Positive electrode active material, nonaqueous electrolyte battery, and battery pack

A nonaqueous electrolyte battery comprising:

• a positive electrode comprising a positive electrode active material;
• a negative electrode;
• and
• a nonaqueous electrolyte,
• wherein the positive electrode active material comprises positive electrode active material primary particles which have an olivine structure, are represented by LiMn1−x−yFexMyPO4 where 0≤x≤0.5, 0≤y≤0.2 where M is at least one element selected from the group consisting of Mg, Ni, Co, Sn, and Nb, and satisfy Formula (1) below:
• β<α (1)
• wherein the positive electrode active material primary particles comprise a surface portion, α is a ratio of Fe in LiMn1−α−yFeαMyPO4 which is a composition of the surface portion of the positive electrode active material primary particles, and β is a ratio of Fe in LiMn1−β−yFeβMyPO4 which is a composition of a central portion of the positive electrode active material primary particles,
• wherein the composition of the surface portion of the positive electrode active material primary particles is a composition of a portion having a thickness of 1 to 10 nm from a surface of a cross section of the positive electrode active material primary particle, and the composition of the central portion of the positive electrode active material primary particles is a composition of a peripheral portion within a range of 1 to 10 nm from a center of gravity of the cross section of the same positive electrode active material primary particle,
• wherein an average diameter of the positive electrode active material primary particles is from 0.01 to 1 μm,
• and wherein the negative electrode comprises a negative electrode active material comprising at least one oxide selected from the group consisting of titanium dioxide having a monoclinic system structure and a niobium titanium oxide.