A magnesium-based hydrogen storage alloy containing holmium and a method for preparing the same

Abstract

This invention belongs to the field of functional metallic materials technology, specifically relating to a holmium-containing magnesium-based hydrogen storage alloy and its preparation method. This invention aims to address the insufficient low-temperature hydrogen desorption performance and high dehydrogenation temperature of existing magnesium-based hydrogen storage alloys. The magnesium-based hydrogen storage alloy of this invention comprises magnesium, nickel, and gadolinium, and also contains holmium (Ho), with an atomic percentage of 0.2%–0.6%. This alloy possesses a long-period stacked ordered structure and a stacking fault structure, wherein the LPSO phase includes 14H-type and / or 18R-type. This alloy is prepared by melting pure magnesium, Mg-Ni, Mg-Gd, and Mg-Ho master alloys according to a predetermined composition, followed by water quenching and ball milling. This invention, through the addition of trace amounts of Ho, promotes the transformation of 18R-LPSO to 14H-LPSO, increases the stacking fault density, and significantly improves the alloy's low- and medium-temperature hydrogen absorption and desorption performance. Under conditions of 250°C and 0.01 MPa, the hydrogen desorption capacity reaches 4.32 wt.% in 30 minutes, an increase of 81.5% compared to the base alloy without Ho addition. This invention is mainly applied to the field of solid-state hydrogen storage, and is particularly suitable for hydrogen energy storage and transportation scenarios that require specific operating temperatures.

Description

Technical Field

[0001] This invention belongs to the field of functional metal materials technology, specifically relating to a holmium-containing magnesium-based hydrogen storage alloy and its preparation method. Background Technology

[0002] We are currently at a critical juncture in the global energy structure's accelerated transition to clean and low-carbon energy, and hydrogen, due to its environmental friendliness and renewable nature, is considered one of the important alternative energy sources to fossil fuels. However, hydrogen's low density, flammability, and easy diffusion make its large-scale safe storage and transportation quite challenging. Solid-state hydrogen storage has attracted widespread attention due to its high safety and large volumetric hydrogen storage density.

[0003] Magnesium-based hydrogen storage materials possess advantages such as abundant resources, low cost, and high theoretical hydrogen storage capacity (approximately 7.6 wt.%), making them one of the most promising solid-state hydrogen storage materials. However, existing magnesium-based hydrogen storage alloys generally suffer from problems such as slow hydrogen absorption and desorption kinetics, high operating temperatures, difficulty in activation, and excessively high thermodynamic stability, which severely restrict their engineering applications.

[0004] Alloying is one of the most common and effective strategies for improving the performance of magnesium-based hydrogen storage. Adding transition elements such as Ni to Mg can form Mg-Ni hydrogen storage alloys and related hydrides, which helps improve the thermodynamic and kinetic properties of hydrogen storage reactions. However, typical Mg-Ni hydrogen storage alloys still suffer from slow hydrogen absorption / desorption rates, poor activation performance, and high operating temperatures. Furthermore, adding rare earth elements to Mg-Ni alloys can form Mg-Ni-RE hydrogen storage alloys. During hydrogen absorption, rare earth elements can form nanoscale rare earth hydrides (REHx), providing rapid interfacial channels for hydrogen atom diffusion and synergistically weakening Mg-H bonds, thus improving the hydrogen absorption / desorption process. Simultaneously, these alloys typically form long-period stacked ordered structures (LPSO phases) of magnesium-rich intermetallic compounds, which significantly impact the kinetic performance and cycle stability of magnesium-based hydrogen storage alloys. For example, Chinese patents CN102337438B and CN110257651A both disclose Mg-Ni-Y hydrogen storage alloys with LPSO structures, confirming the positive role of Y element in forming the LPSO phase and improving hydrogen storage performance. Mg-Ni-Gd alloys are one such highly promising magnesium-based hydrogen storage alloy system.

[0005] Adding trace amounts of rare earth elements to magnesium alloys can significantly improve the hydrogen storage performance of the LPSO phase by replacing some rare earth atoms in the original rare earth phase and regulating its structure, morphology, quantity, and distribution. Simultaneously, the addition of rare earth elements such as Ho can reduce the stacking fault energy of magnesium alloys, thereby increasing the stacking fault density. Stacking faults not only facilitate the formation of the LPSO phase but also serve as channels for the rapid diffusion of hydrogen atoms, playing a positive role in improving the alloy's hydrogen absorption and desorption performance. While Chinese patent CN120758773A attempts to introduce Yb ​​elements into Mg-Ni-Y alloys to optimize performance, it primarily focuses on the conventional grain refinement effect and does not reveal how to precisely control the LPSO phase transformation path and stacking fault density through specific rare earth elements.

[0006] In summary, although existing technologies recognize that rare-earth alloying to form the LPSO phase can improve the performance of magnesium-based hydrogen storage alloys, research on Mg-Ni-Gd alloys is still insufficient. In particular, there is a lack of effective methods for finely controlling the LPSO structure through specific rare-earth elements, such as inducing the transformation of 18R-LPSO to 14H-LPSO and increasing stacking fault density, to further reduce the dehydrogenation temperature and significantly improve low- and medium-temperature hydrogen desorption performance. Therefore, developing a novel magnesium-based hydrogen storage alloy capable of achieving the aforementioned microstructure control and breakthrough hydrogen storage performance is a pressing technical problem in this field. Summary of the Invention

[0007] This invention aims to address the technical problems of insufficient low-temperature hydrogen desorption performance and high dehydrogenation temperature in existing magnesium-based hydrogen storage alloys (especially Mg-Ni-RE alloys). It provides a method for improving the hydrogen storage performance of Mg-Ni-Gd alloys by adding trace amounts of Ho. Specifically, by adding a specific amount of Ho to the Mg-Ni-Gd base alloy, combined with optimized melting and ball milling processes, the formation of the LPSO phase and the transformation of 18R-LPSO to 14H-LPSO in the alloy are promoted. This increases the stacking fault density, refines α-Mg dendrites, and optimizes the volume fraction and distribution of the LPSO phase, thereby effectively reducing the dehydrogenation temperature of the alloy and significantly improving its low-temperature hydrogen absorption and desorption capacity and rate.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: Regarding the alloy composition, the magnesium-based hydrogen storage alloy comprises magnesium, nickel, and gadolinium, and further comprises holmium (Ho), wherein the atomic percentage of holmium is 0.2% to 0.6%. Preferably, the atomic percentage of nickel is 0.5% to 1.5%, and the atomic percentage of gadolinium is 0.5% to 2.0%. In one specific embodiment, the atomic percentage of nickel is 0.75%, the atomic percentage of gadolinium is 1.0%, and the atomic percentage of holmium is 0.4%.

[0009] In terms of microstructure, the magnesium-based hydrogen storage alloy has a long-period stacked ordered structure (LPSO), which includes a 14H-type long-period phase and / or an 18R-type long-period phase. Furthermore, the alloy has a stacking fault structure, which is at least partially distributed within the LPSO structure.

[0010] Regarding the preparation method, the magnesium-based hydrogen storage alloy is prepared by a method including the following steps: pure magnesium, Mg-Ni master alloy, Mg-Gd master alloy and Mg-Ho master alloy are smelted according to a predetermined composition to obtain an alloy ingot; the alloy ingot is mechanically crushed and then ball-milled under a protective atmosphere to obtain magnesium-based hydrogen storage alloy powder.

[0011] Specifically, the smelting is carried out under a protective atmosphere of mixed SF6 and CO2 at a temperature of 700℃ to 750℃; the ball milling speed is 150 to 250 rpm, the ball milling time is 5 to 20 hours, the ball-to-material ratio is (15 to 30): 1, and an organic dispersant (such as n-heptane, n-hexane, cyclohexane or anhydrous ethanol) is added, with the amount of the dispersant added being 0.4 to 0.8 ml per gram of alloy raw material.

[0012] In one specific implementation, pure magnesium ingots and Mg-25Ni, Mg-30Gd, and Mg-20Ho master alloys are used as raw materials, and the proportions are calculated as follows: Ni 0.75%, Gd 1.0%, and Ho 0.4% by atomic percentage. The mixture is smelted at 730°C in a protective atmosphere of SF6 and CO2, with stirring for 3 minutes every 5 minutes during the smelting process, for a total of 4 times. The mixture is then water-quenched to obtain an ingot. The ingot is pulverized and ball-milled at 200 rpm for 10 hours using n-heptane as a dispersant (0.6 ml / g) in a planetary ball mill (with a 10-minute pause every 10 minutes of operation and scraping of the powder once in between) to obtain alloy powder.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: First, significant optimization of the microstructure. This invention achieves precise control over the microstructure of the Mg-Ni-Gd base alloy by adding trace amounts of Ho (0.2%~0.6%). Specifically, the addition of Ho promotes the transformation of the long-period stacked ordered structure in the alloy from the blocky 18R type to the lamellar 14H type, significantly increasing the volume fraction of the LPSO phase and effectively increasing the stacking fault density in the alloy. Stacking faults not only provide favorable conditions for the formation of the LPSO phase, but also serve as channels for the rapid diffusion of hydrogen atoms and preferential nucleation sites for hydrides, thus laying the microstructural foundation for improving hydrogen absorption and desorption kinetics.

[0014] Second, a breakthrough improvement in low- and medium-temperature hydrogen desorption performance. Compared with the base alloy without Ho, the Mg-Ni-Gd-Ho quaternary alloy prepared in this invention achieves significant improvements in both hydrogen storage capacity and hydrogen absorption / desorption rate. Particularly noteworthy is that, under low- and medium-temperature conditions of 250℃, the hydrogen desorption capacity of this alloy reaches 4.32 wt.% within 30 minutes, an increase of 81.5% compared to the 2.38 wt.% of the base alloy, representing a qualitative leap in low- and medium-temperature hydrogen desorption performance. This breakthrough effect far exceeds the range expected by those skilled in the art through conventional rare-earth alloying methods, fully demonstrating the special promoting effect of Ho on the performance of magnesium-based hydrogen storage alloys.

[0015] Third, the thermodynamic stability was optimized and the reaction mechanism was transformed favorably. The hydrogen absorption and desorption enthalpy changes of the alloy of this invention were reduced to 74.50 kJ / mol and 77.94 kJ / mol, respectively, which are about 9.5% and 9.8% lower than those of the basic alloy, indicating that the thermodynamic stability of the alloy was effectively optimized and the dehydrogenation energy barrier was significantly reduced. Meanwhile, JMAK model fitting analysis showed that under low-temperature hydrogen absorption conditions of 250℃, the hydrogenation reaction mechanism of the alloy changed from the single one-dimensional growth mode of the basic alloy to a composite mechanism of three-dimensional growth followed by one-dimensional growth. This favorable transformation of the reaction mechanism, combined with the nanocomposite catalytic network composed of HoH2, GdH2, GdH3, and Mg2Ni-related hydrides formed in situ during hydrogen absorption, jointly promoted the rapid permeation and reaction of hydrogen at low temperatures, opening up a feasible path for the engineering application of magnesium-based hydrogen storage materials in medium and low-temperature environments. Attached Figure Description

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will now be described in detail with reference to the accompanying drawings, wherein... Figure 1 This is a comparison chart of the hydrogen absorption and desorption performance of magnesium alloys in Example 1 and Comparative Example 1 of the present invention; in, Figure 1 (a) and (d) are the hydrogen absorption and desorption curves of Comparative Example 1; Figure 1 (b) and (e) are the hydrogen absorption and desorption curves of Example 1; Figure 1 (c) and (f) are bar charts showing the hydrogen absorption and desorption capacities of Comparative Example 1 and Example 1 at different temperatures, respectively. Figure 2 The thermodynamic properties of magnesium alloys in Example 1 and Comparative Example 1 of this invention are shown in the diagram. in, Figure 2 (a) and (c) show the PCT curves of Comparative Example 1 at different temperatures and the corresponding Van't Hoff fitting curves; Figure 2 (b) and (d) show the PCT curves of Example 1 at different temperatures and the corresponding Van't Hoff fitting curves; Figure 3 These are transmission electron microscope (TEM) images of the magnesium alloys of Example 1 and Comparative Example 1 of the present invention. in, Figure 3 (a) is a TEM image of Comparative Example 1; Figure 3 (b) is a TEM image of Example 1. Detailed Implementation

[0017] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0018] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0019] This invention provides a method for improving the hydrogen storage performance of Mg-Ni-Gd alloys by adding trace amounts of Ho. The core of this method lies in adding a specific amount of Ho to the Mg-Ni-Gd base alloy and combining it with optimized melting and ball milling processes to effectively control the LPSO phase structure (promoting the transformation of 18R-LPSO to 14H-LPSO) and stacking fault density in the alloy, thereby significantly improving the hydrogen absorption and desorption performance of the alloy at medium and low temperatures.

[0020] Example 1 This embodiment provides a method for improving the hydrogen storage performance of Mg-Ni-Gd alloys by adding trace amounts of Ho, specifically including the following steps: I. Alloy Composition Design The chemical composition of the magnesium-based hydrogen storage alloy designed in this embodiment, by atomic percentage, is as follows: Ni: 0.75 at.%; Gd: 1.0 at.%; Ho: 0.4 at.%; the remainder is Mg and unavoidable impurities.

[0021] II. Melting and Preparation of Ingots (1) Pure magnesium ingot (99.99 wt.%) and three intermediate alloys, Mg-25Ni (wt.%), Mg-30Gd (wt.%) and Mg-20Ho (wt.%), were used as raw materials and were formulated according to the designed composition.

[0022] (2) Prepare a release coating using anhydrous ethanol and boron nitride, apply it evenly to the inner surface of a steel crucible, and dry it. Place pure magnesium ingots into the crucible and place it in a resistance furnace at a melting temperature of 730℃.

[0023] (3) After the pure magnesium has completely melted, Mg-Ni, Mg-Gd and Mg-Ho master alloys are added in sequence. The entire smelting process is carried out under a protective atmosphere of SF6 and CO2 to prevent the magnesium melt from oxidizing and burning.

[0024] (4) After the alloy has completely melted, use a long-handled strainer to remove the oxides from the surface of the alloy melt. Then, stir the magnesium alloy melt with an electric stirrer every 5 minutes for 3 minutes each time, for a total of 4 times. After stirring, keep it in the resistance furnace for 5 minutes.

[0025] (5) After standing and keeping warm, turn off the power, take out the crucible, and quench the melt in water under a protective atmosphere to obtain magnesium alloy ingots.

[0026] III. Preparation of Alloy Powders by Ball Milling (1) Use a metal file to crush the cast alloy into larger alloy cutters.

[0027] (2) Weigh the alloy cuttings in the glove box and divide them into two equal portions. Put them into two ball mill jars respectively and add the ball milling beads at a ball-to-material ratio of 25:1.

[0028] (3) Use n-heptane as a dispersant and add it to the ball mill jar at a rate of 0.6 ml / g.

[0029] (4) Remove the ball mill jar from the glove box and prepare alloy powder using a planetary ball mill. The ball milling parameters are set as follows: rotation speed 200 rpm; effective ball milling time 10 h; pause for 10 min every 10 min to prevent overheating and cold welding.

[0030] (5) After 5 hours of effective ball milling, remove the milling jar and scrape off the powder in a glove box to prevent severe cold welding. Repeat the above ball milling steps until the effective ball milling time reaches 10 hours. After ball milling, remove the sample for hydrogen storage performance testing.

[0031] IV. Hydrogen Storage Performance Testing This embodiment uses a Sieverts hydrogen absorption and desorption tester to evaluate the hydrogen storage performance of the above-mentioned alloy powder. The specific test method is as follows: (1) Hydrogen absorption performance Weigh approximately 100 mg of alloy powder and place it into the sample chamber. Heat the sample to the set temperatures (350°C, 320°C, 300°C, 250°C) under vacuum and hold for 30 minutes to ensure complete degassing. Then, introduce 4 MPa of high-purity hydrogen into the sample chamber, record the pressure change over time in real time, and calculate the hydrogen absorption using the ideal gas law.

[0032] See test results Figure 1 (b) and (c), the hydrogen absorption capacity at each temperature after 120 min at 4 MPa H2 is shown in Table 1: Table 1

[0033] (2) Hydrogen release performance After hydrogen absorption reaches saturation, the sample chamber temperature is maintained at the set temperature, the valve is opened to reduce the pressure to a vacuum condition of 0.01 MPa, the pressure recovery is recorded, and the amount of hydrogen released is calculated.

[0034] See test results Figure 1 (e) and (f), hydrogen was released at 0.01 MPa H2 for 30 min, and the hydrogen release capacity at each temperature is shown in Table 2: Table 2

[0035] (3) Thermodynamic and kinetic characteristics Thermodynamic parameter calculation: See Figure 2 (b) and (d), based on the PCT curves at different temperatures, the plateau pressure corresponding to different hydrogen absorption amounts was calculated, and Van't Hoff curves were plotted. The enthalpy change ΔH and entropy change ΔS of the hydrogen absorption reaction were obtained through linear fitting. In this embodiment, the enthalpy change of hydrogen absorption of the alloy decreased to -74.50 kJ / mol, and the enthalpy change of hydrogen release was +77.94 kJ / mol; the entropy change of hydrogen absorption was -137.38 J / (K*mol), and the entropy change of hydrogen release was 142.53 J / (K*mol).

[0036] Kinetic Analysis: The hydrogen absorption kinetics curves were fitted using the JMAK model (Johnson-Mehl-Avrami-Kolmogorov equation). The fitting results show that the alloy in this embodiment exhibits superior nucleation-growth behavior during hydrogen absorption. In particular, under the low-temperature hydrogen absorption condition of 250°C, the hydrogenation reaction mechanism of the alloy in this embodiment presents a composite mechanism of first three-dimensional growth (JMAK exponent n≈2) followed by one-dimensional growth (n≈1), which is beneficial for the rapid penetration and reaction of hydrogen at low temperatures.

[0037] V. Microstructure Characterization The microstructure of the as-cast alloy was observed using transmission electron microscopy (TEM). Figure 3 As shown in (b), a high-density stacking fault structure is formed in the alloy of this embodiment, and a large number of lamellar 14H-type long-period stacked ordered phases (14H-LPSO) appear.

[0038] Comparative Example 1 This comparative example provides a basic magnesium-based hydrogen storage alloy without added Ho, whose chemical composition, by atomic percentage, is: Ni: 0.75%; Gd: 1.0%; the remainder being Mg and unavoidable impurities.

[0039] The elemental composition (at%) of the magnesium alloys of Example 1 and Comparative Example 1 is shown in Table 3: Table 3

[0040] The smelting, water quenching, and ball milling processes of Comparative Example 1 were exactly the same as those of Example 1, except that Ho master alloy was not added.

[0041] See the hydrogen storage performance test results. Figure 1 (a), (d), (c), (f).

[0042] Hydrogen absorption capacity (4 MPa H, 120 min) is shown in Table 4; hydrogen release capacity (0.01 MPa H, 30 min) is shown in Table 5. Table 4

[0043] Table 5

[0044] Thermodynamic parameters are shown in the following table. Figure 2 (a) and (c) show that the hydrogen absorption enthalpy of Comparative Example 1 is -78.33 kJ / mol and the hydrogen release enthalpy is +80.66 kJ / mol; the hydrogen absorption entropy is -143.65 J / (K*mol) and the hydrogen release entropy is 146.24 J / (K*mol).

[0045] For microstructure characterization, see [link to microstructure characterization] Figure 3 (a) In the alloy of Comparative Example 1, the LPSO phase is mainly of the blocky 18R type with a low stacking fault density.

[0046] Example 1 (with 0.4 at.% Ho added) was compared with Comparative Example 1 (the base alloy without Ho added): Microstructure comparison: In Comparative Example 1, the LPSO phase is mainly blocky 18R type with low stacking fault density; while in Example 1, the LPSO phase transforms from 18R type to 14H type, and the stacking fault density is significantly increased. This indicates that the addition of Ho promotes the transformation of 18R-LPSO to 14H-LPSO and significantly increases the stacking fault density of the alloy.

[0047] Hydrogen storage performance comparison: Example 1 showed higher hydrogen absorption capacity than Comparative Example 1 at all test temperatures. In particular, at 250°C, the hydrogen release rate of Example 1 in 30 minutes was 4.32 wt.%, which was 81.5% higher than the hydrogen release rate of Comparative Example 1 (2.38 wt.%).

[0048] Thermodynamic performance comparison: The hydrogen absorption enthalpy change and hydrogen release enthalpy change of Example 1 are both lower than those of Comparative Example 1, indicating that the addition of Ho reduces the thermodynamic stability of the alloy and is beneficial to the dehydrogenation reaction.

[0049] Comparison of reaction mechanisms: Under the low-temperature hydrogen absorption condition of 250℃, Comparative Example 1 exhibits a single one-dimensional growth mode (JMAK index≈1), while Example 1 transforms into a composite mechanism of first three-dimensional growth (n≈2) and then one-dimensional growth (n≈1), indicating that Ho element improves the low-temperature hydrogen absorption reaction mechanism.

[0050] In other embodiments of the present invention, the above technical solutions can be appropriately modified as follows without departing from the core of the present invention: (1) Adjustability of ball milling parameters: The ball milling speed is not limited to 200 rpm, for example, it can be adjusted in the range of 150 to 250 rpm; the effective ball milling time is not limited to 10 h, for example, it can be selected in the range of 8 to 15 h; the amount of dispersant n-heptane added can also be varied between 0.5 and 0.8 ml / g, as long as alloy powder with high density stacking faults and lamellar 14H-LPSO phase can be obtained.

[0051] (2) Replacement of smelting equipment: resistance furnace can be replaced by induction smelting furnace, and the mechanical stirring step can be reduced or replaced by electromagnetic stirring.

[0052] (3) Selection of protective atmosphere: In addition to SF6 and CO2 mixed gas, argon (Ar) or Ar+SF6 mixed gas can also be used as protective atmosphere.

[0053] (4) Allowable fluctuation of Ho content: Although the Ho content in the example is 0.4 at.%, a deviation of ±0.05 at.% is allowed in actual production, and hydrogen storage performance can still be obtained that is better than that of the base alloy without added Ho.

[0054] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to specific embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A holmium-containing magnesium-based hydrogen storage alloy, said magnesium-based hydrogen storage alloy comprising magnesium, nickel and gadolinium, characterized in that, The magnesium-based hydrogen storage alloy further comprises holmium, and the atomic percentage of holmium is 0.2% to 0.6%.

2. The magnesium-based hydrogen storage alloy according to claim 1, characterized in that, The atomic percentage of nickel is 0.5% to 1.5%, and the atomic percentage of gadolinium is 0.5% to 2.0%.

3. The magnesium-based hydrogen storage alloy according to claim 1 or 2, characterized in that, The atomic percentage of nickel is 0.75%, the atomic percentage of gadolinium is 1.0%, and the atomic percentage of holmium is 0.4%.

4. The magnesium-based hydrogen storage alloy according to claim 1, characterized in that, The magnesium-based hydrogen storage alloy has a long-period stacked ordered structure, which includes a 14H-type long-period phase and / or an 18R-type long-period phase.

5. The magnesium-based hydrogen storage alloy according to claim 4, characterized in that, The magnesium-based hydrogen storage alloy has a stacking fault structure, and the stacking fault structure is at least partially distributed in the long-period stacked ordered structure.

6. The magnesium-based hydrogen storage alloy according to claim 1, characterized in that, The magnesium-based hydrogen storage alloy is prepared by a method comprising the following steps: Pure magnesium, Mg-Ni master alloy, Mg-Gd master alloy and Mg-Ho master alloy are smelted according to a predetermined composition to obtain alloy ingots; The alloy ingot was mechanically crushed and then ball-milled under a protective atmosphere to obtain magnesium-based hydrogen storage alloy powder.

7. The magnesium-based hydrogen storage alloy according to claim 6, characterized in that, The smelting is carried out under a protective atmosphere of SF6 and CO2 at a temperature of 700℃ to 750℃; the ball milling speed is 150 to 250 rpm, the ball milling time is 5 to 20 hours, the ball-to-material ratio is (15 to 30):1, and an organic dispersant is added.

8. The magnesium-based hydrogen storage alloy according to claim 7, characterized in that, The organic dispersant is n-heptane, n-hexane, cyclohexane, or anhydrous ethanol, and the amount of the dispersant added is 0.4 to 0.8 ml per gram of alloy raw material.

9. The magnesium-based hydrogen storage alloy according to claim 1, characterized in that, The magnesium-based hydrogen storage alloy has a hydrogen absorption capacity of ≥5.9 wt.% at 350℃ and 4MPa hydrogen pressure, and a hydrogen absorption capacity of ≥5.5 wt.% at 250℃ and 4MPa hydrogen pressure.

10. The magnesium-based hydrogen storage alloy according to claim 1, characterized in that, The magnesium-based hydrogen storage alloy exhibits a hydrogen release rate of ≥4.0 wt.% within 30 minutes at 250℃ and 0.01 MPa hydrogen pressure.

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