Nickel-containing composite hydroxide and production process therefor, positive-electrode active material for a nonaqueous-electrolyte secondary battery and production process therefor, and nonaqueous-electrolyte secondary battery
Provided is a nickel-containing composite hydroxide that is a precursor of a positive-electrode active material with which a nonaqueous-electrolyte secondary battery having a low irreversible capacity and a high energy density can be configured. An aqueous alkaline aqueous solution and a complexing agent are added to an mixed aqueous solution including at least nickel and cobalt to regulate the pH (measured at a reference liquid temperature of 25° C.) of this mixed aqueous solution to 11.0 to 13.0, the ammonium concentration to 4 to 15 g/L, and the reaction temperature to 20° C. to 45° C. Using stirring blades having an inclination angle of 20° to 60° with respect to a horizontal plane, the mixture is stirred to conduct a crystallization reaction under such conditions that when the nickel-containing composite hydroxide to be obtained is roasted in air at 800° C. for 2 hours, the roasted composite hydroxide has a BET value of 12 to 50 m 2 /g. Thus a nickel-containing composite hydroxide expressed by Ni 1−x−y Co x Al y M t (OH) 2+α (where, 0<x≤0.20, 0<y≤0.15, 0≤t≤0.10, 0≤α 0.50, and M is one or more kind of element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr and Y), or the general formula: Ni 1−x−z Co x Mn z M t (OH) 2+α (where 0<x≤0.50, 0<z≤0.50, x+z≤0.70, 0≤t≤0.10, 0≤α≤0.50, and M is one or more kind of element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr and Y) is obtained.
1. A positive-electrode active material for a nonaqueous-electrolyte secondary battery, the positive-electrode active material comprising a lithium nickel-containing composite oxide that is expressed by the general formula: Li 1+u Ni 1−x−y Co x Al y M t O 2 , where 0<x≤0.20, 0<y≤0.15, 0≤t≤0.10, 0≤u≤0.50, and M is at least one element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr or Y, or Li 1+u Ni 1−x−z Co x Mn z M t O 2 , where 0<x≤0.50, 0<z≤0.50, x+z≤0.70, 0≤t≤0.10, 0≤u≤0.50, and M is at least one element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr or Y, the lithium nickel-containing composite oxide consisting of secondary particles that are formed by an aggregation of a plurality of primary particles, the primary particles having a layered hexagonal crystal structure; and
the average particle size of the secondary particles is 20 μm to 50 μm or less, the average particle size of the primary particles is 0.10 μm to 0.40 μm, and the site occupancy of metal ions other than lithium ions at site 3 a that is obtained from Rietveld analysis of X-ray diffraction is 1.5% or less; wherein the positive-electrode active material is prepared by a method comprising a step where the lithium nickel-containing composite oxide undergoes a firing process in an oxygen atmosphere at a temperature of 650° C. to 850° C.
2. The positive-electrode active material for a nonaqueous-electrolyte secondary battery according to claim 1 , wherein a shape of the secondary particles is spherical or ellipsoidal.
3. The positive-electrode active material for a nonaqueous-electrolyte secondary battery according to claim 1 , wherein a tap density of the secondary particles is 2.5 g/cm 3 or greater.
4. A production method for a positive-electrode active material for a nonaqueous-electrolyte secondary battery, the positive-electrode active material comprising a lithium nickel-containing composite oxide that has a layered hexagonal crystal structure that is expressed by the general formula: Li 1+u Ni 1−x−y Co x Al y M t O 2 , where 0<x≤0.20, 0<y≤0.15, 0≤t≤0.10, 0≤u≤0.50, and M is at least one element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr or Y, or Li 1+u Ni 1−x−z Co x Mn z M t O 2 , where 0<x≤0.50, 0<z≤0.50, x+z≤0.70, 0≤t≤0.10, 0≤u≤0.50, and M is at least one element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr or Y, the lithium nickel-containing composite oxide consisting of secondary particles that are formed by aggregation of a plurality of primary particles, the primary particles having a layered hexagonal crystal structure; and
the average particle size of the secondary particles is more than 20 μm and 50 μm or less, the average particle size of the primary particles is 0.10 μm to 0.40 μm, and the site occupancy of the metal ions other than lithium ions at site 3 a that is obtained from Rietveld analysis of X-ray diffraction is 1.5% or less;
the method comprising;
a mixing process for forming a lithium mixture by mixing a nickel-containing composite hydroxide or heat treated particles of the nickel-containing composite hydroxide with a lithium compound; wherein the nickel-containing composite hydroxide is expressed by general formula: Ni 1−x−y Co x Al y M t (OH) 2+α, where 0<x≤0.20, 0<y≤0.15, 0≤t≤0.10, 0≤α≤0.50, and M is at least one element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr, or Y, or Ni 1−x−z Co x Mn z M t (OH) 2+α, where 0<x≤0.50, 0<z≤0.50, x+z≤0.70, 0≤t≤0.10, 0 ≤α≤0.50, and M is at least one element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr, or Y; and
a firing process of performing firing of the lithium nickel-containing composite oxide that was formed in the mixing process in an oxygen atmosphere at a temperature of 650° C. to 850° C., whereby the positive-electrode active material of claim 1 is formed.
5. The production method for a positive-electrode active material for a nonaqueous-electrolyte secondary battery according to claim 4 , further comprising a roasting process before the mixing process for obtaining the heat treated particles by roasting the nickel-containing composite hydroxide in an air atmosphere at 400° C. to 900° C.
6. A nonaqueous-electrolyte secondary battery that uses the positive-electrode active material for a nonaqueous-electrolyte secondary battery according to claim 1 as a positive-electrode material.