Preparation method of Co-doped CeO2 / Nd-Fe-B composite electrode material

Abstract

The invention relates to the technical field of electrode materials, and particularly discloses a Co-doped CeO2 / Nd-Fe-B composite electrode material preparation method, which comprises the following steps: preparing Co-doped CeO2 powder through a hydrothermal method, preparing Nd10Pr8Fe4Ni60B2Al2.4 hydrogen storage alloy through mixed smelting, then mixing the obtained Co-CeO2 powder and Nd10Pr8Fe4Ni60B2Al2.4 hydrogen storage alloy powder, carrying out ball milling, and pressing to obtain the Co-doped CeO2 / Nd-Fe-B composite electrode material. The operation method is simple, convenient and easy to implement, the cost is low, and meanwhile the discharge capacity of the composite electrode material is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and in particular to a method for preparing a Co-doped CeO2 / Nd-Fe-B composite electrode material. Background Art

[0002] As a secondary clean energy source, hydrogen has the characteristics of high energy density and sustainability. The development of hydrogen energy has also indirectly promoted the development of metal hydrides. Metal hydrides are intermetallic compounds formed when elemental hydrogen passes through the lattice of certain transition metals. They achieve the effect of electronic energy storage by storing hydrogen atoms, and are therefore used as the energy storage core of power batteries. However, the current challenge facing the development of new energy vehicles is how to achieve sustainable, low-cost, high-rate, environmentally friendly and pollution-free electrochemical energy storage devices. Therefore, it is necessary to develop a new negative electrode material with market competitiveness to enhance the status of nickel-hydrogen batteries in the field of power batteries.

[0003] In the effort to improve the electrochemical performance of nickel-hydrogen batteries (NiMH) batteries, research on anode materials is a primary concern, followed by the cathode, separator, and electrolyte. The key to improving anode performance lies in improving the properties of the anode hydrogen storage alloy. The most common NiMH battery anode hydrogen storage alloys currently under research include AB5-type alloys based on LaNi5, AB2-type alloys based on ZrM2 and TiM2, Ti-V-based solid solution alloys, and rare earth-magnesium-nickel (La-Mg-Ni)-based ABn-type alloys. AB5-type hydrogen storage alloys were the first commercially available alloys for NiMH battery anodes. However, research has found that LaNi5-type alloys exhibit poor cycling stability, making them unsuitable for practical applications. AB-type (TiFe) and AB2-type (ZrM2 and TiM2) alloys are second-generation hydrogen storage electrode alloys. However, activation of these alloys is difficult, requiring multiple cycles of hydrogen absorption and desorption at high temperatures. V-based solid solution alloys with a BCC structure can also serve as hydrogen storage alloys. V can absorb / desorb hydrogen at room temperature and pressure, but V-based alloys also have the disadvantages of difficulty in activation and poor kinetic properties.

[0004] AB 3.0-3.8 Type hydrogen storage alloy is a new type of hydrogen storage material discovered in recent years. Typical representatives include LaNi3 type alloy and CaNi3 type alloy. This type of alloy is mostly multiphase structure. Their basic unit structure is AB5, AB2, A2B7. Compared with the alloy with simple AB5 structure, the electrochemical advantage of this multiphase structure alloy is more obvious. Further research was conducted on this type of alloy, and it was found that this type of alloy has a multiphase structure. After annealing treatment or after element substitution, the performance of the alloy can be improved accordingly, but this type of alloy also has the characteristic of poor cycle stability. Subsequent studies found that replacing AB with rare earth elements3.8 The method of removing the La element in the alloy found 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 surpass those of traditional LaNi5 alloys, meeting the requirements of power batteries and making them suitable for the development of low-cost MH-Ni batteries. Due to the unique multiphase structure of La-Fe-B hydrogen storage materials, their kinetics and low-temperature discharge performance are significantly superior to those of LaNi5 alloys, making them well-suited for the development of MH-Ni power batteries and low-temperature batteries. However, La-Fe-B hydrogen storage alloys still have drawbacks such as poor cycling stability and high-rate performance.

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

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

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

[0009] dissolving cerium nitrate hexahydrate in ethylene glycol to obtain a first mixed solution, dissolving cobalt nitrate hexahydrate in water to obtain a second mixed solution, and stirring the first mixed solution and the second mixed solution to obtain a third mixed solution;

[0010] adding glacial acetic acid to water and stirring to obtain a fourth mixed solution, adding the fourth mixed solution to the third mixed solution, performing a second stirring, heating, and then centrifuging to obtain a first mixture, and pretreating the first mixture 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, and naturally cooled after the smelting to obtain Nd 10 Pr8Fe4Ni 60 B2A 2.4 Hydrogen storage alloy, the Nd 10 Pr8Fe4Ni 60B2A 2.4 The hydrogen storage alloy was crushed, ground and sieved to obtain Nd 10 Pr8Fe4Ni 60 B2A 2.4 hydrogen storage alloy powder;

[0012] The Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2A 2.4 The hydrogen storage alloy powder is mixed and ground and then pressed into sheets to obtain the Co-doped CeO2 / Nd-Fe-B composite electrode material.

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

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

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

[0016] Furthermore, the smelting is specifically performed as follows: arc melting is performed in an argon atmosphere, and the number of melting times is four times.

[0017] Furthermore, the Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2A 2.4 The mass ratio of the hydrogen storage alloy powder is (1-3): (97-99).

[0018] Furthermore, the mixed grinding was performed by ball milling, with a ball-to-material ratio of 35:1 and a mixed grinding time of 15 minutes.

[0019] Furthermore, the volume ratio of the 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 present invention has the following advantages: 10 Pr8Fe4Ni 60 B2A 2.4Hydrogen storage alloy powders are mixed and ground to prepare Co-doped CeO2 / Nd-Fe-B composite electrode materials. The nanoscale structure of the Co-CeO2 powder increases the rate and electrochemical kinetics of the surface redox reaction, thereby increasing the storage capacity and further increasing 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 occurring at the negative electrode during the charge and discharge process, cerium dioxide participates in the electrochemical reaction and plays a role in charge transfer, thereby increasing 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 the present application helps to enhance the corrosion resistance in alkaline electrolytes.

[0022] On the other hand, the present invention also provides a nickel-hydrogen battery, wherein the negative electrode of the nickel-hydrogen battery is prepared from the Co-doped CeO2 / Nd-Fe-B composite electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0024] Figure 1 The graph is a relationship between the discharge capacity and the number of cycles for Test Examples 1-3 of the present invention and the control example.

[0025] Figure 2 HRD diagrams of the alloy electrodes of Test Examples 1-3 of the present invention and the comparative example

[0026] Figure 3 XRD patterns of the alloy electrodes of Experimental Examples 1-3 and the comparative example of the present invention

[0027] Figure 4 This is a flow chart of a method for preparing a Co-doped CeO2 / Nd-Fe-B composite electrode material provided in an embodiment of the present invention. DETAILED DESCRIPTION

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

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

[0030] dissolving cerium nitrate hexahydrate in ethylene glycol to obtain a first mixed solution, dissolving cobalt nitrate hexahydrate in water to obtain a second mixed solution, and stirring the first mixed solution and the second mixed solution to obtain a third mixed solution;

[0031] adding glacial acetic acid to water and stirring to obtain a fourth mixed solution, adding the fourth mixed solution to the third mixed solution, performing a second stirring, heating, and then centrifuging to obtain a first mixture, and pretreating the first mixture 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, and naturally cooled after the smelting to obtain Nd 10 Pr8Fe4Ni 60 B2A 2.4 Hydrogen storage alloy, the Nd 10 Pr8Fe4Ni 60 B2A 2.4 The hydrogen storage alloy was crushed, ground and sieved to obtain Nd 10 Pr8Fe4Ni 60 B2A 2.4 hydrogen storage alloy powder;

[0033] The Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2A 2.4 The 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 the Nd, Pr, Fe, Ni, B and Al is higher than 99.9%; and the water is preferably deionized water.

[0035] Specifically, the fourth mixed solution is added to the third mixed solution for a second stirring, and then 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 per 1 g of cerium nitrate hexahydrate.

[0037] It is understood that the present invention combines Co-CeO2 powder with Nd 10 Pr8Fe4Ni 60 B2A 2.4 Hydrogen storage alloy powders are mixed and ground to prepare Co-doped CeO2 / Nd-Fe-B composite electrode materials. The nanoscale structure of the Co-CeO2 powder increases the rate and electrochemical kinetics of the surface redox reaction, thereby increasing the storage capacity and further increasing 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 occurring at the negative electrode during the charge and discharge process, cerium dioxide participates in the electrochemical reaction and plays a role in charge transfer, thereby increasing 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 the present application helps to enhance the corrosion resistance in alkaline electrolytes.

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

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

[0040] It is understandable that alternating washing with water and ethanol three times can effectively remove residual nitrate ions, ethylene glycol, glacial acetic acid and other precursor solvents and reaction by-products on the sample surface, avoiding the adverse effects of impurities on the crystal structure and chemical properties of the material. The low-temperature drying process at 60°C can ensure that the adsorbed water and residual ethanol are fully volatilized, and can also prevent the decomposition of the precursor or the agglomeration of nanoparticles caused by high temperature. The subsequent calcination at 350°C in an argon atmosphere for 1 hour, on the one hand, the inert gas environment can inhibit the Ce 3+On the other hand, this temperature can promote the conversion of the amorphous precursor into a CeO2 matrix with complete crystal form, while making the Co ions diffuse evenly into the CeO2 lattice to form a stable solid solution, effectively improving the crystallinity and structural uniformity of the material, and giving the Co-CeO2 powder better catalytic activity and thermal stability.

[0041] In some embodiments of the present 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 the present application, the smelting is specifically: arc melting is performed in an argon atmosphere, and the number of melting times is 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 melting furnace from bottom to top in order of melting point from low to high. They are arc melted in a copper crucible protected by circulating water cooling under an argon atmosphere. To ensure the uniformity of the alloy, the alloy is turned over and melted four times.

[0044] In some embodiments of the present application, the Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2A 2.4 The mass ratio of the hydrogen storage alloy powder is (1-3):(97-99), and the mass ratio is preferably 1:99.

[0045] In some embodiments of the present application, the mixed grinding is performed by ball milling, the ball-to-material ratio is 35:1, and the mixed grinding time is 15 minutes.

[0046] Specifically, the Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2A 2.4 The hydrogen storage alloy powder was placed in a ball mill with a ball-to-material ratio of 35:1. High-purity argon gas was introduced into the ball mill and the ball mill was placed in a high-energy ball mill. The effective milling time of the ball milling process was set to 15 minutes.

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

[0048] In some embodiments of the present 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 further provide a nickel-metal hydride battery, the negative electrode of which is prepared from the Co-doped CeO2 / Nd-Fe-B composite electrode material.

[0050] Example 1

[0051] S1, dissolving 1 g of cerium nitrate hexahydrate in 30 ml of ethylene glycol to obtain a first mixed solution, dissolving 0.1 g of cobalt nitrate hexahydrate in 0.92 ml of deionized water to obtain a second mixed solution, and mixing the first mixed solution and the second mixed solution with stirring for 5 minutes to obtain a third mixed solution;

[0052] S2. Add 1 ml of glacial acetic acid to 1 ml of deionized water and stir to obtain a fourth mixed solution. Mix the third mixed solution and the fourth mixed solution and stir for 30 minutes, then transfer them to a polytetrafluoroethylene-lined autoclave, heat at 180°C for 3 hours, and then centrifuge. Wash three times with deionized water and ethanol, and dry at 60°C. The dried sample is calcined 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 the order of melting point from low to high in the molar ratio of 10:8:4:60:2:2.4, and arc melted in a copper crucible protected by circulating water under an argon atmosphere. The alloy is turned over and melted four times. The melted alloy is naturally cooled and taken out, and is mechanically crushed and ground, and sieved with a 200-mesh sieve to obtain Nd 10 Pr8Fe4Ni 60 B2A 2.4 hydrogen storage alloy powder;

[0054] S4, the Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2A 2.4 The hydrogen storage alloy powder was put into a ball mill at a mass ratio of 1:99 and a ball-to-material ratio of 35:1. High-purity argon gas was introduced into the ball mill and the ball mill was placed in a high-energy ball mill. The effective milling time of the ball milling process was set to 15 minutes to obtain Co-doped CeO2 / Nd-Fe-B composite electrode material.

[0055] Example 2

[0056] S1, dissolving 1 g of cerium nitrate hexahydrate in 30 ml of ethylene glycol to obtain a first mixed solution, dissolving 0.2 g of cobalt nitrate hexahydrate in 0.92 ml of deionized water to obtain a second mixed solution, and mixing the first mixed solution and the second mixed solution with stirring for 5 minutes to obtain a third mixed solution;

[0057] S2. Add 1 ml of glacial acetic acid to 1 ml of deionized water and stir to obtain a fourth mixed solution. Mix the third mixed solution and the fourth mixed solution and stir for 30 minutes, then transfer them to a polytetrafluoroethylene-lined autoclave, heat at 180°C for 3 hours, and then centrifuge. Wash three times with deionized water and ethanol, and dry at 60°C. The dried sample is calcined 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 the order of melting point from low to high in the molar ratio of 10:8:4:60:2:2.4, and arc melted in a copper crucible protected by circulating water under an argon atmosphere. The alloy is turned over and melted four times. The melted alloy is naturally cooled and taken out, and is mechanically crushed and ground, and sieved with a 200-mesh sieve to obtain Nd 10 Pr8Fe4Ni 60 B2A 2.4 hydrogen storage alloy powder;

[0059] S4, the Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2A 2.4 The hydrogen storage alloy powder was put into a ball mill 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 and the ball mill was placed in a high-energy ball mill. The effective milling time of the ball milling process was set to 15 minutes to obtain Co-doped CeO2 / Nd-Fe-B composite electrode material.

[0060] Example 3

[0061] S1, dissolving 1 g of cerium nitrate hexahydrate in 30 ml of ethylene glycol to obtain a first mixed solution, dissolving 0.4 g of cobalt nitrate hexahydrate in 0.92 ml of deionized water to obtain a second mixed solution, and mixing the first mixed solution and the second mixed solution with stirring for 5 minutes to obtain a third mixed solution;

[0062] S2. Add 1 ml of glacial acetic acid to 1 ml of deionized water and stir to obtain a fourth mixed solution. Mix the third mixed solution and the fourth mixed solution and stir for 30 minutes, then transfer them to a polytetrafluoroethylene-lined autoclave, heat at 180°C for 3 hours, and then centrifuge. Wash three times with deionized water and ethanol, and dry at 60°C. The dried sample is calcined 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 the order of melting point from low to high in the molar ratio of 10:8:4:60:2:2.4, and arc melted in a copper crucible protected by circulating water under an argon atmosphere. The alloy is turned over and melted four times. The melted alloy is naturally cooled and taken out, and is mechanically crushed and ground, and sieved with a 200-mesh sieve to obtain Nd 10 Pr8Fe4Ni 60 B2A 2.4 hydrogen storage alloy powder;

[0064] S4, the Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2A 2.4 The hydrogen storage alloy powder was put into a ball mill 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 and the ball mill was placed in a high-energy ball mill. The effective milling time of the ball milling process was set to 15 minutes to obtain a Co-doped CeO2 / Nd-Fe-B composite electrode material.

[0065] Test 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 disc-shaped alloy electrode with a diameter of 1 cm and a thickness of 0.1 to 0.15 cm. This alloy electrode was welded to a conductive nickel wire using a spot welder to form the battery's negative electrode. The positive electrode used a sintered nickelous hydroxide (Ni(OH)2 / NiOOH) electrode sheet, and the electrolyte was a 6 mol / L KOH solution.

[0067] Test 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 disc-shaped alloy electrode with a diameter of 1 cm and a thickness of 0.1 to 0.15 cm. The alloy electrode was welded to a conductive nickel wire using a spot welder to form the battery's negative electrode. The positive electrode used a sintered nickelous hydroxide (Ni(OH)2 / NiOOH) electrode sheet, and the electrolyte was a 6 mol / L KOH solution.

[0069] Test 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 disc-shaped alloy electrode with a diameter of 1 cm and a thickness of 0.1 to 0.15 cm. This alloy electrode was welded to a conductive nickel wire using a spot welder to form the battery's negative electrode. The positive electrode used a sintered nickelous 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 B2A 2.4 Hydrogen storage alloy powder, used as a base alloy, was cold-pressed with carbonyl nickel powder to form a disc-shaped electrode with a diameter of 1 cm and a thickness of 0.1 to 0.15 cm. This disc was then welded to a conductive nickel wire using a spot welder to form the battery's negative electrode. The positive electrode used a sintered nickelous hydroxide (Ni(OH)2 / NiOOH) electrode sheet, and the electrolyte was a 6 mol / L KOH solution.

[0073] Effect detection:

[0074] 1. The batteries assembled in Test Examples 1-3 and the comparative example were subjected to electrochemical performance testing, including attenuation performance, maximum discharge capacity, and rate performance. The maximum discharge capacity and activation performance were tested at a charge and discharge current density of 60 mA / g. For high-rate performance, the battery was first activated at a charge and discharge current density of 60 mA / g. The battery was then charged at a charge current density of 60 mA / g and discharged at discharge current densities of 120 mA / g, 180 mA / g, and finally 600 mA / g. The rate discharge performance was then 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 benchmark alloy;

[0077] from Figure 2It can be seen that the addition of an appropriate amount of Co-CeO2 improves the high-rate discharge performance of the composite alloy. The high-rate discharge performance of hydrogen storage alloys with 1wt% and 2wt% Co-CeO2 additions is superior to that of the baseline alloy. However, when the addition reaches 3wt%, the rate performance of the composite material is significantly inferior to that of the baseline alloy at discharge current densities greater than 240mA / g. The high catalytic activity and moderate conductivity of Co-CeO2 accelerate charge transfer and hydrogen transport within the alloy, allowing hydrogen atoms to diffuse more rapidly from the alloy surface into the interior. However, excessive Co-CeO2 addition makes the alloy more susceptible to pulverization, which is detrimental to improving the high-rate discharge performance of the alloy electrode.

[0078] 2. XRD test was performed on the alloy electrodes of Experimental Examples 1-3 and the reference samples in the comparative example.

[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. Among them, the Nd2Ni7 phase and the NdNi5 phase are phase structures that can play a role in hydrogen storage. It can be seen that the addition of Co-CeO2 does not change the phase structure of the alloy. When the Co-CeO2 addition amount is 1wt% and 2wt%, the diffraction peak height of the alloy composite material increases significantly, and the crystallinity of the alloy increases, which can also explain the increase in the maximum discharge capacity of the alloy composite material after the addition of graphene. When the addition amount is 3wt%, the diffraction peak height of the alloy composite material decreases significantly. This change trend is consistent with the change law of the above-mentioned cycle performance curve and high-rate discharge performance curve.

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as 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 method comprises the following preparation steps: dissolving cerium nitrate hexahydrate in ethylene glycol to obtain a first mixed solution, dissolving cobalt nitrate hexahydrate in water to obtain a second mixed solution, and stirring the first mixed solution and the second mixed solution to obtain a third mixed solution; adding glacial acetic acid to water and stirring to obtain a fourth mixed solution, adding the fourth mixed solution to the third mixed solution, performing a second stirring, heating, and then centrifuging to obtain a first mixture, and pretreating the first mixture 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, and naturally cooled after the smelting to obtain Nd 10 Pr8Fe4Ni 60 B2A 2.4 Hydrogen storage alloy, the Nd 10 Pr8Fe4Ni 60 B2A 2.4 The hydrogen storage alloy was crushed, ground and sieved to obtain Nd 10 Pr8Fe4Ni 60 B2A 2.4 hydrogen storage alloy powder; The Co-CeO2 powder and Nd 10 Pr8Fe4Ni 60 B2A 2.4 The hydrogen storage alloy powder is mixed and ground to obtain the Co-doped CeO2 / Nd-Fe-B composite electrode material.

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

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

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

5. The method for preparing a Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 4, characterized in that: The smelting is specifically performed as follows: arc melting is performed in an argon atmosphere, and the number of melting times is four times.

6. The method for preparing a 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 B2A 2.4 The mass ratio of the hydrogen storage alloy powder is (1-3): (97-99).

7. The method for preparing a Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 6, characterized in that: The mixed grinding was performed by 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 a Co-doped CeO2 / Nd-Fe-B composite electrode material according to claim 7, characterized in that: The volume ratio of the glacial acetic acid to water is 1:

1.

9. The method for preparing a 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 according to any one of claims 1 to 9.

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