Preparation method of composite precursor material

The invention relates to a preparation method of a composite precursor material, which comprises the following steps: (1) mixing soluble cobalt salt, alkali metal hydroxide, a dispersing agent and EDTA (Ethylene Diamine Tetraacetic Acid), cocurrent-flowing into a reaction kettle which is provided with a base solution and is filled with a large amount of air, carrying out constant-temperature co-precipitation, and fully reacting to obtain a hydroxyl cobalt oxide precursor material with the granularity of 3 microns; and (2) on the basis, preparing a mixed solution from manganese chloride, nickel chloride and aluminum chloride according to a molar ratio of Mn: Ni: Al of 80: 15: 5, enabling the mixed solution and a mixed solution of liquid caustic soda, EDTA-2Na and ammonia water to flow in parallel into a reaction kettle of which the base solution is a hydroxyl cobalt oxide precursor material of 3 microns, introducing a large amount of nitrogen, carrying out constant-temperature co-precipitation, carrying out fu