Composite electrode material for zinc-bromine flow battery as well as preparation method and application of composite electrode material

Abstract

The invention discloses a composite electrode material for a zinc-bromine flow battery and a preparation method and application thereof, and the preparation method comprises the following steps: S1, uniformly stirring a copper salt, a zinc salt, a sodium salt and distilled water at room temperature, aging in air, and then filtering, washing and drying to obtain a zinc-copper composite salt; s2, adding a polymer into an organic solvent under a stirring condition, and stirring under a water bath condition to obtain a spinning solution; then adding zinc-copper composite salt, stirring and then carrying out ultrasonic dispersion to obtain a composite spinning solution; s3, preparing the composite spinning solution into a precursor nanofiber material by utilizing high-voltage electrostatic spinning; and S4, carrying out pre-oxidation and carbonization treatment on the precursor nanofiber material in an atmosphere furnace, and cleaning and drying the carbonized material to obtain the composite electrode material for the zinc-bromine flow battery. According to the invention, the problems of low surface activity of bromine electrode reaction on an electrode material, unstable electro-catalytic performance, bromine permeation and the like in the zinc-bromine flow battery can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to a composite electrode material for zinc-bromine liquid flow battery, and a preparation method and application thereof. Background Art

[0002] The shortage and pollution of fossil energy have led to increasing attention to renewable energy. Energy storage technology has become a key technology for the utilization of renewable energy because it can solve the unreliable and discontinuous characteristics of renewable energy. Among the many energy storage technologies, flow batteries are considered to be one of the most promising large-scale energy storage technologies due to their flexible design, high efficiency, long cycle life, and environmental friendliness.

[0003] Zinc-bromine flow batteries have attracted widespread attention due to their advantages such as high voltage, high energy density and low cost. However, the slow redox rate of bromine in the positive electrode of zinc-bromine flow batteries and the diffusion of bromine are key issues that restrict the practical application and industrialization of zinc-bromine flow batteries. The bromine element produced when the battery is charged cannot be completely converted into bromide ions during the discharge stage. On the one hand, it causes the battery coulomb efficiency of subsequent cycles to decrease, and on the other hand, it is easy to cause the concentration of bromine in the positive electrode to be too high, which penetrates into the environment and causes pollution. At present, the electrode materials used in zinc-bromine flow batteries are mainly carbon graphite felt or carbon felt, which has the advantages of low resistivity, large specific surface area, chemical and electrochemical stability; however, the electrochemical activity of the zinc-bromine flow battery electrode reaction on its surface is low, so it is necessary to activate the graphite felt or carbon felt to improve its electrochemical activity and thus improve the battery performance. Nowadays, there are many modification methods for carbon felt or graphite felt electrode materials, including liquid or gas phase chemical treatment, electrochemical treatment, etc., but these methods are very limited in improving the electrochemical activity of carbon fibers, and cannot effectively inhibit bromine penetration.

[0004] Chinese Patent Application No. 201711111243.2 supports carbon-coated titanium disulfide catalyst on carbon felt, thereby inhibiting bromine diffusion to a certain extent, but its tantalum activity is not high, and its cost is high, and its application is difficult; Chinese Patent Application No. 202011384269.6 develops a nitrogen-doped porous carbon felt material for use in zinc-based flow batteries. Its porous structure improves the pore volume, specific surface area and hydrophilicity of the carbon felt, which can enhance the electrolyte wettability and adsorption capacity of zinc atoms, and provide more zinc deposition sites, but its ability to inhibit bromine diffusion is general. The electrode materials prepared by the above methods still have shortcomings in cost, application and electrochemical performance, and need to be further optimized. Summary of the invention

[0005] Aiming at the defects existing in the prior art, the object of the present invention is to provide a composite electrode material for zinc-bromine flow batteries, its preparation method and application, which can solve the problems of low surface activity of bromine electrode reaction in zinc-bromine flow batteries, unstable electrocatalytic performance of electrode materials, bromine penetration, etc. existing in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a preparation method of a composite electrode material for zinc-bromine flow batteries, comprising the following steps:

[0008] S1, Stir copper salt, zinc salt, sodium salt and distilled water evenly at room temperature to form a mixed solution, and after aging treatment in air, filter, wash and dry to obtain zinc-copper double salt;

[0009] S2, Add the polymer to the organic solvent under stirring conditions, and stir under water bath conditions to obtain a spinning solution; then add zinc-copper double salt, stir and perform ultrasonic dispersion to obtain a composite spinning solution;

[0010] S3, Use high-voltage electrospinning to make the composite spinning solution into a precursor nanofiber material;

[0011] S4, Perform pre-oxidation and carbonization treatment on the precursor nanofiber material in an atmosphere furnace, and then wash and dry the carbonized material to obtain a composite electrode material for zinc-bromine flow batteries.

[0012] Preferably, in the step S1:

[0013] The copper salt is selected from one or more of copper sulfate, copper nitrate, and copper acetate;

[0014] The zinc salt is selected from one or more of zinc acetate, zinc sulfate, and zinc nitrate;

[0015] The sodium salt is selected from one or two of sodium diethyldithiocarbamate and sodium dimethyldithiocarbamate.

[0016] Preferably, in the step S1:

[0017] In the mixed solution, the total amount of substance of Cu 2+ and Zn 2+ is 0.01 - 0.05 mol, the amount of substance of Na + is 0.02 - 0.1 mol, and the volume of distilled water is 50 - 250 mL;

[0018] The stirring time is 5 - 12 h, and the aging time is 6 - 24 h;

[0019] The drying temperature is 60 to 100 °C, and the drying time is 5 to 24 h.

[0020] Preferably, in step S2:

[0021] The polymer is selected from one or more of polyacrylonitrile, polyimide, polyvinylpyrrolidone, and polymethyl methacrylate;

[0022] The organic solvent is selected from one or more of ethanol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and acetone.

[0023] Preferably, in step S2:

[0024] The weight ratio of the polymer, zinc-copper composite salt to the organic solvent is 1: 0.5 to 7: 6 to 20; and / or

[0025] The temperature of the water bath is 40 to 100 °C, the total stirring time is 4 to 28 h, and the ultrasonic dispersion time is 2 to 6 h.

[0026] Preferably, the weight ratio of the polymer, zinc-copper composite salt to the organic solvent is 1: 0.5 to 5: 8 to 15; and / or

[0027] The temperature of the water bath is 60 to 80 °C.

[0028] Preferably, in step S3, the process parameters of the high-voltage electrospinning are: the needle aperture is 0.3 to 2.0 mm, the syringe capacity is 5 to 500 mL, the spinning solution flow rate is 0.2 to 5 mm / min, the rotation speed of the roller is 100 to 1000 rpm, the voltage between the needle and the roller is 10 to 30 kV, the distance between the needle and the nanofiber membrane collecting plate on the roller is 10 to 30 cm, the spinning temperature is 25 to 45 °C, and the spinning humidity is 20 to 70% RH.

[0029] Preferably, in step S3:

[0030] The high-voltage electrospinning adopts one of single needle, multi-needle, and needleless; and / or

[0031] The nanofiber membrane collecting plate on the roller is made of one or more of carbon paper, graphite paper, carbon cloth, aluminum foil, tin foil, and alumina foil.

[0032] Preferably, in step S4:

[0033] The pre-oxidation treatment is carried out in an air atmosphere, the pre-oxidation temperature is 200 to 300 °C, the heat preservation time is 1 to 6 h, and the atmosphere is air; and / or

[0034] The carbonization treatment is carried out under a protective atmosphere, the carbonization temperature is 600-1800° C., and the insulation time is 1-12 hours; the protective atmosphere is nitrogen or argon; and / or

[0035] The carbonized material is washed and then dried in a vacuum drying oven or a forced air drying oven at a drying temperature of 60 to 100° C. for a drying time of 6 to 48 hours.

[0036] Preferably, the heating rate of the pre-oxidation treatment is 2 to 20° C. / min; the heating rate of the carbonization treatment is 2 to 25° C. / min, and the flow rate of the protective gas is 20 to 100 ml / min.

[0037] The second aspect of the present invention provides a composite electrode material for zinc-bromine flow battery prepared by the method for preparing a composite electrode material for zinc-bromine flow battery as described in the first aspect of the present invention.

[0038] Preferably, the composite electrode material for zinc-bromine flow battery contains a zinc-copper sulfide composite catalyst, which accounts for 1 to 10 wt%; and / or

[0039] The thickness of the composite electrode material for zinc-bromine flow battery is 1 to 3.5 mm; and / or

[0040] The specific surface area of ​​the composite electrode material for zinc-bromine flow battery is 125 to 165 m 2 / g.

[0041] The third aspect of the present invention provides an application of the composite electrode material for zinc-bromine liquid flow battery as described in the second aspect of the present invention in a zinc-bromine liquid flow battery.

[0042] The beneficial effects of the present invention are:

[0043] 1. The present invention starts with the electrode material and uses high-voltage electrospinning technology to spin the zinc-copper sulfide composite catalyst with electrocatalytic activity into the interior of the nano-carbon fiber, which not only improves the electrocatalytic activity of the electrode, but also makes the catalyst well fixed on the electrode matrix, thereby ensuring the stability of the electrode material;

[0044] 2. The composite electrode material for zinc-bromine liquid flow battery prepared by the present invention is suitable for zinc-bromine liquid flow battery. During the redox reaction of the zinc-bromine liquid flow battery, the bromine element produced is completely reacted, which greatly reduces the concentration of bromine in the electrolyte solution during the subsequent circulation process, reduces the penetration pollution of the bromine element, and improves the voltage efficiency and energy efficiency of the zinc-bromine liquid flow battery, thereby improving its working current density, so that the weight, volume and cost of the battery with the same output power are greatly reduced;

[0045] 3. The present invention uses high-voltage electrospinning to prepare a self-supporting composite nanofiber membrane material with certain mechanical properties, which can not only maintain the intrinsic characteristics of the material, but also improve the comprehensive performance of the material through synergistic action with polymer materials;

[0046] 4. The composite electrode material for zinc-bromine flow battery composed of intertwined carbon fibers of the present invention has a three-dimensional skeleton that provides good electronic conductivity while also having the characteristics of a flexible electrode, which also provides convenience for the assembly of zinc-bromine flow batteries and is easy to realize industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Other features, objects, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0048] Figure 1 It is a schematic flow chart of the preparation method of the composite electrode material for zinc-bromine flow battery of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0050] Combined with Figure 1 As shown, a preparation method of a composite electrode material for zinc-bromine flow battery provided by the present invention includes the following steps:

[0051] S1. Stir copper salt, zinc salt, sodium salt and distilled water evenly at room temperature to form a mixed solution. After aging treatment in air, filter, wash and dry to obtain zinc-copper composite salt;

[0052] Specifically, take a certain amount of copper salt, zinc salt and sodium salt respectively, add them to an appropriate amount of distilled water and mix evenly, or mix a certain amount of copper salt, zinc salt and sodium salt together and add them to an appropriate amount of distilled water, stir at room temperature for a certain time, and mix evenly to form a mixed solution. Age the mixed solution in air for a certain time, then filter and wash, and finally dry in an oven to obtain a black powder, that is, zinc-copper composite salt;

[0053] Among the above materials used, the copper salt is selected from one or more of copper sulfate, copper nitrate, and copper acetate; the zinc salt is selected from one or more of zinc acetate, zinc sulfate, and zinc nitrate; the sodium salt is selected from one or two of sodium diethyldithiocarbamate and sodium dimethyldithiocarbamate. In a specific embodiment, in the mixed solution, the total amount of substance of Cu 2+ and Zn 2+ is 0.01 - 0.05 mol, and the amount of Na +The amount of the substance is 0.02 to 0.1 mol, and the volume of distilled water is 50 to 250 mL.

[0054] In the above process, the stirring time is 5 to 12 h, and the aging time is 6 to 24 h; through the above aging, small crystals in the solution can be continuously dissolved, and impurities adsorbed inside the precipitate re-enter the solution, which can improve the purity of the precipitate and finally obtain the target precipitate. When drying, the drying temperature is 60 to 100 °C, and the drying time is 5 to 24 h.

[0055] S2, adding the polymer to the organic solvent under stirring conditions, and obtaining a spinning solution after stirring under a water bath condition; then adding a zinc-copper composite salt, and performing ultrasonic dispersion after stirring to obtain a composite spinning solution;

[0056] Specifically, adding the polymer to the organic solvent under stirring conditions, and obtaining a spinning solution after stirring under the condition that the water bath temperature is 40 to 100 °C; then adding the zinc-copper composite salt prepared in step S1, stirring for a period of time, and then performing ultrasonic dispersion for a period of time to obtain a uniform composite spinning solution. Among them, the polymer is selected from one or more of polyacrylonitrile, polyimide, polyvinylpyrrolidone, and polymethyl methacrylate; the organic solvent is selected from one or more of ethanol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and acetone. The weight ratio of the polymer, the zinc-copper composite salt to the organic solvent is 1:0.5 to 7:6 to 20, and in a preferred embodiment, the weight ratio of the polymer, the zinc-copper composite salt to the organic solvent is 1:0.5 to 5:8 to 15. In the above process, the temperature of the water bath is 40 to 100 °C, the preferred water bath temperature is 60 to 80 °C, the total stirring time is 4 to 28 h (the stirring time during the preparation of the spinning solution is 2 to 4 h, and the stirring time during the preparation of the composite spinning solution is 2 to 24 h), and the ultrasonic dispersion time is 2 to 6 h.

[0057] S3, using high-voltage electrospinning to make the composite spinning solution into a precursor nanofiber material;

[0058] Specifically, the composite spinning solution obtained in step S2 is prepared by high-voltage electrospinning to obtain a precursor nanofiber material with a thickness of 1 to 3.5.

[0059] The process parameters of the above high-voltage electrospinning are as follows: the needle aperture is 0.3 - 2.0 mm, the syringe capacity is 5 - 500 mL, the spinning solution flow rate is 0.2 - 5 mm / min, the rotation speed of the roller is 100 - 1000 r / min, the voltage between the needle and the roller is 10 - 30 kV, the distance between the needle and the nanofiber membrane collecting plate on the roller is 10 - 30 cm, the spinning temperature is 25 - 45 °C, and the spinning humidity is 20 - 70% RH; in a preferred embodiment, the process parameters of the high-voltage electrospinning are: the needle aperture is 0.3 - 1.6 mm, the syringe capacity is 5 - 20 mL, the spinning solution flow rate is 0.3 - 3 mm / min, the rotation speed of the roller is 200 - 500 r / min, the voltage between the needle and the roller is 10 - 25 kV, the distance between the needle and the nanofiber membrane collecting plate on the roller is 10 - 25 cm, and the spinning humidity is 30 - 60% RH.

[0060] The high-voltage electrospinning adopts one of single needle, multi-needle, and needleless. The nanofiber membrane collecting plate on the roller adopts one or several of carbon paper, graphite paper, carbon cloth, aluminum foil, tin foil, and alumina foil; among them, the thickness of the carbon paper and graphite paper can be 30 - 300 μm, the thickness of the carbon cloth can be 100 - 1000 μm, and the thickness of the aluminum foil, tin foil, and alumina foil can be 10 - 100 μm.

[0061] S4. The precursor nanofiber material is subjected to pre-oxidation and carbonization treatment in an atmosphere furnace, and then the carbonized material is washed and dried to obtain the composite electrode material for zinc-bromine flow batteries.

[0062] Specifically, the above-prepared precursor nanofiber material is placed in an atmosphere furnace (such as a tube furnace) for pre-oxidation and carbonization treatment; the pre-oxidation treatment is carried out in an air atmosphere, the pre-oxidation temperature is 200 - 300 °C, and the holding time is 1 - 6 h; the carbonization treatment is carried out in a protective atmosphere, the carbonization temperature is 600 - 1800 °C, and the holding time is 1 - 12 h. The protective atmosphere uses nitrogen or argon; the heating rate of the pre-oxidation treatment is 2 - 20 °C / min (preferably 5 - 10 °C / min), the heating rate of the carbonization treatment is 2 - 25 °C / min (preferably 5 - 10 °C / min), and the gas flow rate of the protective atmosphere is 20 - 100 mL / min. Then the carbonized material is washed with deionized water or ultrasonically cleaned, and then placed in a vacuum drying oven or a blast drying oven for drying. The drying temperature is 60 - 100 °C, and the drying time is 6 - 48 h. After drying, a composite electrode material for zinc-bromine flow batteries with a thickness of 1 - 3.5 mm is obtained.

[0063] The composite electrode material for zinc-bromine flow battery prepared above is a film-like or block-like material with controllable thickness formed by winding nanocarbon fibers containing zinc-copper sulfide composite catalyst, and the proportion of zinc-copper sulfide composite catalyst is 1-10wt%; the thickness of the composite electrode material for zinc-bromine flow battery is 1-3.5mm, and the specific surface area is 125-165m 2 / g.

[0064] The application of the composite electrode material for zinc-bromine liquid flow battery prepared above in zinc-bromine liquid flow battery, when applied to the positive electrode material, has a current density of 80mA / cm 2 Under constant current charge and discharge test conditions, the energy efficiency of the graphite electrode without the catalyst was increased from 75.8% to 76.5% to 80.4% to 84.1%.

[0065] The composite electrode material for zinc-bromine liquid flow battery and the preparation method thereof of the present invention are further introduced below with reference to specific examples.

[0066] Example 1

[0067] The preparation method of the composite electrode material for zinc-bromine flow battery in this embodiment is as follows:

[0068] (1) Preparation of zinc-copper composite salt: Take Cu 2+ With Zn 2+ The total amount of substance is 0.01 mol, Na + The amount of the substance is 0.02 mol, which is added into 100 ml of distilled water and stirred at room temperature for 6 h. After being mixed evenly, a mixed solution is formed. The mixed solution is aged in air for 6 h, then filtered and washed, and finally dried in an oven at 60 ° C for 10 h to obtain a black powder, namely zinc copper sulfate;

[0069] (2) A certain amount of polyacrylonitrile was added to an appropriate amount of dimethylformamide under stirring conditions so that the mass fraction of polyacrylonitrile in the entire solution was 8%, and the spinning solution was obtained by stirring at a water bath temperature of 60°C for 2 hours. The average molecular weight of the polyacrylonitrile was 150,000.

[0070] (3) adding zinc copper sulfate powder to the spinning solution in a mass ratio of 1:1, stirring for 12 hours, and then ultrasonicating for 6 hours to obtain a uniform composite spinning solution.

[0071] (4) Add the composite spinning solution obtained in step (3) into a 10 ml syringe, and use the high-voltage electrospinning technology to obtain a precursor nanofiber material. The thickness of the nanofiber membrane is 0.5 mm. Among them, the electrospinning process parameters are: the needle aperture is 0.3 mm, the distance between the needle and the nanofiber membrane collection plate on the roller is 15 cm, the electrospinning voltage between the needle and the roller is 20 kV, the collection plate is tinfoil with a thickness of 100 μm, the rotation speed of the roller is 200 revolutions per minute, the flow rate of the spinning solution is 0.5 mm / minute, the spinning temperature is 40 °C, and the humidity is 50% RH.

[0072] (5) Place the nanofiber membrane obtained in step (3) into a tubular furnace for pre-oxidation and carbonization treatment. The pre-oxidation temperature is 250 °C, the heating rate is 20 °C / minute, the holding time is 2 hours, and the atmosphere is air; the carbonization temperature is 800 °C, the heating rate is 10 °C / minute, the holding time is 4 hours, the inert protective atmosphere is nitrogen, and the gas flow rate is 60 ml / minute.

[0073] (6) Wash the carbonized material obtained in step (5) with deionized water 3 - 4 times, and then place it in a vacuum drying oven at 100 °C for 24 hours of holding time. After drying, a composite electrode material for zinc-bromine flow battery with a thickness of 0.3 mm is obtained, which is a block composed of nanofibers entangled with a copper zinc sulfide composite catalyst. In this composite electrode material for zinc-bromine flow battery, the copper zinc sulfide composite catalyst accounts for 3.6 wt%.

[0074] The specific surface area of the composite electrode material for zinc-bromine flow battery prepared in this example is 138.3 m 2 / g, which is two orders of magnitude higher than the specific surface area of the carbon felt electrode (3.2 m 2 / g). At the same time, by using electrospinning to spin the electrocatalytically active copper zinc sulfide composite catalyst into the interior of the nanofibers, not only the electrocatalytic activity of the electrode is improved, but also the catalyst is well fixed on the electrode matrix, ensuring the stability of the electrode material.

[0075] The composite electrode material for zinc-bromine flow battery prepared in this example, under the constant current charge-discharge test conditions with a current density of 80 mA / cm 2 , for the zinc-bromine flow battery applying this composite electrode material, its energy efficiency is increased from 75.8% of the graphite electrode without using the composite electrode material to 81.6%.

[0076] Example 2

[0077] The preparation method of the composite electrode material for zinc-bromine flow battery in this example is as follows:

[0078] (1) Prepare a zinc copper composite salt: Take Cu 2+ and Zn2+ The total amount of substance is 0.02 mol, and the amount of substance of Na + is 0.04 mol. They are mixed and added to 50 ml of distilled water, stirred at room temperature for 8 h, and after being evenly mixed, a mixed solution is formed. The mixed solution is aged in air for 12 h, then filtered and washed, and finally dried in an oven at 80 °C for 8 h to obtain a black powder, namely copper zinc sulfate;

[0079] (2) A certain amount of polyacrylonitrile is added to an appropriate amount of dimethylformamide under stirring conditions, so that the mass fraction of polyacrylonitrile in the whole solution is 10%. Stir for 4 hours at a water bath temperature of 40 °C to obtain a spinning solution, and the average molecular weight of polyacrylonitrile is 8000.

[0080] (3) The copper zinc sulfate powder is added to the spinning solution, and the mass ratio of the added copper zinc sulfate powder to polyacrylonitrile in the solution is 1:2. After stirring for 12 h, it is then ultrasonically treated for 6 h to obtain a uniform composite spinning solution.

[0081] (4) The composite spinning solution obtained in step (3) is added to a 20 ml syringe, and a precursor nanofiber material is obtained by using the high-voltage electrospinning technique. The thickness of the nanofiber membrane is 1 mm; among them, the electrospinning process parameters are: the needle aperture is 0.5 mm, the distance between the needle and the nanofiber membrane collection plate on the roller is 15 cm, the electrospinning voltage between the needle and the roller is 25 kV, the collection plate is tinfoil with a thickness of 100 μm, the rotation speed of the roller is 200 revolutions per minute, the flow rate of the spinning solution is 0.5 mm / minute, the electrospinning temperature is 30 °C, and the humidity is 40% RH.

[0082] (5) The precursor nanofiber material obtained in step (3) is placed in a tubular furnace for pre-oxidation and carbonization treatment. The pre-oxidation temperature is 250 °C, the heating rate is 20 °C / minute, the holding time is 2 h, and the atmosphere is air; the carbonization temperature is 800 °C, the heating rate is 10 °C / minute, the holding time is 4 h, the inert protective atmosphere is nitrogen, and the gas flow rate is 60 ml / minute.

[0083] (6) The carbonized material obtained in step (5) is washed 3 - 4 times with deionized water, and then placed in a vacuum drying oven at 100 °C, and the holding time is 24 h. After drying, a composite electrode material for a zinc bromine flow battery with a thickness of 0.3 mm is obtained, which is a block formed by entanglement of nanocarbon fibers modified with a copper zinc sulfide composite catalyst. In this composite electrode material for a zinc bromine flow battery, the copper zinc sulfide composite catalyst accounts for 1.8 wt%.

[0084] The specific surface area of the composite electrode material for a zinc bromine flow battery prepared in this example is 134.6 m 2 / g, and the specific surface area of the carbon felt electrode (3.2 m2 / g) is two orders of magnitude higher. At the same time, electrospinning is used to spin the electrocatalytically active copper zinc sulfide composite catalyst into the interior of the nanofibers, which not only improves the electrocatalytic activity of the electrode, but also fixes the catalyst well on the electrode substrate, ensuring the stability of the electrode material.

[0085] The composite electrode material for zinc bromine flow battery prepared in this example has a current density of 80 mA / cm 2 Under the constant current charge-discharge test conditions, the energy efficiency of the zinc bromine flow battery using this composite electrode material is increased from 76.2% of the graphite electrode without using the composite electrode material to 82.1%.

[0086] Example 3

[0087] The preparation method of the composite electrode material for zinc bromine flow battery in this example is as follows:

[0088] (1) Preparation of copper zinc composite salt: Take Cu 2+ and Zn 2+ with a total amount of substance of 0.04 mol, and the amount of substance of Na + is 0.08 mol. Mix and add them to 150 ml of distilled water, stir at room temperature for 6 h, form a mixed solution after mixing evenly, age the mixed solution in air for 6 h, then filter, wash, and finally dry in an oven at 80 °C for 12 h to obtain black powder, namely copper zinc sulfate.

[0089] (2) Add a certain amount of polyacrylonitrile to an appropriate amount of dimethylformamide under stirring conditions so that the mass fraction of polyacrylonitrile in the whole solution is 12%. Stir at a water bath temperature of 80 °C for 2 hours to obtain a spinning solution, and the average molecular weight of polyacrylonitrile is 150,000.

[0090] (3) Add the copper zinc sulfate powder to the spinning solution, and the mass ratio of the added copper zinc sulfate powder to polyacrylonitrile in the solution is 2:3. After stirring for 6 hours, then ultrasonicate for 5 hours to obtain a uniform composite spinning solution.

[0091] (4) Add the composite spinning solution obtained in step (3) to a 20 ml syringe, and use the high-voltage electrospinning technology to obtain a precursor nanofiber material, and the thickness of the nanofiber membrane is 2 mm; among them, the electrospinning process parameters are: the needle aperture is 0.6 mm, the distance between the needle and the nanofiber membrane collection plate on the roller is 20 cm, the electrospinning voltage between the needle and the roller is 15 kV, the collection plate is a 100-μm-thick tin foil, the rotation speed of the roller is 500 revolutions per minute, the flow rate of the spinning solution is 1.2 mm / minute, the electrospinning temperature is 30 °C, and the humidity is 30% RH.

[0092] (5) Place the nanofiber membrane obtained in step (3) into a tubular furnace for pre-oxidation and carbonization. The pre-oxidation temperature is 280 °C, the heating rate is 5 °C / minute, the holding time is 3 hours, and the atmosphere is air; the carbonization temperature is 800 °C, the heating rate is 20 °C / minute, the holding time is 6 hours, the inert protective atmosphere is nitrogen, and the gas flow rate is 80 ml / minute.

[0093] (6) Wash the carbonized material obtained in step (5) with deionized water 3 - 4 times, and then place it in a vacuum drying oven at 80 °C for 12 hours. After drying, a composite electrode material for zinc-bromine flow batteries with a thickness of 1.5 mm is obtained. It is a block formed by entanglement of nanocarbon fibers modified with copper zinc sulfide composite catalyst. In this composite electrode material for zinc-bromine flow batteries, the copper zinc sulfide composite catalyst accounts for 4.5 wt%.

[0094] The specific surface area of the composite electrode material for zinc-bromine flow batteries prepared in this example is 162.2 m 2 / g, which is 2 orders of magnitude higher than the specific surface area of the carbon felt electrode (3.2 m 2 / g). At the same time, by electrospinning, the electrocatalytically active copper zinc sulfide composite catalyst is spun into the interior of the nanocarbon fibers, which not only improves the electrocatalytic activity of the electrode, but also fixes the catalyst well on the electrode matrix, ensuring the stability of the electrode material.

[0095] Under the constant current charge-discharge test conditions with a current density of 80 mA / cm 2 for the composite electrode material for zinc-bromine flow batteries prepared in this example, the energy efficiency of the zinc-bromine flow battery using this composite electrode material is increased from 76.5% of the graphite electrode without using the composite electrode material to 84.1%.

[0096] Example 4

[0097] The preparation method of the composite electrode material for zinc-bromine flow batteries in this example is as follows:

[0098] (1) Prepare copper zinc composite salt: Take the total amount of substance of Cu 2+ and Zn 2+ to be 0.03 mol, and the amount of substance of Na + to be 0.06 mol. Blend and add them to 200 ml of distilled water, stir at room temperature for 12 h, form a mixed solution after mixing evenly, age the mixed solution in air for 24 h, then filter, wash, and finally dry in an oven at 100 °C for 24 h to obtain a black powder, namely copper zinc sulfate.

[0099] (2) Add a certain amount of polyacrylonitrile to an appropriate amount of dimethylformamide under stirring conditions so that the mass fraction of polyacrylonitrile in the whole solution is 14%. Stir for 4 hours at a water bath temperature of 80 °C to obtain a spinning solution, and the average molecular weight of polyacrylonitrile is 150,000.

[0100] (3) Add zinc copper sulfate powder to the spinning solution. The mass ratio of the added zinc copper sulfate to polyacrylonitrile in the solution is 1:2. After stirring for 24 hours, then ultrasonicate for 2 hours to obtain a uniform composite spinning solution.

[0101] (4) Add the composite spinning solution obtained in step (3) into a 25 ml syringe, and use the high-voltage electrospinning technique to obtain a precursor nanofiber material. The thickness of the nanofiber membrane is 2.0 mm; among them, the electrospinning process parameters are: the needle aperture is 0.9 mm, the distance between the needle and the nanofiber membrane collection plate on the roller is 25 cm, the electrospinning voltage between the needle and the roller is 30 kV, the collection plate is tinfoil with a thickness of 100 μm, the rotation speed of the roller is 800 revolutions per minute, the flow rate of the spinning solution is 2.0 mm / minute, the spinning temperature is 40 °C, and the humidity is 50% RH.

[0102] (5) Place the precursor nanofiber material obtained in step (4) into a tubular furnace for pre-oxidation and carbonization treatment. The pre-oxidation temperature is 300 °C, the heating rate is 15 °C / minute, the holding time is 2 hours, and the atmosphere is air; the carbonization temperature is 1000 °C, the heating rate is 10 °C / minute, the holding time is 3 hours, the inert protective atmosphere is nitrogen, and the gas flow rate is 80 ml / minute.

[0103] (6) Wash the carbonized material obtained in step (5) with deionized water 3 - 4 times, and then place it in a vacuum drying oven at 100 °C for a holding time of 8 hours. After drying, a composite electrode material for zinc-bromine flow battery with a thickness of 1.0 mm is obtained, which is a block formed by entanglement of nanofibers of carbon modified with zinc copper sulfide composite catalyst. In this composite electrode material for zinc-bromine flow battery, the zinc sulfide / copper catalyst accounts for 6.2 wt%.

[0104] The specific surface area of the composite electrode material for zinc-bromine flow battery prepared in this example is 127.6 m 2 / g, which is 2 orders of magnitude higher than the specific surface area of the carbon felt electrode (3.2 m 2 / g). At the same time, using electrospinning to spin the electrocatalytically active zinc copper sulfide composite catalyst into the interior of the nanofibers not only improves the electrocatalytic activity of the electrode, but also fixes the catalyst well on the electrode matrix, ensuring the stability of the electrode material.

[0105] The composite electrode material for zinc-bromine flow battery prepared in this example has a current density of 80 mA / cm 2Under the constant current charge-discharge test conditions, the energy efficiency of the zinc-bromine flow battery using this composite electrode material is increased from 76.5% of the graphite electrode without using the composite electrode material to 81.4%.

[0106] Example 5

[0107] The preparation method of the composite electrode material for the zinc-bromine flow battery in this example is as follows:

[0108] (1) Prepare zinc copper composite salt: Take Cu 2+ and Zn 2+ with a total amount of substance of 0.05 mol, and Na + with a substance amount of 0.1 mol and blend them into 250 ml of distilled water. Stir at room temperature for 10 h, and after mixing evenly, form a mixed solution. Age the mixed solution in air for 12 h, then filter and wash it, and finally dry it in an oven at 80 °C for 12 h to obtain black powder, that is, zinc copper sulfate;

[0109] (2) Add a certain amount of polyacrylonitrile to an appropriate amount of dimethylformamide under stirring conditions to make the mass fraction of polyacrylonitrile in the whole solution 15%. Stir at a water bath temperature of 80 °C for 4 hours to obtain a spinning solution, and the average molecular weight of polyacrylonitrile is 100,000.

[0110] (3) Add the zinc copper sulfate powder to the spinning solution, and the mass ratio of the added zinc copper sulfate to polyacrylonitrile in the solution is 1:1. After stirring for 12 hours, then ultrasonic for 3 hours to obtain a uniform composite spinning solution.

[0111] (4) Add the composite spinning solution obtained in step (3) into a 40 ml syringe, and use the high-voltage electrospinning technology to obtain a precursor nanofiber material, and the thickness of the nanofiber membrane is 2.5 mm; among them, the electrospinning process parameters are: the needle aperture is 1.0 mm, the distance between the needle and the nanofiber membrane collecting plate on the roller is 25 cm, the spinning voltage between the needle and the roller is 20 kV, the collecting plate is a 100-μm-thick tin foil, the rotation speed of the roller is 1000 revolutions per minute, the spinning solution flow rate is 2.5 mm / minute, the spinning temperature is 30 °C, and the humidity is 40% RH.

[0112] (5) Place the precursor nanofiber material obtained in step (4) into a tube furnace for pre-oxidation and carbonization treatment. The pre-oxidation temperature is 280 °C, the heating rate is 15 °C / minute, the holding time is 3 hours, and the atmosphere is air; the carbonization temperature is 800 °C, the heating rate is 10 °C / minute, the holding time is 4 hours, the inert protective atmosphere is nitrogen, and the gas flow rate is 100 ml / minute.

[0113] (6) The carbonized material obtained in step (5) is washed with deionized water 3 to 4 times, and then placed in a vacuum drying oven at 100 °C for 48 hours of heat preservation. After drying, a composite electrode material for zinc-bromine flow batteries with a thickness of 1.2 mm is obtained, which is a block formed by entanglement of nanometer carbon fibers modified with copper zinc sulfide composite catalyst. In this electrode material, the copper zinc sulfide composite catalyst accounts for 8.5 wt%.

[0114] The specific surface area of the composite electrode material for zinc-bromine flow batteries prepared in this example is 141.2 m 2 / g, which is two orders of magnitude higher than that of the carbon felt electrode (3.2 m 2 / g). At the same time, by electrospinning, the electrocatalytically active copper zinc sulfide composite catalyst is spun into the interior of the nanometer carbon fibers, which not only improves the electrocatalytic activity of the electrode, but also fixes the catalyst well on the electrode matrix, ensuring the stability of the electrode material.

[0115] Under the constant current charge-discharge test conditions with a current density of 80 mA / cm 2 for the composite electrode material for zinc-bromine flow batteries prepared in this example, the energy efficiency of the zinc-bromine flow battery using this composite electrode material is increased from 76.5% of the graphite electrode without using the composite electrode material to 80.4%.

[0116] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A preparation method of a composite electrode material for a zinc-bromine flow battery, characterized in that, It includes the following steps: S1. Stir copper salt, zinc salt, sodium salt and distilled water evenly at room temperature to form a mixed solution. After aging treatment in air, filter, wash and dry to obtain zinc copper composite salt. S2. Add the polymer to the organic solvent under stirring conditions, and stir under water bath conditions to obtain a spinning solution. Then add the zinc copper composite salt, stir and perform ultrasonic dispersion to obtain a composite spinning solution. S3. Use high-voltage electrostatic spinning to make the composite spinning solution into a precursor nanofiber material. S4. Perform pre-oxidation and carbonization treatment on the precursor nanofiber material in an atmosphere furnace. After that, wash and dry the carbonized material to obtain a composite electrode material for zinc bromide flow battery.

2. The preparation method of the composite electrode material for zinc-bromine flow battery according to claim 1, characterized in that, In the step S1: The copper salt is selected from one or more of copper sulfate, copper nitrate and copper acetate. The zinc salt is selected from one or more of zinc acetate, zinc sulfate and zinc nitrate. The sodium salt is selected from one or two of sodium diethyldithiocarbamate and sodium dimethyldithiocarbamate.

3. The preparation method of the composite electrode material for a zinc-bromine flow battery according to claim 1, wherein, In the step S1: In the mixed solution, Cu 2+ and Zn 2+ have a total amount of substance of 0.01 - 0.05 mol, Na + has an amount of substance of 0.02 - 0.1 mol, and the volume of distilled water is 50 - 250 mL; The stirring time is 5 - 12 h, and the aging time is 6 - 24 h. The drying temperature is 60 - 100 °C, and the drying time is 5 - 24 h.

4. The preparation method of the composite electrode material for zinc-bromine flow battery according to claim 1, characterized in that, In the step S2: The polymer is selected from one or more of polyacrylonitrile, polyimide, polyvinylpyrrolidone and polymethyl methacrylate. The organic solvent is selected from one or more of ethanol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and acetone.

5. The preparation method of the composite electrode material for a zinc-bromine flow battery according to claim 1, characterized in that, In the step S2: The weight ratio of the polymer, zinc copper composite salt to the organic solvent is 1:0.5 - 7:6 - 20; and / or The temperature of the water bath is 40 - 100 °C, the total stirring time is 4 - 28 h, and the ultrasonic dispersion time is 2 - 6 h.

6. The preparation method of the composite electrode material for zinc-bromine flow battery according to claim 5, characterized in that, The weight ratio of the polymer, zinc copper composite salt to the organic solvent is 1:0.5 - 5:8 - 15; and / or The water bath temperature is 60 - 80 °C.

7. The preparation method of the composite electrode material for zinc-bromine flow battery according to claim 1, characterized in that, In the step S3, the process parameters of the high-voltage electrostatic spinning are: the needle aperture is 0.3 - 2.0 mm, the syringe capacity is 5 - 500 ml, the spinning solution flow rate is 0.2 - 5 mm / min, the rotation speed of the roller is 100 - 1000 r / min, the voltage between the needle and the roller is 10 - 30 kV, the distance between the needle and the nanofiber membrane collecting plate on the roller is 10 - 30 cm, the spinning temperature is 25 - 45 °C, and the spinning humidity is 20 - 70%RH.

8. The preparation method of the composite electrode material for a zinc-bromine flow battery according to claim 7, characterized in that, In the step S3: The high-voltage electrostatic spinning adopts one of single needle, multi-needle and needleless; and / or The nanofiber membrane collecting plate on the roller is made of one or more of carbon paper, graphite paper, carbon cloth, aluminum foil, tin foil and alumina foil.

9. The preparation method of the composite electrode material for zinc-bromine flow battery according to claim 1, characterized in that, In the step S4: The pre-oxidation treatment is carried out in an air atmosphere, the pre-oxidation temperature is 200 - 300 °C, the holding time is 1 - 6 h, and the atmosphere is air; and / or The carbonization treatment is carried out in a protective atmosphere, the carbonization temperature is 600 - 1800 °C, the holding time is 1 - 12 h; the protective atmosphere adopts nitrogen or argon; and / or After washing, the carbonized material is dried in a vacuum drying oven or a forced-air drying oven at a drying temperature of 60-100 °C for 6-48 h.

10. The preparation method of the composite electrode material for zinc-bromine flow batteries according to claim 9, characterized in that, The heating rate for the pre-oxidation treatment is 2-20 °C / min; the heating rate for the carbonization treatment is 2-25 °C / min, and the flow rate of the protective gas is 20-100 mL / min.

11. A composite electrode material for a zinc-bromine flow battery prepared by using the preparation method of the composite electrode material for a zinc-bromine flow battery according to any one of claims 1-10.

12. The composite electrode material for a zinc-bromine flow battery according to claim 11, wherein: The composite electrode material for a zinc-bromine flow battery contains a copper zinc sulfide composite catalyst, and its proportion is 1-10 wt%; and / or The thickness of the composite electrode material for a zinc-bromine flow battery is 1-3.5 mm; and / or The specific surface area of the composite electrode material for the zinc-bromine flow battery is 125 to 165 m 2 / g.

13. An application of the composite electrode material for a zinc-bromine flow battery according to claim 11 in a zinc-bromine flow battery.

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