Abstract: A method for reducing waste by recovering transition metal of a lithium secondary battery of the present invention includes preparing a cathode active material from a cathode of the lithium secondary battery, producing a first leachate by treating the cathode active material with a first acidic solution containing a reducing agent in an amount smaller than an amount corresponding to a reaction equivalent of the cathode active material, and producing a second leachate by treating the remaining cathode active material, which excludes a fraction contained in the first leachate, with a second acidic solution containing a reducing agent. Accordingly, extraction rate of manganese and purity of cobalt may be improved.

Abstract: A cathode active material for a lithium secondary battery according to an embodiment of the present invention includes a plurality of a lithium-transition metal composite oxide particle having a shape of a secondary particle in which a plurality of primary particles are aggregated. The lithium-transition metal composite oxide particle includes a lithium-molybdenum-containing portion having a hexagonal close-packed structure formed between the primary particles.