Abstract: A positive electrode includes: a positive electrode current collector; and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer contains a lithium-containing transition metal oxide represented by composition formula (1) indicated below, and a compound represented by LiVOPO4. The lithium-containing transition metal oxide and the compound represented by LiVOPO4 are dispersed in the positive electrode active material layer. LitNixCoyAlzO2??(1) where 0.9?t?1.1, 0.3<x<0.99, 0.01<y<0.4, 0.001<z<0.2, and x+y+z=1.

Abstract: A positive electrode includes: a positive electrode current collector; and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer contains a lithium-containing transition metal oxide represented by composition formula (1) indicated below, and a compound represented by LiVOPO4. The lithium-containing transition metal oxide and the compound represented by LiVOPO4 are dispersed in the positive electrode active material layer. LitNixCoyAlzO2 ??(1) where 0.9<t<1.1, 0.3<x<0.99, 0.01<y<0.4, 0.001<z<0.2, and x+y+z=1.

Abstract: A positive electrode active material for a lithium ion secondary battery includes: a first active material selected from active materials represented by composition formula (1); and a second active material represented by composition formula (2). A ratio a/b of an average particle diameter a of the first active material to an average particle diameter b of the second active material is in a range of 1?a/b?60. LiwNix(M1)y(M2)zO2 ??(1) where M1 is at least one element selected from Co and Mn, M2 is at least one element selected from Al, Fe, Cr, Ba, Mn, and Mg, 0.9<w<1.1, 2.0<(x+y+z+w)?2.1, 0.3<x<0.95, 0.01<y<0.4, and 0.001<z<0.2. LiaVOPO4 ??(2) where 0<??1.2.