Active material, nonaqueous electrolyte battery, battery pack and vehicle

1. An active material comprising particles of a Na-containing niobium titanium composite oxide having an orthorhombic crystal structure,

wherein a peak intensity I 1 of a strongest peak P 1 within a range of 3350 to 3450 cm −1 is 1.6 or less in an infrared diffuse reflectivity spectrum of a surface of the particles, according to a diffuse reflectance Fourier transform spectrometry measurement, and

wherein the Na-containing niobium titanium composite oxide is represented by a general formula of:

Li 2+v Na 2−w M1 x Ti 6−y−z Nb y M2 z O 14+δ ,

wherein:

0≤v≤0.2;

0<w<2;

0.05≤x≤0.2;

0<y<6;

0≤z<3;

−0.5≤δ≤0.5;

M1 is at least one metal element selected from the group consisting of Cs, K, Mg, Sr, Ba and Ca; and

M2 is at least one metal element selected from the group consisting of Zr, Sn, V, Ta, Mo, W, Fe, Co, Mn, and Al.

2. The active material according to claim 1 , wherein, in the infrared diffuse reflectivity spectrum, a peak intensity I 2 of a strongest peak P 2 within a range of 1410 to 1460 cm −1 is within a range of 6≤I 2 ≤10.

3. The active material according to claim 1 , wherein the peak intensity I 1 of the strongest peak P 1 is within a range of 1 or more and 1.6 or less.

4. The active material according to claim 1 , wherein the peak intensity I 1 of the strongest peak P 1 is within a range of 1.2 or more and 1.5 or less.

5. The active material according to claim 1 , wherein a value of y is within a range of 0.1≤y≤1.

6. The active material according to claim 1 , wherein a value of w is within a range of 0.1≤w≤1.

7. A nonaqueous electrolyte battery comprising:

a negative electrode comprising the active material according to claim 1 ;

a positive electrode; and

a nonaqueous electrolyte.

8. The nonaqueous electrolyte battery according to claim 7 , wherein the positive electrode comprises at least one selected from the group consisting of a lithium cobalt composite oxide, a lithium nickel cobalt manganese composite oxide, a lithium manganese composite oxide having a spinel structure, and a lithium manganese iron composite phosphate having an olivine structure.

9. A battery pack comprising the nonaqueous electrolyte battery according to claim 7 .

10. The battery pack according to claim 9 , further comprising:

an external power distribution terminal, and

a protective circuit.

11. A battery pack comprising nonaqueous electrolyte batteries each according to claim 7 , wherein the nonaqueous electrolyte batteries are electrically connected in series, in parallel, or in combination of series and parallel.

12. A vehicle comprising the battery pack according to claim 9 .

13. The vehicle according to claim 12 , wherein the battery pack is configured to recover a regenerative energy of a power of the vehicle.