Electrode-bipolar plate composite assembly and method of making same, stack, and flow battery

Abstract

The application provides an electrode and bipolar plate composite assembly, a preparation method thereof, a stack and a flow battery. The electrode and bipolar plate composite assembly comprises a bipolar plate and an electrode layer, and the electrode layer is arranged on at least one side surface of the bipolar plate. The electrode layer comprises activated carbon particles, graphene particles and a porous carbon binder. The particle size of the activated carbon particles is 200-500 mu m, the particle size of the graphene particles is 20-50 mu m, and the mass ratio of the activated carbon particles, the graphene particles and the porous carbon binder is (98-99.7):(0.4-3):(0.1-1). The electrode and bipolar plate composite assembly is beneficial to improving the energy efficiency of the flow battery.

Description

Technical Field

[0001] This application relates to the field of flow battery technology, and in particular to an electrode and bipolar plate composite assembly and its preparation method, a fuel cell stack, and a flow battery. Background Technology

[0002] A flow battery is a novel type of rechargeable battery that stores energy in an electrolyte solution. Energy storage and release are achieved through the flow of the electrolyte within the battery and electrode reactions. A flow battery system mainly consists of a stack system, an electrolyte system, a control system, and auxiliary systems. The stack system primarily comprises bipolar plates, electrodes, an ion exchange membrane, an electrode frame / sealing gasket, end plates, and current collectors.

[0003] With the rapid development of flow battery technology, higher requirements have been placed on the energy efficiency of flow batteries. Therefore, how to further improve the energy efficiency of flow batteries has become one of the important research directions in this field. Summary of the Invention

[0004] Based on this, this application provides an electrode and bipolar plate composite component and its preparation method, a fuel cell stack, and a flow battery. This electrode and bipolar plate composite component is beneficial to improving the energy efficiency of the flow battery.

[0005] The technical solution proposed in this application is as follows:

[0006] According to a first aspect of this application, an electrode-bipolar plate composite assembly is provided, comprising a bipolar plate and an electrode layer, wherein the electrode layer is disposed on at least one surface of the bipolar plate; the electrode layer comprises activated carbon particles, graphene particles and a porous carbon binder, wherein the average particle size of the activated carbon particles is 200 μm to 500 μm, the average particle size of the graphene particles is 20 μm to 50 μm, and the mass ratio of the activated carbon particles, the graphene particles and the porous carbon binder is (98 to 99.7):(0.4 to 3):(0.1 to 1).

[0007] In some embodiments, the specific surface area of ​​the activated carbon particles is 800 m². 2 / g~1200m 2 / g.

[0008] In some embodiments, the activated carbon particles are activated carbon particles that have undergone high-temperature air activation modification, concentrated sulfuric acid boiling activation modification, or supported metal catalyst activation modification.

[0009] In some embodiments, the electrical conductivity of the graphene particles is 4000 S / cm to 5000 S / cm.

[0010] In some embodiments, the thickness of the electrode layer on one side of the bipolar plate is 0.2mm-0.5mm.

[0011] In some embodiments, the compaction density of the electrode layer is 0.6g / cm 3 ~1.0g / cm 3 .

[0012] According to a second aspect of the present application, a method for preparing the electrode and bipolar plate composite assembly of the first aspect of the present application is provided, comprising the following steps:

[0013] providing a bipolar plate;

[0014] applying an electrode paste on at least one side surface of the bipolar plate to form an electrode paste layer; the electrode paste comprising the activated carbon particles, the graphene particles and a polymer binder;

[0015] drying the electrode paste layer and performing carbonization treatment to form the electrode layer.

[0016] According to a third aspect of the present application, a stack is provided, comprising the electrode and bipolar plate composite assembly of the first aspect of the present application.

[0017] In some embodiments, the stack further comprises an electrode frame, which is arranged on the bipolar plate and surrounds the periphery of the electrode layer, and flow channels are arranged in the electrode frame and the bipolar plate, and a filter screen is arranged at the flow channel opening of the electrode frame and / or the bipolar plate, and the pore size of the filter screen is smaller than the particle size of the activated carbon particles and the graphene particles.

[0018] According to a fourth aspect of the present application, a flow battery is provided, comprising the stack of the third aspect of the present application.

[0019] Compared with the prior art, the present application has at least the following beneficial effects:

[0020] The electrode and bipolar plate composite assembly of the present application uses activated carbon particles and graphene particles with specific content and particle size in the electrode layer; among them, the activated carbon particles with a particle size of 200μm-500μm and the graphene particles with a particle size of 20μm-50μm are matched by particle jointing, which is beneficial to form good electrolyte channels in the electrode layer and reduce the flow resistance of the electrolyte in the electrode layer; and the electrode layer has good electrical conductivity. By matching the activated carbon particles and graphene particles with the above particle size at a specific mass ratio, the electrode layer can have good catalytic activity and electrical conductivity at the same time, thereby effectively improving the energy efficiency of the flow battery.

[0021] And, by adjusting the mass ratio of the activated carbon particles and the graphene particles, the catalytic activity and the electrical conductivity of the electrode layer can be conveniently regulated, and the performance of the flow battery is further regulated. BRIEF DESCRIPTION OF DRAWINGS

[0022] For a better description and illustration of the embodiments or examples provided by the present application, one or more drawings can be referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any one of the disclosed applications, the presently described embodiments or examples, and the best mode of these applications presently understood. Moreover, the same reference numbers are used to represent the same components throughout the drawings. In the drawings:

[0023] Figure 1 Structure schematic diagram of the electrode and bipolar plate composite assembly of an embodiment of the present application.

[0024] Figure 2 Structure schematic diagram of the electrode and bipolar plate composite assembly of an embodiment of the present application. Figure 1 Top view of the electrode and bipolar plate composite assembly.

[0025] Explanation of reference signs:

[0026] 10, electrode and bipolar plate composite assembly; 11, bipolar plate; 12, electrode layer; 121, activated carbon particles; 122, graphene particles. DETAILED DESCRIPTION

[0027] The technical solutions of the present application will be described clearly and completely in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0028] "ranges" disclosed herein can be defined with endpoints by referencing the lower and upper limits, and the endpoints are inclusive and independently variable. Any range of values that has an endpoint can be expressed as comprising either the precise value that is the endpoint or the approximate value that is the endpoint. Unless otherwise stated, a range "a~b" wherein a and b are both real numbers indicates a range including all real combinations of "a" and "b" in the range from the lower value to the upper value inclusive. For example, a range of "0~5" indicates a range of values that includes any real number of values from the value "0" up to, and including, the value "5." In addition, when a parameter is stated as an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is stated as an integer selected from "2~10," it is equivalent to list the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0029] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specifically stated.

[0030] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment or implementation of the application. The appearances of the phrase that the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of other embodiments. It is explicitly contemplated that embodiments described herein can be combined with other embodiments. It is also understood that a reference to "an implementation" herein has a corresponding meaning.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0032] Traditional liquid flow battery electrode materials usually use carbon felt, such as polyacrylonitrile-based carbon felt. This kind of carbon felt electrode material has the disadvantages of low specific surface area, large electrolyte mass transfer resistance, insufficient reaction activity, and difficult adjustment of electrical conductivity and reaction activity due to the disordered accumulation of fibers, the tortuous pores, and the like, resulting in low energy efficiency of the liquid flow battery.

[0033] Specifically, first, due to graphitization, the carbon felt surface has strong chemical inertness and it is extremely difficult to form micropores, which makes it difficult to expand the specific surface area in the activation process, the specific surface area of the carbon felt is small, and the polarization resistance of the liquid flow battery is increased. Second, since the carbon felt is a kind of needle-punched non-woven fabric, the internal fibers are arranged in disorder, the porosity is low, the electrolyte flow is hindered, the flow resistance of the electrolyte is large, and the polarization resistance of the liquid flow battery is greatly increased. Third, the specific surface area of the carbon felt is small and the chemical inertness is strong, the effective group grafting sites are few or difficult to graft during the activation process, which results in insufficient activity of the carbon felt and increases the activation polarization of the liquid flow battery. Fourth, the existing carbon felt production process of the liquid flow battery is long, and the temperature and time are high during the activation process, and the electrical conductivity and reaction activity of the carbon felt electrode are difficult to precisely control.

[0034] For this purpose, please refer to Figure 1 and Figure 2 An embodiment of the present application provides an electrode and bipolar plate composite assembly 10, which comprises a bipolar plate 11 and an electrode layer 12, the electrode layer 12 being arranged on at least one side surface of the bipolar plate 11; the electrode layer 12 comprises activated carbon particles 121, graphene particles 122 and a porous carbon binder, the average particle size of the activated carbon particles 121 is 200-500 μm, the average particle size of the graphene particles 122 is 20-50 μm, and the mass ratio of the activated carbon particles 121, the graphene particles 122 and the porous carbon binder is (98-99.7):(0.4-3):(0.1-1).

[0035] The electrode and bipolar plate composite assembly 10 described above in the present application uses activated carbon particles 121 and graphene particles 122 with specific content and particle size to be matched in the electrode layer 12; wherein the activated carbon particles 121 with an average particle size of 200-500 μm and the graphene particles 122 with an average particle size of 20-50 μm are matched by particle jointing, which is beneficial to form good electrolyte channels in the electrode layer 12, reduce the flow resistance of the electrolyte in the electrode layer 12, and make the electrode layer 12 have good electrical conductivity. By matching the activated carbon particles 121 and the graphene particles 122 with the above particle size at a specific mass ratio, the electrode layer 12 can have good catalytic activity and electrical conductivity at the same time, thereby effectively improving the energy efficiency of the liquid flow battery. Furthermore, by adjusting the mass ratio of the activated carbon particles 121 and the graphene particles 122, the catalytic activity and electrical conductivity of the electrode layer 12 can be conveniently adjusted.

[0036] In the present application, the activated carbon particles 121 and the graphene particles 122 in the electrode layer 12 are mixed and overlapped with each other, and the porous carbon binder is located in the gaps between the activated carbon particles 121 and the graphene particles 122, thereby bonding the activated carbon particles 121 and the graphene particles 122, and bonding the electrode layer 12 to the bipolar plate 11. The porous carbon binder can be obtained by high-temperature carbonization of a polymer binder.

[0037] It should be noted that the particle size of the activated carbon particles 121 and the graphene particles 122 is the equivalent particle size of the particles. That is, when the particles are spherical, the particle size is the diameter of the spherical particles; when the particles are of other shapes (such as ellipsoidal or other irregular shapes), the particle size is the diameter of a spherical particle with the same volume as the particle.

[0038] It can be understood that the average particle size of the activated carbon particles 121 can be 200 μm, 220 μm, 250 μm, 280 μm, 300 μm, 320 μm, 350 μm, 380 μm, 400 μm, 420 μm, 450 μm, 480 μm, 500 μm, and any value within the range formed by any two of the above values; the average particle size of the graphene particles 122 can be 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, and any value within the range formed by any two of the above values.

[0039] In some embodiments, the porous carbon binder is obtained by high-temperature carbonization of polyvinyl alcohol.

[0040] In some embodiments, the specific surface area of the activated carbon particles 121 is 800 m 2 / g~1200 m 2 / g. The activated carbon particles 121 with the above specific surface area are beneficial to balance the resistivity and the active site density of the activated carbon particles 121, so that the activated carbon particles 121 have both low resistivity and high active site density, thereby being beneficial to make the electrode layer 12 have both good catalytic activity and conductivity, and being beneficial to improve the energy efficiency of the flow battery.

[0041] It can be understood that the specific surface area of the activated carbon particles 121 can be 800 m 2 / g, 820 m 2 / g, 850 m 2 / g, 880 m 2 / g, 900 m 2 / g, 920 m 2 / g, 950 m 2 / g, 980 m 2 / g, 1000 m2 / g, 1020 m 2 / g, 1050 m 2 / g, 1080 m 2 / g, 1100 m 2 / g, 1120 m 2 / g, 1150 m 2 / g, 1180 m 2 / g, 1200 m 2 / g, and any value formed in a range between any two of the above values.

[0042] In the present application, the specific surface area of the activated carbon particles 121 can be tested by using a conventional testing method in the art. Specifically, the specific surface area of the activated carbon particles 121 can be tested by using a low-temperature nitrogen adsorption-desorption method (BET method) according to GB / T 19587-2017.

[0043] In some embodiments, the activated carbon particles 121 are activated carbon particles 121 that are subjected to high-temperature air activation modification, concentrated sulfuric acid boiling activation modification, or metal catalyst loading activation modification. By using the activated carbon particles 121 subjected to the activation modification treatment, the electrochemical catalytic performance and the number of active sites of the activated carbon particles 121 can be improved, thereby increasing the redox activity of the flow battery electrode material and improving the energy efficiency of the flow battery.

[0044] In some specific examples, the activated carbon particles 121 are subjected to the activation modification treatment by using high-temperature air activation. Specifically, the activated carbon particles 121 are placed in a muffle furnace, and the heating rate is controlled to be 5°C / min. When the temperature reaches 550°C, the temperature is maintained for 5h. In this way, the electrochemical catalytic performance and the number of active sites of the activated carbon particles 121 can be effectively improved.

[0045] In some embodiments, the graphene particles 122 have an electrical conductivity of 4000 S / cm to 5000 S / cm. By using the graphene particles 122 having the above electrical conductivity in combination with the activated carbon particles 121, the overall electrical conductivity of the electrode layer 12 can be improved, the electrical conductivity of the electrode layer 12 can be improved, and thus the energy efficiency of the flow battery can be improved.

[0046] It can be appreciated that the electrical conductivity of the graphene particles 122 can be any value in the range of 4000 S / cm, 4050 S / cm, 4080 S / cm, 4100 S / cm, 4150 S / cm, 4180 S / cm, 4200 S / cm, 4250 S / cm, 4280 S / cm, 4300 S / cm, 4350 S / cm, 4380 S / cm, 4400 S / cm, 4450 S / cm, 4480 S / cm, 4500 S / cm, 4550 S / cm, 4580 S / cm, 4600 S / cm, 4650 S / cm, 4680 S / cm, 4700 S / cm, 4750 S / cm, 4780 S / cm, 4800 S / cm, 4850 S / cm, 4880 S / cm, 4900 S / cm, 4950 S / cm, 4980 S / cm, 5000 S / cm, and any range formed by any two of the above values.

[0047] In the present application, the electrical conductivity of the graphene particles 122 can be tested by using conventional methods in the art. Specifically, the four-probe method can be used to test the electrical conductivity of the graphene particles 122.

[0048] In some embodiments, the thickness of the single-sided electrode layer 12 on the bipolar plate 11 is 0.2 mm to 0.5 mm; and the compacted density of the electrode layer 12 is 0.6 g / cm 3 ~1.0 g / cm 3 Controlling the thickness and compacted density of the electrode layer 12 in the above ranges is beneficial to improving the energy efficiency of the flow battery.

[0049] It can be appreciated that the thickness of the single-sided electrode layer 12 can be any value in the range of 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0.3 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.4 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.5 mm, and any range formed by any two of the above values; and the compacted density of the electrode layer 12 can be any value in the range of 0.6 g / cm 3 , 0.65 g / cm 3 , 0.68 g / cm 3 , 0.7 g / cm 3 , 0.72 g / cm 3 , 0.8 g / cm 3 , 0.83 g / cm3 0.88 g / cm 3 0.9 g / cm 3 0.91 g / cm 3 0.95 g / cm 3 1.0 g / cm 3 and any numerical value within the range of any two of the above-listed values.

[0050] An embodiment of the present application provides a preparation method of the electrode and bipolar plate composite assembly 10, which comprises the following steps S100 to S300:

[0051] Step S100: providing a bipolar plate 11.

[0052] Step S200: applying an electrode slurry on at least one side surface of the bipolar plate 11 to form an electrode slurry layer; the electrode slurry comprises activated carbon particles 121, graphene particles 122 and a polymer binder.

[0053] Step S300: drying the electrode slurry layer and then placing it in a high-temperature furnace for carbonization treatment at 800°C under a nitrogen atmosphere for 4h, so as to carbonize the polymer binder to form a porous carbon binder, and the contact surface of the activated carbon particles 121 and the graphene particles 122 is sintered and fixed to form an electrode layer 12.

[0054] By the above method, the electrode and bipolar plate composite assembly 10 of the present application can be conveniently prepared. The bipolar plate 11 can be a conventional bipolar plate 11 in a flow battery. The polymer binder can be polyvinyl alcohol. The polyvinyl alcohol can be used as an emulsion stabilizer in the electrode slurry, so that the activated carbon particles 121 and the graphene particles 122 are uniformly dispersed in the slurry. After the electrode slurry layer is dried and solidified, the polyvinyl alcohol acts as a binder to bond the activated carbon particles 121 and the graphene particles 122, and to bond the electrode layer 12 to the bipolar plate 11. After high-temperature carbonization, the polyvinyl alcohol is carbonized to form a porous carbon binder, and the contact surface of the activated carbon particles 121 and the graphene particles 122 is sintered and fixed.

[0055] In some embodiments, the bipolar plate 11 is placed in an oven together with the electrode slurry layer for drying at 80°C for 2h.

[0056] An embodiment of the present application provides a stack (not shown in the figure) comprising the electrode and bipolar plate composite assembly 10 described above. It can be understood that the stack usually comprises one or more single cells connected in series. The single cell comprises two electrode and bipolar plate composite assemblies 10, one of which acts as a positive electrode and the other acts as a negative electrode.

[0057] In some embodiments, the stack further comprises an electrode frame (not shown) disposed on the bipolar plate 11 and surrounding the periphery of the electrode layer 12, the electrode frame and the bipolar plate 11 each having flow channels, and a filter screen having a pore size smaller than the particle size of the activated carbon particles 121 and the graphene particles 122 is disposed at the flow channel opening of the electrode frame and / or the bipolar plate 11.

[0058] By disposing the filter screen having a pore size smaller than the particle size of the activated carbon particles 121 and the graphene particles 122 at the flow channel opening of the electrode frame and / or the bipolar plate 11, the activated carbon particles 121 and the graphene particles 122 in the electrode layer 12 can be prevented from entering the electrolyte. Specifically, the filter screen can be a metal titanium screen.

[0059] Further, in addition to the electrode-bipolar plate composite assembly 10 and the electrode frame described above, the stack can further comprise an ion exchange membrane, a seal, an end plate, and the like conventional structural components. The ion exchange membrane is disposed between the two electrode-bipolar plate composite assemblies 10 of the single cell to prevent the mixing of active substances in the positive and negative electrolytes, and can allow specific ions to pass through to maintain charge balance. The seal is used to prevent the leakage of electrolyte and to prevent the entry of external air into the stack. The end plate is usually located at the outermost layer of the stack and is fixed by fastening bolts to tightly press the layered structure in the stack.

[0060] An embodiment of the present application provides a flow battery comprising the stack described above. By using the stack of the present application, the flow battery has a higher energy efficiency due to the use of the electrode-bipolar plate composite assembly 10 of the present application in the stack.

[0061] It can be understood that, in addition to the stack of the present application, the flow battery can further comprise an electrolyte storage tank, a circulating pump, a temperature control system, a state monitoring system, an electrical control system, a safety protection system, and the like conventional auxiliary systems.

[0062] The present application will be further described below in conjunction with specific examples and comparative examples, but should not be construed as limiting the scope of protection of the present application.

[0063] Example 1:

[0064] A single cell of a full vanadium flow battery comprises two electrode-bipolar plate composite assemblies, an electrode frame, and an ion exchange membrane. One of the two electrode-bipolar plate composite assemblies serves as a positive electrode, and the other serves as a negative electrode, and the ion exchange membrane is disposed between the two electrode-bipolar plate composite assemblies to separate the positive and negative electrodes.

[0065] The electrode and bipolar plate composite assembly is prepared by the following method: applying an electrode paste on one side surface of the bipolar plate to form an electrode paste layer; the electrode paste comprises activated carbon particles, graphene particles and polyvinyl alcohol; placing the bipolar plate with the electrode paste layer in an oven to dry at 80℃ for 2h; then carbonizing at 800℃ for 4h in a nitrogen atmosphere, carbonizing the polyvinyl alcohol to form a porous carbon binder, and at the same time, the contact surface of the activated carbon particles and the graphene particles is sintered and fixed, thereby forming an electrode layer.

[0066] In the electrode layer, the average particle size of the activated carbon particles is 350μm, the average particle size of the graphene particles is 35μm, and the mass ratio of the activated carbon particles, the graphene particles and the porous carbon binder is 98.5:1:0.5. The specific surface area of the activated carbon particles is 1000m 2 / g, and the activated carbon particles are activated carbon particles after high-temperature air activation modification treatment at 550℃ for 2h; the conductivity of the graphene particles is 4500S / cm. The thickness of the electrode layer is 0.3mm, and the compacted density is 0.65g / cm 3 .

[0067] Example 2:

[0068] This example is basically the same as Example 1, except that the average particle sizes of the activated carbon particles and the graphene particles in the electrode layer are different. In this example, the average particle size of the activated carbon particles is 200μm, and the average particle size of the graphene particles is 20μm; accordingly, the specific surface area of the activated carbon particles is 1120m 2 / g.

[0069] Example 3:

[0070] This example is basically the same as Example 1, except that the average particle sizes of the activated carbon particles and the graphene particles in the electrode layer are different. In this example, the average particle size of the activated carbon particles is 500μm, and the average particle size of the graphene particles is 50μm; accordingly, the specific surface area of the activated carbon particles is 986m 2 / g.

[0071] Example 4:

[0072] This example is basically the same as Example 1, except that the mass ratio of the activated carbon particles, the graphene particles and the porous carbon binder in the electrode layer is different. In this example, the mass ratio of the activated carbon particles, the graphene particles and the porous carbon binder is 99.5:0.4:0.1. The specific surface area of the activated carbon particles is 1120m 2 / g.

[0073] Example 5:

[0074] This example is basically the same as Example 1, except that the thickness of the electrode layer is 0.5 mm and the compacted density is 0.80 g / cm 3 . The specific surface area of the activated carbon particles is 1011m 2 / g.

[0075] Comparative Example 1

[0076] This comparative example is basically the same as Example 1, except that the average particle sizes of the activated carbon particles and the graphene particles in the electrode layer are different. In this comparative example, the average particle size of the activated carbon particles is 100 μm and the average particle size of the graphene particles is 10 μm; correspondingly, the specific surface area of the activated carbon particles is 1310m 2 / g.

[0077] Comparative Example 2

[0078] This comparative example is basically the same as Example 1, except that the average particle sizes of the activated carbon particles and the graphene particles in the electrode layer are different. In this comparative example, the average particle size of the activated carbon particles is 600 μm and the average particle size of the graphene particles is 60 μm; correspondingly, the specific surface area of the activated carbon particles is 936m 2 / g.

[0079] Comparative Example 3

[0080] This comparative example is basically the same as Example 1, except that the average particle sizes of the activated carbon particles and the graphene particles in the electrode layer are different. In this comparative example, the mass ratio of the activated carbon particles, the graphene particles and the binder is 93:5:2. The specific surface area of the activated carbon particles is 966m 2 / g.

[0081] Comparative Example 4

[0082] This comparative example is basically the same as Example 1, except that the electrode and bipolar plate composite assembly of the present application is not used, but a traditional carbon felt is used as the electrode material, which is compressed on the bipolar plate. The thickness of the carbon felt is 1.5 mm.

[0083] Test method

[0084] (1) Single cell energy efficiency test

[0085] Under the condition of a current density of 160 mA / cm 2 , the coulombic efficiency (CE), voltage efficiency (VE) and energy efficiency (EE) of the single cell are tested according to the method of NB / T 42081-2016 Performance Test Method for Single Cell of Vanadium Redox Flow Battery. Among them, the energy efficiency = coulombic efficiency x voltage efficiency; that is, EE = CE x VE.

[0086] The positive electrolyte used in the test has the following composition (mass percentage): water (H2O): 52%, sulfuric acid (H2SO4): 20%, vanadium sulfate (V2(SO4)3): 16%, vanadyl sulfate (VOSO4): 12%.

[0087] The negative electrolyte has the following composition (mass percentage): water (H2O): 52%, sulfuric acid (H2SO4): 20%, vanadium sulfate (V2(SO4)3): 16%, vanadyl sulfate (VOSO4): 12%.

[0088] The parameters and performance data of the single cells of the above examples and comparative examples are shown in Table 1. Among them, " / " represents the absence or no test.

[0089] Table 1

[0090]

[0091] As can be seen from Table 1, the single cells of the examples of the present application have high energy efficiency. In Comparative Examples 1-3, the particle size of the activated carbon particles, graphene particles or the mass ratio of the activated carbon particles, graphene particles and the porous carbon binder is not within the scope of the present application, and the energy efficiency of the single cells thereof decreases. In Comparative Example 4, a traditional carbon felt is used as an electrode material, and the energy efficiency of the single cell thereof is significantly reduced.

[0092] The technical features of the above-described examples can be combined in any manner. In order to make the description concise, all possible combinations of the technical features in the above examples are not described, however, as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present disclosure.

[0093] The above-described examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent of the present application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A composite assembly of an electrode and a bipolar plate, characterized in that, The device includes a bipolar plate and an electrode layer, wherein the electrode layer is disposed on at least one surface of the bipolar plate; the electrode layer includes activated carbon particles, graphene particles and a porous carbon binder, wherein the porous carbon binder is obtained by high-temperature carbonization of a polymer binder; the average particle size of the activated carbon particles is 200 μm to 500 μm, the average particle size of the graphene particles is 20 μm to 50 μm, and the mass ratio of the activated carbon particles, the graphene particles and the porous carbon binder is (98 to 99.7): (0.4 to 3): (0.1 to 1).

2. The electrode and bipolar plate composite assembly according to claim 1, characterized in that, The specific surface area of ​​the activated carbon particles is 800 m². 2 / g~1200m 2 / g.

3. The electrode and bipolar plate composite assembly according to claim 1, characterized in that, The activated carbon particles are activated carbon particles that have undergone high-temperature air activation modification, concentrated sulfuric acid boiling activation modification, or metal catalyst-supported activation modification.

4. The electrode and bipolar plate composite assembly according to claim 1, characterized in that, The electrical conductivity of the graphene particles is 4000 S / cm to 5000 S / cm.

5. The electrode and bipolar plate composite assembly according to claim 1, characterized in that, The thickness of the electrode layer on one side of the bipolar plate is 0.2 mm to 0.5 mm.

6. The electrode and bipolar plate composite assembly according to any one of claims 1 to 5, characterized in that, The compaction density of the electrode layer is 0.6 g / cm³. 3 ~1.0g / cm 3 .

7. A method for preparing an electrode and bipolar plate composite assembly according to any one of claims 1 to 6, characterized in that, Includes the following steps: Provide bipolar plates; An electrode slurry is applied to at least one surface of the bipolar plate to form an electrode slurry layer; the electrode slurry includes the activated carbon particles, the graphene particles, and a polymer binder; The electrode slurry layer is dried and carbonized to form the electrode layer.

8. A fuel cell stack, characterized in that, The electrode and bipolar plate composite assembly included in any one of claims 1 to 6.

9. The fuel cell stack according to claim 8, characterized in that, The fuel cell stack also includes an electrode frame disposed on the bipolar plate and surrounding the periphery of the electrode layer. Both the electrode frame and the bipolar plate have flow channels. A filter screen is provided at the flow channel opening of the electrode frame and / or the bipolar plate. The pore size of the filter screen is smaller than the particle size of the activated carbon particles and the graphene particles.

10. A flow battery, characterized in that, Includes the fuel cell stack as described in claim 8 or 9.

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