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

Abstract

The present application provides a method for modifying a carbon electrode for a liquid flow battery and the carbon electrode for a liquid flow battery obtained thereby. The method comprises loading iron-based alloy powder onto a carbon electrode by ultrasonic vibration; heating the carbon electrode loaded with the iron-based alloy powder by an induction coil and cooling it to room temperature to obtain a modified carbon electrode. The electrode modification method of the present application is simple and easy to operate, and significantly improves the electrical properties of the carbon electrode. The modified electrode of the present application can not only be applied to the all-vanadium liquid flow battery system, but can also be extended to other types of liquid flow battery systems.

Description

Technical Field

[0001] The present application relates to the field of liquid flow batteries, and in particular to a method for modifying a carbon electrode for a liquid flow battery, a carbon electrode, and a liquid flow battery. Background Art

[0002] Liquid flow battery is an electrochemical energy storage device that stores electricity through electrolyte. At present, the electrodes of liquid flow battery stacks are usually made of carbon materials such as carbon felt and graphite felt, which have the characteristics of good conductivity, large specific surface area, high porosity, low cost and good mechanical stability, but they also have disadvantages such as poor hydrophilicity and insufficient electrochemical activity.

[0003] In order to improve the hydrophilicity and activity of carbon electrodes, there are many methods to modify them, such as heat treatment, chemical treatment, metal modification, graphene modification, etc. However, heat treatment and metal modification methods cannot improve the hydrophilicity of carbon electrodes such as carbon felt and graphite felt; chemical treatment often uses nitric acid and concentrated sulfuric acid, which is more dangerous and costly.

[0004] Therefore, there is a need for an improved method for modifying a carbonaceous electrode for a flow battery, a carbonaceous electrode, and a flow battery. Summary of the invention

[0005] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of protection of this application.

[0006] The present application provides a method for modifying a carbon electrode for a liquid flow battery, a carbon electrode and a liquid flow battery.

[0007] In one aspect, the present application provides a method for modifying a carbon electrode for a liquid flow battery, the method comprising loading iron-based alloy powder onto the carbon electrode by ultrasonic vibration; heating the carbon electrode loaded with the iron-based alloy powder by an induction coil and cooling it to room temperature to obtain a modified carbon electrode;

[0008] wherein the iron-based alloy has the formula Fe a C b B c Si d Cu e Ni f Mo g Cr h Mn i, a represents the atomic percentage of iron, b represents the atomic percentage of carbon, c represents the atomic percentage of boron, d represents the atomic percentage of silicon, e represents the atomic percentage of copper, f represents the atomic percentage of nickel, g represents the atomic percentage of molybdenum, h represents the atomic percentage of chromium, and i represents the atomic percentage of manganese, a is in the range of 50-100, b, c and d are in the range of 0-10 and b, c and d are not 0 at the same time, e, f, g, h and i are in the range of 0-50 and e, f, g, h and i are not 0 at the same time;

[0009] The melting point of the iron-based alloy powder is in the range of 1300° C. to 1400° C.;

[0010] The particle size of the iron-based alloy powder is in the range of 100 nm to 1000 nm.

[0011] In one embodiment, the iron-based alloy is selected from Fe 67.8 C 0.2 Cr 18 Ni 10 Mn 2 Si、Fe 65 Cr 17 Ni 12 Mn 2 Mo 2.5 SiCu 0.2 C 0.3 , Fe 77.8 Cr 15 Mo 3 Ni 2 Bc 0.2 , Fe 85.5 Cr 12.5 MnSi 0.5 C 0.5 One or more of .

[0012] In one embodiment, the carbon-based electrode material is glassy carbon, carbon paper, graphite felt or carbon felt.

[0013] In one embodiment, the ultrasonic vibration time is 8-24h.

[0014] In one embodiment, the frequency of the induction coil is in the range of 1 KHz-20 KHz, and / or the power of the induction coil is in the range of 100 kW-1000 kW.

[0015] In one embodiment, the heating lasts for 0.1-2 seconds.

[0016] In another aspect, the present application provides a carbon-based electrode for a liquid flow battery, wherein the carbon-based electrode is modified by the above method.

[0017] In one embodiment, the contact angle of the carbon-based electrode is in the range of 0°-30°.

[0018] On the other hand, the present application provides a liquid flow battery, comprising the above-mentioned carbon-based electrode.

[0019] The present application uses ultrasonic vibration to uniformly and efficiently load iron-based alloy powder onto carbon-based electrodes such as carbon felt, which is easy to operate and low in cost, and is conducive to large-scale production and preparation. Moreover, the use of ultrasonic vibration can make the iron-based alloy powder fill the inner and outer surfaces of carbon-based electrodes such as carbon felt as evenly as possible.

[0020] The present application adopts induction heating to heat only the iron-based alloy powder without heating the carbon electrode, which has little effect on the carbon felt and can quickly heat the iron-based alloy powder, which is conducive to large-scale production; moreover, by adopting induction heating, the iron-based alloy powder is melted and firmly loaded on the carbon electrode such as carbon felt, and more pore structures are formed inside and outside the carbon felt, thereby increasing the specific surface area of ​​the carbon felt, which is about 10 times higher than the specific surface area of ​​the original carbon felt.

[0021] After the carbon-based electrode modified by the modification method of the present application is applied to a liquid flow battery stack structure, such as an all-vanadium liquid flow battery stack structure, it exhibits excellent stability during battery operation. After 500 charge and discharge cycles, the electrode not only has no obvious morphological changes, but also has excellent electrical properties; for example, after 500 cycles, 240 mA / cm 2 The voltage efficiency at the current density can still be maintained above 86%.

[0022] The modification method of the present application is simple and easy to implement, and significantly improves the conductivity and stability of carbon electrodes. It is not only applicable to all-vanadium liquid flow batteries, but can also be extended to other types of liquid flow battery systems, such as zinc-bromine liquid flow batteries.

[0023] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0025] Figure 1 A diagram showing the appearance of an original carbon felt electrode provided according to an embodiment of the present disclosure;

[0026] Figure 2A and Figure 2B are graphs showing cyclic voltammetry curves of the positive electrode and the negative electrode of the modified carbon felt electrode and the original carbon felt electrode provided according to an embodiment of the present disclosure, respectively; and

[0027] Figure 3 The modified carbon felt electrode and the original carbon felt electrode provided according to an embodiment of the present disclosure are shown in Figure 1. 2 and 240mA / cm 2 Plot of voltage efficiency at current density. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present application more clear, the embodiments of the present application are described in detail below. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily without conflict.

[0029] The following embodiments use carbon felt as an example of a carbon electrode and select an all-vanadium liquid flow battery for illustration, but do not limit the application of carbon electrodes in other liquid flow batteries.

[0030] Unless otherwise specified, the materials used in the following examples are commercially available.

[0031] Example 1

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

[0033] Fe 77.8 Cr 15 Mo 3 Ni 2 Bc 0.2 The iron-based alloy powder and the original carbon felt were placed in a mold and ultrasonically vibrated for 12 hours to make the Fe 78 Cr 15 Mo 3 Ni 2 Bc 0.3 The iron-based alloy powder is loaded onto the original carbon felt; the carbon felt loaded with the iron-based alloy powder is heated by an induction coil, the frequency of the induction coil is 1000 Hz, the power of the induction coil is 1000 kW, and the heating lasts for 1 second; and the modified carbon felt electrode is obtained after natural cooling to room temperature.

[0034] Performance Testing

[0035] The hydrophilicity of the modified carbon felt electrode and the original carbon felt electrode of Example 1 was tested. The results showed that the contact angle of the original carbon felt was 120°, which was poor in hydrophilicity; while the contact angle of the modified carbon felt electrode prepared in Example 1 was 0°, which was excellent in hydrophilicity, and excellent hydrophilicity was one of the basic requirements for electrode materials of all-vanadium redox flow batteries.

[0036] The modified carbon felt electrode and the original carbon felt electrode of Example 1 were tested for electrochemical performance in an all-vanadium liquid flow battery. The modified carbon felt electrode and the original carbon felt electrode of Example 1 were used as working electrodes, respectively, and a three-electrode electrolytic cell was composed of a platinum sheet as a counter electrode and a saturated calomel electrode as a reference electrode. Cyclic voltammetry scanning experiments were performed to obtain cyclic voltammetry curves of the modified carbon felt electrode and the original carbon felt electrode of Example 1. The results are as follows: Figure 2A and 2B As shown. Figure 2A and Figure 2B It can be seen that the carbon felt electrode modified by this method has the smallest redox peak difference and the largest peak current, showing superior electrochemical activity compared with the original carbon felt; the modified carbon felt electrode has a higher electrochemical activity for the positive electrode reaction (V 5+ / V 4+ ) and negative electrode reaction (V 2+ / V 3+ ) have good electrochemical activity. This further demonstrates that the carbon-based electrodes modified by the modification method of the present application are universal and extensible for improving the electrochemical reaction activity of all-vanadium redox flow batteries.

[0037] The modified carbon felt electrode and the original carbon felt electrode of Example 1 were used as positive and negative electrodes to assemble the all-vanadium redox flow battery stack, and 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. 2 and 240mA / cm 2 The constant current charge and discharge test was carried out under the current density, and the results were as follows Figure 3 As shown. Figure 3 It can be seen that the flow battery comprising the modified carbon felt electrode of Example 1 has a higher voltage efficiency at two different current densities compared to the original carbon felt electrode. Figure 3 It also shows that the modified electrode of the present application has an 2 The voltage efficiency value at current density remains almost unchanged with the increase of charge and discharge cycles, while the original carbon felt electrode is 2 The voltage efficiency value under current density gradually decreases with the increase in the number of charge and discharge cycles, which shows that the stability of the carbon electrode modified by the modification method of the present application is significantly better than that of the original carbon felt electrode.

[0038] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Those skilled in the art can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for modifying a carbon electrode for a flow battery, characterized in that: The method comprises: loading iron-based alloy powder onto a carbon-based electrode by ultrasonic vibration; heating the carbon-based electrode loaded with the iron-based alloy powder by an induction coil and cooling it to room temperature, thereby obtaining a modified carbon-based electrode; wherein the iron-based alloy has the formula Fe a C b B c Si d Cu e Ni f Mo g Cr h Mn i , a represents the atomic percentage of iron, b represents the atomic percentage of carbon, c represents the atomic percentage of boron, d represents the atomic percentage of silicon, e represents the atomic percentage of copper, f represents the atomic percentage of nickel, g represents the atomic percentage of molybdenum, h represents the atomic percentage of chromium, and i represents the atomic percentage of manganese, a is in the range of 50-100, b, c and d are in the range of 0-10 and b, c and d are not 0 at the same time, e, f, g, h and i are in the range of 0-50 and e, f, g, h and i are not 0 at the same time; The melting point of the iron-based alloy powder is in the range of 1300°C-1400°C; The particle size of the iron-based alloy powder is in the range of 100nm-1000nm; The ultrasonic vibration time is 8-24h; The frequency of the induction coil is in the range of 1 KHz-20 KHz, and / or the power of the induction coil is in the range of 100 kW-1000 kW; The heating lasts for 0.1-2 seconds.

2. The method according to claim 1, characterized in that The iron-based alloy is selected from Fe 65 Cr 17 Ni 12 Mn2Mo 2.5 SiCu 0.2 C 0.3 , Fe 77.8 Cr 15 Mo3Ni2SiBC 0.2 and Fe 85.5 Cr 12.5 MnSi 0.5 C 0.5 One or more of .

3. The method according to claim 1, characterized in that The material of the carbon-based electrode is glassy carbon, carbon paper, graphite felt or carbon felt.

4. A carbon electrode for a flow battery, characterized in that: The carbon-based electrode is modified by the method according to any one of claims 1-3.

5. The carbon-based electrode according to claim 4, characterized in that: The contact angle of the carbon-based electrode is in the range of 0°-30°.

6. A liquid flow battery, characterized in that: It comprises the carbon-based electrode according to claim 4 or 5.

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