Positive electrode active material for nonaqueous secondary battery, and method for manufacturing same
Provided is a positive-electrode active material for a nonaqueous electrolyte secondary battery, including a lithium transition metal composite oxide particle having a layered structure and containing nickel, and an oxide containing lithium and aluminum and an oxide containing lithium and boron adhering to a surface of the lithium transition metal composite oxide particle. The lithium transition metal composite oxide particle includes a secondary particle formed by aggregation of primary particles containing a solid solution of aluminum in a surface layer. The lithium transition metal composite oxide particles have a composition with a difference of more than 0.22 mol % and less than 0.6 mol % between a ratio of the number of moles of aluminum in the solid solution in the surface layer of the primary particles relative to a total number of moles of metal other than lithium and a ratio of the number of moles of aluminum present in a region other than the surface layer of the primary particles relative to the total number of moles of metal other than lithium.
1. A positive-electrode active material for a nonaqueous electrolyte secondary battery comprising:
a lithium transition metal composite oxide particle having a layered structure and containing nickel; and an oxide containing lithium and aluminum and an oxide containing lithium and boron adhering to a surface of the lithium transition metal composite oxide particle, wherein
the lithium transition metal composite oxide particle comprises a secondary particle formed by aggregation of primary particles containing a solid solution of aluminum in a surface layer, and wherein
the positive-electrode active material has a composition with a difference of more than 0.22 mol % and less than 0.6 mol % between a ratio of a number of moles of aluminum in the solid solution in the surface layer of the primary particles relative to a total number of moles of metal other than lithium in the lithium transition metal composite oxide particle and a ratio of a number of moles of aluminum present in a region other than the surface layer of the primary particles relative to the total number of moles of metal other than lithium in the lithium transition metal composite oxide particle,
wherein the oxide containing lithium and boron comprises LiBO 2 and/or Li 3 BO 3 ,
wherein a content ratio (Al/B) of the oxide containing lithium and aluminum to the oxide containing lithium and boron is 1 or less in terms of aluminum and boron.
2. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein
a content of the oxide containing lithium and aluminum relative to the lithium transition metal composite oxide particle is 0.1 mol % to 0.8 mol % in terms of aluminum, and wherein a content of the oxide containing lithium and boron relative to the lithium transition metal composite oxide particle is 0.3 mol % to 2.0 mol % in terms of boron.
3. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein
the lithium transition metal composite oxide particle has a composition in which a ratio of a number of moles of nickel to the total number of moles of metal other than lithium is 0.33 or more and 0.95 or less.
4. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein
the lithium transition metal composite oxide particle has a composition comprising cobalt, and wherein a ratio of a number of moles of cobalt to the total number of moles of metal other than lithium in the composition is 0.02 or more and 0.33 or less.
5. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein
the lithium transition metal composite oxide particle has a composition comprising manganese, and wherein a ratio of a number of moles of manganese to the total number of moles of metal other than lithium in the composition is 0.01 or more and 0.33 or less.
6. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein the lithium transition metal composite oxide has a composition represented by the following formula:
Li a Ni b Co c Mn d Al e M 1 t O 2
wherein 1.0≤a≤1.5, 0.33≤b≤0.95, 0.02≤c≤0.33, 0.01≤d≤0.33, 0.0022≤e≤0.05, 0≤f≤0.02, and b+c+d=1, and M 1 is at least one selected from the group consisting of Zr, Ti, Mg, Ta, Nb, and Mo.
7. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein
the oxide containing lithium and aluminum has a volume-based particle diameter distribution in which a total volume percentage of particles having a particle diameter of 0.4 μm to 3.0 μm is greater than 50%.
8. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 2 , wherein
the lithium transition metal composite oxide has a composition represented by the following formula:
Li a Ni b Co c Mn d Al e M 1 f O 2
wherein 1.0≤a≤1.5, 0.33≤b≤0.95, 0.02≤c≤0.33, 0.01≤d≤0.33, 0.0022≤e≤0.05, 0≤f≤0.02, and b+c+d=1, and M 1 is at least one selected from the group consisting of Zr, Ti, Mg, Ta, Nb, and Mo.
9. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein a volume average particle diameter of the lithium transition metal composite oxide particle is 2μm to 25 μm.
10. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 2 , wherein the content of the oxide containing lithium and aluminum relative to the lithium transition metal composite oxide particle is 0.13 mol % to 0.5 mol % in terms of aluminum.
11. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 2 , wherein a volume average particle diameter of the lithium transition metal composite oxide particle is 2 μm to 25 μm.
12. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 11 , wherein the content of the oxide containing lithium and aluminum relative to the lithium transition metal composite oxide particle is 0.13 mol % to 0.5 mol % in terms of aluminum.
13. The positive-electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 , wherein the content ratio (Al/B) of the oxide containing lithium and aluminum to the oxide containing lithium and boron is 0.1 or more and 1 or less in terms of aluminum and boron.