Lithium metal composite oxide powder, positive electrode active material for lithium secondary batteries, positive electrode, and lithium secondary battery
A lithium metal composite oxide powder has a layered structure, and includes at least Li, Ni, an element X, and an element M. The element X is at least one element selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga and V. The element M is at least one element selected from the group consisting of B, Si, S and P. A molar ratio of Ni to a sum of Ni and the element X, Ni/(Ni+X), is 0.40 or more. A molar ratio of the element M to a sum of Ni and the element X, M/(Ni+X), is more than 0 and 0.05 or less. The lithium metal composite oxide powder has core particles and coatings. The coatings include the element M at a concentration of more than 0.0185 mol/cm 3 and 0.070 mol/cm 3 or less.
1 . A lithium metal composite oxide powder, which has a layered structure, and comprises at least Li, Ni, an element X, and an element M, wherein:
the element X is at least one element selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga and V, and the element M is at least one element selected from the group consisting of B, Si, S and P;
a molar ratio of Ni to a sum of Ni and the element X, Ni/(Ni+X), is 0.40 or more;
a molar ratio of the element M to a sum of Ni and the element X, M/(Ni+X), is more than 0 and 0.05 or less; and
the lithium metal composite oxide powder has core particles and coatings formed thereon, the coatings comprising the element M at a concentration of more than 0.0185 mol/cm 3 and 0.070 mol/cm 3 or less.
2 . The lithium metal composite oxide powder according to claim 1 , which has a BET specific surface area of 2 m 2 /g or less.
3 . The lithium metal composite oxide powder according to claim 1 wherein the coatings comprise a boron-containing compound.
4 . The lithium metal composite oxide powder according to claim 1 , which satisfies composition formula (I) below:
Li[Li m (Ni (1-n-p) X n M p ) 1-m ]O 2 (I)
wherein −0.1≤m≤0.2, 0<n≤0.6, 0<p≤0.05, and n+p<0.6.
5 . The lithium metal composite oxide powder according to claim 4 , wherein m in the composition formula (I) satisfies: 0<m≤0.2.
6 . The lithium metal composite oxide powder according to claim 1 , which has an average primary particle diameter of 1 μm or more and 7 μm or less.
7 . The lithium metal composite oxide powder according to claim 1 , wherein the coatings have an amorphous structure.
8 . A positive electrode active material for a lithium secondary battery, comprising the lithium metal composite oxide powder of claim 1 .
9 . A positive electrode comprising the positive electrode active material of claim 8 .
10 . A lithium secondary battery comprising the positive electrode of claim 9 .