Ni-, Co-, and Mn- multi-element doped positive electrode material for lithium battery and its preparation method

A method for preparing a multi-element cathode material comprising the following steps:

• a) preparing a Ni, Co and Mn multi-element intermediate wherein step (a) comprises the steps of:
• dissolving one or more sulfate or nitrate of Ni, Co and Mn in water to form a first solution;
• adding a salt of Mo, Cr, Ge, In, Sr, Ta, Mg or a salt of one or more of rare earth elements to the first solution to make a second solution, wherein the second solution has a molar concentration of all metal elements in the range of 0.8-1.3 mol/L, in which a molar ratio of Ni, Co and Mn is Ni:Co:Mn=(0.9-1.2):1:(0.9-1.2), and a total amount of Mo, Cr, Ge, In, Sr, Ta, Mg and/or rare earth elements is 0.13-0.3% of the total weight of Ni, Co and Mn;
• adding the second solution into a basic solution of NaOH and NH3 that contains polyethylene glycol or an oxalate solution that contains polyethylene glycol at a rate of 5-30 mL/min in a temperature range of 40-70° C. to obtain a third solution;
• stirring the third solution for 1-2 hours before settling for 1-4 hours and filtering to obtain a solid;
• washing the solid with de-ionized water until a weight percentage of element Na is less than 0.01%;
• drying the solid at 105-120° C. for 3-5 hours to obtain the Ni, Co and Mn multi-element intermediate;
• b) mixing the Ni, Co and Mn multi-element intermediate with a Lithium salt to obtain a first mixture, wherein the molar ratio of the mixture is Li:(Ni+Co+Mn)=1.05-1.1:1, grounding the first mixture for 2-8 hours before preheating at 500-520° C. for 2 hours;
• mixing polyvinyl alcohol (PVA) with the pretreated material to form lumps, where an amount of PVA used is 0.98-2% of the total weight of Ni, Co and Mn;
• c) calcining the lumps obtained above at 800-930° C. for 16-22 hours before cooling to 45-55° C., and crashing the calcining lumps and sieving through a 400 mesh sieve to obtain a filtrate;
• d) placing the filtrate in a porcelain dish and calcining at 700-800° C. for 5-8 hours before cooling to 45-55° C., and crashing the calcined filtrate through a 400 mesh sieve to obtain the multi-element cathode material.