Y-Sm-Mg-Ni series hydrogen storage alloy electrode material and preparation method thereof

Abstract

The invention discloses a Y-Sm-Mg-Ni series hydrogen storage alloy electrode material and a preparation method thereof, the chemical formula of the electrode material is Y1-a-bSmaMgbNixAly, a, b, x and y are atomic ratios, 0.05 < = a < = 0.15, 0 < = b < = 0.2, 2.85 < = x < = 3.05, and 0 < = y < = 0.2, the preparation method comprises the following steps: proportioning metal simple substances, Y-Ni and Mg-Ni intermediate alloys as raw materials, preparing an as-cast alloy by using a conventional induction melting method, and preparing the as-cast alloy into the Y-Sm-Mg-Ni series hydrogen storage alloy electrode material. And the as-cast alloy is wrapped and sealed in a quartz tube with the argon pressure of-0.09 to-0.05 MPa by using a tantalum sheet, and then annealing is performed in a muffle furnace. According to the preparation method, the cycling stability of the Y-Mg-Ni series alloy is remarkably improved through Sm doping, and the preparation cost of the Y-Sm-Mg-Ni series alloy is reduced by adopting Y-Ni and Mg-Ni intermediate alloy as raw materials in the preparation method.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen storage alloys, and in particular to a Y-Sm-Mg-Ni series hydrogen storage alloy electrode material and a preparation method thereof. Background Art

[0002] Nickel-metal hydride (Ni-MH) batteries are rechargeable batteries favored for their safety and environmental friendliness. While lithium batteries are now widely used in various applications, Ni-MH batteries still offer significant advantages in certain areas. Compared to lithium batteries, Ni-MH batteries exhibit greater safety and a longer service life. In particular, Ni-MH batteries exhibit greater stability and are less likely to cause safety issues in situations involving overcharge or over-discharge, making them particularly attractive for applications with high safety standards. Furthermore, Ni-MH batteries offer a longer cycle life and can withstand a greater number of charge and discharge cycles, making them more economical in long-term use. While lithium batteries hold an advantage in energy density, these characteristics make Ni-MH batteries a compelling choice for specific applications.

[0003] The performance of nickel-hydrogen batteries mainly depends on the hydrogen storage alloy of the negative electrode material. The traditional negative electrode material is an AB5 type hydrogen storage alloy, whose commercial maximum discharge capacity is about 340 mAh / g, which is close to the theoretical maximum and cannot meet the current market demand. Therefore, there is an urgent need to develop negative electrode materials with higher capacity. In recent years, superlattice La-Mg / Y-Ni alloys have become a research hotspot and are regarded as potential candidate materials. However, compared with La-Mg / Y-Ni alloys, the newly discovered Y-Mg-Ni alloys are mainly composed of light elements Y and magnesium Mg, which have higher theoretical capacity. However, yttrium and magnesium are very easy to react with the alkaline electrolyte in nickel-hydrogen batteries, thereby significantly reducing the cycle life (reference: Int J Hydrogen Energ 2018, 43(37):17800 and Int J Hydrogen Energ 2019, 44(39): 22064). If the cycle life of Y-Mg-Ni alloys is not improved, they will be difficult to use in nickel-hydrogen batteries. In addition, the price of Y metal alone is relatively high, about four times that of Y-Ni alloy; at the same time, Mg is easily volatilized during the smelting preparation process. In CN115074578A, a Y-Mg-Ni based alloy was prepared by mixing alloy powder with Mg powder and then sintering. The phase structure of this alloy is (Y, Mg, D) (Ni, E)2 phase of F-43m and (Y, Mg, D) (Ni, E)3 phase of space group R-3m, and the structure is relatively stable. However, the cycle capacity decays rapidly, making it difficult to apply. Summary of the Invention

[0004] In response to the above-mentioned shortcomings, the present invention proposes a Y-Sm-Mg-Ni series hydrogen storage alloy electrode material and a preparation method thereof. The cycle stability of the Y-Mg-Ni series alloy is significantly improved by Sm doping. The preparation method reduces the preparation cost of the Y-Sm-Mg-Ni series alloy by using Y-Ni and Mg-Ni intermediate alloys as raw materials.

[0005] To achieve the above object, the present invention provides the following technical solutions: a Y-Sm-Mg-Ni series hydrogen storage alloy electrode material, the chemical formula of the electrode material is Y 1-a-b Sm a Mg b Ni x Al y , a, b, x and y are all atomic ratios, where 0.05≤a≤0.15, 0≤b≤0.2, 2.85≤x≤3.05, 0≤y≤0.2.

[0006] As an improvement, 0.08≤a≤0.12, 0≤y≤0.10.

[0007] As an improvement, the electrode materials include AB3 type phase, A2B7 type phase, A5B 19 type phase, AB3 type phase is the main phase.

[0008] The method for preparing any one of the above-mentioned Y-Sm-Mg-Ni series hydrogen storage alloy electrode materials comprises the following steps: S1: Using metal elements, Y-Ni and Mg-Ni master alloys as raw materials, the cast alloy is prepared by induction melting method; S2: Wrapping the as-cast alloy with a tantalum sheet and sealing it in a quartz tube with an argon pressure of -0.09 to -0.05 MPa, and then uniformly heating it from room temperature to a first temperature in a muffle furnace; S3: then uniformly heating to the second temperature, keeping it warm for 0.5-1.5 hours, finally uniformly heating to the third temperature, keeping it warm for 4-8 hours, then cooling naturally or in a water bath to room temperature and taking it out.

[0009] As an improvement, the first temperature in step S2 is 550° C.-650° C., and the heating rate is 2-8° C. / min.

[0010] As an improvement, the second temperature in step S3 is 650° C.-750° C., and the heating rate is 0.5-1.5° C. / min.

[0011] As an improvement, the third temperature in step S3 is 925° C. to 975° C., and the heating rate is 0.5-1.5° C. / min.

[0012] As an improvement, the maximum discharge capacity of the nickel-hydrogen battery negative electrode material prepared using the electrode material is 371mAh / g-382mAh / g at room temperature, and the capacity retention rate after 100 charge and discharge cycles is 89.5%-91.5%.

[0013] Compared with the prior art, the advantages of the present invention are: (1) By doping with Sm, the alloy successfully improved the cycle stability of the Y-Mg-Ni alloy. This improvement enables the electrode material to maintain higher capacity stability during the charge and discharge cycle, thereby extending the battery life. Specifically, the maximum discharge capacity of the nickel-hydrogen battery negative electrode material prepared using this electrode material reaches 371mAh / g to 382mAh / g at room temperature, and after 100 charge and discharge cycles, its capacity retention rate can still be maintained at a high level of 89.5% to 91.5%; (2) The alloy electrode material has the characteristics of high capacity, which is due to its fine phase structure design and optimized chemical composition ratio. The material contains AB3 type phase, A2B7 type phase and A5B 19 type phase, of which the AB3 type phase is the main phase. This combination of phase structures enables the alloy to store and release hydrogen more effectively, thereby improving the hydrogen storage capacity and electrochemical performance of the electrode; (3) The use of Y-Ni and Mg-Ni intermediate alloys as raw materials significantly reduces the preparation cost of Y-Sm-Mg-Ni alloys. Traditional alloy preparation methods often require high-purity metal elements as raw materials, which are expensive. By using these intermediate alloys, not only the raw material cost is reduced, but also the preparation process is simplified and the production efficiency is improved. (4) The preparation method of the alloy electrode material is simple and easy, and is easy to industrialize. The cast alloy is prepared by induction melting method, and then after a specific heat treatment process, the electrode material with excellent performance can be obtained. This preparation process is not only easy to control, but also has good repeatability, which provides a strong guarantee for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Figure 1 This is a schematic diagram of the alloy phase structure of Example 1; Figure 2 This is a schematic diagram of the alloy phase structure of Example 2; Figure 3 This is a schematic diagram of the alloy phase structure of Example 3; Figure 4 This is a schematic diagram of the alloy phase structure of Example 4; Figure 5 Schematic diagram of the alloy phase structure of comparative example 1. DETAILED DESCRIPTION

[0015] Example 1 As shown in Table 1, S1: metal elements Sm, Ni, Al, Y-Ni and Mg-Ni master alloy are used as raw materials for batching, wherein Sm is 1.75g, Ni is 4.27g, Al is 0.32g, Y-Ni is 22.24g, and Mg-Ni is 1.42g, and the cast alloy is prepared by induction melting method; S2: The cast alloy was wrapped with tantalum sheets and sealed in a quartz tube with an argon pressure of -0.07 MPa, and then heated from room temperature to 600°C in a muffle furnace at a heating rate of 5°C / min; S3: Then, the temperature was raised to 700°C at a heating rate of 1°C / min and kept at this temperature for 1 hour. Finally, the temperature was raised to 950°C at a heating rate of 1°C / min and kept at this temperature for 6 hours. The temperature was then naturally cooled or cooled in a water bath to room temperature to obtain the desired alloy, wherein the total mass of the alloy was 30 g.

[0016] The chemical composition of the alloy electrode material is: Y 0.75 Sm 0.1 Mg 0.1 Ni 2.9 Al 0.1 The alloy electrode material is crushed by mechanical crushing, then passed through a 400-mesh sieve, and its structure is tested by an X-ray diffractometer and analyzed by the Rietveld method, as shown in FIG. Figure 1 As shown, the phase structure of the alloy prepared in Example 1 is AB3 type phase and A2B7 type phase, and the phase contents are 90.1% and 9.9% respectively.

[0017] The crushed alloy was sieved through a 160-200 mesh sieve, and 0.2 g of alloy powder and 0.8 g of nickel powder were weighed and evenly mixed using a grinder. The mixture was then placed into a mold with a diameter of 16 mm and cold-pressed into electrode sheets at a pressure of 10 MPa. The positive electrode was sintered nickel hydroxide (Ni(OH)2 / NiOOH), and the electrolyte was a 6 mol / L KOH solution to form a half-cell.

[0018] The test was conducted on a CT3004A battery tester at room temperature of 25°C. The maximum discharge capacity test steps of the alloy half-cell were as follows: first, the prepared half-cell was allowed to stand for 24 hours, then charged at a current density of 60 mA / g for 7.5 hours, allowed to stand for 10 minutes, and then discharged at a current density of 60 mA / g to 0.6 V, allowed to stand for 10 minutes. This charge and discharge cycle was repeated until the maximum discharge capacity was reached. The maximum discharge capacity of Example 1 was 378 mAh / g.

[0019] The alloy was charged at a current density of 300 mA / g for 1.5 h, allowed to stand for 10 minutes, and then discharged at a current density of 60 mA / g to 1.0 V and allowed to stand for 10 minutes. The discharge capacity of each charge and discharge cycle was recorded. The ratio of the discharge capacity at 100 cycles to the maximum discharge capacity was the capacity retention rate of the alloy. The capacity retention rate of Example 1 after 100 cycles was 84.6%.

[0020] Example 2 As shown in Table 1, S1: metal elements Sm, Ni, Al, Y-Ni and Mg-Ni master alloy are used as raw materials for batching, wherein Sm is 2.56g, Ni is 4.88g, Al is 0.31g, Y-Ni is 20.19g, and Mg-Ni is 2.07g, and the cast alloy is prepared by induction melting method; The remaining steps are consistent with those in Example 1.

[0021] The chemical composition of the alloy electrode material is: Y 0.7 Sm 0.15 Mg 0.15 Ni 2.95 Al 0.11 ,like Figure 1 As shown, the phase structure of the alloy prepared in Example 2 is AB3 type phase, A2B7 type phase and A5B19 type phase, and the phase contents are 81.2%, 10.3% and 8.5% respectively.

[0022] The maximum discharge capacity of Example 2 is 371 mAh / g.

[0023] The capacity retention rate of Example 2 after 100 cycles is 91.5%.

[0024] Example 3 As shown in Table 1, S1: metal elements Sm, Ni, Al, Y-Ni and Mg-Ni master alloy are used as raw materials for batching, wherein Sm is 2.08g, Ni is 3.37g, Al is 0.16g, Y-Ni is 23.13g, and Mg-Ni is 1.26g, and the cast alloy is prepared by induction melting method; The remaining steps are consistent with those in Example 1.

[0025] The chemical composition of the alloy electrode material is: Y 0.79 Sm 0.12 Mg 0.09 Ni 2.87 Al 0.05 ,like Figure 1 As shown, the phase structure of the alloy prepared in Example 3 is AB3 type phase and A2B7 type phase, and the phase contents are 66.5% and 33.5% respectively.

[0026] The maximum discharge capacity of Example 3 is 375 mAh / g.

[0027] The capacity retention rate of Example 3 after 100 cycles is 90.8%.

[0028] Example 4 As shown in Table 1, S1: metal elements Sm, Ni, Al, Y-Ni and Mg-Ni master alloy are used as raw materials for batching, wherein Sm is 1.40g, Ni is 2.81g, Al is 0.63g, Y-Ni is 22.33g, and Mg-Ni is 1.84g, and the cast alloy is prepared by induction melting method; The remaining steps are consistent with those in Example 1.

[0029] The chemical composition of the alloy electrode material is: Y 0.79 Sm 0.08 Mg 0.13 Ni 2.85 Al 0.2 ,like Figure 1 As shown, the phase structure of the alloy prepared in Example 4 is AB3 type phase and A2B7 type phase, and the phase contents are 71.3% and 28.7% respectively.

[0030] The maximum discharge capacity of Example 4 is 382 mAh / g.

[0031] The capacity retention rate of Example 4 after 100 cycles is 89.5%.

[0032] Comparative Example 1 As shown in Table 1, S1: metal element Ni, Y-Ni and Mg-Ni master alloy are used as raw materials for batching, wherein Ni is 1.84g, Y-Ni is 25.97g, and Mg-Ni is 1.84g, and the cast alloy is prepared by induction melting method; The remaining steps are consistent with those in Example 1.

[0033] The chemical composition of the alloy electrode material is: Y 0.85 Mg 0.15 Ni 2.9 ,like Figure 1 As shown, the phase structure of the alloy prepared in Comparative Example 1 is AB3 type phase, and the phase content is 100%.

[0034] The maximum discharge capacity of Comparative Example 1 is 375 mAh / g.

[0035] The capacity retention rate of Comparative Example 1 after 100 cycles is 84.6%.

[0036] Table 1 lists the electrochemical properties of the hydrogen storage alloys described in Examples 1 to 4 and Comparative Example 1. As can be seen from Table 1, compared to Comparative Example 1, the addition of Sm and Al in Examples 1 to 4 significantly improves the cycle capacity retention of the alloy electrode material while maintaining the maximum discharge capacity of the electrode material.

[0037] Table 1 Electrochemical performance of Example 1 to Comparative Example 1 The alloy phase structure of the comparative example 1 is a single AB3 type phase. As we all know, the structural stability of the AB3 type phase is not as good as that of the A2B7 type phase and the A5B 19 In Examples 1 to 4, after adding Sm and Al, A2B7 and A5B 19 phase, which improves the structural stability of the alloy electrode during the cycle. In addition, according to literature research, Sm and Al can improve the corrosion resistance of hydrogen storage electrode materials in alkaline electrolytes and slow down the capacity decay of alloy electrodes (Int J Hydrogen Energ, 2021, 46(10): 7432, Int J Hydrogen Energ, 2025, 109: 264.). Therefore, compared with Comparative Example 1, Examples 1 to 4 improve the cycle capacity retention rate of the alloy electrode material in terms of structural stability and oxidation corrosion resistance, and ensure that the maximum discharge capacity remains basically unchanged.

[0038] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A Y-Sm-Mg-Ni series hydrogen storage alloy electrode material, characterized by: The chemical formula of the electrode material is Y 1-a- b Sm a Mg b Ni x Al y , a, b, x and y are all atomic ratios, where 0.05≤a≤0.15, 0≤b≤0.2, 2.85≤x≤3.05, 0≤y≤0.

2.

2. The Y-Sm-Mg-Ni series hydrogen storage alloy electrode material according to claim 1, characterized in that: The aforementioned 0.08≤a≤0.12, 0≤y≤0.

10.

3. The Y-Sm-Mg-Ni series hydrogen storage alloy electrode material according to claim 1, characterized in that: The electrode materials include AB3 type phase, A2B7 type phase, A5B 19 type phase, the AB3 type phase is the main phase.

4. A method for preparing a Y-Sm-Mg-Ni series hydrogen storage alloy electrode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: Using metal elements, Y-Ni and Mg-Ni master alloys as raw materials, the cast alloy is prepared by induction melting method; S2: Wrapping the as-cast alloy with a tantalum sheet and sealing it in a quartz tube with an argon pressure of -0.09 to -0.05 MPa, and then uniformly heating it from room temperature to a first temperature in a muffle furnace; S3: then uniformly heating to the second temperature, keeping it warm for 0.5-1.5 hours, finally uniformly heating to the third temperature, keeping it warm for 4-8 hours, then cooling naturally or in a water bath to room temperature and taking it out.

5. The method for preparing a Y-Sm-Mg-Ni series hydrogen storage alloy electrode material according to claim 4, characterized in that: The first temperature in step S2 is 550° C.-650° C., and the heating rate is 2-8° C. / min.

6. The method for preparing a Y-Sm-Mg-Ni series hydrogen storage alloy electrode material according to claim 4, characterized in that: The second temperature in step S3 is 650° C.-750° C., and the heating rate is 0.5-1.5° C. / min.

7. The method for preparing a Y-Sm-Mg-Ni series hydrogen storage alloy electrode material according to claim 4, characterized in that: The third temperature in step S3 is 925° C. to 975° C., and the heating rate is 0.5-1.5° C. / min.

8. The method for preparing a Y-Sm-Mg-Ni series hydrogen storage alloy electrode material according to claim 4, characterized in that: The maximum discharge capacity of the nickel-hydrogen battery negative electrode material prepared using the electrode material is 371mAh / g-382mAh / g at room temperature, and the capacity retention rate after 100 charge and discharge cycles is 89.5%-91.5%.

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