A positive electrode includes first active material particles, second active material particles, and third active material particles, and the second active material particles include an aggregation of second primary particles. The average particle size D1 of the first active material particles, the average particle size D2 of the second active material particles, and the average particle size D3 of the third active material particles satisfy a relationship of D1>D2>D3. A first particle disintegration rate α1 of the first active material particle and a third particle disintegration rate α2 of the third active material particle are not more than 20%, and a second particle disintegration rate β of the second active material particle is not less than 70%.