Positive electrode active material, positive electrode, and nonaqueous electrolyte secondary battery

A positive electrode active material that is used for a nonaqueous electrolyte secondary battery, the positive electrode active material, comprising:

• a first positive electrode active material particle;
• and
• a second positive electrode active material particle, wherein
• an average particle diameter d1 (μm) of the first positive electrode active material particle is equal to or more than 3 μm and not more than 5 μm,
• an average particle diameter d2 (μm) of the second positive electrode active material particle is equal to or more than 0.1 μm and not more than 0.5 μm,
• a weight ratio A (wt %) of the second positive electrode active material particle is equal to or more than 2 wt % and not more than 35 wt % when a sum of the first positive electrode active material particle and the second positive electrode active material particle is treated as 100 wt %, and
• the average particle diameter d2 of the second positive electrode active material particle and the weight ratio A of the second positive electrode active material particle satisfy a relationship described below:
• A
• ≦
• -
• 25
• ⁢
• d
• 2
• +
• 37.5
• .