Three-dimensional porous metal electrode and preparation method thereof, zinc-iron flow battery and electric device

Abstract

The invention provides a three-dimensional porous metal electrode and a preparation method thereof, a zinc-iron flow battery and an electric device. The preparation method comprises the following steps that a three-dimensional printing model is constructed, and the three-dimensional printing model is provided with holes; the three-dimensional printing model is printed and formed in the protective atmosphere through 3D printing, and a printing blank is obtained; a printing material for 3D printing comprises inert metal powder; the printing blank is subjected to annealing treatment at the temperature of 400-900 DEG C, and an intermediate blank is obtained; and carrying out reduction treatment on the intermediate blank at 500-800 DEG C in a reducing atmosphere to obtain the three-dimensional porous metal electrode. The metal electrode prepared by the method is used as a positive electrode of the zinc-iron flow battery, and the voltage efficiency and coulombic efficiency of the zinc-iron flow battery can be obviously improved.

Description

Technical Field

[0001] The present application relates to the technical field of liquid flow batteries, and in particular to a three-dimensional porous metal electrode and a preparation method thereof, a zinc-iron liquid flow battery and an electrical device. Background Art

[0002] Zinc-iron flow batteries are advanced large-scale energy storage technologies with many inherent advantages. First, they have high energy density and can store large amounts of electrical energy, making them suitable for large-scale energy storage systems. Second, zinc-iron flow batteries are highly safe and are not prone to fire or explosion. Third, zinc and iron are abundant elements in the earth's crust, and the raw material costs are low and environmentally friendly, which helps reduce the production costs and environmental impact of batteries. Fourth, zinc-iron flow batteries have long life and deep discharge capabilities, can maintain high performance after multiple charge and discharge cycles, and can operate stably at different discharge depths.

[0003] However, the positive electrode of the zinc-iron flow battery has the following problems during the charging and discharging process: First, the positive electrode will generate iron oxides during the charging and discharging process. These oxides may adhere to the electrode surface, causing the electrode active surface area to decrease and the number of reactive sites to decrease, thus causing the battery performance to decrease; at the same time, due to the poor conductivity of iron oxides, when attached to the electrode surface, the internal resistance of the battery system and the electrochemical polarization of the electrode surface will increase, causing the battery voltage efficiency to decrease; and due to the irreversible decomposition of the positive electrode active material, the battery capacity and coulomb efficiency gradually decay. In addition, side reactions are prone to occur on the electrode surface during the charging and discharging process, such as the oxidation of water at the positive electrode in the late stage of charging. These side reactions will consume active materials and electrical energy, reducing the coulomb efficiency of the battery.

[0004] Therefore, conventional zinc-iron flow batteries still need to be improved. Summary of the invention

[0005] Based on this, one or more embodiments of the present application provide a three-dimensional porous metal electrode with high voltage efficiency and coulombic efficiency and a preparation method thereof, a zinc-iron liquid flow battery and an electrical device.

[0006] According to a first aspect of an embodiment of the present application, a method for preparing a three-dimensional porous metal electrode is provided, comprising the following steps:

[0007] constructing a three-dimensional printing model, wherein the three-dimensional printing model has holes;

[0008] The three-dimensional printing model is printed and formed by 3D printing in a protective atmosphere to obtain a printed blank; the printing material of the 3D printing includes inert metal powder;

[0009] Annealing the printed blank at 400° C. to 900° C. to obtain an intermediate blank;

[0010] The intermediate blank is subjected to reduction treatment at 500° C. to 800° C. in a reducing atmosphere to obtain a three-dimensional porous metal electrode.

[0011] In some embodiments, the inert metal powder includes one or more of titanium powder, stainless steel powder, gold powder and zirconium powder.

[0012] In some embodiments, the preparation method satisfies at least one of the following characteristics:

[0013] (1) The porosity of the three-dimensional printed model is 30% to 60%;

[0014] (2) The shape of the hole is one or more of square, rectangular, diamond, spherical or irregular;

[0015] (3) The annealing time is 2h~10h;

[0016] (4) The reduction treatment time is 2h~10h;

[0017] (5) The protective atmosphere includes one or more of argon, nitrogen and helium;

[0018] (6) The reducing atmosphere includes hydrogen.

[0019] According to a second aspect of an embodiment of the present application, a three-dimensional porous metal electrode is provided, which is prepared by the above-mentioned preparation method.

[0020] According to a third aspect of an embodiment of the present application, a zinc-iron liquid flow battery is provided, comprising a positive electrode, a negative electrode, a positive electrode electrolyte, a negative electrode electrolyte and a diaphragm, wherein the diaphragm is arranged between the positive electrode and the negative electrode, the positive electrode is immersed in the positive electrode electrolyte, and the negative electrode is immersed in the negative electrode electrolyte;

[0021] The positive electrode includes the above-mentioned three-dimensional porous metal electrode.

[0022] In some embodiments, the zinc-iron flow battery satisfies at least one of the following features:

[0023] (1) The negative electrode material includes one or more of carbon felt, graphite felt, carbon cloth, carbon paper, zinc plate and galvanized plate;

[0024] (2) The diaphragm includes one or more of a proton exchange membrane, a cation exchange membrane, a porous membrane and an anion exchange membrane.

[0025] In some embodiments, the cathode electrolyte is an alkaline solution containing ferrocyanide;

[0026] Optionally, the ferrocyanide includes one or more of potassium ferrocyanide and sodium ferrocyanide;

[0027] Optionally, the alkaline solution includes one or more of a sodium hydroxide solution and a potassium hydroxide solution;

[0028] Optionally, the concentration of ferrocyanide in the positive electrode electrolyte is 0.1 mol / L to 0.85 mol / L;

[0029] Optionally, the concentration of the alkaline solution in the positive electrode electrolyte is 1 mol / L~4 mol / L.

[0030] In some embodiments, the negative electrode electrolyte is an alkaline solution containing zinc ions;

[0031] Optionally, the alkaline solution includes one or more of a sodium hydroxide solution and a potassium hydroxide solution;

[0032] Optionally, the concentration of zinc ions in the negative electrode electrolyte is 0.1 mol / L to 0.4 mol / L;

[0033] Optionally, the concentration of the alkaline solution in the negative electrode electrolyte is 2 mol / L to 6 mol / L.

[0034] In some of the embodiments, it also includes a positive electrode liquid storage tank, a positive electrode circulation pipeline, a positive electrode circulation pump, a negative electrode liquid storage tank, a negative electrode circulation pipeline and a negative electrode circulation pump;

[0035] The positive electrode liquid storage tank is connected to the positive electrode through the positive electrode circulation pipeline, and a positive electrode circulation pump is provided on the positive electrode circulation pipeline; the negative electrode liquid storage tank is connected to the negative electrode through the negative electrode circulation pipeline, and a negative electrode circulation pump is provided on the negative electrode circulation pipeline.

[0036] According to a fourth aspect of an embodiment of the present application, there is provided an electrical device comprising the above-mentioned zinc-iron liquid flow battery.

[0037] Compared with the traditional technology, this application has the following beneficial effects:

[0038] The present application uses an inert metal with good chemical stability as the electrode material, so that the electrode has the performance of chemical corrosion resistance and electrochemical corrosion resistance in the working environment, thereby protecting the integrity of the electrode structure and inhibiting the oxygen evolution side reaction on the electrode surface, thereby reducing unnecessary energy loss and damage to the electrode structure; in this way, the coulomb efficiency of the battery made with the above-mentioned electrode can be effectively improved and its resistance can be reduced. At the same time, controlling the temperature of the annealing treatment and the reduction treatment within a specific range can effectively improve the conductivity of the electrode.

[0039] Furthermore, since the porous metal electrode of the present application has a high specific surface area, it can effectively expand the reaction interface inside the battery, increase the number of reaction active sites, and accommodate more charge transfer and chemical reactions, thereby significantly improving the voltage efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 This is a schematic diagram of the structure of the three-dimensional porous metal electrode prepared in Example 1 of the present application;

[0042] Figure 2 This is a schematic diagram of the structure of the zinc-iron flow battery in Example 1 of the present application. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present application. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present application, etc. can be purchased from the market or can be prepared by existing methods.

[0045] In the present application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0046] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0047] In the present application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1-10, indicating that t is any integer selected from the integer group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0048] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0049] Traditional technology records that a two-dimensional hexagonal sheet of magnesium-aluminum hydrotalcite material is synthesized on the surface of ordinary carbon felt by hydrothermal method to form a nano-scale void structure; this structure can effectively enhance the mass transfer process of active ions on the electrode surface, thereby reducing concentration polarization and improving the voltage efficiency and energy efficiency of the battery. However, this electrode has shortcomings in actual operation. For example, when it is operated for a long time, the carbon felt will decompose in the alkaline solution, and the in-situ grown hydrotalcite material may fall off, resulting in the destruction of the structural morphology.

[0050] Based on this, some embodiments provide a method for preparing a three-dimensional porous metal electrode, including S10 to S40.

[0051] S10: constructing a three-dimensional printing model, wherein the three-dimensional printing model has holes;

[0052] S20: Printing the three-dimensional printing model by 3D printing in a protective atmosphere to obtain a printed blank; the printing material of the 3D printing includes an inert metal powder;

[0053] S30: annealing the printed blank at 400° C. to 900° C. to obtain an intermediate blank;

[0054] S40: performing reduction treatment on the intermediate blank at 500° C. to 800° C. in a reducing atmosphere to obtain a three-dimensional porous metal electrode.

[0055] In some of the embodiments, one or more of the following software are used to construct the 3D printing model in S10: Solidworks and Materialise Magics.

[0056] In some embodiments, the inert metal powder in S20 includes one or more of titanium powder, stainless steel powder, gold powder and zirconium powder.

[0057] Inert metals have good chemical stability and can effectively prevent chemical and electrochemical corrosion in the working environment of the battery, thereby protecting the integrity of the electrode structure, inhibiting possible oxygen evolution side reactions on the electrode surface, and avoiding unnecessary energy loss and damage to the electrode structure.

[0058] Compared with traditional carbon materials and resin materials, the electrodes made of inert metal powder in this application exhibit better conductivity, making the transfer of charge inside the battery more efficient, thereby greatly reducing the internal resistance of the battery, reducing the energy loss caused by poor charge transfer, and thus improving the voltage efficiency of the battery.

[0059] In some of these embodiments, the porosity of the 3D printed model is 30% to 60%.

[0060] As an example, the porosity of the 3D printed model can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, or any value within the range formed by any two of the above point values.

[0061] Furthermore, the porosity of the 3D printed model is 50%~60%.

[0062] It can be understood that the porosity of the three-dimensional porous metal electrode is basically consistent with the porosity of the three-dimensional printed model. By reasonably designing its porosity when constructing the model, the porosity of the three-dimensional porous metal electrode can be within the above range.

[0063] By increasing the porosity of the three-dimensional porous metal electrode, the specific surface area of ​​the electrode can be increased, thereby expanding the reaction interface inside the battery, increasing the number of reaction active sites, accommodating more charge transfer and chemical reactions, and significantly improving the reaction rate and kinetic performance of the battery.

[0064] In some embodiments, the shape of the holes of the three-dimensional printed model is one or more of a square, a rectangle, a diamond, a sphere or an irregular shape.

[0065] In some embodiments, the protective atmosphere in S20 includes one or more of argon, nitrogen and helium.

[0066] Furthermore, the protective atmosphere is selected from argon.

[0067] As an example, the temperature of the annealing treatment in S30 may be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, ℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, or any value within the range formed by any two of the above point values.

[0068] Furthermore, the temperature of the annealing treatment is 700°C to 800°C.

[0069] In some embodiments, the annealing treatment time in S30 is 2 hours to 10 hours.

[0070] As an example, the annealing time can be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, or any value within the range formed by any two of the above point values.

[0071] It is understandable that annealing at the above-mentioned specific temperature can effectively release the stress in the printed blank, thereby alleviating damage such as structural deformation of the electrode, allowing the electrode to maintain a stable structure during multiple charge and discharge cycles, and ensuring stable battery performance. Too high an annealing temperature may damage the internal structure of the material and lead to a decrease in mechanical properties, such as reduced strength and poor toughness; at the same time, too high an annealing temperature may cause excessive grain growth, thereby changing the microstructure of the material. Conversely, if the annealing temperature is too low, it may not be possible to effectively eliminate internal stress or improve material properties, and the expected effect may not be achieved.

[0072] As an example, the temperature of the reduction treatment in S40 can be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, or any value within the range formed by any two of the above point values.

[0073] Furthermore, the temperature of the reduction treatment is 500°C to 600°C.

[0074] In some embodiments, the reduction treatment time in S40 is 2 h to 10 h.

[0075] As an example, the time for the restoration process can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or any value within the range formed by any two of the above point values.

[0076] In some embodiments, the reducing atmosphere in S40 includes one or more of hydrogen gases.

[0077] Furthermore, the reducing atmosphere is selected from hydrogen.

[0078] It can be understood that reduction in a reducing atmosphere can effectively reduce the oxides on the surface of the blank.

[0079] In some embodiments, the preparation method further includes S50.

[0080] S50: polishing the surface of the three-dimensional porous metal electrode.

[0081] It is understandable that polishing the electrode surface with polishing powder can reduce the probability of puncturing the diaphragm when assembling the battery.

[0082] Some embodiments of the present application also provide a three-dimensional porous metal electrode, which is prepared using the above-mentioned preparation method.

[0083] Some embodiments of the present application further provide a zinc-iron liquid flow battery, which includes a positive electrode, a negative electrode, a positive electrode electrolyte, a negative electrode electrolyte and a diaphragm, wherein the diaphragm is disposed between the positive electrode and the negative electrode, the positive electrode is immersed in the positive electrode electrolyte, and the negative electrode is immersed in the negative electrode electrolyte;

[0084] The positive electrode includes the three-dimensional porous metal electrode described above.

[0085] In some embodiments, the material of the negative electrode includes one or more of carbon felt, graphite felt, carbon cloth, carbon paper, zinc plate and galvanized plate.

[0086] In some embodiments, the membrane includes one or more of a proton exchange membrane, a cation exchange membrane, a porous membrane, and an anion exchange membrane.

[0087] In some embodiments, the positive electrode electrolyte is an alkaline solution containing ferrocyanide.

[0088] Further, the concentration of ferricyanide in the positive electrolyte is 0.1 mol / L to 0.85 mol / L. As an example, the concentration of ferricyanide can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, or any value within the range formed by any two of the above point values.

[0089] In some examples, the ferrocyanide includes one or more of potassium ferrocyanide and sodium ferrocyanide.

[0090] Further, the concentration of the alkaline solution in the positive electrode electrolyte is 1 mol / L to 4 mol / L. As an example, the concentration of the alkaline solution can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, or any value within the range formed by any two of the above point values.

[0091] In some examples, the alkaline solution in the positive electrode electrolyte includes one or more of a sodium hydroxide solution and a potassium hydroxide solution.

[0092] In some embodiments, the negative electrode electrolyte is an alkaline solution containing zinc ions.

[0093] Further, the concentration of zinc ions in the negative electrode electrolyte is 0.1 mol / L to 0.4 mol / L. As an example, the concentration of zinc ions can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, or any value within the range formed by any two of the above point values.

[0094] In some examples, the zinc ions in the negative electrolyte are present in the form of zinc oxide.

[0095] Further, the concentration of the alkaline solution in the negative electrode electrolyte is 2 mol / L to 6 mol / L. As an example, the concentration of the alkaline solution can be 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, or any value within the range formed by any two of the above point values.

[0096] In some examples, the alkaline solution in the negative electrode electrolyte includes one or more of a sodium hydroxide solution and a potassium hydroxide solution.

[0097] In some of the embodiments, the zinc-iron liquid flow battery further comprises a positive electrode liquid storage tank, a positive electrode circulation pipeline, a positive electrode circulation pump, a negative electrode liquid storage tank, a negative electrode circulation pipeline and a negative electrode circulation pump;

[0098] The positive electrode liquid storage tank is connected to the positive electrode through a positive electrode circulation pipeline, and a positive electrode circulation pump is provided on the positive electrode circulation pipeline; the negative electrode liquid storage tank is connected to the negative electrode through a negative electrode circulation pipeline, and a negative electrode circulation pump is provided on the negative electrode circulation pipeline.

[0099] The zinc-iron liquid flow battery of the present application uses the three-dimensional porous metal electrode prepared by the above-mentioned specific method as the positive electrode, and the coulombic efficiency and voltage efficiency of the battery are significantly improved during the cycle process.

[0100] Some embodiments of the present application also provide an electrical device, including the above-mentioned zinc-iron liquid flow battery.

[0101] The present application will be further described below in conjunction with specific examples and comparative examples, but they should not be construed as limiting the scope of protection of the present application. The raw materials involved in the following specific examples, unless otherwise specified, can all be sourced from commercial sources, the instruments used, unless otherwise specified, can all be sourced from commercial sources, and the processes involved, unless otherwise specified, are all conventionally selected by those skilled in the art.

[0102] Example 1

[0103] (1) A three-dimensional printed model with multiple hole structures was constructed using Solidworks software. The holes were spherical. The printed model was a cube with a cross-sectional geometric area of ​​50 mm × 50 mm, a thickness of 3 mm, and a porosity of 53%.

[0104] (2) The designed printing model data is imported into the 3D printer, titanium powder is used as the printing material, and 3D printing is performed in an argon atmosphere to obtain a printed blank.

[0105] (3) The printed blank is subjected to high-temperature annealing treatment at 800°C for 3 h to remove the substrate and obtain an intermediate blank.

[0106] (4) The intermediate blank is reduced in a hydrogen atmosphere at 600°C for 2 h, and then the surface is polished with polishing powder to obtain a structure such as Figure 1 The three-dimensional porous titanium electrode shown.

[0107] (5) The porous titanium electrode is used as an electrode, the negative electrode is a porous graphite felt with a thickness of 3 mm (porosity of 45%), the separator is a Nafion 212 proton exchange membrane, the negative electrode liquid includes 0.2 M ZnO and 3 M NaOH solution, and the positive electrode electrolyte includes 0.4 M potassium ferrocyanide and 3 M NaOH solution, and the following is assembled: Figure 2 The zinc-iron flow battery shown. When the battery is running, a pump pumps the electrolyte from the storage tank into the battery for circulation.

[0108] Example 2

[0109] The method is basically the same as Example 1, except that the temperature of the annealing treatment in step (3) is different. Specifically, the annealing temperature in Example 2 is 900° C. The remaining steps and parameters are basically the same as Example 1.

[0110] Example 3

[0111] The method is basically the same as Example 1, except that the temperature of the reduction treatment in step (4) is different. Specifically, the reduction temperature in Example 3 is 800° C. The remaining steps and parameters are basically the same as those in Example 1.

[0112] Example 4

[0113] The method is basically the same as Example 1, except that the printing material in step (2) is different. Specifically, the printing material in Example 4 is stainless steel powder. The remaining steps and parameters are basically the same as Example 1.

[0114] Example 5

[0115] The method is basically the same as Example 1, except that the printing material in step (2) is different. Specifically, the printing material in Example 5 is gold powder. The remaining steps and parameters are basically the same as Example 1.

[0116] Example 6

[0117] The method is basically the same as Example 1, except that the printing material in step (2) is different. Specifically, the printing material in Example 6 is zirconium powder. The remaining steps and parameters are basically the same as Example 1.

[0118] Example 7

[0119] It is basically the same as Example 1, except that the porosity of the printed model and the three-dimensional porous titanium electrode finally prepared is different. Specifically, the porosity of the printed model in Example 7 is 30%.

[0120] Example 8

[0121] It is basically the same as Example 1, except that the porosity of the printed model and the three-dimensional porous titanium electrode finally prepared is different. Specifically, the porosity of the printed model in Example 8 is 26%.

[0122] Comparative Example 1

[0123] It is basically the same as Example 1, except that the positive electrode of the zinc-iron liquid flow battery is different.

[0124] A flat titanium metal plate with a cross-sectional geometric area of ​​50mm×50mm and a thickness of 3mm was used as the positive electrode, a porous graphite felt with a thickness of 3mm was used as the negative electrode, the diaphragm was a Nafion 212 proton exchange membrane, the positive electrode liquid included 0.2M ZnO and 3M NaOH solution, and the negative electrode electrolyte included 0.4M potassium ferrocyanide and 3M NaOH solution, and a zinc-iron liquid flow battery was assembled.

[0125] Comparative Example 2

[0126] The method is basically the same as Example 1, except that the temperature of the annealing treatment in step (3) is different. Specifically, the annealing temperature in Comparative Example 2 is 1000° C. The remaining steps and parameters are basically the same as those in Example 1.

[0127] Comparative Example 3

[0128] The method is basically the same as Example 1, except that the temperature of the reduction treatment in step (4) is different. Specifically, the annealing temperature in Comparative Example 3 is 1000° C. The remaining steps and parameters are basically the same as Example 1.

[0129] Comparative Example 4

[0130] The method is basically the same as Example 1, except that the temperature of the reduction treatment in step (4) is different. Specifically, the annealing temperature in Comparative Example 4 is 400° C. The remaining steps and parameters are basically the same as Example 1.

[0131] Comparative Example 5

[0132] The method is basically the same as Example 1, except that the printing material in step (2) is different. Specifically, the printing material in Comparative Example 5 is a photosensitive resin. The remaining steps and parameters are basically the same as Example 1.

[0133] Some step parameters in the above embodiments and comparative examples are shown in the following table.

[0134] Table 1

[0135]

[0136] Performance Testing

[0137] The battery was tested using a charge and discharge instrument. The test conditions were: continuous charge and discharge tests were performed on the battery at a constant power of 50W. The cycle steps were: 50W constant power charging to a cut-off voltage of 2.1V, then constant power discharging to a cut-off voltage of 1.2V, and continuous cycling for 20 cycles. The coulombic efficiency, voltage efficiency, and energy efficiency of the battery were tested to characterize the cyclic charge and discharge performance of the battery, and the average coulombic efficiency, voltage efficiency, and energy efficiency of 20 cycles were calculated. The test results are shown in Table 2.

[0138] Voltage efficiency = discharge voltage of a single cycle / charge voltage of a single cycle × 100%

[0139] Coulomb efficiency = discharge capacity of a single cycle / charge capacity of a single cycle × 100%

[0140] Energy efficiency = discharge energy of a single cycle / charge energy of a single cycle × 100%

[0141] Table 2 Battery performance test results

[0142]

[0143] It can be seen from the above table that compared with the comparative example, the voltage efficiency of the zinc-iron liquid flow battery prepared in Examples 1 to 8 is significantly higher, indicating that the metal electrode with a three-dimensional porous structure of the present application can effectively reduce the electrochemical polarization of the positive electrode and the concentration polarization in the later stage of the reaction; at the same time, the coulombic efficiency of the battery prepared in Example 1 is also improved in 20 cycles, indicating that the inert electrode can effectively inhibit the occurrence of the oxygen evolution side reaction.

[0144] Compared with Example 1, after the annealing temperature in Example 2 was increased to 900°C, the coulombic efficiency, voltage efficiency and energy efficiency were slightly reduced; after the annealing temperature in Comparative Example 2 was increased to 1000°C, the coulombic efficiency, voltage efficiency and energy efficiency were significantly reduced; indicating that limiting the annealing temperature to around 800°C can further improve the comprehensive performance of the electrode material.

[0145] Compared with Example 1, the difference between Example 3, Comparative Example 3 and Comparative Example 4 is that the reduction temperature is different. When the reduction temperature is controlled at about 600° C., the comprehensive performance of the electrode material can be further improved.

[0146] It can be seen from Examples 1 and 4 to 6 that, compared with stainless steel powder, gold powder and zirconium powder, selecting titanium powder as an inert metal for printing is conducive to preparing an electrode material with better comprehensive performance.

[0147] It can be seen from Examples 1 and 7 to 8 that a porosity of the positive electrode material of 50% to 60% is conducive to preparing an electrode material with better comprehensive performance.

[0148] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0149] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for preparing a three-dimensional porous metal electrode, characterized in that: The steps include: constructing a three-dimensional printing model, wherein the three-dimensional printing model has holes; The three-dimensional printing model is printed and formed by 3D printing in a protective atmosphere to obtain a printed blank; the printing material of the 3D printing includes inert metal powder; Annealing the printed blank at 400° C. to 900° C. to obtain an intermediate blank; The intermediate blank is subjected to reduction treatment at 500° C. to 800° C. in a reducing atmosphere to obtain a three-dimensional porous metal electrode.

2. The method for preparing a three-dimensional porous metal electrode according to claim 1, characterized in that: The inert metal powder includes one or more of titanium powder, stainless steel powder, gold powder and zirconium powder.

3. The method for preparing a three-dimensional porous metal electrode according to claim 1, characterized in that: The preparation method meets at least one of the following characteristics: (1) The porosity of the three-dimensional printed model is 30% to 60%; (2) The shape of the hole is one or more of square, rectangular, diamond, spherical or irregular; (3) The annealing time is 2h~10h; (4) The reduction treatment time is 2h~10h; (5) The protective atmosphere includes one or more of argon, nitrogen and helium; (6) The reducing atmosphere includes hydrogen.

4. A three-dimensional porous metal electrode, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 3.

5. A zinc-iron liquid flow battery, characterized in that: It includes a positive electrode, a negative electrode, a positive electrode electrolyte, a negative electrode electrolyte and a separator, wherein the separator is arranged between the positive electrode and the negative electrode, the positive electrode is immersed in the positive electrode electrolyte, and the negative electrode is immersed in the negative electrode electrolyte; The positive electrode comprises the three-dimensional porous metal electrode according to claim 4.

6. The zinc-iron flow battery according to claim 5, characterized in that: The zinc-iron flow battery meets at least one of the following characteristics: (1) The negative electrode material includes one or more of carbon felt, graphite felt, carbon cloth, carbon paper, zinc plate and galvanized plate; (2) The diaphragm includes one or more of a proton exchange membrane, a cation exchange membrane, a porous membrane and an anion exchange membrane.

7. The zinc-iron flow battery according to any one of claims 5 to 6, characterized in that: The positive electrode electrolyte is an alkaline solution containing ferrocyanide; Optionally, the ferrocyanide includes one or more of potassium ferrocyanide and sodium ferrocyanide; Optionally, the alkaline solution includes one or more of a sodium hydroxide solution and a potassium hydroxide solution; Optionally, the concentration of ferrocyanide in the positive electrode electrolyte is 0.1 mol / L to 0.85 mol / L; Optionally, the concentration of the alkaline solution in the positive electrode electrolyte is 1 mol / L~4 mol / L.

8. The zinc-iron flow battery according to any one of claims 5 to 6, characterized in that: The negative electrode electrolyte is an alkaline solution containing zinc ions; Optionally, the alkaline solution includes one or more of a sodium hydroxide solution and a potassium hydroxide solution; Optionally, the concentration of zinc ions in the negative electrode electrolyte is 0.1 mol / L to 0.4 mol / L; Optionally, the concentration of the alkaline solution in the negative electrode electrolyte is 2 mol / L to 6 mol / L.

9. The zinc-iron flow battery according to any one of claims 5 to 6, characterized in that: It also includes a positive electrode liquid storage tank, a positive electrode circulation pipeline, a positive electrode circulation pump, a negative electrode liquid storage tank, a negative electrode circulation pipeline and a negative electrode circulation pump; The positive electrode liquid storage tank is connected to the positive electrode through the positive electrode circulation pipeline, and a positive electrode circulation pump is provided on the positive electrode circulation pipeline; the negative electrode liquid storage tank is connected to the negative electrode through the negative electrode circulation pipeline, and a negative electrode circulation pump is provided on the negative electrode circulation pipeline.

10. An electrical device, characterized in that: Including the zinc-iron liquid flow battery as described in any one of claims 5 to 9.

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