NOVELTY - A positive electrode active material comprises lithium metal complex oxide particle consisting of secondary particles formed by aggregation of primary particles. The secondary particle has spongy structure and interior porosity of 15-70%.    USE - A positive electrode active material for non-aqueous electrolyte secondary batteries (claimed). Can also be used as object for power supplies, hybrid vehicles, electric vehicle, fixed-type storage batteries, and portable electronic device.    ADVANTAGE - The positive electrode active material has high thermal stability and charge/discharge capacitance and satisfies requirement of high capacity and longevity with respect to small secondary batteries. The battery using the positive electrode active material has high safety and battery capacity.    DETAILED DESCRIPTION - A positive electrode active material comprises lithium metal complex oxide particle of formula Li1+zNi1-x-yCoxNbyO2 consisting of secondary particles formed by aggregation of primary particles. The secondary particle has spongy structure and interior porosity of 15-70%.    x=0.05-0.35;    y=0.02-0.08; and    z=- 0.05-0.1.    INDEPENDENT CLAIMS are included for:    (1) manufacture of positive electrode active material which involves preparing mixed aqueous solution containing nickel salt and cobalt salt in atmosphere with oxygen concentration of greater than or equal to 3 vol.%, adding alkaline solution to adjust pH to 10-11 at 25 degrees C, maintaining ammonia concentration of reaction liquid to less than or equal to 3 g/L at 50-80 degrees C, co-precipitating nickel cobalt niobium composite hydroxide particle, mixing nickel cobalt niobium composite hydroxide particle and lithium compound to obtain lithium mixture, and calcining lithium mixture at 650-850 degrees C in an oxidative atmosphere; and    (2) non-aqueous electrolyte secondary battery comprising positive electrode using the positive electrode active material for non-aqueous electrolyte secondary batteries.