A carbon-plastic composite electrode plate, its preparation method and application

Abstract

The present invention belongs to the field of flow batteries, and specifically discloses a carbon-plastic composite plate and its preparation method and application. The present invention realizes the uniform mixing of carbon materials and nano-resins through air convection, enables the nano-resins to be orderly stacked on the surface and between the layers of the carbon materials, improves the swelling and rebound during the molding process, and further inhibits the volume effect and the generation of micro-cracks of the formed plate. A continuous conductive and heat-conductive filler network can be formed, so that the carbon-plastic composite plate has a low resistivity and conductivity, and the nano-resin containing a carbazole unit has high thermal stability and is not easily aged in the battery environment.

Description

Technical Field

[0001] The invention belongs to the field of liquid flow batteries, and specifically relates to a carbon-plastic composite plate and a preparation method and application thereof. Background Art

[0002] As the core component of the flow battery, the plate mainly isolates the positive and negative ions of adjacent batteries and transfers current and heat. However, in the actual operation of the battery, the plate also needs to have excellent bending and compressive strength, air tightness, hydrophobicity and corrosion resistance. At the same time, in order to improve the power density of the battery and reduce production costs, the plate should be as light and thick as possible while ensuring the normal operation of various functions. The types of plates can be mainly divided into: graphite plates, metal plates and composite plates according to the material. Among them, carbon-plastic composite plates are a new type of composite material. It is made of graphite and polymer resin. It has the advantages of simple process, easy forming, sufficient raw materials and low production cost. It can use molding to carve flow channels on the plate instead of complex processing. Therefore, it has received widespread attention.

[0003] The processing performance and structural strength of carbon-plastic composite plates are significantly better than those of hard graphite plates, and their liquid resistance is also better than that of flexible graphite plates. In addition, their corrosion resistance is much stronger than that of ordinary metal plates. These characteristics make carbon-plastic composite plates widely used. However, the resistivity of carbon-plastic composite plates is usually 1 to 2 orders of magnitude higher than that of metal plates and graphite plates, resulting in a lack of conductive effect; and due to the high resistance, a large amount of heat will inevitably be generated during the discharge process, which will increase the battery temperature and easily lead to the failure of the proton exchange membrane.

[0004] Patent CN114976086B discloses a composite graphite bipolar plate and a preparation method. The electrical conductivity, thermal conductivity and hydrogen barrier of the composite graphite plate are improved by grafting modified graphene with thermosetting azidophenolic resin; and the compatibility of the conductive filler and the resin is improved by solvent-free hot pressing and curing the powder, thus avoiding the problem of local expansion of the plate caused by the direct hot pressing process. However, the azidopolymer product may cause problems such as a widening of the molecular weight distribution and uncontrollable molecular chain end groups, which may cause the plate to have fine cracks, bending deformation and other problems during the operation of the battery stack due to repeated changes in temperature and force. Summary of the invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the present application provides a low-resistance carbon-plastic composite plate and a preparation method thereof. The carbon-plastic composite plate has a low resistivity, effectively improves the conductivity and interlayer toughness of the composite material, thereby solving problems such as fine cracks and bending deformation that may occur during the use of the battery.

[0006] In order to achieve the above purpose, the technical solution adopted in this application is:

[0007] In the first aspect of the present application, a method for preparing a low-resistance carbon-plastic composite plate is provided, comprising the following raw materials: mixing a nano-resin and a carbon-based mixture by air convection to obtain a mixture; spreading powder and pre-pressing to obtain a blank plate; and then hot-pressing the blank plate to obtain the low-resistance carbon-plastic composite plate.

[0008] Preferably, the mass ratio of the nano-resin to the carbon-based mixture is (0.18 - 0.32):1.

[0009] In the present application, the carbon material and the resin are mixed by air convection, so that the nano-resin can be stacked orderly on the surface and between the layers of the carbon material, realizing the uniform mixing of the graphite powder and the adhesive resin, which is convenient for later powder spreading.

[0010] In some embodiments, the specific operation of the hot pressing is as follows: first, hot-press at a hot plate temperature of 240 - 280 o °C and a pressure of 8 - 14 MPa for 3 - 5 min; then hot-press at a hot plate temperature of 180 - 220 o °C and a pressure of 15 - 22 MPa for 2 - 4 min; then, at this temperature, mold the flow channel; finally, cool to room temperature and demold.

[0011] In some embodiments, the particle size of the nano-resin is 70 - 120 nm.

[0012] In some embodiments, the preparation steps of the nano-resin are as follows:

[0013] S1. Stir N-methylpyrrolidone and sodium sulfide at 150 - 180 o °C for 20 - 40 min, add p-dichlorobenzene, p-dichlorobenzoic acid and sodium hydroxide, pass nitrogen, first heat up to 200 - 240 o °C and keep warm for 1 - 4 h, then heat up to 260 - 280 o °C and keep warm for 1 - 3 h, after cooling to room temperature, acidify, wash, filter, and vacuum dry to obtain reactant 1;

[0014] S2. Under nitrogen protection, stir dichloromethane, aluminum trichloride and 3,6-bis[9-carbazolyl]-9-phenylcarbazole at 30 - 60 o °C for 12 - 17 h, then add the reactant 1 obtained in step S1 and stir for 8 - 12 h, after cooling to room temperature, filter, wash, recrystallize, and vacuum dry, and vacuum drying gives the nano-resin.

[0015] In some embodiments, the mass ratio of sodium sulfide to p-dichlorobenzene in step S1 is 1:(0.73 - 0.98).

[0016] In some embodiments, the mass ratio of aluminum trichloride, 3,6-bis(9-carbazolyl)-9-phenylcarbazole, and reactant 1 in step S2 is (9.2 - 11.8):1:(8.71 - 10.05).

[0017] In this application, a nano-resin with a specific particle size is obtained through a specific process. On the one hand, this nano-resin solves the problem of poor impregnation between the carbon-based mixture and the thermoplastic resin, improves the bonding interface strength, and reduces the production difficulty and cost. On the other hand, by introducing carbazole units, the thermal stability of the polymer is enhanced, preventing the formation of a conjugated structure between the unsaturated S atoms in the resin molecules and the benzene rings on the molecular chain, increasing the difficulty of oxidizing the thioether bonds in the macromolecules to sulfoxide groups and sulfone groups, ensuring that the main chain is not easily broken, and making the resin less likely to age in the battery environment. On the third hand, through the interaction between the polymer skeletons, the microporosity of the polymer formed by the self-polymerization of carbazole units is reduced, and at the same time, the permeability of the electrode plate is decreased, eliminating the need for hole plugging and contributing to an increase in the power density of the battery.

[0018] In some embodiments, the carbon-based mixture includes graphite, graphene, and multi-walled carbon nanotubes.

[0019] In some embodiments, the mass ratio of graphite, graphene, and multi-walled carbon nanotubes is 1:(0.1 - 0.3):(0.05 - 0.25).

[0020] Through the specific selection of the types and ratios of various carbon-based materials, the carbon-based mixture in this application can form a perfect conductive network in the composite electrode plate. However, during the operation of the battery stack, the electrode plate may develop small cracks, bending deformation, etc. due to the repeatedly changing temperature and mechanical stress. After the nano-resin in this application is mixed with the carbon-based mixture, part of it is distributed between the carbon material layers, which can improve the expansion and rebound during the molding process and simultaneously inhibit the volume effect and the generation of microcracks in the formed electrode plate.

[0021] To improve the electrical conductivity of the carbon-plastic composite electrode plate, a common method is to increase the amount of carbon-based materials. However, a high amount of carbon-based materials will cause a significant decline in the processing performance and mechanical properties of the materials. The electron-withdrawing property of the S atoms in the nano-resin in this application is beneficial for adjusting the electronic properties of the carbon materials, making it easier to polarize electron pairs, generating charge positions, and achieving the purpose of improving the electrochemical performance.

[0022] In the second aspect of this application, a low-resistance carbon-plastic composite electrode plate is provided, and the resistivity of the composite electrode plate is 1.6 - 3.4 mΩ·cm 2 。

[0023] In the third aspect of this application, the application of a low-resistance carbon-plastic composite electrode plate in flow batteries and fuel cells is provided.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present application provides a low-resistance carbon-plastic composite plate. Through air convection, the nano-resin can be stacked orderly on the surface and between layers of the carbon material, improving the expansion and rebound during the molding process, and at the same time suppressing the volume effect and the generation of microcracks of the formed plate.

[0026] 2. The present application strengthens the thermal stability of the polymer by introducing carbazole units into the nano-resin, avoiding the formation of a conjugated structure between the unsaturated S atoms in the resin molecule and the benzene ring on the molecular chain, increasing the difficulty of oxidizing the thioether bonds in the macromolecule to sulfoxide groups and sulfone groups, ensuring that the main chain is not easily broken, and making the resin not easily age in the battery environment.

[0027] 3. The nano-resin of the present application reduces the microporosity of the polymer formed by the self-polymerization of carbazole units through the interaction between the polymer skeletons, and at the same time reduces the permeability of the plate, so that it does not need to be plugged, which helps to improve the power density of the battery.

[0028] 4. The present application optimizes the process of improving the conductivity of the carbon-plastic composite plate. By adjusting the electronic properties of the carbon material through the electron-withdrawing characteristics of S atoms in the nano-resin, the carbon material is more likely to polarize electron pairs and generate charge positions, achieving the purpose of improving the electrochemical performance. Detailed implementation manners

[0029] The following will illustrate the present invention in combination with specific implementation manners. It should be noted that the following examples are examples of the present invention, only for illustrating the present invention, and not for limiting the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the main idea or scope of the present invention.

[0030] Preparation Example 1

[0031] The preparation steps of nano-resin-A are as follows:

[0032] S1. Stir 500 mL of N-methylpyrrolidone and 100 g of sodium sulfide at 160 o °C for 30 min, add 85.13 g of p-dichlorobenzene, 7 g of p-dichlorobenzoic acid and 2.5 g of sodium hydroxide, pass nitrogen, first heat to 220 o °C and keep warm for 3 h, then heat to 270 o °C and keep warm for 2 h. After cooling to room temperature, adjust the pH to 6 ± 0.2, wash with deionized water, filter, and vacuum dry at 60 o °C to constant weight to obtain Reactant 1;

[0033] S2. Under nitrogen protection, 80 mL of dichloromethane, 108 g of aluminum trichloride, and 10 g of 3,6-bis[9-carbazolyl]-9-phenylcarbazole were stirred at 40 o °C for 15 h, then 93 g of the reactant 1 obtained in step S1 was added and stirred for 10 h. After cooling to room temperature, the mixture was filtered, and the filter cake was washed successively with 1 M hydrochloric acid and deionized water, recrystallized, and dried under vacuum at 80 o °C to constant weight to obtain nano-resin-A.

[0034] Preparation Example 2

[0035] The preparation steps of nano-resin-B are as follows:

[0036] The difference between this preparation example and Preparation Example 1 is that: 70 g of p-dichlorobenzene was used in step S1.

[0037] Preparation Example 3

[0038] The preparation steps of nano-resin-C are as follows:

[0039] The difference between this preparation example and Preparation Example 1 is that: 105 g of p-dichlorobenzene was used in step S1.

[0040] Preparation Example 4

[0041] The preparation steps of nano-resin-D are as follows:

[0042] The difference between this preparation example and Preparation Example 1 is that: 13 g of 3,6-bis[9-carbazolyl]-9-phenylcarbazole was used in step S2.

[0043] Preparation Example 5

[0044] The preparation steps of nano-resin-E are as follows:

[0045] The difference between this preparation example and Preparation Example 1 is that: 8 g of 3,6-bis[9-carbazolyl]-9-phenylcarbazole was used in step S2.

[0046]

[0047] Example 1

[0048] A preparation method of a low-resistance carbon-plastic composite plate electrode comprises the following steps:

[0049] Using an air convection device, a nano-resin-A and a carbon-based mixture with a mass ratio of 0.26:1 were mixed to obtain a mixture; powder was spread and pre-pressed to obtain a blank plate; then the blank plate was first hot-pressed at a hot plate temperature of 260 o °C and a pressure of 11 MPa for 4 min; then at a hot plate temperature of 200 oC, hot press for 3 min at a pressure of 18 MPa; then, at this temperature, mold the flow channels; finally, cool to room temperature and demold to obtain the composite electrode plate.

[0050] Among them, the carbon-based mixture contains graphite, graphene, and multi-walled carbon nanotubes with a mass ratio of 1:0.2:0.15.

[0051] Example 2

[0052] A preparation method of a low-resistance carbon-plastic composite electrode plate, comprising the following steps:

[0053] Use air convection to mix nano-resin-A and a carbon-based mixture with a mass ratio of 0.18:1 to obtain a mixture; spread the powder and pre-press to obtain a blank plate; then, first heat-press the blank plate at a hot plate temperature of 240 o C, hot press for 3 min at a pressure of 14 MPa; then, at a hot plate temperature of 180 o C, hot press for 2 min at a pressure of 22 MPa; then, at this temperature, mold the flow channels; finally, cool to room temperature and demold to obtain the composite electrode plate.

[0054] Among them, the carbon-based mixture contains graphite, graphene, and multi-walled carbon nanotubes with a mass ratio of 1:0.1:0.05.

[0055] Example 3

[0056] A preparation method of a low-resistance carbon-plastic composite electrode plate, comprising the following steps:

[0057] Use air convection to mix nano-resin-A and a carbon-based mixture with a mass ratio of 0.32:1 to obtain a mixture; spread the powder and pre-press to obtain a blank plate; then, first heat-press the blank plate at a hot plate temperature of 280 o C, hot press for 5 min at a pressure of 8 MPa; then, at a hot plate temperature of 220 o C, hot press for 4 min at a pressure of 15 MPa; then, at this temperature, mold the flow channels; finally, cool to room temperature and demold to obtain the composite electrode plate.

[0058] Among them, the carbon-based mixture contains graphite, graphene, and multi-walled carbon nanotubes with a mass ratio of 1:0.3:0.25.

[0059] Example 4

[0060] This example provides a preparation method of a low-resistance carbon-plastic composite electrode plate. The specific implementation method is the same as that of Example 1, except that nano-resin-A is replaced by an equal amount of nano-resin-B.

[0061] Example 5

[0062] This embodiment provides a preparation method of a low-resistance carbon-plastic composite plate electrode. The specific implementation manner is the same as that of Embodiment 1, except that nano-resin-A is replaced by an equal amount of nano-resin-C.

[0063] Example 6

[0064] This embodiment provides a preparation method of a low-resistance carbon-plastic composite plate electrode. The specific implementation manner is the same as that of Embodiment 1, except that nano-resin-A is replaced by an equal amount of nano-resin-D.

[0065] Example 7

[0066] This embodiment provides a preparation method of a low-resistance carbon-plastic composite plate electrode. The specific implementation manner is the same as that of Embodiment 1, except that nano-resin-A is replaced by an equal amount of nano-resin-E.

[0067] Example 8

[0068] This embodiment provides a preparation method of a low-resistance carbon-plastic composite plate electrode. The specific implementation manner is the same as that of Embodiment 1, except that the carbon-based mixture contains graphite and graphene with a mass ratio of 1:0.2.

[0069] Example 9

[0070] This embodiment provides a preparation method of a low-resistance carbon-plastic composite plate electrode. The specific implementation manner is the same as that of Embodiment 1, except that the carbon-based mixture contains graphite and multi-walled carbon nanotubes with a mass ratio of 1:0.15.

[0071] Example 10

[0072] This embodiment provides a preparation method of a low-resistance carbon-plastic composite plate electrode. The specific implementation manner is the same as that of Embodiment 1, except that the carbon-based mixture contains graphene and multi-walled carbon nanotubes with a mass ratio of 1:0.75.

[0073] Performance test:

[0074] 1. Resistance test

[0075] Use a four-probe resistance tester (Ruikewei FT-541SJB, Ningbo, China) to test the resistance of the composite plate electrode. During the measurement, avoid sample deformation and dust on the sample surface. Select at least five positions near the edge and center of the composite plate electrode and calculate the average value.

[0076] 2. Flexural strength

[0077] Use a mechanical universal testing machine to measure the flexural strength of the composite plate electrode provided in each embodiment according to the industry standard NB / T 42007-2013. The loading speed is 0.5 mm / min. The size of the composite plate electrode is 100 mm × 10 mm, and the span is 64 mm.

[0078] To reflect the heat aging performance of the nano-resin, the composite electrode plate was heat-treated: The composite electrode plate was placed in a high-temperature electrothermal blast drying oven and heated at a rate of 5 o °C / min to 350 o °C, then aged at a constant temperature for 1 h, taken out and placed in a desiccator to cool to room temperature; then put back into the electrothermal blast drying oven and heated at a rate of 5 o °C / min to 350 o °C, then aged at a constant temperature for 200 h, taken out and placed in a desiccator to cool to room temperature, and the flexural strength test was carried out again.

[0079] 3. Air permeability test

[0080] Reference standard: NB / T 42007-2013. The specific test method includes: Hydrogen and inert gas with a temperature of (25 ± 1.5) o °C and a pressure of 0.1 MPa were introduced into both sides of the fixture gas chamber respectively to ensure that the pressures on both sides were balanced (controlled by precision pressure gauges on both sides), and stabilized for at least 5 h. Then, the outlet of the inert gas was introduced into a gas chromatograph to measure the concentration of the gas to be measured, and the chromatogram was recorded. Calculate the hydrogen permeation rate C of the composite electrode plate per unit time and per unit area according to C = q / S;

[0081] In the formula: q is the gas permeation amount per unit time, cm 3 / s; S is the effective test area of the permeation cell, cm 2 .

[0082] The test results are shown in Table 1.

[0083] Table 1

[0084]

[0085] It can be seen from the data in Table 1 that the composite electrode plates of Examples 1-3 have lower resistance and air permeability, and can effectively exert the conductive performance and gas barrier effect; in addition, they also have higher flexural strength, indicating that the interface between the nano-resin and the carbon-based mixture in them is strongly bonded, and the difference in flexural strength before and after heat treatment is small, reflecting the heat aging performance of the nano-resin in the composite electrode plate.

[0086] Compared with Example 1, the nano-resin used in the composite electrode plates of Examples 4-5 changed the dosage of p-dichlorobenzene in step S1, which caused a large change in the particle size of the nano-resin, which may lead to self-aggregation of the nano-resin or uneven mixing with the carbon-based mixture, resulting in micro-cracks during the molding process, and further leading to an increase in resistance and air permeability; it can be seen from the change in flexural strength before and after heat treatment that the micro-cracks that occurred during production will further expand after heat treatment, resulting in a decrease in flexural strength.

[0087] Compared with Example 1, the nano-resin used in the composite electrodes of Examples 6-7 changes the dosage of 3,6-bis[9-carbazolyl]-9-phenylcarbazole in step S2, which is not conducive to the introduction of carbazole units, and then affects the thermal stability of the nano-resin and the microporosity of the composite electrodes, resulting in a decrease in the flexural strength of the electrodes and an increase in air permeability; from the air permeability, it can be seen that the introduction of an appropriate amount of carbazole units can also improve the gas barrier property of the electrodes.

[0088] Compared with Example 1, the composite electrodes of Examples 8-10 change the type of carbon material in the carbon-based mixture, resulting in a decrease in electrical conductivity, flexural performance and gas barrier performance.

[0089] The above-described embodiments do not impose any formal limitations on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or equivalent variations using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent variation and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a carbon-plastic composite plate, characterized in that: The method comprises the following steps: mixing the nano resin and the carbon-based mixture by air convection to obtain a mixture; spreading powder and pre-pressing to obtain a blank plate; and then hot-pressing the blank plate to obtain the carbon-plastic composite plate; The preparation steps of the nano resin are as follows: S1. Stir N-methylpyrrolidone and sodium sulfide at 150-180° C. for 20-40 min, add p-dichlorobenzene, p-dichlorobenzoic acid and sodium hydroxide, pass nitrogen, first heat to 200-240° C. and keep warm for 1-4 h, then heat to 260-280° C. and keep warm for 1-3 h, cool to room temperature, adjust pH to 5-7, wash, filter, and vacuum dry to obtain reactant 1; S2, under nitrogen protection, stirring dichloromethane, aluminum chloride and 3,6-di[9-carbazolyl]-9-phenylcarbazole at 30-60° C. for 12-17 hours, then adding the reactant 1 obtained in step S1 and stirring for 8-12 hours, cooling to room temperature and filtering, washing, recrystallizing and vacuum drying to obtain the nano resin; In step S1, the mass ratio of sodium sulfide to p-dichlorobenzene is 1:(0.73-0.98); In the step S2, the mass ratio of aluminum chloride, 3,6-di[9-carbazolyl]-9-phenylcarbazole and reactant 1 is (9.2-11.8):1:(8.71-10.05); The carbon-based mixture includes graphite, graphene and multi-walled carbon nanotubes.

2. The method for preparing the carbon-plastic composite plate according to claim 1, characterized in that: The specific operation of the hot pressing is: first hot pressing for 3-5 minutes at a hot plate temperature of 240-280°C and a pressure of 8-14MPa; then hot pressing for 2-4 minutes at a hot plate temperature of 180-220°C and a pressure of 15-22MPa; then at this temperature, molding the flow channel; finally cooling to room temperature and demolding.

3. The method for preparing the carbon-plastic composite plate according to claim 1, characterized in that: The particle size of the nano resin is 70-120nm.

4. The method for preparing the carbon-plastic composite plate according to claim 1, characterized in that: The mass ratio of the graphite, graphene and multi-walled carbon nanotubes is 1:(0.1-0.3):(0.05-0.25).

5. A carbon-plastic composite plate obtained by the preparation method according to any one of claims 1 to 4, characterized in that: The resistivity of the carbon-plastic composite plate is 1.6-3.4 mΩ.cm 2 .

6. A carbon-plastic composite electrode plate obtained by the preparation method according to any one of claims 1 to 4, and use of the carbon-plastic composite electrode plate according to claim 5 in a liquid flow battery.

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