising the steps of: (a) mixing an aqueous solution of one or more transition metal-containing precursor compounds with an alkalifying agent and a lithium precursor compound to precipitate hydroxides of the transition metals; (b) mixing the mixture of step (a) with water under supercritical or subcritical conditions to synthesize a lithium-metal composite oxide, and drying the lithium-metal composite oxide; and (c) subjecting the dried lithium-metal composite oxide either to calcination or to granulation and then calcination. Also disclosed are an electrode comprising the lithium-metal composite oxide, and an electrochemical device comprising the electrode. In the disclosed invention, a lithium-metal composite oxide synthesized based on the prior supercritical hydrothermal synthesis method is subjected either to calcination or to granulation and then calcination. Thus, unlike the prior dry calcination method or wet precipitation method, a uniform solid solution can be formed and the ordering of metals in the composite oxide can be improved. Accordingly, the lithium-metal composite oxide can show crystal stability and excellent electrochemical properties.