Process for preparing integrated polar plate of flow battery

Abstract

The invention aims to provide the preparation process of the integrated polar plate of the flow battery, the electrode and the bipolar plate are integrated into an integrated structure, and the introduction of an electrode / bipolar plate contact interface is avoided, so that the internal resistance of the flow battery can be effectively reduced. The integrated structural design also improves the efficiency and consistency of stack assembly, and improves the product quality. The method comprises the following steps: directly mixing conductive carbon material powder and resin material powder, carrying out fibrillation in a crusher, a ball mill or an emulsifying machine, coating the fibrillation mixture on the surface of a bipolar plate of the flow battery to form a middle conductive layer, and finally hot-pressing a graphite felt electrode on the middle conductive layer to obtain the flow battery. And preparing to obtain the integrated flow battery pole plate. According to the process, the use of solvents in the process can be reduced, the environmental pollution and the energy consumption are reduced, meanwhile, the integrated polar plate is more beneficial to reducing the contact resistance in the flow battery, and the product performance and the efficiency are improved.

Description

Technical Field

[0001] The invention relates to a liquid flow battery, in particular to a process for preparing an integrated polar plate of a liquid flow battery. Background Art

[0002] The stack of a flow battery is composed of multiple cells connected in series, and is mainly composed of end plates, current collectors, bipolar plates, electrodes, diaphragms, etc. As an important component of a flow battery, the bipolar plate has the following functions: connecting adjacent cells in series, isolating the electrolytes on both sides, conducting internal electrons, and supporting electrodes. Therefore, the bipolar plate needs to have good conductivity, mechanical strength, and corrosion resistance. The current bipolar plates of flow batteries are graphite bipolar plates, metal bipolar plates, and other types. The bipolar plate and the electrode are two independent components, and there is a certain contact resistance when the two are assembled, thereby increasing the internal resistance of the battery.

[0003] Liquid flow battery bipolar plates are classified by materials, mainly including graphite, metal, and composite materials. Graphite materials have high conductivity, low density, good corrosion resistance, and can be easily formed into specific flow channels through mechanical processing; however, graphite materials have insufficient mechanical strength and are prone to brittle fracture. In addition, the high porosity of graphite plates and the slow corrosion process under high potential make them challenging to use in practical applications. Metal bipolar plates have advantages in mechanical properties and have good electrical conductivity, thermal conductivity, and mechanical properties. They can be prepared by stamping, but electrochemical corrosion also occurs. Composite bipolar plates have the characteristics of high conductivity of graphite materials and high toughness of polymer materials. They have relatively low manufacturing costs and relatively good mechanical properties, but due to the introduction of polymer materials, the conductivity is also reduced accordingly.

[0004] Although the above three types of bipolar plates have their own strengths, in actual applications, there will be a contact interface between the electrode and the bipolar plate, which will introduce contact resistance. Therefore, the integrated electrode-bipolar plate can reduce the contact resistance and improve the performance of the flow battery while developing various material properties. Summary of the invention

[0005] The purpose of the present invention is to provide a process for preparing an integrated plate for a liquid flow battery, which integrates the electrode and the bipolar plate into an integrated structure, avoiding the introduction of the electrode / bipolar plate contact interface, thereby effectively reducing the internal resistance of the liquid flow battery. The integrated structural design will also improve the efficiency and consistency of the battery stack assembly and enhance product quality.

[0006] In order to achieve the above purpose, the present invention utilizes the principle that the resin material becomes fibrils under the action of high-speed shear force. The fibrillated resin material is in a mesh shape and can adhere to the carbon powder of the conductive material to achieve direct dispersion of the conductive material and the binder. When the resin material fibrils are processed, there is no need to use a solvent for dispersion. The resin material is directly mixed with the conductive material as a binder by high shearing, replacing the wet impregnation process.

[0007] The present invention directly mixes the conductive carbon material and the resin material powder, and fibrillates them in a pulverizer, a ball mill or an emulsifier, and then coats the fibrillated mixture on the surface of the bipolar plate of the flow battery to form an intermediate conductive layer, and finally hot presses the graphite felt electrode on the intermediate conductive layer to prepare an integrated flow battery plate. This process can reduce the use of solvents in the process, reduce environmental pollution and energy consumption, and at the same time, the integrated plate is more helpful to reduce the contact resistance inside the flow battery and improve product performance and efficiency.

[0008] The specific plan is as follows: A process for preparing an integrated plate for a flow battery, the characteristics of which include: Step 1: Preparation of conductive intermediate layer materials The conductive material powder and the resin material powder are arranged in a specific mass ratio; Put the prepared materials into a high-speed disperser, emulsifier, ball mill or air flow mill for mixing to form a mixture; Step 2: Conductive intermediate layer coating The mixture is applied to both sides of the base bipolar plate by an extruder, a molding machine, a coating machine or a sprayer to form an intermediate conductive layer on both sides of the base bipolar plate; Step 3: Integrated hot pressing The graphite felt electrode is placed on the other side of the middle conductive layer and hot pressed together with the base bipolar plate and the middle conductive layer to form an integrated electrode plate.

[0009] In some embodiments, the hot pressing temperature of the graphite felt electrode and the base bipolar plate with the intermediate conductive layer is 200-600°C.

[0010] In some embodiments, the hot pressing pressure is 1-8 MPa.

[0011] In some embodiments, the conductive material is one or more mixtures of graphite, carbon fiber, expanded graphite, intercalated graphite, carbon black, carbon nanotubes, or graphene materials.

[0012] In some embodiments, the resin is one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyethylene terephthalate, polyetheretherketone, polyetherimide, and polyimide.

[0013] In some embodiments, the mass ratio of the conductive material to the resin material is 1:1 to 50:1.

[0014] In some embodiments, the high-speed disperser is used to perform high-speed shear mixing on the conductive material and the resin material powder, and the shear rate is 10000~80000s -1 .

[0015] In some embodiments, the high-speed shear mixing time is 10 to 50 minutes.

[0016] In some embodiments, the conductive material content in the intermediate conductive layer is 0.2-8.0 mg / cm 2 .

[0017] Compared with the prior art, the present invention mainly has the following advantages: Compared with the traditional battery assembly process, the present invention integrates the electrode and the bipolar plate into one, avoiding the separate assembly of the electrode and the bipolar plate, minimizing the contact resistance of the electrode-bipolar plate, and helping to reduce the internal resistance of the liquid flow battery and improve the performance of the liquid flow battery. In addition, the present invention introduces an intermediate conductive layer, which combines the characteristics of various materials and has the advantages of high conductivity, high mechanical strength, high corrosion resistance, high liquid resistance, etc. This process adopts a dry process to obtain the intermediate conductive layer during the preparation of the integrated plate, avoiding the use of solvents, and the process is simple. There is no need for drying operations, the process has low energy consumption, and it is environmentally friendly. In the dry preparation process of the intermediate conductive layer, the material ratio and the surface density of the conductive material can be more accurately controlled than the wet process. The dry process can reduce the generation of porosity and improve the corrosion resistance of the plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a flowchart showing the process of preparing integrated plates for liquid flow batteries according to an embodiment of the present invention.

[0019] Figure 2 The figure is a schematic diagram showing the structure of an integrated plate of a flow battery prepared by the process of the present invention. Example

[0020] The technical solution of the present invention is further described in detail below through embodiments and in combination with the accompanying drawings, but is not limited to the contents of the embodiments. Example 1

[0021] A process for preparing an integrated plate for a liquid flow battery, characterized in that it includes: step 1: using carbon black as a conductive material and PTFE as a resin material, configuring them in a mass ratio of 3:1, and shearing and mixing them in a high-speed disperser to form a mixture. Step 2: coating the mixture on both sides of the base bipolar plate through an extruder to form an intermediate conductive layer, wherein the conductive material content is about 0.9 mg / cm 2 Step 3: Place the graphite felt electrode on the other side of the middle conductive layer, and hot press it together with the base bipolar plate and the middle conductive layer at a hot pressing temperature of 300°C and a hot pressing pressure of 2MPa. Example 2

[0022] The main process is similar to that of Example 1, but the conductive material is graphene and the resin material is PTFE powder, with a mass ratio of 2:1; the content of the conductive material in the middle conductive layer is 0.8 mg / cm 2 ; Hot pressing temperature is 350℃, hot pressing pressure is 2.5MPa. Example 3

[0023] The main process is similar to that of Example 1, but the conductive material is expanded graphite and carbon nanotubes, and the resin material is PTFE powder, with a mass ratio of 2:2:1; the conductive material content in the middle conductive layer is 2 mg / cm 2 ; Hot pressing temperature is 350℃, hot pressing pressure is 4MPa. Example 4

[0024] The main process is similar to that of Example 1, but the conductive materials are expanded graphite and carbon nanotubes, and the resin material is PVDF powder, with a mass ratio of 2:2:1; the conductive material content in the middle conductive layer is 2 mg / cm 2 ; Hot pressing temperature is 350℃, hot pressing pressure is 8MPa. Example 5

[0025] The main process is similar to that of Example 1, but the conductive material is intercalated graphite and carbon nanotubes, and the resin material is PTFE powder, with a mass ratio of 2:2:1; the conductive material content in the middle conductive layer is 2 mg / cm 2 ; Hot pressing temperature is 350℃, hot pressing pressure is 4MPa. Example 6

[0026] The main process is similar to that of Example 1, but the conductive material is intercalated graphite and carbon nanotubes, and the resin material is PVDF powder, with a mass ratio of 2:2:1; the conductive material content in the middle conductive layer is 5 mg / cm 2 ; Hot pressing temperature is 350℃, hot pressing pressure is 4MPa. Example 7

[0027] The main process is similar to that of Example 1, but the conductive materials are carbon black and carbon nanotubes, and the resin material is PTFE powder, with a mass ratio of 2:2:1; the conductive material content in the middle conductive layer is 8 mg / cm 2 ; Hot pressing temperature is 350℃, hot pressing pressure is 4MPa. Example 8

[0028] The main process is similar to that of Example 1, but the conductive material is carbon fiber and graphene, and the resin material is PTFE powder, with a mass ratio of 2:1:1; the content of the conductive material in the middle conductive layer is 1.8 mg / cm 2 ; Hot pressing temperature is 350℃, hot pressing pressure is 3.5MPa. Example 9

[0029] The main process is similar to that of Example 1, but the conductive materials are carbon black, carbon nanotubes, and graphene, and the resin material is PTFE powder, with a mass ratio of 2:1:1:1; the conductive material content in the middle conductive layer is 2 mg / cm 2 ; Hot pressing temperature 400℃, hot pressing pressure 5MPa. Example 10

[0030] The main process is similar to that of Example 1, but the conductive material is expanded graphite, carbon nanotubes, and graphene, and the resin material is PVDF powder, with a mass ratio of 2:1:1:1; the conductive material content in the middle conductive layer is 2 mg / cm 2 ; Hot pressing temperature 400℃, hot pressing pressure 5MPa.

Claims

1. A process for preparing an integrated plate for a flow battery, characterized in that: The method includes configuring conductive material powder and resin powder in a specific mass ratio; placing the configured materials into a high-speed disperser, an emulsifier, a ball mill or a jet mill for mixing to form a mixture; applying the mixture on both sides of a base bipolar plate through an extruder, a molding machine, a coater or a sprayer to form an intermediate conductive layer on both sides of the base bipolar plate; placing a graphite felt electrode on the other side of the intermediate conductive layer, and hot pressing it together with the base bipolar plate and the intermediate conductive layer to form an integrated electrode plate.

2. A process for preparing an integrated plate for a liquid flow battery according to claim 1, characterized in that: The hot pressing temperature of the graphite felt electrode and the substrate bipolar plate with the intermediate conductive layer is 200-600° C., and the hot pressing pressure is 1-8 MPa.

3. A process for preparing an integrated plate for a liquid flow battery according to claim 1, characterized in that: The conductive material is one or more mixtures of graphite, carbon fiber, expanded graphite, intercalated graphite, carbon black, carbon nanotubes or graphene materials.

4. The process for preparing an integrated plate for a liquid flow battery according to claim 1, characterized in that: The mass ratio of the conductive material powder to the resin powder is 1:1 to 50:

1.

5. The process for preparing an integrated plate for a liquid flow battery according to claim 1, characterized in that: The conductive material and the resin powder are mixed by high-speed shearing using the high-speed disperser, emulsifier, ball mill or air flow mill, and the shear rate is 10000~80000s -1 .

6. The process for preparing an integrated plate for a liquid flow battery according to claim 1, characterized in that: The resin used is one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyethylene terephthalate, polyetheretherketone, polyetherimide and polyimide.

7. A process for preparing an integrated plate for a liquid flow battery according to claim 5, characterized in that: The high-speed shear mixing time is 10 to 50 minutes.

8. The process for preparing an integrated plate for a liquid flow battery according to claim 1, characterized in that: The conductive material content in the intermediate conductive layer is 0.2-8.0 mg / cm 2 .

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