POSITIVE ELECTRODE ACTIVE MATERIAL, POSITIVE ELECTRODE MATERIAL, POSITIVE ELECTRODE, AND NON-AQUEOUS ELECTROLYTE SECONDARY BATTERY

[Object] Provided is a means which is capable, with respect to a non-aqueous electrolyte secondary battery, of suppressing a decrease in capacity when the battery is used for a long period of time, and improving cycle characteristics. [0002] [Solving Means] Disclosed is a positive electrode active substance for a non-aqueous electrolyte secondary battery comprising a composite oxide containing lithium and nickel, in which the positive electrode active substance has a structure of secondary particles formed by aggregation of primary particles, the average particle diameter of the primary particles (D1) is 0.9 µm or less, and the ratio value (D2/D1) of the average particle diameter of the secondary particles (D2) to the average particle diameter of the primary particles (D1) is 11 or more.