Positive electrode active material for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery
A positive electrode active material for a non-aqueous electrolyte secondary battery according to a configuration includes a lithium-transition metal composite oxide containing nickel (Ni) in an amount of greater than or equal to 80 mol %, in which boron (B) is present at least on a particle surface of the lithium-transition metal composite oxide. In the lithium-transition metal composite oxide, when particles having a larger particle size than a volume-based 70% particle size (D70) are first particles and particles having a smaller particle size than a volume-based 30% particle size (D30) are second particles, a coverage ratio of B on surfaces of the first particles is larger than a coverage ratio of B on surfaces of the second particles by 5% or greater.
1. A positive electrode active material for a non-aqueous electrolyte secondary battery, comprising:
a lithium-transition metal composite oxide containing nickel (Ni) in an amount of greater than or equal to 80 mol % with respect to a total number of moles of metal elements other than lithium (Li), wherein boron (B) is present at least on a particle surface of the lithium-transition metal composite oxide, wherein
the lithium-transition metal composite oxide is a secondary particle formed by flocculation of a plurality of primary particles;
the secondary particle comprises a plurality of secondary particles wherein those having a larger particle size than a volume-based 70% particle size (D70) are defined as first particles, those having a smaller particle size than a volume-based 30% particle size (D30) are defined as second particles;
a coverage ratio of B on surfaces of the first particles is larger than a coverage ratio of B on surfaces of the second particles by 5% or greater, the coverage ratio being a ratio of an area of surfaces on which B is present to a total area of surfaces of each of the secondary particles.
2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein
the lithium-transition metal composite oxide is a composite oxide represented by a general formula Li a Ni b Co c Mn d Me e B f O g (in the formula, 0.8≤a≤1.2, b≥0.80, c≤0.10, 0.03≤d≤0.12, 0≤e≤0.05, 0.001≤f≤0.020, 1≤g≤2, b+c+d+e+f=1, and Me is at least one element selected from elements of groups 4 to 6).
3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein
B is present on the surfaces of the first particle and the second particle in a form of a boron compound containing Li and B.
4. The positive electrode active material for a non-aqueous electrolyte secondary battery according claim 1 , wherein
the coverage ratio of B on the surfaces of the first particles is 80%˜98%.
5. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein
the coverage ratio of B on the surfaces of the second particles is 50%˜80%.
6. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein
a molar fraction of B with respect to a total number of moles of metal elements other than Li in the first particle is larger than a molar fraction of boron with respect to a total number of moles of metal elements other than Li in the second particle.
7. A non-aqueous electrolyte secondary battery comprising:
a positive electrode having the positive electrode active material according to claim 1 ;
a negative electrode; and
a non-aqueous electrolyte.