Active material, nonaqueous electrolyte battery, battery pack, and vehicle

An active material comprising active material particles containing orthorhombic Na-containing niobium titanium composite oxide, and satisfying the following formula (1):

• 1.2≤A5/A0 (1)
• where A5 is a mole content ratio of a Li mole content L5 to a total of a Ti mole content T5 and a Nb mole content N5, and each of the Li mole content L5, the Ti mole content T5, and the Nb mole content N5 is a value according to an X-ray photoelectron spectroscopy measurement, obtained at a depth of 5 nm from surfaces of the active material particles, and
• A0 is a mole content ratio of a Li mole content L0 to a total of a Ti mole content T0 and a Nb mole content N0, and each of the Li mole content L0, the Ti mole content T0, and the Nb mole content N0 is a value according to the X-ray photoelectron spectroscopy measurement, obtained at the surfaces of the active material particles,
• wherein
• the orthorhombic Na-containing niobium titanium composite oxide is represented by the general formula Li2+vNa2−wM1xTi6-y-zNbyM2zO14+δ,
• M1 is at least one element selected from the group consisting of Cs, K, Sr, Ba, Mg, and Ca,
• M2 is at least one element selected from the group consisting of Zr, Sn, V, Ta, Mo, W, Fe, Co, Mn, and Al, and
• 0≤v≤4, 0<w<2, 0≤x<2, 0<y<6, 0≤z<3, and −0.5≤δ≤0.5 hold.