Active material, nonaqueous electrolyte battery, battery pack, and method of producing active material
地域：
Minato-ku
摘要
According to one embodiment, an active material containing a niobium titanium composite oxide is provided. The niobium titanium composite oxide has average composition represented by LiyNb2+xTi1?xO7+0.5x (0≤x≤0.5, 0≤y≤5.5). The niobium titanium composite oxide 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).
說明書
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This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-236687, filed Oct. 26, 2012, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to an active material, a nonaqueous electrolyte battery, a battery pack, and a method of producing an active material.
In a niobium titanium composite oxide such as Nb2TiO7, when Li is inserted, Nb is charge-compensated (from plus-pentavalent to plus-trivalent) and Ti is charge-compensated (from plus-quadrivalent to plus-trivalent). Thus, it has a high theoretical capacity of 387.6 mAh/g. Consequently, the niobium titanium composite oxide is expected to replace Li4Ti5O12 as a high capacity material; however, the rate performance is low. Generally, Nb-rich niobium titanium composite oxides, such as Nb10Ti2O29 and Nb24TiO62 are excellent in lithium absorption and release characteristics as compared with Nb2TiO7. However, the content ratio of Nb increases, which leads to an increase in cost.
權(quán)利要求
What is claimed is:1. An active material comprising a niobium titanium composite oxide whose average composition is represented by LiyNb2+xTi1?xO7+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 Nb2TiO7 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 Nb10Ti2O29 at 2θ of 25.0±0.1° in the wide angle X-ray diffraction pattern, C is an intensity of a peak derived from Nb24TiO62 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 TiO2 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 TiO2 particles and Nb2O5 particles at 600° C. to 1100° C., wherein the Nb2O5 particles have an average particle diameter smaller than an average particle diameter of the TiO2 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 Nb2TiO7, a niobium titanium composite oxide phase having a different composition ratio of Nb/Ti from the phase of Nb2TiO7 and a TiO2 rutile phase. 15. The active material according to claim 14 , wherein the niobium titanium composite oxide phase comprises a phase of Nb10Ti2O29 or a phase of Nb24TiO62. 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 TiO2 particles and Nb2O5 particles at 600° C. to 1100° C., wherein the Nb2O5 particles have an average particle diameter smaller than an average particle diameter of the TiO2 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 Nb2O5 particles is 1 μm or less and an average particle diameter of the TiO2 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.
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