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EP-4737600-A1 - HYDROGEN STORAGE MATERIAL, HYDROGEN STORAGE CONTAINER, AND HYDROGEN SUPPLY DEVICE

EP4737600A1EP 4737600 A1EP4737600 A1EP 4737600A1EP-4737600-A1

Abstract

Provided is a hydrogen storage material comprising a TiFe-based alloy having excellent durability, good initial activation, and sufficient amount of hydrogen stored and hydrogen absorption/desorption characteristics. Also provided are a hydrogen storage container including the hydrogen storage material and a hydrogen supply apparatus including the hydrogen storage container. There are provided a hydrogen storage material comprising an alloy having a specific elemental composition represented by Formula (1), wherein, in a 1000 times magnified COMP image of a cross section obtained by EPMA, 10 or more and 3000 or less La-enriched phases having a size of 0.1 µm or more and 10 µm or less are present in a field of view of 85 µm × 120 µm, a hydrogen storage container including the hydrogen storage material, and a hydrogen supply apparatus including the hydrogen storage container. [Chem. 1] Ti (1-a-b) La a M1 b Fe c Mn d M2 e C f (1)

Inventors

  • OTSUKI, TAKAYUKI
  • HAYASHI, HIROKI
  • KAWAGUCHI, YASUHIKO
  • NISHIMOTO, MASAKAZU
  • HATANAKA, HIROSHI

Assignees

  • Santoku Corporation

Dates

Publication Date
20260506
Application Date
20240619

Claims (10)

  1. A hydrogen storage material comprising an alloy of an elemental composition represented by Formula (1) below, wherein, in a 1000 times magnified COMP image of a cross section of the alloy obtained by EPMA, 10 or more and 3000 or less pieces of a phase in which La is enriched, having a phase size of 0.1 µm or more and 10 µm or less, are present in a field of view of 85 µm × 120 µm of the COMP image, [Chem. 1] Ti (1-a-b) La a M1 b Fe c Mn d M2 e C f (1) wherein M1 represents at least one selected from the group consisting of V, Zr, Nb, and Ta, and M2 represents at least one selected from transition metal elements (excluding rare earth elements, M1, Ti, Fe, and Mn), Al, B, Ga, Si, and Sn; here, the rare earth elements include Sc and Y; and a is 0.0011 ≤ a ≤ 0.016, b is 0 ≤ b ≤ 0.20, c is 0.40 ≤ c ≤ 1.15, d is 0 ≤ d ≤ 0.40, e is 0 ≤ e ≤ 0.20, f is 0 ≤ f ≤ 0.07, and c + d + e is 0.60 ≤ c + d + e ≤ 1.20.
  2. The hydrogen storage material according to claim 1, wherein the alloy is pulverized and classified to have a particle size of 300 to 500 µm and an oxygen content of the alloy powder is 500 ppm or less.
  3. The hydrogen storage material according to claim 1, wherein, after an alloy powder obtained by pulverizing the alloy and classified to have a particle size of 300 to 500 µm is subjected to treatments (1) to (3) below, an oxygen content of an alloy powder having a particle size of 150 µm or less is 6000 ppm or less: (1) evacuation is performed at 85°C for about 2 hours; (2) after pressurization is performed at a hydrogen pressure of about 2.7 MPa, the temperature is switched to -20°C and hydrogen is absorbed until the hydrogen pressure stabilizes; and (3) after the operations of (1) to (2) are repeated three times, evacuation is performed at 85°C for about 5 hours to desorb hydrogen.
  4. The hydrogen storage material according to claim 1, wherein, in a PCT absorption curve, which is a hydrogen pressure-composition isotherm diagram at 30°C, the alloy satisfies a relational expression of 0 ≤ log 10 (P a2 ) - log 10 (P a1 ) ≤ 0.65 wherein P a1 is a hydrogen absorption pressure at a hydrogen content of 0.3 wt%, and P a2 is a hydrogen absorption pressure at a hydrogen content of 1.3 wt%.
  5. The hydrogen storage material according to claim 1, wherein, in a PCT desorption curve, which is a hydrogen pressure-composition isotherm diagram at 30°C, the alloy satisfies a relational expression of 0 ≤ log 10 (P b2 ) - log 10 (P b1 ) ≤ 0.80 wherein P b1 is a hydrogen desorption pressure at a hydrogen content of 0.3 wt%, and P b2 is a hydrogen desorption pressure at a hydrogen content of 1.3 wt%.
  6. The hydrogen storage material according to claim 1, wherein, in a PCT desorption curve, which is a hydrogen pressure-composition isotherm diagram at 30°C, the alloy satisfies a relational expression of 1.2 ≤ [0.2/{log 10 (P b4 ) - log 10 (P b3 )}] wherein P b3 is a hydrogen desorption pressure at a hydrogen content of +0.10 wt% from a starting point, the starting point being defined as an intersection of an equilibrium pressure of 0.01 MPa and the PCT desorption curve, and P b4 is a hydrogen desorption pressure at a hydrogen content of +0.30 wt% from the starting point.
  7. The hydrogen storage material according to any one of claims 1 to 6, wherein the alloy is subjected to mechanical alloying treatment.
  8. The hydrogen storage material according to any one of claims 1 to 6, wherein the hydrogen storage material is formed of a composite in which the alloy and a resin are mixed.
  9. A hydrogen storage container comprising the hydrogen storage material according to any one of claims 1 to 6.
  10. A hydrogen supply apparatus comprising the hydrogen storage container according to claim 9.

Description

TECHNICAL FIELD The present invention relates to a hydrogen storage material, a hydrogen storage container, and a hydrogen supply apparatus. BACKGROUND ART A hydrogen storage alloy is an alloy capable of reversibly absorbing and desorbing hydrogen, and has already been used as a negative electrode material of a nickel-metal hydride secondary battery, and is also expected as a material capable of safely storing hydrogen, which is attracting attention as an energy source these days, and is being put into practical use for hydrogen storage/supply systems. There are various hydrogen storage alloys such as an ABS-based type, an AB2-based type, a TiFe-based type, and a BCC-based type such as TiVCr; among these, a TiFe-based alloy is a material that is made of the most inexpensive source materials and is most expected as hydrogen storage use in which a much larger amount than the amount used for a battery is needed. However, the TiFe-based alloy is a difficult-to-use alloy type because the activation is not easy and the initial activation needs application of a temperature of 400°C or higher and a pressure of 3 MPa or more. It is known that various additive elements are effective for the improvement; for example, technologies shown in the following patent literatures are known. Patent Literature 1 discloses a titanium-based hydrogen storage alloy represented by the formula Ti1+kFe1-lMn1Am (where 0 ≤ k ≤ 0.3, 0 < 1 ≤ 0.3, 0 < m ≤ 0.1, and A is an element composed of at least one of niobium and the rare earth elements). Patent Literature 1 further discloses that an alloy that is easy to activate and has a sufficient amount of hydrogen stored is obtained by adding Mn and an A element (at least one of Nb and the rare earth elements) to a TiFe alloy. Patent Literature 2 discloses a hydrogen storage alloy made of an alloy having a composition represented by the general formula (T1-aFea)100-b-c-dLabMcM'd (where T is at least one element selected from Ti, Zr, and Hf, M is at least one element selected from V, Nb, Ta, Cr, Mo, and W, M' is at least one element selected from Mn, Co, Ni, Cu, Zn, B, Al, Ge, and Sn, a is 0.45 ≤ a ≤ 0.55 in terms of atomic ratio, and b, c, and d are 0.01 ≤ b ≤ 10, 0 ≤ c ≤ 20, and 0 ≤ d ≤ 30 in terms of atomic%, respectively), in which minute pieces of a crystalline phase having a crystal grain size of 10 µm or less are precipitated in at least part of the alloy structure. Patent Literature 2 further discloses that a hydrogen storage alloy excellent in hydrogen storage characteristics and corrosion resistance is obtained by appropriately setting the kinds of the elements constituting the T component, Fe, the La component, the M component, and the M' component in the general formula and the composition ratio of each component and, after cooling and solidification, performing heat treatment to precipitate minute pieces of a crystalline phase. Patent Literature 3 discloses a hydrogen storage alloy made of an alloy having a composition represented by the general formula AaTbMcM'd (where A is at least one element selected from Ti, Zr, Hf, and V, T is at least one element selected from Ni, Co, Fe, Cu, Mn, and Cr, M is at least one element selected from Al, Si, Ga, Ge, Zn, Sn, In, and Sb, M' is at least one element selected from B, C, N, and P, and a, b, c, and d are 20 ≤ a ≤ 70, 30 ≤ b ≤ 60, 5 ≤ c ≤ 40, 0.1 ≤ d ≤ 10, and a + b + c + d = 100 in terms of atomic%), in which minute pieces of a crystalline phase having a crystal grain size of 10 µm or less are precipitated in at least part of the alloy structure. Patent Literature 3 further discloses that a hydrogen storage alloy excellent in hydrogen storage characteristics and corrosion resistance is obtained by appropriately setting the kinds of the elements constituting the A component, the T component, the M component, and the M' component in the general formula and the composition ratio of each component and, after cooling and solidification, performing heat treatment to precipitate minute pieces of a crystalline phase. CITATION LIST PATENT LITERATURE Patent Literature 1: JP S61-250136 APatent Literature 2: JP H10-265875 APatent Literature 3: JP H10-265888 A SUMMARY OF INVENTION TECHNICAL PROBLEM The addition of the rare earth element described in Patent Literature 1 and Patent Literature 2 is effective in improving the initial activation, increasing the amount of hydrogen stored, increasing the equilibrium pressure during hydrogen absorption and desorption, eliminating the two-stage plateau, and the like, however, the excessive addition of the rare earth element causes an increase in the oxygen content of the alloy, leading to deterioration of durability. Therefore, an object of the present invention is to provide a hydrogen storage material having a TiFe-based alloy which is excellent in durability, has good initial activation, and exhibits a sufficient amount of hydrogen stored and hydrogen absorption/desorption characteristics while suppressing th