A rare earth-rich high-capacity vanadium-based solid-solution type hydrogen storage alloy and a preparation method thereof

Abstract

The application relates to the technical field of hydrogen storage alloys, and discloses a rare earth-rich high-capacity vanadium-based solid solution type hydrogen storage alloy and a preparation method thereof. x Ti y Cr z A m B n wherein 0.6<=x<=0.8, 0.067<=y<=0.133, 0.103<=z<=0.247, 0.01<=m<=0.04, 5<=n<=7, A is one or more of Fe, Al, Mn, Mo, Ni and Co, B is rare earth Y, Ce, La or an alloy thereof, and the rare earth Y, Ce, La or the alloy thereof is added in excess of the CrV intermediate alloy O content. In the design of the alloy composition, the generation of Ti-rich phases in the crystal and at the grain boundary can be effectively inhibited by adding more rare earth elements, and the reversible hydrogen storage capacity is improved; the prepared hydrogen storage alloy has good cycle stability. In the preparation process, the cooling rate after accelerated heat treatment is used to maintain the microstructure of the alloy at high temperature, and the harmful Ti-rich phase is inhibited from being precipitated along the grain boundary again.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage alloy technology, specifically to a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy and its preparation method. Background Technology

[0002] Sustainable development in the energy sector remains a core global concern. Hydrogen, as a highly efficient and clean energy source, holds promise for accelerating the transition from an industrial society to a low-carbon economy. Under standard conditions (273 K and 1 atm), hydrogen has an extremely low density of only 0.0899 g / L, making its storage and transportation extremely difficult. Solid-state hydrogen storage materials can store hydrogen in atomic form within the interstitial spaces of the material's crystal lattice at relatively low pressures, significantly improving volumetric storage density and safety compared to high-pressure gaseous hydrogen.

[0003] In solid-state hydrogen storage materials, vanadium-based solid solution hydrogen storage alloys exhibit high reversible hydrogen storage capacity at room temperature and relatively low pressure, with a reversible hydrogen storage capacity exceeding 2.4 wt.% (Journal of Power Sources, 2025, 640: 236807). Therefore, vanadium-based alloys show great application potential in both mobile and stationary hydrogen storage. However, the cost of pure vanadium is approximately $200 / kg, resulting in high costs for preparing vanadium-based alloys using pure vanadium. Studies have shown that using lower-cost (~$20 / kg) vanadium master alloys (such as FeV80) to replace pure vanadium can significantly reduce the preparation cost of vanadium-based alloys (Rare Metals, 2024, 43(12):6201-6232), providing a method for the large-scale application of vanadium-based hydrogen storage alloys. 80 The master alloy contains approximately 80 wt.% V, 15 wt.% Fe, and the remaining 5 wt.% is mainly composed of impurity elements such as O, Al, and Si. For example, Yan et al. improved the FeV... 80 Adding 3wt.% Ce, V was developed. 30 Ti 32 Cr 32Fe6 alloy (at.%) was analyzed, and the formation of C14 Laves and CeO phases was confirmed. Subsequent annealing treatment was found to eliminate the Laves phase (Journal of powersources, 2007, 164(2): 799-802). Okada et al. and Yang et al. found the presence of C15 Laves phase in low-V alloys (V≤20 at.%), and heat treatment could eliminate some of it (Journal of alloys and compounds, 330, 511-516. International Journal of Hydrogen Energy, 2023, 48(69):26870-26880.). However, some studies have shown that extending the heat treatment time to 20h may increase the C14 Laves phase in the alloy (Nano-MicroLetters, 17(1), 1-30.). Ulmer U et al. systematically used FeV 80 Replaced V 40 Fe8Ti 26 Cr 26 For alloys with 0–90 wt.% V, the reversible hydrogen storage capacity decreased from 2.2 wt.% to 1.7 wt.% (Journal of Alloys and Compounds, 2015, 648: 1024–1030), primarily due to the higher FeV content. 80 The addition of [a substance] leads to the formation of a large amount of titanium-rich phases, which do not possess good hydrogen absorption and desorption properties. Ulmer et al. prepared V using pure V raw materials with high and low oxygen contents. 40 Fe8Ti 26 Cr 26 In an alloy prepared from high-oxygen raw materials, an α-Ti phase was found. This study suggests that the formation of the α-Ti phase originates from the deoxidation reaction of Ti in a high-oxygen environment, which reduces the Ti concentration in the original BCC matrix by approximately 4 at.% (International Journal of Hydrogen Energy, 2004, 29(13):1377-1381.). Huang et al. prepared V using pure alloys. 70 Ti 10 Cr 20 The alloy was found to contain a titanium-rich TiV phase, and the content of this Ti-rich phase was affected by the V content and the Ti / Cr ratio (Energy & Fuels, 38(13), 12121-12128). Li et al. added 3 wt.% Y and Zr elements to FeV before alloy smelting. 80 The raw materials were pre-refined, and the pre-refined FeV was used. 80Ti was prepared 27 Cr 27 (FeV 80 +Y) 46 The reversible hydrogen storage capacity of the alloy increased from 2.0 wt.% to 2.3 wt.%, possibly because 3 wt.% Y element suppressed the formation of the Ti-rich phase (Rare Metals, 2025, 44: 4137-4148). Zhang et al. further improved the FeV alloy by adding 3 wt.% Y, La, Ce, Nb and Ga elements. 80 The raw materials were pre-refined to prepare Ti 31 Cr 35 (FeV 80 -RE) 34 Alloy (Journal of RareEarths, 2025). The results show that Ce and Y elements have the best impurity removal effect, and the alloy achieves a reversible hydrogen storage capacity of 2.28 wt.%.

[0004] The above studies indicate that the addition of small amounts of rare earth elements can remove some Si and O impurities, thereby improving the reversible hydrogen storage capacity to a certain extent. However, vanadium-based hydrogen storage alloys prepared using intermediate alloys generally exhibit a large number of Ti-rich phases (Rare Metals, 2025, 44:4137-4148, Journal of Rare Earths, 2025). There are various types of Ti-rich phases, including the hexagonal (HCP) C14 Laves phase and α-Ti phase, and the body-centered cubic (BCC) C15 Laves phase and TiV phase. Similar to the α-Ti phase, the TiV phase may be formed due to the reaction of Ti with residual O elements. The formation of Ti-rich phases leads to the loss of Ti elements in the main phase of the alloy, reducing the cell volume and resulting in a lower overall reversible hydrogen storage capacity. Summary of the Invention

[0005] The present invention aims to provide a high-capacity vanadium-based solid solution hydrogen storage alloy rich in rare earth elements and its preparation method, so as to solve the problem of low reversible capacity caused by the presence of titanium-rich phase in the prior art, so that the reversible capacity at 50°C reaches more than 2.6 wt.%, while ensuring the low cost characteristics and good cycle stability of the hydrogen storage alloy.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy, with the chemical formula V2... x Ti y Cr z A m B nWhere: 0.6≤x≤0.8, 0.067≤y≤0.133, 0.103≤z≤0.247, 0.01≤m≤0.04, 5≤n≤7, A is one or more of Fe, Al, Mn, Mo, Ni, and Co, and B is rare earth Y, Ce, La, or their alloys, wherein the amount of rare earth Y, Ce, La, or their alloys added is based on the excess content of O in the CrV master alloy.

[0007] Preferably, as an improvement, the molar ratio of the addition of rare earth elements Y, Ce, La or their alloys to the O content of the CrV master alloy is >0.5.

[0008] Preferably, as an improvement, the molar ratio of the addition of rare earth elements Y, Ce, La or their alloys to the O content of the CrV master alloy is 0.65 to 0.86.

[0009] Preferably, as an improvement, a method for preparing a rare-earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy includes the following steps:

[0010] S1. Prepare the intermediate alloy: The intermediate alloy is a CrV intermediate alloy;

[0011] S2. Smelting: Mix CrV master alloy, Ti, Fe, Cr and rare earth elements, and smelt to obtain cast alloy ingot; the molar ratio of rare earth addition to O content in CrV master alloy is 0.65~0.86.

[0012] S3. Heat treatment: Heat treatment is performed on the cast alloy ingot to obtain vanadium-based hydrogen storage alloy.

[0013] Preferably, as an improvement, in step S1, the raw materials for preparing the CrV master alloy include V2O5, Al, CaO, slagging agent and Cr, the molar ratio of V2O5 to Al is 3:9.8~10, the amount of CaO and slagging agent added is 12~15% of the total mass of the V2O5 and Al mixture, and the amount of Cr added is 0.5-2.0% of the total mass of the V2O5 and Al mixture.

[0014] Preferably, as an improvement, in step S2, the melting temperature is 1900~2200℃ and the melting time is 1~10min.

[0015] Preferably, as an improvement, in step S2, the melting process is carried out in an argon atmosphere with an argon pressure of 0.07-0.08 MPa.

[0016] Preferably, as an improvement, in step S2, a melting current plus electromagnetic stirring method is adopted. After the alloy ingot is completely melted and clarified, the electromagnetic stirring is turned on. The melting current is 270~300A, the rotation speed is 5~15 rpm, and the number of melting times is 3~5 times.

[0017] Preferably, as an improvement, in step S3, the heat treatment temperature is 1300~1400℃ and the heat treatment time is 0.5~6h.

[0018] Preferably, as an improvement, in step S3, after the heat treatment is completed, the furnace is cooled rapidly, and when the furnace temperature is ≥300℃, the cooling rate is 20℃ / min.

[0019] The principle and advantages of this scheme are as follows: Vanadium-based hydrogen storage alloys have the advantage of high hydrogen storage capacity at room temperature, but there are the following technical barriers in the application stage: On the one hand, pure vanadium is expensive. When using low-cost vanadium master alloys (such as FeV80) to replace pure vanadium, impurities such as Fe and O in the master alloy will induce the formation of a large number of Ti-rich phases (including C14 Laves phase and α-Ti phase of HCP structure, and C15 Laves phase and TiV phase of BCC structure); Ti-rich phases do not have hydrogen absorption and desorption properties, and will also lead to the absence of Ti element in the main phase of the alloy and the reduction of the cell volume, ultimately resulting in a significant decrease in reversible hydrogen storage capacity; on the other hand, the addition of a small amount of rare earth elements (such as Y and Ce) can only partially remove Si and O impurities, and cannot effectively suppress the formation of Ti-rich phases, so the effect of improving hydrogen storage capacity is limited.

[0020] This technical solution improves the reversible hydrogen storage capacity of the alloy through a three-dimensional synergy of "composition design, process optimization, and micro-control," while simultaneously achieving high cycle stability and low raw material costs. In this solution, a CrV master alloy is prepared, which is then used as a raw material to prepare a vanadium-based hydrogen storage alloy. During the preparation process, rare earth elements (such as Ce) are added to remove oxygen from the CrV master alloy. Since rare earth elements are difficult to integrate into the solid solution structure of vanadium-based alloys, and rare earths become stable rare earth hydrides after hydrogenation, excessive addition of rare earths would reduce the reversible hydrogen storage capacity of the alloy. Therefore, in existing technologies, the addition of rare earths is typically based on a stoichiometric amount required to convert O in the CrV master alloy into rare earth oxides.

[0021] However, during the research and development of this technical solution, it was unexpectedly discovered that the addition of excessive rare earth elements, combined with high melt temperature and rapid cooling rate, can effectively remove excess rare earth elements and their Ti-rich phases. Previous studies showed that as the ratio of rare earth element addition to oxygen content in the raw materials increased, the alloy's capacity continuously increased. Based on this, the inventors' team determined the optimal ratio range of rare earth to oxygen content through targeted research in subsequent development. This technical solution adds an excessive amount of rare earth elements—the amount of rare earth added is 0.65 to 0.86 times the O content in the CrV alloy (molar ratio), significantly exceeding the stoichiometric ratio of 0.5 (based on the molar ratio of Ce to O when forming CeO2). This suppresses the formation of Ti-rich phases within the alloy grains and at grain boundaries (Example 1), thereby significantly improving the reversible hydrogen storage capacity and overcoming the biases of existing technologies. By analyzing its principle in reverse, it was found that after adding excessive rare earth elements, the rare earth elements preferentially combine with O to form stable rare earth oxides (such as CeO2), thus completely removing O impurities. On the other hand, excessive rare earth elements are difficult to integrate into the vanadium-based solid solution structure, and can inhibit the nucleation and growth of Ti-rich phases within the crystal and at the grain boundaries through interfacial adsorption.

[0022] Furthermore, this technical solution combines electromagnetic stirring with the core invention of "excess rare earth deoxidation," efficiently removing reaction products through physical means and avoiding the negative impact of residual rare earth oxide inclusions on the alloy's hydrogen storage performance (such as cycle stability and activation performance). It ensures that after the excess rare earth achieves its effect of purifying oxygen impurities and suppressing titanium-rich phases, the byproducts generated can be effectively eliminated, thereby refining the alloy melt and improving the purity and overall performance of the final alloy. Rapid cooling after subsequent heat treatment maintains the alloy's high-temperature microstructure, which is beneficial for the formation of a supersaturated solid solution and inhibits the re-precipitation of harmful titanium-rich phases along grain boundaries.

[0023] In summary, the beneficial effects of this technical solution are as follows:

[0024] 1. In this technical solution, by adding a significant amount of rare earth elements (overcoming the bias of adding only small amounts of rare earth elements in existing technologies), the formation of Ti-rich phases within and at grain boundaries can be effectively suppressed, thereby increasing the reversible hydrogen storage capacity. For example: This invention (V 0.70 Ti 0.1 Cr 0.19 Fe 0.01 ) 93 The Ce7 alloy (Example 1), with a titanium-rich phase content reduced to 1.00 wt%, exhibited a hydrogen release of 2.66 wt.% at 50°C. In contrast, the (V) alloy described in this invention... 0.77 Ti 0.1 Cr 0.19 Fe 0.01 ) 99In the Ce1 alloy (Comparative Example 2), the content of titanium-rich phase was 5.37 wt%, and the hydrogen release of the alloy at 50 °C was 0.74 wt.%.

[0025] 2. The hydrogen storage alloy designed in this technical solution exhibits good cycle stability. For example: this invention (V 0.75 Ti 0.083 Cr 0.157 Fe 0.01 ) 93 Ce7 alloy (Example 2) had an initial reversible hydrogen release of 2.61 wt%, and after 100 cycles, the capacity retention reached 95.4 wt%.

[0026] 3. The vanadium-based hydrogen storage alloy developed in this technical solution can use low-cost CrV alloy as raw material, with a cost of less than 10% of that of pure metallic vanadium, which significantly reduces the preparation cost of hydrogen storage alloy.

[0027] 4. In this technical solution, by accelerating the cooling rate after heat treatment, the microstructure of the alloy at high temperature is maintained, and the precipitation of harmful titanium-rich phase along the grain boundaries is suppressed. Attached Figure Description

[0028] Figure 1 The XRD patterns are of the alloys in Examples 1-4 of this invention.

[0029] Figure 2 The images show the SEM microstructure and energy dispersive spectroscopy (EDS) analysis of the alloys in Examples 1-5 of this invention.

[0030] Figure 3 This is the hydrogen absorption kinetic curve of the alloy in Example 1 of the present invention.

[0031] Figure 4 The PCT curve for hydrogen desorption of the alloy in Example 1 of this invention is shown.

[0032] Figure 5 This is the hydrogen absorption kinetic curve of the alloy in Example 2 of the present invention.

[0033] Figure 6 The PCT curve for hydrogen desorption of the alloy in Example 2 of this invention is shown.

[0034] Figure 7 This is the hydrogen absorption kinetic curve of the alloy in Example 3 of the present invention.

[0035] Figure 8 The PCT curve for hydrogen desorption of the alloy in Example 3 of this invention is shown.

[0036] Figure 9 This is the hydrogen absorption kinetic curve of the alloy in Example 4 of the present invention.

[0037] Figure 10The PCT curve for hydrogen desorption of alloy in Example 4 of this invention is shown.

[0038] Figure 11 This is the hydrogen absorption kinetic curve of the alloy in Example 5 of the present invention.

[0039] Figure 12 The PCT curve for hydrogen desorption of the alloy in Example 5 of this invention is shown.

[0040] Figure 13 This is the hydrogen absorption kinetic curve of the alloy in Example 6 of the present invention.

[0041] Figure 14 The PCT curve for hydrogen desorption of the alloy in Example 6 of this invention is shown.

[0042] Figure 15 The XRD patterns are of alloys 1-7 in the comparative examples of this invention.

[0043] Figure 16 The images show the SEM microstructure of alloys 1-7 in the present invention.

[0044] Figure 17 This is the hydrogen absorption kinetic curve of alloy 1 in Comparative Example 1 of this invention.

[0045] Figure 18 The PCT curve for hydrogen desorption of alloy 1 in Comparative Example 1 of this invention is shown.

[0046] Figure 19 This is the hydrogen absorption kinetic curve of alloy 2 in Comparative Example 2 of this invention.

[0047] Figure 20 The present invention is a comparative example 2 alloy with hydrogen desorption PCT curve.

[0048] Figure 21 This is the hydrogen absorption kinetic curve of alloy 3 in Comparative Example 3 of this invention.

[0049] Figure 22 The PCT curve for hydrogen desorption of alloy 3 in Comparative Example 3 of this invention is shown.

[0050] Figure 23 This is the hydrogen absorption kinetic curve of alloy 4 in Comparative Example 4 of this invention.

[0051] Figure 24 The present invention is a comparative example 4 alloy with hydrogen desorption PCT curve. Detailed Implementation

[0052] The following detailed description provides further details on specific embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; and the materials and reagents used are all commercially available.

[0053] Overview of the plan:

[0054] A high-capacity vanadium-based solid solution hydrogen storage alloy rich in rare earth elements, with the chemical formula V x Ti y Cr z A m B n Where: 0.6≤x≤0.8, 0.067≤y≤0.133, 0.103≤z≤0.247, 0.01≤m≤0.04, 5≤n≤7, A is one or more of Fe, Al, Mn, Mo, Ni, and Co, and B is rare earth Y, Ce, La, or their alloys.

[0055] A method for preparing a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy includes the following steps:

[0056] S1. Preparation of CrV master alloy: The raw materials are V2O5, Al, CaO, slag-forming agent and Cr. The molar ratio of V2O5 to Al is 3:9.8~10. The amount of CaO and slag-forming agent added is 12~15% of the total mass of V2O5 and Al mixture. The amount of Cr added is 0.5~2.0% of the total mass of V2O5 and Al mixture. After mixing the raw materials, the CrV master alloy is obtained by aluminothermic reaction.

[0057] S2. Melting: Mix CrV master alloy, Ti, Fe, Cr and rare earth elements. The amount of rare earth added is 0.65-0.86 times (molar ratio) of the O content of CrV master alloy. Melt the mixture in a non-consumable arc furnace or suspension furnace to obtain cast alloy ingots.

[0058] The melting temperature is 1900-2200℃, the melting time is 1-10 min, and the melting process is carried out in an argon atmosphere while maintaining a vacuum degree of <5×10⁻⁶. -3 Pa; Using a melting current of 270~300A and electromagnetic stirring, after the alloy ingot is completely melted and clarified, the electromagnetic stirring is turned on and continued until the melting is finished. The stirring current is controlled at 30~50 A to make the melt rotate stably. The speed is controlled at 5~15 rpm, and the melting is repeated 3~5 times.

[0059] S3. Heat treat the cast alloy ingot to obtain a vanadium-based hydrogen storage alloy; the heat treatment temperature is 1300~1400℃ and the heat treatment time is 0.5~6h; after the heat treatment is completed, cool it rapidly, and when the furnace temperature is ≥300℃, the cooling rate is 20℃ / min.

[0060] Example 1

[0061] A high-capacity vanadium-based solid solution hydrogen storage alloy rich in rare earth elements, with an alloy composition of (V 0.70 Ti0.1 Cr 0.19 Fe 0.01 ) 93 Ce7 alloy is made of CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), Ti, Fe, Ce (all with a purity of 99.95 wt%), and the molar ratio of rare earth Ce to O in the CrV alloy is 0.74.

[0062] A method for preparing a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy includes the following steps:

[0063] S1. The master alloy is a CrV alloy with the following composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, and 0.2 wt.% Si.

[0064] S2. Melting: Melting is performed under a high-purity argon atmosphere (99.99%) using a non-consumable arc melting method. The ingot is repeatedly turned and melted five times to prepare a cast alloy ingot weighing approximately 20 g. The melting process uses a 300 A melting current with electromagnetic stirring. After the alloy ingot is completely melted and clarified, electromagnetic stirring is activated and continued until the end of melting. The stirring current is controlled at 45 A to maintain stable rotation of the melt at 10 rpm. The melting temperature is controlled at approximately 2000℃, and the melting time is approximately 5 minutes. The melting process involves three high-purity argon gas purgings, and the vacuum level is controlled to be <5 × 10⁻⁵. -3 Pa.

[0065] S3. Heat treatment: The cast alloy ingot is heated at 1400 ℃ under vacuum (vacuum degree < 5 × 10⁻⁶). -3 Heat treatment was performed for 0.5 h under vacuum (without high-purity argon gas washing or protection) to improve tissue homogeneity; after heat treatment, the cooling rate was 25 ℃ / min.

[0066] Experimental Example 1: Evaluation of Organizational Structure

[0067] Test method: The cast alloy ingot was sliced ​​using a slicer to obtain 1-3 mm alloy flakes. The alloy flakes were then mounted on sandpaper and polished to a mirror finish. The surface and microstructure were obtained by SEM testing.

[0068] Test results are as follows Figure 1 and 2As shown, the alloy is dominated by BCC phase, accounting for 99.00%, with a small amount of Ti-rich phase (1.00%) in the interdendritic space and very little granular CeO2 phase. This indicates that the composition design (excess rare earth addition, CrV master alloy raw material) and preparation process (electromagnetic stirring, rapid cooling) of this invention effectively suppress the formation of harmful Ti-rich phase, resulting in high purity of the alloy's main phase and laying a structural foundation for excellent hydrogen storage performance. Energy dispersive spectroscopy (EDS) analysis results (points 1 and 2) further verify that the granular material is rare earth oxides such as CeO2, rather than Ti-rich phase, confirming that the process of this invention can effectively achieve the dual objectives of rare earth impurity removal and Ti-rich phase suppression.

[0069] Experiment Example 2: Hydrogen Absorption / Desorption Performance Test

[0070] Test method: First, the alloy was activated by vacuuming in an 80 ℃ water bath for 2 h. After activation, hydrogen absorption kinetics were tested at 0 ℃ water bath and 9.5 MPa hydrogen pressure for cycles 1, 26, 50 and 100. Then, hydrogen desorption PCT was performed at 50 ℃ water bath and 9.5 MPa hydrogen pressure to determine the maximum hydrogen absorption and desorption and to calculate the cycle decay rate.

[0071] Figure 3 The figure shows the hydrogen absorption kinetics for cycles 1, 26, 50, and 100 of Example 1. Figure 4 The figure shows the hydrogen desorption PCT of Example 1 at cycles 1, 26, 50, and 100. The results show that the hydrogen storage alloy of Example 1 has a hydrogen absorption capacity of 3.87 wt.% in the first cycle, a hydrogen desorption capacity of 2.66 wt.% at 0.01 MPa in the first cycle, and a cycle decay rate of 7.9% after 100 cycles.

[0072] Example 2

[0073] The hydrogen storage alloy composition in this embodiment is (V 0.75 Ti 0.083 Cr 0.157 Fe 0.01 ) 93 Ce7 alloy is made of CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), Ti, Fe, Ce (all with a purity of 99.95 wt%), and the molar ratio of rare earth Ce to O in the CrV alloy is 0.69.

[0074] The preparation process, microstructure evaluation, and hydrogen absorption / desorption performance testing methods of the hydrogen storage alloy in this embodiment are the same as those in Example 1.

[0075] Organizational structure evaluation results as follows Figure 1 and 2As shown, the alloy is dominated by BCC phase, accounting for 98.97%, with a small amount of Ti-rich phase (content of 1.03%) in the interdendritic space and very little granular CeO2 phase.

[0076] Figure 5 The diagram shows the hydrogen absorption kinetics for cycles 1, 26, 50, and 100 of Example 2. Figure 6 The figure shows the hydrogen desorption PCT of Example 2 at cycles 1, 26, 50, and 100. The results show that the hydrogen storage alloy of Example 2 has a hydrogen absorption of 3.75 wt.% in the first cycle and a hydrogen desorption of 2.61 wt.% at 0.01 MPa in the first cycle. Moreover, with a V content of 75 at.%, the cycle decay rate after 100 cycles is 4.6%.

[0077] Example 3

[0078] The hydrogen storage alloy composition in this embodiment is (V 0.65 Ti 0.117 Cr 0.193 Fe 0.03 Al 0.01 ) 93 (LaCe)7 alloy is made of CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth LaCe to O in the CrV alloy is 0.86. The Ti-rich phase content in the alloy is 1.98 wt%.

[0079] The preparation process, microstructure evaluation, and hydrogen absorption / desorption performance testing methods of the hydrogen storage alloy in this embodiment are the same as those in Example 1.

[0080] Organizational structure evaluation results as follows Figure 1 and 2 As shown, the alloy is dominated by BCC phase, accounting for 98.02%, with a small amount of Ti-rich phase (content of 1.98%) in the interdendritic space and very little granular CeO2 phase.

[0081] Figure 7 The diagram shows the hydrogen absorption kinetics for cycles 1, 26, 50, and 100 of Example 3. Figure 8 The figure shows the hydrogen desorption PCT of Example 3 at cycles 1, 26, 50, and 100. The results show that the hydrogen storage alloy of Example 3 has a hydrogen absorption of 3.60 wt.% in the first cycle and a hydrogen desorption of 2.51 wt.% at 0.01 MPa in the first cycle. Moreover, with a V content of 60 at.%, the cycle decay rate after 100 cycles is 17.1%.

[0082] Example 4

[0083] The hydrogen storage alloy composition in this embodiment is (V 0.6 Ti 0.133 Cr 0.247 Fe 0.01 Mo 0.01 ) 93 The Ce7 alloy is a CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth Ce to O in the CrV alloy is 0.8. The Ti-rich phase content in the alloy is 1.3 wt%. The preparation process, microstructure evaluation, and hydrogen absorption / desorption performance testing methods of the hydrogen storage alloy in this embodiment are the same as those in Example 1.

[0084] Organizational structure evaluation results as follows Figure 1 and 2 As shown, the alloy is dominated by BCC phase, accounting for 98.7%, with a small amount of Ti-rich phase (content of 1.3%) in the interdendritic space and very little granular CeO2 phase.

[0085] Figure 9 The diagram shows the hydrogen absorption kinetics for cycles 1, 26, 50, and 100 of Example 4. Figure 10 The figure shows the hydrogen desorption PCT of Example 4 at cycles 1, 26, 50, and 100. The results show that the hydrogen storage alloy of Example 4 has a hydrogen absorption capacity of 3.88 wt.% in the first cycle, a hydrogen desorption capacity of 2.59 wt.% at 0.01 MPa in the first cycle, and a cycle decay rate of 9.7% after 100 cycles.

[0086] Example 5

[0087] The hydrogen storage alloy composition in this embodiment is (V 0.8 Ti 0.067 Cr 0.103 Fe 0.01 Mn 0.01 Mo 0.01 ) 95 Y5 is an alloy made of CrV alloy (composition: 92 wt.% V, 3.7 wt.% Cr, 2.7 wt.% O, 0.4 wt.% Fe, 0.2 wt.% Al, 0.1 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth Y to O in the CrV alloy is 0.65. The preparation process, microstructure evaluation, and hydrogen absorption / desorption performance testing methods of the hydrogen storage alloy in this embodiment are the same as those in Example 1.

[0088] Figure 11 The figure shows the hydrogen absorption kinetics for the first cycle of Example 5. Figure 12The figure shows the hydrogen desorption PCT of the first cycle in Example 5. The results show that the hydrogen storage alloy of Example 5 has a hydrogen absorption capacity of 3.88 wt.% in the first cycle and a hydrogen desorption capacity of 2.62 wt.% up to 0.01 MPa.

[0089] Example 6

[0090] The hydrogen storage alloy composition in this embodiment is (V 0.65 Ti 0.117 Cr 0.223 Fe 0.01 ) 93 The La7 alloy is a CrV alloy (composition: 92 wt.% V, 3.7 wt.% Cr, 2.7 wt.% O, 0.4 wt.% Fe, 0.2 wt.% Al, 0.1 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth La to O in the CrV alloy is 0.69. The preparation process, microstructure evaluation, and hydrogen absorption / desorption performance testing methods of the hydrogen storage alloy in this embodiment are the same as in Example 1.

[0091] Figure 13 The figure shows the hydrogen absorption kinetics for the first cycle of Example 6. Figure 14 The figure shows the hydrogen desorption PCT of the first cycle in Example 6. The results show that the hydrogen storage alloy of Example 6 has a hydrogen absorption capacity of 3.66 wt.% in the first cycle and a hydrogen desorption capacity of 2.50 wt.% at 0.01 MPa.

[0092] Comparative Example 1

[0093] The comparative hydrogen storage alloy composition is V. 75 Ti 8.3 Cr 15.7 Fe1, without the addition of rare earth elements such as Ce and Y during the smelting process. Except for the elemental composition, the preparation process, microstructure evaluation, and hydrogen absorption / desorption performance testing methods of the hydrogen storage alloy are the same as in Example 1.

[0094] Organizational structure evaluation results as follows Figure 15 As shown, the XRD pattern of Comparative Example 1 reveals that the alloy has a BCC structure and some C14 Laves phases. SEM image (…) Figure 16 The energy dispersive spectroscopy (EDS) results at point 3 show that, without the addition of Ce, the alloy of Comparative Example 1 contains a large number of bulk Ti-rich C14 Laves phases, as well as some acicular phases distributed within the crystals, accounting for approximately 10.12%. This figure, through comparison with the SEM images of the embodiments, clearly verifies the necessity of the "excess rare earth + optimized process" of the present invention for controlling the microstructure and reducing harmful phases.

[0095] Comparative Example 1 alloy's first-cycle capacity was only 1.62 wt.% ( Figure 17The reversible hydrogen release is only 0.70 wt.% ( Figure 18 Furthermore, the slow hydrogen absorption rate indicates that without rare earth elements, the large amount of Ti-rich phase severely hinders the diffusion of hydrogen atoms, leading to a sharp decline in hydrogen absorption activity.

[0096] Comparative Example 2

[0097] The composition of this comparative hydrogen storage alloy is (V 0.75 Ti 0.083 Cr 0.157 Fe 0.01 ) 99 Ce1 alloy was prepared using a CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth Ce to O in the CrV alloy was 0.099. Except for the elemental composition, the preparation process, microstructure evaluation, and hydrogen absorption / desorption performance testing methods for the hydrogen storage alloy were the same as in Example 1.

[0098] Organizational structure evaluation results as follows Figure 15 As shown, the XRD pattern of Comparative Example 2 reveals that the alloy has a BCC structure and some C14 Laves phases. SEM image (…). Figure 16 The data shows that the Ti-rich phase content in Comparative Example 2 is 5.36%. The first-cycle capacity of the alloy in Comparative Example 2 is only 1.65 wt.%. Figure 19 The reversible hydrogen release is only 0.74 wt.% ( Figure 20 This indicates that when the amount of rare earth added is insufficient, it is impossible to effectively remove O impurities and suppress the Ti-rich phase, resulting in no significant improvement in hydrogen absorption activity and difficulty in increasing hydrogen storage capacity.

[0099] Comparative Example 3

[0100] The composition of this comparative hydrogen storage alloy is (V 0.75 Ti 0.083 Cr 0.157 Fe 0.01 ) 97 The Ce3 alloy was made of CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth Ce to O in the CrV alloy was 0.30. Except for the elemental composition, the preparation process, microstructure evaluation, and hydrogen absorption / desorption performance testing methods of the hydrogen storage alloy were the same as in Example 1.

[0101] Organizational structure evaluation results as follows Figure 15 As shown, the XRD pattern of Comparative Example 3 reveals that the alloy has a BCC structure and some C14 Laves phases. SEM image ( Figure 16 The data shows that the Ti-rich phase content in Comparative Example 3 is 4.30%. The first-cycle capacity of the alloy in Comparative Example 2 is only 3.36 wt.%. Figure 21 The reversible hydrogen release is only 2.19 wt.% ( Figure 22 The results showed that when the rare earth content reached 0.30%, some O impurities were removed and the hydrogen absorption activity was improved, but the optimal level was not reached due to the residual Ti-rich phase (4.30 wt.%).

[0102] Comparative Example 4

[0103] The composition of this comparative hydrogen storage alloy is (V 0.75 Ti 0.083 Cr 0.157 Fe 0.01 ) 91 Ce9 alloy was prepared using a CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth Ce to O in the CrV alloy was 0.89. Except for the elemental composition, the preparation process, microstructure evaluation, and hydrogen absorption / desorption performance testing methods for the hydrogen storage alloy were the same as in Example 1.

[0104] Organizational structure evaluation results as follows Figure 15 As shown, the XRD pattern of Comparative Example 4 reveals that the alloy has a BCC structure. (SEM image) Figure 16 The energy dispersive spectroscopy (EDS) results at point 4 show that Comparative Example 4 still has a small amount of acicular phase distributed within the crystals, and the content of Ti-rich phase is reduced. However, the excessive addition of Ce leads to the appearance of large Ce₂O₃ spherical particles in the alloy of Comparative Example 4, and the total content of the second phase is 4.31%. The first-cycle capacity of the alloy of Comparative Example 4 is 3.88 wt.%. Figure 23 The reversible hydrogen release is only 2.45 wt.% ( Figure 24 The results show that excessive rare earth elements did not affect hydrogen absorption activity, but subsequent cycling performance was significantly affected by rare earth oxide inclusions, indicating that more rare earth elements are not necessarily better.

[0105] Comparative Example 5

[0106] The composition of this comparative hydrogen storage alloy is (V 0.75 Ti 0.11 Cr 0.12 Fe 0.02 ) 95Ce5 alloy was made from CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth Ce to O in the CrV alloy was 0.89. In Comparative Example 5, the alloy was smelted using a magnetic stirring current of 25 A, a melt rotation speed of 4 rpm, and a cooling rate of 20 °C / min after heat treatment.

[0107] Organizational structure evaluation results as follows Figure 15 As shown, the XRD pattern of Comparative Example 5 reveals that the alloy has a BCC structure with some C14 Laves phase. SEM image (…) Figure 16 The results show that Comparative Example 5 has a large number of needle-like Ti-rich phases distributed in the crystals, and a large number of Ti-rich phases precipitated between the grain boundaries.

[0108] Comparative Example 6

[0109] The composition of this comparative hydrogen storage alloy is (V 0.75 Ti 0.11 Cr 0.12 Fe 0.02 ) 95 Ce5 alloy was made from CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth Ce to O in the CrV alloy was 0.89. In Comparative Example 6, the alloy was smelted using a magnetic stirring current of 30 A and a melt rotation speed of 6 rpm; the cooling rate after heat treatment was 15 ℃ / min.

[0110] Organizational structure evaluation results as follows Figure 15 As shown, the XRD pattern of Comparative Example 6 reveals that the alloy has a BCC structure with some C14 Laves phase. SEM image (…) Figure 16 The results show that Comparative Example 6 has some needle-like Ti-rich phases distributed in the crystal, and due to the low rotation speed, a large number of Ce2O3 spherical particles are mixed in.

[0111] Comparative Example 7

[0112] The composition of this comparative hydrogen storage alloy is (V 0.75 Ti 0.11 Cr 0.12 Fe 0.02 ) 95Ce5 alloy was made from CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth Ce to O in the CrV alloy was 0.89. In Comparative Example 7, the alloy was smelted using a magnetic stirring current of 50 A and a melt rotation speed of 15 rpm; the cooling rate after heat treatment was 15 °C / min.

[0113] Organizational structure evaluation results as follows Figure 15 As shown, the XRD pattern of Comparative Example 7 reveals that the alloy has a BCC structure with some C14 Laves phase. SEM image (…) Figure 16 The results show that due to the low cooling rate, a large amount of Ti-rich phase precipitates in the crystal and between the grain boundaries in Comparative Example 7. Due to the appropriate rotation speed, only a small amount of Ce2O3 spherical particles are mixed in.

[0114] Comparative Example 8

[0115] The hydrogen storage alloy composition in this embodiment is (V 0.6 Ti 0.133 Cr 0.247 Fe 0.01 Mo 0.01 ) 93 Ce7 alloy was constructed using a CrV alloy (composition: 84 wt.% V, 10 wt.% Cr, 4 wt.% O, 0.5 wt.% Fe, 0.4 wt.% Al, 0.2 wt.% Si), with Ti, Fe, and Ce (all with a purity of 99.95 wt%). The molar ratio of rare earth Ce to O in the CrV alloy was 0.8. The microstructure evaluation and hydrogen absorption / desorption performance testing methods for this comparative alloy were the same as in Example 1. However, magnetic stirring was not used during the melting process.

[0116] Organizational structure evaluation results as follows Figure 15 As shown, the XRD pattern of Comparative Example 8 reveals that the alloy has a BCC structure with some C14 Laves phase. SEM image (…) Figure 16 The results show that the lack of magnetic stirring process resulted in a large number of granular Ce2O3 phases inside the alloy.

[0117] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy, characterized in that: The chemical formula is V x Ti y Cr z A m B n Where: 0.6≤x≤0.8, 0.067≤y≤0.133, 0.103≤z≤0.247, 0.01≤m≤0.04, 5≤n≤7, A is one or more of Fe, Al, Mn, Mo, Ni, and Co, and B is rare earth Y, Ce, La, or their alloys. The addition amount of rare earth Y, Ce, La, or their alloys is added in excess according to the O content of CrV master alloy, and the molar ratio of the addition amount of rare earth Y, Ce, La, or their alloys to the O content of CrV master alloy is 0.65~0.

86.

2. The method for preparing a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy according to claim 1, characterized in that, Includes the following steps: S1. Prepare the intermediate alloy: The intermediate alloy is a CrV intermediate alloy; S2. Smelting: Mix CrV master alloy, Ti, Fe, Cr and rare earth elements, and smelt to obtain cast alloy ingot; the molar ratio of rare earth addition to O content in CrV master alloy is 0.65~0.

86. S3. Heat treatment: Heat treatment is performed on the cast alloy ingot to obtain vanadium-based hydrogen storage alloy.

3. The method for preparing a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy according to claim 2, characterized in that: In step S1, the raw materials for preparing the CrV master alloy include V2O5, Al, CaO, slag-forming agent and Cr. The molar ratio of V2O5 to Al is 3:9.8~10. The amount of CaO and slag-forming agent added is 12~15% of the total mass of the V2O5 and Al mixture, and the amount of Cr added is 0.5~2.0% of the total mass of the V2O5 and Al mixture.

4. The method for preparing a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy according to claim 3, characterized in that: In step S2, the melting temperature is 1900~2200℃ and the melting time is 1~10 min.

5. The method for preparing a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy according to claim 4, characterized in that: In step S2, the melting process is carried out in an argon atmosphere with an argon pressure of 0.07-0.08 MPa.

6. The method for preparing a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy according to claim 5, characterized in that: In step S2, the method of using smelting current and electromagnetic stirring is adopted. After the alloy ingot is completely melted and clarified, the electromagnetic stirring is turned on. The smelting current is 270~300A, the rotation speed is 5~15 rpm, and the number of smelting times is 3~5.

7. The method for preparing a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy according to claim 6, characterized in that: In step S3, the heat treatment temperature is 1300~1400℃ and the heat treatment time is 0.5~6h.

8. The method for preparing a rare earth-rich, high-capacity vanadium-based solid solution hydrogen storage alloy according to claim 7, characterized in that: In step S3, after the heat treatment is completed, the furnace is cooled rapidly. When the furnace temperature is ≥300℃, the cooling rate is 20℃ / min.

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