Positive-electrode active material powder
The present invention provides a positive-electrode active material powder, which comprises a granular material (A) capable of doping/dedoping lithium ions and a deposit (B) placed on the surface of the material in a granular or layered form (herein, the material (A) and the deposit (B) are not the same), the percentage of [volumetric sum of particles having a particle diameter of 1 μm or less]/[volumetric sum of entire particles] being 5% or less.
1. A positive-electrode active material powder, which comprises a granular material (A) capable of doping/dedoping lithium ions and a deposit (B) placed on the surface of the material in a granular or layered form (herein, the material (A) and the deposit (B) are not the same), the percentage of [volumetric sum of particles having a particle diameter of 1 μm or less]/[volumetric sum of entire particles] being 5% or less,
wherein the positive-electrode active material powder has an average particle diameter of from 2 μm to 20 μm, inclusive, on a volume basis,
wherein the granular material (A) is the oxidized mixture of Li, Ni, and M, in which M is at least one element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Mg, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Fe, Ru, Co, Rh, Ir, Ni, Pd, Cu, Ag, Zn, and Cd, and
wherein the deposit (B) is a compound containing at least one element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Mg, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Fe, Ru, Co, Rh, Ir, Pd, Cu, Ag, Zn, and Cd.
2. The positive-electrode active material powder according to claim 1 , wherein the BET specific surface area of the positive-electrode active material powder is from 0.1 to 1.0 m 2 /g.
3. The positive-electrode active material powder according to claim 1 , wherein the granular material (A) capable of doping/dedoping lithium ions is a granular compound (A) represented by the formula of Li x Ni 1-y M y O 2 (wherein x is a value within a range from 0.9 or more and 1.2 or less; y is a value within a range from 0 or more and 0.9 or less; and M is at least one element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Mg, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Fe, Ru, Co, Rh, Ir, Ni, Pd, Cu, Ag, Zn and Cd).
4. The positive-electrode active material powder according to claim 3 , wherein M in the compound (A) is at least one element selected from the group consisting of Al, Mn, Fe, Ti, Cu, V and Co.
5. The positive-electrode active material powder according to claim 1 , wherein the compound (B) is a compound containing at least one element selected from the group consisting of Al, Mn and Co.
6. A method for producing a positive-electrode active material powder, which comprises the steps of (a) to (d) in this order:
(a) mixing a lithium compound, a nickel compound and a compound of an element M (wherein M is at least one element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Mg, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Fe, Ru, Co, Rh, Ir, Ni, Pd, Cu, Ag, Zn and Cd) to obtain a mixture,
grinding the mixture and then
calcining the ground mixture at 700° C. or higher and 1,200° C. or lower to obtain a compound (A);
(b) grinding the compound (A) to obtain a granular compound (A);
(c) placing a compound (B) on the particle surface of the granular compound (A) in a granular or layered form to obtain a granular positive electrode active material; and
(d) removing 5 to 40% by weight of particles out of the granular positive electrode active material, accumulated from the finer particle side,
wherein the deposit (B) is a compound containing at least one element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Mg, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Fe, Ru, Co, Rh, Ir, Pd, Cu, Ag, Zn, and Cd,
wherein the percentage of [volumetric sum of particles having a particle diameter of 1 μm or less]/[volumetric sum of entire particles] being 5% or less, and
wherein the positive-electrode active material powder has an average particle diameter of from 2 μm to 20 μm, inclusive, on a volume basis.
7. A positive electrode for nonaqueous secondary battery, which comprises the positive-electrode active material powder according to claim 1 .
8. A nonaqueous secondary battery, which comprises the positive electrode for nonaqueous secondary battery according to claim 7 .
9. The method according to claim 6 , wherein the step (d) is the step of removing 10 to 30% by weight of particles out of the granular positive electrode active material, accumulated from the finer particle side.
10. A method for producing a positive-electrode active material powder described in claim 1 , which comprises the steps of (a) to (d) in this order:
(a) mixing a lithium compound, a nickel compound and a compound of an element M (wherein M is at least one element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Mg, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Fe, Ru, Co, Rh, Ir, Ni, Pd, Cu, Ag, Zn and Cd) to obtain a mixture,
grinding the mixture and then
calcining the ground mixture at 700° C. or higher and 1,200° C. or lower to obtain a compound (A);
(b) grinding the compound (A) to obtain the granular material (A);
(c) placing the deposit (B) on the particle surface of the granular material (A) in a granular or layered form to obtain a granular positive electrode active material; and
(d) removing 5 to 40% by weight of particles out of the granular positive electrode active material, accumulated from the finer particle side.