TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Properties: The peak maximum in pore distribution curve of positive electrode active material is at 80-800 nm pore radius. The volume density of positive electrode active material is 1.6-2.4 g/cm3. The median diameter of active material, measured by making particle diameter reference into volume reference after ultrasonic dispersion using output of 30 W and frequency of 22.5 kHz for 5 minutes is 0.1-20 mu m. The refractive index of active material is 1.24, measured by laser diffraction/scattering-type particles size distribution measuring device. The BET specific surface area of active material is 0.5-5 m2/g. The positive electrode active material has volume resistivity of 1000-1 million (~o).cm, which is carried out under pressure of 40 MPa. The carbon concentration of positive electrode active material is 0.01-0.3 weight%. Preferred Composition: The mixing rate of particles (A) and particles (B) is 20:1-1:20. Preferred Process: The lithium-containing transition metal compound fine particles (A) are obtained by pulverizing lithium compound and transition metal compound(s) in liquid medium to obtain slurry, spray-drying the obtained slurry, baking the obtained spray-dried fine particles, and classifying the obtained baked component. A boron-containing compound and tungsten-containing compound are added in the ratio of 0.01-2 mol% with respect to total molar amount of transition metal element in main component raw material during slurry preparation process. The lithium-containing transition metal compound fine particles (B) are obtained by pulverizing lithium compound, transition metal compound(s) and additive which suppresses the grain growth at the time of baking and sintering, in liquid medium to obtain slurry, spray-drying the obtained slurry, baking the obtained spray-dried fine particles, and classifying the obtained baked component. Preferred Condition: The refractive index of slurry during slurry preparation process is adjusted to 1.24. The slurry is spray-dried when slurry has viscosity of 50-4000 cp and ratio of gas feed rate and slurry feed rate of 500-10000. The baking process of slurry is carried out at more than 700 degrees C, preferably more than 900 degrees C under oxygen-containing atmosphere. Preferred Component: The additive contains oxide of molybdenum, tungsten, niobium, tantalum and/or rhenium. The lithium-containing transition metal compound fine particles (A) and lithium-containing transition metal compound fine particles (B) contain lithium-nickel-manganese-cobalt-type complex oxide having crystal structure which belongs to layer structure. The composition of lithium-nickel-manganese-cobalt-type complex oxide is of formula: LiMO2. The molar ratio of manganese and nickel is 0.1-5, and cobalt and mixture of manganese, nickel and cobalt is 0-0.35, and nickel of complex oxide is 0.001-0.2. The lithium-containing transition metal compound fine particles (B) contain molybdenum, tungsten, niobium, tantalum and/or rhenium. A positive electrode has positive electrode active material layer having positive electrode active material on a collector, and binder.M=lithium, nickel and manganese, or lithium, nickel, manganese and cobalt, preferably M is of formula: Liz/(2+z)((Ni(1+y)/2Mn(1-y)/2)1-xCox)2/(2+z) and Liz'/(2+z')((Ni(1+y')/2Mn(1-y')/2)1-x'Cox')2/(2+z');x=0.1-0.35;y,y'=-0.1 to 0.1;z=(1-x) to ((0.02-0.98y)(1-x)(0.2-0.88y));x'=0-0.1;andz'=(1-x') to ((0.05-0.98y')(1-x')(0.2-0.88y')).