Active material, electrode, secondary battery, battery pack, and vehicle
According to one embodiment, an active material is provided. The active material includes a primary particle including an Nb 10 Ti 2 O 29 phase and at least one Nb-rich phase selected from an Nb 14 TiO 37 phase and an Nb 24 TiO 64 phase. In the primary particle, a ratio M Nb /M Ti of substance amount of niobium to titanium satisfies 5.0<M Nb /M Ti ≤24.0. A diffraction chart according to a wide angle X-ray diffraction method using a CuKα ray for the active material includes a peak A and a peak C attributed to the Nb 10 Ti 2 O 29 phase and a peak B appearing within a range of 2θ of 25.5±0.2° attributed to the Nb-rich phase. The active material satisfies a peak intensity ratio represented by 0<I B /I A <5.0. A half width of the peak C is in a range of 0.15° or more and 0.80° or less.
1 . An active material comprising a primary particle,
the primary particle comprising an Nb 10 Ti 2 O 29 phase and at least one Nb-rich phase selected from the group consisting of an Nb 14 TiO 37 phase and an Nb 24 TiO 64 phase,
a molar ratio Nb/Ti of niobium to titanium in the primary particle satisfying 5.0<Nb/Ti≤24.0,
a diffraction chart according to a wide angle X-ray diffraction method using a CuKα ray as an X-ray source for the active material comprising:
a peak A appearing within a range of 2θ of 24.9±0.2° attributed to the Nb 10 Ti 2 O 29 phase;
a peak B appearing within a range of 2θ of 25.5±0.2° attributed to the Nb-rich phase; and
a peak C appearing within a range of 2θ of 23.7±0.2° attributed to the Nb 10 Ti 2 O 29 phase,
the active material satisfying a first peak intensity ratio represented by following formula (1) and a second peak intensity ratio represented by following formula (2):
0< I B /I A <5.0 (1)
0≤ I D /I A <0.01 (2)
where I A is a peak intensity of the peak A, I B is a peak intensity of the peak B, and I D is a peak intensity of a peak D appearing within a range of 2θ of 20.1±0.2° attributed to the Nb 2 TiO 7 phase in the diffraction chart, and
a half width of the peak C being in a range of 0.15° or more and 0.80° or less.
2 . The active material according to claim 1 , wherein the first peak intensity ratio I B /I A is within a range of 0.01 or more and 1.20 or less.
3 . The active material according to claim 1 , wherein the molar ratio Nb/Ti satisfies 6.5≤Nb/Ti≤12.0.
4 . The active material according to claim 1 , wherein the half width of the peak C is within a range of 0.20° or more and 0.45° or less.
5 . The active material according to claim 1 , further comprising at least one selected from the group consisting of Ta, K, and P.
6 . An electrode comprising the active material according to claim 1 .
7 . The electrode according to claim 6 , wherein the electrode comprises an active material-containing layer containing the active material.
8 . A secondary battery comprising:
a positive electrode;
a negative electrode; and
an electrolyte,
wherein the negative electrode is the electrode according to claim 6 .
9 . A battery pack comprising the secondary battery according to claim 8 .
10 . The battery pack according to claim 9 , further comprising:
an external power distribution terminal; and
a protective circuit.
11 . The battery pack according to claim 9 , further comprising plural of the secondary battery, the secondary batteries being electrically connected in series, in parallel, or in a combination of in series and in parallel.
12 . A vehicle comprising the battery pack according to claim 9 .
13 . The vehicle according to claim 12 , further comprising a mechanism that converts kinetic energy of the vehicle into regenerative energy.