Preparation process of bipolar plate of flow battery

Abstract

The invention aims to provide a preparation process of a bipolar plate of a flow battery, and the bipolar plate is a composite material, has the characteristics of high conductivity and high toughness, and has better mechanical property and liquid resistance. The preparation method comprises the following steps: mixing a conductive carbon material, a resin material and a liquid assistant in a pulverizer, an emulsifying machine, a ball mill or a jet mill, then coating the mixture on the surface of a matrix, and drying, hot-pressing and separating to obtain the bipolar plate. The specific scheme is as follows: step 1, material mixing: preparing a carbon conductive material and a resin material according to a specific mass ratio; putting the prepared materials into a high-speed dispersion machine, an emulsifying machine, a ball mill or a jet mill for mixing to form a mixture; step 2, coating a base body layer, namely coating the mixture on the base body through an extruding machine, a molding press, a coating machine or a spraying machine; and 3, performing hot-pressing separation: performing hot-pressing on the coated substrate layer, and then separating from the substrate layer to prepare the bipolar plate.

Description

Technical Field

[0001] The invention relates to a fuel cell, in particular to a method for preparing a bipolar 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. Summary of the invention

[0004] The purpose of the present invention is to provide a process for preparing a bipolar plate for a liquid flow battery. The bipolar plate is a composite material having the characteristics of high conductivity and high toughness, and having good mechanical properties and liquid resistance.

[0005] The present invention mixes conductive carbon material, resin material and liquid additive in a pulverizer, emulsifier, ball mill or air flow pulverizer, then coats the mixture on the surface of a substrate, and obtains a bipolar plate after drying, hot pressing and separation.

[0006] The specific plan is as follows: A process for preparing bipolar plates for flow batteries, characterized in that it comprises: Step 1: Mixing materials The carbon conductive material and the resin material 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: Base layer coating The mixture is applied on a substrate through an extruder, a molding machine, a coater or a sprayer; Step 3: Hot pressing separation The coated substrate layer is hot pressed and then separated from the substrate layer to obtain a bipolar plate.

[0007] In some embodiments, the carbon conductive material is one or more mixtures of graphite, carbon fiber, expanded graphite, intercalated graphite, carbon black, carbon nanotubes, or graphene materials.

[0008] In some embodiments, the resin is one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyethylene terephthalate, polyetheretherketone, polyetherimide, and polyimide.

[0009] In some embodiments, the mass ratio of the carbon conductive material to the resin material is 1:1 to 50:1.

[0010] In some embodiments, the high-speed disperser, emulsifier, ball mill or air flow mill performs high-speed shear mixing on the carbon conductive material powder and the resin powder, and the shear rate is 10000~80000s -1 , the high-speed shear mixing time is 10~50min.

[0011] In some embodiments, the hot pressing temperature is 200-600°C.

[0012] In some embodiments, the hot pressing pressure is 1-8 MPa.

[0013] A process for preparing bipolar plates for flow batteries, characterized in that it comprises: Step 1: Mixing materials The carbon conductive material, the resin material and the liquid additive are configured 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: Base layer coating The mixture is applied on a substrate through an extruder, a molding machine, a coater or a sprayer; Step 3: Hot pressing separation The coated substrate layer is dried and hot pressed, and then separated from the substrate layer to obtain a bipolar plate.

[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 1000~10000s -1 .

[0015] In some embodiments, the high-speed shear mixing time is 10 to 600 minutes.

[0016] In some embodiments, when the conductive material and the resin material are subjected to high-speed shear mixing, a liquid auxiliary agent is added, which is one or more of water, alcohol, N-methylpyrrolidone, and N,N-dimethylformamide.

[0017] In some embodiments, the mass of the liquid auxiliary agent is 0.1 to 10 times the mass of the solid mixture.

[0018] Compared with the prior art, the present invention has the following advantages: Compared with conventional graphite bipolar plates and metal bipolar plates, the composite material bipolar plates prepared by the present invention have the characteristics of high conductivity, mechanical strength, high toughness, and good corrosion resistance and liquid resistance. In the solid-state dry process, the bipolar plate has low porosity, small amount of washing liquid, and good low-temperature performance of the liquid flow battery. The solid-state dry process has high production efficiency and saves drying energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a flowchart showing the process of preparing bipolar plates for liquid flow batteries according to an embodiment of the present invention. Specific embodiments

[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 bipolar plates for flow batteries, characterized by the following: Step 1: Graphite is used as the carbon conductive material, and PTFE is used as the resin material, and the materials are configured in a mass ratio of 3:1, and the above materials are sheared, mixed and fiberized in a jet mill to form a mixture. Step 2: The mixture is coated and formed on a substrate through an extruder. Step 3: After coating, hot pressing is performed, and then the bipolar plate is separated from the substrate layer to obtain the bipolar plate. The shear rate is 80,000 s -1 , high-speed shear mixing time 50min; hot pressing temperature 350℃, hot pressing pressure 4MPa. Example 2

[0022] Similar to Example 1, except that: the carbon conductive material is graphite and carbon nanotubes, the resin material is PTFE powder, the mass ratio is 7:1:2; the shear rate is 50000s -1 , high-speed shear mixing time is 30min; hot pressing temperature is 350℃, and hot pressing pressure is 4MPa. Example 3

[0023] Similar to Example 1, except that the conductive material is graphite and carbon black, the resin material is PVDF, the mass ratio is 8:1:1; the shear rate is 10000s -1, high-speed shear mixing time 50min; hot pressing temperature 350℃, hot pressing pressure 8MPa. Example 4

[0024] Similar to Example 1, except that: the conductive material is graphite, graphene, the resin material is PVDF, the mass ratio is 8:1:1; the shear rate is 10000s -1 , high-speed shear mixing time is 20min; hot pressing temperature is 350℃, and hot pressing pressure is 4MPa. Example 5

[0025] Similar to Example 1, except that: the conductive material is carbon fiber and carbon nanotube, the resin material is PTFE, the mass ratio is 8:1:1; the shear rate is 50000s -1 , high-speed shear mixing time 40min; hot pressing temperature 600℃, hot pressing pressure 4MPa. Example 6

[0026] Step 1: Mixing materials The carbon conductive material, the resin material and the liquid additive are configured in a specific mass ratio; the conductive material is graphite, carbon fiber and carbon nanotube, the resin material is PTFE, and the mass ratio is 6:2:1:1; the liquid additive is isopropanol, and its mass is 3 times the mass of the solid mixture; Put the prepared materials into a high-speed disperser, emulsifier, ball mill or air flow mill for mixing to form a mixture; the shear rate is 5000s -1 , high-speed shear mixing time 180min; Step 2: Base layer coating The mixture is applied on a substrate through an extruder, a molding machine, a coater or a sprayer; Step 3: Hot pressing separation The coated substrate layer is dried and then hot pressed at a temperature of 400°C and a pressure of 5MPa, and then separated from the substrate layer to obtain a bipolar plate. Example 7

[0027] Similar to Example 6, except that: the conductive material is graphite, carbon fiber, carbon nanotubes, the resin material is PTFE, the mass ratio is 6:2:1:1; the liquid additive is isopropanol, the mass of which is 3 times the mass of the solid mixture; the shear rate is 7000s -1 , high-speed shear mixing time is 180min; hot pressing temperature is 400℃, and hot pressing pressure is 6MPa. Example 8

[0028] Similar to Example 6, except that: the conductive material is graphite, carbon fiber, carbon nanotubes, the resin material is PVDF, the mass ratio is 6:2:1:1; the liquid additive is N-methylpyrrolidone, the mass of which is 5 times the mass of the solid mixture; the shear rate is 1000s -1 , high-speed shear mixing time 600min; hot pressing temperature 400℃, hot pressing pressure 5MPa. Example 9

[0029] Similar to Example 6, except that: the conductive material is graphite, carbon fiber, carbon nanotubes, the resin material is PTFE, the mass ratio is 6:2:1:1; the liquid additive is isopropanol, the mass of which is 10 times the mass of the solid mixture; the shear rate is 5000s -1 , high-speed shear mixing time is 180min; hot pressing temperature is 400℃, and hot pressing pressure is 5MPa. Example 10

[0030] Similar to Example 6, except that: the conductive material is graphite, carbon fiber, carbon nanotubes, the resin material is PTFE, the mass ratio is 6:2:1:1; the liquid additive is isopropanol, the mass of which is 3 times the mass of the solid mixture; the shear rate is 5000s -1 , high-speed shear mixing time is 180min; hot pressing temperature is 400℃, and hot pressing pressure is 8MPa.

Claims

1. A process for preparing bipolar plates for flow batteries, characterized in that: The method includes configuring carbon 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; passing the mixture through an extruder, a molding machine, a coater or a sprayer, coating it on a substrate and performing hot pressing, and separating the mixture from the substrate to form a bipolar plate.

2. A process for preparing bipolar plates for flow batteries according to claim 1, characterized in that: The carbon conductive material is one or more mixtures of graphite, carbon fiber, expanded graphite, intercalated graphite, carbon black, carbon nanotubes or graphene materials.

3. A process for preparing bipolar plates for flow batteries 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.

4. A process for preparing bipolar plates for flow batteries according to claim 1, characterized in that: The mass ratio of the carbon conductive material powder to the resin powder is 1:1 to 50:

1.

5. A process for preparing bipolar plates for flow batteries according to claim 1, characterized in that: The carbon conductive material powder 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 , the high-speed shear mixing time is 10~50min.

6. A process for preparing bipolar plates for flow batteries according to claim 1, characterized in that: The hot pressing temperature is 200-600° C., and the hot pressing pressure is 1-8 MPa.

7. A process for preparing bipolar plates for flow batteries according to claim 1, characterized in that: When the conductive material and the resin powder are mixed by high-speed shearing using the high-speed disperser or emulsifier, a liquid auxiliary agent is added and then coated on the substrate, and a drying step is added before hot pressing.

8. A process for preparing bipolar plates for flow batteries according to claim 7, characterized in that: The shear rate is 1000~10000s -1 , the high-speed shear mixing time is 10~600min.

9. A process for preparing bipolar plates for flow batteries according to claim 7, characterized in that: The liquid auxiliary agent is one or more of water, alcohol, N-methylpyrrolidone and N,N-dimethylformamide, and the added mass is 0.1 to 10 times the mass of the solid mixture.

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