Composite electrode for flow battery, preparation method of composite electrode and flow battery

Abstract

The invention provides a composite electrode for a flow battery, a preparation method of the composite electrode and the flow battery. The composite electrode comprises a first carbon cloth layer, a second carbon cloth layer and a carbon felt layer or a graphite felt layer located between the first carbon cloth layer and the second carbon cloth layer, the sintering track line is formed by mutually melting and connecting carbon fibers in the first carbon cloth layer, the carbon felt layer or the graphite felt layer and the second carbon cloth layer through carbon-carbon covalent bonds generated by laser induction. The overall energy efficiency of the flow battery system comprising the composite electrode is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flow battery, and in particular to a composite electrode for flow battery and a preparation method thereof. BACKGROUND

[0002] Flow battery is an electrochemical energy storage device that stores electricity through electrolyte. At present, the electrode of flow battery stack usually adopts carbon felt, graphite felt and other carbon materials, which has the characteristics of good electrical conductivity, large specific surface area, high porosity, low cost and good mechanical stability. However, the internal pore structure of the current carbon felt electrode is random and disordered, the electrolyte flow path is chaotic, and flow dead zones and short circuit flows are easily generated, resulting in large mass transfer resistance and high pumping energy consumption. Moreover, the carbon felt is prone to fiber shedding and pressure creep during long-term operation, resulting in structural collapse and performance degradation.

[0003] Therefore, there is a need for an improved electrode for flow battery and a preparation method thereof. SUMMARY

[0004] 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.

[0005] In one aspect, a composite electrode for flow battery is provided, which includes a first carbon cloth layer, a second carbon cloth layer, and a carbon felt layer or a graphite felt layer between the first carbon cloth layer and the second carbon cloth layer, wherein the composite electrode has a plurality of sintering track lines formed by carbon fibers in the first carbon cloth layer, the carbon felt layer or graphite felt layer, and the second carbon cloth layer being fusedly connected to each other via laser-induced carbon-carbon covalent bonds.

[0006] In an exemplary embodiment, the composite electrode has a plurality of parallelogram grid units composed of the plurality of sintering track lines.

[0007] In an exemplary embodiment, the first carbon cloth layer has a thickness of 0.3-0.5mm and an area density of 100-150g / m 2 .

[0008] In an exemplary embodiment, the second carbon cloth layer has a thickness of 0.3-0.5mm and an area density of 100-150g / m 2 .

[0009] In an exemplary embodiment, the carbon felt layer or graphite felt layer has a thickness of 1.5-3.0mm, an area density of 350-450g / m 2 , and a porosity of >90%.

[0010] In an exemplary embodiment, the first carbon cloth layer and the second carbon cloth layer have the same or different thicknesses; and the first carbon cloth layer and the second carbon cloth layer have the same or different areal densities.

[0011] In another aspect, a method for preparing the composite electrode is provided, comprising the following steps: 1) sequentially placing the first carbon cloth layer, the carbon felt layer or graphite felt layer, and the second carbon cloth layer to form a stacked structure; and 2) scanning the stacked structure with a laser under inert gas or nitrogen to form a plurality of sintering tracks in the composite electrode, the sintering tracks being formed by the carbon fibers in the first carbon cloth layer, the carbon felt layer or graphite felt layer, and the second carbon cloth layer being fusedly connected to each other via carbon-carbon covalent bonds induced by the laser.

[0012] In an exemplary embodiment, the laser is a fiber laser, the laser power is 50-200 W, the scanning speed is 100-1000 mm / s, and the spot diameter is 50-150 μm.

[0013] In an exemplary embodiment, the scanning of the stacked structure with the laser comprises multiple scans of the laser beam along a first direction to form a plurality of first sintering tracks, and multiple scans of the laser beam along a second direction intersecting the first direction to form a plurality of second sintering tracks, thereby forming a plurality of sintering tracks in the composite electrode, in which the first sintering tracks and the second sintering tracks are connected to each other.

[0014] In an exemplary embodiment, the scanning of the stacked structure with the laser comprises multiple scans of the laser beam along a first direction to form a plurality of first sintering tracks, and multiple scans of the laser beam along a second direction intersecting the first direction to form a plurality of second sintering tracks, thereby forming a plurality of parallelogram grid units in the composite electrode, in which the first sintering tracks and the second sintering tracks are connected to each other.

[0015] In an exemplary embodiment, the parallelogram grid units have a size of 3x3 mm to 5x5 mm.

[0016] In an exemplary embodiment, the parallelogram grid units are rhombic grid units.

[0017] In an exemplary embodiment, the scanning line width of the laser is 200-500 μm.

[0018] In another aspect, the present application provides a composite electrode for a liquid flow battery, which is prepared by the above method.

[0019] In yet another aspect, the application provides a flow battery comprising the composite electrode.

[0020] In an exemplary embodiment, the flow battery is one of a vanadium flow battery or a iron-chromium flow battery.

[0021] The application ingeniously realizes the integrated integration of the flow channel and the electrode by laser sintering to form a regular quadrilateral such as a rhombus grid in the composite electrode. The unsintered area naturally forms an efficient flow channel under pressure, which can strongly guide the uniform distribution of electrolyte, completely eliminate dead zones, and significantly reduce flow resistance. This greatly reduces the pumping loss of the battery system, improves the overall energy efficiency, and the excellent mass transfer capacity supports the stable operation of the battery at a higher current density, thereby releasing a higher power density.

[0022] The application sintering three layers of carbon materials by laser sintering, the carbon fibers in the three layers of carbon materials are connected to each other through the carbon-carbon covalent bond induced by laser, forming a three-dimensional integrated conductive reinforcing framework throughout the composite electrode.

[0023] The three-layer structure of the composite electrode of the application realizes the complementary advantages of functional materials. The first carbon cloth layer and the second carbon cloth layer provide a high-catalytic-activity surface rich in edge carbon and defect sites, and the middle carbon felt layer or graphite felt layer contributes a large three-dimensional reaction space and liquid storage capacity.

[0024] In the application, the carbon-carbon sintering lines formed by laser sintering are not only firmly connected, but also have excellent electrical conductivity, ensuring efficient transmission of current within the electrode and between interfaces, thereby significantly enhancing the reaction kinetics of the electrode and significantly reducing the electrochemical polarization, resulting in higher voltage efficiency and coulombic efficiency. At the same time, the current distribution on the entire electrode surface is more uniform, avoiding local overload or uneven reaction.

[0025] The application melts the three layers of materials into a solid whole by laser sintering, with extremely high mechanical strength and excellent resistance to tearing and fiber shedding. More importantly, the laser welding points have excellent compression creep resistance, which can always maintain the stability of the pore structure and thickness of the electrode under the long-term assembly pressure of the stack, thereby greatly extending the service life of the electrode and improving the reliability and durability of the entire stack.

[0026] The surface carbon cloth of the composite electrode of the application has a relatively flat surface, and when it contacts the bipolar plate, the contact area is larger and the contact resistance is smaller. The internal sintering connection ensures efficient current collection and conduction, further optimizing the interface performance.

[0027] The preparation process of the composite electrode of the present application does not introduce any foreign substances, and the connection points are all carbon materials, which are perfectly compatible with strong acid and strong oxidizing vanadium electrolyte, fundamentally eliminating the risks of corrosion, pollution and short circuit, and ensuring the chemical stability and safety of long-term operation of the battery.

[0028] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent from the description, or can be learned by practice of the present application. Other advantages of the present application can be realized and attained by means of the instrumentalities and combinations particularly pointed out in the description and appended claims. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings are included to provide an understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the technical scheme of the present application, and do not constitute a limitation on the technical scheme of the present application.

[0030] Figure 1 The pressure drop-flow curves of the composite electrode provided according to the embodiment 1 of the present application and the traditional carbon felt electrode are shown; Figure 2A and Figure 2B The graphs showing the cyclic voltammetry curves of the positive electrode and the negative electrode of the composite electrode and the traditional carbon felt electrode provided according to the embodiment 1 of the present application, respectively; and Figure 3 The graphs showing the voltage efficiency of the composite electrode and the traditional carbon felt electrode provided according to the embodiment 1 of the present application at 160 mA / cm 2 and 240 mA / cm 2 current density are shown. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme 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 in the present application and the features in the embodiments can be combined with each other arbitrarily without conflict.

[0032] The materials used in the following embodiments are all commercially available if not specifically mentioned.

[0033] Embodiment 1 The first carbon cloth layer, the carbon felt layer and the second carbon cloth layer are stacked in sequence to form a laminated structure (i.e. sandwich structure); the thickness of the first carbon cloth layer and the second carbon cloth layer is 0.5 mm, and the area density is 100-150 g / m 2 ; the thickness of the middle carbon felt layer is 3.5 mm, and the area density is 0.1 g / cm 2 , and the porosity is 95%.

[0034] A fiber laser with a wavelength of 1064 nm was used to scan the stacked structure under nitrogen atmosphere protection. The laser power was set to 100 W, the scanning speed to 200 mm / s, the spot diameter to 100 μm, and the scanning linewidth to 200 μm.

[0035] The laser beam scans multiple times along a first direction to form multiple parallel first sintering trajectory lines; the laser beam scans multiple times along a second direction that intersects with the first direction to form multiple parallel second sintering trajectory lines, forming multiple 3×3 mm rhomboid grid units in the composite electrode by connecting the first sintering trajectory lines and the second sintering trajectory lines.

[0036] This indicates that laser scanning effectively couples energy to the three layers of carbon material, forming strong and dense carbon interconnects along the scanning trajectory, thereby achieving integrated interlayer connection.

[0037] Performance testing Pressure drop-flow rate tests were performed on the composite electrode prepared in Example 1 of this application and a traditional carbon felt electrode. The results are as follows: Figure 1 As shown. From Figure 1 As can be seen, throughout the entire flow range, the pressure drop of the composite electrode prepared by Example 1 of this application (red curve) is consistently significantly lower than that of the conventional carbon felt electrode (black curve). This difference widens dramatically with increasing flow rate. For example, at a flow rate of 10 L / min: the pressure drop of the conventional carbon felt electrode is as high as 45 kPa, while the pressure drop of the composite electrode of Example 1 is only 8 kPa, representing a reduction of approximately 82% in pressure drop.

[0038] The electrochemical performance of the composite electrode prepared in Example 1 of this application and the conventional carbon felt electrode were characterized in an all-vanadium redox flow electrolyzer. First, a three-electrode electrolyzer system consisting of the composite electrode prepared in Example 1 and the conventional carbon felt electrode as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode was used to perform cyclic voltammetry scans, thereby obtaining the cyclic voltammetry curves of the composite electrode prepared in Example 1 and the conventional carbon felt electrode, respectively. The results... Figure 2A and 2B As shown. By Figure 2A and Figure 2B As can be seen, compared with traditional carbon felt electrodes, the composite electrode prepared by this method has the smallest redox peak position difference and the largest peak current, exhibiting superior electrochemical activity compared with traditional carbon felt electrodes. The prepared composite electrode also shows better performance for the positive electrode reaction (Vo). 5+ / V 4+ ) and negative electrode reaction (V 2+ / V 3+Both exhibit good electrochemical activity. This further demonstrates the universality and scalability of the composite electrode prepared by this method for improving the electrochemical reaction activity of vanadium redox flow batteries.

[0039] The composite electrode prepared in Example 1 and a conventional carbon felt electrode were used as positive and negative electrodes to assemble a 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 traditional carbon felt electrode, the flow battery containing the composite electrode of Example 1 exhibits higher voltage efficiency at both different current densities. Furthermore, Figure 3 The composite electrode of this application is also shown to operate at 240 mA / cm². 2 The voltage efficiency at current density remains almost constant with increasing charge-discharge cycle count, while the original carbon felt electrode achieves efficiency at 240 mA / cm². 2 The voltage efficiency at current density gradually decreases with increasing charge-discharge cycle count, indicating that the stability of the composite electrode in this application is significantly better than that of the traditional carbon felt electrode.

[0040] 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 composite electrode for a flow battery, characterized in that, The composite electrode includes a first carbon cloth layer, a second carbon cloth layer, and a carbon felt layer or a graphite felt layer located between the first carbon cloth layer and the second carbon cloth layer. The composite electrode has multiple sintering trajectory lines, which are formed by the fusion connection of carbon fibers in the first carbon cloth layer, the carbon felt layer or the graphite felt layer, and the second carbon cloth layer through laser-induced carbon-carbon covalent bonds.

2. The composite electrode according to claim 1, characterized in that, The composite electrode has multiple parallelogram grid units formed by the multiple sintering trajectory lines.

3. The composite electrode according to claim 1, characterized in that, The thickness of the first carbon cloth layer is 0.3-0.5 mm, and the areal density is 100-150 g / m³. 2 The second carbon cloth layer has a thickness of 0.3-0.5 mm and a surface density of 100-150 g / m³. 2 ; and / or, The thickness of the carbon felt layer or graphite felt layer is 1.5-3.0 mm, and the areal density is 350-450 g / m³. 2 Porosity > 90%.

4. The composite electrode according to any one of claims 1-3, characterized in that, The thicknesses of the first carbon cloth layer and the second carbon cloth layer may be the same or different; the areal densities of the first carbon cloth layer and the second carbon cloth layer may be the same or different.

5. A method for preparing the composite electrode according to any one of claims 1-4, characterized in that, Includes the following steps: 1) The first carbon cloth layer, the carbon felt layer or graphite felt layer, and the second carbon cloth layer are sequentially placed to form a laminated structure; and 2) Under inert gas or nitrogen, a laser is used to scan the stacked structure to form multiple sintering trajectory lines in the composite electrode. The sintering trajectory lines are formed by the carbon fibers in the first carbon cloth layer, the carbon felt layer or graphite felt layer and the second carbon cloth layer being fused together by carbon-carbon covalent bonds generated by laser.

6. The method according to claim 5, characterized in that, The laser is a fiber laser with a power of 50-200W, a scanning speed of 100-1000mm / s, and a spot diameter of 50-150μm.

7. The method according to claim 5, characterized in that, Scanning the stacked structure with a laser includes scanning the laser beam multiple times along a first direction to form multiple first sintering trajectory lines; scanning the laser beam multiple times along a second direction intersecting the first direction to form multiple second sintering trajectory lines; and forming multiple sintering trajectory lines in the composite electrode where the first and second sintering trajectory lines are interconnected; and / or, The laser scanning linewidth is 200-500 μm.

8. The method according to claim 5, characterized in that, The laser scanning of the stacked structure includes multiple scans along a first direction to form multiple parallel first sintering trajectory lines; multiple scans along a second direction intersecting the first direction to form multiple parallel second sintering trajectory lines; and the formation of multiple parallelogram grid units in the composite electrode formed by connecting the first sintering trajectory lines and the second sintering trajectory lines. Optionally, the size of the parallelogram grid cell is 3×3 mm to 5×5 mm; and / or, The laser scanning linewidth is 200-500 μm.

9. A composite electrode for a flow battery, characterized in that, The composite electrode is prepared by the method described in any one of claims 5-8.

10. A flow battery, characterized in that, The composite electrode includes any one of claims 1-4 or the composite electrode of claim 9, wherein the flow battery is a vanadium redox flow battery or an iron-chromium redox flow battery.

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