A high-power AB2-AB5 dual-phase La-Mg-Ni-based hydrogen storage alloy and a preparation method thereof

Abstract

The application discloses a high-power AB3 type AB2-AB5 dual-phase La-Mg-Ni-based hydrogen storage alloy and a preparation method thereof, and has a dual-phase structure of an AB5 type LaNi5 phase and an AB2 type LaMgNi4 phase. Unlike the AB3 type La-Mg-Ni-based hydrogen storage alloy in the past, which is mainly of a superlattice alloy phase formed by stacking [A2B4] and [AB5] sublattices, the AB3 type alloy in the application is composed of independent AB2 and AB5 alloy phases, which can not only avoid the service life problem caused by the structural mismatch of two sublattices in the same alloy phase in the hydrogen absorption and release process, but also avoid the adverse effect of mutual restriction on the rapid charge and discharge. Meanwhile, the grain boundary between the AB2 and AB5 alloy phases can further provide sufficient channels for the rapid hydrogen absorption and release of the alloy, which is beneficial to the high-rate discharge performance.

Description

Technical Field

[0001] This invention relates to an AB3 type AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloy, belonging to the field of hydrogen storage alloy technology. Background Technology

[0002] With the rapid depletion of fossil fuels and the increasing severity of environmental pollution, hydrogen energy, as a clean and sustainable new energy source, has a vast market potential in the 21st century. Nickel-metal hydride (Ni / MH) batteries, using hydrogen storage alloys as anode materials, occupy an important position in energy storage and conversion due to their advantages such as high power, good safety, and long lifespan. The development of anode materials is a crucial aspect of Ni / MH battery development. In recent years, La-Mg-Ni based hydrogen storage alloys have emerged as one of the most promising anode materials for Ni / MH batteries due to their excellent comprehensive electrochemical hydrogen storage performance.

[0003] AB 3～4 La-Mg-Ni based hydrogen storage alloys typically feature a superpacked alloy phase as the main phase. This type of alloy phase is formed by stacking [A2B4] and [AB5] sublattices along the c-axis in different proportions, resulting in AB3 phase (1:1), A2B7 phase (1:2), and A5B... 19 The super-stacked structure alloys formed by the AB2 and AB5 alloys (1:3 ratio) possess both the high capacity of the AB2 alloy and the superior activation performance of the AB5 alloy. However, traditional La-Mg-Ni based alloys with super-stacked alloy phases as the main phase suffer from structural collapse due to their complex stacking structure and the asynchronous hydrogen absorption and desorption of the [A2B4] and [AB5] sublattices during charge and discharge, leading to rapid capacity decay. Furthermore, the mutual restriction of contraction and expansion between the [A2B4] and [AB5] sublattices prevents the full realization of high-rate discharge performance, which needs further improvement. Therefore, if the [A2B4] and [AB5] sublattices can exist independently in the alloy as AB2 and AB5 alloy phases, it can avoid the lifespan problem caused by the structural mismatch of the two sublattices in the same alloy phase during hydrogen absorption and desorption, and also avoid the adverse effects of their mutual restriction on rapid charge and discharge. At the same time, the grain boundaries between the AB2 and AB5 alloy phases can further provide sufficient channels for the alloy to rapidly absorb and desorb hydrogen, which is beneficial to high-rate discharge performance. However, on the phase diagram, the elemental composition of phases AB2 and AB5 spans across phases AB3, A2B7, and A5B. 19 Equally, it is difficult to avoid the appearance of the above superlattice alloy phases, or even their existence as the main alloy phase in AB. 3～4In La-Mg-Ni based alloys, the preparation of AB5-AB2 biphase La-Mg-Ni based alloys presents certain difficulties. Currently, only a small number of AB2-type alloys containing both AB5 and AB2 phases exist. However, the B-side content of AB2-type alloys is low, resulting in insufficient catalytic activity and a low plateau voltage, which adversely affects reversible charge-discharge (hydrogen absorption and desorption) and leads to poor rapid discharge capability. In general, AB... 3～4 The AB5-AB2 biphase La-Mg-Ni based hydrogen storage alloy is likely to be used as a negative electrode material for high-power, long-life nickel-metal hydride batteries, but there are currently no related reports. Summary of the Invention

[0004] This invention provides an AB3-type AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloy and its preparation method by designing the elemental composition, controlling the volatilization of Mg, and adjusting the heat treatment process.

[0005] The technical solution of the present invention is: an AB3 type AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloy, having a dual-phase structure of AB5 type LaNi5 phase and AB2 type LaMgNi4 phase.

[0006] Preferably, the LaNi5 phase content is 46.3 wt% to 47.3 wt%.

[0007] Preferably, the expression for this hydrogen storage alloy is La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.14 .

[0008] Preferably, the expression for this hydrogen storage alloy is La 0.26 Nd 0.22 Sm 0.18 Mg 0.34 Ni 2.77 Al 0.13 .

[0009] The preparation method of the above-mentioned AB3 type AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloy includes:

[0010] (1) Batching and smelting of alloys: Select elemental metals, according to La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.15 The chemical composition was prepared by batching, with La in excess of 3wt%, Sm in excess of 5%, and Mg in excess of 25wt%, and alloy ingots were prepared by medium-frequency induction melting.

[0011] Or, according to La0.26 Nd 0.22 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.15 The chemical composition was prepared by batching, with La and Nd elements in excess of 3wt%, Sm element in excess of 5%, and Mg element in excess of 25wt%. The alloy ingot was prepared by medium-frequency induction melting.

[0012] (2) Heat treatment: Take the smelted alloy ingot, put it into a sealed nickel shell container, and then place the nickel shell containing the alloy ingot in a vacuum tube furnace for step-by-step heat treatment under an argon atmosphere.

[0013] Preferably, the sealed nickel-cased container satisfies a ratio of alloy ingot mass to container cavity volume of 6–8 g : 10–14 cm³. 3 .

[0014] Preferably, the specific heat treatment process is as follows: Argon gas is introduced, and the temperature is increased at a rate of 5 K / min to reach 873 K. Then, the temperature is increased at a rate of 1 K / min to 1123-1173 K and held for 8 hours. Then, the temperature is decreased at a rate of 1 K / min to 973 K and held for another 8 hours. After the heat treatment is completed, the temperature is decreased at a rate of 5 K / min to 773 K and cooled to room temperature with the furnace. Throughout the entire heat treatment process, the internal pressure of the quartz tube is maintained between -0.02 MPa and 0.02 MPa.

[0015] Preferably, the quartz tube of the vacuum tube furnace is washed with argon gas multiple times before heat treatment to completely remove the internal oxygen. Then, under vacuum, the temperature is raised from room temperature to 373K at a rate of 5K / min and held for 1 hour to remove residual water vapor in the quartz tube.

[0016] Compared with existing technologies, the advantages of this invention are as follows: Unlike previous AB3-type La-Mg-Ni based hydrogen storage alloys with superlattice alloy phases formed by stacking [A2B4] and [AB5] sublattices as the main phase, the AB3-type alloy in this invention is composed of independent AB2 and AB5 alloy phases. This avoids the lifetime problems caused by structural mismatch between the two sublattices in the same alloy phase during hydrogen absorption and desorption, and also avoids the adverse effects of their mutual restriction on rapid charge and discharge. Simultaneously, the grain boundaries between the AB2 and AB5 alloy phases can further provide sufficient channels for the alloy's rapid hydrogen absorption and desorption, which is beneficial for high-rate discharge performance. Attached Figure Description

[0017] Figure 1 The images show the XRD patterns and refined XRD patterns of the AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloys prepared in Examples 1 to 4 of this invention, where a: Example 1, b: Example 2, c: Example 3, and d: Example 4.

[0018] Figure 2 The graph shows the relationship between discharge capacity and cycle number during the first seven weeks of activation of the AB2-AB5 biphase La-Mg-Ni based hydrogen storage alloys prepared in Examples 1-4 of this invention.

[0019] Figure 3 The graphs show the relationship between capacity retention and cycle number of the AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloys prepared in Examples 1-4 of this invention.

[0020] Figure 4 The high-rate discharge (HRD) curves of the AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloys prepared in Examples 1-4 of this invention are shown. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] The following examples include four alloys: La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.14 Annealing at -850℃, La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.14 Annealing at -900℃, La 0.26 Nd 0.22 Sm 0.18 Mg 0.34 Ni 2.77 Al 0.13 Annealing at -850℃, La 0.26 Nd 0.22 Sm 0.18 Mg 0.34 Ni 2.77 Al 0.13 Annealing at -900℃.

[0023] AB 3～4La-Mg-Ni based hydrogen storage alloys typically feature a super-stacked alloy phase as the main phase. This type of alloy phase is formed by stacking [A2B4] and [AB5] sublattices along the c-axis in different proportions, possessing both the high capacity of AB2 alloys and the rapid activation of AB5 alloys. However, due to the complex stacking structure and the asynchronous hydrogen absorption and desorption of the [A2B4] and [AB5] sublattices during charging and discharging, these alloys are prone to structural collapse during repeated charging and discharging (hydrogen absorption and desorption), leading to rapid capacity decay. Furthermore, the mutual restriction of contraction and expansion between the [A2B4] and [AB5] sublattices prevents the full utilization of high-rate discharge performance, which needs further improvement. This invention, through designing the elemental composition, controlling the volatilization of Mg, and adjusting the heat treatment process, prepared an AB3-type La-Mg-Ni based alloy composed of independent AB2 and AB5 alloy phases. Unlike typical AB3 alloys, this invention does not contain the superlattice alloy phase (AB5) formed by stacking [A2B4] and [AB5] sublattices. 3～4 The combination of AB2 and AB5 phases not only avoids the lifetime issues caused by structural mismatch between the two sublattices within the same alloy phase during hydrogen absorption and desorption, but also avoids the adverse effects of their mutual restriction on rapid charge and discharge. Furthermore, the grain boundaries between the AB2 and AB5 alloy phases provide ample channels for the alloy's rapid hydrogen absorption and desorption, which is beneficial for high-rate discharge performance.

[0024] Example 1

[0025] A method for preparing a high-power AB3-type AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloy, comprising:

[0026] (1) Using elemental metals La, Sm, Mg, Ni, and Al as raw materials, according to La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.15 The chemical composition was determined by batching, with La in excess at 3 wt%, Sm in excess at 5 wt%, and Mg in excess at 25 wt%. The resulting as-cast alloy was then prepared using medium-frequency induction melting. ICP testing showed that the actual elemental composition of the alloy ingot was: La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.14 .

[0027] (2) In order to control the amount of Mg volatilization, the heat treatment process of the alloy ingot needs to be carried out in a nickel shell. The preparation process of the nickel shell is referred to in patent CN112501475 A.

[0028] (3) Take 8g of La 0.48 Sm0.18 Mg 0.34 Ni 2.75 Al 0.14 The alloy ingot is first prepared by removing the oxide layer from its surface with sandpaper. Then, the alloy block is inserted into the nickel shell through an opening, and a 0.2cm section is folded and hammered at the opening to ensure a tight seal. Finally, a spot welding machine is used to repeatedly weld and seal the folded areas of the nickel shell, resulting in an ingot approximately 4.0cm long, 2.3cm high, 1.8cm wide at the base, and 14cm in volume. 3 A triangular prism shape.

[0029] (4) A step-by-step heat treatment was performed using a vacuum tube furnace. First, the sealed nickel shell containing the alloy was placed flat in the corundum crucible and pushed to the middle of the tube furnace for step-by-step heat treatment. The specific steps were as follows: the two ends of the quartz tube in the sealed tube furnace were purged with argon gas and then vacuumed three times, with the last purging with argon gas to -0.1 MPa; then the temperature was increased at a rate of 5 K / min to reach 873 K, then increased to 1123 K at a rate of 1 K / min and held for 8 hours, then the temperature was decreased to 973 K at a rate of 1 K / min and held for another 8 hours. Throughout the heat treatment process, the internal pressure of the quartz tube was maintained between -0.02 MPa and 0.02 MPa. After the heat treatment, the temperature was decreased to 773 K at a rate of 5 K / min and then cooled to room temperature with the furnace.

[0030] (5) The heat-treated sample was removed from the nickel shell, the surface oxide layer was removed, and it was mechanically crushed and ground. Alloy powder with a thickness of less than 37 μm was taken and subjected to XRD testing. The obtained data was then refined using Maud software. The XRD pattern of the alloy and the refined pattern are shown below. Figure 1 As shown, the results indicate that the alloy product contains AB5-type LaNi5 phase and AB2-type LaMgNi4 phase, with the AB5 phase accounting for 46.5 wt% and the A2B4 phase accounting for 53.5 wt%. Alloy powder with an average particle size of 37–74 μm was used as the negative electrode active material for the battery. It was uniformly mixed with nickel hydroxide powder at a ratio of 1:5 and cold-pressed to prepare a nickel-metal hydride battery negative electrode sheet. Nickel hydroxide was used as the counter electrode, and 6M KOH aqueous solution was used as the electrolyte to prepare an open-type dual-electrode simulated experimental battery for electrochemical performance testing. Before the test, the battery was immersed in the electrolyte for 24 hours to ensure sufficient wetting of the separator. Subsequently, the electrochemical performance of the battery was tested using a Blue Electric CT-3002A high-precision battery tester. Figure 2 This is the activation curve of the alloy electrode for the first 7 weeks. The alloy electrode reached its maximum discharge capacity of 314 mAh g in the first week. -1 ; Figure 3 The figure shows the cycle stability curve of the alloy electrode within 100 cycles. The capacity retention rate of the alloy electrode in the 100th cycle is 75.9%. Figure 4The high-rate discharge performance curve of the alloy electrode is shown when the discharge current density is 1500 mAg. -1 At that time, the high-rate discharge performance of the alloy electrode was 67.4%.

[0031] Example 2

[0032] A method for preparing a high-power AB3-type AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloy, comprising:

[0033] (1) Using elemental metals La, Sm, Mg, Ni, and Al as raw materials, according to La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.15 The chemical composition was prepared by mixing ingredients, with La in excess of 3wt%, Sm in excess of 5%, and Mg in excess of 25wt%, and then a cast alloy was prepared by medium-frequency induction melting.

[0034] (2) In order to control the amount of Mg volatilization, the heat treatment process of the alloy ingot needs to be carried out in a nickel shell.

[0035] (3) Take 8g of La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.14 The alloy ingot is first prepared by removing the oxide layer from its surface with sandpaper. Then, the alloy block is inserted into the nickel shell through an opening, and a 0.2cm section is folded and hammered at the opening to ensure a tight seal. Finally, a spot welding machine is used to repeatedly weld and seal the folded areas of the nickel shell, resulting in an ingot approximately 4.0cm long, 2.3cm high, 1.8cm wide at the base, and 14cm in volume. 3 A triangular prism shape.

[0036] (4) A step-by-step heat treatment was performed using a vacuum tube furnace. First, the sealed nickel shell containing the alloy was placed flat in the corundum crucible and pushed to the middle of the tube furnace for step-by-step heat treatment. The specific steps were as follows: the two ends of the quartz tube in the sealed tube furnace were purged with argon gas and then vacuumed three times, with the last purging with argon gas to -0.1 MPa; then the temperature was increased at a rate of 5 K / min to 873 K, then increased to 1173 K at a rate of 1 K / min and held for 8 hours, then the temperature was decreased to 973 K at a rate of 1 K / min and held for another 8 hours. Throughout the heat treatment process, the internal pressure of the quartz tube was maintained between -0.02 MPa and 0.02 MPa. After the heat treatment, the temperature was decreased to 773 K at a rate of 5 K / min and then cooled to room temperature with the furnace.

[0037] (5) The heat-treated sample was removed from the nickel shell, the surface oxide layer was removed, and it was mechanically crushed and ground. Alloy powder with a thickness of less than 37 μm was taken and subjected to XRD testing. The obtained data was then refined using Maud software. The XRD pattern of the alloy and the refined pattern are shown below. Figure 1 As shown, the results indicate that the alloy product contains AB5-type LaNi5 phase and AB2-type LaMgNi4 phase, with the AB5 phase accounting for 46.8 wt% and the A2B4 phase accounting for 53.2 wt%. Alloy powder with an average particle size of 37–74 μm was used as the negative electrode active material for the battery. It was uniformly mixed with nickel hydroxide powder at a ratio of 1:5 and cold-pressed to prepare a nickel-metal hydride battery negative electrode sheet. Nickel hydroxide was used as the counter electrode, and 6M KOH aqueous solution was used as the electrolyte to prepare an open-type dual-electrode simulated experimental battery for electrochemical performance testing. Before the test, the battery was immersed in the electrolyte for 24 hours to ensure sufficient wetting of the separator. Subsequently, the electrochemical performance of the battery was tested using a Blue Electric CT-3002A high-precision battery tester. Figure 2 This is the activation curve of the alloy electrode for the first 7 weeks. The alloy electrode reached its maximum discharge capacity of 322 mAh g in the first week. -1 ; Figure 3 The cycling stability curves of the alloy electrode are shown within 100 cycles. The capacity retention rate of the alloy electrode in the 100th cycle is 75.1%. Figure 4 The high-rate discharge performance curve of the alloy electrode is shown when the discharge current density is 1500 mAg. -1 At that time, the high-rate discharge performance of the alloy electrode was 68.7%.

[0038] Example 3

[0039] A method for preparing a high-power AB3-type AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloy, comprising:

[0040] (1) Using elemental metals La, Nd, Sm, Mg, Ni, and Al as raw materials, according to La 0.26 Nd 0.22 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.15 The chemical composition was determined by batching, with La and Nd in excess of 3 wt%, Sm in excess of 5 wt%, and Mg in excess of 25 wt%. The resulting as-cast alloy was then prepared using medium-frequency induction melting. ICP testing showed that the actual elemental composition of the alloy ingot was: La 0.26 Nd 0.22 Sm 0.18 Mg 0.34 Ni 2.77 Al 0.13 .

[0041] (2) In order to control the amount of Mg volatilization, the heat treatment process of the alloy ingot needs to be carried out in a nickel shell.

[0042] (3) Take 8g of La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.14 The alloy ingot is first prepared by removing the oxide layer from its surface with sandpaper. Then, the alloy block is inserted into the nickel shell through an opening, and a 0.2cm section is folded and hammered at the opening to ensure a tight seal. Finally, a spot welding machine is used to repeatedly weld and seal the folded areas of the nickel shell, resulting in an ingot approximately 4.0cm long, 2.3cm high, 1.8cm wide at the base, and 14cm in volume. 3 A triangular prism shape.

[0043] (4) A step-by-step heat treatment was performed using a vacuum tube furnace. First, the sealed nickel shell containing the alloy was placed flat in the corundum crucible and pushed to the middle of the tube furnace for step-by-step heat treatment. The specific steps were as follows: the two ends of the quartz tube in the sealed tube furnace were purged with argon gas and then vacuumed three times, with the last purging with argon gas to -0.1 MPa; then the temperature was increased at a rate of 5 K / min to reach 873 K, then increased to 1123 K at a rate of 1 K / min and held for 8 hours, then the temperature was decreased to 973 K at a rate of 1 K / min and held for another 8 hours. Throughout the heat treatment process, the internal pressure of the quartz tube was maintained between -0.02 MPa and 0.02 MPa. After the heat treatment, the temperature was decreased to 773 K at a rate of 5 K / min and then cooled to room temperature with the furnace.

[0044] (5) The heat-treated sample was removed from the nickel shell, the surface oxide layer was removed, and it was mechanically crushed and ground. Alloy powder with a thickness of less than 37 μm was taken and subjected to XRD testing. The obtained data was then refined using Maud software. The XRD pattern of the alloy and the refined pattern are shown below. Figure 1 As shown, the results indicate that the alloy product contains AB5-type LaNi5 phase and AB2-type LaMgNi4 phase, with the AB5 phase accounting for 46.3 wt% and the A2B4 phase accounting for 53.7 wt%. Alloy powder with an average particle size of 37–74 μm was used as the negative electrode active material for the battery. It was uniformly mixed with nickel hydroxide powder at a ratio of 1:5 and cold-pressed to prepare a nickel-metal hydride battery negative electrode sheet. Nickel hydroxide was used as the counter electrode, and 6M KOH aqueous solution was used as the electrolyte to prepare an open-type dual-electrode simulated experimental battery for electrochemical performance testing. Before the test, the battery was immersed in the electrolyte for 24 hours to ensure sufficient wetting of the separator. Subsequently, the electrochemical performance of the battery was tested using a Blue Electric CT-3002A high-precision battery tester. Figure 2This is the activation curve of the alloy electrode for the first 7 weeks. The alloy electrode reached its maximum discharge capacity of 304 mAh g in the first week. -1 ; Figure 3 The cycling stability curves of the alloy electrode are shown within 100 cycles. The capacity retention rate of the alloy electrode in the 100th cycle is 79.8%. Figure 4 The high-rate discharge performance curve of the alloy electrode is shown when the discharge current density is 1500 mAg. -1 At that time, the high-rate discharge performance of the alloy electrode was 83.2%.

[0045] Example 4

[0046] A method for preparing a high-power AB3-type AB2-AB5 dual-phase La-Mg-Ni based hydrogen storage alloy, comprising:

[0047] (1) Using elemental metals La, Nd, Sm, Mg, Ni, and Al as raw materials, according to La 0.26 Nd 0.22 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.15 The chemical composition was prepared by mixing La and Nd elements in excess of 3 wt%, Sm element in excess of 5 wt%, and Mg element in excess of 25 wt%. The as-cast alloy was then prepared by medium-frequency induction melting.

[0048] (2) In order to control the amount of Mg volatilization, the heat treatment process of the alloy ingot needs to be carried out in a nickel shell.

[0049] (3) Take 8g of La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.14 The alloy ingot is first prepared by removing the oxide layer from its surface with sandpaper. Then, the alloy block is inserted into the nickel shell through an opening, and a 0.2cm section is folded and hammered at the opening to ensure a tight seal. Finally, a spot welding machine is used to repeatedly weld and seal the folded areas of the nickel shell, resulting in an ingot approximately 4.0cm long, 2.3cm high, 1.8cm wide at the base, and 14cm in volume. 3 A triangular prism shape.

[0050] (4) A step-by-step heat treatment was performed using a vacuum tube furnace. First, the sealed nickel shell containing the alloy was placed flat in the corundum crucible and pushed to the middle of the tube furnace for step-by-step heat treatment. The specific steps were as follows: the two ends of the quartz tube in the sealed tube furnace were purged with argon gas and then vacuumed three times, with the last purging with argon gas to -0.1 MPa; then the temperature was increased at a rate of 5 K / min to 873 K, then increased to 1173 K at a rate of 1 K / min and held for 8 hours, then the temperature was decreased to 973 K at a rate of 1 K / min and held for another 8 hours. Throughout the heat treatment process, the internal pressure of the quartz tube was maintained between -0.02 MPa and 0.02 MPa. After the heat treatment, the temperature was decreased to 773 K at a rate of 5 K / min and then cooled to room temperature with the furnace.

[0051] (5) The heat-treated sample was removed from the nickel shell, the surface oxide layer was removed, and it was mechanically crushed and ground. Alloy powder with a thickness of less than 37 μm was taken and subjected to XRD testing. The obtained data was then refined using Maud software. The XRD pattern of the alloy and the refined pattern are shown below. Figure 1 As shown, the results indicate that the alloy product contains AB5-type LaNi5 phase and AB2-type LaMgNi4 phase, with the AB5 phase accounting for 47.3 wt% and the A2B4 phase accounting for 52.7 wt%. Alloy powder with an average particle size of 37–74 μm was used as the negative electrode active material for the battery. It was uniformly mixed with nickel hydroxide powder at a ratio of 1:5 and cold-pressed to prepare a nickel-metal hydride battery negative electrode sheet. Nickel hydroxide was used as the counter electrode, and 6M KOH aqueous solution was used as the electrolyte to prepare an open-type dual-electrode simulated experimental battery for electrochemical performance testing. Before the test, the battery was immersed in the electrolyte for 24 hours to ensure sufficient wetting of the separator. Subsequently, the electrochemical performance of the battery was tested using a Blue Electric CT-3002A high-precision battery tester. Figure 2 The activation curves for the alloy electrode over the first 7 weeks show that the alloy electrode reached its maximum discharge capacity of 309 mAh g in the first week. -1 ; Figure 3 The curves show the cycle stability of the alloy electrode within 100 cycles, with a capacity retention of 80.3% in the 100th cycle. Figure 4 The high-rate discharge performance curve of the alloy electrode is shown when the discharge current density is 1500 mAg. -1 At that time, the high-rate discharge performance of the alloy electrode was 77.0%.

Claims

1. An AB3 type AB2-AB5 two-phase La-Mg-Ni-based hydrogen storage alloy, characterized in that, It has a dual-phase structure of AB5 type LaNi5 phase and AB2 type LaMgNi4 phase; The content of the LaNi5 phase is 46.3 wt% to 47.3 wt%; The hydrogen storage alloy expression is La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.14 or La 0.26 Nd 0.22 Sm 0.18 Mg 0.34 Ni 2.77 Al 0.13 .

2. The method for preparing the AB3 type AB2-AB5 two-phase La-Mg-Ni-based hydrogen storage alloy according to claim 1, characterized in that, Comprise: (1) Alloying and melting: selecting metal elements, according to La 0.48 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.15 Chemical composition, wherein the La element is 3 wt% excess, the Sm element is 5% excess, the Mg element is 25 wt% excess, and a medium-frequency induction melting method is used to prepare alloy ingots; or, according to La 0.26 Nd 0.22 Sm 0.18 Mg 0.34 Ni 2.75 Al 0.15 The chemical composition is dosed, wherein the La and Nd elements are over 3wt%, the Sm element is over 5%, and the Mg element is over 25wt%, and an alloy ingot is prepared by a medium-frequency induction melting method. (2) Heat treatment: take the smelted alloy ingot, put it into a sealed nickel shell container, and then put the nickel shell containing the alloy ingot into a vacuum tube furnace to perform step-by-step heat treatment under an argon atmosphere.

3. The method of claim 2, wherein, Sealed nickel shell containers meet the alloy ingot quality to nickel shell container inner cavity volume ratio of 6 to 8 g: 10 to 14 cm 3 .

4. The method of claim 2, wherein, The specific process of heat treatment is as follows: fill argon, heat at a rate of 5 K / min to 873 K, then heat at a rate of 1 K / min to 1123-1173 K, keep for 8 h, then reduce the temperature to 973 K at a rate of 1 K / min, continue to keep for 8 h, after heat treatment, reduce to 773 K at a rate of 5 K / min, and cool to room temperature with the furnace, and the pressure in the quartz tube is kept between-0.02 MPa and 0.02 MPa during the whole heat treatment process.

5. The method of claim 2, wherein, Before heat treatment, the quartz tube of the vacuum tube furnace is washed with argon several times to completely remove the internal oxygen, then, under vacuum, the temperature is raised from room temperature to 373 K at a rate of 5 K / min, and kept for 1 h to remove the residual water vapor in the quartz tube.

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