A Mg-Ni-based hydrogen storage alloy with added TiMn2 and its preparation method

Abstract

This invention belongs to the field of hydrogen storage materials technology, specifically relating to a Mg-Ni based hydrogen storage alloy with added TiMn2 and its preparation method. The hydrogen storage alloy of this invention consists of a Mg-Ni alloy matrix and a TiMn2 catalytic phase dispersed therein; the Mg-Ni alloy matrix has a mass percentage of 85-95 wt.% for Mg and 5-15 wt.% for Ni; the TiMn2 catalytic phase has a mass percentage of 5-15 wt.%; the TiMn2 catalytic phase is TiMn2 alloy powder that has been activated to exhibit room-temperature hydrogen absorption activity. The preparation method of this invention includes: preparing TiMn2 alloy powder and Mg-Ni alloy powder separately, and ball milling them together in the presence of a grinding aid. This invention introduces the TiMn2 catalytic phase activated by hydrogen absorption / desorption treatment into a magnesium-rich Mg-Ni alloy and uses a mild ball milling process to form a multiphase composite interface. The hydrogen storage alloy prepared by this invention exhibits good low-temperature hydrogen absorption / desorption performance and cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage materials technology, specifically relating to a Mg-Ni based hydrogen storage alloy with added TiMn2 and its preparation method. Background Technology

[0002] Driven by global energy transition and dual-carbon goals, hydrogen energy, as a clean, low-carbon, and high-energy-density secondary energy source, faces a key bottleneck in its large-scale application: safe and efficient storage and transportation technologies. Existing high-pressure gaseous hydrogen storage suffers from low volumetric hydrogen storage density, high pressure resistance requirements for storage and transportation equipment, and a significant risk of leakage. Cryogenic liquid hydrogen storage is hampered by high liquefaction energy consumption, complex equipment, and high storage and transportation costs. In contrast, solid-state hydrogen storage utilizes the reversible interaction between the storage material and hydrogen to achieve hydrogen storage and release, offering advantages such as high safety, high volumetric hydrogen storage density, and relatively mild storage and transportation conditions. Therefore, it has become an important research direction in the field of hydrogen energy storage and transportation.

[0003] Magnesium-based hydrogen storage materials are considered promising solid-state hydrogen storage materials due to their high theoretical hydrogen storage capacity, abundant resources, and low cost. Among them, magnesium-rich Mg-Ni hydrogen storage alloys have attracted widespread attention because they can improve the hydrogen absorption and desorption kinetics of the magnesium matrix through the Mg2Ni phase while maintaining a high magnesium content. However, magnesium-rich Mg-Ni alloys still face the common challenges of slow hydrogen absorption and desorption kinetics in the mid-to-low temperature range and relatively high hydrogen desorption temperatures, making it difficult to meet the rapid response requirements of scenarios such as on-board hydrogen storage and distributed hydrogen supply.

[0004] To improve the hydrogen absorption and desorption performance of magnesium-based or Mg-Ni-based hydrogen storage materials, various modification methods have been proposed in existing technologies.

[0005] For example, the literature (Interface-Engineered TiV Bimetal Catalysts…, J. Phys. Chem. Lett., 2025, 16, 8084) achieved a dehydrogenation rate of 3.0 wt.% within 40 min at 225 °C by introducing a TiV bimetallic catalyst into Mg-20Ni, but its low-temperature hydrogen absorption performance was still unsatisfactory: the hydrogen absorption rate at 225 °C for 60 min was <3 wt.%. Furthermore, existing patented technologies attempt to improve the kinetic performance of magnesium-based hydrogen storage materials through different approaches. CN117026034A proposes a Mg… 85 Ni 15-x Ti xHydrogen storage alloys, which use a hydrogenation combustion method to partially replace Ni atoms with Ti atoms to form ternary solid solutions / intermetallic compounds, can achieve relatively rapid hydrogen absorption at 250°C, but do not address hydrogen absorption capabilities below 100°C or even at room temperature. CN118221067A discloses a method for modifying a body-centered cubic hydrogen storage alloy with MgH2 composites, which can lower the dehydrogenation temperature, but its matrix is ​​MgH2 rather than a Mg-Ni alloy, and the hydrogen absorption test still exceeds 150°C.

[0006] While the aforementioned technologies can improve the hydrogen absorption and desorption performance of magnesium-based hydrogen storage materials to some extent, they still have problems such as insufficient hydrogen absorption capacity at low temperatures, limited hydrogen absorption performance near room temperature, or insufficient synergistic effect between the catalytic phase and the magnesium-rich Mg-Ni matrix.

[0007] AB2-type TiMn2 hydrogen storage alloys exhibit high hydrogen adsorption / desorption capacity at room temperature, high hydrogen dissociation activity, and good cycle stability. If activated TiMn2 alloys can be introduced as functional composite phases into magnesium-rich Mg-Ni alloys, and a multiphase composite interface can be formed through appropriate ball milling processes, it is expected to provide more active sites and transport channels for hydrogen adsorption, dissociation, and diffusion, thereby improving the hydrogen adsorption / desorption kinetics of magnesium-rich Mg-Ni alloys under medium- and low-temperature conditions, and even near-room temperature.

[0008] Therefore, there is an urgent need in the field to provide a Mg-Ni based hydrogen storage alloy with TiMn2 added and its preparation method, so as to improve the low-temperature hydrogen absorption and desorption rate, low-temperature hydrogen absorption capacity and cycle stability of the magnesium-rich Mg-Ni alloy while maintaining its high hydrogen storage capacity. Summary of the Invention

[0009] The present invention aims to overcome the problems of slow hydrogen absorption and desorption kinetics at medium and low temperatures, insufficient hydrogen absorption capacity at low temperatures, and the need to improve cycle stability in existing magnesium-rich Mg-Ni hydrogen storage alloys, and provides a Mg-Ni based hydrogen storage alloy with added TiMn2 and its preparation method.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A Mg-Ni-based hydrogen storage alloy with added TiMn2, The Mg-Ni-based hydrogen storage alloy is composed of a Mg-Ni alloy matrix and a TiMn2 catalytic phase dispersed therein; In the Mg-Ni alloy matrix, the mass percentage of Mg is 85~95wt.%, the mass percentage of Ni is 5~15wt.%, and all Ni elements exist in the form of Mg2Ni phase, while Mg elements exist in the forms of Mg phase and Mg2Ni phase. The TiMn2 catalyst phase accounts for 5~15 wt.% of the mass of the Mg-Ni based hydrogen storage alloy. The TiMn2 catalytic phase is TiMn2 alloy powder that has been activated to have room temperature hydrogen absorption activity.

[0011] As an optional implementation, the Mg content may be 85 wt.%, 90 wt.%, 92 wt.%, or 95 wt.%; the Ni content may be 15 wt.%, 10 wt.%, 8 wt.%, or 5 wt.%.

[0012] Furthermore, in the Mg-Ni alloy matrix, the mass percentage of Mg is 95 wt.% and the mass percentage of Ni is 5 wt.%; the mass percentage of the TiMn2 catalyst phase in the Mg-Ni based hydrogen storage alloy is 10 wt.%.

[0013] Furthermore, the TiMn2 catalytic phase is obtained through a pretreatment process including the following steps: Ti and Mn metals are mixed in an atomic ratio of 1:2, with Mn metal in excess of 3-5%, and TiMn2 alloy ingots are obtained by vacuum arc melting. The TiMn2 alloy ingot was vacuum annealed at 1000°C for 6 hours; The annealed TiMn2 alloy was subjected to hydrogen absorption and desorption activation treatment at 30°C and 4MPa hydrogen pressure for 3 to 5 times to obtain the TiMn2 alloy powder with room temperature hydrogen absorption activity.

[0014] Furthermore, the TiMn2 catalytic phase forms a microcrack structure and a newly formed active surface after being activated by hydrogen absorption and desorption.

[0015] This invention also provides a method for preparing a Mg-Ni-based hydrogen storage alloy with added TiMn2, comprising the following steps: TiMn2 alloy powder was prepared; Mg-Ni alloy powder was prepared; the TiMn2 alloy powder and the Mg-Ni alloy powder were ball-milled in the presence of a grinding aid to obtain the Mg-Ni-based hydrogen storage alloy with added TiMn2. The TiMn2 alloy powder is a TiMn2 alloy powder that has been activated to have room temperature hydrogen absorption activity; in the Mg-Ni alloy powder, the mass percentage of Mg is 85~95wt.% and the mass percentage of Ni is 5~15wt.%; the mass percentage of TiMn2 alloy powder in the ball-milled composite raw material is 5~15wt.%.

[0016] Preferably, the ball-to-material ratio in the ball milling process is 40-60:1, the ball milling speed is 400-450 rpm, the ball milling is intermittent, and the total milling time is 8-10 hours; specifically, the intermittent ball milling involves alternating between milling for 8-10 minutes and stopping for 8-10 minutes. The grinding aid is preferably tetrahydrofuran.

[0017] Furthermore, the TiMn2 alloy powder is prepared by the following steps: Ti and Mn metal elements are mixed in an atomic ratio of 1:2, with Mn metal element in excess of 3-5%. The mixture is then melted in a vacuum arc melting furnace under argon protection and an arc current of 140-160A. The melting process is repeated 3-5 times to obtain TiMn2 alloy ingots. The TiMn2 alloy ingot was vacuum annealed at 1000°C for 6 hours; The annealed TiMn2 alloy was subjected to hydrogen absorption and desorption activation treatment at 30°C and 4MPa hydrogen pressure for 3 to 5 times to obtain TiMn2 alloy powder with room temperature hydrogen absorption activity.

[0018] Furthermore, the Mg-Ni alloy powder is prepared by the following steps: Mg metal element and Mg-30wt.%Ni master alloy are batched according to the ratio of 95wt.% Mg and 5wt.% Ni, placed in a vacuum induction melting furnace, and melted at 780~820°C under argon protection. After complete melting, the mixture is held at the temperature for 3~5 minutes and cooled with the furnace to obtain a Mg-Ni alloy ingot. The Mg-Ni alloy ingot is then filed and crushed to obtain the Mg-Ni alloy powder.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses TiMn2 alloy powder that has undergone hydrogen absorption and desorption activation treatment as a catalyst phase introduced into the magnesium-rich Mg-Ni system. By utilizing the excellent hydrogen molecule dissociation ability and room temperature hydrogen absorption activity of TiMn2, the adsorption, dissociation and diffusion efficiency of hydrogen in the material is improved, thereby improving the hydrogen absorption and desorption kinetics performance of Mg-Ni based hydrogen storage alloy. This invention achieves synergistic optimization of hydrogen storage capacity and kinetic performance by controlling the TiMn2 catalytic phase content to 5–15 wt.%, while maintaining the high hydrogen storage capacity of magnesium-rich Mg-Ni alloys.

[0020] This invention employs an intermittent ball milling process to achieve uniform composite of the TiMn2 catalytic phase and the Mg-Ni matrix, which is beneficial for forming a stable catalytic interface and hydrogen diffusion channels, improving material activity, and reducing the adverse effects of temperature rise during ball milling.

[0021] The hydrogen storage alloy prepared by this invention exhibits excellent hydrogen absorption and desorption performance under medium and low temperature conditions, which can effectively improve the low-temperature hydrogen absorption rate and dehydrogenation efficiency. Among them, the sample with 10wt.% TiMn2 added shows the best comprehensive performance.

[0022] The hydrogen storage alloy prepared by this invention has good cycle stability and can maintain high hydrogen storage capacity and structural stability during multiple hydrogen absorption and desorption cycles, showing good application prospects. Attached Figure Description

[0023] 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 The XRD patterns of Example 3, Comparative Example 1, and TiMn2 alloy of the present invention are shown below. Figure 2 The isothermal dehydrogenation curves of various embodiments and comparative examples of the present invention at 220°C are shown below. Figure 3 The following are the isothermal hydrogen absorption curves of various embodiments and comparative examples of the present invention at 100°C; Figure 4 This is the isothermal hydrogen absorption curve of Example 3 of the present invention at 30°C; Figure 5 The hydrogen absorption and desorption curves for Example 3 of the present invention after 20 cycles at 260°C; Figure 6 The image shows the SEM image and elemental energy spectrum of Embodiment 3 of the present invention. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] In this embodiment of the invention, the preparation process is mainly completed using the following equipment: Electric arc melting furnace for preparing TiMn2 alloy ingots; vacuum annealing furnace for annealing TiMn2 alloy; A hydrogen storage performance testing system for TiMn2 activation treatment and hydrogen storage performance testing; Vacuum induction melting furnace, used for the preparation of Mg-Ni alloy ingots; Inert atmosphere glove box, used for powder weighing and loading; Planetary ball mill, used for compound ball milling; X-ray diffraction (XRD) is used for phase analysis; Scanning electron microscope (SEM) is used to observe the microstructure and grain size of materials after ball milling.

[0027] Example 1 This embodiment provides a method for preparing a Mg-5Ni hydrogen storage alloy with 5 wt.% TiMn2.

[0028] The preparation method in this embodiment specifically includes: First, Mg-5Ni alloy powder was prepared.

[0029] The raw materials were prepared with Mg accounting for 95 wt.% and Ni accounting for 5 wt.%. The Ni source was a Mg-30 wt.% Ni master alloy. The Mg raw material and the Mg-Ni master alloy were added to a graphite crucible in a vacuum induction melting furnace. After evacuation, argon gas was introduced for protection.

[0030] By controlling the heating power, the furnace temperature is raised to 780°C, and the raw materials are completely melted and held at that temperature for 3–5 minutes. After melting, the furnace is allowed to cool naturally for 40–60 minutes to obtain a Mg-5Ni alloy ingot. The ingot is then filed and crushed in air to obtain Mg-5Ni alloy powder.

[0031] Secondly, TiMn2 alloy powder was prepared.

[0032] The raw materials were prepared according to an atomic ratio of Ti:Mn = 1:2. Considering the volatilization and loss of Mn during the smelting process, an excess of 3-5% Mn was added. In this example, 2.93g of elemental Ti and 7.07g of elemental Mn were used. The raw materials were placed in a crucible of a vacuum arc melting furnace. After evacuation, high-purity argon was introduced as a protective atmosphere. The arc current was controlled at 150A for melting. To ensure uniform chemical composition, the melting was repeated four times, with each melting time being approximately 60 seconds. After melting, the TiMn2 alloy ingot was obtained by furnace cooling.

[0033] The ingot was placed in a vacuum annealing furnace. The annealing temperature was 1000°C, and the annealing time was 6 hours. Annealing achieved microstructure homogenization and eliminated internal stress. The annealed TiMn2 alloy was then placed in a hydrogen storage testing device for hydrogen absorption and desorption cycles. The activation temperature was 30°C, the hydrogen absorption pressure was 4 MPa, and the activation was performed three times. After activation, TiMn2 alloy powder with room-temperature hydrogen absorption activity was obtained. During the activation process, the TiMn2 alloy underwent volume expansion and micro-fragmentation after the first hydrogen absorption. The microcracks and newly formed active surfaces formed after activation increased hydrogen diffusion channels and improved the interfacial contact area between TiMn2 and the Mg-Ni matrix, thereby enhancing catalytic activity.

[0034] Finally, ball milling is performed.

[0035] In an argon-filled glove box, weigh out 0.0125g of TiMn2 alloy powder and 0.2375g of Mg-5Ni alloy powder, respectively, and place them into a 50mL zirconia ball mill jar. Add 15g of zirconia grinding balls and 1mL of tetrahydrofuran as a grinding aid.

[0036] After sealing, the grinding jar is installed on a planetary ball mill. Set the grinding parameters: rotation speed 450 rpm, using a forward and reverse intermittent grinding mode, specifically, rotating forward for 10 minutes, then stopping for 10 minutes, then rotating in reverse for 10 minutes, then stopping for 10 minutes, and so on, for a total grinding time of 10 hours.

[0037] After ball milling, the can was opened in an argon glove box, and residual tetrahydrofuran was removed by vacuuming the transition chamber of the glove box to obtain a Mg-5Ni hydrogen storage alloy with 5wt.% TiMn2 added, which was named Sample 1 of Example.

[0038] As an optional variation, the total ball milling time can be adjusted within the range of 8 to 10 hours, and the rotation speed can be adjusted within the range of 400 to 450 rpm, both of which can achieve good composite effects.

[0039] Example 2 This embodiment provides a method for preparing a Mg-5Ni hydrogen storage alloy with 7wt.% TiMn2 added.

[0040] Mg-5Ni alloy powder and TiMn2 alloy powder were prepared using the same method as in Example 1. In an argon glove box, 0.0175 g of TiMn2 alloy powder and 0.2325 g of Mg-5Ni alloy powder were weighed and placed into a ball mill jar. 15 g of zirconia grinding balls and 1 mL of tetrahydrofuran were added. The ball milling parameters were exactly the same as in Example 1: 450 rpm, intermittent ball milling in both forward and reverse directions, with a 10-minute break every 10 minutes, for a total time of 10 hours. After ball milling, a Mg-5Ni hydrogen storage alloy with 7 wt.% TiMn2 was obtained, named the sample of Example 2.

[0041] Example 3 This embodiment provides a method for preparing a Mg-5Ni hydrogen storage alloy with 10 wt.% TiMn2 added.

[0042] Mg-5Ni alloy powder and TiMn2 alloy powder were prepared using the same method as in Example 1. In an argon glove box, 0.025 g of TiMn2 alloy powder and 0.225 g of Mg-5Ni alloy powder were weighed and placed into a ball mill jar. 15 g of zirconia grinding balls and 1 mL of tetrahydrofuran were added. The ball milling parameters were exactly the same as in Example 1: 450 rpm, intermittent ball milling in both forward and reverse directions, with a 10-minute break every 10 minutes, for a total time of 10 hours. After ball milling, a Mg-5Ni hydrogen storage alloy with 10 wt.% TiMn2 was obtained, named Sample 3.

[0043] Example 4 This embodiment provides a method for preparing a Mg-5Ni hydrogen storage alloy with 15 wt.% TiMn2 added.

[0044] Mg-5Ni alloy powder and TiMn2 alloy powder were prepared using the same method as in Example 1. In an argon glove box, 0.0375 g of TiMn2 alloy powder and 0.2125 g of Mg-5Ni alloy powder were weighed and placed into a ball mill jar. 15 g of zirconia grinding balls and 1 mL of tetrahydrofuran were added. The ball milling parameters were exactly the same as in Example 1: 450 rpm, intermittent ball milling in both forward and reverse directions, with a 10-minute break every 10 minutes, for a total time of 10 hours. After ball milling, a Mg-5Ni hydrogen storage alloy with 15 wt.% TiMn2 was obtained, named Sample 4.

[0045] Comparative Example 1 This comparative example provides a method for preparing a pure Mg-5Ni hydrogen storage alloy without the addition of TiMn2.

[0046] Mg-5Ni alloy powder was prepared using the same method as in Example 1. In an argon-filled glove box, 0.25 g of Mg-5Ni alloy powder was weighed and placed in a ball mill jar, along with 15 g of zirconia grinding balls and 1 mL of tetrahydrofuran. The ball milling parameters were exactly the same as in Example 1: 450 rpm, intermittent ball milling in both forward and reverse directions, with a 10-minute pause every 10 minutes, for a total time of 10 hours. After ball milling, pure Mg-5Ni hydrogen storage alloy was obtained and named Comparative Example 1 sample.

[0047] Material characterization and hydrogen storage performance testing: 1. X-ray diffraction (XRD) analysis Test conditions: Cu target Kα radiation, scan step size 0.02°, scan angle 10°~80°.

[0048] like Figure 1The figures show the XRD patterns of the 10 wt.% TiMn2 / Mg-5Ni hydrogen storage alloy prepared in Example 3, the Mg-5Ni hydrogen storage alloy prepared in Comparative Example 1, and the TiMn2 alloy powder. As can be seen from the figures, the diffraction peaks of the TiMn2 alloy sample match the standard TiMn2 PDF card, indicating that the target TiMn2 phase was successfully obtained. In Comparative Example 1, characteristic peaks of the Mg phase and Mg2Ni phase are observed, indicating that Ni exists in the Mg matrix in the form of Mg2Ni. In the XRD pattern of the sample from Example 3, in addition to the Mg and Mg2Ni phases, characteristic peaks of the TiMn2 phase also appear, indicating that the TiMn2 alloy was successfully introduced into the Mg-Ni system. Furthermore, no obvious impurity phase peaks were found, indicating that no new unfavorable side reaction products were generated during the composite process.

[0049] 2. Hydrogen storage performance testing methods The hydrogen absorption and desorption performance of the samples was tested using a QuantumH-Sorb 4600PCT PRO hydrogen storage performance testing device. Before testing, the samples were activated 10 times at 320℃ using hydrogen absorption and desorption conditions: absorption time 60 min, absorption pressure 3.5 MPa; desorption conditions: desorption time 10 min, desorption pressure 0.01 MPa. The sample mass was 60-100 mg.

[0050] During the hydrogen absorption test, a constant temperature and pressure method was used; during the hydrogen dehydrogenation test, a constant temperature near-vacuum method was used. Subsequently, the hydrogen absorption and desorption performance of Examples 1-4 and Comparative Example 1 was evaluated.

[0051] 3. Isothermal hydrogen absorption and desorption performance test Test conditions: Hydrogen absorption pressure 3.5 MPa, dehydrogenation pressure 0.01 MPa. The comparison results of dehydrogenation and hydrogen absorption performance of each example and comparative example at 220°C and 100°C are as follows: Figure 2 , Figure 3 As shown in Table 1.

[0052] Table 1

[0053] As shown in Table 1, the dehydrogenation performance was significantly improved after adding TiMn2, with Example 3 (10 wt.%) showing the best effect, achieving a dehydrogenation amount of 4.13 wt.% at 220°C for 60 min, which is far superior to the 1.89 wt.% of Comparative Example 1. Notably, Example 3 achieved a hydrogen absorption amount of 4.20 wt.% at 100°C, higher than the 3.97 wt.% of Comparative Example 1, and also exhibited a faster hydrogen absorption rate. This indicates that the introduction of TiMn2 not only improved the hydrogen desorption kinetics but also significantly enhanced the low-temperature hydrogen absorption performance.

[0054] As the TiMn2 content increases from 5 wt.% to 10 wt.%, the number of catalytic sites increases, promoting hydrogen molecule dissociation and hydrogen atom diffusion, thus continuously improving hydrogen absorption and desorption performance. When the TiMn2 content is further increased to 15 wt.%, the excessively high proportion of the catalytic phase leads to a decrease in the proportion of the Mg-Ni phase, the main hydrogen storage phase, thereby reducing the hydrogen storage capacity and kinetic performance. Therefore, 10 wt.% is the optimal addition amount.

[0055] 4. Room temperature hydrogen absorption performance test like Figure 4 The figure shows the isothermal hydrogen absorption curve of the sample in Example 3 at 30°C and 3.5 MPa. The sample in Example 3 absorbed 3.18 wt.% hydrogen gas within 600 minutes at 30°C and 3.5 MPa hydrogen pressure. This is because the TiMn2 alloy first absorbs hydrogen and releases heat at room temperature, while hydrogen atoms dissociated from its surface rapidly diffuse through the phase boundary into the Mg-5Ni matrix, achieving synergistic hydrogen absorption.

[0056] 5. Cyclic stability test like Figure 5 The figure shows the cycle stability test curve for Example 3. After 20 hydrogen absorption and desorption cycles at 260°C, the hydrogen storage capacity of the Example 3 sample decreased from 5.24 wt.% to 5.18 wt.%, with a capacity retention rate as high as 98.9%, indicating that the 10 wt.% TiMn2 / Mg-5Ni hydrogen storage alloy has excellent cycle stability.

[0057] 6. Microscopic morphology analysis like Figure 6 The image shown is the SEM image and elemental energy spectrum of Example 3. The SEM image of the sample in Example 3 shows a grain size of 1–5 μm, and the elemental energy spectrum shows that Ti and Mn elements are uniformly distributed on the surface of the Mg-5Ni alloy. This uniform distribution facilitates sufficient interfacial contact between the TiMn2 catalytic phase and the Mg-Ni matrix, providing continuous diffusion channels for hydrogen atoms.

[0058] The present invention provides a Mg-Ni based hydrogen storage alloy with added TiMn2 and its preparation method. The process is simple and the cost is controllable. The prepared hydrogen storage alloy has excellent hydrogen absorption and desorption kinetics and cycle stability in the medium and low temperature range (30~220°C). It realizes the effective hydrogen absorption of magnesium-rich Mg-Ni hydrogen storage alloy under near room temperature conditions, which breaks through the limitation of insufficient low temperature hydrogen absorption performance of traditional Mg-Ni system. It can be widely used in vehicle hydrogen storage system, distributed hydrogen supply device, hydrogen power station and other scenarios, and has broad application prospects.

[0059] 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 Mg-Ni based hydrogen storage alloy with added TiMn2, characterized in that, The Mg-Ni-based hydrogen storage alloy is composed of a Mg-Ni alloy matrix and a TiMn2 catalytic phase dispersed therein; In the Mg-Ni alloy matrix, the mass percentage of Mg is 85~95wt.%, the mass percentage of Ni is 5~15wt.%, and all Ni elements exist in the form of Mg2Ni phase, while Mg elements exist in the forms of Mg phase and Mg2Ni phase. The TiMn2 catalyst phase accounts for 5~15 wt.% of the mass of the Mg-Ni based hydrogen storage alloy. The TiMn2 catalytic phase is TiMn2 alloy powder that has been activated to have room temperature hydrogen absorption activity. 2.The TiMn2-added Mg-Ni-based hydrogen storage alloy of claim 1, wherein, In the Mg-Ni alloy matrix, Mg accounts for 95 wt.% by mass and Ni accounts for 5 wt.% by mass. 3.The TiMn2-added Mg-Ni-based hydrogen storage alloy of claim 1, wherein, The TiMn2 catalyst phase accounts for 10 wt.% of the mass of the Mg-Ni based hydrogen storage alloy.

4. The TiMn2-added Mg-Ni-based hydrogen storage alloy according to any one of claims 1 to 3, characterized by, The TiMn2 catalytic phase is obtained through a pretreatment process including the following steps: Ti and Mn metals are mixed in an atomic ratio of 1:2, with Mn metal in excess of 3-5%, and TiMn2 alloy ingots are obtained by vacuum arc melting. The TiMn2 alloy ingot was vacuum annealed at 1000°C for 6 hours; The annealed TiMn2 alloy was subjected to hydrogen absorption and desorption activation treatment at 30°C and 4MPa hydrogen pressure for 3 to 5 times to obtain the TiMn2 alloy powder with room temperature hydrogen absorption activity.

5. The Mg-Ni based hydrogen storage alloy with added TiMn2 according to claim 4, characterized in that, After hydrogen absorption and desorption activation treatment, the TiMn2 catalytic phase forms a microcrack structure and a newly formed active surface.

6. A method for producing a Mg-Ni-based hydrogen storage alloy to which TiMn2 is added, characterized by, Includes the following steps: Preparation of TiMn2 alloy powder; Preparation of Mg-Ni alloy powder; The TiMn2 alloy powder and the Mg-Ni alloy powder were ball-milled in the presence of a grinding aid to obtain the Mg-Ni-based hydrogen storage alloy with added TiMn2. in, The TiMn2 alloy powder is a TiMn2 alloy powder that has been activated to have room temperature hydrogen absorption activity; In the Mg-Ni alloy powder, the mass percentage of Mg is 85-95 wt.%, and the mass percentage of Ni is 5-15 wt.%. The TiMn2 alloy powder accounts for 5-15 wt.% of the mass of the ball-milled composite raw material.

7. The production method according to claim 6, characterized by, The ball-to-material ratio of the ball milling process is 40-60:1, the ball milling speed is 400-450 rpm, the ball milling is intermittent, and the total ball milling time is 8-10 hours. Specifically, the intermittent ball milling is performed by alternating between 8-10 minutes of milling and 8-10 minutes of downtime.

8. The production method according to claim 6 or 7, characterized by, The grinding aid is tetrahydrofuran.

9. The preparation method according to claim 6, characterized in that, The TiMn2 alloy powder is prepared by the following steps: Ti and Mn metal elements are mixed in an atomic ratio of 1:2, with Mn metal element in excess of 3-5%. The mixture is then melted in a vacuum arc melting furnace under argon protection and an arc current of 140-160A. The melting process is repeated 3-5 times to obtain TiMn2 alloy ingots. The TiMn2 alloy ingot was vacuum annealed at 1000°C for 6 hours; The annealed TiMn2 alloy was subjected to hydrogen absorption and desorption activation treatment at 30°C and 4MPa hydrogen pressure for 3 to 5 times to obtain TiMn2 alloy powder with room temperature hydrogen absorption activity.

10. The method of claim 6, wherein, The Mg-Ni alloy powder is prepared by the following steps: Mg metal and Mg-30wt.%Ni master alloy are mixed according to the ratio of 95wt.% Mg and 5wt.% Ni, and then placed in a vacuum induction melting furnace and melted at 780~820°C under argon protection. After complete melting, the mixture is held at the temperature for 3~5 minutes and then cooled in the furnace to obtain a Mg-Ni alloy ingot. The Mg-Ni alloy ingot is then filed and crushed to obtain the Mg-Ni alloy powder.

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