A positive electrode comprising a first active material particle, a second active material particle, and a third active material particle, wherein the second active material particle is an aggregated particle formed by aggregation of primary particles, an average particle size D1 of the first active material particle, an average particle size D2 of the second active material particle, and an average particle size D3 of the third active material particle satisfy a relationship of D1 > D2 > D3, the first active material particle has a particle disintegration rate α1 of not more than 20%, the third active material particle has a particle disintegration rate α2 of not more than 20%, and the second active material particle has a particle disintegration rate β of not less than 70%, wherein the particle disintegration rate is measurable by the method mentioned in the description, wherein the first active material particle and the third active material particle are aggregated particles formed by aggregation of primary particles, wherein a proportion ((M1/(M1 + M3)) × 100) of a content M1 of the first active material particle to a total amount of the content M1 of the first active material particle and a content M3 of the third active material particle is not less than 55 vol% and not more than 85 vol%, a proportion ((M3/(M1 + M3)) × 100) of the content M3 of the third active material particle to the total amount of the content M1 of the first active material particle and the content M3 of the third active material particle is not less than 15 vol% and not more than 45 vol%, and a proportion ((M2/M3) × 100) of a content M2 of the second active material particle to the content M3 of the third active material particle is not more than 50 vol%, wherein the first active material particle and the third active material particle each have average composition represented by formula below, and the second active material particle has average composition represented by formula below: Li v1 Ni w1 M1' x1 O z1... (In the formula, 0 < v1 < 2, w1 + x1 ≤ 1, 0.2 ≤ w1 ≤ 1, 0 ≤ x1 ≤ 0.7, 0 < z1 < 3, and M1' is at least one element consisting of transition metals including Co (cobalt), Fe (iron), Mn (manganese), Cu (copper), Zn (zinc), Al (aluminum), Cr (chromium), V (vanadium), Ti (titanium), Mg (magnesium), and Zr (zirconium)), and Li v2 Ni w2 M2' x2 O z2... (In the formula, 0 < v2 < 2, w2 + x2 ≤ 1, 0.65 ≤ w2 ≤1, 0 ≤ x2 ≤ 0.35, 0 < z2 < 3, and M2' is at least one element consisting of transition metals including Co (cobalt), Fe (iron), Mn (manganese), Cu (copper), Zn (zinc), Al (aluminum), Cr (chromium), V (vanadium), Ti (titanium), Mg (magnesium), and Zr (zirconium)), wherein the average particle size D1 of the first active material particle is not less than 12 μm and not more than 25 μm, the average particle size D2 of the second active material particle is not less than 3 μm and not more than 12 μm, and the average particle size D3 of the third active material particle is not less than 1 μm and not more than 6 μm, wherein the average particle size is measurable by the method mentioned in the description. wherein the second active material particle is an aggregated particle formed by aggregation of primary particles, an average particle size D1 of the first active material particle, an average particle size D2 of the second active material particle, and an average particle size D3 of the third active material particle satisfy a relationship of D1 > D2 > D3, the first active material particle has a particle disintegration rate α1 of not more than 20%, the third active material particle has a particle disintegration rate α2 of not more than 20%, and the second active material particle has a particle disintegration rate β of not less than 70%, wherein the particle disintegration rate is measurable by the method mentioned in the description, wherein the first active material particle and the third active material particle are aggregated particles formed by aggregation of primary particles, wherein a proportion ((M1/(M1 + M3)) × 100) of a content M1 of the first active material particle to a total amount of the content M1 of the first active material particle and a content M3 of the third active material particle is not less than 55 vol% and not more than 85 vol%, a proportion ((M3/(M1 + M3)) × 100) of the content M3 of the third active material particle to the total amount of the content M1 of the first active material particle and the content M3 of the third active material particle is not less than 15 vol% and not more than 45 vol%, and a proportion ((M2/M3) × 100) of a content M2 of the second active material particle to the content M3 of the third active material particle is not more than 50 vol%, wherein the first active material particle and the third active material particle each have average composition represented by formula below, and the second active material particle has average composition represented by formula below: the average particle size D1 of the first active material particle is not less than 12 μm and not more than 25 μm, the average particle size D2 of the second active material particle is not less than 3 μm and not more than 12 μm, and the average particle size D3 of the third active material particle is not less than 1 μm and not more than 6 μm, wherein the average particle size is measurable by the method mentioned in the description.