Secondary battery, portable information terminal, vehicle, and manufacturing method of positive electrode active material

A method for manufacturing a positive electrode active material, comprising:

• a first step of mixing a titanium compound, a lithium compound, and a cobalt-containing material to form a first mixture;
• and
• a second step of heating the first mixture,
• wherein the cobalt-containing material contains magnesium and oxygen, and
• wherein a heating temperature in the second step is higher than or equal to 780° C. and lower than or equal to 1150° C.

A method for manufacturing a positive electrode active material, comprising:

• a first step of mixing lithium cobalt oxide, a magnesium compound, and a fluoride to form a first mixture;
• a second step of heating the first mixture to form a cobalt-containing material;
• a third step of mixing the cobalt-containing material, a titanium compound, and a lithium compound to form a second mixture;
• and
• a fourth step of heating the second mixture,
• wherein a heating temperature in the fourth step is higher than or equal to 780° C. and lower than or equal to 1150° C.

A method for manufacturing a positive electrode active material, comprising:

• a first step of mixing a composite oxide, a magnesium compound, and a fluoride to form a first mixture;
• a second step of heating the first mixture to form a cobalt-containing material;
• a third step of mixing the cobalt-containing material, a titanium compound, and a lithium compound to form a second mixture;
• and
• a fourth step of heating the second mixture,
• wherein the composite oxide has a layered rock-salt crystal structure,
• wherein the composite oxide contains cobalt,
• wherein the composite oxide contains one or more selected from nickel, manganese, and aluminum, and
• wherein a heating temperature in the fourth step is higher than or equal to 780° C. and lower than or equal to 1150° C.