A rare-earth-free Mg-Ni-Cu high-capacity hydrogen storage alloy and a preparation method thereof

Abstract

The application belongs to the technical field of new energy hydrogen storage materials, and particularly relates to a rare-earth-free Mg-Ni-Cu high-capacity hydrogen storage alloy and a preparation method thereof. 100‑x‑y Ni x Cu y , wherein 3.3<=x<=13.3, and y=3. The alloy contains Mg, Mg2Ni and Mg2Cu phase multi-phase eutectic structures. The alloy ingot is prepared from Mg, Mg-30Ni and Cu with a purity greater than 99% as raw materials under the protection of argon at a high-temperature smelting of 750 DEG C+ / -15 DEG C. The total hydrogen absorption amount of the alloy is greater than or equal to 5.3 wt.% under a hydrogen pressure of 5 MPa at 350 DEG C within 2 hours, the hydrogen absorption amount is greater than or equal to 3.89 wt.% within 2 minutes, and the reversible hydrogen absorption amount is greater than or equal to 4.48 wt.% within 20 minutes. The preparation process is simple, rare-earth elements are not needed, the cost is lower than that of a rare-earth-containing system, and the application is suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of new energy hydrogen storage materials technology, specifically relating to a rare earth-free Mg-Ni-Cu high-capacity hydrogen storage alloy and its preparation method. Background Technology

[0002] Hydrogen energy, as a clean energy source, boasts advantages such as high energy density and zero pollution. Solid-state hydrogen storage technology, with its high hydrogen storage density, high safety, and low cost, has become an important development direction for hydrogen energy storage. With the deepening research into solid-state hydrogen storage technology, materials based on magnesium and magnesium-based alloys exhibit excellent hydrogen storage performance and are considered to have great potential in solid-state hydrogen storage.

[0003] Among magnesium-based solid-state hydrogen storage materials, the Mg-Ni hydrogen storage system is the most representative. It relies on Mg, Ni, or other metals added to these two metals to form an alloy. These alloys promote the adsorption and dissociation of hydrogen molecules. During hydrogen absorption, hydrogen molecules decompose into hydrogen atoms on the alloy surface. These hydrogen atoms diffuse into the alloy lattice and interact with magnesium and nickel atoms to form hydrides, thus improving the hydrogen absorption performance of the material. Simultaneously, the size of the catalytic phase formed by the alloy directly affects the hydrogen storage performance of the material. Smaller catalytic phases can better promote the binding of hydrogen atoms with the material, which is more conducive to hydrogen adsorption and desorption. However, the hydrogen storage capacity of traditional Mg2Ni alloys is still lower than the theoretical value of pure Mg, and the hydrogen adsorption and desorption kinetics need further improvement. To address these issues, researchers have found that partially replacing Ni with Cu can effectively improve the hydrogen storage performance of Mg-Ni alloys. The addition of Cu can promote the formation of the Mg2Ni phase and cause lattice expansion and micro-strain, thereby enhancing the catalytic effect of the alloy, lengthening the H-Mg2(Ni,Cu) bond length, and increasing the cracking tendency of alloy particles. These effects are all beneficial to hydrogen adsorption and desorption reactions.

[0004] Currently, the main methods for preparing Mg-Ni-Cu hydrogen storage alloys include mechanical ball milling, induction melting, and hydrogenation combustion synthesis. Among these, mechanical ball milling offers advantages such as simplicity and the ability to achieve micro-refinement and alloying, but its drawbacks are also significant. First, the ball milling process is energy-intensive, especially since a uniform nanostructure is only achieved after prolonged milling, leading to increased costs. Second, impurities, such as abrasive particles from the grinding media, are easily introduced during ball milling, potentially contaminating the hydrogen storage material and affecting its hydrogen storage performance and cycle stability. Furthermore, ball milling easily leads to material oxidation, especially in reactive metals like magnesium alloys, increasing safety risks and the difficulty of subsequent processing. These factors make large-scale industrial production of the ball milling method difficult, resulting in poor batch-to-batch consistency and limiting its application in the preparation of commercial hydrogen storage materials.

[0005] Therefore, developing a rare earth-free, high-capacity Mg-Ni-Cu hydrogen storage alloy with a simple and controllable preparation process suitable for industrial production and its preparation method is of great significance for promoting the application of magnesium-based solid hydrogen storage materials. Summary of the Invention

[0006] To address the challenge of achieving uniform Cu distribution and obtaining excellent eutectic structure in Mg-Ni alloys under normal pressure smelting conditions, thereby effectively improving the hydrogen absorption and desorption kinetics and hydrogen storage performance of magnesium-based hydrogen storage alloys, this invention provides an easily activated, high-capacity, rare-earth-free Mg-Ni-Cu hydrogen storage alloy and its preparation method.

[0007] Specifically, the present invention provides a Mg-Ni-Cu hydrogen storage alloy, wherein the chemical composition of the Mg-Ni-Cu alloy is Mg 100-x-y Ni x Cu y , where 3.3≤x≤13.3, y=3.

[0008] Furthermore, in the Mg-Ni-Cu hydrogen storage alloy, when x=13.3, the as-cast microstructure of the Mg-Ni-Cu hydrogen storage alloy includes a Mg-Mg2Ni-Mg2Cu three-phase eutectic structure.

[0009] Furthermore, in the Mg-Ni-Cu hydrogen storage alloy, when x=3.3, the as-cast alloy microstructure of the Mg-Ni-Cu hydrogen storage alloy consists of a network Mg-Mg2Ni eutectic structure and a plum blossom-shaped Mg phase.

[0010] Furthermore, the Mg-Ni-Cu hydrogen storage alloy exhibits a reversible hydrogen absorption capacity of ≥4.48 wt.% within 20 minutes at 350°C and 5 MPa hydrogen pressure.

[0011] Furthermore, the Mg-Ni-Cu hydrogen storage alloy has a total hydrogen absorption capacity of ≥5.3wt.% at 350℃ and 5MPa hydrogen pressure.

[0012] A method for preparing the Mg-Ni-Cu hydrogen storage alloy of the present invention is also provided, comprising the following steps:

[0013] Mg, Mg-30Ni and Cu were placed in a graphite crucible and melted at a high temperature of 750℃±15℃ under an inert gas atmosphere to obtain Mg-Ni-Cu hydrogen storage alloy ingots.

[0014] Furthermore, in the method, the inert gas is argon, and the gas flow rate of the argon is 5-8 L / min; the high-temperature melting time is 1 hour.

[0015] Furthermore, in the method, the melt is subjected to intermittent mechanical stirring during the high-temperature melting stage.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The present invention obtains a Mg-Ni-Cu hydrogen storage alloy by precisely controlling the ratio of Ni to Cu in the alloy. The chemical composition of the alloy is Mg 100-x-y Ni x Cu y With the formula 3.3≤x≤13.3 and y=3, this Mg-Ni-Cu hydrogen storage alloy achieves synergistic optimization of high hydrogen storage capacity and rapid hydrogen absorption kinetics without the addition of rare earth elements. At 350℃ and 5MPa hydrogen pressure, the total hydrogen absorption capacity of this Mg-Ni-Cu hydrogen storage alloy can reach 5.3wt.% to 6.05wt.% within 2 hours, significantly higher than traditional Mg2Ni alloys and most magnesium-based hydrogen storage systems containing rare earth or transition metals. This Mg-Ni-Cu hydrogen storage alloy can absorb 67.5% to 80% of the total hydrogen absorption capacity within 2 minutes, with a maximum absorption capacity of 4.62wt.%. This characteristic greatly improves the hydrogen charging efficiency of the hydrogen storage system.

[0017] (2) By controlling the Ni content (3.3≤x≤13.3), this invention constructs different types of multiphase eutectic structures in the as-cast microstructure. These fine and uniformly distributed eutectic structures, especially the three-phase eutectic formed when x=13.3, provide a large number of active interfaces and fast channels for the dissociation of hydrogen molecules and the diffusion of hydrogen atoms, thereby significantly improving the hydrogen absorption and desorption kinetics of the alloy. This microstructure design is the key to achieving excellent performance under normal pressure melting conditions in this invention.

[0018] (3) This invention eliminates the drawbacks of traditional mechanical ball milling methods, such as high energy consumption, easy introduction of impurities and oxidation, and poor batch consistency. It also eliminates the need for expensive rare earth elements (La, Ce, Nd, Y, etc.) or complex hydrogenation combustion synthesis processes. It only requires a one-step atmospheric pressure melting method, which involves high-temperature melting at 750℃±15℃ for 1 hour under argon protection to obtain high-performance Mg-Ni-Cu hydrogen storage alloy. This preparation method has a short process, low equipment requirements, and low raw material costs, making it suitable for large-scale industrial production.

[0019] In summary, this invention successfully solves the technical challenge of obtaining high-performance Mg-Ni-Cu hydrogen storage alloys under simple smelting conditions, and provides a comprehensive solution that combines high capacity, fast kinetics, long lifespan, low cost, and ease of preparation. Attached Figure Description

[0020] Figure 1 This is the ternary phase diagram of the Mg-Ni-Cu alloy.

[0021] Figure 2 Mg 83.7 Ni 13.3SEM image of Cu3 alloy.

[0022] Figure 3 Mg 88.7 Ni 8.3 SEM image of Cu3 alloy.

[0023] Figure 4 Mg 93.7 Ni 3.3 SEM image of Cu3 alloy.

[0024] Figure 5 Mg 83.7 Ni 13.3 Cu3, Mg 88.7 Ni 8.3 Cu3, Mg 93.7 Ni 3.3 XRD pattern of Cu3 particles.

[0025] Figure 6 Mg 83.7 Ni 13.3 Cu3, Mg 88.7 Ni 8.3 Cu3, Mg 93.7 Ni 3.3 XRD pattern of Cu3 after hydrogenation.

[0026] Figure 7 Mg 83.7 Ni 13.3 Hydrogen absorption kinetics curve of Cu3 alloy at 350℃ and 5MPa.

[0027] Figure 8 Mg 88.7 Ni 8.3 Hydrogen absorption kinetics curve of Cu3 alloy at 350℃ and 5MPa.

[0028] Figure 9 Mg 93.7 Ni 3.3 Hydrogen absorption kinetics curve of Cu3 alloy at 350℃ and 5MPa.

[0029] Figure 10 Mg 83.7 Ni 13.3 EDS spectrum of Cu3.

[0030] Figure 11 Mg 88.7 Ni 8.3 EDS spectrum of Cu3.

[0031] Figure 12 For Mg 93.7 Ni 3.3EDS spectrum of Cu3. Detailed Implementation

[0032] The technical solution of the present invention will be described below with reference to the embodiments. However, the present invention is not limited to the following embodiments.

[0033] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0034] Unless otherwise specified, the experimental and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0035] The purity of Mg, Mg-30Ni, and Cu used in this invention is greater than 99%.

[0036] Mg-30Ni is a Mg-Ni alloy with a Mg mass fraction of 70% and a Ni mass fraction of 30%.

[0037] Example 1 According to Mg 100-x-y Ni x Cu y The chemical composition formula is given in this embodiment, with x=13.3 and y=3, and the target component is Mg. 83.7 Ni 13.3 Cu3; Based on the target composition, the raw materials Mg, Mg-30Ni, and Cu were accurately calculated and weighed. Mg, Mg-30Ni, and Cu were placed in a graphite crucible, and argon gas was continuously introduced through a gas inlet pipe at a flow rate of 5 L / min. The atmosphere was maintained throughout the process. A resistance furnace was used for high-temperature melting at 750℃±15℃ for 1 hour. During the high-temperature melting stage, the melt was intermittently mechanically stirred at a speed of 70 r / min, with each stirring cycle lasting 3 minutes and followed by a 2-minute resting period, until the liquid surface was bright silvery with no churning and no unmelted metal particles floated to the surface. Mg was then obtained. 83.7 Ni 13.3 Cu3 alloy ingots. After ingot forming, ICP composition analysis was performed, with strict control of elemental composition deviations ≤0.5%. The Mg... 83.7 Ni 13.3 The ternary phase diagram of Cu3 alloy ingots is as follows: Figure 1 As shown.

[0038] Example 2 According to Mg 100-x-y Ni x Cu y The chemical composition formula is given in this embodiment, with x=8.3 and y=3, and the target component is Mg. 88.7Ni 8.3 Cu3; Based on the target composition, the raw materials Mg, Mg-30Ni, and Cu were accurately calculated and weighed. Mg, Mg-30Ni, and Cu were placed in a graphite crucible, and argon gas was continuously introduced through a gas inlet pipe at a flow rate of 7 L / min. The atmosphere was maintained throughout the process. A resistance furnace was used for high-temperature melting at 750℃±15℃ for 1 hour. During the high-temperature melting stage, the melt was intermittently mechanically stirred at a speed of 90 r / min, with each stirring cycle lasting 5 minutes and followed by a 4-minute resting period, until the liquid surface was bright silvery with no churning and no unmelted metal particles floating to the surface. Mg was thus obtained. 88.7 Ni 8.3 Cu3 alloy ingots. After ingot forming, ICP composition analysis is performed, and the deviation of each element composition is strictly controlled to be ≤0.5%.

[0039] Example 3 According to Mg 100-x-y Ni x Cu y The chemical composition formula is given in this embodiment, with x=3.3 and y=3, and the target component is Mg. 93.7 Ni 3.3 Cu3; Based on the target composition, the raw materials Mg, Mg-30Ni, and Cu were accurately calculated and weighed. Mg, Mg-30Ni, and Cu were placed in a graphite crucible, and argon gas was continuously introduced through a gas inlet pipe at a flow rate of 8 L / min. The atmosphere was maintained throughout the process. A resistance furnace was used for high-temperature melting at 750℃±15℃ for 1 hour. During the high-temperature melting stage, the melt was intermittently mechanically stirred at a speed of 80 r / min, with each stirring cycle lasting 4 minutes and followed by a 3-minute resting period, until the liquid surface was bright silver with no churning and no unmelted metal particles floated to the surface. Mg was thus obtained. 93.7 Ni 3.3 Cu3 alloy ingots. After ingot forming, ICP composition analysis is performed, and the deviation of each element composition is strictly controlled to be ≤0.5%.

[0040] Test Example 1 This test example uses three groups of MgNiCu hydrogen storage alloys with different nickel content gradients from Examples 1 to 3 as samples. Through SEM microstructure characterization, EDS micro-area composition analysis, XRD phase testing, and hydrogen storage kinetic performance testing, the influence of nickel content gradient on the alloy microstructure, phase composition, and hydrogen storage performance is investigated.

[0041] Depend on Figure 2 It can be seen that Mg 83.7 Ni 13.3 The as-cast microstructure of Cu3 alloy exhibits three contrasts: white, black, and dark gray. EDS energy dispersive spectroscopy analysis can reveal the presence of Mg. 83.7 Ni 13.3The as-cast Cu3 alloy consists of a white, elongated, blocky Mg-Mg2Ni-Mg2Cu three-phase eutectic structure, a fine Mg-Mg2Ni two-phase eutectic structure, and a black Mg matrix.

[0042] Figure 3 Mg 88.7 Ni 8.3 The microstructure of the as-cast Cu3 alloy, as determined by EDS energy dispersive spectroscopy analysis, shows that the alloy contains a large amount of fine Mg-Mg2Ni eutectic structure and a very small number of plum blossom-shaped Mg phases.

[0043] Figure 4 Mg 93.7 Ni 3.3 Microstructure of Cu3 as-cast alloy, EDS energy dispersive spectroscopy analysis showed that Mg 93.7 Ni 3.3 The as-cast Cu3 alloy consists of a large amount of network Mg-Mg2Ni eutectic structure and plum blossom-shaped Mg phase.

[0044] Depend on Figure 5 , Figure 6 It can be seen that as-cast Mg 83.7 Ni 11.3 Cu3, Mg 88.7 Ni 8.3 Cu3, Mg 93.7 Ni 3.3 The Cu3 triad alloy consists only of three phases: Mg, Mg2Ni, and Mg2Cu. With increasing Ni content, the intensity of the Mg diffraction peak in the matrix decreases, while the precipitation of Mg2Ni and Mg2Cu increases simultaneously. After hydrogen absorption, a large amount of elemental Mg is converted into the hydrogen storage phase MgH2, and the diffraction signal of Mg2NiH4 becomes stronger with increasing Ni content. Furthermore, neither set of spectra shows any other extraneous peaks, indicating good atmosphere protection during smelting and hydrogenation.

[0045] Figure 7 Mg 83.7 Ni 13.3 The hydrogen absorption kinetics curve of Cu3 shows that the total hydrogen absorption of this alloy can reach 5.3 wt.% within 2 hours under 350℃ and 5 MPa hydrogen pressure, and 4.4 wt.% within 2 minutes, reaching 80% of the total hydrogen absorption. The alloy exhibits good hydrogen absorption and desorption cycle performance at 350℃, with a reversible hydrogen absorption of 4.67 wt.% within 20 minutes.

[0046] Figure 8 Mg 88.7 Ni 8.3The hydrogen absorption kinetics curve of Cu3 shows that the total hydrogen absorption of this alloy can reach 5.76 wt.% within 2 hours under 350℃ and 5 MPa hydrogen pressure, and 3.89 wt.% within 2 minutes, reaching 67.5% of the total hydrogen absorption. The alloy exhibits good hydrogen absorption and desorption cycle performance at 350℃, with a reversible hydrogen absorption of 5.14 wt.% within 20 minutes.

[0047] Figure 9 Mg 93.7 Ni 3.3 The hydrogen absorption kinetics curve of Cu3 shows that the total hydrogen absorption of this alloy can reach 6.05 wt.% within 2 hours under 350℃ and 5 MPa hydrogen pressure, and 4.62 wt.% within 2 minutes, reaching 67.5% of the total hydrogen absorption. The alloy exhibits good hydrogen absorption and desorption cycle performance at 350℃, with a reversible hydrogen absorption of 4.48 wt.% within 20 minutes.

[0048] Figure 10 Mg 83.7 Ni 13.3 The EDS spectrum of Cu3 shows a large number of parallel or interlaced elongated, needle-like, and plate-like secondary phases in the matrix, with lengths reaching several micrometers. The dark bands are clearly enriched in Ni and Cu, while the Mg signal is relatively weak, indicating that it is an intermetallic compound enriched in Ni and Cu; the matrix is ​​dominated by Mg.

[0049] Figure 11 Mg 88.7 Ni 8.3 The EDS spectrum of Cu3 shows a relatively regular elongated, framework-like, and locally curved second phase, with lengths reaching several micrometers. Some of these phases form a continuous network, exhibiting clear directional growth characteristics. EDS surface scanning indicates that the elongated and framework regions are significantly enriched in Ni and Cu, while the Mg signal is weakened; the surrounding regions are dominated by a Mg matrix. Cu is generally distributed along the Ni-enriched phase.

[0050] Figure 12 Mg 93.7 Ni 3.3 The EDS spectrum of Cu3 shows that the eutectic phase is predominantly elliptical, with particle sizes ranging from several hundred nanometers to 1 micrometer. Some particles are interconnected, resulting in a relatively dispersed overall distribution. The EDS results indicate that Ni and Cu are enriched simultaneously in the particle regions, while Mg is mainly distributed in the interparticle matrix, exhibiting a clear elemental partitioning characteristic.

[0051] Comparative Example 1 The alloy chemical formula of this comparative example is Mg. 3.497 Ni 0.170 La 0.032 Y 0.006The raw materials used were elemental Mg, Ni, La, and Y with a purity of 99.9%. 45.0132 g of Mg, 5.1112 g of Ni, 3.7875 g of La, and 0.2525 g of Y were weighed, with Mg increased by 5% based on burn-off, and La and Y each increased by 1%. After grinding to remove the oxide film and preheating and drying, the raw materials were placed in a crucible, heated to 500℃ and held for 3 min, and the air was replaced with 99.9% SF6. The temperature was then increased to 1050℃ and held for 3 min, followed by 1150℃ and held for 10 min. Finally, the mixture was cast to obtain an alloy ingot.

[0052] Comparative Example 2 This comparative example, composed of 80 wt.% Mg, 15 wt.% Al, and 5 wt.% Ni, has a maximum hydrogen storage capacity of 4.36 wt.%. La, Mg, Ni, Co, and Al metal powders were weighed according to stoichiometric ratios and induction melted at 1500 °C for 10 min in 0.2 MPa argon atmosphere. After casting, the mixture was annealed at 1173 K for 8 h. The alloy was crushed and sieved into 300-mesh powder. 2.0 g of the powder was added to 25 mL of 0.01 mol / L H₂SO₄ and activated by stirring at 25 °C for 1 min under nitrogen protection. The activated powder was then poured into a solution prepared from 0.0789 g CuSO₄·5H₂O and 50 mL of deionized water and reacted at 25 °C and 30 MHz ultrasonically for 2 min. After filtration, the alloy was washed three times each with deionized water and ethanol, and then dried under vacuum at 30°C for 4 hours to obtain an alloy with approximately 1 wt.% copper coating. Increasing the amount of CuSO4·5H2O can yield a copper coating layer of 3-9 wt.%.

[0053] Comparative Example 3 Graphene-reinforced Mg-Ni hydrogen storage alloy powder was prepared. The graphene nanosheets contained no more than 10 layers, the Mg-Ni master alloy contained 35 wt.% Ni, and the Mg block had a purity of 99%. The mass ratio of graphene nanosheets, Mg-Ni master alloy, and Mg block was 2:95:8, and the master alloy contained 35 wt.% Ni. The Mg-Ni master alloy and Mg block were ultrasonically cleaned at 40 kHz and 700 W for 15 min, placed in an alumina crucible, heated to 800℃ at 8℃ / min and held for 10 min in argon atmosphere, and then cooled in the furnace. This heating and cooling process was repeated 2-3 times. Subsequently, the pre-formed alloy was heated to 830℃ and rapidly quenched at 2000 r / min, with a cooling rate of approximately 10^6℃ / min, to form an amorphous ribbon with a thickness of approximately 80 μm. Finally, it was ball-milled in an argon-sealed ball mill jar with GCr15 steel balls at a ball-to-material ratio of 20:1 at 1200 r / min for 6 h to obtain a 300 nm graphene-Mg-Ni composite powder.

[0054] Comparative Example 4 This comparative example provides a hydrogen storage alloy with a Mg content of 90-95 at.%, a Ni content of 3-6 at.%, a Y content of 1-2 at.%, and a Nd content of 1-2 at.%, with the total Y and Nd content not exceeding 3 at.%. Ingots of Mg, Ni, Y, and Nd are used. The alloy is prepared by induction melting at 675-750℃ for 3-5 cycles, followed by furnace cooling to 400℃ at a rate of 3℃ / min, and then air-cooling to room temperature. The ingot is descaled, mechanically crushed in air, and sieved through a 200-mesh sieve. The powder is loaded into a closed reactor, purged three times with argon gas, and then subjected to hydrogen absorption at 5 MPa and 350℃ for 4 h to allow in-situ decomposition of the alloy. Finally, hydrogen is released under vacuum at 350℃ for 0.5 h to obtain a hydrogen storage alloy containing Mg, Mg2Ni, and YH. x and NdH x A composite hydrogen storage material. Other components include Mg. 92 Ni5Y1Nd2, Mg 93 Ni5Y2 and Mg 91 Ni5Y2Nd2.

[0055] Comparative Example 5 This comparative example provides a chemical composition of Mg. 93 Ni 6.6 Si 0.4 Hydrogen storage alloys. Raw materials include pure Mg, Mg-30Ni master alloy, and Mg-15Si master alloy. Based on Mg... 93 Ni 6.6 Si 0.4 The target composition was prepared by mixing raw materials and adjusting the amount of Ni and Si lost during burning according to actual conditions. Mg blocks were first melted in a resistance furnace, followed by the sequential addition of Mg-15Si and Mg-30Ni. After removing impurities and allowing the mixture to stand, it was poured into a water-cooled mold. The as-cast alloy was mechanically crushed into particles of tens of micrometers and then ball-milled for 14 hours in an argon-sealed ball mill with stainless steel balls at a ball-to-material ratio of 30:1 and a speed of 280 r / min to obtain Mg-Ni-Si hydrogen storage alloy powder.

[0056] Comparative Example 6 This comparative example provides a hydrogen storage alloy with a chemical composition of Mg-15Ni-0.1Cu. Pure Mg, pure Ni, and pure Cu sheets were used. 255 kg of Mg, 45 kg of Ni, and 0.3 kg of Cu were weighed. The Ni and Cu sheets were preheated at 200 °C for 3 h. Mg was melted in a protective atmosphere of 0.1 vol.% SF6 and 99.9 vol.% CO2. After the melt reached 740 °C, Ni and Cu were added. After complete melting, the mixture was stirred, surface impurities were removed, and the mixture was allowed to stand at 720 °C. After standing for 20 min, the mixture was poured into ingots of approximately 5 kg / ingot at 670 °C within 60 min using a transfer pump. The ingots were then cut and crushed to less than 80 mesh.

[0057] Comparative Example 7 This comparative example provides a Mg2Ni-type ternary Mg-Ni-Cu reversible hydrogen storage material, using Mg, Ni, and Cu powders with a particle size of not less than 200 mesh and a purity of not less than 99.5%. The target alloy is Mg. 20 Ni 10 x Cu x (0 < x ≤ 1.2), of which Mg accounts for 66.7 at.%, and Ni and Cu together account for 33.3 at.%. First, Ni and Cu powders are weighed according to the proportion, and wet-milled in industrial alcohol at a ball-to-powder ratio of 20:1 and 150-300 r / min for 30-50 h, then dried to obtain Ni(Cu) solid solution powder; then mixed with Mg powder according to the atomic ratio, ball-milled at a ball-to-powder ratio of 20:1 and 300 r / min for 1 h, and vacuum sintered at 500℃ for 20 h. Mg is then obtained. 20 Ni 9.5 Cu 0.5 and Mg 20 Ni 9.0 Cu 1.0 alloy.

[0058] Comparative Example 8 This comparative example provides a high-capacity Mg-Ni-Cu-La hydrogen storage alloy, using Mg ingots with a purity of not less than 99.94%, electrolytic Ni blocks with a purity of 99.96%, Cu blocks with a purity of 99.9%, and La blocks with a purity of 99.5%. The alloy is Mg-13Ni-7Cu-3La. After weighing the materials according to the target ratio, Ni and Cu layers, small Mg layers, La layers, and large Mg layers are placed sequentially from bottom to top in an alumina crucible. The medium-frequency induction furnace is evacuated to below 0.1 Pa, then filled with approximately 350 Pa of argon gas for protection. Induction melting is performed until the raw materials are completely melted. After solidification, the molten liquid yields the as-cast Mg-13Ni-7Cu-3La hydrogen storage alloy.

[0059] Test Example 2 This test example uses MgNiCu hydrogen storage alloys with different nickel content gradients prepared in Examples 1-3 as samples, and hydrogen storage alloys prepared in Comparative Examples 1-8 as samples to test the hydrogen storage performance of different hydrogen storage alloys. The test results are shown in Table 1.

[0060] Table 1. Test results of hydrogen storage performance of different hydrogen storage alloys

[0061] As shown in Table 1, the maximum hydrogen storage capacity of the MgNiCu hydrogen storage alloys prepared in Examples 1-3 of this invention is 5.3 wt.%, 5.76 wt.%, and 6.05 wt.%, respectively, showing a progressively increasing trend with optimization of nickel content, demonstrating a significant overall advantage in hydrogen storage capacity. Compared with Comparative Examples 1, 2, 3, 6, 7, and 8 (maximum hydrogen storage capacity 3.58-5.1 wt.%), the maximum hydrogen storage capacity of the alloys in the examples of this application is significantly higher, proving that the MgNiCu alloys modified by nickel content gradient can effectively improve the saturated hydrogen storage capacity of the alloy, which is significantly better than the traditional unmodified hydrogen storage alloy system.

[0062] The MgNiCu-based hydrogen storage alloys prepared in Examples 1-3 of this invention combine high hydrogen storage capacity with excellent rapid hydrogen absorption kinetics. Compared with the hydrogen storage alloys provided in the comparative examples, they have higher hydrogen storage capacity, faster hydrogen absorption response speed, and significantly improved overall hydrogen storage performance.

[0063] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A Mg-Ni-Cu hydrogen storage alloy, characterized in that, The chemical composition of the Mg-Ni-Cu alloy is Mg 100-x- y Ni x Cu y , where 3.3≤x≤13.3, y=3.

2. The Mg-Ni-Cu hydrogen storage alloy according to claim 1, characterized in that, When x=13.3, the as-cast microstructure of the Mg-Ni-Cu hydrogen storage alloy contains a Mg-Mg2Ni-Mg2Cu three-phase eutectic structure.

3. The Mg-Ni-Cu hydrogen storage alloy according to claim 1, characterized in that, When x=3.3, the as-cast alloy microstructure of the Mg-Ni-Cu hydrogen storage alloy consists of a network Mg-Mg2Ni eutectic structure and a plum blossom-shaped Mg phase.

4. The Mg-Ni-Cu hydrogen storage alloy according to claim 1, characterized in that, At 350℃ and 5MPa hydrogen pressure, the reversible hydrogen absorption capacity is ≥4.48wt.% within 20 minutes.

5. The Mg-Ni-Cu hydrogen storage alloy according to claim 1, characterized in that, At 350℃ and 5MPa hydrogen pressure, the total hydrogen absorption is ≥5.3wt.%.

6. A method for preparing the Mg-Ni-Cu hydrogen storage alloy according to any one of claims 1-5, characterized in that, Includes the following steps: Mg, Mg-30Ni and Cu were placed in a graphite crucible and melted at a high temperature of 750℃±15℃ under an inert gas atmosphere to obtain Mg-Ni-Cu hydrogen storage alloy ingots.

7. The method according to claim 6, characterized in that, The inert gas is argon, and the argon gas flow rate is 5-8 L / min; the high-temperature melting time is 1 hour.

8. The method according to claim 7, characterized in that, During the high-temperature smelting stage, the melt is subjected to intermittent mechanical stirring.

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