Positive electrode active material precursor for nonaqueous electrolyte secondary battery, positive electrode active material for nonaqueous electrolyte secondary battery, method for manufacturing positive electrode active material precursor for nonaqueous electrolyte secondary battery, and method for manufacturing positive electrode active material for nonaqueous electrolyte secondary battery

1. A positive electrode active material for a nonaqueous electrolyte secondary battery, the positive electrode active material comprising:

a lithium metal composite oxide represented by general formula Li 1+α Ni x Co y Mn z M t O 2 (where 0.25≤α≤0.55, x+y+z+t=1, 0.05≤x≤0.3, 0.1≤y≤0.4, 0.55≤z≤0.8, 0≤t≤0.1, and M denotes at least one additional element selected from a group consisting of Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W);

wherein the lithium metal composite oxide includes a dense secondary particle formed by a plurality of primary particles that have been aggregated;

wherein an internal porosity of the dense secondary particle is less than or equal to 3%, and a ratio of the number of the dense secondary particles, whose internal porosity is less than or equal to 3%, with respect to a total number of particles included in the positive electrode active material is greater than or equal to 65%,

wherein the lithium metal composite oxide is composed of two types layered compounds represented by formulas Li 2 M1O 3 and LiM2O 2 where M1 denotes at least one metal element including Mn and adjusted to be tetravalent on average, and M2 denotes metal elements including at least Ni, Co, and Mn that are adjusted to be trivalent on average,

wherein a tap density of the positive electrode active material is greater than or equal to 1.9 g/cc, and

wherein a specific surface area of the positive electrode active material is greater than or equal to 2.1 m 2 /g and less than or equal to 3.7 m 2 /g.

2. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein

the additional element (M) in the general formula representing the lithium metal composite oxide includes molybdenum (Mo); and

a content ratio of molybdenum (Mo) in metal components consisting of Ni, Co, Mn and the additional element M contained in the lithium metal composite oxide is greater than or equal to 0.5 at % and less than or equal to 5 at %.

3. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein

the additional element (M) in the general formula is molybdenum (Mo); and

0.005≤t≤0.05.

4. A positive-electrode active material manufacturing method for manufacturing the positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , the positive-electrode active material manufacturing method comprising:

a precursor manufacturing method for manufacturing a positive electrode active material precursor including a nickel-cobalt-manganese carbonate composite represented by general formula Ni x Co y Mn Z M 1 CO 3 (where x+y+z+t=1, 0.05≤≤0.3, 0.1≤y≤0.4, 055≤z≤0.8, 0≤t≤0.1, and M denotes at least one additional element selected from a group consisting of Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W) and a hydrogen-containing functional group, the precursor manufacturing method comprising:

a nucleation step of forming nuclei in a mixed aqueous solution that is prepared by mixing together, under the presence of carbonate ions, an initial aqueous solution containing an ammonium ion supplier, an aqueous solution containing nickel as a metal component, an aqueous solution containing cobalt as a metal component, and an aqueous solution containing manganese as a metal component; and

a nucleus growth step of growing the nuclei formed in the nucleation step;

wherein a pH value of the mixed aqueous solution is controlled to be less than or equal to 7.5 at a reaction temperature of 40° C. as a standard temperature in the nucleation step,

wherein the positive-electrode active material manufacturing method further includes:

a heat treatment step of heat-treating the positive electrode active material precursor that has been obtained by the precursor manufacturing method, the heat treatment being performed at a temperature greater than or equal to 80° C. and less than or equal to 600° C.;

a mixing step of adding and mixing a lithium compound into particles obtained by the heat treatment step to form a lithium mixture; and a firing step of firing 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.