A method for preparing a Co-doped CeO2 / Nd-Fe-B composite electrode material

Abstract

This invention relates to the field of electrode materials technology, specifically disclosing a method for preparing a Co-doped CeO2 / Nd-Fe-B composite electrode material. The invention involves preparing Co-doped CeO2 powder via a hydrothermal method and preparing Nd-Fe-B through a mixing and melting process. 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy, and then the obtained Co-CeO2 powder is mixed with Nd 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder is mixed, ball-milled, and pressed to obtain Co-doped CeO2 / Nd-Fe-B composite electrode material. The present invention is simple, easy to implement, and low in cost, while greatly improving the discharge capacity of the composite electrode material.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and more specifically, to a method for preparing a Co-doped CeO2 / Nd-Fe-B composite electrode material. Background Technology

[0002] Hydrogen, as a secondary clean energy source, boasts high energy density and sustainability. The development of hydrogen energy has indirectly promoted the development of metal hydrides, which are intermetallic compounds formed when elemental hydrogen passes through the crystal lattice of certain transition metals. These compounds store hydrogen atoms to achieve electronic energy storage, thus serving as the core energy storage component in power batteries. However, the current challenge facing the development of new energy vehicles is how to achieve sustainable, low-cost, high-rate, and environmentally friendly electrochemical energy storage devices. Therefore, it is necessary to develop a novel, market-competitive anode material to enhance the position of nickel-metal hydride batteries in the power battery field.

[0003] In improving the electrochemical performance of nickel-metal hydride (NiMH) batteries, the research on NiMH anode materials is the primary issue, followed by NiMH cathodes, separators, and electrolytes. The key to improving anode performance lies in enhancing the performance of the hydrogen storage alloy material. Currently, the most common NiMH anode hydrogen storage alloys in research include LaNi5-based AB5 alloys, ZrM2 and TiM2-based AB2 alloys, Ti-V-based solid solution alloys, and rare-earth-magnesium-nickel (La-Mg-Ni)-based ABn alloys. AB5-type hydrogen storage alloys were the first to be commercially used in NiMH battery anodes; however, research has found that LaNi5-type alloys have poor cycle stability, failing to meet practical application requirements. AB-type (TiFe) and AB2-type (ZrM2 and TiM2) alloys are second-generation hydrogen storage electrode alloys; however, activation of these alloys is very difficult, requiring multiple hydrogen absorption / desorption cycles at high temperatures. V-based solid solution alloys with a BCC structure can also be used as hydrogen storage alloys. V can absorb / desorb hydrogen at room temperature and pressure, but V-based alloys also suffer from difficulties in activation and poor kinetic properties.

[0004] AB 3.0-3.8 Hydrogen storage alloys are a novel type of hydrogen storage material discovered in recent years. Typical examples include LaNi3-type and CaNi3-type alloys. These alloys are mostly multiphase structures, with basic unit phases such as AB5, AB2, and A2B7. Compared to alloys with a simple AB5 structure, these multiphase alloys exhibit more significant electrochemical advantages. Further research on this type of alloy revealed that its multiphase structure, along with annealing or element substitution, improves its performance. However, these alloys also suffer from poor cycle stability. Subsequent studies have shown that replacing AB5 with rare earth elements...3.8 The method for replacing the element La in the alloy revealed that replacing it with rare earth elements such as cerium and neodymium can correspondingly improve the cycle stability of the alloy.

[0005] In recent years, La-Fe-B hydrogen storage alloys have been gradually developed and researched. Their activation performance and high-rate discharge performance are superior to traditional LaNi5 alloys, meeting the requirements of power batteries and suitable for developing low-cost MH-Ni batteries. Due to the unique multiphase structure of La-Fe-B hydrogen storage materials, their kinetic performance and low-temperature discharge performance are significantly better than LaNi5 alloys, making them very suitable for developing MH-Ni power batteries and low-temperature batteries. However, La-Fe-B hydrogen storage alloys still have drawbacks such as poor cycle stability and low-rate performance.

[0006] Therefore, it is necessary to design a method for preparing Co-doped CeO2 / Nd-Fe-B composite electrode materials to solve the problems of poor cycle stability and high-rate performance, small discharge capacity, and complex and costly processes of existing La-Fe-B system hydrogen storage alloy electrode materials. Summary of the Invention

[0007] In view of this, the present invention proposes a method for preparing Co-doped CeO2 / Nd-Fe-B composite electrode materials to solve the problems of poor cycle stability and high-rate performance, small discharge capacity, and complex and costly processes of existing La-Fe-B system hydrogen storage alloy electrode materials.

[0008] On the one hand, this invention proposes a method for preparing a Co-doped CeO2 / Nd-Fe-B composite electrode material, comprising the following preparation steps:

[0009] Cerium nitrate hexahydrate is dissolved in ethylene glycol to obtain a first mixed solution. Cobalt nitrate hexahydrate is dissolved in water to obtain a second mixed solution. The first and second mixed solutions are stirred to obtain a third mixed solution.

[0010] Glacial acetic acid is added to water and stirred to obtain a fourth mixed solution. The fourth mixed solution is added to the third mixed solution and stirred for a second time. Then it is heated and centrifuged to obtain a first mixture. The first mixture is pretreated to obtain Co-CeO2 powder.

[0011] Nd, Pr, Fe, Ni, B, and Al were mixed and smelted in a molar ratio of 10:8:4:60:2:2.4. After smelting, the mixture was allowed to cool naturally to obtain Nd. 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy, with the Nd 10 Pr8Fe4Ni 60B2Al 2.4 The hydrogen storage alloy was pulverized, ground, and sieved to obtain Nd. 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder;

[0012] The Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder is mixed, ground, and then pressed into sheets to obtain the Co-doped CeO2 / Nd-Fe-B composite electrode material.

[0013] Furthermore, the mass ratio of cerium nitrate hexahydrate to cobalt nitrate hexahydrate is 10:(1-4).

[0014] Furthermore, the pretreatment specifically involves washing the first mixture three times with water and ethanol respectively, then drying it at 60°C, and finally calcining it at 350°C for 1 hour after drying.

[0015] Furthermore, the stirring time for the first stirring is 5 minutes; the stirring time for the second stirring is 30 minutes.

[0016] Furthermore, the melting process specifically involves: arc melting under an argon atmosphere, with the melting process repeated four times.

[0017] Furthermore, the Co-CeO2 powder and Nd... 10 Pr8Fe4Ni 60 B2Al 2.4 The mass ratio of the hydrogen storage alloy powder is (1-3):(97-99).

[0018] Furthermore, the mixing and grinding is carried out using ball milling with a ball-to-material ratio of 35:1 and a mixing and grinding time of 15 minutes.

[0019] Furthermore, the volume ratio of glacial acetic acid to water is 1:1.

[0020] Furthermore, the heating temperature is 180°C, and the heating time is 3 hours.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: This application combines Co-CeO2 powder with Nd... 10 Pr8Fe4Ni 60 B2Al 2.4Hydrogen storage alloy powder was mixed and ground to prepare a Co-doped CeO2 / Nd-Fe-B composite electrode material. The nanoscale structure of the Co-CeO2 powder improved the rate of surface redox reactions and electrochemical kinetics, thereby increasing the storage capacity and thus improving the discharge capacity of the composite electrode material of the present invention. The presence of cobalt on the surface of the composite electrode material promotes charge transfer by reducing the resistance between the electrode and the electrolyte. In the electrochemical reaction that occurs at the negative electrode during charging and discharging, cerium dioxide participates in the electrochemical reaction and plays a role in charge transfer, which increases the exchange current density of the composite electrode material of the present invention, thereby improving the high-rate discharge performance and cycle stability. At the same time, the presence of CeO2 and Co-CeO2 coatings on the surface of the composite electrode material of this application helps to enhance corrosion resistance in alkaline electrolytes.

[0022] On the other hand, the present invention also provides a nickel-metal hydride battery, wherein the negative electrode of the nickel-metal hydride battery is made of the Co-doped CeO2 / Nd-Fe-B composite electrode material. Attached Figure Description

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0024] Figure 1 The graphs show the relationship between discharge capacity and cycle number for test examples 1-3 and control examples of this invention.

[0025] Figure 2 HRD diagrams of alloy electrodes from Test Examples 1-3 and the Control Example of this invention

[0026] Figure 3 XRD patterns of alloy electrodes from Test Examples 1-3 and the Control Example of this invention

[0027] Figure 4 A flowchart illustrating the preparation method of the Co-doped CeO2 / Nd-Fe-B composite electrode material provided in this embodiment of the invention. Detailed Implementation

[0028] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] On the one hand, such as Figure 4 As shown in some embodiments of this application, a method for preparing a Co-doped CeO2 / Nd-Fe-B composite electrode material includes the following preparation steps:

[0030] Cerium nitrate hexahydrate is dissolved in ethylene glycol to obtain a first mixed solution. Cobalt nitrate hexahydrate is dissolved in water to obtain a second mixed solution. The first and second mixed solutions are stirred to obtain a third mixed solution.

[0031] Glacial acetic acid is added to water and stirred to obtain a fourth mixed solution. The fourth mixed solution is added to the third mixed solution and stirred for a second time. Then it is heated and centrifuged to obtain a first mixture. The first mixture is pretreated to obtain Co-CeO2 powder.

[0032] Nd, Pr, Fe, Ni, B, and Al were mixed and smelted in a molar ratio of 10:8:4:60:2:2.4. After smelting, the mixture was allowed to cool naturally to obtain Nd. 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy, with the Nd 10 Pr8Fe4Ni 60 B2Al 2.4 The hydrogen storage alloy was pulverized, ground, and sieved to obtain Nd. 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder;

[0033] The Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder is mixed and ground to obtain the Co-doped CeO2 / Nd-Fe-B composite electrode material.

[0034] Specifically, the purity of Nd, Pr, Fe, Ni, B, and Al is higher than 99.9%; the water is preferably deionized water.

[0035] Specifically, the fourth mixed solution is added to the third mixed solution and stirred for a second time before being transferred to a polytetrafluoroethylene-lined autoclave for heating.

[0036] Specifically, a 200-mesh sieve is used for sieving; the amount of ethylene glycol and cerium nitrate hexahydrate used is 30 ml of ethylene glycol for every 1 g of cerium nitrate hexahydrate.

[0037] It is understandable that this application involves mixing Co-CeO2 powder with Nd... 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder was mixed and ground to prepare a Co-doped CeO2 / Nd-Fe-B composite electrode material. The nanoscale structure of the Co-CeO2 powder improved the rate of surface redox reactions and electrochemical kinetics, thereby increasing the storage capacity and thus improving the discharge capacity of the composite electrode material of the present invention. The presence of cobalt on the surface of the composite electrode material promotes charge transfer by reducing the resistance between the electrode and the electrolyte. In the electrochemical reaction that occurs at the negative electrode during charging and discharging, cerium dioxide participates in the electrochemical reaction and plays a role in charge transfer, which increases the exchange current density of the composite electrode material of the present invention, thereby improving the high-rate discharge performance and cycle stability. At the same time, the presence of CeO2 and Co-CeO2 coatings on the surface of the composite electrode material of this application helps to enhance corrosion resistance in alkaline electrolytes.

[0038] In some embodiments of this application, the mass ratio of cerium nitrate hexahydrate to cobalt nitrate hexahydrate is 10:(1-4); the preferred mass ratio is 10:2.

[0039] In some embodiments of this application, the pretreatment specifically involves washing the first mixture three times with water and ethanol respectively, then drying it at 60°C, and finally calcining it at 350°C for 1 hour after drying; the water is preferably deionized water.

[0040] Understandably, alternating washing with water and ethanol three times effectively removes residual nitrate ions, ethylene glycol, glacial acetic acid, and other precursor solvents and reaction byproducts from the sample surface, preventing impurities from adversely affecting the material's crystal structure and chemical properties. The 60℃ low-temperature drying process ensures the full evaporation of adsorbed water and residual ethanol while preventing precursor decomposition or nanoparticle agglomeration caused by high temperatures. Subsequent calcination at 350℃ under an argon atmosphere for 1 hour further inhibits Ce2 oxidation. 3+The oxidation of low-valence ions maintains the target doping valence state; on the other hand, this temperature can promote the transformation of amorphous precursors into a crystalline CeO2 matrix, while allowing Co ions to diffuse uniformly into the CeO2 lattice to form a stable solid solution, effectively improving the crystallinity and structural uniformity of the material, and giving Co-CeO2 powder better catalytic activity and thermal stability.

[0041] In some embodiments of this application, the stirring time of the first stirring is 5 minutes; the stirring time of the second stirring is 30 minutes.

[0042] In some embodiments of this application, the melting process specifically involves: arc melting under an argon atmosphere, with the melting process repeated four times.

[0043] Specifically, Nd, Pr, Fe, Ni, B, and Al are mixed in a molar ratio of 10:8:4:60:2:2.4, and then placed in a copper crucible in order of increasing melting point from bottom to top in a melting furnace. The crucible is then melted in an argon atmosphere using an electric arc furnace. To ensure the uniformity of the alloy, the alloy is turned over and melted four times.

[0044] In some embodiments of this application, the Co-CeO2 powder and Nd... 10 Pr8Fe4Ni 60 B2Al 2.4 The mass ratio of the hydrogen storage alloy powder is (1-3):(97-99), and the preferred mass ratio is 1:99.

[0045] In some embodiments of this application, ball milling is used for the mixed grinding, with a ball-to-material ratio of 35:1 and a grinding time of 15 minutes.

[0046] Specifically, the Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder was placed in a ball mill jar with a ball-to-powder ratio of 35:1. High-purity argon gas was introduced into the ball mill jar, which was then placed in a high-energy ball mill. The effective ball milling time was set to 15 minutes.

[0047] In some embodiments of this application, the volume ratio of glacial acetic acid to water is 1:1.

[0048] In some embodiments of this application, the heating temperature is 180°C and the heating time is 3 hours.

[0049] On the other hand, some embodiments of the present invention also provide a nickel-metal hydride battery, wherein the negative electrode is made of the Co-doped CeO2 / Nd-Fe-B composite electrode material.

[0050] Example 1

[0051] S1. Dissolve 1g of cerium nitrate hexahydrate in 30ml of ethylene glycol to obtain the first mixed solution. Dissolve 0.1g of cobalt nitrate hexahydrate in 0.92ml of deionized water to obtain the second mixed solution. Mix the first mixed solution and the second mixed solution and stir for 5 minutes to obtain the third mixed solution.

[0052] S2. Add 1 ml of glacial acetic acid to 1 ml of deionized water and stir to obtain the fourth mixed solution. Mix the third mixed solution with the fourth mixed solution and stir for 30 minutes. Then transfer the mixture to a polytetrafluoroethylene-lined autoclave and heat at 180°C for 3 hours. Centrifuge the mixture, wash it three times with deionized water and ethanol, and dry it at 60°C. Calcine the dried sample in a tube furnace at 350°C under an argon atmosphere for 1 hour to obtain Co-CeO2 powder.

[0053] S3. Nd, Pr, Fe, Ni, B, and Al are placed in a melting furnace in a molar ratio of 10:8:4:60:2:2.4, arranged from bottom to top according to their melting points, in a copper crucible cooled and protected by circulating water. The alloy is then melted by electric arc under an argon atmosphere, with the crucible being turned over four times. After the alloy has cooled naturally, it is removed and mechanically crushed and ground, then sieved through a 200-mesh sieve to obtain Nd. 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder;

[0054] S4. The Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder was added to a ball mill jar at a mass ratio of 1:99, with a ball-to-material ratio of 35:1. High-purity argon gas was introduced into the ball mill jar, which was then placed in a high-energy ball mill. The effective ball milling time was set to 15 minutes to obtain Co-doped CeO2 / Nd-Fe-B composite electrode material.

[0055] Example 2

[0056] S1. Dissolve 1g of cerium nitrate hexahydrate in 30ml of ethylene glycol to obtain the first mixed solution. Dissolve 0.2g of cobalt nitrate hexahydrate in 0.92ml of deionized water to obtain the second mixed solution. Mix the first mixed solution and the second mixed solution and stir for 5 minutes to obtain the third mixed solution.

[0057] S2. Add 1 ml of glacial acetic acid to 1 ml of deionized water and stir to obtain the fourth mixed solution. Mix the third mixed solution with the fourth mixed solution and stir for 30 minutes. Then transfer the mixture to a polytetrafluoroethylene-lined autoclave and heat at 180°C for 3 hours. Centrifuge the mixture, wash it three times with deionized water and ethanol, and dry it at 60°C. Calcine the dried sample in a tube furnace at 350°C under an argon atmosphere for 1 hour to obtain Co-CeO2 powder.

[0058] S3. Nd, Pr, Fe, Ni, B, and Al are placed in a melting furnace in a molar ratio of 10:8:4:60:2:2.4, arranged from bottom to top according to their melting points, in a copper crucible cooled and protected by circulating water. The alloy is then melted by electric arc under an argon atmosphere, with the crucible being turned over four times. After the alloy has cooled naturally, it is removed and mechanically crushed and ground, then sieved through a 200-mesh sieve to obtain Nd. 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder;

[0059] S4. The Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder was added to a ball mill jar at a mass ratio of 2:98 and a ball-to-material ratio of 35:1. High-purity argon gas was introduced into the ball mill jar, which was then placed in a high-energy ball mill. The effective ball milling time was set to 15 minutes to obtain Co-doped CeO2 / Nd-Fe-B composite electrode material.

[0060] Example 3

[0061] S1. Dissolve 1g of cerium nitrate hexahydrate in 30ml of ethylene glycol to obtain the first mixed solution. Dissolve 0.4g of cobalt nitrate hexahydrate in 0.92ml of deionized water to obtain the second mixed solution. Mix the first mixed solution and the second mixed solution and stir for 5 minutes to obtain the third mixed solution.

[0062] S2. Add 1 ml of glacial acetic acid to 1 ml of deionized water and stir to obtain the fourth mixed solution. Mix the third mixed solution with the fourth mixed solution and stir for 30 minutes. Then transfer the mixture to a polytetrafluoroethylene-lined autoclave and heat at 180°C for 3 hours. Centrifuge the mixture, wash it three times with deionized water and ethanol, and dry it at 60°C. Calcine the dried sample in a tube furnace at 350°C under an argon atmosphere for 1 hour to obtain Co-CeO2 powder.

[0063] S3. Nd, Pr, Fe, Ni, B, and Al are placed in a melting furnace in a molar ratio of 10:8:4:60:2:2.4, arranged from bottom to top according to their melting points, in a copper crucible cooled and protected by circulating water. The alloy is then melted by electric arc under an argon atmosphere, with the crucible being turned over four times. After the alloy has cooled naturally, it is removed and mechanically crushed and ground, then sieved through a 200-mesh sieve to obtain Nd. 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder;

[0064] S4. The Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder was added to a ball mill jar at a mass ratio of 3:97 and a ball-to-material ratio of 35:1. High-purity argon gas was introduced into the ball mill jar, which was then placed in a high-energy ball mill. The effective ball milling time was set to 15 minutes to obtain Co-doped CeO2 / Nd-Fe-B composite electrode material.

[0065] Experimental Example 1

[0066] The Co-doped CeO2 / Nd-Fe-B composite electrode material prepared in Example 1 was cold-pressed with carbonyl nickel powder to form a circular alloy electrode with a diameter of 1 cm and a thickness of 0.1–0.15 cm. The alloy electrode was then spot-welded to a conductive nickel wire to form the negative electrode of the battery. The positive electrode was a sintered nickel hydroxide (Ni(OH)2 / NiOOH) electrode sheet, and the electrolyte was a 6 mol / L KOH solution.

[0067] Experimental Example 2

[0068] The Co-doped CeO2 / Nd-Fe-B composite electrode material prepared in Example 2 was cold-pressed with carbonyl nickel powder to form a circular alloy electrode with a diameter of 1 cm and a thickness of 0.1–0.15 cm. The alloy electrode was then spot-welded to a conductive nickel wire to form the negative electrode of the battery. The positive electrode was a sintered nickel hydroxide (Ni(OH)2 / NiOOH) electrode sheet, and the electrolyte was a 6 mol / L KOH solution.

[0069] Experimental Example 3

[0070] The Co-doped CeO2 / Nd-Fe-B composite electrode material prepared in Example 3 was cold-pressed with carbonyl nickel powder to form a circular alloy electrode with a diameter of 1 cm and a thickness of 0.1–0.15 cm. The alloy electrode was then spot-welded to a conductive nickel wire to form the negative electrode of the battery. The positive electrode was a sintered nickel hydroxide (Ni(OH)2 / NiOOH) electrode sheet, and the electrolyte was a 6 mol / L KOH solution.

[0071] Comparative Example

[0072] Nd 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder, used as a reference alloy, was cold-pressed with carbonyl nickel powder to prepare a circular electrode with a diameter of 1 cm and a thickness of 0.1–0.15 cm. The circular electrode was then spot-welded to a conductive nickel wire to form the negative electrode of the battery. The positive electrode was a sintered nickel hydroxide (Ni(OH)₂ / NiOOH) electrode sheet, and the electrolyte was a 6 mol / L KOH solution.

[0073] Effect detection:

[0074] 1. Electrochemical performance tests were conducted on the batteries assembled in Examples 1-3 and the comparative examples, including degradation performance, maximum discharge capacity, and rate performance. Maximum discharge capacity and activation performance were tested at charge and discharge current densities of 60 mA / g. High-rate performance was first assessed by activating the battery at a charge and discharge current density of 60 mA / g, followed by charging at a current density of 60 mA / g, and then discharging sequentially at discharge current densities of 120 mA / g, 180 mA / g…600 mA / g. The rate discharge performance was determined based on the resulting discharge capacity ratio.

[0075] The results are as follows Figure 1-2 As shown:

[0076] from Figure 1 It can be seen that the maximum discharge capacity of the composite electrode material is significantly better than that of the reference alloy;

[0077] from Figure 2It can be seen that adding an appropriate amount of Co-CeO2 improves the high-rate discharge performance of the composite alloy. The hydrogen storage alloys with 1wt% and 2wt% Co-CeO2 additions exhibit better high-rate discharge performance than the reference alloy. However, when the addition amount is 3wt%, the composite material's rate performance is significantly worse than the reference alloy at a discharge current density greater than 240 mA / g. Due to the high catalytic activity and appropriate conductivity of Co-CeO2, charge transfer and hydrogen transfer within the alloy are accelerated, allowing hydrogen atoms to diffuse more quickly from the alloy surface into the alloy interior. However, excessive Co-CeO2 addition makes the alloy prone to pulverization, which is detrimental to improving the high-rate discharge performance of the alloy electrode.

[0078] 2. XRD analysis was performed on the alloy electrodes of Test Examples 1-3 and the reference sample in the comparative examples.

[0079] The results are as follows Figure 3 As shown:

[0080] from Figure 3 It can be seen that the alloy composite material is a multiphase alloy, including Nd2Ni7, NdNi5 and Nd2Fe. 14 Phase B. The Nd2Ni7 and NdNi5 phases are the phase structures that can function as hydrogen storage phases. It is evident that the addition of Co-CeO2 did not change the phase structure of the alloy. When the Co-CeO2 addition amount was 1wt% and 2wt%, the diffraction peak height of the alloy composite material increased significantly, indicating an increase in the crystallinity of the alloy, which explains the increase in the maximum discharge capacity of the alloy composite material after the addition of graphene. However, when the addition amount was 3wt%, the diffraction peak height of the alloy composite material decreased significantly. This trend is consistent with the changes in the cycle performance curves and high-rate discharge performance curves mentioned above.

[0081] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a Co-doped CeO2 / Nd-Fe-B composite electrode material, characterized in that, The preparation steps include the following: Cerium nitrate hexahydrate is dissolved in ethylene glycol to obtain a first mixed solution. Cobalt nitrate hexahydrate is dissolved in water to obtain a second mixed solution. The first and second mixed solutions are stirred to obtain a third mixed solution. Glacial acetic acid is added to water and stirred to obtain a fourth mixed solution. The fourth mixed solution is added to the third mixed solution and stirred for a second time, then heated and centrifuged to obtain a first mixture. The first mixture is pretreated to obtain Co-CeO2 powder. Nd, Pr, Fe, Ni, B, and Al were mixed and smelted in a molar ratio of 10:8:4:60:2:2.

4. After smelting, the mixture was allowed to cool naturally to obtain Nd. 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy, with the Nd 10 Pr8Fe4Ni 60 B2Al 2.4 The hydrogen storage alloy was pulverized, ground, and sieved to obtain Nd. 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder; The Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2Al 2.4 Hydrogen storage alloy powder is mixed and ground to obtain the Co-doped CeO2 / Nd-Fe-B composite electrode material.

2. The preparation method of the Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 1, characterized in that, The mass ratio of cerium nitrate hexahydrate to cobalt nitrate hexahydrate is 10:(1-4).

3. The preparation method of the Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 2, characterized in that, The pretreatment specifically involves washing the first mixture three times with water and ethanol respectively, then drying it at 60°C, and finally calcining it at 350°C for 1 hour after drying.

4. The preparation method of the Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 3, characterized in that, The stirring time for the first mixer is 5 minutes; the stirring time for the second mixer is 30 minutes.

5. The preparation method of the Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 4, characterized in that, The melting process specifically involves arc melting under an argon atmosphere, with the melting process repeated four times.

6. The preparation method of the Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 5, characterized in that, The Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2Al 2.4 The mass ratio of the hydrogen storage alloy powder is (1-3):(97-99).

7. The method for preparing the Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 6, characterized in that, The mixing and grinding process is carried out using ball milling with a ball-to-material ratio of 35:1 and a mixing and grinding time of 15 minutes.

8. The method for preparing the Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 7, characterized in that, The volume ratio of glacial acetic acid to water is 1:

1.

9. The method for preparing the Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 8, characterized in that, The heating temperature is 180°C, and the heating time is 3 hours.

10. A nickel-metal hydride battery, characterized in that, The negative electrode is prepared from the Co-doped CeO2 / Nd-Fe-B composite electrode material as described in any one of claims 1-9.

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