Positive electrode material of lithium secondary battery, and lithium secondary battery using same
Provided is a positive electrode material which can impart a lithium secondary battery with excellent low temperature output characteristics, excellent high temperature cycle characteristics and excellent durability against high voltage. A positive electrode material of a lithium secondary battery disclosed here includes a positive electrode active substance particle, a Li-free first coating at the surface of the positive electrode active substance particle, and a Li-containing second coating at the surface of the positive electrode active substance particle. The first coating contains a titanium oxide represented by TiO 2 or Ti n O 2n-1 , wherein n is an integer of 3 or more. The second coating contains a composite oxide containing Li and Ti, wherein the ratio of the number of atoms of Li relative to the number of atoms of Ti is at least 0.1 and at most 3.
1. A positive electrode material of a lithium secondary battery, the positive electrode material comprising:
a positive electrode active substance particle;
a Li-free first coating at a surface of the positive electrode active substance particle; and
a Li-containing second coating at the surface of the positive electrode active substance particle, wherein
the first coating contains a titanium oxide represented by TiO 2 or Ti n O 2n-1 , wherein n is an integer of 3 or more,
the second coating contains a composite oxide containing Li and Ti, wherein a ratio of a number of atoms of Li relative to a number of atoms of Ti is at least 0.1 and at most 3, and
all of the second coating is in contact with the surface of the positive electrode active substance particle, and at least some of the first coating is present on the second coating such that where the first coating is present on the second coating, the first coating contacts the second coating and does not contact the surface of the positive electrode active substance particle.
2. The positive electrode material of a lithium secondary battery according to claim 1 , wherein in the composite oxide contained in the second coating, the ratio of the number of atoms of Li relative to the number of atoms of Ti is at least 0.9 and at most 2.5.
3. The positive electrode material of a lithium secondary battery according to claim 1 , wherein a total amount of Ti contained in the first coating and the second coating is at least 0.01 mass % and at most 10 mass % relative to a mass of the positive electrode active substance particle.
4. The positive electrode material of a lithium secondary battery according to claim 1 , wherein a ratio of an area of the first coating relative to an area of the second coating on the positive electrode active substance particle is at least 0.01 and at most 3.
5. A lithium secondary battery comprising:
a positive electrode;
a negative electrode; and
an electrolyte, wherein
the positive electrode contains the positive electrode material of a lithium secondary battery according to claim 1 .
6. The positive electrode material of a lithium secondary battery according to claim 1 , wherein all of the first coating is present on the second coating.