Modification method of carbon electrode for flow battery, carbon electrode and flow battery

Abstract

The invention relates to a modification method of a carbon electrode for a flow battery, the carbon electrode and the flow battery. The modification method comprises the following steps: pretreating a carbon electrode; cobalt-based alloy powder is sprayed to the pretreated carbon electrode in a sand blasting mode, and the carbon electrode loaded with the cobalt-based alloy powder is formed; heating the carbon-based electrode loaded with the powder of the cobalt-based alloy by an induction coil and cooling the carbon-based electrode to room temperature; and washing the obtained carbon electrode and drying the carbon electrode to obtain the modified carbon electrode. The electrode modification method provided by the invention is simple and feasible in process, and the electrical property of the carbon electrode is remarkably improved. The modified electrode provided by the invention not only can be suitable for an all-vanadium redox flow battery system, but also can be expanded to other types of redox flow battery systems.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flow battery, and particularly relates to a modification method of carbon-based electrode for flow battery, carbon-based electrode and flow battery. BACKGROUND

[0002] The flow battery is an electrochemical energy storage device for storing electricity through electrolyte. At present, the electrode of the flow battery stack usually adopts carbon-based materials such as carbon felt and graphite felt, which has the characteristics of good electrical conductivity, large specific surface area, high porosity, low cost and good mechanical stability, but also has the shortcomings of poor hydrophilicity and insufficient electrochemical activity.

[0003] In order to improve the hydrophilicity and activity of the carbon-based electrode, there are currently many methods for modifying the carbon-based electrode, such as heat treatment, chemical treatment, metal modification and graphene modification. However, the methods of heat treatment and metal modification cannot improve the hydrophilicity of the carbon-based electrode such as carbon felt and graphite felt; the chemical treatment often uses nitric acid and concentrated sulfuric acid, which is dangerous and high in cost.

[0004] Therefore, there is a need for an improved modification method of carbon-based electrode for flow battery, carbon-based electrode and flow battery. SUMMARY

[0005] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of protection of the present application.

[0006] The present application provides a modification method of carbon-based electrode for flow battery, carbon-based electrode and flow battery.

[0007] In one aspect, the present application provides a method for modifying a carbon-based electrode for flow battery, the method comprising the following steps: S1: pretreating the carbon-based electrode; S2: spraying the powder of cobalt-based alloy onto the pretreated carbon-based electrode by sandblasting to form a carbon-based electrode loaded with the powder of cobalt-based alloy; S3: heating the carbon-based electrode loaded with the powder of cobalt-based alloy by an induction coil and cooling to room temperature; S4: washing the carbon-based electrode obtained in step S3 and drying, i.e. obtaining the modified carbon-based electrode; wherein the cobalt-based alloy has the formula Co a Cr b W c Fe d Ni e Mo f C g, a represents the atomic percentage of cobalt element, b represents the atomic percentage of chromium element, c represents the atomic percentage of tungsten element, d represents the atomic percentage of iron element, e represents the atomic percentage of nickel element, f represents the atomic percentage of molybdenum element, and g represents the atomic percentage of carbon element, a is in the range of 50-65, b is in the range of 20-30, c is in the range of 0.5-10, d is in the range of 1-5, e is in the range of 1-5, f is in the range of 1-5, and g is in the range of 0.1-2; The melting point of the powder of the cobalt-based alloy is in the range of 1300℃-1400℃; The particle size of the powder of the cobalt-based alloy is in the range of 100 nm-1000 nm; The material of the carbon-based electrode is graphite felt or carbon felt.

[0008] In an embodiment, the cobalt-based alloy is selected from one or more of Co 59 Cr 29 W4Fe3Ni3MoC, Co 54.6 Cr 29 W8Fe3Ni3MoC 1.4 , Co 62.2 Cr 27 W 0.5 Fe2Ni3Mo5C 0.3 .

[0009] In an embodiment, in step S1, the pre-treatment of the carbon-based electrode includes ultrasonic cleaning of the carbon-based electrode using deionized water and drying.

[0010] In an embodiment, the time of ultrasonic cleaning of the carbon-based electrode using deionized water is 10-60 min, the drying temperature is 40-100℃, and the drying time is 2-6h.

[0011] In an embodiment, in step S2, the forming of the carbon-based electrode loaded with the powder of the cobalt-based alloy includes having 10-100g of the powder of the cobalt-based alloy per square meter of the carbon-based electrode.

[0012] In an embodiment, in step S3, the frequency of the induction coil is in the range of 1 KHz-20 KHz, and the power of the induction coil is in the range of 100kw-1000kw.

[0013] In an embodiment, in step S3, the heating lasts for 0.1-2 seconds.

[0014] In an embodiment, in step S4, the washing of the carbon-based electrode obtained in step S3 includes ultrasonic washing lasting for 10-60 min, the drying temperature is 40-100℃, and the drying time is 2-6h.

[0015] On the other hand, this application provides a carbon-based electrode for a flow battery, wherein the carbon-based electrode is modified by the method described above.

[0016] In another aspect, this application provides a flow battery including the above-described modified carbon-based electrode.

[0017] The induction coil heating method used in this application has the advantages of fast heating speed, high thermal efficiency, and relatively uniform heating through coil design. This helps to form a uniform cobalt alloy modification layer and avoids local overheating or poor bonding.

[0018] The method of this application heats cobalt-based alloy powder with an induction coil at high temperatures, causing it to interact with the surface of a carbon-based electrode, such as carbon felt, potentially forming carbides or metallurgical bonds, rather than simply physical adhesion, thus achieving excellent stability and strong adhesion. Compared with conventional coating, drop coating, or electrodeposition methods, the modified layer prepared by the method used in this application is less prone to peeling off. When used as an electrode for electrochemical reactions (especially in environments with fluid impact or bubble generation), the risk of coating peeling is greatly reduced, ensuring the long-term stability of electrode performance.

[0019] This application loads cobalt alloys onto carbon-based electrodes such as carbon felt. Through the synergistic effect between different metal elements, the electronic structure is further optimized, improving intrinsic catalytic activity and selectivity, and significantly enhancing the catalytic performance of the originally weak carbon felt electrode. The cobalt alloy used in this application exhibits good corrosion resistance to acids, alkalis, salts, and organic media, especially performing exceptionally well in corrosive environments containing sulfur and chloride ions, thereby extending the service life of carbon-based electrodes such as carbon felt in flow batteries.

[0020] This application employs a sandblasting method to "blow" powder onto the carbon fibers of a carbon-based electrode, forming a porous, rough catalytic layer that further increases the specific surface area of ​​the carbon-based electrode. A larger specific surface area exposes more catalytically active sites, allowing reactants (such as H2O, O2, and pollutant molecules) to come into more thorough contact with the catalyst, thereby improving reaction efficiency. Furthermore, the sandblasting treatment used in this application not only loads cobalt alloy powder but also roughens the surface of the carbon-based electrode, increasing surface energy and facilitating bonding with the cobalt alloy layer, achieving high bonding strength.

[0021] This application utilizes high-temperature treatment to create excellent electrical contact between the cobalt alloy layer and the carbon fibers of the carbon-based electrode, constructing a continuous, highly conductive three-dimensional network. This ensures that electrons can be rapidly transferred from the current collector to the catalytic active site during the electrochemical reaction, reducing the internal resistance of the electrode and improving energy efficiency.

[0022] The method described in this application is simple, easy to operate, low in cost, and scalable. The entire process (pretreatment-sandblasting-heat treatment-washing) has clear steps, is easy to operate and control, and has the potential to move from the laboratory to industrial-scale production.

[0023] The carbon-based electrode modified by the method described in this application combines the advantages of carbon materials, such as large specific surface area, good conductivity, and three-dimensional structure, with the advantages of cobalt-based alloys, such as high catalytic activity and stability.

[0024] The carbon-based electrodes modified using the method described in this application, when applied to flow battery stack structures such as vanadium redox flow battery stacks, exhibit excellent stability during battery operation. After 1000 charge-discharge cycles, the electrodes show no significant morphological changes, and their electrical performance remains excellent; for example, after 1000 charge-discharge cycles, the electrode maintains a stable electrical performance of 240 mA / cm². 2 The voltage efficiency at current density can still be maintained above 86%.

[0025] The modification method described in this application is simple and easy to implement, and significantly improves the conductivity and stability of carbon-based electrodes. It is not only applicable to all-vanadium redox flow batteries, but can also be extended to other types of flow battery systems, such as zinc-bromine flow batteries.

[0026] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the embodiments described in the description and the accompanying drawings. Attached Figure Description

[0027] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0028] Figure 1 A diagram showing the appearance of the original carbon felt electrode provided in Embodiments 1 and 2 according to this disclosure; Figure 2A and Figure 2B The graphs show the cyclic voltammetry curves of the positive and negative electrodes of the modified carbon felt electrode and the original carbon felt electrode provided in Embodiment 1 according to the present disclosure, respectively. Figure 3 To illustrate the modified carbon felt electrode and the original carbon felt electrode provided in Example 1 according to this disclosure at 160 mA / cm 2 and 240mA / cm 2 A graph of voltage efficiency at current density; Figure 4A and Figure 4BThe graphs shown are the cyclic voltammetry curves of the positive and negative electrodes of the modified carbon felt electrode and the original carbon felt electrode provided in Embodiment 2 according to the present disclosure; and Figure 5 To illustrate the modified carbon felt electrode and the original carbon felt electrode provided in Example 2 according to this disclosure at 160 mA / cm 2 and 240mA / cm 2 A graph showing the voltage efficiency at current density. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application are described in detail below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be arbitrarily combined with each other.

[0030] The following examples use carbon felt as an example of a carbon-based electrode and a vanadium redox flow battery for illustration, but do not limit the application of other carbon-based electrodes in other flow batteries.

[0031] Unless otherwise specified, all materials used in the following examples are commercially available.

[0032] Example 1 like Figure 1 As shown, the original carbon felt used in this embodiment has a size of 500mm×300mm×4.2mm.

[0033] The raw carbon felt was ultrasonically cleaned with deionized water for 30 minutes. The cleaned carbon felt was then dried in an oven at 80℃ for 4 hours. The dried carbon felt was then placed in a sandblasting machine. 59 Cr 29 W4Fe3Ni3MoC cobalt-based alloy powder is filled into the spray gun canister and then uniformly sprayed into the carbon felt using a sandblasting method, so that each square meter of carbon felt contains 50g of cobalt-based alloy powder (i.e., 50g / m²). 2 The carbon felt loaded with alloy powder is heated by an induction coil for 1 second at a frequency of 1 kHz. After natural cooling to room temperature, the carbon felt is ultrasonically cleaned with deionized water for 30 minutes and then dried in a drying oven at 80°C for 4 hours to obtain the modified carbon felt electrode.

[0034] Performance testing Hydrophilicity tests were performed on the modified carbon felt electrode and the original carbon felt electrode from Example 1. The results showed that the original carbon felt electrode had a contact angle of 120° and poor hydrophilicity; while the modified carbon felt electrode prepared in Example 1 had a contact angle of 10° and excellent hydrophilicity. Excellent hydrophilicity is one of the basic requirements for electrode materials in vanadium redox flow batteries.

[0035] The modified carbon felt electrode and the original carbon felt electrode from Example 1 were tested for electrochemical performance in a vanadium redox flow cell. Cyclic voltammetry scans were performed on a three-electrode electrolytic cell consisting of the modified carbon felt electrode and the original carbon felt electrode from Example 1, respectively, as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode. The cyclic voltammetry curves of the modified carbon felt electrode and the original carbon felt electrode from Example 1 were obtained, and the results are as follows: Figure 2A and Figure 2B As shown. By Figure 2A and Figure 2B As can be seen, the carbon felt electrode modified using the method in Example 1 exhibits the smallest redox peak position difference and the largest peak current, demonstrating superior electrochemical activity compared to the original carbon felt electrode; the modified carbon felt electrode also exhibits excellent electrochemical activity for the positive electrode reaction (V0). 5+ / V 4+ ) and negative electrode reaction (V 2+ / V 3+ All of them exhibit good electrochemical activity. This further demonstrates the universality and scalability of the carbon-based electrodes modified by the modification method of this application for improving the electrochemical reaction activity of vanadium redox flow batteries.

[0036] The modified carbon felt electrode from Example 1 and the original carbon felt electrode were used as positive and negative electrodes to assemble an all-vanadium redox flow battery stack. The stack was assembled according to the structure of end plate-bipolar plate-electrode-proton exchange membrane-electrode-bipolar plate-electrode-proton exchange membrane-electrode-bipolar plate-end plate. The flow battery was tested at 160 mA / cm². 2 and 240 mA / cm 2 Constant current charge-discharge tests were performed at current density, and the results are as follows: Figure 3 As shown. By Figure 3 It can be seen that, compared with the original carbon felt electrode, the flow battery containing the modified carbon felt electrode of Example 1 exhibits higher voltage efficiency at both different current densities. Furthermore, Figure 3 It is also shown that the voltage efficiency of the modified electrode of this application remains almost unchanged with the increase of charge-discharge cycle number, while the voltage efficiency of the original carbon felt electrode decreases with the increase of charge-discharge cycle number. This indicates that the carbon electrode modified by the modification method of this application has significantly better stability than the original carbon felt electrode.

[0037] Example 2 like Figure 1 As shown, the original carbon felt used in this embodiment has a size of 500mm×300mm×4.2mm.

[0038] The raw carbon felt was ultrasonically cleaned with deionized water for 30 minutes. The cleaned carbon felt was then dried in an oven at 80℃ for 4 hours. The dried carbon felt was then placed in a sandblasting machine. 54.6 Cr 29W8Fe3Ni3MoC 1.4 Cobalt-based alloy powder is filled into the spray gun canister and then evenly sprayed into the carbon felt using a sandblasting method, so that each square meter of carbon felt contains 50g of cobalt-based alloy powder (i.e., 50g / m²). 2 The carbon felt loaded with alloy powder is heated by an induction coil for 1 second at a frequency of 1 kHz. After natural cooling to room temperature, the carbon felt is ultrasonically cleaned with deionized water for 30 minutes and then dried in a drying oven at 80°C for 4 hours to obtain the modified carbon felt electrode.

[0039] Performance testing Hydrophilicity tests were performed on the modified carbon felt electrode and the original carbon felt electrode from Example 2. The results showed that the original carbon felt electrode had a contact angle of 120° and poor hydrophilicity; while the modified carbon felt electrode prepared in Example 2 had a contact angle of 12° and excellent hydrophilicity. Excellent hydrophilicity is one of the basic requirements for electrode materials in vanadium redox flow batteries.

[0040] The modified carbon felt electrode and the original carbon felt electrode from Example 2 were subjected to electrochemical performance testing in a vanadium redox flow battery. Cyclic voltammetry scans were performed on a three-electrode electrolytic cell consisting of the modified carbon felt electrode and the original carbon felt electrode from Example 2, respectively, as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode. The cyclic voltammetry curves of the modified carbon felt electrode and the original carbon felt electrode from Example 2 were obtained, and the results are as follows: Figure 4A and Figure 4B As shown. By Figure 4A and Figure 4B As can be seen, the carbon felt electrode modified using the method in Example 2 exhibits the smallest redox peak position difference and the largest peak current, demonstrating superior electrochemical activity compared to the original carbon felt electrode; the modified carbon felt electrode also exhibits excellent electrochemical activity for the positive electrode reaction (V0). 5+ / V 4+ ) and negative electrode reaction (V 2+ / V 3+ All of them exhibit good electrochemical activity. This further demonstrates the universality and scalability of the carbon-based electrodes modified by the modification method of this application for improving the electrochemical reaction activity of vanadium redox flow batteries.

[0041] The modified carbon felt electrode from Example 2 and the original carbon felt electrode were used as positive and negative electrodes to assemble an all-vanadium redox flow battery stack. The stack was assembled according to the structure of end plate-bipolar plate-electrode-proton exchange membrane-electrode-bipolar plate-electrode-proton exchange membrane-electrode-bipolar plate-end plate. The flow battery was tested at 160 mA / cm². 2 and 240 mA / cm 2 Constant current charge-discharge tests were performed at current density, and the results are as follows: Figure 5 As shown. By Figure 5It can be seen that, compared with the original carbon felt electrode, the flow battery containing the modified carbon felt electrode of Example 2 exhibits higher voltage efficiency at both different current densities. Furthermore, Figure 5 It is also shown that the voltage efficiency of the modified electrode of this application remains almost unchanged with the increase of charge-discharge cycle number, while the voltage efficiency of the original carbon felt electrode decreases with the increase of charge-discharge cycle number. This indicates that the carbon electrode modified by the modification method of this application has significantly better stability than the original carbon felt electrode.

[0042] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method of modifying a carbon-based electrode for a flow battery, characterized by, The method comprises the following steps: S1: pretreating a carbon-based electrode; S2: spraying a cobalt-based alloy powder onto the pretreated carbon-based electrode by sandblasting to form a carbon-based electrode loaded with the cobalt-based alloy powder; S3: heating the carbon-based electrode loaded with the cobalt-based alloy powder by an induction coil and cooling to room temperature; S4: washing the carbon-based electrode obtained in step S3 and drying, i.e. obtaining a modified carbon-based electrode; wherein the cobalt-based alloy has the formula Co a Cr b W c Fe d Ni e Mo f C g , a represents the atomic percentage of cobalt element, b represents the atomic percentage of chromium element, c represents the atomic percentage of tungsten element, d represents the atomic percentage of iron element, e represents the atomic percentage of nickel element, f represents the atomic percentage of molybdenum element, and g represents the atomic percentage of carbon element, a is in the range of 50-65, b is in the range of 20-30, c is in the range of 0.5-10, d is in the range of 1-5, e is in the range of 1-5, f is in the range of 1-5, and g is in the range of 0.1-2; The melting point of the cobalt-based alloy powder is in the range of 1300-1400℃; The particle size of the cobalt-based alloy powder is in the range of 100-1000 nm; The material of the carbon-based electrode is graphite felt or carbon felt.

2. The method of claim 1, wherein, wherein the cobalt-based alloy is selected from Co 59 Cr 29 W4Fe3Ni3MoC, Co 54.6 Cr 29 W8Fe3Ni3MoC 1.4 , Co 62.2 Cr 27 W 0.5 Fe2Ni3Mo5C 0.3 one or more of.

3. The method according to claim 1 or 2, characterized in that, In step S1, the pretreatment of the carbon-based electrode comprises ultrasonic cleaning of the carbon-based electrode with deionized water and drying.

4. The method of claim 3, wherein, The ultrasonic cleaning time of the deionized water is 10-60 min, the drying temperature is 40-100℃, and the drying time is 2-6 h.

5. The method according to claim 1 or 2, characterized in that, In step S2, forming the carbon-based electrode loaded with the cobalt-based alloy powder comprises having 10-100 g of the cobalt-based alloy powder per square meter of the carbon-based electrode.

6. The method of claim 1 or 2, wherein, In step S3, the frequency of the induction coil is in the range of 1-20 KHz, and the power of the induction coil is in the range of 100-1000 kw.

7. The method according to claim 1 or 2, characterized in that, In step S3, the heating lasts for 0.1-2 seconds.

8. The method of claim 1 or 2, wherein, In step S4, washing the carbon-based electrode obtained in step S3 comprises ultrasonic washing for 10-60 min, the drying temperature is 40-100℃, and the drying time is 2-6 h.

9. A carbon-based electrode for a flow battery, characterized in that, The carbon-based electrode is modified by the method according to any one of claims 1-8.

10. A flow battery, characterized in that, The carbon-based electrode according to claim 9 is included.

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