Precursor with transformed crystal form and preparation method thereof

A preparation method of cobaltosic oxide, comprising the following steps:

• (1) heating a 0.8 mol/L to 1.8 mol/L carbonate solution, spray adding a cobalt salt and reacting, and spray adding a 2.5 mol/L to 3.5 mol/L carbonate solution and reacting to obtain a cobalt carbonate slurry with a particle size of 3 μm to 5 μm;
• (2) allowing the cobalt carbonate slurry to stand, and spray adding a cobalt salt and a 2.5 mol/L to 3.5 mol/L carbonate solution separately to allow a reaction to obtain a cobalt carbonate slurry with a particle size of 9 μm to 13 μm;
• and spray adding a cobalt salt using a single spray head at a flow rate of 1 m3/h to 3 m3/h and spray adding a 2.5 mol/L to 3.5 mol/L carbonate solution using no less than three spray heads each at a flow rate of 0.2 m3/h to 5 m3/h to obtain cobalt carbonate with a transformed crystal form;
• and
• (3) further spray adding a cobalt salt and a 2.5 mol/L to 3.5 mol/L carbonate solution to the cobalt carbonate with a transformed crystal form, performing a constant-temperature reaction under heating, and washing and calcining a resulting product to obtain the cobaltosic oxide,
• wherein in steps (1) and (2), the cobalt salt is spray added at a flow rate of 1 m3/h to 3 m3/h, and the 2.5 mol/L to 3.5 mol/L carbonate solution is spray added at a flow rate of 0.2 m3/h to 5 m3/h.