A multiphase hydrogen storage alloy and a method for preparing the same

Abstract

This invention discloses a multiphase hydrogen storage alloy and its preparation method, wherein the alloy has the chemical formula La. 0.37 Nd 0.05 Sm 0.30 Mg 0.28 Ni 3.0 Al 0.1 The phase structure of this alloy is A. 7 B 23 A 2 B 7 AB 2 A multiphase structure was obtained by a two-stage vacuum induction melting method to produce a cast alloy. The cast alloy was then placed in a vacuum annealing vessel, which was evacuated to -0.1 MPa before being placed in an ultra-vacuum annealing furnace for zoned annealing heat treatment. This invention, by setting a high vacuum environment and strictly controlling the volatilization of Mg, controls the chemical composition and phase structure of the alloy, resulting in an alloy containing A. 7 B 23 A 2 B 7 AB 2 A multiphase hydrogen storage alloy with a phase structure has high discharge capacity and good cycle life. It can be used in energy storage batteries such as nickel-metal hydride batteries, which is beneficial for the storage and utilization of secondary clean energy such as wind and solar energy.

Description

A multiphase hydrogen storage alloy and its preparation method Technical Field

[0001] This invention relates to the field of hydrogen storage alloy materials technology, and in particular to a multiphase hydrogen storage alloy and its preparation method. Background Technology

[0002] With the depletion of fossil fuels such as coal and oil and the increasing severity of environmental pollution, reducing carbon emissions has become a global consensus. Many regions and countries, including the EU and Japan, have set carbon emission targets, promoted energy structure transformation, and accelerated the development and application of renewable energy. However, the instability of renewable energy sources such as wind and solar power is a significant challenge affecting their application. Energy storage batteries can provide a stable energy output for the generation and use of renewable energy, balancing electricity demand and energy supply. Therefore, energy storage batteries have enormous development potential in the field of renewable energy storage and can contribute to the widespread adoption of clean energy.

[0003] Hydrogen storage alloys have broad application prospects in hydrogen and energy storage fields. These materials can not only reversibly store and release large amounts of hydrogen, but also serve as anode materials for alkaline batteries such as nickel-metal hydride batteries, and further be used in large-scale energy storage devices. AB5-type rare-earth alloys are the first generation of commercially available hydrogen storage alloys. These alloys are easily activated and have good hydrogen absorption / desorption kinetics, but their capacity is relatively low, making it difficult to meet the requirements of large-scale energy storage. Therefore, the development of high-capacity hydrogen storage alloys is imperative. The capacity of hydrogen storage alloys is closely related to their structure and chemical composition. Rare-earth-based hydrogen storage alloys can be derived from the general formula AB5. x (2≤x≤5) indicates that there is a relationship between the theoretical hydrogen storage capacity and cycle stability of the alloy and the alloy's B / A stoichiometric ratio. High-capacity, long-life hydrogen storage alloys can be designed and developed by controlling the alloy's stoichiometric ratio and composition. This patent addresses the high requirements of energy storage batteries for electrochemical discharge capacity and cycle stability by controlling the alloy phase structure to develop novel high-capacity, long-life rare-earth hydrogen storage alloys. This aims to meet the capacity requirements of large-scale energy storage devices and promote the large-scale application of rare-earth hydrogen storage alloys in the new energy field. Summary of the Invention

[0004] This invention aims to provide a high-capacity, long-life multiphase hydrogen storage alloy with the molecular formula La. 0.37 Nd 0.0 5Sm 0.30 Mg 0.28 Ni 3.0 Al 0.1 The phase structure of this alloy is A7B. 23The invention provides a multiphase structure of type A2B7 and AB2. Simultaneously, it also provides a method for preparing this alloy, which involves sequential induction melting and partitioned annealing heat treatment. The method is simple, the process is easy to control, and the alloy phase composition is effectively controlled, ensuring the hydrogen storage performance of the alloy. The prepared hydrogen storage alloy has advantages such as easy activation, large discharge capacity, and long cycle life.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A multiphase hydrogen storage alloy with the chemical formula La 0.37 Nd 0.05 Sm 0.30 Mg 0.28 Ni 3.0 Al 0.1 The phase structure of this alloy is A7B. 23 A2B7 and AB2 type multiphase structures.

[0007] As a limitation of the present invention, the AB2 phase content is 10-20 wt%, and A7B 23 The content of the phase is 20-80 wt%, and the content of the A2B7 phase is 10-60 wt%.

[0008] This invention develops a multi-element alloy based on the traditional ternary La–Mg–Ni alloy. Traditional ternary La–Mg–Ni alloys are susceptible to oxidation and corrosion, particularly since La and Mg elements readily form products such as La(OH)3 and Mg(OH)2, which coat the electrode surface. This not only reduces the amount of active La and Mg, lowering the electrocatalytic activity of the alloy surface, but also hinders hydrogen diffusion into the alloy matrix, leading to a decrease in the alloy's discharge capacity. Rational alloy composition design is crucial for improving the alloy's cycle stability. Replacing the A-side La element with highly electronegative Nd and Sm elements can improve the alloy's corrosion resistance. Furthermore, the [A2B4] lattice in the La–Mg–Ni alloy structure contains a higher proportion of A-side elements, and these A-side elements have larger atomic radii. The [A2B4] sublattice volume is larger than the [AB5] sublattice. During hydrogen absorption and desorption, the [A2B4] and [AB5] sublattices undergo anisotropic volume expansion / contraction, generating stress within and at the boundaries of the sublattices, resulting in decreased crystal structure stability and alloy pulverization. Therefore, based on the principle of atomic selective site occupancy, sublattice volume can be adjusted through element substitution to improve sublattice matching, reduce internal stress, and enhance the structural stability of the alloy. Compared to La on the A side, Nd and Sm have smaller atomic radii, which can reduce the [A2B4] sublattice volume. Conversely, for Ni on the B side, Al has a larger atomic radius than Ni, which can increase the [AB5] sublattice volume. This brings the [A2B4] and [AB5] sublattice volumes closer together, enhancing sublattice volume matching and structural stability. On the other hand, controlling the alloy phase structure is another important method to improve the hydrogen storage performance of alloys. Rare earth hydrogen storage alloy AB... x The theoretical hydrogen storage capacity decreases with increasing B / A stoichiometric ratio, compared to A5B. 19 Type-3 alloys, with low stoichiometry, have higher discharge capacity for hydrogen storage alloys.

[0009] Furthermore, annealing heat treatment can also affect the chemical composition and hydrogen storage performance of the alloy. Therefore, this invention studies the process of partitioned annealing heat treatment. After the alloy ingot is placed in an annealing pot and vacuumed, it is then placed in a vacuum annealing furnace for annealing heat treatment, which effectively controls the chemical composition of the alloy and prevents the volatilization of low-melting-point elements in the alloy.

[0010] This invention designs a multi-element hydrogen storage alloy. Considering the alloy's corrosion resistance and anti-pulverization properties, this invention utilizes rare earth elements Nd and Sm, which have small atomic radii and high electronegativity, to replace La atoms on the A side and Al to replace Ni atoms on the B side. This promotes isotropic contraction / expansion of the [A2B4] and [AB5] sublattice volumes, improves sublattice matching, and enhances the alloy's structural stability and corrosion resistance. Furthermore, by strictly controlling the B / A stoichiometry, a hydrogen storage alloy with a B / A stoichiometry of 3.10 is designed and prepared to obtain a phase structure with a low stoichiometry, ensuring a high level of electrochemical discharge capacity and achieving the preparation of a high-capacity, long-life hydrogen storage alloy.

[0011] As a limitation of the hydrogen storage alloy preparation method of the present invention, the preparation method of the multiphase hydrogen storage alloy is carried out according to the following steps:

[0012] (1) Induction melting: according to La 0.37 Nd 0.05 Sm 0.30 Mg 0.28 Ni 3.0 Al 0.1 The chemical composition is prepared by mixing ingredients, with Mg in excess at 30 wt%. The metal raw materials are heated and melted at 1100–1300 °C; then poured and cooled to obtain a cast alloy.

[0013] (2) Zoned annealing heat treatment: After sealing the as-cast alloy, place it in an ultra-vacuum annealing furnace at 5×10⁻⁶ ℃. -3 ~2×10 2 The target alloy was obtained by annealing under vacuum conditions.

[0014] As a limitation of the preparation method of the present invention, the partitioned annealing heat treatment process is carried out in the following steps sequentially:

[0015] (S1) Increase the temperature from room temperature to 600℃ at a rate of 5℃ / min, and hold at 600℃ for 2 hours;

[0016] (S2) Increase the temperature from 600℃ to 800℃ at a rate of 2℃ / min and hold for 2 hours;

[0017] (S3) Increase the temperature from 800℃ to 980~1000℃ at 1℃ / min, and keep it at the target temperature for 8~10h;

[0018] (S4) Cool to room temperature with the furnace.

[0019] As a second limitation of the preparation method of the present invention, in step (2), the annealed heat-treated sample is sealed in a vacuum annealing vessel, and after the annealing vessel is pumped to -0.1 MPa, it is placed in an ultra-vacuum annealing furnace for annealing heat treatment.

[0020] This invention also has a limitation: the prepared hydrogen storage alloy has a maximum discharge capacity greater than 390 mAh / g, a capacity retention rate greater than 90% after 100 cycles, and a capacity retention rate greater than 80% after 200 cycles.

[0021] The chemical composition of this invention is crucial for preparing high-capacity, long-life hydrogen storage alloys, as it affects the alloy's performance. Based on the traditional ternary La–Mg–Ni alloy, this invention replaces La on the A-side with Nd and Sm, and Ni on the B-side with Al. Compared to La, Nd and Sm have higher electronegativity, which improves the alloy's corrosion resistance. Furthermore, Nd and Sm have smaller atomic radii than La, reducing the [A2B4] sublattice volume, while Al has a larger atomic radius than Ni, increasing the [AB5] sublattice volume. After replacing La on the A-side and Ni on the B-side, the [A2B4] and [AB5] sublattice volumes in the alloy structure tend to be consistent, promoting sublattice volume matching and improving the alloy's structural and cycling stability. On the other hand, strictly controlling the B / A stoichiometric ratio is beneficial for obtaining a low-stoichiometric alloy with a large theoretical hydrogen storage capacity, ensuring the alloy's discharge capacity.

[0022] The annealing heat treatment of this invention is crucial for controlling the chemical composition and phase structure of the alloy. Placing the as-cast alloy in a vacuum annealing vessel and sealing it under vacuum for annealing heat treatment effectively controls the volatilization of the low-melting-point element Mg and avoids the formation of the AB5-type phase structure with low discharge capacity. Annealing heat treatment conditions, including temperature, time, and heating / cooling rates, directly affect the peritectic reaction and phase transformation process of the alloy, and reaction conditions must be strictly controlled. In the initial stage of heat treatment, the temperature is raised from room temperature to 600℃ to reach the suitable temperature for Mg diffusion and promote the uniform distribution of Mg in the alloy. A relatively fast heating rate of 5℃ / min is used in this stage to reduce Mg volatilization. Holding at this temperature for 2 hours allows Mg to reach equilibrium in the system. In the second heating stage, a heating rate of 2℃ / min is designed to promote the dissociation of chemical particles from the reaction phase and their transformation into product phase grains through peritectic reaction. If the heating rate is greater than 2℃ / min in this stage, the reaction will be incomplete, affecting the uniformity of the alloy composition. If it is less than 2℃ / min, the grain nucleation rate will decrease. Holding at this temperature for 1 hour allows for sufficient grain growth and improves the alloy structure. Crystallinity; when the temperature rises to the target temperature of 980-1000℃, if it is below 980℃, it is not easy to form an A2B7 type phase structure with good cycle life; if it is above 1000℃, it is easy to form an AB5 type phase structure with low discharge capacity. The peritectic reaction requires sufficient mass transfer time. In the final heating stage of the heat treatment process of this invention, a small heating rate of 1℃ / min is used to allow the phase structure in the alloy to slowly dissociate and react. When the holding time at the target temperature is less than 8h, the solid phase diffusion is incomplete, the alloy structure is unevenly distributed, and it is difficult to obtain the alloy with uniform structure described in this invention; while when the holding time is greater than 10h, it will cause a co-deposition reaction of the product grains and form a non-superlattice AB5 type phase structure.

[0023] The beneficial effects achieved by adopting the above-mentioned technical solution of the present invention are as follows:

[0024] 1. The A7B provided by this invention 23 A2B7 and AB2 type multiphase hydrogen storage alloys have large discharge capacity, strong structural stability, and good cycle stability.

[0025] 2. The A7B provided by this invention 23 The preparation methods of A2B7 and AB2 type multiphase hydrogen storage alloys are simple and easy to control. The phase structure formation can be well controlled during the preparation process, and the resulting hydrogen storage alloy has a uniform microstructure, which ensures the hydrogen storage performance of the hydrogen storage alloy.

[0026] 3. The A7B provided by this invention 23The A2B7 and AB2 type multiphase hydrogen storage alloys have a reasonable element matching. The alloys prepared by the method of this invention achieve control of the specific phase structure composition, and finally obtain multiphase hydrogen storage alloys with large discharge capacity and long cycle life. The alloys prepared by this invention have a maximum discharge capacity of more than 390 mAh / g, a capacity retention rate of more than 90% after 100 cycles, and a capacity retention rate of more than 80% after 200 cycles.

[0027] This invention is applicable to the preparation of A7B 23 A2B7 and AB2 type multiphase hydrogen storage alloys are further used as electrode materials for nickel-metal hydride batteries for large-scale energy storage batteries.

[0028] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. Attached Figure Description

[0029] Figure 1 shows the XRD patterns of the hydrogen storage alloys prepared in Examples 1 and 2 of this invention;

[0030] Figure 2 shows the activation curves of the hydrogen storage alloys prepared in Examples 1 and 2 of this invention;

[0031] Figure 3 shows the cycle life of the hydrogen storage alloys prepared in Examples 1 and 2 of this invention. Detailed Implementation

[0032] Unless otherwise specified, the preparation methods described in the following examples are all existing preparation methods, and the raw materials are all obtained commercially unless otherwise specified.

[0033] Example 1

[0034] This embodiment prepares a multiphase hydrogen storage alloy, the as-cast alloy having the chemical formula La. 0.37 Nd 0.05 Sm 0.30 Mg 0.28 Ni 3.0 Al 0.1 The preparation process is carried out in the following order:

[0035] (1) Ingredients

[0036] According to the alloy chemical formula ratio, weigh out the metals La, Sm, Nd, Mg, Ni, and Al. Considering that Mg has a low melting point and is easily volatile, Mg is added in excess by 30 wt%.

[0037] (2) Induction melting

[0038] The above-mentioned metal is heated and melted at a temperature of 1100–1300°C; poured and cooled to obtain an alloy ingot.

[0039] The as-cast alloy was placed in a vacuum annealing vessel, evacuated to -0.1 MPa, sealed, and placed in an ultra-vacuum annealing furnace at 5 × 10⁻⁶ ℃. -3 ~2×10 2 The target alloy was obtained by annealing heat treatment under vacuum conditions.

[0040] In this step, the partitioned annealing heat treatment process is carried out in the following order:

[0041] (S1) Increase the temperature from room temperature to 600℃ at a rate of 5℃ / min, and hold at 600℃ for 2 hours;

[0042] (S2) Increase the temperature from 600℃ to 800℃ at a rate of 2℃ / min and hold for 2 hours;

[0043] (S3) Increase the temperature from 800℃ to 980℃ at a rate of 1℃ / min, and hold at the target temperature for 8 hours;

[0044] (S4) Cool to room temperature with the furnace.

[0045] The prepared alloy was mechanically pulverized and ground through a 400-mesh sieve. The alloy powder was then subjected to X-ray diffraction (XRD) testing, and the results are shown in Figure 1. From the position and intensity characteristics of the diffraction peaks in the XRD pattern, it can be determined that the alloy is a multiphase hydrogen storage alloy, containing AB2 type (MgCu4Sn) with a content of 23.5 wt%, and A7B... 23 Type A2B7 contains 21.5 wt%, while Type A2B7 contains 55.0 wt%.

[0046] Example 2

[0047] This embodiment describes a multiphase hydrogen storage alloy, with the as-cast alloy having the chemical formula La. 0.37 Nd 0.05 Sm 0.30 Mg 0.28 Ni 3.0 Al 0.1 The preparation process is carried out in the following order:

[0048] (1) Ingredients

[0049] According to the alloy chemical formula ratio, weigh out the metals La, Sm, Nd, Mg, Ni, and Al. Considering that Mg has a low melting point and is easily volatile, Mg is added in excess by 30 wt%.

[0050] (2) Induction melting

[0051] The above metal is heated and melted at a temperature of 1100–1300°C; poured and cooled to obtain alloy ingot A;

[0052] The as-cast alloy was placed in a vacuum annealing vessel, evacuated to -0.1 MPa, sealed, and placed in an ultra-vacuum annealing furnace at 5 × 10⁻⁶ ℃. -3 ~2×10 2 The target alloy was obtained by annealing heat treatment under vacuum conditions.

[0053] The partitioned annealing heat treatment process is carried out in the following order:

[0054] (S1) Increase the temperature from room temperature to 600℃ at a rate of 5℃ / min, and hold at 600℃ for 2 hours;

[0055] (S2) Increase the temperature from 600℃ to 800℃ at a rate of 2℃ / min and hold for 2 hours;

[0056] (S3) Increase the temperature from 800℃ to 1000℃ at a rate of 1℃ / min, and hold at the target temperature for 10 hours;

[0057] (S4) Cool to room temperature with the furnace.

[0058] The prepared alloy was mechanically pulverized and ground through a 400-mesh sieve. The alloy powder was then subjected to XRD analysis, and the results are shown in Figure 1. From the diffraction peak positions and intensity characteristics in the XRD pattern, it can be determined that this alloy is a multiphase hydrogen storage alloy, containing AB2 type (MgCu4Sn) at a content of 14.5 wt%, and A7B... 23 Type A, with a content of 75.0 wt%, and Type A2B7, with a content of 10.5 wt%.

[0059] Example 3 Performance Test

[0060] The A7B prepared in Examples 1-2 23 The surface oxide layer of A2B7 and AB2 type multiphase hydrogen storage alloys was removed, mechanically crushed and ground, and sieved (200-400 mesh sieve). The resulting sheets were then pressed into 1 cm diameter plates under 15 MPa pressure to serve as the negative electrode in a nickel-metal hydride battery half-cell. Nickel hydroxide / nickel sulfide was used as the positive electrode, and a 6 mol / L KOH aqueous solution was used as the electrolyte. The electrochemical performance of the negative electrode, including electrochemical capacity and cycle life, was tested.

[0061] The maximum discharge capacity of the hydrogen storage alloys described in Examples 1 and 2 is shown in Figure 2. In Examples 1 and 2, the maximum discharge capacity was reached after 2 and 3 charge / discharge cycles, respectively, at a charge / discharge current density of 0.2C. The maximum discharge capacities were 392.2 mAh / g and 408.5 mAh / g, respectively. After the hydrogen storage alloy negative electrode was activated and reached its maximum discharge capacity, the battery cycle performance was tested at a charge / discharge current of 1C. The discharge capacity of the hydrogen storage alloy electrode was recorded after different numbers of cycles, and the capacity retention rate S of the hydrogen storage alloy electrode was calculated according to the following formula. n value:

[0062]

[0063] Among them, C n C represents the discharge capacity of the alloy electrode in the nth cycle. max This represents the maximum discharge capacity of the alloy electrode.

[0064] Figure 3 shows the A7B prepared in Examples 1-2. 23 The capacity retention rates of multiphase hydrogen storage alloys of types A2B7 and AB2 under different number of cycles were as follows: after 100 electrochemical cycles, the capacity retention rates of Examples 1 and 2 were 92.6% and 90.7%, respectively; after 200 cycles, the capacity retention rates of Examples 1 and 2 were 85.3% and 83.7%, respectively.

[0065] Example 4 Comparative Example

[0066] To better illustrate the A7B provided by this invention 23 Electrochemical performance of A2B7 and AB2 type multiphase hydrogen storage alloys: This embodiment compares the performance of some existing hydrogen storage alloys, and the induction melting process in the preparation process is the same as in this embodiment 1.

[0067] Group A: Hydrogen storage alloy composition is La 0.64 Sm 0.07 Nd 0.08 Mg 0.21 Ni 3.57 Al 0.10 The preparation process involves melting metals La, Sm, Nd, Mg, Ni, and Al in an induction melting furnace under an argon atmosphere. After annealing (the annealing process involves heating from room temperature to 600℃ at a rate of 4℃ / min, then to 1010℃ at a rate of 2℃ / min, holding at this temperature for 24 hours, and subsequently cooling to room temperature with the furnace), a crystal structure of type A5B is obtained. 19 With a superlattice structure, this hydrogen storage alloy has a maximum discharge capacity of 378.1 mAh / g and a capacity retention of 76.6% after 200 electrochemical cycles.

[0068] Group B: Hydrogen storage alloy with La composition 0.60 Nd 0.15 Mg 0.25 Ni 3.20 Mn 0.1The alloy was prepared by melting La, Nd, Mg, Ni, and Mn in an induction furnace under an argon atmosphere. After annealing (the annealing process was as follows: the temperature was increased from room temperature to 600℃ at a rate of 4℃ / min, then increased to 975℃ at a rate of 2℃ / min, and held at this temperature for 14 hours, followed by furnace cooling to room temperature), a single-phase alloy with a crystal structure of type A2B7 was obtained. Electrochemical performance tests showed that the maximum discharge capacity of the alloy was 385.0 mAh / g, and the capacity retention rate was 78.6% after 200 electrochemical cycles.

[0069] Group C: Hydrogen storage alloy with La composition 0.60 Nd 0.20 Mg 0.20 Ni 3.26 Using La 0.6 Nd 0.2 Mg 0.2 Ni 3.65 The LaMgNi4 precursor was prepared by powder sintering (the powder sintering process was as follows: heating from room temperature to 600℃ at a rate of 5℃ / min, holding at that temperature for 1 hour, then heating to 700℃ / 800℃ at a rate of 1℃ / min, holding at the corresponding temperature for 1 hour, continuing to heat to 900℃ at a rate of 1℃ / min, and holding at that temperature for 96 hours, finally cooling to room temperature in the furnace). The alloy phase structure composition was A2B7 and A7B. 23 The phase structure and electrochemical performance test results show that the maximum discharge capacity of the alloy is 353 mAh / g, and the capacity retention rate is 89.1% after 100 cycles.

[0070] As can be seen from the above groups A and C, although the alloys in group A have the same constituent elements and similar preparation methods as those in this invention, the maximum discharge capacity and cycle capacity retention rate of the alloys obtained are lower than those of the alloys provided in this invention due to differences in alloy element ratios and phase structures. The alloys in group B have similar preparation methods to those in this invention, but the alloys are different from those in this invention, and the phase structures of the alloys obtained are different from those in this invention, resulting in lower maximum discharge capacity and cycle capacity retention rates. The alloy crystal structure in group C is similar to that in this invention, but due to differences in alloy composition and preparation methods, the hydrogen storage performance of the resulting alloys is different from that of the alloys in this invention, and the maximum discharge capacity and capacity retention rate are lower than those of the alloys in this invention.

[0071] As can be seen from the comparative examples, the A7B provided by this invention... 23The multiphase hydrogen storage alloys of type A2B7 and AB2 exhibit better electrochemical hydrogen storage performance, mainly due to the chemical and structural composition of the alloys in this invention. By strictly controlling the preparation conditions, a vacuum induction melting process and a strictly vacuumed and sealed partitioned annealing heat treatment process were adopted. The holding temperature, holding time, and other conditional parameters related to the alloy composition and phase structure formation were strictly controlled to eliminate internal stress, suppress alloy defects, and make the grains more complete and uniform. This resulted in an alloy with a uniform microstructure and a specific structure. The alloys obtained by this invention have excellent electrochemical hydrogen storage performance, with large electrochemical discharge capacity and good cycle stability, making them suitable for application in large energy storage batteries such as nickel-metal hydride batteries.

[0072] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A multiphase hydrogen storage alloy, characterized in that, Its chemical formula is La 0.37 Nd 0.05 Sm 0.30 Mg 0.28 Ni 3.0 Al 0.1 The phase structure of this alloy is A7B. 23 A2B7 and AB2 type multiphase structures; the AB2 phase content is 10~20 wt%, A7B 23 The phase content is 20~80wt%, and the A2B7 phase content is 10~60wt%; the preparation method of the multiphase hydrogen storage alloy is carried out according to the following steps: (1) Induction melting: according to La 0.37 Nd 0.05 Sm 0.30 Mg 0.28 Ni 3.0 Al 0.1 Chemical composition is prepared, with Mg in excess of 30wt%. The metal raw materials are heated and melted at 1100~1300℃; poured and cooled to obtain the cast alloy; (2) Partial annealing heat treatment: the cast alloy is sealed and placed in an ultra-vacuum annealing furnace, and heated at 5×10 -3 ~2×10 2 The target alloy is obtained by annealing under vacuum conditions. The partitioned annealing heat treatment process is carried out in the following steps: (S1) heating from room temperature to 600℃ at 5℃ / min and holding at 600℃ for 2h; (S2) heating from 600℃ to 800℃ at 2℃ / min and holding for 2h; (S3) heating from 800℃ to 980~1000℃ at 1℃ / min and holding at the target temperature for 8~10h; (S4) cooling to room temperature in the furnace.

2. The multiphase hydrogen storage alloy according to claim 1, characterized in that, In step (2), the annealed heat-treated sample is sealed in a vacuum annealing vessel. After the annealing vessel is evacuated to -0.1 MPa, it is placed in an ultra-vacuum annealing furnace for annealing heat treatment.

3. The multiphase hydrogen storage alloy according to claim 1, characterized in that, The prepared hydrogen storage alloy has a maximum discharge capacity greater than 390 mAh / g, and the capacity retention rate is higher than 90% after 100 cycles and higher than 80% after 200 cycles.

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