Active material, nonaqueous electrolyte battery, battery pack, and method of producing active material

1. An active material comprising a niobium titanium composite oxide whose average composition is represented by Li y Nb 2+x Ti 1−x O 7+0.5x (0≤x≤0.5, 0≤y≤5.5) and which satisfies peak intensity ratios represented by the following formulae (1) to (3):

0.05≤(B/A)≤0.7  (1)

0.01≤(C/A)≤0.2  (2)

0≤(D/A)≤0.1  (3)

wherein A is an intensity of a peak derived from Nb 2 TiO 7 at 2θ of 26.0±0.1° in a wide angle X-ray diffraction pattern using CuKα rays as an X-ray source, B is an intensity of a peak derived from Nb 10 Ti 2 O 29 at 2θ of 25.0±0.1° in the wide angle X-ray diffraction pattern, C is an intensity of a peak derived from Nb 24 TiO 62 at 2θ of 24.8±0.1° in the wide angle X-ray diffraction pattern, and D is an intensity of a peak derived from a TiO 2 rutile phase at 2θ of 27.4±0.2° in the wide angle X-ray diffraction pattern.

2. The active material according to claim 1 , wherein the peak intensity ratio (D/A) satisfies 0<(D/A)≤0.1.

3. The active material according to claim 1 , wherein the peak intensity ratio (B/A) satisfies 0.06≤(B/A)≤0.5.

4. The active material according to claim 1 , wherein the peak intensity ratio (C/A) satisfies 0.01≤(C/A)≤0.1.

5. A nonaqueous electrolyte battery comprising:

a positive electrode;

a negative electrode containing the active material according to claim 1 ; and

a nonaqueous electrolyte.

6. A battery pack comprising the nonaqueous electrolyte battery according to claim 5 .

7. A method of producing the active material of claim 1 , comprising:

first sintering a mixture comprising TiO 2 particles and Nb 2 O 5 particles at 600° C. to 1100° C., wherein the Nb 2 O 5 particles have an average particle diameter smaller than an average particle diameter of the TiO 2 particles, to produce a first sintered mixture; and

second sintering the first sintered mixture at 1300° C. to 1400° C. to obtain oxide.

8. The method according to claim 7 , further comprising annealing the oxide at 600° C. to 1000° C. after the second sintering.

9. The method according to claim 7 , further comprising cooling the oxide after the second sintering.

10. The active material according to claim 1 , wherein:

the peak intensity ratio (D/A) satisfies 0<(D/A)≤0.1;

the peak intensity ratio (B/A) satisfies 0.06≤(B/A)≤0.5; and

the peak intensity ratio (C/A) satisfies 0.01≤(C/A)≤0.1.

11. The active material according to claim 1 , wherein the peak intensity ratio (D/A) satisfies 0.005≤(D/A)≤0.1.

12. The active material according to claim 1 , wherein the peak intensity ratio (B/A) satisfies 0.05≤(B/A)≤0.5.

13. The active material according to claim 1 , wherein the niobium titanium composite oxide comprises phases having different composition ratios of Nb/Ti each other.

14. The active material according to claim 1 , wherein the niobium titanium composite oxide comprises a phase of Nb 2 TiO 7 , a niobium titanium composite oxide phase having a different composition ratio of Nb/Ti from the phase of Nb 2 TiO 7 and a TiO 2 rutile phase.

15. The active material according to claim 14 , wherein the niobium titanium composite oxide phase comprises a phase of Nb 10 Ti 2 O 29 or a phase of Nb 24 TiO 62 .

16. The active material according to claim 1 , further comprising titanium oxide compounds.

17. The active material according to claim 16 , wherein the titanium oxide compounds comprise at least one compound selected from a group consisting of titanium dioxide having an anatase structure, titanium dioxide having a bronze structure, lithium titanate having a ramsdellite structure, and lithium titanate having a spinel structure.

18. The active material according to claim 1 , wherein the active material is made by a method comprising:

first sintering a mixture comprising TiO 2 particles and Nb 2 O 5 particles at 600° C. to 1100° C., wherein the Nb 2 O 5 particles have an average particle diameter smaller than an average particle diameter of the TiO 2 particles, to produce a first sintered mixture; and

second sintering the first sintered mixture at 1300° C. to 1400° C. to obtain oxide.

19. The active material according to claim 18 , wherein an average particle diameter of the Nb 2 O 5 particles is 1 μm or less and an average particle diameter of the TiO 2 particles is 4 μm or more.

20. The active material according to claim 1 , wherein:

the peak intensity ratio (D/A) satisfies 0.005≤(D/A)≤0.025;

the peak intensity ratio (B/A) satisfies 0.05≤(B/A)≤0.57; and

the peak intensity ratio (C/A) satisfies 0.01≤(C/A)≤0.14.