Metal composite hydroxide and method for producing the same, positive electrode active material for lithium ion secondary battery and method for producing the same, and lithium ion secondary battery using the same

A positive electrode active material for lithium ion secondary battery comprising:

• a lithium-metal composite oxide that contains lithium, nickel, manganese, and tungsten and optionally cobalt and element M and has a mass ratio of the respective metal elements represented by Li:Ni:Mn:Co:W:M=1+u:x:y:z:a:b (x+y+z=1, −0.05≤u≤0.50, 0.3≤x≤0.95, 0.05≤y≤0.55, 0≤z≤0.4, 0<a≤0.1, 0≤b≤0.1, and M is one or more elements selected from the group consisting of Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, and Ta), wherein
• the lithium-metal composite oxide includes secondary particles with a plurality of aggregated primary particles,
• the secondary particles have a multilayer structure including at least a center at which the primary particles are densely disposed, a void at which the primary particles are more sparsely disposed than the center, and a dense solid portion at which the primary particles are densely disposed, from a center of the secondary particles toward a surface
• a compound containing tungsten and lithium is present in a concentrated state on a surface layer of primary particles present on a surface of or inside the secondary particles and at a grain boundary between the primary particles,
• a tap density is 1 g/cm3 or more and 2 g/cm3 or less, and
• a BET specific surface area is 1.45 m2/g or more and 5.4 m2/g or less.