Positive electrode material of secondary battery, and secondary battery using same
Provided is a positive electrode material which can impart a 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 secondary battery disclosed here includes a positive electrode active substance particle and a coating containing a titanium-containing compound at the surface of the positive electrode active substance particle. A layer having a higher Ti concentration than the Ti concentration at a depth of 500 nm from the surface is formed in a surface portion of the positive electrode active substance particle. The titanium-containing compound in the coating is at least one compound selected from the group consisting of TiO 2 , Ti n O 2n−1 , wherein n is an integer of 3 or more, and oxides containing Li and Ti.
1. A positive electrode material of a secondary battery, the positive electrode material comprising:
a positive electrode active substance particle having an outermost region layer that includes an outermost surface of the positive electrode active substance particle, the outermost region layer having a thickness of at least 0.5 nm to at most 100 nm as measured from the outermost surface, wherein the outermost region layer comprises a titanium (Ti) concentrated layer having a higher Ti concentration than a Ti concentration at a depth of 500 nm from the outermost surface of the positive electrode active substance particle; and
a coating containing a titanium-containing compound separate from and on the Ti concentrated layer of the outermost region layer of the positive electrode active substance particle, wherein
a total amount of Ti contained in the titanium-containing compound of the coating and Ti contained in the outermost region layer having the higher Ti concentration is at least 0.01 mass % and at most 15 mass % relative to a mass of the positive electrode active substance particle,
Ti is in solid solution in the positive electrode active substance particle,
the coating is in a form of islands scattered over the outermost surface of the positive electrode active substance particle and does not fully cover the outermost surface, and
the titanium-containing compound in the coating is at least one compound selected from the group consisting of TiO 2 , Ti n O 2n−1 , wherein n is an integer of 3 or more, and oxides containing Li and Ti.
2. A secondary battery comprising:
a positive electrode;
a negative electrode; and
an electrolyte, wherein
the positive electrode contains the positive electrode material of a secondary battery according to claim 1 .
3. The positive electrode material of a secondary battery according to claim 1 , wherein the coating has a thickness of at least 0.1 nm and at most 100 nm.
4. The positive electrode material of a secondary battery according to claim 1 , wherein the coating is formed by causing a constituent material of the coating to adhere to the outermost surface of the positive electrode active substance particle by a mechanochemical treatment or a barrel sputtering treatment.