Carbon felt electrode for flow battery and preparation method of carbon felt electrode

Abstract

The embodiment of the invention relates to the technical field of flow batteries, and provides a carbon felt electrode for a flow battery and a preparation method thereof, and the preparation method comprises the following steps: preparing a mixed salt solution containing first metal ions and second metal ions; preparing an alcohol solution containing 2-methylimidazole; adding the mixed salt solution into the alcohol solution, and uniformly mixing to obtain a precursor solution; immersing the cleaned carbon felt into the precursor solution for a first time, then taking out the carbon felt, cleaning the carbon felt with an alcohol solvent, and drying the carbon felt to obtain a ZIF carbon felt; and putting the ZIF carbon felt into a tube furnace protected by inert gas, and carrying out heat treatment at a preset temperature for a preset second time to obtain the carbon felt electrode. The invention provides a novel bimetallic catalyst, and the interaction between metals can promote the adsorption and activation of reactants on metal atoms and promote the proceeding of the reaction. In the nitrogen-carbon catalyst formed by carbonizing ZIF, metal ions are uniformly dispersed, and agglomeration of the metal ions in the synthesis process is prevented.

Description

Technical Field

[0001] The present disclosure relates to the technical field of liquid flow batteries, and in particular to a carbon felt electrode for a liquid flow battery and a preparation method thereof. Background Art

[0002] Liquid flow batteries are widely used in renewable energy storage and grid peak regulation due to their flexible and adjustable decoupling of power and energy, long cycle life, low capacity decay, and rapid deep charge and discharge. Among liquid flow batteries, all-vanadium liquid flow batteries are currently the most technologically mature, but the high cost of their ionic electrolytes limits further cost reductions. Furthermore, strongly acidic electrolytes are highly corrosive to various components. In contrast, neutral iron-sulfur liquid flow battery systems offer a broader range of development opportunities due to their low electrolyte cost and non-corrosive nature. However, their stacks have a relatively low current density and require further optimization.

[0003] Electrodes are where redox reactions occur in flow batteries. Electrode materials are commonly carbon-based, primarily graphitized carbon felt. Carbon felt is an organic polymer fiber felt that undergoes heat treatment processes such as pre-oxidation and carbonization in an inert atmosphere, followed by further graphitization at high temperatures. Compared to various types of carbon felt, PAN-based carbon felt has higher porosity and lower electrical resistance, facilitating the transport of active substances in flow batteries, making it one of the most commonly used carbon felt materials. Carbon felt is relatively inexpensive and offers advantages such as good stability and outstanding conductivity. However, it also suffers from poor surface hydrophilicity, low specific surface area, and low electrochemical activity, which are key factors contributing to the low power density of vanadium batteries. High-performance electrodes with high hydrophilicity, specific surface area, and electrochemical activity are the core technology of high-power fuel cell stacks. The introduction of catalysts has a positive effect on improving the electrochemical activity of carbon felt electrodes. However, traditional metal catalyst materials have poor electrochemical reversibility. While precious metal-based catalysts such as platinum and iridium have advantages such as high electrochemical activity, good reversibility, and good chemical stability, these catalysts have low specific surface areas and are expensive, which restricts their large-scale application in flow batteries. Furthermore, the adhesion of various catalysts to the carbon fiber surface is poor, and the loading stability needs to be further improved. Summary of the Invention

[0004] The present disclosure aims to solve at least one of the problems existing in the prior art and provides a carbon felt electrode for a flow battery and a preparation method thereof.

[0005] One aspect of the present disclosure provides a method for preparing a carbon felt electrode for a flow battery, the method comprising:

[0006] Preparing a mixed salt solution containing a first metal ion and a second metal ion; wherein the first metal ion and the second metal ion are different;

[0007] Prepare an alcohol solution containing 2-methylimidazole;

[0008] adding the mixed salt solution to the alcohol solution and mixing them evenly to obtain a precursor solution;

[0009] Immersing the cleaned carbon felt in the precursor solution for a predetermined time, then taking it out and washing it with an alcohol solvent and then drying it to obtain ZIF@carbon felt;

[0010] The ZIF@carbon felt is placed in a tubular furnace protected by inert gas, and heat-treated at a preset temperature for a preset second time to obtain a carbon felt electrode.

[0011] Optionally, the preparation of the mixed salt solution containing the first metal ion and the second metal ion comprises:

[0012] A mixed salt solution of zinc nitrate and cobalt nitrate was prepared with methanol as solvent.

[0013] Optionally, the method of using methanol as a solvent to prepare a mixed salt solution of zinc nitrate and cobalt nitrate comprises:

[0014] Using methanol as solvent, prepare a mixed salt solution of 10mg / ml to 30mg / ml zinc nitrate and 10mg / ml to 30mg / ml cobalt nitrate.

[0015] Optionally, the configuration of the alcohol solution containing 2-methylimidazole includes:

[0016] Prepare 180 mg / ml to 220 mg / ml of 2-methylimidazole in methanol.

[0017] Optionally, the preset first time range is 11h~13h.

[0018] Optionally, the alcohol solvent is methanol.

[0019] Optionally, the preset temperature range is 550°C to 650°C.

[0020] Optionally, the preset second time range is 1 hour to 3 hours.

[0021] Optionally, the inert gas is argon.

[0022] Another aspect of the present disclosure provides a carbon felt electrode for a liquid flow battery, wherein the carbon felt electrode for a liquid flow battery is prepared using the preparation method described above.

[0023] Compared to the prior art, the present disclosure provides a novel bimetallic catalyst. Compared to monometallic catalysts, its advantage is that the interaction between the metals can promote the adsorption and activation of reactants on metal atoms, thereby promoting the reaction. In the nitrogen-carbon catalyst carbonized with ZIF, the metal ions are evenly dispersed, preventing the agglomeration of metal ions during the synthesis process. After the ZIF is carbonized by in-situ growth on carbon felt, the material is stably bonded to the carbon felt, and the load stability is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings, and these exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0025] Figure 1 A flow chart of a method for preparing a carbon felt electrode for a flow battery provided in one embodiment of the present disclosure. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. However, it will be understood by those skilled in the art that in each embodiment of the present disclosure, many technical details are provided to enable readers to better understand the present disclosure. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present disclosure can be implemented. The division of the following embodiments is for the convenience of description and should not constitute any limitation on the specific implementation of the present disclosure. The various embodiments can be combined and referenced with each other under the premise that there is no contradiction.

[0027] One embodiment of the present disclosure relates to a method for preparing a carbon felt electrode for a flow battery, the process of which is as follows: Figure 1 Shown, including:

[0028] Step S110: preparing a mixed salt solution containing a first metal ion and a second metal ion; wherein the first metal ion and the second metal ion are different.

[0029] Specifically, in this step, a mixed salt solution of zinc nitrate and cobalt nitrate is prepared using methanol as a solvent. In some embodiments, a mixed salt solution of 10 mg / ml to 30 mg / ml of zinc nitrate and 10 mg / ml to 30 mg / ml of cobalt nitrate is prepared, preferably a mixed salt solution of 20 mg / ml of zinc nitrate and 20 mg / ml of cobalt nitrate is prepared.

[0030] Step S120: preparing an alcohol solution containing 2-methylimidazole.

[0031] Specifically, in this step, a 180 mg / ml to 220 mg / ml methanol solution of 2-methylimidazole is prepared, preferably a 200 mg / ml methanol solution of 2-methylimidazole is prepared.

[0032] Step S130: adding the mixed salt solution to the alcohol solution and mixing them evenly to obtain a precursor solution.

[0033] Step S140 , immersing the cleaned carbon felt in the precursor solution for a preset first time, then taking it out and washing it with an alcohol solvent and then drying it to obtain ZIF@carbon felt.

[0034] Specifically, in this step, the cleaned carbon felt is immersed in the precursor solution for 11 to 13 hours, preferably 12 hours, and then removed and washed with an alcohol solvent and dried to obtain ZIF@carbon felt. In some embodiments, the alcohol solvent may be methanol, for example.

[0035] Step S150: placing the ZIF@carbon felt into a tubular furnace protected by inert gas, and subjecting it to heat treatment at a preset temperature for a preset second time to obtain a carbon felt electrode.

[0036] Specifically, in this step, the ZIF@carbon felt is placed in an argon-protected tubular furnace and heat-treated at 550° C. to 650° C. for 1 h to 3 h to obtain a Zn / Co@nitrogen-carbon composite carbon felt electrode.

[0037] In the disclosed embodiments, the inventors have found that parameters such as reaction time, temperature, stirring speed, and feed ratio all have a significant impact on the particle size of ZIF. For example, reaction time: the longer the reaction time, the larger the ZIF particle size; the shorter the time, the smaller the particle size; temperature: lowering the temperature can reduce the nucleation and growth rate of ZIF, increasing the number of nuclei formed. Accordingly, the synthesized ZIF particle size is small and uniform, but the corresponding reaction time is prolonged. Taking all factors into consideration, direct reaction at room temperature has the best economic benefits. Feed ratio: adjusting the feed ratio of 2-methylimidazole to metal ions can also control the ZIF particle size. The protonation reaction of excess 2-methylimidazole with the solvent is the basis for the formation of ZIF nuclei. At the same time, excess neutral 2-methylimidazole will adsorb on the surface of the nuclei, thereby slowing the growth of the nuclei. Therefore, the particle size of ZIF decreases with increasing feed ratio. While this method can easily and effectively produce ZIF-8 with sizes ranging from a few microns to tens of nanometers, it also results in significant waste of raw materials. Too little 2-methylimidazole prevents the effective formation of ZIF. ZIF contains metal ions, nitrogen, and carbon, and carbonization in an inert atmosphere yields a metal-NC composite. Based on these findings, the inventors conducted several experimental studies and proposed the time, temperature, and feed ratios mentioned in the above steps.

[0038] The method for preparing carbon felt electrodes for flow batteries disclosed in the present embodiment provides a novel bimetallic catalyst. Compared to monometallic catalysts, its advantage lies in the intermetallic interaction that promotes the adsorption and activation of reactants on metal atoms, thereby promoting the reaction. The Zn / Co@nitrogen-carbon catalyst, carbonized from ZIF, achieves uniform dispersion of metal ions, preventing metal ion aggregation during the synthesis process. Carbonization of the in-situ grown ZIF on the carbon felt stabilizes the material and carbon felt, improving load stability.

[0039] The following will describe in detail the method for preparing the carbon felt electrode for a liquid flow battery disclosed in the present invention in several embodiments.

[0040] Example 1

[0041] A mixed salt solution of 10 mg / ml zinc nitrate and 10 mg / ml cobalt nitrate was prepared using methanol as solvent.

[0042] Prepare a 180 mg / ml methanol solution of 2-methylimidazole.

[0043] The Zn / Co salt solution prepared above was slowly added to the methanol solution of 2-methylimidazole and mixed evenly to obtain a precursor solution.

[0044] The cleaned carbon felt was immersed in the precursor solution for 11 hours, then taken out and washed with methanol and dried to obtain ZIF@carbon felt.

[0045] The ZIF@carbon felt was placed in an argon-protected tubular furnace and heat-treated at 550° C. for 1 h to obtain a Zn / Co@nitrogen-carbon composite carbon felt electrode.

[0046] Example 2

[0047] Using methanol as solvent, prepare a mixed salt solution of 30 mg / ml zinc nitrate and 30 mg / ml cobalt nitrate.

[0048] Prepare a 220 mg / ml methanol solution of 2-methylimidazole.

[0049] The Zn / Co salt solution prepared above was slowly added to the methanol solution of 2-methylimidazole and mixed evenly to obtain a precursor solution.

[0050] The cleaned carbon felt was immersed in the precursor solution for 13 hours, then taken out and washed with methanol and dried to obtain ZIF@carbon felt.

[0051] The ZIF@carbon felt was placed in an argon-protected tubular furnace and heat-treated at 650° C. for 3 h to obtain a Zn / Co@nitrogen-carbon composite carbon felt electrode.

[0052] Example 3

[0053] A mixed salt solution of 20 mg / ml zinc nitrate and 20 mg / ml cobalt nitrate was prepared using methanol as solvent.

[0054] Prepare a 200 mg / ml methanol solution of 2-methylimidazole.

[0055] The Zn / Co salt solution prepared above was slowly added to the methanol solution of 2-methylimidazole and mixed evenly to obtain a precursor solution.

[0056] The cleaned carbon felt was immersed in the precursor solution for 12 hours, then taken out and washed with methanol and dried to obtain ZIF@carbon felt.

[0057] The ZIF@carbon felt was placed in an argon-protected tubular furnace and heat-treated at 600° C. for 2 h to obtain a Zn / Co@nitrogen-carbon composite carbon felt electrode.

[0058] Another aspect of the present disclosure provides a carbon felt electrode for a liquid flow battery. The carbon felt electrode for a liquid flow battery is prepared using the preparation method described above. For details, please refer to the relevant description above and will not be repeated here.

[0059] The carbon felt electrode for the liquid flow battery of the disclosed embodiment is prepared using the preparation method described above. It provides a new type of bimetallic catalyst. Compared with monometallic catalysts, its advantage is that the interaction between the metals can promote the adsorption and activation of reactants on the metal atoms, thereby promoting the reaction. In the Zn / Co@nitrogen-carbon catalyst carbonized by ZIF, the metal ions are evenly dispersed, preventing the agglomeration of metal ions during the synthesis process. After the ZIF is carbonized by in situ growth on the carbon felt, the material is stably bonded to the carbon felt, and the load stability is improved.

[0060] Those skilled in the art will appreciate that the above-mentioned embodiments are specific embodiments for implementing the present disclosure, and that in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present disclosure.

Claims

1. A method for preparing a carbon felt electrode for a flow battery, characterized in that: The preparation method comprises: Preparing a mixed salt solution containing a first metal ion and a second metal ion; wherein the first metal ion and the second metal ion are different; Prepare an alcohol solution containing 2-methylimidazole; adding the mixed salt solution to the alcohol solution and mixing them evenly to obtain a precursor solution; Immersing the cleaned carbon felt in the precursor solution for a predetermined time, then taking it out and washing it with an alcohol solvent and then drying it to obtain ZIF@carbon felt; The ZIF@carbon felt is placed in a tubular furnace protected by inert gas, and heat-treated at a preset temperature for a preset second time to obtain a carbon felt electrode.

2. The preparation method according to claim 1, characterized in that The preparation of a mixed salt solution containing the first metal ion and the second metal ion comprises: A mixed salt solution of zinc nitrate and cobalt nitrate was prepared with methanol as solvent.

3. The preparation method according to claim 2, characterized in that The method of using methanol as a solvent to prepare a mixed salt solution of zinc nitrate and cobalt nitrate of a predetermined amount comprises: Using methanol as solvent, prepare a mixed salt solution of 10mg / ml to 30mg / ml zinc nitrate and 10mg / ml to 30mg / ml cobalt nitrate.

4. The preparation method according to claim 3, characterized in that The alcohol solution containing 2-methylimidazole is prepared, comprising: Prepare 180 mg / ml to 220 mg / ml of 2-methylimidazole in methanol.

5. The preparation method according to any one of claims 1 to 4, characterized in that The preset first time range is 11 hours to 13 hours.

6. The preparation method according to any one of claims 1 to 4, characterized in that The alcohol solvent is methanol.

7. The preparation method according to any one of claims 1 to 4, characterized in that The preset temperature range is 550°C to 650°C.

8. The preparation method according to any one of claims 1 to 4, characterized in that The preset second time range is 1 hour to 3 hours.

9. The preparation method according to any one of claims 1 to 4, characterized in that The inert gas used is argon.

10. A carbon felt electrode for a liquid flow battery, characterized in that: The carbon felt electrode for liquid flow battery is prepared by the preparation method according to any one of claims 1 to 9.

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