A rare earth-magnesium-nickel based hydrogen storage electrode material and preparation method thereof

Abstract

This application relates to the technical field of nickel-metal hydride secondary battery electrode materials, and specifically relates to a rare earth-magnesium-nickel-based hydrogen storage electrode material and a preparation method thereof. The present invention provides a rare earth-magnesium-nickel-based hydrogen storage electrode material that can improve the discharge characteristics of nickel-metal hydride secondary batteries at low temperatures. This material has an A5B 19 type superlattice structure, with the general formula M 1‑a Mg a Ni x Al y N z . In the X-ray diffraction pattern of this hydrogen storage material, the relative intensity of the maximum peak P1 appearing in the range of 2θ = 30.20° - 30.45° is greater than 4.00% and less than 10.00%. The relative intensity of the maximum peak P2 appearing in the range of 2θ = 31.45° - 31.75° is greater than 5.00% and less than 15.00%. In the range of 2θ = 31.45° - 33.00°, a broad signal is exhibited, and its maximum relative intensity is greater than 1.50% and less than 7.00%. The relative intensity of the maximum peak P3 appearing in the range of 2θ = 33.00° - 33.20° is greater than 2.00% and less than 10.00%. This material has a high discharge capacity at both room temperature and -30°C low temperature.

Description

Technical Field

[0001] The invention relates to the technical field of nickel-hydrogen secondary battery electrode materials, and in particular to a rare earth-magnesium-nickel based hydrogen storage electrode material and a preparation method thereof. Background Art

[0002] Nickel-hydrogen secondary batteries have high energy density and are environmentally friendly. They are mainly used in portable electronic devices, power tools, hybrid vehicles, etc. In recent years, they are more commonly used in hybrid vehicles. Considering the large temperature difference in the use environment, nickel-hydrogen secondary batteries need to have good discharge performance even at low temperatures. The key to achieving this goal is to improve the performance of the negative electrode hydrogen storage material.

[0003] In hydrogen storage alloy materials, rare earth AB 5 The alloy has been widely used in nickel-hydrogen secondary batteries and can be industrialized, but its theoretical discharge capacity is low, only about 340 mAh / g. The crystal structure of superlattice rare earth hydrogen storage alloy is [A 2 B 4 ] and [AB 5 ] The subunits are periodically stacked along the c-axis, with AB 2 Type alloy high capacity and AB 5 The alloy has the advantages of easy activation and good high current discharge capacity, which is a good alternative to traditional AB 5 As a new generation of materials for the negative electrode of nickel-hydrogen secondary batteries, La-Y-Ni alloy and La-Mg-Ni alloy are the most common. For example, Chinese patent CN110317974A discloses an A 5 B 19 Phase yttrium-nickel rare earth hydrogen storage alloy, Chinese patent CN106086569A discloses an A 2 B 7 and A 5 B 19 Among these two types of alloys, magnesium-based hydrogen storage alloy materials have high theoretical electrochemical capacity and better cycle stability, and have been commercially applied in small nickel-hydrogen secondary batteries. Therefore, in order to meet the application and industrial needs of nickel-hydrogen power batteries, rare earth magnesium-nickel hydrogen storage materials have more industrial development prospects, but the low-temperature discharge performance of rare earth magnesium-nickel Cu-Kα hydrogen storage materials still needs to be improved.

[0004] When the superlattice rare earth hydrogen storage alloy [AB 5 ] and [A 2 B 4 ] subunit ratios are different, and with [AB 5 ] When the subunit ratio increases, AB 3 , A 2 B 7 , A5 B 19 Generally, as the stoichiometric ratio of the elements on the B side of the structure increases, the rate performance, low-temperature discharge performance, and cycle performance of the alloy are improved. For example, Chinese patent CN108172807A discloses a multi-element single-phase A 5 B 19 The superlattice hydrogen storage alloy electrode material shows good discharge performance: the maximum discharge capacity is ≥363 mAh / g, the capacity retention rate is ≥88.8% after 100 charge and discharge cycles, the capacity retention rate is ≥80% after 200 charge and discharge cycles, and HRD1500 is ≥58.2%. 2 B 4 ] There are two different subunit configurations, and the phase structures with different stoichiometric ratios are also divided into 3R and 2H types. Since the structures are very similar and have similar formation energies, 3R and 2H phase structures usually coexist. Slight changes in stoichiometry and subunit type represent significant changes in structure, which have an important impact on both hydrogen storage and electrochemical properties. Among them, the low-temperature performance of the alloy is better when multiple phases coexist, but the single-phase alloy has good cycle stability and high capacity. Therefore, it is now necessary to develop a hydrogen storage alloy with good cycle stability, high capacity and good low-temperature discharge performance. Summary of the invention

[0005] Therefore, based on the existing technology, in order to provide an A-type quartz crystal with simple preparation method, good cycle stability, high capacity and good low temperature discharge performance, 5 B 19 The present invention provides a rare earth-magnesium-nickel based hydrogen storage electrode material and a preparation method thereof:

[0006] A rare earth-magnesium-nickel based hydrogen storage electrode material, the general formula of the hydrogen storage electrode material is M 1-a Mg a Ni x Al y N z ;

[0007] Wherein M is one or more of rare earth elements, Y, and Sc, and N is one or more of Ti, V, Cr, Mo, W, Mn, Fe, Co, Cu, Zn, C, Si, and P; wherein 0.15≤a≤0.25, 0.05≤y≤0.20, 0≤z≤0.50, and 3.5≤x+y+z≤3.8;

[0008] The hydrogen storage electrode material has A 5 B 19 Type superlattice structure;

[0009] In the X-ray diffraction spectrum of the hydrogen storage electrode material measured using Cu-Kα rays as the X-ray source, when the relative intensity of the maximum peak among the diffraction peaks appearing in the range of 2θ=42.00°-43.00° is set to 100.00%, the relative intensity of the maximum peak P1 appearing in the range of 2θ=30.20°-30.45° is greater than 4.00% and less than 10.00%, the relative intensity of the maximum peak P2 appearing in the range of 2θ=31.45°-31.75° is greater than 5.00% and less than 15.00%, a broad signal is exhibited in the range of 2θ=31.45°-33.00°, and the maximum relative intensity of the broad signal is greater than 1.50% and less than 7.00%, and the relative intensity of the maximum peak P3 appearing in the range of 2θ=33.00°-33.20° is greater than 2.00% and less than 10.00%.

[0010] Specifically, the maximum relative intensity of a broad signal in the range of 2θ=31.45°-33.00° is greater than 2.00% and less than 5.00%.

[0011] Specifically, the hydrogen storage electrode material is M 1-a Mg a Ni x Al y N z , wherein M is one or more of La, Ce, Pr, Nd, Sm, Y, Gd, Dy, wherein 0.20≤a≤0.25. Preferably, the hydrogen storage electrode material is La c1 Sm 0.2 Y 0.02 Mg a Ni 3.55 Al 0.15 , where 0.53≤c1≤0.58.

[0012] Specifically, the hydrogen storage electrode material is La 0.55 Sm 0.25 Mg 0.20 Ni 3.35 Al 0.15 , La 0.67 Nd 0.10 Mg 0.23 Ni 3.55 Al 0.05 , La 0.70 Y 0.10 Mg 0.2 Ni 3.65 Co 0.05 Al 0.1 .

[0013] A method for preparing the above rare earth-magnesium-nickel based hydrogen storage electrode material comprises the following steps:

[0014] Step 1: Weigh and prepare the metal element or master alloy according to the atomic ratio of the designed composition to obtain the raw material, wherein the amount of Mg added is equivalent to 120%-150% of the Mg amount calculated according to the designed composition of the alloy;

[0015] Step 2: preparing the cast alloy by induction melting method, firstly, evacuating the induction melting furnace to below 1Pa, filling with argon or argon / helium mixed gas as protective gas so that the pressure in the induction melting furnace is 0.01-0.1MPa, melting the raw materials at 1200°C-1500°C until the melt composition is uniform, cooling with a quick-setting copper roller at a cooling rate of 1000-3000°C / s, and obtaining alloy castings;

[0016] Step 3: The alloy casting is sealed and annealed in an argon or helium atmosphere. The annealing process parameters are: first, the temperature is increased from room temperature to 600°C at a heating rate of 5-10°C / min, and then the temperature is immediately increased to 900-980°C at a heating rate of 1-5°C / min. The holding time is 12-72h. Finally, the annealed alloy is naturally cooled to room temperature and taken out.

[0017] Specifically, the design component in step 1 is La c1 Sm 0.2 Y 0.02 Mg a Ni 3.55 Al 0.15 , wherein 0.20≤a≤0.25, 0.53≤c1≤0.58, and the process parameters of the annealing treatment in step 3 are: heating from room temperature to 600°C at a heating rate of 5°C / min, and then immediately heating to 940°C-980°C at a heating rate of 1°C / min, and the holding time is 25h.

[0018] Specifically, the design component in step 1 is La 0.55 Sm 0.25 Mg 0.20 Ni 3.35 Al 0.15 The process parameters of the annealing treatment in step 3 are: heating from room temperature to 600°C at a heating rate of 5°C / min, and then immediately heating to 900°C at a heating rate of 1°C / min, and the holding time is 72h.

[0019] Specifically, the design component in step 1 is La 0.67 Nd 0.10 Mg 0.23 Ni 3.55 Al 0.05The process parameters of the annealing treatment in step 3 are: heating from room temperature to 600°C at a heating rate of 5°C / min, and then immediately heating to 960°C at a heating rate of 1°C / min, and the holding time is 12h.

[0020] Specifically, the design component in step 1 is La 0.70 Y 0.10 Mg 0.2 Ni 3.65 Co 0.05 Al 0.1 The process parameters of the annealing treatment in step 3 are: heating from room temperature to 600°C at a heating rate of 5°C / min, and then immediately heating to 980°C at a heating rate of 1°C / min, and the holding time is 12h.

[0021] The beneficial effects of the present invention are:

[0022] (1) The superlattice rare earth-magnesium-nickel-based hydrogen storage material prepared by the present invention mainly functions to improve the structural stability of the alloy. When its content a is lower than the range specified by the present invention, it is not easy to generate a local mixed stacking structure. When it is higher than the specified range, it is easy to decompose and produce a phase with poor structural stability. Therefore, the magnesium content is preferably 0.20≤a≤0.25; Al helps to improve the corrosion resistance and cycle stability of the material. If its content b is too low, the corrosion resistance will not be improved sufficiently. If it is too high, the discharge capacity of the material will be reduced. x+y+z is the stoichiometric ratio of the elements on the B side. Too high or too low is not conducive to the formation of A 5 B 19 The rare earth hydrogen storage material of the present invention comprises 2H-A 5 B 19 Type and 3R-A 5 B 19 The ratio of the two configurations does not have a special effect on the discharge characteristics at low temperatures.

[0023] (2) The present invention controls the composition and preparation process to prepare a special structure superlattice rare earth-magnesium-nickel based hydrogen storage material with A 5 B 19 At the same time as the main phase structure, the stacking period changes locally, showing a hydrogen storage material with a mixed stacking structure and a specific X-ray diffraction spectrum. The diffraction peaks at P2 and P3 in the X-ray diffraction spectrum are 3R-A 5 B 19 The characteristic peak of the phase, the diffraction peak at P1 is 2H-A 5 B 19 Phase characteristics, broad signal contains 2H-A 5 B 19The characteristic peaks of the phase and the signal peaks generated by the local mixed stacking structure. This special structure can be seen in the 5 B 19 On the basis of the superlattice phase composition, more defects are introduced to increase the phase interface, thereby increasing the diffusion channel of hydrogen in the alloy body, so that the absorption and desorption reaction rate of the alloy at low temperature is improved. The discharge capacity of this material can reach at least 370mA / g at room temperature, and the discharge capacity at low temperature of -30℃ is greater than 315mA / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0025] Figure 1 This is a 1000-fold EPMA image of the hydrogen storage material of Example 1 obtained using EPMA;

[0026] Figure 2 This is a 1000-fold EPMA image of the hydrogen storage material of Comparative Example 1 obtained using EPMA;

[0027] Figure 3 X-ray diffraction patterns of the hydrogen storage materials of Example 1 and Comparative Examples 1-2;

[0028] Figure 4 X-ray diffraction patterns of the hydrogen storage materials of Example 4 and Comparative Example 4;

[0029] Figure 5 X-ray diffraction patterns of the hydrogen storage materials of Example 6 and Comparative Example 5;

[0030] Figure 6 The spherical aberration electron microscope spectrum of the hydrogen storage material of Example 1;

[0031] Figure 7 This is the spherical aberration electron microscope image of the hydrogen storage material of Comparative Example 1. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] The rare earth-magnesium-nickel based hydrogen storage electrode materials described in Examples 1-8 and Comparative Examples 1-5 were prepared in the following manner.

[0034] (1) The alloy elements are weighed and mixed according to the designed atomic ratio to obtain the raw material. Considering the volatility of Mg, the amount of Mg added to the raw material is equivalent to 120%-150% of the Mg amount calculated according to the alloy composition.

[0035] (2) The induction melting furnace is evacuated to below 1Pa, and then an argon protective atmosphere is introduced with a pressure of 0.01-0.1MPa. The prepared alloy raw materials are melted in the induction melting furnace at a melting temperature of 1200℃-1500℃ until the melt composition is uniform to form an alloy melt. The alloy is then quenched and solidified using a quick-setting copper roller at a cooling rate of 1500℃ / s to obtain an alloy casting.

[0036] (3) The obtained alloy casting sheet is sealed and annealed in an argon atmosphere. The specific annealing process is as follows: first, the temperature is raised from room temperature to 600°C at a heating rate of 5°C / min, and then the temperature is further raised to 900°C-980°C at a heating rate of 1°C / min (see Table 1 below for specific temperatures), and the holding time is 12-72h (see Table 1 below for specific time), and finally the alloy after the above annealing treatment is naturally cooled to room temperature and taken out.

[0037] (4) The alloys obtained in the examples and comparative examples were crushed, ground and sieved, and alloy powders in the corresponding particle size range and the remaining block alloy ingots were collected for EPMA, XRD, spherical aberration electron microscopy HAADF atomic phase and electrochemical performance testing.

[0038] Table 1 Chemical composition and preparation process of hydrogen storage electrode materials in Examples and Comparative Examples

[0039]

[0040] Electron Probe Microscopy (EPMA) Test

[0041] The alloy sheets of Examples 1-8 and Comparative Examples 1-5 were embedded in conductive hot-press embedding powder and cured under pressure, and then coarsely ground and precisely ground to a polished mirror surface using a wet grinder to obtain the cross-section required for EPMA testing.

[0042] Figure 1 and Figure 2 The EPMA spectra of the alloy cross-sections of Example 1 and Comparative Example 1 at 1000 times magnification are shown. It can be seen from the figure that the components of Example 1 and Comparative Example 1 are evenly distributed without segregation and impurity. The components at different positions obtained by the energy spectrum are basically the same. The composition of Example 1 is La 0.57 Sm 0.2 Y 0.02 Mg 0.21 Ni 3.55 Al 0.14 , the composition of Comparative Example 1 is La 0.63 Sm 0. 2 Y 0.02 Mg 0.15 Ni 3.55 Al 0.15 , which does not deviate much from the design components.

[0043] X-ray powder diffraction (XRD) test

[0044] The hydrogen storage alloy powder with a mesh size less than 400 was subjected to X-ray diffraction test using Cu-Kα radiation with a power of 40 kV × 300 mA and a step size of 0.02 o , step scanning mode with a dwell time of 1 s per step, and a 2θ angle range of 20 o -80 o The specific results are shown in Table 2.

[0045] Table 2 X-ray diffraction peak characteristics of hydrogen storage electrode materials in Examples and Comparative Examples

[0046]

[0047] Figure 3 The X-ray diffraction patterns of Example 1 and Comparative Examples 1-2 are shown in Table 1. The X-ray diffraction results show that Example 1 and Comparative Example 1 consist of 2H-A 5 B 19 Type and 3R-A 5 B 19 Phase composition, Comparative Example 2 shows AB due to the high magnesium content 5 and AB 3 Different from Comparative Example 1, Example 1 exhibits a broad signal between the P2 and P3 peaks, while Comparative Example 1 has a single diffraction peak at 2θ=32.27°.

[0048] same, Figure 4 and Figure 5 In the embodiment 4 and the embodiment 6, the peaks between P2 and P3 are broad signals, while the comparative example 4 is composed of 2H-A 5 B 19 Type and 3R-A 5 B 19 Phase composition but no broad signal appears, while Comparative Example 5 shows AB 5 and A 2 B 7 Type.

[0049] Spherical aberration electron microscopy HAADF atomic phase map

[0050] The alloy samples were sliced ​​and sampled, and then observed and analyzed at the atomic level using a JEM ARM 200F spherical aberration electron microscope. Figure 6 and Figure 7 The spherical aberration electron microscope spectra of Example 1 and Comparative Example 1 are respectively. Figure 4 As can be seen, Comparative Example 1 is [AB 5 ] subunit and [AB 2 ] subunits are arranged periodically in a ratio of 3:1, and in Example 1 [AB5 ] subunit and [AB 2 In addition to the periodic arrangement of the subunits in a ratio of 3:1, there are also arrangements in a ratio of 2:1 and 1:1, indicating that it produces A 5 B 19 The local mixed stacking structure outside the structure leads to changes in the XRD diffraction pattern, which in turn affects the electrochemical properties of the material.

[0051] Discharge performance test

[0052] Take hydrogen storage alloy powder between 160-200 meshes for discharge performance test. The test process is as follows:

[0053] 200 mg of hydrogen storage alloy powder and 800 mg of carbonyl nickel powder were accurately weighed, uniformly mixed, and cold pressed at 16 MPa for 10 min to prepare Φ The 16 mm × 1 mm electrode sheet was placed in the middle of the folded nickel foam and then cold-pressed and spot-welded to the nickel strip. The test device was a sandwich-type two-electrode test device, with the negative electrode being a hydrogen storage alloy electrode and the auxiliary electrode being [Ni(OH) 2 / NiOOH] electrode, the electrolyte is 6 mol / L KOH alkaline solution, and the test temperature is controlled by a high and low temperature box. The test temperature is room temperature 25℃ and low temperature -30℃.

[0054] After the alloy electrode was left to stand for 24 h under open circuit to ensure sufficient wetting, it was charged at a constant current of 60 mA / g for 450 min at 25°C and -30°C, left to stand for 10 min, and then discharged at a constant current of 60 mA / g with a cutoff potential of -1.0 V and left to stand for 10 min. This cycle was repeated in sequence to achieve the maximum discharge capacity at different temperatures.

[0055] The cyclic stability test method of the alloy is: charge at a constant current of 300 mA / g for 90 min at room temperature, stand for 10 min, then discharge at a constant current of 300 mA / g, with a cut-off potential of -1.0 V, stand for 10 min, and cycle in sequence. The ratio of the remaining discharge capacity to the maximum discharge capacity measured under this condition after 200 cycles of charge and discharge is S 200 The above results are shown in Table 3.

[0056] Table 3 Electrochemical performance test results of hydrogen storage alloy materials of examples and comparative examples

[0057]

[0058] It can be seen from Tables 2 and 3 that Examples 1-8 that meet the characteristics of the XRD spectrum have a discharge capacity of not less than 370 mA / g at room temperature, and a discharge capacity of more than 315 mA / g at a low temperature of -30°C. It can be seen that they have a high discharge capacity at both room temperature and low temperature conditions. Compared with Example 1, Comparative Example 1 has a lower discharge capacity of only 240 mA / g at low temperature due to the lack of a local mixed stacking structure. Due to the increase in magnesium content in Comparative Example 2, the phase composition of the alloy changes after heat treatment at the same temperature, and the discharge capacity at room temperature drops significantly. Compared with Example 4, the heat treatment temperature of Comparative Example 4 is higher than 980°C, which causes the disappearance of the local mixed stacking structure. There is no wide signal peak between P2 and P3 in the XRD spectrum, and its discharge capacity at low temperature is relatively low, only 290 mA / g. Since the heat treatment temperature of Comparative Example 5 is only 850°C, the alloy phase structure is not evenly distributed, except for A 5 B 19 The proportion of other phase structures outside the phase is relatively large, resulting in low discharge capacity at room temperature and low temperature.

[0059] Some exemplary embodiments of the present invention are described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the scheme obtained thereby is still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the protection scope required by the present invention.

Claims

1. A rare earth-magnesium-nickel based hydrogen storage electrode material, characterized in that: The general formula of the hydrogen storage electrode material is M 1-a Mg a Ni x Al y N z ; Wherein M is one or more rare earth elements, N is one or more of Ti, V, Cr, Mo, W, Fe, Co, Cu, Zn, C, Si and P; wherein 0.20≤a≤0.25, 0.05≤y≤0.20, 0≤z≤0.50, 3.5≤x+y+z≤3.8; The hydrogen storage electrode material has A5B 19 Type superlattice structure; In the X-ray diffraction spectrum of the hydrogen storage electrode material measured using Cu-Kα rays as the X-ray source, when the relative intensity of the maximum peak among the diffraction peaks appearing in the range of 2θ=42.00°-43.00° is set to 100.00%, the relative intensity of the maximum peak P1 appearing in the range of 2θ=30.20°-30.45° is greater than 4.00% and less than 10.00%, the relative intensity of the maximum peak P2 appearing in the range of 2θ=31.45°-31.75° is greater than 5.00% and less than 15.00%, a broad signal is exhibited in the range of 2θ=31.45°-33.00°, and the maximum relative intensity of the broad signal is greater than 1.50% and less than 7.00%, and the relative intensity of the maximum peak P3 appearing in the range of 2θ=33.00°-33.20° is greater than 2.00% and less than 10.00%.

2. A rare earth-magnesium-nickel based hydrogen storage electrode material according to claim 1, characterized in that: The maximum relative intensity of a broad signal in the range of 2θ=31.45°-33.00° is greater than 2.00% and less than 5.00%.

3. A rare earth-magnesium-nickel based hydrogen storage electrode material according to claim 1, characterized in that: The hydrogen storage electrode material is M 1-a Mg a Ni x Al y N z , wherein M is one or more of La, Ce, Pr, Nd, Sm, Y, Gd, and Dy.

4. A rare earth-magnesium-nickel based hydrogen storage electrode material according to claim 3, characterized in that: The hydrogen storage electrode material is La c1 Sm 0.2 Y 0.02 Mg a Ni 3.55 Al 0.15 , where 0.53≤c1≤0.

58.

5. A rare earth-magnesium-nickel based hydrogen storage electrode material according to claim 1, characterized in that: The hydrogen storage electrode material is La 0.55 Sm 0.25 Mg 0.20 Ni 3.35 Al 0.15 , La 0.67 Nd 0.10 Mg 0.23 Ni 3.55 Al 0.05 , La 0.70 Y 0.10 Mg 0.2 Ni 3.65 Co 0.05 Al 0.1 .

6. A method for preparing the rare earth-magnesium-nickel based hydrogen storage electrode material according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Weigh and prepare the metal element or master alloy according to the atomic ratio of the designed composition to obtain the raw material, wherein the amount of Mg added is equivalent to 120%-150% of the Mg amount calculated according to the designed composition of the alloy; Step 2: preparing the cast alloy by induction melting method, firstly, evacuating the induction melting furnace to below 1Pa, filling with argon or argon / helium mixed gas as protective gas so that the pressure in the induction melting furnace is 0.01-0.1MPa, melting the raw materials at 1200°C-1500°C until the melt composition is uniform, cooling with a quick-setting copper roller at a cooling rate of 1000-3000°C / s, and obtaining alloy castings; Step 3: The alloy casting is sealed and annealed in an argon or helium atmosphere. The annealing process parameters are: first, the temperature is increased from room temperature to 600°C at a heating rate of 5-10°C / min, and then the temperature is immediately increased to 900-980°C at a heating rate of 1-5°C / min. The holding time is 12-72h. Finally, the annealed alloy is naturally cooled to room temperature and taken out.

7. A method for preparing a rare earth-magnesium-nickel based hydrogen storage alloy electrode material as claimed in claim 6, characterized in that: In step 1, the designed component is La c1 Sm 0.2 Y 0.02 Mg a Ni 3.55 Al 0.15 , wherein 0.20≤a≤0.25, 0.53≤c1≤0.58, and the process parameters of the annealing treatment in step 3 are: heating from room temperature to 600°C at a heating rate of 5°C / min, and then immediately heating to 940°C-980°C at a heating rate of 1°C / min, and the holding time is 25h.

8. A method for preparing a rare earth-magnesium-nickel based hydrogen storage alloy electrode material as claimed in claim 6, characterized in that: In step 1, the designed component is La 0.55 Sm 0.25 Mg 0.20 Ni 3.35 Al 0.15 The process parameters of the annealing treatment in step 3 are: heating from room temperature to 600°C at a heating rate of 5°C / min, and then immediately heating to 900°C at a heating rate of 1°C / min, and the holding time is 72h.

9. A method for preparing a rare earth-magnesium-nickel based hydrogen storage alloy electrode material as claimed in claim 6, characterized in that: In step 1, the designed component is La 0.67 Nd 0.10 Mg 0.23 Ni 3.55 Al 0.05 The process parameters of the annealing treatment in step 3 are: heating from room temperature to 600°C at a heating rate of 5°C / min, and then immediately heating to 960°C at a heating rate of 1°C / min, and the holding time is 12h.

10. A method for preparing a rare earth-magnesium-nickel based hydrogen storage alloy electrode material as claimed in claim 6, characterized in that: The designed component in step 1 is La 0.70 Y 0.10 Mg 0.2 Ni 3.65 Co 0.05 Al 0.1 The process parameters of the annealing treatment in step 3 are: heating from room temperature to 600°C at a heating rate of 5°C / min, and then immediately heating to 980°C at a heating rate of 1°C / min, and the holding time is 12h.

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