Second-stage hydrogen storage alloy of two-stage metal hydride hydrogen compressor and preparation method of second-stage hydrogen storage alloy

Abstract

The invention belongs to the technical field of hydrogen storage materials, and particularly discloses a second-stage hydrogen storage alloy of a two-stage metal hydride hydrogen compressor and a preparation method of the second-stage hydrogen storage alloy. The chemical equation of the second-stage hydrogen storage alloy of the two-stage metal hydride hydrogen compressor is Ti < 0.84 > Zr < 0.16 > MnaCrbFe < 0.1 >, a is larger than or equal to 0.9 and smaller than or equal to 1.1, and b is larger than or equal to 0.7 and smaller than or equal to 1.0. The invention further provides a preparation method of the Ti-Mn-based hydrogen storage alloy. According to the hydrogen storage alloy, a non-stoichiometric modification process is used, and the purpose of regulating and controlling the performance of the alloy is achieved by controlling the quality of smelting elements. The prepared hydrogen storage alloy has the advantages of being easy to activate, high in reversible hydrogen storage density, excellent in dynamic performance, long in cycle life and the like, and is very suitable for being used as a second-stage hydrogen storage alloy of a two-stage metal hydride hydrogen compressor.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen storage materials, and specifically discloses a second-stage hydrogen storage alloy for a two-stage metal hydride hydrogen compressor and a preparation method thereof. Background Art

[0002] Energy is an important foundation for the development of modern science and technology and social progress, and is also a necessary condition for the survival and development of mankind. Since the industrial revolution, with the rapid development of economy and technology, people's demand for energy has been increasing. Currently, the main energy used globally is non-renewable fossil energy. Therefore, it is crucial to find new sustainable clean energy.

[0003] Hydrogen energy is a clean energy with high energy density, which can be produced by a zero-carbon method. Combined with efficient fuel cell technology, clean and efficient hydrogen fuel cell vehicles (FCEVs) can be produced. Since more than 30% of the energy globally is applied to transportation, as a new technology, FCEVs have very good development and application prospects. For the development of FCEVs, it is necessary to build and improve the hydrogen energy infrastructure - hydrogen refueling stations. As the core equipment of hydrogen refueling stations, hydrogen compressors are one of the research focuses in the current hydrogen energy field.

[0004] In an alloy compressor system, its core material is the hydrogen storage alloy used to compress hydrogen. Metals, alloy-based intermetallic compounds that can reversibly absorb and release hydrogen are collectively called hydrogen storage alloys. Hydrogen storage alloys can react with hydrogen to form hydrides and release heat under certain temperature and hydrogen pressure conditions; metal hydrides absorb heat and decompose to release hydrogen.

[0005] Currently, the hydrogen storage materials used for hydrogen compressors usually include AB5 series, AB2 series, and AB series, etc. Most early metal hydride compressors relied on AB5 alloys. However, recent methods either use AB2 alloys or a combination of AB5 and AB2 alloys, where AB5 is used for the low-pressure stage and AB2 is used for the high-pressure stage. AB2 alloys provide a wider range of equilibrium hydrogen pressures and can achieve higher delivery pressures. In addition, due to the scarcity of the main component rare earth metals in AB5 alloys and the rising price of nickel, the MHHC design based on AB2 alloys is more cost-effective.

[0006] AB2-type alloys, with their high reversible capacity, good hydrogen absorption and desorption kinetics, and relatively low cost, are one of the most promising solid-state hydrogen storage materials. However, difficult activation and poor cycle stability limit their application in solid-state hydrogen storage. Therefore, it is of great significance to further optimize AB2-type hydrogen storage alloy materials to prepare a hydrogen storage alloy for a two-stage metal hydride hydrogen compressor. Summary of the Invention

[0007] Aiming at the deficiencies of AB2-type hydrogen storage alloy materials, such as difficult activation and poor cycle stability, the purpose of the present invention is to provide a hydrogen storage alloy material with improved hydrogen absorption and desorption performance and its preparation method. By adjusting the stoichiometric ratio of the elements on the B side of the alloy, the activation performance of the hydrogen storage material is significantly improved, the kinetic rate is accelerated, the hysteresis is reduced, and the cycle life is increased.

[0008] The chemical formula of the hydrogen storage alloy of the second stage of the two-stage metal hydride hydrogen compressor of the present invention is: Ti 0.84 Zr 0.16 Mn a Cr b Fe 0.1 , where 0.9 ≤ a ≤ 1.1 and 0.7 ≤ b ≤ 1.0.

[0009] This hydrogen storage alloy has a single C14-type Laves phase crystal structure.

[0010] The preparation method of the hydrogen storage alloy of the second stage of the two-stage metal hydride hydrogen compressor is as follows:

[0011] (1) Weigh the materials according to the element ratio of the hydrogen storage alloy Ti 0.84 Zr 0.16 Mn a Cr b Fe.

[0012] Among them, the purity of Ti is 99%, the purity of Zr is 99%, the purity of Mn is 99%, the purity of Cr is 99.5%, and the purity of Fe is 99.7%.

[0013] (2) Under an argon atmosphere, melt the metals in an arc furnace, and then refine them at 1473 - 1523K for 10 - 15 minutes to obtain an alloy ingot. During the alloy melting, turn it over and remelt it three times to ensure uniform distribution of each element in the alloy ingot;

[0014] (3) Anneal the alloy ingot to obtain the hydrogen storage alloy.

[0015] The annealing process is as follows: Place the alloy ingot in the furnace tube of a tube furnace filled with argon, anneal it at 1123 - 1173K for 10 hours, then take out the furnace tube and air-cool it to obtain the hydrogen storage alloy.

[0016] The advantages and beneficial effects of the present invention are:

[0017] 1. By adjusting the stoichiometric ratio and controlling the mass of each element during melting, the present invention optimizes the alloy performance. Its preparation method is simple and easy to operate. At the same time, expensive metals such as V and La are not added during the melting process, so the cost is low and it can be applied to large-scale production.

[0018] 2. The hydrogen storage alloy prepared by the present invention is easy to activate, and the first activation can be completed within 10 minutes at room temperature when hydrogen is introduced.

[0019] 3. The hydrogen storage alloy prepared by the present invention has excellent hydrogen absorption and desorption kinetic properties. Under the conditions of a temperature of 40 °C and an initial hydrogen pressure of 7 MPa, the optimized alloy only takes 43 seconds to reach 90% of the maximum hydrogen absorption capacity.

[0020] 4. The hydrogen storage material prepared by the present invention adopts an annealing treatment to improve its hydrogen absorption and desorption kinetic properties and the operating efficiency of the hydrogen compressor; at the same time, it makes the element distribution more uniform, reduces the hysteresis of the hydrogen absorption and desorption plateau, and improves the hydrogen absorption and desorption cycle life. After 500 long-cycle hydrogen absorption and desorption cycles, the volume hydrogen storage density measured under the conditions of 25 °C and 7 MPa decreases from 1.818 wt.% at the beginning to 1.745 wt.%, and the capacity retention rate is 96.2%. Description of the Drawings

[0021] Figure 1 is Ti 0.84 Zr 0.16 Mn a Cr 0.7 Fe 0.1 and Ti 0.84 Zr 0.16 Mn 0.9 Cr b Fe 0.1 XRD pattern of the alloy; in the figure, the abscissa 2θ represents the diffraction angle (degree), and the ordinate Intensity represents the relative intensity (a.u.).

[0022] Figure 2 (a)- Figure 2 (b) is Ti 0.84 Zr 0.16 Mn a Cr 0.7 Fe 0.1 and Ti 0.84 Zr 0.16 Mn 0.9 Cr b Fe 0.1 Initial activation curve of the alloy. Among them, Figure 2 (a) is Ti 0.84 Zr 0.16 Mn a Cr 0.7 Fe 0.1 , Figure 2 (b) is Ti 0.84 Zr 0.16 Mn 0.9 Cr b Fe 0.1 .

[0023] Figure 3 is Ti 0.84Zr 0.16 Mn a Cr 0.7 Fe 0.1 and Ti 0.84 Zr 0.16 Mn 0.9 Cr b Fe 0.1 PCT curves of the alloy at 7 MPa high-purity hydrogen (volume purity 99.999%) at 313 and 303 K; among them, (a) is Ti 0.84 Zr 0.16 Mn a Cr 0.7 Fe 0.1 , (b) is Ti 0.84 Zr 0.16 Mn 0.9 Cr b Fe 0.1 ; in the figure, the abscissa Hydrogen content represents the mass hydrogen storage density (wt.%), and the ordinate Pressure represents the hydrogen pressure (MPa).

[0024] Figure 4 is Ti 0.84 Zr 0.16 Mn a Cr 0.7 Fe 0.1 Isothermal hydrogen absorption curves of the alloy at 7 MPa high-purity hydrogen (volume purity 99.999%); among them, (a) is the hydrogen absorption curve and (b) is the normalized curve; in the figure, the abscissa Time represents the time (s), and the ordinate Hydrogen content represents the mass hydrogen storage density (wt.%).

[0025] Figure 5 is Ti 0.84 Zr 0.16 Mn 0.9 Cr b Fe 0.1 Isothermal hydrogen absorption curves of the alloy at 7 MPa high-purity hydrogen (volume purity 99.999%); among them, (a) is the hydrogen absorption curve and (b) is the normalized curve; in the figure, the abscissa Time represents the time (s), and the ordinate Hydrogen content represents the mass hydrogen storage density (wt.%)

[0026] Figure 6 PCT curve of the alloy in Example 1 after 30 minutes of ball milling treatment at 303 K; in the figure, the abscissa Hydrogen content represents the mass hydrogen storage density (wt.%), and the ordinate Pressure represents the hydrogen pressure (MPa).

[0027] Figure 7 XRD curve of the alloy of Example 1 during 500 hydrogen absorption and desorption cycles under 7 MPa high-purity hydrogen (volume purity 99.999%); in the figure, the abscissa 2θ represents the diffraction angle (degree), and the ordinate Intensity represents the relative intensity (a.u.).

[0028] Figure 8 PCT curve of the alloy of Example 1 at 313 K after 500 hydrogen absorption and desorption cycles under 7 MPa high-purity hydrogen (volume purity 99.999%); in the figure, the abscissa Hydrogen content represents the mass hydrogen storage density (wt.%), and the ordinate Pressure represents the hydrogen pressure (MPa).

[0029] Figure 9 PCT curve of the alloy of Example 3 at 313 K after 500 hydrogen absorption and desorption cycles under 7 MPa high-purity hydrogen (volume purity 99.999%); in the figure, the abscissa Hydrogen content represents the mass hydrogen storage density (wt.%), and the ordinate Pressure represents the hydrogen pressure (MPa). Detailed implementation manners

[0030] Now, various exemplary implementation manners of the present invention will be described in detail. This description should not be regarded as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0031] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail. Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention description, which are obvious to those skilled in the art. Other implementation manners obtained from the description of the present invention are obvious to those skilled in the art. The description and examples of the present invention are only exemplary.

[0032] It should be noted that there are no special restrictions on the parameters of all raw materials involved in the present invention. Exemplarily, in the following examples, the purity of Ti is 99%, the purity of Zr is 99%, the purity of Mn is 99%, the purity of Cr is 99.5%, and the purity of Fe is 99.7%; all are commercially available

[0033] Example 1

[0034] Step 1: The metals are mixed according to the stoichiometric ratio, melted in an electric arc furnace under an argon atmosphere, and refined at 1473K for 10 minutes. During the melting period, the metals are turned over and remelted three times to obtain an alloy ingot;

[0035] Step 2: Place the alloy ingot in an argon-filled tubular furnace, set the temperature to 1123K, anneal for 10 hours, remove the furnace tube and air cool to obtain a hydrogen storage alloy. 0.84 Zr 0.16 Mn 0.9 Cr 0.7 Fe 0.1 .

[0036] Performance test 1: The hydrogen storage alloy samples were activated and the hydrogen storage performance was tested. The experiment was carried out on the H2PCT-3101 three-channel fully automatic gas-solid reaction tester of the Gas Technology Group of the Shanghai Institute of Applied Physics, Chinese Academy of Sciences. The PCT curve test of hydrogen absorption and desorption adopted the Sieverts method. The purity of hydrogen was 99.999%. Process: Weigh about 1.5g of alloy and put it into the sample chamber, heat it to 303K, evacuate it for 40 minutes to remove impurities, and pass 7MPa of hydrogen to react with the sample. Repeat hydrogen absorption and desorption 3 times to ensure that the sample is fully activated, and then set different temperatures for hydrogen storage performance test. During the hydrogen absorption kinetics test, the initial inlet pressure of the sample chamber is higher than the hydrogen absorption equilibrium pressure of the alloy being tested. The pressure change over time during the entire experiment is recorded and converted into the change of hydrogen absorption amount over time, and the hydrogen absorption kinetics curve of the alloy at this temperature can be obtained.

[0037] At the same time, the Van't Hoff formula is used to calculate the enthalpy change and reaction entropy change of the hydrogen absorption and desorption reaction of the hydrogen storage alloy:

[0038] (Among them, P H2 is the equilibrium pressure of hydrogen absorption or desorption, P0 is the standard atmospheric pressure, ΔH and ΔS are the standard enthalpy variable and standard entropy variable respectively).

[0039] Test results: The mass hydrogen storage density at 298K is 1.83wt%, and the hydrogen absorption equilibrium pressure is 0.92MPa, which is easy to accept the hydrogen supply of the first-stage compressed working medium. Under the conditions of temperature of 40℃ and initial hydrogen pressure of 7MPa, it only takes 43 seconds to reach 90% of the maximum hydrogen absorption. The hydrogen absorption and desorption kinetics are fast and easy to activate. The enthalpy changes of hydrogen absorption and desorption are -21.5KJ·mol -1 and 26.1 kJ·mol -1 The entropy changes of hydrogen absorption and desorption are -89.2 J·mol -1 ·K -1 and 99.1 J·mol -1 ·K -1 .

[0040] Example 2

[0041] The preparation method is the same as that of Example 1, except that the hydrogen storage alloy is Ti 0.84 Zr 0.16 Mn 1.0 Cr 0.7 Fe 0.1 . Test results: The mass hydrogen storage density at 298K is 1.83wt%, the hydrogen absorption equilibrium pressure is 1.77MPa, and it is easy to accept the hydrogen supply from the first-stage compression working medium. Under the conditions of a temperature of 40°C and an initial hydrogen pressure of 7MPa, it only takes 49 seconds to reach 90% of the maximum hydrogen absorption amount, the hydrogen absorption and desorption kinetics speed is fast, and it is easy to activate. The hydrogen absorption and desorption enthalpy changes are -20.4KJ·mol -1 and 25.9KJ·mol -1 , and the hydrogen absorption and desorption entropy changes are -88.8J·mol -1 ·K -1 and 106.8J·mol -1 ·K -1

[0042] Example 3

[0043] The preparation method is the same as that of Example 1, except that the hydrogen storage alloy is Ti 0.84 Zr 0.16 Mn 1.1 Cr 0.7 Fe 0.1 .

[0044] Test results: The mass hydrogen storage density at 298K is 1.81wt%, the hydrogen absorption equilibrium pressure is 2.86MPa, and it is easy to accept the hydrogen supply from the first-stage compression working medium. Under the conditions of a temperature of 40°C and an initial hydrogen pressure of 7MPa, it only takes 103 seconds to reach 90% of the maximum hydrogen absorption amount, the hydrogen absorption and desorption kinetics speed is fast, and it is easy to activate. The hydrogen absorption and desorption enthalpy changes are -18.8KJ·mol -1 and 25.2KJ·mol -1 , and the hydrogen absorption and desorption entropy changes are -88.3J·mol -1 ·K -1 and 107.6J·mol -1 ·K -1 .

[0045] Performance test 2: The hydrogen storage alloys or hydrogen storage materials in Example 1 and Example 3 were subjected to a cyclic performance test for hydrogen storage, and the number of cycles included 10, 50, 200, and 500 times, and the hydrogen storage capacity retention rate was calculated.

[0046] Sample Example 1 Comparative Example 1 Hydrogen storage capacity retention rate (10 cycles) % 100 100 Hydrogen storage capacity retention rate (50 cycles) % 99.5 96.7 Hydrogen storage capacity retention rate (200 cycles) % 99 93.9 Hydrogen storage capacity retention rate (500 cycles) % 96.2 93.4

[0047] Example 4

[0048] The preparation method is the same as that of Example 1, except that the hydrogen storage alloy is

[0049] Ti 0.84 Zr 0.16 Mn 0.9 Cr 0.8 Fe 0.1 。

[0050] Test results: The mass hydrogen storage density at 303K is 1.80wt%, the hydrogen absorption equilibrium pressure is 1.67MPa, and it is easy to accept the hydrogen supply from the first-stage compression working medium. Under the conditions of a temperature of 45°C and an initial hydrogen pressure of 7MPa, it only takes 43 seconds to reach 90% of the maximum hydrogen absorption amount. The hydrogen absorption and desorption kinetics are fast and it is easy to activate. The enthalpy changes of hydrogen absorption and desorption are -21.2KJ·mol -1 and 26.0KJ·mol -1 respectively, and the entropy changes of hydrogen absorption and desorption are -90.9J·mol -1 ·K -1 and 105.2J·mol -1 ·K -1

[0051] Example 5

[0052] The preparation method is the same as that of Example 1, except that the hydrogen storage alloy is

[0053] Ti 0.84 Zr 0.16 Mn 0.9 Cr 0.9 Fe 0.1 。

[0054] Test results: The mass hydrogen storage density at 303K is 1.79wt%, the hydrogen absorption equilibrium pressure is 2.57MPa, and it is easy to accept the hydrogen supply from the first-stage compression working medium. Under the conditions of a temperature of 45°C and an initial hydrogen pressure of 7MPa, it only takes 83 seconds to reach 90% of the maximum hydrogen absorption amount. The hydrogen absorption and desorption kinetics are fast and it is easy to activate. The enthalpy changes of hydrogen absorption and desorption are -20.8KJ·mol -1 and 25.9KJ·mol -1 respectively, and the entropy changes of hydrogen absorption and desorption are -95.7J·mol -1 ·K -1 and 106.9J·mol -1 ·K -1

[0055] Example 6

[0056] The preparation method is the same as that of Example 1, except that the hydrogen storage alloy is Ti 0.84 Zr0.16 Mn 0.9 Cr 1.0 Fe 0.1 。

[0057] Test results: The mass hydrogen storage density at 303 K is 1.76 wt%, the hydrogen absorption equilibrium pressure is 3.86 MPa, and it can easily accept the hydrogen supply from the working medium of the first-stage compression. Under the conditions of a temperature of 45 °C and an initial hydrogen pressure of 7 MPa, it takes 170 seconds to reach 90% of the maximum hydrogen absorption amount. The hydrogen absorption and desorption kinetics are relatively fast and it is easy to activate. The enthalpy changes of hydrogen absorption and desorption are -20.4 KJ·mol -1 and 25.7 KJ·mol -1 respectively, and the entropy changes of hydrogen absorption and desorption are -99.5 J·mol -1 ·K -1 and 107.3 J·mol -1 ·K -1

[0058] Conclusion: It can be seen from the data of Examples 1 to 6 that when the total stoichiometry of the hydrogen storage alloy is within 1.7 - 2.0, as the proportion of alloying elements Mn and Cr on the B side decreases, the hydrogen storage alloy has a lower hydrogen absorption equilibrium pressure, a larger mass hydrogen storage density, and the hydrogen absorption kinetics rate is also improved. It should be noted that as the stoichiometric ratio decreases again, the hydrogen absorption plateau pressure will decrease again. When the plateau pressure is lower than 0.1 MPa (one atmosphere), it will be difficult to release hydrogen, resulting in a decrease in the reversible hydrogen storage capacity.

[0059] Comparative Example 1

[0060] The preparation method is the same as that of Example 1, except that: the hydrogen storage alloy is Ti 0.68 Zr 0.16 Mn 0.9 Cr 1.0 Fe 0.1 Ce 0.16 。

[0061] Test results: The mass hydrogen storage density at 298 K is 1.61 wt%, the hydrogen absorption equilibrium pressure is 1.90 MPa, and it can easily accept the hydrogen supply from the working medium of the first-stage compression. Under the conditions of a temperature of 45 °C and an initial hydrogen pressure of 7 MPa, it takes 71 seconds to reach 90% of the maximum hydrogen absorption amount. The hydrogen absorption and desorption kinetics are relatively fast and it is easy to activate. The enthalpy changes of hydrogen absorption and desorption are -18.4 KJ·mol -1 and 23.8 KJ·mol -1 respectively, and the entropy changes of hydrogen absorption and desorption are -89.1 J·mol -1 ·K -1 and 99.2 J·mol -1 ·K -1

[0062] Conclusion: From the data of Example 1 and Comparative Example 1, it can be seen that the addition of rare earth element Ce will reduce the performance of the alloy, the hydrogen absorption and desorption kinetic rate decreases, and the hydrogen storage density decreases from 1.81 wt% to 1.61 wt%.

[0063] Comparative Example 2

[0064] The preparation method is the same as that of Example 1, except that: the prepared hydrogen storage alloy was subjected to 30 min of mechanical ball milling treatment.

[0065] Both the ball milling tank and the steel balls used for grinding are made of stainless steel, and the diameter of the grinding balls is 5 mm. The specific experimental scheme is as follows: The alloy powder was sieved through a 300-mesh sieve, the steel balls and the alloy were weighed according to a mass ratio of 20:1, argon was filled into the tank, and the sample was mechanically ball milled at a speed of 350 r / min. Taking 10 min of ball milling and 10 min of rest as a cycle, the ball milling was cycled, and the total ball milling time was 30 min.

[0066] Test results: The mass hydrogen storage density at 298 K is 1.64 wt%, the hydrogen absorption equilibrium pressure is 1.33 MPa, and it is easy to accept the hydrogen supply of the first-stage compression working medium. Under the conditions of a temperature of 45 °C and an initial hydrogen pressure of 7 MPa, it takes 31.7 seconds to reach 90% of the maximum hydrogen absorption amount, the hydrogen absorption and desorption kinetic speed is fast, and it is easy to be activated. However, after 30 min of ball milling, the alloy particles gradually change from multi-angular irregular polygons to microsphere shapes, and agglomeration occurs, and the average particle size of the particles decreases from 30.99 μm to 9.01 μm, the hydrogen absorption surface area increases, the alloy activation speed increases, but the anti-oxygen poisoning performance weakens.

[0067] Conclusion: From the data of Example 1 and Comparative Example 2, it can be seen that after ball milling, the alloy particle size decreases, and the activation performance is significantly improved, but the hydrogen storage capacity of the alloy will decrease due to the poisoning effect of trace oxygen in the glove box (see Figure 6 ).

[0068] In summary, the hydrogen storage alloy prepared by the present invention has excellent hydrogen absorption and desorption kinetics, and the hydrogen absorption and desorption rate is significantly improved. Among them, the low stoichiometric ratio of Ti 0.84 Zr 0.16 Mn 0.9 Cr 0.7 Fe 0.1 has the best performance.

[0069] The implementation results show that the present invention prepares hydrogen storage alloys with different stoichiometric ratios, the preparation method is simple and the operation is convenient, and the performance of non-stoichiometric Mn and Cr elements on the hydrogen storage alloy is tested. It is found that the low stoichiometric ratio has faster hydrogen absorption and desorption kinetics, higher mass hydrogen storage density and better cycle capacity retention rate.

[0070] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the spirit of the present invention's design, various modifications and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A second-stage hydrogen storage alloy for a two-stage metal hydride hydrogen compressor, characterized in that: The chemical formula of the second stage hydrogen storage alloy of the two-stage metal hydride hydrogen compressor is: Ti 0.84 Zr 0.16 Mn a Cr b Fe 0.1 , among which, 0.9≤a≤1.1, 0.7≤b≤1.

0.

2. The second stage hydrogen storage alloy of the two-stage metal hydride hydrogen compressor according to claim 1, characterized in that: The hydrogen storage alloy has a single C14 type Laves phase crystal structure.

3. A method for preparing the second stage hydrogen storage alloy of the two-stage metal hydride hydrogen compressor according to claim 1, characterized in that: The steps of the preparation method of the hydrogen storage alloy are as follows: (1) According to the hydrogen storage alloy Ti 0.84 Zr 0.16 Mn a Cr b The ingredients are prepared by proportioning the Fe element; (2) Melting the metal in an electric arc furnace under an argon atmosphere, and then refining to obtain an alloy ingot. During the alloy smelting period, the alloy ingot is turned over and remelted three times to ensure that the elements of the alloy ingot are evenly distributed; (3) The alloy ingot is annealed to obtain the hydrogen storage alloy.

4. The method for preparing the second stage hydrogen storage alloy of the two-stage metal hydride hydrogen compressor according to claim 3, characterized in that: The purity of Ti is 99%, the purity of Zr is 99%, the purity of Mn is 99%, the purity of Cr is 99.5%, and the purity of Fe is 99.7%.

5. The method for preparing the second stage hydrogen storage alloy of the two-stage metal hydride hydrogen compressor according to claim 3, characterized in that: The refining is carried out at 1473-1523 K for 10-15 minutes.

6. The method for preparing the second stage hydrogen storage alloy of the two-stage metal hydride hydrogen compressor according to claim 3, characterized in that: The annealing step is: placing the alloy ingot in a tubular furnace filled with argon, annealing at 1123-1173K for 10 hours, and then taking out the furnace tube for air cooling to obtain the hydrogen storage alloy.

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