Method of producing positive electrode active material for nonaqueous electrolyte secondary battery
A method of producing a positive electrode active material for a nonaqueous electrolyte secondary battery, the method includes preparing nickel-containing composite oxide particles having a ratio 1 D 90 / 1 D 10 of a 90% particle size 1 D 90 to a 10% particle size 1 D 10 in volume-based cumulative particle size distribution is 3 or less; mixing the composite oxide particles and a lithium compound to obtain a first mixture; subjecting the first mixture to a first heat treatment at a first temperature and a second heat treatment at a second temperature higher than the first temperature to obtain a first heat-treated product; and subjecting the first heat-treated material to a dispersion treatment.
1. A method of producing a positive electrode active material for a nonaqueous electrolyte secondary battery, comprising:
providing nickel-containing composite oxide particles having a ratio 1 D 90 / 1 D 10 of a 90% particle size 1 D 90 to a 10% particle size 1 D 10 in volume-based cumulative particle size distribution of 3 or less;
mixing the composite oxide particles and a lithium compound to obtain a first mixture;
subjecting the first mixture to a first heat treatment at a first temperature and a second heat treatment at a second temperature higher than the first temperature to obtain a first heat-treated material; and
dissociating from the first heat-treated material the positive electrode active material,
wherein the positive electrode active material comprises lithium-transition metal composite oxide particles having a ratio 2 D 50 / 2 D SEM of a 50% particle size 2 D 50 in volume-based cumulative particle size distribution to an average particle size 2 D SEM based on electron microscopic observation in a range of 1 to 4,
wherein the lithium-transition metal composite oxide particles have a ratio 2 D 90 / 2 D 10 of a 90% particle size 2 D 90 to a 10% particle size 2 D 10 in volume-based cumulative particle size distribution is 4 or less,
wherein a molar ratio of nickel in a composition of the lithium-transition metal composite oxide to a total molar number of metals other than lithium is 0.3 to 0.6,
wherein a molar ratio of cobalt in the composition of the lithium-transition metal composite oxide to a total molar number of metals other than lithium is 0.4 or less, and
wherein the first temperature is in a range of 850° C. to 950° C., and the second temperature is in a range of 980° C. to 1,100° C.
2. The method according to claim 1 , wherein the lithium-transition metal composite oxide further contains at least one of Mn or Al and a molar ratio of total molar number of Mn and Al in the composition to a total molar number of metals other than lithium is 0.5 or less.
3. The method according to claim 1 , wherein a molar ratio of lithium in the composition to a total molar number of metals other than lithium is 1.0 to 1.3.
4. The method according to claim 1 , wherein a molar ratio of oxygen in the composition to a total molar number of metals other than lithium is 0.9 to 1.1.
5. The method according to claim 1 , wherein the lithium-transition metal composite oxide particles have a composition represented by the following formula (1):
Li p Ni x Co y M 1 z O 2+α (1)
wherein p, x, y, z, and α satisfy 1.0≤p≤1.3, 0.3≤x<0.6, 0≤y≤0.4, 0≤z≤0.5, x+y+z=1, and −0.1≤α≤0.1, and M 1 represents at least one of Mn and Al.
6. The method according to claim 5 , wherein p in formula (1) satisfies 1.1≤p≤1.2.
7. The method according to claim 1 , wherein the difference between the first temperature and the second temperature is 30° C. to 250° C.
8. The method according to claim 7 , further comprising:
mixing the positive electrode active material dissociated from the first heat-treated material and a lithium compound to obtain a second mixture; and
subjecting the second mixture to a heat treatment to obtain a second heat-treated material.
9. The method according to claim 8 , wherein
the composite oxide particles have a 50% particle size 1 D 50 in volume-based cumulative particle size distribution is in a range of 1 μm to 4 μm, and
the lithium-transition metal composite oxide particles are configured such that the 50% particle size 2 D 50 in volume-based cumulative particle size distribution is in a range of 1 μm to 3 μm.
10. The method according to claim 7 , wherein
the composite oxide particles have a 50% particle size 1 D 50 in volume-based cumulative particle size distribution is in a range of 1 μm to 4 μm, and
the lithium-transition metal composite oxide particles are configured such that the 50% particle size 2 D 50 in volume-based cumulative particle size distribution is in a range of 1 μm to 3 μm.
11. The method according to claim 1 , further comprising:
mixing the positive electrode active material dissociated from the first heat-treated material and a lithium compound to obtain a second mixture; and
subjecting the second mixture to a heat treatment to obtain a second heat-treated material.
12. The method according to claim 11 , wherein
the composite oxide particles have a 50% particle size 1 D 50 in volume-based cumulative particle size distribution is in a range of 1 μm to 4 μm, and
the lithium-transition metal composite oxide particles are configured such that the 50% particle size 2 D 50 in volume-based cumulative particle size distribution is in a range of 1 μm to 3 μm.
13. The method according to claim 1 , wherein
the composite oxide particles have a 50% particle size 1 D 50 in volume-based cumulative particle size distribution is in a range of 1 μm to 4 μm, and
the lithium-transition metal composite oxide particles are configured such that the 50% particle size 2 D 50 in volume-based cumulative particle size distribution is in a range of 1 μm to 3 μm.
14. The method according to claim 1 , wherein the ratio 2 D 50 / 2 D SEM of the 2 D 50 to the 2 D SEM is in a range of 1 to 3.