Method for manufacturing positive-electrode active material precursor and positive-electrode active material for nonaqueous electrolyte secondary battery
A method for manufacturing a positive-electrode active material precursor for a nonaqueous electrolyte secondary battery containing a nickel-cobalt-manganese carbonate compound includes: an initial aqueous solution preparation process of preparing an initial aqueous solution; a nucleation process of forming nuclei; and a nucleus growth process of growing the nuclei. In the nucleation process, a pH value of the mixed aqueous solution is controlled to be greater than or equal to 8.0 at the reference reaction temperature of 25° C. In the nucleus growth process, the pH value of the mixed aqueous solution is controlled to be greater than or equal to 6.0 and less than or equal to 7.5 at the reference reaction temperature of 25° C. The nucleation process takes a time greater than or equal to 1/20 and less than or equal to 3/10 of a combined time of the nucleation process and the nucleus growth process.
1 . A method for manufacturing a positive-electrode active material precursor for a nonaqueous electrolyte secondary battery containing a nickel-cobalt-manganese carbonate compound represented by a general formula of Ni x Co y Mn z M t CO 3 where x+y+z+t=1, 0.05≤x≤0.3, 0.1≤y≤0.4, 0.55≤z≤0.8, and 0≤t≤0.1 are satisfied; and M represents one or more additive elements selected from among Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W, the method comprising:
an initial aqueous solution preparation process of preparing an initial aqueous solution that contains an ammonium ion supplier and water, in which a pH value is controlled to be greater than or equal to 9.0 and less than or equal to 12.0 by an alkaline aqueous solution at a reference reaction temperature of 25° C., and a liquid temperature is set greater than or equal to 25° C. and less than or equal to 50° C.;
a nucleation process of forming nuclei by adding and mixing, under presence of carbonate ions, an aqueous solution that contains nickel as a metal component, an aqueous solution that contains cobalt as a metal component, an aqueous solution that contains manganese as a metal component, and an ammonium ion supplier, with the initial aqueous solution so as to form a mixed aqueous solution; and
a nucleus growth process of growing the nuclei by adding and mixing, under presence of carbonate ions, an aqueous solution that contains nickel as a metal component, an aqueous solution that contains cobalt as a metal component, an aqueous solution that contains manganese as a metal component, and an ammonium ion supplier, with the mixed aqueous solution formed in the nucleation process,
wherein in the nucleation process, a pH value of the mixed aqueous solution is controlled to be greater than or equal to 8.0 at the reference reaction temperature of 25° C., by adding an alkaline aqueous solution, thereby controlling the pH value of the mixed aqueous solution while concurrently adding the ammonium ion supplier and the alkaline aqueous solution during the nucleation process,
wherein in the nucleus growth process, the pH value of the mixed aqueous solution is controlled to be greater than or equal to 6.0 and less than or equal to 7.5 at the reference reaction temperature of 25° C., by adding the alkaline aqueous solution, and
wherein the nucleation process takes a time greater than or equal to 1/20 and less than or equal to 3/10 of a combined time of the nucleation process and the nucleus growth process, to add the aqueous solution that contains nickel as the metal component, the aqueous solution that contains cobalt as the metal component, the aqueous solution that contains manganese as the metal component, and the ammonium ion supplier, to the initial aqueous solution.
2 . The method for manufacturing the positive-electrode active material precursor for the nonaqueous electrolyte secondary battery as claimed in claim 1 , wherein the ammonium ion supplier is either of an ammonium carbonate aqueous solution, ammonia water, an ammonium chloride aqueous solution, or an ammonium sulfate aqueous solution, and
wherein the alkaline aqueous solution is an aqueous solution of one or more substances selected from among sodium carbonate, sodium bicarbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide.
3 . The method for manufacturing the positive-electrode active material precursor for the nonaqueous electrolyte secondary battery as claimed in claim 1 , wherein after completion of the nucleation process and before starting the nucleus growth process, an acid aqueous solution of either sulfuric acid, nitric acid, or hydrochloric acid is added to the mixed aqueous solution so as to lower the pH value of the mixed aqueous solution.
4 . The method for manufacturing the positive-electrode active material precursor for the nonaqueous electrolyte secondary battery as claimed in claim 1 , wherein during processes ranging from the initial aqueous solution preparation process to the nucleus growth process, an ammonia concentration of the initial aqueous solution and the mixed aqueous solution is controlled to be greater than or equal to 3 g/L and less than or equal to 15 g/L.
5 . The method for manufacturing the positive-electrode active material precursor for the nonaqueous electrolyte secondary battery as claimed in claim 1 , the method further comprising:
a coating process of coating the secondary particles contained in the positive-electrode active material precursor for the nonaqueous electrolyte secondary battery obtained in the nucleus growth process, with the additive element.
6 . A method for manufacturing a positive-electrode active material for a nonaqueous electrolyte secondary battery, the method comprising:
a heat treatment process of applying heat treatment to the positive-electrode active material precursor for the nonaqueous electrolyte secondary battery obtained by the method for manufacturing the positive-electrode active material precursor for the nonaqueous electrolyte secondary battery as claimed in claim 1 , at a temperature greater than or equal to 105° C. and less than or equal to 600° C.;
a mixing process of adding and mixing a lithium compound in particles obtained in the heat treatment process, to form a lithium mixture; and
a sintering process of sintering the lithium mixture in an oxidizing atmosphere at a temperature greater than or equal to 600° C. and less than or equal to 1000° C.