Structured electrode and preparation method thereof, structured electrode assembly and preparation method thereof, and flow battery
By designing structured electrodes in a vanadium redox flow battery and assembling and compressing alternating regions with bipolar plates, the problem of uneven electrolyte distribution was solved, thus improving the battery's energy efficiency.
Patent Information
- Application Number
- CN202410584269.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-11
- Publication Date
- 2025-11-18
AI Technical Summary
In existing vanadium redox flow batteries, the simple pore structure of the carbon felt electrode leads to uneven electrolyte distribution, increases concentration polarization, and reduces battery efficiency.
The structured electrode is designed with alternating first and second regions on its main surface. The first region has a low volume density and high porosity, while the second region has a high volume density and low porosity. It is then assembled and compressed with bipolar plates to form corresponding portions of the plate grooves and plate ridges, thereby achieving uniform volume density and porosity of the battery assembly.
It improves the uniformity of electrolyte flow field distribution in the electrode, reduces concentration polarization, and enhances the energy efficiency of flow batteries.
Smart Images
Figure CN120978091A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a flow battery, in particular, to a structured electrode and a preparation method thereof, a structured electrode assembly and a preparation method thereof, and a flow battery. BACKGROUND
[0002] Flow energy storage battery is a large-scale electrochemical energy storage technology, which has the advantages of high energy conversion efficiency, flexible system design, large storage capacity, free site selection, deep discharge, safety and environmental protection, low maintenance cost, etc. compared with other energy storage technologies, and can be widely used in renewable energy power generation storage, emergency power supply system, standby power station and peak load shifting of power system, etc. As one of the key components of the flow battery, the electrode material affects the ohmic polarization, concentration polarization and electrochemical polarization of the battery, thereby affecting the working current density and energy efficiency of the battery.
[0003] At present, the electrode material commonly used in all-vanadium flow battery is carbon paper or carbon felt, and the porosity and pore structure of the carbon paper or carbon felt directly affect the transmission rate and electrochemical catalytic activity of the active material at the electrode interface. The carbon felt used in the traditional flow-through flow battery electrode has a single pore structure. After the battery is assembled, the ridge part of the bipolar plate flow channel is compressed, and the bulk density is large, so a large amount of electrolyte tends to flow away from the plate flow channel, and the electrolyte flow rate in the dense carbon felt part of the flow channel ridge is slow, which makes the electrolyte in the electrode unevenly distributed, the battery concentration polarization increases, and the electrode active area utilization rate is low, thereby reducing the battery efficiency. SUMMARY
[0004] The purpose of the present disclosure is to provide a structured electrode and a preparation method thereof, a structured electrode assembly and a preparation method thereof, and a flow battery, the first region and the second region of the structured electrode have a specific bulk density and porosity, and when they are assembled and compressed with the corresponding bipolar plate, a structured electrode assembly can be prepared, and the bulk density and porosity of the plate ridge and the corresponding part of the structured electrode in the assembly are uniform, so that the electrolyte flow field in the structured electrode is more evenly distributed, the battery concentration polarization is reduced, and the electrode and electrolyte utilization rate is high.
[0005] In order to achieve the above-mentioned purpose, the first aspect of the present disclosure provides a structured electrode, the main surface of the structured electrode has a first region and a second region, the first region and the second region are alternately distributed; the bulk density of the second region is greater than the bulk density of the first region, and the porosity of the second region is less than the porosity of the first region; the thickness of the first region and the second region is not the same, or the thickness of the first region and the second region is the same.
[0006] Optionally, the second region of the structured electrode has a bulk density of 0.06-0.87 g / cm 3 , and a porosity of 40-90%; the first region has a bulk density of 0.05-0.70 g / cm 3 , and a porosity of 92-96%.
[0007] Optionally, the structured electrode has a body thickness d2 of 0.05-6 mm, the first region has a width l2 of 0.5-3 mm, the second region has a width j2 of 0.5-3 mm, and the thickness difference i2 between the first region and the second region is -3 to 3 mm, preferably -2.4 to 2.4 mm, more preferably -1 to 1 mm, and further preferably -0.6 to 0.6 mm.
[0008] Optionally, the structured electrode comprises one or more of a structured carbon felt, a structured carbon cloth, and a structured carbon paper, and preferably is a structured carbon felt; and the material of the structured electrode is selected from one or more of polyacrylonitrile, viscose-based, and pitch-based, and preferably is polyacrylonitrile.
[0009] The second aspect of the present disclosure provides a method for preparing a structured electrode, comprising:
[0010] (1) first needling raw fiber to obtain a raw felt;
[0011] (2) regionally second needling a main surface of the raw felt to form a second needled felt in which first regions and second regions are alternately distributed; wherein the first regions are not subjected to the second needling, and the second regions are subjected to the second needling;
[0012] (3) carbonizing and graphitizing the second needled felt to form a structured electrode.
[0013] Optionally, in step (2), the raw felt has a bulk density of 0.05-0.70 g / cm 3 , and the second needling has a density of 20-100 needles / cm 2 ; and the method further comprises: before the second needling in step (2), etching the raw felt by an etching process to form an etched felt; the etched region corresponds to the first region, and the etched width is l2; or the etched region corresponds to the second region, and the etched width is j2; and then the etched felt is subjected to the second needling; preferably, the etching depth i3 is 0-3 mm, preferably 0-2.4 mm, more preferably 0-1 mm, and further preferably 0-0.6 mm.
[0014] The third aspect of the present disclosure provides a structured electrode assembly, comprising a structured electrode and a bipolar plate in contact with the structured electrode; one side of the bipolar plate has a groove structure, the groove structure comprises bipolar plate grooves and bipolar plate ridges which are alternately distributed; the structured electrode comprises bipolar plate groove corresponding parts and bipolar plate ridge fitting parts which are alternately distributed, the bipolar plate groove corresponding parts match the bipolar plate grooves, and the bipolar plate ridge fitting parts match the bipolar plate ridges; the volume density of the bipolar plate groove corresponding parts is 95-105% of the volume density of the bipolar plate ridge fitting parts, and the porosity of the bipolar plate groove corresponding parts is 95-105% of the porosity of the bipolar plate ridge fitting parts.
[0015] Optionally, the depth i4 at which the bipolar plate groove corresponding parts of the structured electrode are embedded in the bipolar plate grooves is 0-100%, preferably 0-60%, of the depth i1 of the bipolar plate grooves.
[0016] The fourth aspect of the present disclosure provides a method for preparing a structured electrode assembly, comprising: superimposing a structured electrode and a main surface of a bipolar plate, and then compressing the obtained combination in a direction perpendicular to the main surface; the structured electrode is the structured electrode described in the first aspect of the present disclosure; wherein the second region of the structured electrode matches the bipolar plate grooves, and forms bipolar plate groove corresponding parts after compression, and the first region of the structured electrode matches the bipolar plate ridges, and forms bipolar plate ridge fitting parts after compression.
[0017] The fifth aspect of the present disclosure provides a flow battery, comprising a structured positive electrode assembly, a separator and a structured negative electrode assembly, the structured positive electrode assembly and the structured negative electrode assembly are the structured electrode assembly described in the third aspect of the present disclosure.
[0018] Through the above technical solutions, the present disclosure provides a structured electrode and a preparation method thereof, a structured electrode assembly and a preparation method thereof, and a flow battery. The first region and the second region of the structured electrode are alternately distributed, and have specific volume density and porosity. After the structured electrode is assembled and compressed with a bipolar plate, a structured electrode assembly can be prepared. The volume density and the porosity of the bipolar plate groove corresponding parts and the bipolar plate ridge fitting parts of the structured electrode in the assembly are uniform, so that the flow field distribution of the electrolyte in the structured electrode is more uniform, the concentration polarization of the battery is reduced, and the utilization rate of the electrode and the electrolyte is high.
[0019] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments section. BRIEF DESCRIPTION OF DRAWINGS
[0020] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and together with the following specific embodiments, serve to explain the present disclosure but do not constitute a limitation thereof. In the drawings:
[0021] Figure 1 is a schematic diagram of a structured electrode and a corresponding bipolar plate in one embodiment of the present disclosure;
[0022] Figure 2 is a schematic diagram of a groove structure of a bipolar plate in one embodiment of the present disclosure;
[0023] Figure 3 is a schematic diagram of a structured electrode in one embodiment of the present disclosure;
[0024] Figure 4 is a schematic diagram of a structured electrode A and a structured electrode assembly prepared in Example 1 of the present disclosure;
[0025] Figure 5 is a schematic diagram of a structured electrode B and a structured electrode assembly prepared in Example 2 of the present disclosure;
[0026] Figure 6 is a schematic diagram of a structured electrode C and a structured electrode assembly prepared in Example 3 of the present disclosure;
[0027] Figure 7 is a schematic diagram of a structured electrode D and a structured electrode assembly prepared in Example 4 of the present disclosure;
[0028] Figure 8 is a schematic diagram of a common electrode and a comparative structured electrode assembly prepared in Comparative Example 1 of the present disclosure.
[0029] Explanation of Reference Signs
[0030] 1 bipolar plate 2 plate groove 3 plate ridge
[0031] 4 structured electrode 5 second region 6 first region DETAILED DESCRIPTION
[0032] The specific embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present disclosure, and are not intended to limit the present disclosure.
[0033] A structured electrode is provided in the first aspect of the present disclosure, the structured electrode has a first region and a second region on a main surface thereof, the first region and the second region are alternately distributed with intervals; the volume density of the second region is greater than the volume density of the first region, and the porosity of the second region is less than the porosity of the first region; the thickness of the first region is not the same as the thickness of the second region, or the thickness of the first region is the same as the thickness of the second region.
[0034] The structured electrode provided by the present disclosure has a relatively small thickness, a relatively large length and width, and a main surface with regions of different bulk densities and porosities alternately arranged at intervals, as shown in Figure 1 and Figure 3 wherein the second region 5 has a larger bulk density and a smaller porosity, and the first region 6 has a smaller bulk density and a larger porosity. After the structured electrode of the present disclosure is assembled with a bipolar plate and compressed, a structured electrode assembly with a uniform bulk density and porosity of the whole electrode can be obtained, so as to reduce the flow resistance of the electrolyte in the structured electrode, increase the uniformity of the distribution of the electrolyte in the structured electrode, reduce the concentration polarization of the battery, and finally improve the energy efficiency of the flow battery.
[0035] The present disclosure does not limit the thickness of the first region and the second region. In one embodiment, the thickness of the first region is not equal to the thickness of the second region, for example, the thickness of the first region is smaller than the thickness of the second region, in which case the first region is a groove and the second region is a protrusion, as shown in Figures 4-5 Alternatively, the thickness of the first region is greater than the thickness of the second region, in which case the first region is a protrusion and the second region is a groove, as shown in Figure 7 In another embodiment, the thickness of the first region is equal to the thickness of the second region, and the structured electrode does not have obvious protrusions and grooves, as shown in Figure 6
[0036] In one embodiment of the present disclosure, the bulk density of the second region of the structured electrode is 0.06-0.87 g / cm 3 , and the porosity is 40-90%; the bulk density of the first region is 0.05-0.70 g / cm 3 , and the porosity is 92-96%. In a preferred embodiment, the bulk density of the second region is 105-230%, preferably 110-150%, of the bulk density of the first region; and the porosity of the second region is 40-93%, preferably 80-90%, of the porosity of the first region. In the above embodiment, the second region and the first region with the preferred bulk density and porosity are selected, which is beneficial to obtain a structured electrode assembly with a uniform bulk density and porosity of the whole electrode, and further reduce the flow resistance of the electrolyte in the electrode assembly.
[0037] In one embodiment of the present disclosure, the thickness d2 of the body of the structured electrode is 0.05-6 mm, the width l2 of the first region is 0.5-3 mm, the width j2 of the second region is 0.5-3 mm, and the thickness difference i2 between the first region and the second region is -3 to 3 mm, preferably -2.4 to 2.4 mm, more preferably -1 to 1 mm, and further preferably -0.6 to 0.6 mm.
[0038] In the present disclosure, the bulk thickness d2 of the structured electrode refers to the distance from the thinnest region on the main surface of the structured electrode to the secondary surface of the structured electrode, for example, when the thickness of the first region is less than the thickness of the second region, the thickness of the first region is the bulk thickness of the structured electrode; when the thickness of the first region is greater than the thickness of the second region, the thickness of the second region is the bulk thickness of the structured electrode; when the thickness of the first region is equal to the thickness of the second region, the thickness of the first region or the thickness of the second region can be the bulk thickness of the structured electrode.
[0039] The thickness difference i2 of the first region refers to the difference between the thickness of the first region and the thickness of the second region, i.e. i2 = thickness of the first region - thickness of the second region, wherein i2 can be positive, can be 0, or can be negative, for example, i2 is -3 to 3 mm, preferably -2.4 to 2.4 mm, more preferably -1 to 1 mm, and further preferably -0.6 to 0.6 mm.
[0040] When i2 is negative, for example -3 mm ≤ i2 < 0 mm, it indicates that the thickness of the first region is less than the thickness of the second region; when i2 is positive, for example 0 mm < i2 ≤ 3 mm, it indicates that the thickness of the first region is greater than the thickness of the second region; when i2 = 0 mm, it indicates that the thickness of the first region is equal to the thickness of the second region.
[0041] In an embodiment of the present disclosure, the structured electrode comprises one or more of a structured carbon felt, a structured carbon cloth, and a structured carbon paper, and is preferably a structured carbon felt. In an embodiment, the material of the structured electrode is selected from one or more of polyacrylonitrile, viscose-based, and pitch-based, and is preferably polyacrylonitrile.
[0042] The second aspect of the present disclosure provides a method for preparing a structured electrode, the method comprising:
[0043] (1) first needling the raw fiber to obtain a raw felt;
[0044] (2) regionally performing second needling on the main surface of the raw felt to form a second needled felt in which the first region and the second region are alternately distributed; wherein the first region is not subjected to the second needling, and the second region is subjected to the second needling;
[0045] (3) performing carbonization treatment and graphitization treatment on the second needled felt to form a structured electrode.
[0046] The present disclosure can form multiple regions with different bulk densities and porosities by second needling the original felt in different regions. In a specific embodiment, the second needling is alternately performed on the main surface of the original felt. The structure of the region after the second needling is more compact and has a smaller porosity, i.e., a second region with a larger bulk density and a smaller porosity is formed. The structure of the region without the second needling is looser and has a larger porosity, i.e., a first region with a smaller bulk density and a larger porosity is formed. The first region and the second region are alternately distributed. In the above preparation process, no etching process is used, and the structured electrode formed does not have obvious protruding parts and recessed parts, as shown in Figure 6 .
[0047] In an embodiment of the present disclosure, in step (2), the bulk density of the original felt is 0.05-0.70 g / cm 3 , and the density of the second needling is 20-100 needles / cm 2 . In step (3), the temperature of the carbonization treatment is 800-1600℃, and the temperature of the graphitization treatment is 2000-3000℃. In the above embodiment, the use of the preferred second needling conditions can further increase the bulk density of the second region and reduce the porosity thereof.
[0048] In an embodiment of the present disclosure, the method further comprises: before the second needling in step (2), etching the original felt by using an etching process to form an etched felt; the etched region corresponds to the first region, and the etching width is l2; or the etched region corresponds to the second region, and the etching width is j2; and then the etched felt is subjected to the second needling. Preferably, the etching depth i3 is 0-3 mm, preferably 0-2.4 mm, more preferably 0-1 mm, and further preferably 0-0.6 mm.
[0049] In the present disclosure, the original felt is etched by using an etching process, which can form protruding parts and recessed parts on the original felt. In an embodiment, the etched region corresponds to the first region, and the etching width is l2. The recessed part formed corresponds to the first region after the second needling, and the protruding part formed corresponds to the second region after the second needling, as shown in Figures 4-5 . In another embodiment, the etched region corresponds to the second region, and the etching width is j2. The protruding part formed corresponds to the first region after the second needling, and the recessed part formed corresponds to the second region after the second needling, as shown in Figure 7 .
[0050] In the detailed description, the original felt can be secondarily needled according to the groove structure of the corresponding bipolar plate. The secondly needled area is the part of the original felt corresponding to the pole groove of the bipolar plate, and the etched area is the part of the original felt corresponding to the pole ridge of the bipolar plate. The width of the etched area is equal to the width of the pole ridge, and the recessed part corresponds to the first area after the second needling, and the raised part corresponds to the second area after the second needling, as shown in FIG. 8A. In another embodiment, the etched area is the part of the original felt corresponding to the pole groove of the bipolar plate, and the width of the etched area is equal to the width of the pole groove. The raised part corresponds to the first area after the second needling, and the recessed part corresponds to the second area after the second needling, as shown in FIG. 8B. Preferably, the etching depth i3 can be 0-100% of the pole groove depth i1, and the etching depth i3 is preferably 0-80% of the pole groove depth i1, for example, i3 is 0-3 mm, and preferably 0-2.4 mm. Figures 4-5 Figure 7
[0051] In an embodiment of the present disclosure, the etching process includes electric spark etching and / or laser etching. The method of electric spark etching can be as follows: 1) place the original felt on the xy-axis movable processing table, and adjust the distance between the original felt and the electrode wire for electric spark processing to be 1.5 mm, wherein the electrode wire is a copper wire with a diameter of 0.5 mm; 2) set the etching voltage to 0.6-0.8 kV through the server, and start the electric spark processing by translating the processing table at a fixed speed and in a fixed direction to etch the flow channel on the original felt; and 3) clean the surface after etching to obtain the etched felt with a groove structure.
[0052] The raw fiber of the present disclosure is commercially purchased and is a known product in the art. In an embodiment, the diameter of the raw fiber is 10 μm, and the type of the raw fiber can be selected from pitch-based raw fiber, polyacrylonitrile raw fiber (PAN raw fiber), and viscose-based raw fiber, and the polyacrylonitrile raw fiber is preferred.
[0053] The third aspect of the present disclosure provides a structured electrode assembly, which comprises a structured electrode and a bipolar plate in contact with the structured electrode. One side of the bipolar plate has a groove structure, and the groove structure comprises pole grooves and pole ridges alternately distributed. The structured electrode comprises pole groove corresponding parts and pole ridge fitting parts alternately distributed. The pole groove corresponding parts match the pole grooves, and the pole ridge fitting parts match the pole ridges. The bulk density of the pole groove corresponding parts is 95-105% of the bulk density of the pole ridge fitting parts, and the porosity of the pole groove corresponding parts is 95-105% of the porosity of the pole ridge fitting parts.
[0054] In one embodiment, the depth i4 of the portion of the structured electrode plate recess corresponding part embedded in the structured electrode plate recess of the bipolar plate is 0-100%, preferably 0-60% of the depth i1 of the structured electrode plate recess.
[0055] The structured electrode assembly provided by the present disclosure is composed of a structured electrode and a bipolar plate in contact with the structured electrode, wherein the portion of the structured electrode embedded in the structured electrode plate recess of the bipolar plate is defined as the structured electrode plate recess corresponding part, and the portion of the structured electrode closely fitted with the structured electrode plate ridge of the bipolar plate is defined as the structured electrode plate ridge fitted part. The volume density and porosity of the structured electrode plate recess corresponding part and the structured electrode plate ridge fitted part are uniform, which is conducive to reducing the flow resistance of the electrolyte in the electrode and making the flow field distribution of the electrolyte in the electrode more uniform. In one embodiment, the structured electrode in the structured electrode assembly is formed by the structured electrode of the first aspect of the present disclosure combined with the bipolar plate and compressed. Due to compression, the volume density and porosity of the first region and the second region of the structured electrode of the first aspect change, and finally form the structured electrode in the structured electrode assembly of the third aspect of the present disclosure, wherein the structured electrode plate ridge fitted part of the structured electrode is formed by the first region after compression, the structured electrode plate recess corresponding part is formed by the second region after compression, and the volume density and porosity of the structured electrode plate ridge fitted part and the structured electrode plate recess corresponding part are uniform.
[0056] In one embodiment, the volume density of the structured electrode plate recess corresponding part is the same as the volume density of the structured electrode plate ridge fitted part, and the porosity of the structured electrode plate recess corresponding part is the same as the porosity of the structured electrode plate ridge fitted part. In the above embodiment, it is conducive to further increasing the uniformity of the electrolyte distribution in the electrode, reducing the concentration polarization of the battery, and ultimately improving the energy efficiency of the flow battery.
[0057] The structured electrode plate recess corresponding part in the present disclosure can be embedded or not embedded in the structured electrode plate recess. In the specific embodiment, the depth i4 of the structured electrode plate recess corresponding part embedded in the structured electrode plate recess can be 0 mm, 0.3 mm, 0.7 mm, 1 mm, 1.5 mm, 2.5 mm or 3 mm, or within a numerical range between any two of them, for example, it can be 0-3 mm, preferably 0-1.8 mm.
[0058] The fourth aspect of the present disclosure provides a method for preparing a structured electrode assembly, comprising: superimposing a structured electrode and a main surface of a bipolar plate opposite to each other, and then compressing the obtained combination in a direction perpendicular to the main surface; the structured electrode is the structured electrode of the first aspect of the present disclosure; wherein the second region of the structured electrode matches the structured electrode plate recess of the bipolar plate, and forms the structured electrode plate recess corresponding part after compression, and the first region of the structured electrode matches the structured electrode plate ridge of the bipolar plate, and forms the structured electrode plate ridge fitted part after compression.
[0059] The bipolar plate and the structured electrode of the present disclosure correspond to each other, that is, the second region of the structured electrode corresponds to the bipolar plate groove, and the first region of the structured electrode corresponds to the bipolar plate ridge, and the obtained combination is compressed, so that the second region with a larger volume density and a smaller porosity can be embedded in the bipolar plate groove, and the first region with a smaller volume density and a larger porosity can be closely attached to the bipolar plate ridge, the volume density of the closely attached part can be increased, and the porosity can be reduced, so that the finally obtained structured electrode assembly has the characteristics that the volume density and the porosity of the entire structured electrode are consistent.
[0060] In an embodiment, the compression rate can be 20-60%, so that the second region of the structured electrode is embedded in the bipolar plate groove in whole or in part, for example, the second region of the structured electrode is embedded in the bipolar plate groove in whole after compression, the bipolar plate groove is completely filled, and it can be considered that the invasion degree of the second region is 100%, as shown in Figure 4 ; or the second region of the structured electrode is embedded in the bipolar plate groove in part after compression, the bipolar plate groove is partially filled, and it can be considered that the invasion degree of the second region is less than 100%, for example, the invasion degree of the second region can be 67% or 33%, as shown in Figures 5-6 ; or the second region of the structured electrode is not embedded in the bipolar plate groove at all after compression, the bipolar plate groove is not filled, and it can be considered that the invasion degree of the second region is 0%, as shown in Figure 7 . The compression rate represents the compression degree of the body thickness of the structured electrode, and the calculation method is (the body thickness of the structured electrode before compression-the body thickness of the structured electrode after compression) / the body thickness of the structured electrode before compression*100%.
[0061] In the present disclosure, the second region of the structured electrode matches the bipolar plate groove means that the number, position and width of the second region and the bipolar plate groove are the same, and the depth of the bipolar plate groove is greater than or equal to the thickness of the second region protruding from the first region, so that the bipolar plate groove can completely accommodate the second region; the first region of the structured electrode matches the bipolar plate ridge means that the number, position and width of the first region and the bipolar plate ridge are the same, and the first region and the bipolar plate ridge are attached to each other. In an embodiment, the bipolar plate has a groove structure as shown in Figure 1 and Figure 2 , wherein 1 is a bipolar plate, 2 is a bipolar plate groove, and 3 is a bipolar plate ridge. The structured electrode has a structure matching the groove structure of the bipolar plate, as shown in Figure 1 and Figure 3 , wherein 4 is a structured electrode, 5 is a second region matching the bipolar plate groove, and 6 is a first region matching the bipolar plate ridge.
[0062] In one embodiment of the present disclosure, the body thickness d1 of the bipolar plate is 0.01-5 mm, the width l1 of the plate ridge is 0.5-3 mm; the depth i1 of the plate groove is 0-3 mm, and the width j1 of the plate groove is 0.5-3 mm.
[0063] In the present disclosure, the body thickness d1 of the plate ridge refers to the distance from the raised plane of the plate ridge to the bottom plane of the bipolar plate, and the depth i1 of the plate groove refers to the distance from the raised plane of the plate ridge to the recessed plane of the plate groove. The depth i1 of the plate groove of the present disclosure can be 0 or a positive value. When i1 = 0 mm, it indicates that the thicknesses of the plate ridge and the plate groove are equal, and the bipolar plate does not have obvious raised and recessed parts. When 0 mm < i1 ≤ 3 mm, it indicates that the thicknesses of the plate ridge and the plate groove are not equal, the plate ridge is the raised part, and the plate groove is the recessed part. At this time, the body thickness of the bipolar plate should be greater than the depth of the plate groove.
[0064] The groove structure of the bipolar plate of the present disclosure is not limited, and in the specific embodiments, the groove structure comprises one or more of a serpentine groove structure, a parallel groove structure, an interdigital groove structure, a spiral groove structure, a grid groove structure and a bionic groove structure. In a preferred embodiment, the groove structure of the bipolar plate is a serpentine groove structure, as shown in FIG. 1, and the structured electrode has a matching serpentine groove structure, as shown in FIG. 2. Figure 2 Figure 3
[0065] The fifth aspect of the present disclosure provides a flow battery, which comprises a structured positive electrode assembly, a separator and a structured negative electrode assembly, and the structured positive electrode assembly and the structured negative electrode assembly are the structured electrode assembly of the third aspect of the present disclosure.
[0066] When the structured electrode assembly provided by the present disclosure is used in a flow battery, the flow field distribution of the electrolyte in the electrode is more uniform, which is beneficial to increase the uniformity of the distribution of the electrolyte in the structured electrode, reduce the concentration polarization of the battery, and ultimately improve the energy efficiency of the flow battery. The flow battery provided by the present disclosure has excellent electrochemical activity and high battery efficiency.
[0067] The present disclosure will be further illustrated by examples, but the present disclosure is not limited in any way by the examples. Unless otherwise specified, the raw materials used in the examples and comparative examples of the present disclosure are all purchased through commercial channels and are pure reagents.
[0068] Example 1
[0069] The structured electrode is prepared by the following steps:
[0070] (1) first needling of polyacrylonitrile precursor (PAN precursor fiber, diameter 10 μm) to obtain a raw felt; the first needling density is 100 needles / cm 2 ;
[0071] (2) according to the groove structure of the corresponding bipolar plate, the raw felt is etched by using an electric spark etching process, the etched area is the part corresponding to the bipolar plate ridge of the raw felt, the etching depth i3 is 0.8 mm, and the width is 1.6 mm, so as to form an etched felt; the etched felt is second needled, the second needling area is the part corresponding to the bipolar plate groove of the etched felt, and a second needled felt is formed; wherein the bulk density of the raw felt is 0.08 g / cm 3 , and the second needling density is 30 needles / cm 2 ;
[0072] The bipolar plate has a serpentine groove structure, and the serpentine groove structure has alternately distributed plate grooves and plate ridges; the plate body thickness d1 is 3 mm, the plate ridge width l1 is 1.6 mm, the plate groove depth i1 is 1 mm, and the plate groove width j1 is 2 mm, as shown in Figure 4 ;
[0073] The electric spark etching method comprises the following steps: 1) placing the raw felt on an xy-axis movable processing table, and adjusting the distance between the raw felt and the electrode wire used for electric spark processing to 1 mm, wherein the electrode wire is a copper wire with a diameter of 0.4 mm; 2) setting the etching voltage to 0.6-0.8 kV through a server, and starting the electric spark processing to translate the processing table at a fixed speed and in a fixed direction, so as to etch flow channels on the raw felt; and 3) cleaning the surface after etching to obtain an etched felt with a groove structure;
[0074] (3) carbonization treatment and graphitization treatment are performed on the second needled felt, the carbonization treatment temperature is 950 DEG C, the graphitization treatment temperature is 2500 DEG C, and a structured electrode A is formed, as shown in Figure 4 .
[0075] The structured electrode A presents a plate-shaped structure with relatively small thickness and relatively large length and width, and the main surface has alternately distributed strip-shaped first and second regions, wherein the strip-shaped first region is a recessed part with a thickness of 2.5 mm, that is, the body thickness d2 of the structured electrode A is 2.5 mm, the width l2 of the first region is 1.6 mm, and the strip-shaped second region is a raised part with a width j2 of 2 mm; the thickness difference i2 of the first region and the second region is -0.8 mm;
[0076] The bulk density of the second region is 0.091 g / cm 3, the porosity of the first region is 85%; the bulk density of the second region is 114% of the bulk density of the first region, and the porosity of the second region is 89% of the porosity of the first region. 3 , the porosity of the first region is 85%; the bulk density of the second region is 114% of the bulk density of the first region, and the porosity of the second region is 89% of the porosity of the first region.
[0077] The structured electrode assembly is prepared by the following steps:
[0078] S1, the groove structure of the bipolar plate is superimposed on the main surface of the structured electrode A, that is, the plate groove of the bipolar plate is superimposed on the second region of the structured electrode A, and the plate ridge of the bipolar plate is superimposed on the first region of the structured electrode A, then the obtained combination is compressed in the direction perpendicular to the main surface, the compression rate is 20%, so that the intrusion degree of the second region is 100%, to obtain a structured electrode assembly, the structure of which is shown in Figure 4 .
[0079] The structured electrode assembly includes a bipolar plate with a groove structure and a structured electrode in contact with the groove structure, the groove structure includes alternating plate grooves and plate ridges, and the structured electrode includes alternating plate groove corresponding parts and plate ridge fitting parts, wherein the plate groove corresponding part matches the plate groove, and the plate ridge fitting part matches the plate ridge; the bulk density of the plate groove corresponding part is the same as that of the plate ridge fitting part, both being 0.10 g / cm 3 ; the porosity of the plate groove corresponding part is the same as that of the plate ridge fitting part, both being 82%; the depth i4 of the plate groove corresponding part embedded in the plate groove is 1 mm, which is 100% of the depth i1 of the plate groove.
[0080] Example 2
[0081] The same as example 1, the difference is only that the etching depth i3 in step (2) is 0.4 mm, so that the thickness difference i2 between the first region and the second region of the structured electrode B formed is -0.4 mm; in step S1, the compression rate is 20%, so that the intrusion degree of the second region is 67%, to obtain a structured electrode assembly, the structure of which is shown in Figure 5 .
[0082] The bulk density of the plate groove corresponding part in the structured electrode assembly is the same as that of the plate ridge fitting part, both being 0.10 g / cm 3 ; the porosity of the plate groove corresponding part is the same as that of the plate ridge fitting part, both being 82%; the depth i4 of the plate groove corresponding part embedded in the plate groove is 0.67 mm, which is 67% of the depth i1 of the plate groove.
[0083] Example 3
[0084] The same as example 1, the difference is only that the step (2) of the electric spark etching process is not carried out, that is, the etching depth i3 is 0 mm, and according to the groove structure of the corresponding bipolar plate, the second needling is directly carried out on the original felt, and the obtained structured electrode C does not have obvious protruding parts and recessed parts, that is, the thickness difference i2 between the first region and the second region is 0 mm. In step S1, the compression ratio is 20%, so that the intrusion degree of the second region is 33%, and the structured electrode assembly is obtained, and the structure is as shown in Figure 6 .
[0085] The volume density of the bipolar plate groove corresponding part in the structured electrode assembly is the same as that of the bipolar plate ridge fitting part, both of which are 0.10 g / cm 3 , the porosity of the bipolar plate groove corresponding part is the same as that of the bipolar plate ridge fitting part, both of which are 82%; the depth i4 of the bipolar plate groove corresponding part embedded in the bipolar plate groove is 0.33 mm, that is, 33% of the depth i1 of the bipolar plate groove.
[0086] Example 4
[0087] The same as example 1, the difference is only that the etched region in step (2) is the part corresponding to the bipolar plate groove of the original felt, and the etching depth i3 is 0.5 mm, and the formed structured electrode D is as shown in Figure 7 , wherein the protruding part is the first region, the recessed part is the second region, and the thickness difference i2 between the first region and the second region is 0.5 mm. In step S1, the compression ratio is 20%, so that the intrusion degree of the second region is 0%, and the structured electrode assembly is obtained, and the structure is as shown in Figure 7 .
[0088] The volume density of the bipolar plate groove corresponding part in the structured electrode assembly is the same as that of the bipolar plate ridge fitting part, both of which are 0.10 g / cm 3 , the porosity of the bipolar plate groove corresponding part is the same as that of the bipolar plate ridge fitting part, both of which are 82%; the depth i4 of the bipolar plate groove corresponding part embedded in the bipolar plate groove is 0 mm, that is, 0% of the depth i1 of the bipolar plate groove.
[0089] Comparative Example 1
[0090] The same as example 1, the difference is only that steps (1)-(3) are not carried out, but a common electrode (the structure is as shown in Figure 8 ) without protrusions and recesses and with consistent overall volume density and porosity is overlapped with the groove structure of the bipolar plate, and then compressed, and the compression ratio is 20%, so that the intrusion degree of the common electrode is 20%, and the comparative structured electrode assembly is obtained, and the structure is as shown in Figure 8 .
[0091] The volume density of the plate groove corresponding part of the comparative structured electrode assembly is 0.10 g / cm 3 The volume density of the plate ridge fitting part is 0.11 g / cm 3 The porosity of the plate groove corresponding part is 82%, and the porosity of the plate ridge fitting part is 75%; the depth i4 of the plate groove corresponding part embedded in the plate groove is 0.33 mm, which is 33% of the depth i1 of the plate groove.
[0092] Test example
[0093] The structured electrode assemblies prepared from Examples 1-4 and Comparative Example 1 were subjected to electrolyte flow uniformity testing, which used a finite element simulation method. The specific method was as follows: 1. Establish a three-dimensional model of the structured electrode; 2. Divide the grid and perform grid independence test; 3. Input the boundary conditions of the simulation, wherein the electrolyte inlet flow rate was 0.1 m / s, and the electrolyte viscosity coefficient was 0.005; 4. Simulation calculation; 5. Obtain flow field velocity data and calculate velocity variance. The simulation results are shown in Table 1:
[0094] Table 1
[0095]
[0096] As can be seen from the data in Table 1 above, the structured electrode assemblies prepared from Examples 1-4 using the structured electrode of the present disclosure have a smaller velocity variance when the electrolyte flows in the structured electrode during simulation fitting, indicating that the uniformity of electrolyte distribution in the structured electrode is significantly improved, which is beneficial to reducing the concentration polarization of the battery and ultimately improving the energy efficiency of the flow battery. The comparative structured electrode assembly prepared from Comparative Example 1 does not use the structured electrode of the present disclosure, but uses a common electrode. When the comparative structured electrode assembly is used for simulation fitting, the velocity variance of the electrolyte flowing in the common electrode is larger, and the flow uniformity of the electrolyte is poorer.
[0097] The preferred embodiments of the present disclosure are described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to the specific details in the above-described embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.
[0098] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.
[0099] In addition, various different embodiments of the present disclosure can also be combined in any appropriate manner, as long as they do not deviate from the idea of the present disclosure, and they should also be considered as disclosed by the present disclosure.
Claims
1. A structured electrode, characterized in that, The structured electrode has a first region and a second region on its main surface, which are distributed alternately. The volume density of the second region is greater than that of the first region, and the porosity of the second region is less than that of the first region. The thickness of the first region is different from that of the second region, or the thickness of the first region is the same as that of the second region.
2. The structured electrode according to claim 1, characterized in that, The volume density of the second region of the structured electrode is 0.06–0.87 g / cm³. 3 The porosity is 40–90%; the bulk density of the first region is 0.05–0.70 g / cm³. 3 The porosity is 92-96%.
3. The structured electrode according to claim 1, characterized in that, The structured electrode has a body thickness d2 of 0.05 to 6 mm, a width l2 of 0.5 to 3 mm, a width j2 of 0.5 to 3 mm, and a thickness difference i2 between the first and second regions of -3 to 3 mm, preferably -2.4 to 2.4 mm, more preferably -1 to 1 mm, and even more preferably -0.6 to 0.6 mm.
4. The structured electrode according to claim 1, characterized in that, The structured electrode includes one or more of structured carbon felt, structured carbon cloth and structured carbon paper, preferably structured carbon felt; The structured electrode is made of one or more of polyacrylonitrile, adhesive-based, and bitumen-based materials, preferably polyacrylonitrile.
5. A method for preparing a structured electrode, characterized in that, include: (1) The raw silk fibers are needle-punched for the first time to obtain the original felt body; (2) The main surface of the original felt body is divided into regions for second needle punching to form a second needle punched felt body with alternating first and second regions; wherein the first region is not subjected to the second needle punching, and the second region is subjected to the second needle punching; (3) The second needle-punched felt is subjected to carbonization and graphitization treatment to form a structured electrode.
6. The method according to claim 5, characterized in that, In step (2), the bulk density of the original felt body is 0.05–0.70 g / cm³. 3 The density of the second acupuncture point is 20-100 needles / cm². 2 ; The method further includes: before the second needle punching in step (2), etching process is used to etch the original felt body to form an etched felt body; the etched area corresponds to the first area and the etching width is l2; or, the etched area corresponds to the second area and the etching width is j2; then the etched felt body is subjected to the second needle punching. Preferably, the etching depth i3 is 0-3 mm, more preferably 0-2.4 mm, more preferably 0-1 mm, and even more preferably 0-0.6 mm.
7. A structured electrode assembly, characterized in that, The device includes a structured electrode and a bipolar plate that contacts and engages with the structured electrode; one side of the bipolar plate has a groove structure, the groove structure including alternately distributed electrode grooves and electrode ridges; the structured electrode includes alternately distributed electrode groove corresponding portions and electrode ridge fitting portions, the electrode groove corresponding portions matching the electrode grooves, and the electrode ridge fitting portions matching the electrode ridges; The bulk density of the portion corresponding to the groove of the electrode plate is 95-105% of the bulk density of the portion attached to the ridge of the electrode plate, and the porosity of the portion corresponding to the groove of the electrode plate is 95-105% of the porosity of the portion attached to the ridge of the electrode plate.
8. The structured electrode assembly according to claim 7, characterized in that, The depth i4 of the electrode groove of the structured electrode embedded in the electrode groove of the bipolar plate is 0 to 100% of the depth i1 of the electrode groove, preferably 0 to 60%.
9. A method for preparing a structured electrode assembly, characterized in that, include: The structured electrode is stacked opposite to the main surface of the bipolar plate, and then the resulting assembly is compressed in a direction perpendicular to the main surface; the structured electrode is the structured electrode according to any one of claims 1 to 4; The second region of the structured electrode matches the plate groove of the bipolar plate, and after compression, it forms a corresponding part of the plate groove. The first region of the structured electrode matches the plate ridge of the bipolar plate, and after compression, it forms a plate ridge fitting part.
10. A flow battery, characterized in that, The flow battery includes a structured positive electrode assembly, a separator, and a structured negative electrode assembly, wherein the structured positive electrode assembly and the structured negative electrode assembly are the structured electrode assemblies described in any one of claims 7 to 8.