A body-centered cubic hydrogen storage alloy and a method for preparing the same

Abstract

The application provides a body-centered cubic structure hydrogen storage alloy and a preparation method thereof. The hydrogen storage alloy has a general formula of Ti x Cr y M z , wherein 0.35≤x≤0.55, 0.35≤y≤0.55, and 0

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen storage alloys, and in particular relates to a hydrogen storage alloy with a body-centered cubic structure and a preparation method thereof. Background Art

[0002] Energy is a vital engine for sustainable human development and industrial progress. As the energy crisis intensifies, global climate change poses a significant threat to human society. The development of clean, efficient, renewable energy and the establishment of a system for its generation and supply are urgent. Hydrogen, a high-energy-density, clean energy source, will play a crucial role in future renewable energy systems. However, the safe storage and transportation of hydrogen has long constrained its large-scale application and remains a critical technical challenge that urgently needs to be addressed.

[0003] Solid-state hydrogen storage technology is a hot topic in current hydrogen storage technology research and has important application prospects due to its outstanding advantages such as high volume density, obvious safety advantages, and easy implementation of equipment and infrastructure. Currently, solid-state hydrogen storage alloys can be divided into five categories according to the main types of constituent elements: rare earth lanthanum series, Laves phase AB type titanium iron series, Laves phase AB2 type zirconium series or titanium series, magnesium series, and BCC type series. Rare earth lanthanum series hydrogen storage alloys have good hydrogen absorption power and moderate platform pressure, and have been successfully applied in nickel-hydrogen batteries, but their disadvantages are that their capacity is too low to meet high capacity requirements, and they are prone to cause unit cell volume expansion during the hydrogen absorption and desorption cycle, resulting in structural instability and poor cycle stability; AB type titanium iron series hydrogen storage alloys can achieve reversible hydrogen absorption and desorption, and their hydride decomposition pressure is low, which meets practical requirements. In addition, the elements on both sides are abundant in nature, but they are difficult to activate, have poor anti-poisoning ability, and have problems such as short cycle life; titanium zirconium series hydrogen storage alloys have Laves Phase, its hydrogen storage capacity is <2.0wt.%, the hydrogen absorption and desorption kinetics are good, and the platform hysteresis is small, but it also has some difficult-to-overcome disadvantages such as difficulty in activation and high price; magnesium-based hydrogen storage alloys have a hydrogen storage capacity of up to 7.6wt.%, and magnesium resources are abundant and cheap, but the hydrides formed are too stable and the kinetics are slow, which greatly limits their practical application; although BCC-type vanadium-based hydrogen storage alloys have a high hydrogen storage capacity, the raw material metal vanadium has high smelting cost, low hydrogen desorption pressure, and a lot of residual hydrogen, which is difficult to activate, and there is still a long way to go before practical application.

[0004] In summary, existing solid-state hydrogen storage materials are unable to meet the needs of current practical applications, hindering their further development. Therefore, developing a low-cost, high-capacity, easily activated BCC-type hydrogen storage alloy with a moderate plateau pressure, and hydrogen storage performance comparable to conventional V-based hydrogen storage alloys, is a pressing technical challenge for those skilled in the art. Summary of the Invention

[0005] The object of the present invention is to provide a hydrogen storage alloy with a body-centered cubic structure and a preparation method thereof. The present invention prepares a hydrogen storage alloy with a body-centered cubic structure without using vanadium. At the same time, it has the same hydrogen storage performance as a conventional V-based hydrogen storage alloy. The provided preparation method has a simple process and low cost.

[0006] To achieve the object of this invention, the following technical solutions are adopted in the present invention:

[0007] In the first aspect, the present invention provides a hydrogen storage alloy with a body-centered cubic structure. The general formula of the composition of the hydrogen storage alloy is Ti x Cr y M z , where 0.35 ≤ x ≤ 0.55, 0.35 ≤ y ≤ 0.55, 0 < z ≤ 0.10;

[0008] where M includes Nb or Ta.

[0009] Through the optimized design of each component, the present invention uses Nb or Ta to replace the V element. Nb, Ta and V belong to the same group of elements and all have a body-centered cubic structure. At the same time, the Ti, Cr, Nb or Ta ternary alloy has a body-centered cubic structure in the high-temperature phase diagram region, and hydrogen atoms exist in the octahedral and tetrahedral interstitial sites of the body-centered cubic structure. This structure has a higher theoretical hydrogen storage capacity compared to the Laves phase structure; the hydrogen storage alloy with a body-centered cubic structure has a low cost, high capacity, is easy to activate, has a moderate plateau pressure, and at the same time has a hydrogen storage performance similar to that of a conventional V-based hydrogen storage alloy.

[0010] In the present invention, it is necessary to control the sum of the molar ratios of each element to be 1, that is, x + y + z = 1.

[0011] In the present invention, the proportion of the Ti element in the hydrogen storage alloy is 0.35 ≤ x ≤ 0.55. For example, it can be 0.37, 0.4, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52 or 0.54, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable; the proportion of the Cr element in the hydrogen storage alloy is 0.35 ≤ x ≤ 0.55. For example, it can be 0.37, 0.4, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52 or 0.54, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable; the proportion of the M element in the hydrogen storage alloy is 0 < z ≤ 0.10. For example, it can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08 or 0.09, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0012] As a preferred technical solution of the present invention, in the hydrogen storage alloy, in terms of molar ratio: 0.40 ≤ x ≤ 0.50, 0.45 ≤ y ≤ 0.55, 0.03 < z ≤ 0.06.

[0013] Preferably, in the hydrogen storage alloy, in terms of molar ratio: 0.50 ≤ Ti / Cr ≤ 1.30. For example, it can be 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2 or 1.25, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable. Preferably it is 0 ≤ Ti / Cr ≤ 1.20.

[0014] It should be noted that in the present invention, the ratio of Ti / Cr is further controlled within the range of 0.70 - 1.20. Since Ti belongs to the hydrogen absorption side element and Cr belongs to the non-hydrogen absorption element, too low Ti will lead to a decrease in hydrogen absorption amount, while too high Ti will make the plateau pressure of the material too low; the Cr content also affects the hydrogen absorption amount and plateau pressure.

[0015] In the present invention, for the hydrogen storage alloy Ti x Cr y M z , 0.40 ≤ x ≤ 0.50, 0.45 ≤ y ≤ 0.55, 0.03 < z ≤ 0.10 and 0.70 ≤ Ti / Cr ≤ 1.20 can both increase the hydrogen storage amount and make the plateau pressure moderate.

[0016] As a preferred technical solution of the present invention, the maximum hydrogen absorption amount of the hydrogen storage alloy ≥ 3.2 wt%, for example, it can be 3.25 wt%, 3.3 wt%, 3.35 wt%, 3.4 wt%, 3.45 wt%, 3.5 wt%, 3.6 wt% or 3.7 wt%, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0017] Preferably, the maximum hydrogen desorption amount of the hydrogen storage alloy ≥ 2.3 wt%, for example, it can be 2.32 wt%, 2.34 wt%, 2.36 wt%, 2.38 wt%, 2.4 wt%, 2.42 wt%, 2.44 wt%, 2.48 wt% or 2.5 wt%, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0018] Preferably, the crystal structure of the hydrogen storage alloy is a body-centered cubic structure (BCC type).

[0019] In the second aspect, the present invention provides a preparation method of the hydrogen storage alloy described in the first aspect. The preparation method includes the following steps:

[0020] (1) Weigh the materials according to the element ratio of the general formula of the hydrogen storage alloy composition, and then carry out smelting to obtain a cast alloy;

[0021] (2) The cast alloy described in step (1) is encapsulated and quenched in sequence to obtain a hydrogen storage alloy.

[0022] The preparation method provided by the present invention adopts a specific raw material ratio combined with a redesigned preparation method, and the ingredients are melted, packaged and quenched in sequence, and the crystal form of the alloy is controlled, so that the alloy has a flat hydrogen absorption and desorption platform pressure, thereby significantly improving the hydrogen storage performance of the alloy. The preparation method is simple to operate and low in cost.

[0023] As a preferred technical solution of the present invention, the smelting current in step (1) is 100 to 180 A, for example, it can be 110 A, 120 A, 130 A, 140 A, 150 A, 160 A or 170 A, etc., but is not limited to the listed values. Other values ​​not listed within this range are also applicable.

[0024] In the present invention, the raw materials used in the batching in step (1) are all metal powders with a purity of ≥99.9%.

[0025] In the present invention, the smelting in step (1) is carried out under an inert gas, the smelting equipment includes an electric arc furnace, and the inert gas includes argon.

[0026] Preferably, the smelting time in step (1) is 60 to 120 s / time, for example, it can be 70 s / time, 80 s / time, 90 s / time, 100 s / time, 110 s / time or 120 s / time, but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0027] Preferably, the smelting in step (1) is performed 3 to 5 times, for example, 3 times, 4 times or 5 times.

[0028] In the present invention, the smelting is repeated 3 to 5 times. After one smelting, the metal is cooled to room temperature along with the equipment and then turned over for the next smelting. Multiple smelting can make the multiple metal components more evenly mixed.

[0029] As a preferred technical solution of the present invention, the crystal structure of the cast alloy in step (1) includes a Laves phase.

[0030] Preferably, the lattice constant of the cast alloy in step (1) is 0.312 to 0.321 nm, for example, it can be 0.314 nm, 0.316 nm, 0.318 nm, 0.320 nm or 0.3205 nm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] As a preferred technical solution of the present invention, the packaging in step (2) is: wrapping the cast alloy with tantalum sheets and then packaging it in a quartz tube filled with inert gas.

[0032] In the present invention, the packaging in step (2) is specifically as follows: the cast alloy is wrapped with a tantalum sheet and placed in a quartz tube, and then the quartz tube is evacuated and the molecular pump is activated to 2.0×10 -3 MPa, then introduce inert gas, and finally seal the quartz tube.

[0033] Preferably, the vacuum degree in the quartz tube is -0.07 to -0.09 MPa, for example, -0.072 MPa, -0.075 MPa, -0.08 MPa, -0.085 MPa or -0.088 MPa, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0034] As a preferred technical solution of the present invention, the quenching in step (2) includes sequentially performing heat treatment and rapid cooling.

[0035] Preferably, the heating rate of the heat treatment is 10 to 20°C / min, for example, it can be 12°C / min, 14°C / min, 15°C / min, 16°C / min or 18°C / min, but is not limited to the listed values. Other values ​​not listed within this range are also applicable.

[0036] Preferably, the holding temperature of the heat treatment is 1380-1480°C, for example, it can be 1390°C, 1400°C, 1410°C, 1420°C, 1430°C, 1440°C, 1450°C, 1460°C or 1470°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0037] Preferably, the holding time of the heat treatment is 1 to 10 minutes, for example, it can be 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes or 9 minutes, but is not limited to the listed values. Other values ​​not listed within this range are also applicable.

[0038] Preferably, the rapid cooling is: placing the heat-treated cast alloy in liquid nitrogen or cold water.

[0039] In the present invention, the heat-treated cast alloy is quickly placed in liquid nitrogen or cold water for rapid cooling.

[0040] As a preferred technical solution of the present invention, step (2) further includes grinding and crushing in sequence after quenching.

[0041] Preferably, the particle size of the crushed alloy powder is 80 to 200 mesh, for example, it can be 90 mesh, 100 mesh, 110 mesh, 120 mesh, 130 mesh, 140 mesh, 150 mesh, 160 mesh, 170 mesh, 180 mesh or 190 mesh, but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0042] Preferably, the crystal structure of the hydrogen storage alloy is a body-centered cubic structure.

[0043] Preferably, the crystal constant of the hydrogen storage alloy is 0.306-0.311 nm, for example, it can be 0.306 nm, 0.307 nm, 0.308 nm, 0.309 nm, 0.310 nm, 0.311 nm or 0.3105 nm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0044] The crystal constant of the hydrogen storage alloy of the present invention is slightly smaller than the crystal constant of the cast alloy obtained in step (1) because the atomic radius of the Nb and Ta elements is smaller than the atomic radius of the Ti element. After rapid heat treatment, the nucleation rate is large due to rapid solidification, the grains are not easy to grow, and the alloy grain structure is fine and uniform.

[0045] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0046] (1) preparing the ingredients according to the element ratio of the general formula of the hydrogen storage alloy, and then smelting to obtain a cast alloy with a lattice constant of 0.312 to 0.321 nm;

[0047] The smelting current is 100-180A, the time is 60-120s / time, and the number of times is 3-5 times;

[0048] (2) After encapsulating the cast alloy described in step (1), heating it to 1380-1480° C. at a rate of 10-20° C. / min for heat treatment for 1-10 min, then placing the heat-treated cast alloy in liquid nitrogen or water, and then grinding and crushing it to obtain a hydrogen storage alloy with a crystal constant of 0.306-0.311 nm;

[0049] The packaging is as follows: the cast alloy is wrapped with tantalum sheets and then packaged in a quartz tube filled with inert gas.

[0050] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The hydrogen storage alloy provided by the present invention has an elemental molar composition of Ti x Cr y M z , it has the same hydrogen storage performance as conventional V-based hydrogen storage alloys, with a maximum hydrogen absorption capacity of ≥3.2wt%, a maximum hydrogen release capacity of ≥2.3wt%, and a moderate platform pressure;

[0053] (2) The hydrogen storage alloy provided by the present invention improves the hydrogen absorption and desorption capacity, activation performance and cycle performance of the alloy by sequentially performing smelting, packaging, heat treatment and rapid cooling. The preparation process is simple and low-cost. The alloy is modified by combining high-temperature heat treatment and rapid rapid cooling to regulate the crystal form, so that the alloy has a BCC single-phase structure and a flat hydrogen absorption and desorption platform pressure, thereby having a higher hydrogen absorption and desorption capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Graph (298K) showing the hydrogen absorption process of the hydrogen storage alloys in Examples 1-2, Example 6, Example 10, and Comparative Example 5;

[0055] Figure 2 PCT curve diagram (373K) of the hydrogen storage alloys in Examples 1-2 and 7. DETAILED DESCRIPTION

[0056] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0057] Example 1

[0058] This embodiment provides a BCC type hydrogen storage alloy and a preparation method thereof. The composition formula of the hydrogen storage alloy is Ti 0.50 Cr 0.45 Nb 0.05 ;

[0059] The preparation method comprises the following steps:

[0060] (1) According to the molar ratio of the target hydrogen storage alloy, 10 g of metal was mixed and then heated to 2.0 × 10 -3 The alloy was melted in an electric arc furnace under a vacuum of 1.5 Pa, and the crucible was turned over after cooling to room temperature. The melting was repeated 4 times to obtain a cast alloy with a lattice constant of 0.314 nm.

[0061] The smelting current is 140A and the smelting time is 90s / time;

[0062] (2) Wrap the cast alloy described in step (1) with tantalum sheets and place it in a quartz tube. Evacuate the quartz tube and start the molecular pump to 2.0×10-3 MPa or less, after passing argon, the quartz tube was sealed, and then heated to 1400°C at a rate of 15°C / min for 10 minutes, and then quickly placed in liquid nitrogen for rapid cooling, and finally mechanically polished to remove the oxide scale, and mechanically crushed and sieved to 100 mesh to obtain a hydrogen storage alloy with a crystal constant of 0.3083nm;

[0063] The vacuum degree in the quartz tube is -0.08 MPa.

[0064] Example 2

[0065] This embodiment provides a BCC type hydrogen storage alloy and a preparation method thereof. In addition to the general formula of the hydrogen storage alloy being Ti 0.40 Cr 0.55 Ta 0.05 Except for this, other conditions are the same as those in Example 1.

[0066] Example 3

[0067] This embodiment provides a BCC type hydrogen storage alloy and a preparation method thereof. The composition formula of the hydrogen storage alloy is Ti 0.50 Cr 0.45 Nb 0.05 ;

[0068] The preparation method comprises the following steps:

[0069] (1) According to the molar ratio of the target hydrogen storage alloy, 10 g of metal was mixed and then heated to 2.0 × 10 -3 Pa in an electric arc furnace, and the crucible was turned over after cooling to room temperature. The melting was repeated 5 times to obtain a cast alloy with a lattice constant of 0.313 nm.

[0070] The smelting current is 100A and the smelting time is 120s / time;

[0071] (2) Wrap the cast alloy described in step (1) with tantalum sheets and place it in a quartz tube. Evacuate the quartz tube and start the molecular pump to 2.0×10 -3 MPa or less, after passing argon, the quartz tube was sealed, and then heated to 1480℃ at a rate of 15℃ / min for 5min, and then quickly placed in liquid nitrogen for rapid cooling, and finally mechanically polished to remove the oxide scale, and mechanically crushed and sieved to 150 mesh to obtain a hydrogen storage alloy with a crystal constant of 0.307nm;

[0072] The vacuum degree in the quartz tube is -0.08 MPa.

[0073] Example 4

[0074] This embodiment provides a BCC type hydrogen storage alloy and a preparation method thereof. In addition to the general formula of the hydrogen storage alloy being Ti 0.35 Cr 0.55 Nb 0.10 Except for this, other conditions are the same as those in Example 1.

[0075] Example 5

[0076] This embodiment provides a BCC type hydrogen storage alloy and a preparation method thereof. In addition to the general formula of the hydrogen storage alloy being Ti 0.55 Cr 0.35 Nb 0.10 Except for this, other conditions are the same as those in Example 1.

[0077] Example 6

[0078] This embodiment provides a hydrogen storage alloy and a preparation method thereof. Except that the smelting time in step (1) is 20 s / time, other conditions are the same as those in Example 2.

[0079] Example 7

[0080] This embodiment provides a hydrogen storage alloy and a preparation method thereof. Except that the heat treatment temperature in step (2) is raised to 1000° C., other conditions are the same as those in Example 1.

[0081] Example 8

[0082] This embodiment provides a hydrogen storage alloy and a preparation method thereof. Except that the heat treatment temperature in step (2) is raised to 1500° C., other conditions are the same as those in Example 1.

[0083] Example 9

[0084] This embodiment provides a hydrogen storage alloy and a preparation method thereof. Except that the holding time of the heat treatment in step (2) is 30 minutes, other conditions are the same as those in Example 1.

[0085] Example 10

[0086] This embodiment provides a hydrogen storage alloy and a preparation method thereof. Except for the furnace cooling after the heat treatment in step (2), other conditions are the same as those in Example 1.

[0087] Comparative Example 1

[0088] This comparative example provides a hydrogen storage alloy and a preparation method thereof. Except that no Nb element is added to the hydrogen storage alloy and an equal amount of Ce is used instead, other conditions are the same as those in Example 1.

[0089] Comparative Example 2

[0090] This comparative example provides a hydrogen storage alloy and a preparation method thereof, except that the composition formula of the hydrogen storage alloy is Ti 0.30 Cr 0.65 Nb 0.05 Except for this, other conditions are the same as those in Example 1.

[0091] Comparative Example 3

[0092] This comparative example provides a hydrogen storage alloy and a preparation method thereof, except that the composition formula of the hydrogen storage alloy is Ti 0.60 Cr 0.35 Nb 0.05 Except for this, other conditions are the same as those in Example 1.

[0093] Comparative Example 4

[0094] This comparative example provides a hydrogen storage alloy and a preparation method thereof, except that the composition formula of the hydrogen storage alloy is Ti 0.45 Cr 0.35 Nb 0.20 Except for this, other conditions are the same as those in Example 1.

[0095] Comparative Example 5

[0096] This comparative example provides a hydrogen storage alloy and a preparation method thereof. Except that the tube sealing and heat treatment are not performed, other conditions are the same as those in Example 1.

[0097] The hydrogen storage alloys prepared in the above examples and comparative examples were activated and then tested for hydrogen storage performance at 100° C. and 8 MPa hydrogen pressure.

[0098] The activation treatment is as follows: keeping the temperature at 400° C. and evacuating the reactor (the pressure in the reactor is kept below <0.001 MPa) for 60 minutes.

[0099] Figure 1 This is a hydrogen absorption process diagram (298K) of the hydrogen storage alloy in Examples 1-2, Example 6, Example 10 and Comparative Example 5 of the present invention. It can be found that too short a smelting time, cooling with the furnace after heat treatment, and no heat treatment are not conducive to improving the hydrogen absorption kinetics of the hydrogen storage alloy.

[0100] Figure 2 This is the PCT curve diagram (373K) of the hydrogen storage alloys in Examples 1-2 and Example 7 of the present invention. It can be found that the heat treatment temperature is too low, resulting in a decrease in hydrogen absorption performance.

[0101] The test results of the above embodiments and comparative examples are shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] Among them: If the alloy is a composite phase, the lattice constant does not have a unique value;

[0106] The following points can be drawn from Table 1:

[0107] (1) The hydrogen storage alloys and preparation methods provided in Examples 1-3 of the present invention have the same hydrogen storage performance as conventional V-based hydrogen storage alloys, with a maximum hydrogen absorption capacity of ≥3.2 wt%, a maximum hydrogen release capacity of ≥2.3 wt%, and a moderate plateau pressure;

[0108] (2) Based on Example 1 and Examples 4-5, it can be seen that when the Ti / Cr ratio is not within the preferred range of 0.70 to 1.20, the hydrogen absorption platform pressure of the alloy is too low or too high, resulting in poor hydrogen storage performance;

[0109] (3) Based on Examples 2 and 6, it can be seen that due to the high melting point of the metal Ta in the alloy component, it is necessary to extend the necessary smelting time to achieve the homogenization process of the multi-component alloy. If the smelting time is too short, it will lead to smelting non-uniformity and poor hydrogen storage performance.

[0110] (4) From Example 1 and Examples 7-8, it can be seen that when the heat treatment temperature is too low, the internal elements of the alloy are not fully diffused, the uniformity of the alloy is reduced, and the hydrogen absorption platform pressure of the alloy is still relatively inclined, resulting in a small amount of hydrogen absorption and effective hydrogen release; when the heat treatment temperature is too high, the quartz tube is easily softened and cracked, and the sample is oxidized during the heat treatment process, and the hydrogen storage performance deteriorates; from Example 1 and Example 9, it can be seen that when the heat treatment holding time is too long, the internal thermal stress of the alloy increases, and recrystallization and grain growth are prone to occur, thereby affecting the hydrogen absorption and effective hydrogen release;

[0111] (5) Based on Example 1 and Example 10, it can be seen that due to the cooling of the furnace at high temperature, the alloy in the quartz tube cannot maintain the phase structure at high temperature. The sample forms a Laves phase structure after cooling, resulting in a decrease in hydrogen storage performance.

[0112] (6) Based on Example 1 and Comparative Example 1, it can be seen that when an equal amount of rare earth element Ce is used to replace Nb, due to the intrinsic characteristics between the elements, a BCC structure cannot be formed in the high-temperature phase region, resulting in the alloy presenting a single Laves phase, making the theoretical hydrogen storage capacity less than 2 wt%, resulting in a decrease in hydrogen storage performance;

[0113] (7) Based on Example 1 and Comparative Examples 2-3, it can be seen that when the Ti or Cr content in the hydrogen storage alloy is too high or too low, Ti is a hydrogen-absorbing element, while Cr is a non-hydrogen-absorbing element. When the Ti content is too high, the hydrogen absorption capacity of the alloy increases, but the plateau pressure is very low. When the Ti content is too low, the total hydrogen absorption capacity of the alloy decreases, and it is difficult to form a single BCC structure, resulting in a decrease in hydrogen storage performance.

[0114] (8) Based on Example 1 and Comparative Example 4, it can be seen that when the Nb content in the hydrogen storage alloy is too high, the alloy is not easy to form a single BCC structure, and a Laves-based phase structure is likely to appear, resulting in a decrease in hydrogen storage performance and capacity;

[0115] (9) Based on Example 1 and Comparative Example 5, it can be seen that the phase structure of the alloy in the cast state is mainly the Laves phase, which cannot be completely transformed into the BCC phase. Therefore, its hydrogen storage capacity is about 2.2 wt.%, resulting in a significant decrease in hydrogen absorption capacity and poor hydrogen storage performance.

[0116] The applicant declares that the present invention is not limited to the above-described detailed structural features through the above-described embodiments, and does not necessarily rely on the above-described detailed structural features for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A body-centered cubic hydrogen storage alloy, characterized in that: The general formula of the hydrogen storage alloy is Ti x Cr y M z , wherein according to the molar ratio, 0.35≤x≤0.55, 0.35≤y≤0.55, 0 <z≤0.10; wherein M comprises Nb or Ta; The preparation method of the body-centered cubic hydrogen storage alloy comprises the following steps: (1) preparing the ingredients according to the element ratio of the general formula of the hydrogen storage alloy, and then smelting to obtain a cast alloy; (2) encapsulating and quenching the as-cast alloy described in step (1) in sequence to obtain a hydrogen storage alloy; The smelting current in step (1) is 100-180A, the number of times is 3-5 times, and the time is 60-120s / time; The quenching in step (2) includes sequentially performing heat treatment and rapid cooling; The holding temperature of the heat treatment is 1380-1480°C; The holding time of the heat treatment is 1 to 10 minutes; The rapid cooling is: placing the heat-treated cast alloy into liquid nitrogen or water.

2. The hydrogen storage alloy according to claim 1, characterized in that The hydrogen storage alloy is calculated according to the molar ratio: 0.40≤x≤0.50, 0.45≤y≤0.55, 0.03 <z≤0.06。 3. The hydrogen storage alloy according to claim 2, characterized in that The hydrogen storage alloy has a molar ratio of 0.50≤Ti / Cr≤1.

30.

4. The hydrogen storage alloy according to claim 3, characterized in that The hydrogen storage alloy has a molar ratio of 0.70≤Ti / Cr≤1.

20.

5. The hydrogen storage alloy according to claim 1, characterized in that The maximum hydrogen absorption capacity of the hydrogen storage alloy is ≥3.2 wt %.

6. The hydrogen storage alloy according to claim 1, characterized in that The maximum hydrogen release capacity of the hydrogen storage alloy is ≥2.3 wt%.

7. A method for preparing the hydrogen storage alloy according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: (1) preparing the ingredients according to the element ratio of the general formula of the hydrogen storage alloy, and then smelting to obtain a cast alloy; (2) encapsulating and quenching the as-cast alloy described in step (1) in sequence to obtain a hydrogen storage alloy; The smelting current in step (1) is 100-180A, the number of times is 3-5 times, and the time is 60-120s / time; The quenching in step (2) includes sequentially performing heat treatment and rapid cooling; The holding temperature of the heat treatment is 1380-1480°C; The holding time of the heat treatment is 1 to 10 minutes; The rapid cooling is: placing the heat-treated cast alloy into liquid nitrogen or water.

8. The preparation method according to claim 7, characterized in that The crystal structure of the cast alloy in step (1) includes a Laves phase.

9. The preparation method according to claim 7, characterized in that The lattice constant of the cast alloy in step (1) is 0.312 to 0.321 nm.

10. The preparation method according to claim 7, characterized in that The packaging in step (2) is as follows: wrapping the cast alloy with tantalum sheets and then packaging it in a quartz tube filled with inert gas.

11. The preparation method according to claim 10, characterized in that: The vacuum degree in the quartz tube is -0.07 to -0.09 MPa.

12. The preparation method according to claim 7, characterized in that The heating rate of the heat treatment is 10-20°C / min.

13. The preparation method according to claim 7, characterized in that After the quenching in step (2), grinding and crushing are also performed in sequence.

14. The preparation method according to claim 13, characterized in that The particle size of the crushed alloy powder is 80-200 meshes.

15. The preparation method according to claim 7, characterized in that The lattice constant of the hydrogen storage alloy is 0.306-0.311 nm.

16. The preparation method according to claim 7, characterized in that The preparation method comprises the following steps: (1) preparing the ingredients according to the element ratio of the general formula of the hydrogen storage alloy, and then smelting to obtain a cast alloy with a lattice constant of 0.312 to 0.321 nm; The smelting current is 100-180A, the time is 60-120s / time, and the number of times is 3-5 times; (2) encapsulating the cast alloy described in step (1), heating it to 1380-1480° C. at a rate of 10-20° C. / min and performing heat treatment for 1-10 min, then placing the heat-treated cast alloy in liquid nitrogen or water, and then grinding and crushing it to obtain a hydrogen storage alloy with a lattice constant of 0.306-0.311 nm; The packaging is as follows: the cast alloy is wrapped with tantalum sheets and then packaged in a quartz tube filled with inert gas.

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