A RE-Mg-Ni-based AB-type electrode alloy for Ni-MH secondary batteries and a preparation method thereof

Abstract

The present invention relates to the technical field of hydrogen storage alloy materials, and particularly relates to a RE-Mg-Ni-based AB-type electrode alloy for Ni-MH secondary batteries and a preparation method thereof. The composition of the hydrogen storage electrode alloy is: Mg 10‑ x Ce x Ni 9‑y‑z‑m Co y Al z Mn m +n wt.% Ni, where x, y, z, m are atomic ratios, and 0

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen storage alloy materials, and particularly relates to a RE-Mg-Ni-based AB-type hydrogen storage electrode alloy for high-capacity and long-life Ni-MH secondary batteries and a preparation method thereof. Background Art

[0002] The main advantages of nickel-metal hydride batteries are pollution-free, safe, and efficient, making them suitable for use in hybrid electric vehicles. However, in order to improve the performance of nickel-metal hydride battery systems and reduce their costs to increase consumer acceptance of electric vehicles or hybrid electric vehicles, further research is still needed.

[0003] Many metal hydrides have been identified for practical hydrogen storage applications, especially commercially produced rare-earth-based AB5 and AB2-type alloys. However, the specific capacity of AB5 alloys is not ideal, and the activation of AB2 alloys is relatively difficult, which limits their further development. Mg-based alloys have good electrochemical hydrogen capacity and are ideal candidates for nickel-metal hydride battery electrodes. The most attractive advantage of Mg-based alloys is their low cost and high discharge capacity, but the poor electrochemical cycle stability and low discharge capacity of Mg-based alloys limit their practical applications at room temperature. Summary of the Invention

[0004] The main object of the present invention is to provide a RE-Mg-Ni-based AB-type electrode alloy for Ni-MH secondary batteries and a preparation method thereof. Through the present invention, the electrochemical cycle stability of the hydrogen storage electrode alloy is greatly improved while maintaining a high capacity.

[0005] The inventors, through research on Mg-based alloys, found that the formation of a relatively thick Mg(OH)2 layer on the electrode surface is the main cause of capacity decay. The newly formed Mg(OH)2 layer inhibits hydrogen diffusion and charge transfer, reducing the content of active substances. In addition, harmful pulverization can lead to further corrosion of active metals and promote the generation of additional Mg(OH)2 during the electrode reaction process. Therefore, partial substitution of Mg and / or Ni is considered an effective method to improve electrochemical performance, where substitution can enhance the antioxidant and / or anti-crushing ability of the alloy electrode by reducing the expansion coefficient. Especially adding rare earths and transition metals to magnesium-nickel-based alloys can improve the corrosion resistance of the alloys and increase the cycle life. Some scholars have studied Mg 0.9− x Ti 0.1 Pd xNi (x = 0.04-0.1) alloys, it was found that replacing Mg with Pd greatly improved the electrochemical cycle stability. This improvement is due to the formation of a passivation film on the electrode surface. Some scholars have also reported that adding Pd can improve the cycle stability of Mg2Ni-based alloys and improve the electrochemical performance through surface modification, especially mechanical coating.

[0006] The present invention achieves its purpose through the following technical solutions.

[0007] One aspect of the present invention provides a hydrogen storage electrode alloy for Ni-MH secondary batteries, which is characterized in that the alloy contains rare earth element Ce and metal elements Ni, Co, Al and Mn, and a certain amount of nano Ni powder is added, and the surface coating of the alloy particles is achieved by mechanical ball milling, and the composition is: Mg 10-x Ce x Ni 9-y-z-m Co y Al z Mn m + n wt.%Ni, where x, y, z, m are atomic ratios, and 0 <x≤2, 0<y≤1, 0<z≤1, 0<m≤1, n为纳米Ni所占合金的百分比, 40≤n≤60。优选的原子比x: y: z: m = 1: 0.5: 0.5: 0.5, n = 50。

[0008] Another aspect of the present invention provides a method for preparing a hydrogen storage electrode alloy for a Ni-MH battery, the preparation steps comprising:

[0009] 1. Ingredients: According to the chemical formula Mg 10-x Ce x Ni 9-y-z-m Co y Al z Mn m To prepare the ingredients, <x≤2, 0<y≤1,0<z≤1, 0<m≤1, 其中,所述化学式组成中的Mg在配比时增加8%、稀土Ce及金属Mn在配比时增加5%比例的烧损量,原材料的金属纯度≥99.5%。

[0010] 2. Alloy melting and rapid quenching: The weighed raw materials are heated by conventional methods, such as arc melting, induction heating melting or other heating methods. The heating conditions are as follows: evacuate to 1×10-2-5×10-5 Pa, introduce 0.01-0.1 MPa of high-purity helium or a helium + argon mixed gas with a volume ratio of about 1:1 as a protective gas, heat to 1500-1600℃, and obtain molten Mg 10-x Ce x Ni 9-y-z-m Coy Al z Mn m Liquid master alloy. After the molten alloy is kept in a protective gas atmosphere for about 5 minutes, the liquid master alloy is directly injected into a tundish with an NB nozzle embedded at the bottom. The liquid alloy continuously drops from the slit of the NB nozzle at the bottom of the tundish (the slit width is 0.3 mm) onto the surface of a water-cooled copper roller rotating at a linear speed of 5 - 30 m / s, obtaining a rapidly quenched alloy thin sheet with a thickness between 50 - 300 μm. It is necessary to determine an appropriate rapid quenching cooling rate to ensure that the rapidly quenched alloy thin strip has an almost completely nanocrystalline structure with a grain size between 10 - 100 nm.

[0011] 3. Mechanical ball milling with Ni coating on the surface: The rapidly quenched Mg 10-x Ce x Ni 9-y-z-m Co y Al z Mn m The alloy thin strip is mechanically crushed and screened through a 200 - mesh sieve. The sieved alloy powder, a certain amount of nano - Ni powder, and stainless - steel grinding balls are loaded into a stainless - steel ball - milling tank. After evacuating, high - purity argon is filled. Ball milling is carried out in an all - around planetary high - energy ball mill for 5 - 20 hours, preferably 8 hours, with a ball - to - material ratio of 20:1 and a rotation speed of 350 revolutions per minute. During the ball - milling process, the ball mill stops for 0.5 hour every 1 hour of continuous operation to prevent the temperature of the ball - milling tank and abrasive from being too high. Determining the ball - milling time is crucial. If the ball - milling time is too long, a large amount of amorphous phase will appear, deteriorating the electrochemical performance of the alloy. The optimal ball - milling time is to ensure that there is no excessive amorphous phase in the ball - milled alloy and to ensure good bonding between the nano - Ni powder and the alloy powder, so that the Ni powder is evenly distributed on the surface of the alloy particles, thereby improving the electro - catalytic activity and cycle stability of the alloy.

[0012] 4. Structure analysis and performance testing: The phase structure of the as - cast and ball - milled powders is tested by XRD. The morphology and microstructure of the as - cast and ball - milled alloys are observed by high - resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM), and the crystallinity of the alloy is determined by selected - area electron diffraction (SAED). After mixing the obtained alloy powder and nickel carbonyl powder (particle diameter ≤ 2.5 μm) evenly according to a mass ratio of 1:4, a cylindrical electrode sheet with a diameter of 15 mm is cold - pressed under a pressure of 35 MPa, and then its electrochemical performance is tested by the standard three - electrode test method.

[0013] From the ball - milled MmMg 12During the study of the electrochemical properties of the alloy-Ni composite materials, it was found that when the Ni content increased from 150 wt.% to 200 wt.%, the initial discharge increased from 964 mAh / g to 1164 mAh / g. Some scholars found that both the cycle life and the maximum discharge capacity of the Mg-50 at.% Ni composite materials were significantly improved. Some scholars studied the electrochemical properties of Mg2NiH4 prepared by mechanical coating of nano-Ni, and the maximum discharge capacity reached 896 mAh / g, with a significant improvement in the anti-corrosion ability.

[0014] Applying the technical solution of the present invention has the following technical effects:

[0015] In the present invention, part of Mg is replaced by Ce, and part of Ni is replaced by Al, Co and Mn to improve the electrochemical properties of the alloy. Previous studies have found that adding Al and Co can improve the corrosion resistance of AB3-type alloys in KOH electrolytes, and adding Ce can significantly improve the electrochemical properties of REMg12-type alloys. On this basis, the surface of the alloy is modified by mechanical coating of nickel powder. The Ni coating effectively increases the corrosion resistance of the Mg-based alloy, improves the charge transfer rate on the electrode surface and the diffusion of hydrogen in the electrode. On the basis of scientific design of the composition, by melt spinning combined with mechanical ball milling of Ni-coated coating, not only the high capacity of the alloy is maintained, but also the electrochemical cycle stability is greatly improved. Brief Description of the Drawings

[0016] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0017] Figure 1 SEM morphology of the as-cast alloys of Examples 1-6.

[0018] Figure 2 Rapidly quenched (10 m / s) alloy ribbon of Example 1.

[0019] Figure 3 SEM morphology of the ball-milled alloy powders of Examples 1-6.

[0020] Figure 4 XRD diffraction patterns of the ball-milled powders of Examples 1-6.

[0021] Figure 5 HRTEM morphology of the ball-milled powders of Examples 1-6. Detailed Description of the Invention

[0022] The embodiments of the present application will be described in detail below in conjunction with the accompanying drawings and examples, so as to fully understand how the present application uses technical means to solve technical problems and achieve the realization process of technical effects and implement accordingly.

[0023] Through research, the present invention finds that the pulverization of alloy particles during hydrogen absorption and desorption is the main reason for the capacity decline. By alloying to increase the lattice parameter of the alloy and reduce the lattice expansion rate during hydrogen absorption and desorption, the anti-pulverization ability of the alloy can be effectively improved, thereby improving the electrochemical cycle stability of the alloy. In terms of composition design, adding micro-alloying elements Co, Mn, and Al can increase the unit cell volume and refine the alloy grains. At the same time, adding multiple rare earth elements Ce to the alloy can significantly improve the corrosion resistance of alloy elements in the electrolyte when matched with Al, further improving the electrochemical cycle stability of the alloy.

[0024] The rapidly quenched alloy prepared by the vacuum rapid quenching technology has a uniform nanocrystalline-amorphous structure and is arranged in columnar crystals along the direction perpendicular to the roll surface. This structure is particularly beneficial for improving the anti-pulverization ability of the alloy. Different from ball milling, the ultrafine structure and crystal defects obtained by rapid quenching have high stability, and the grains are not easy to aggregate and grow after multiple charge-discharge cycles. In terms of electrochemical performance, it not only maintains the high capacity of the alloy but also has good cycle stability. In addition, compared with the casting process, the rapid quenching treatment completely eliminates the composition segregation caused by the crystallization process, which is extremely beneficial to improving the electrochemical performance of the alloy.

[0025] After adding nano-Ni powder and undergoing mechanical ball milling, while maintaining the microstructure of the rapidly quenched alloy, the surface state of the alloy is improved, and the advantages of the two preparation processes are exerted. The surface coating of Ni is the key for the alloy of this system to electrochemically store hydrogen. As is well known, RE-Mg-Ni-based alloys can basically not electrochemically store hydrogen at room temperature. Even through alloying treatment, their discharge capacity is very low and cannot meet the capacity requirements of the negative electrode of Ni-MH batteries. Through the mechanical coating of nano-Ni powder, the electrocatalytic activity of the alloy surface is fundamentally changed, so that the alloy has good electrochemical hydrogen storage performance at room temperature. At the same time, through the mechanical coating treatment, a uniformly distributed Ni coating is formed on the surface of the alloy particles, which can significantly improve the corrosion resistance of the alloy in alkaline electrolytes, so that the electrochemical cycle stability performance of the alloy meets the requirements of the negative electrode of Ni-MH batteries. It is precisely because of the combination of rapid quenching and mechanical ball milling that the electrochemical performance of the alloy is greatly improved.

[0026] The present invention further illustrates the composition and preparation method of the RE-Mg-Ni-based AB-type electrode alloy involved in the present invention through the following examples.

[0027] The RE-Mg-Ni-based AB-type electrode alloy for Ni-MH batteries of the present invention has a chemical formula of: Mg 10- x Ce x Ni 9-y-z-m Co y Al z Mn m + n wt.%Ni, where x, y, z, m are atomic ratios, and 0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 1, 0 < m ≤ 1, n is the percentage of nano-Ni in the alloy, and 40 ≤ n ≤ 60. The preferred atomic ratio x:y:z:m = 1:0.5:0.5:0.5, and n = 50.

[0028] The preparation method of the RE-Mg-Ni-based AB-type electrode alloy for Ni-MH batteries of the present invention includes the following steps:

[0029] A. Charge materials according to the chemical formula composition Mg 10-x Ce x Ni 9-y-z-m Co y Al z Mn m Since metallic Mg, rare earth Ce, and metallic Mn are prone to volatilization, when formulating the ratio, Mg is added in an extra 8% amount, and rare earth Ce and metallic Mn are each added in an extra 5% amount to compensate for the loss by burning.

[0030] B. Place the prepared raw materials in a magnesia crucible in sequence. Blocky rare earth Ce is placed at the bottom of the crucible, electrolytic Ni, Co, and Mn are placed above rare earth Ce, electrolytic Al is placed above metallic Ni, Co, and Mn, and metallic Mg is placed on the top. After the materials are placed in sequence, cover the furnace lid, evacuate to 1×10 -2 -5×10 -5 Pa, and fill with high-purity helium gas at a pressure of 0.01 - 0.1 MPa as a protective gas. The melting temperature is 1500 - 1600 °C to obtain molten Mg 10-x Ce x Ni 9-y-z-m Co y Al z Mn m liquid master alloy.

[0031] C. Under the protection of an inert gas atmosphere, after the alloy is melted and held for about 5 minutes, the liquid master alloy is directly poured into a tundish with an NB nozzle embedded at the bottom. The liquid alloy continuously sprays through the slit of the NB nozzle onto the smooth surface of a water-cooled copper roller rotating at 5 - 30 m / s, preferably 10 m / s, to obtain a rapidly quenched alloy thin sheet with a thickness between 50 - 300 μm. This rapidly quenched alloy has a columnar crystal structure, which is a uniform and consistent nanocrystalline structure. The requirement for rapid quenching is to ensure that the rapidly quenched alloy thin strip has as many nanocrystalline structures as possible. If the rapid quenching cooling rate is too fast, a considerable proportion of amorphous phase will appear in the structure, which will cause a sharp drop in the electrochemical capacity of the alloy. If the cooling rate is too slow, a relatively large number of microcrystalline structures will appear, weakening the electrochemical kinetic performance of the alloy.

[0032] D. After mechanically crushing the rapidly quenched Mg 10-x Ce x Ni 9-y-z-m Co y Al z Mn m alloy thin strip and passing it through a 200 - mesh sieve, it is mixed with a certain amount of nano - Ni powder and stainless - steel grinding balls and loaded into a stainless - steel ball - milling tank. After evacuating, high - purity argon is filled, and ball - milling is carried out in an all - around planetary high - energy ball - mill for 5 - 20 hours, preferably 8 hours; the ball - to - material ratio is 20:1, and the rotation speed is 350 revolutions per minute. During the ball - milling process, the ball - mill stops for 0.5 hours every 1 hour of continuous operation to prevent the temperature of the ball - milling tank and the abrasive from being too high. Through the above preparation process, the RE - Mg - Ni - based AB - type electrode alloy for Ni - MH batteries described in this patent is obtained. It should be noted that the ball - milling process must be appropriate. An overly long ball - milling time will result in more amorphous phases in the microstructure, and at the same time, due to cold welding between particles, agglomeration will occur, which will all reduce the electrochemical performance of the alloy. At the same time, an overly long ball - milling time will increase energy consumption and reduce the efficiency of material preparation, not meeting the requirements for large - scale alloy preparation.

[0033] E. The structure of the ball - milled powder is tested by XRD, and the morphology and microstructure of the alloy before and after ball - milling are observed by high - resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM), and the crystal state of the alloy is determined by selected - area electron diffraction (SAED). The electrochemical discharge capacity and cycle stability of the alloy are tested by a simulated battery tester.

[0034] The chemical composition and proportion of the specific embodiments of the present invention are selected as follows:

[0035] Example 1: Mg9Ce1Ni 7.5 Co 0.5 Al 0.5 Mn 0.5 + 50 wt.% Ni

[0036] Example 2: Mg8Ce2Ni 7.5 Co 0.5 Al 0.5 Mn 0.5 + 50 wt.% Ni

[0037] Example 3: Mg9Ce1Ni7Co1Al 0.5 Mn 0.5 + 50 wt.% Ni

[0038] Example 4: Mg9Ce1Ni7Co 0.5 Al1Mn 0.5 + 50 wt.% Ni

[0039] Example 5: Mg9Ce1Ni7Co 0.5 Al 0.5 Mn1 + 50 wt.% Ni

[0040] Example 6: Mg 8.5 Ce 1.5 Ni 7.5 Co 0.5 Al 0.5 Mn 0.5 + 50 wt.% Ni

[0041] Comparative Example 1: Mg 10 Ni 10 (Rapid quenching)

[0042] Select massive metals Mg, rare-earth metal Ce, electrolytic Ni, Co, Mn, and Al according to the chemical formula compositions of the respective examples. The metal purity requirement is ≥99.5%. After grinding the selected massive metals to remove the surface oxide layer, weigh them according to the stoichiometric ratio. Among them, the metal Mg is increased by 8% during the proportioning, and the rare-earth Ce and the metal Mn are increased by 5% to make up for the loss during melting; during the preparation process, the technical parameters at each stage are as follows: the vacuum is from 1×10-2 to 5×10-4 Pa during induction heating, and high-purity helium gas with a filling pressure of 0.01 - 0.1 MPa or a helium + argon mixed gas with a volume ratio of 1:1 is filled; the melting temperature is 1500 - 1600 °C; the surface linear velocity of the rapid quenching water-cooled copper roller is 5 - 30 m / s. After mechanically crushing the rapidly quenched thin flakes and passing them through a 200-mesh sieve, mix them with nano-Ni powder and stainless steel grinding balls and load them into a stainless steel ball milling tank, and ball mill for 5 - 20 hours. The ball mill stops for 0.5 hours every 1 hour of continuous operation. All process parameters can be appropriately selected within the above ranges to prepare the hydrogen storage alloy powder described in the patent. Therefore, although only a typical example is given in the present invention, this example is applicable to preparation methods with different parameters.

[0043] Process technical parameters of Example 1: According to the chemical formula Mg9Ce1Ni 7.5 Co 0.5 Al 0.5 Mn 0.5 , select massive Mg, rare earth Ce, electrolytic Ni, Co, Mn and Al. The purity of these metals is 99.5%. Weigh them according to the stoichiometric ratio. Each furnace is charged with 5 kg of materials. Among them, massive metal Mg is 1358.5 g, rare earth Ce is 846.0 g, electrolytic Ni is 2531.4 g, electrolytic Mn is 165.9 g, electrolytic Co is 169.4 g, and electrolytic Al is 77.6 g. Place the weighed massive metals in a magnesia crucible of an intermediate frequency induction furnace according to the designed process. Place massive rare earth Ce at the bottom of the crucible, electrolytic Ni, Co and Mn on top of rare earth Ce, electrolytic Al on top of metals Ni, Co and Mn, and metal Mg on the top. Then cover the furnace lid, evacuate to a vacuum of about 30 minutes until the vacuum degree is above 5×10-2 Pa, and then fill with high-purity helium protective gas until the air pressure reaches 0.04 MPa. Adjust the power to 5 kW and control the temperature at 650 °C to melt metal Mg. Then adjust the power to 25 kW and control the temperature at 1600 °C to melt the remaining metals. After the molten alloy is kept for 5 minutes in the protective gas atmosphere, directly inject the liquid master alloy into the tundish with an NB nozzle embedded at the bottom. The liquid alloy continuously drops from the gap of the NB nozzle at the bottom of the tundish (the nozzle gap width is 0.3 mm) onto the surface of a water-cooled copper roller rotating at a linear speed of 10 m / s, obtaining a rapidly quenched alloy thin sheet with a thickness of about 182 μm and an average grain size of about 51 nm. Crush the rapidly quenched Mg9Ce1Ni 7.5 Co 0.5 Al 0.5 Mn 0.5 alloy thin sheet mechanically and sieve it through a 200-mesh sieve. Weigh 20 g of the sieved alloy powder, 10 g of nano-Ni powder and 400 g of stainless steel grinding balls and mix them together and load them into a 250-ml stainless steel ball milling jar. Evacuate and fill with high-purity argon and then seal. Ball mill in an all-round planetary high-energy ball mill for 8 hours. The ball mill stops for 0.5 hour every 1 hour of continuous operation.

[0044] Figure 1 SEM morphologies of the as-cast alloys of Examples 1-6. The results show that after adding rare earth Ce and alloying with various metals, a variety of intermetallic compounds are formed. Among them, Mg and Ni form the main phase Mg2Ni, the MgNi2 phase, Ce and Ni form the Ce2Ni7 phase, and Al and Ni form various intermetallic compounds such as the Al3Ni5 phase.

[0045] Figure 2It is a physical photo of the rapidly quenched alloy ribbon, and the quenching speed is 10 m / s. The thickness of the tested ribbon is about 182 μm. It is found by HRTEM observation that the rapidly quenched alloy ribbon is almost completely nanocrystalline structure, and the average grain size is about 51 nm.

[0046] Figure 3 It is the SEM morphology of the ball-milled powders of Examples 1-6. It is observed that the dispersion of alloy particles after ball milling is very good, and no obvious agglomeration phenomenon is formed.

[0047] Figure 4 It is the XRD pattern of the ball-milled alloys of Examples 1-6. It is found that the ball-milled materials have the structural characteristics of nanocrystals and amorphous.

[0048] Figure 5 It is the HRTEM morphology of the ball-milled alloys of Examples 1-6, showing that the alloy has a nanocrystalline and very small amount of amorphous structure.

[0049] The alloys of the above-mentioned different composition examples obtained are mechanically pulverized and passed through a 200-mesh sieve to obtain alloy powders with a diameter ≤ 74 μm. After mixing the alloy powder and nickel carbonyl powder (particle diameter ≤ 2.5 μm) evenly by mass ratio of 1:4, they are cold-pressed into cylindrical electrode sheets with a diameter of 15 mm under a pressure of 35 MPa, and then their electrochemical properties are tested by the standard three-electrode test method.

[0050] The discharge regime used to test the activation performance and maximum discharge capacity of the alloy is: charge-discharge current density is 60 mA / g, charge time is 600 minutes, and discharge cut-off voltage is -0.5 V; the discharge regime used to test the electrochemical cycle stability of the alloy is: charge-discharge current density is 300 mA / g, charge time is 100 minutes, and discharge cut-off voltage is -0.6 V. When the charge-discharge current density is 300 mA / g, the cycle number corresponding to the discharge capacity of the alloy dropping to 60% of the maximum discharge capacity is defined as the cycle life of the alloy. S200 represents the retention rate of the alloy capacity after 200 cycles, that is, S200 = C200,300 / Cmax,300 × 100%. Cmax,300 - the maximum discharge capacity at a charge-discharge current density of 300 mA / g; C200,300 - the discharge capacity after 200 charge-discharge cycles at a charge-discharge current density of 300 mA / g.

[0051] The test results of the alloys prepared in the above examples are listed in Table 1.

[0052] Table 1 Electrochemical properties of the example alloys

[0053] Corresponding embodiment Maximum discharge capacity (mAh / g) <![CDATA[S 200 (%)]]> Cycle life (times) Example 1 577.5 69.8 265 Example 2 510.6 70.4 271 Example 3 521.5 62.5 214 Example 4 533.3 66.2 237 Example 5 538.9 64.9 228 Example 6 564.5 68.9 258 Comparative example 110.4 - -

[0054] The test results show that the electrochemical performance of the alloy, especially the discharge capacity, is much higher than that of the rare earth-based AB5 type alloy (330 mAh / g) currently sold in the market. Compared with similar alloys at home and abroad, the performance of the alloy of this patent, especially the discharge capacity and the electrochemical cycle stability, shows obvious advantages.

[0055] Compared with the traditional RE-Mg-Ni based hydrogen storage alloy and its preparation method, the present invention has the following advantages:

[0056] (1) By adding various metal elements in the composition design, the microstructure is regulated, and the discharge capacity and the electrochemical cycle stability of the alloy are improved.

[0057] (2) By using helium protection, the volatilization loss of metallic magnesium during induction melting is basically avoided, ensuring that the composition of the prepared alloy conforms to the designed component molar ratio.

[0058] (3) Compared with the traditional casting + annealing process, the present invention can completely suppress the composition segregation of the alloy and obtain a uniform microcrystalline-nanocrystalline-amorphous structure. The hydrogen storage alloy with this structure has strong anti-powdering ability and excellent electrochemical cycle stability.

[0059] (4) Since there is basically no composition segregation in the rapidly quenched alloy, the annealing treatment can be omitted, saving costs and improving production efficiency. At the same time, it has the characteristics that the process is easy to master and is suitable for large-scale production.

[0060] (5) By using mechanical Ni coating treatment, the electrocatalytic activity of the alloy is greatly improved, and the alloy has a discharge capacity close to the theoretical capacity. Since a relatively dense Ni coating is formed on the surface of the alloy particles, the corrosion resistance of the alloy in alkaline electrolyte is greatly improved, so that the alloy electrode has good electrochemical cycle stability.

[0061] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-capacity and long-life RE-Mg-Ni-based AB-type hydrogen storage electrode alloy for Ni-MH, characterized in that, Containing multi-transition metal elements Ni, Co, Mn and Al, and rare earth element Ce, with the composition: Mg 10-x Ce x Ni 9-y-z-m Co y Al z Mn m + n wt.%Ni, where x, y, z, m are atomic ratios, and 0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 1, 0 < m ≤ 1, n is the percentage of nano-Ni powder in the alloy, and 40 ≤ n ≤ 60.

2. The electrode alloy according to claim 1, characterized in that, The atomic ratio of the chemical formula composition is: x:y:z:m = 1:0.5:0.5:0.5, n = 50.

3. A preparation method of a multi-component RE-Mg-Ni-based AB type hydrogen storage electrode alloy, characterized in that, Including the following steps: Step 1. Weigh materials according to the chemical formula Mg 10-x Ce x Ni 9-y-z-m Co y Al z Mn m where x, y, z, m are atomic ratios, and 0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 1, 0 < m ≤ 1; Step 2: Add the weighed raw materials into a magnesia crucible in sequence, evacuate the vacuum to 1×10 -2 to 5×10 -5 Pa, then fill with a protective gas at a pressure of 0.01 to 0.1 MPa, and heat to 1500 - 1600 °C by induction heating method to obtain molten Mg 10-x Ce x Ni 9-y-z-m Co y Al z Mn m liquid alloy; Step 3: Directly inject the liquid alloy prepared in the above Step 2 into the tundish with a BN nozzle embedded at the bottom. Through the slit of the BN nozzle at the bottom of the tundish, the liquid alloy continuously drops onto the smooth surface of the rotating copper roller to obtain a rapidly quenched alloy thin strip with a thickness between 50 - 300 μm. The rapidly quenched strip has a nanocrystalline structure with a grain size of 10 - 100 nm; Step 4: Mechanically crush and screen the rapidly quenched Mg 10-x Ce x Ni 9-y-z-m Co y Al z Mn m alloy ribbon to obtain alloy powder by screening. Then, load the screened alloy powder, nano-Ni powder and stainless steel grinding balls into a stainless steel ball milling tank. After evacuating, fill it with high-purity argon and ball mill in an all-round planetary high-energy ball mill to obtain a hydrogen storage electrode alloy in powder form; where the value of the mass percentage n of nano-Ni powder in the alloy is 40 ≤ n ≤ 60.

4. The preparation method of the hydrogen storage electrode alloy according to claim 3, characterized in that, In the above Step 1, the atomic ratio is: x:y:z:m = 1:0.5:0.5:0.5, n = 50.

5. The preparation method of the hydrogen storage electrode alloy according to claim 3, characterized in that, In the above Step 2, the protective gas is high-purity helium or a mixed gas of helium and argon with a volume ratio of 1:

1.

6. The preparation method of the hydrogen storage electrode alloy according to claim 3, characterized in that, In the above Step 3, the copper roller rotates at a linear speed of 5 - 30 m / s.

7. The preparation method according to claim 3, characterized in that: Step 4: Ball mill for 3 - 10 hours in an all-round planetary high-energy ball mill, with a ball-to-material ratio of 20:1 and a rotation speed of 350 revolutions per minute. During the ball milling process, the ball mill stops for 0.5 hours every 1 hour of continuous operation.

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