Active material for battery, nonaqueous electrolyte battery, and battery pack
In general, according to one embodiment, the active material for a battery contains a niobium composite oxide represented by the formula: Li x M (1-y) Nb y Nb 2 O (7+δ) . M represents at least one kind selected from the group consisting of Ti and Zr. X, y, and δ are numbers respectively satisfying the following: 0≦x≦6, 0≦y≦1, and −1≦δ≦1). The pH of the active material for a battery is from 7.4 to 12.5.
1. An active material for a battery comprising: a niobium composite oxide represented by the formula Li x M (1-y) Nb y Nb 2 O (7+δ) ,
wherein M represents at least one kind selected from the group consisting of Ti and Zr,
x, y, and δ are numbers respectively satisfying the following: 0≦x≦6, 0≦y≦1, and −1≦δ≦1, and
the pH of the active material for a battery is from 7.4 to 12.5.
2. The active material for a battery according to claim 1 , wherein carbonate ions are arranged on at least one part of the surface of the active material for a battery.
3. The active material for a battery according to claim 1 , wherein lithium carbonate is arranged on at least one part of the surface of the active material for a battery.
4. The active material for a battery according to claim 1 , wherein the pH is a pH measured when the specific surface area of the active material for a battery is from 0.5 to 50 m 2 /g.
5. The active material for a battery according to claim 1 , wherein the pH is a pH measured when the specific surface area of the active material for a battery is from 3 to 30 m 2 /g.
6. The active material for a battery according to claim 1 , wherein a crystal structure of the niobium composite oxide belongs to a monoclinic system.
7. The active material for a battery according to claim 1 , wherein the crystal structure of the niobium composite oxide belongs to a space group C/2m or P12/m1.
8. The active material for a battery according to claim 1 , wherein the carbon content of the active material for a battery is from 0.01 to 3% by mass based on the total amount of the active material for a battery.
9. The active material for a battery according to claim 1 , wherein the active material for a battery has a peak belonging to the carbonate ion (CO 3 − ) in the range of 1430±30, the range of 1500±30, or the range of 2350±30 cm −1 in an infrared reflectance spectrum with Fourier transform infrared spectrophotometer (FT-IR).
10. A nonaqueous electrolyte battery comprising:
a positive electrode;
a negative electrode comprising the active material for a battery according to claim 1 ; and
a nonaqueous electrolyte.
11. A battery pack comprising one or more nonaqueous electrolyte batteries according to claim 10 .
12. The battery pack according to claim 11 , wherein the plurality of nonaqueous electrolyte batteries are connected electrically to each other, and the battery pack further comprises a protective circuit that can detect the voltage of each of the nonaqueous electrolyte batteries.