A flow battery channel plate and its preparation method

Abstract

This invention discloses a flow battery channel plate and its preparation method. First, the invention pre-treats carbon fiber woven fabric or unidirectional carbon fiber filament fabric, then impregnates it in a resin solution, followed by drying and winding to obtain carbon fiber prepreg. Second, the invention uses an intercalation reaction to prepare expandable graphite, which is then expanded at high temperature to prepare worm graphite. The worm graphite is then pre-pressed and gradient rolled to obtain high-density graphite paper. Third, the invention performs surface resin spraying treatment on the carbon fiber prepreg and the perforated graphite paper, and then alternately lays the materials according to a basic structure of carbon fiber prepreg-graphite paper-carbon fiber prepreg, sequentially undergoing curing, carbonization, densification, and graphitization treatments to obtain the flow battery channel plate product. This invention combines the high corrosion resistance and stability of carbon-carbon composite materials with the high conductivity of graphite. This material does not have bubbling or swelling problems and can be used stably inside the battery.

Description

Technical Field

[0001] This invention relates to the field of flow batteries, and in particular to a flow battery flow channel plate and its preparation method. Background Technology

[0002] Currently, the flow plates used in flow batteries are made by intercalating natural flake graphite to create expandable graphite, which is then expanded, spread, rolled, and die-cut into graphite paper. Flow plates produced using this process are characterized by low cost, resistance to acid and alkali corrosion, and high conductivity. However, in the fuel cell stack, these graphite paper flow plates are susceptible to problems due to hydrogen evolution at the negative electrode and oxygen evolution at the positive electrode. Gases can seep into the graphite paper, and even electrolytes can seep in, causing the graphite paper to blister and swell. This leads to increased contact resistance between the flow plate and the electrode materials.

[0003] To address the aforementioned issues, two solutions exist: Solution 1 involves impregnating the manufactured graphite paper with resin, allowing the resin to permeate the graphite pores. Once the resin cures, it seals the pores, thus resolving the problems of bubbling and swelling in the graphite paper. Solution 2 utilizes isostatically pressed graphite, directly machining it into a flow channel structure. This type of material does not exhibit swelling or bubbling. However, both solutions have their own drawbacks. The resins selected in Solution 1 are mostly resistant to short- to medium-term acid, alkali, and electrolyte corrosion. Long-term exposure to acidic or alkaline environments or prolonged electrochemical corrosion can still affect them, maintaining the risk of bubbling and swelling. While the material itself in Solution 2 is not problematic, its molding requires wire sawing and machining, increasing the cost to 4-5 times that of conventional graphite paper, making it prohibitively expensive. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems, the present invention provides a flow battery channel plate and its preparation method.

[0005] In a first aspect, the present invention provides a method for preparing a flow battery channel plate, which is achieved through the following technical solution.

[0006] A method for preparing a flow channel plate for a flow battery includes the following steps:

[0007] S1. Preparation of carbon fiber substrate

[0008] a. Resin solution preparation: Add diluent and coupling agent to the resin in sequence, stir at 45℃-55℃ and then cool down to 25℃-35℃, add curing agent and continue stirring to obtain resin solution. The viscosity of the solution is controlled at 150mPa·s-500mPa·s, and allowed to stand to remove bubbles.

[0009] b. Substrate pretreatment: Dry the carbon fiber woven fabric or carbon fiber filament unidirectional fabric at 80℃-120℃; wherein, the areal density of the carbon fiber fabric is controlled at 50g / m². 2 -300g / m2 The tensile strength of a single filament is ≥3500MPa, and the tensile modulus is ≥230GPa;

[0010] c. Impregnation and quantity control: The pretreated substrate is passed through the impregnation tank at a uniform speed of 0.5m / min-2m / min. The temperature of the adhesive solution in the impregnation tank is maintained at 30℃-40℃, and the impregnation time of the substrate in the adhesive solution is controlled at 10s-30s. After impregnation, the substrate is extruded by rollers to control the quantity, resulting in a pre-impregnated blank with a resin content controlled at 30%-45%.

[0011] d. Drying and winding;

[0012] S2. Preparation of graphite paper

[0013] a. Preparation of expandable graphite by intercalation reaction: Flake graphite was mixed with a mixture of concentrated sulfuric acid and concentrated nitric acid at 10℃-30℃ with stirring. Potassium permanganate was added in batches, with the addition time controlled at 5min-15min, and the temperature was maintained at 20℃-40℃. The reaction was continued with stirring for 30min-90min. After the reaction was completed, hydrogen peroxide was added to terminate the reaction. After stirring, the mixture was filtered, washed, and dried to obtain expandable graphite.

[0014] b. Preparation of worm-shaped graphite by high-temperature expansion: Expandable graphite is continuously fed into a high-temperature expansion furnace, and the temperature inside the furnace is controlled at 900℃-1200℃. The graphite stays in the furnace for 10s-60s to obtain fluffy worm-shaped graphite.

[0015] c. Pre-compression molding: The worm graphite is loosened and dispersed, then evenly spread to a thickness of 5cm-20cm. Preliminary compaction is then performed at a pre-compression pressure of 0.1MPa-0.5MPa. After pre-compression, a foamed graphite preform with a thickness of 1cm-5cm is obtained, with a surface density controlled at 100g / m³. 2 -2000g / m 2 ;

[0016] d. High-density graphite paper preparation by multi-stage rolling: Foamed graphite preforms are subjected to gradient rolling, with a total of 3-5 rolling processes, ultimately resulting in high-density graphite paper with a density controlled at 1.3 g / cm³. 3 -1.8g / cm 3 ;

[0017] e. Post-processing and winding: The rolled graphite paper is impregnated in a sodium carboxymethyl cellulose aqueous solution with a mass concentration of 0.2%-1% for 5-20 seconds, dried, and then wound up.

[0018] S3. Carbon fiber graphite composite

[0019] a. Graphite paper pretreatment and perforation: The perforation diameter is controlled between 0.1mm and 5mm, the perforation spacing is controlled between 0.5mm and 20mm, and the porosity ranges from 5% to 30%.

[0020] b. Resin spraying pretreatment: The carbon fiber prepreg and the perforated graphite paper are subjected to surface resin spraying treatment, with the resin coating amount on one side of the graphite paper controlled at 10g / m². 2 -80g / m 2 The amount of resin applied to one side of the carbon fiber prepreg is controlled at 20g / m. 2 -150g / m 2 ;

[0021] c. Laying and high-pressure pressing: Lay out materials alternately according to the basic structure of carbon fiber prepreg - graphite paper - carbon fiber prepreg, with a total number of layers ranging from 2 to 20. After laying out the materials, press them together.

[0022] d. Curing treatment;

[0023] e. Carbonization treatment;

[0024] f. Densification treatment: Select chemical vapor infiltration or precursor impregnation pyrolysis process to densify the carbonized billet according to performance requirements;

[0025] g. Graphitization treatment: After the densified billet is sent into a high-temperature graphitization furnace for graphitization treatment, the finished flow battery flow channel plate is obtained.

[0026] Furthermore, in step S1a, the resin is selected from one or more of epoxy resin, phenolic resin, furan resin, and asphalt resin; the curing agent is selected from any one of amines and imidazoles, and the curing agent accounts for 0.5%-3% of the total mass of the resin; the diluent is selected from any one of acetone and anhydrous ethanol, and the diluent accounts for 1%-4% of the total mass of the resin; the coupling agent is selected from any one of silane coupling agents KH550 and KH560, and the coupling agent accounts for 0.2%-1.5% of the total mass of the resin; the total mass of the curing agent, diluent, and coupling agent accounts for 2%-8% of the total mass of the resin.

[0027] Furthermore, in step S1d, the prepreg fabric after impregnation is fed into a stepped drying oven, which is divided into three temperature control sections: the first section temperature is 60℃-80℃, and the dwell time is 2min-5min; the second section temperature is 90℃-110℃, and the dwell time is 3min-8min; the third section temperature is 50℃-70℃, and the dwell time is 1min-3min. After drying, the prepreg fabric is wound up after the tension roller is adjusted to 5N / m-20N / m, and the winding tightness is controlled to be ≤2mm per meter of roll diameter deviation.

[0028] Furthermore, in step S2a, the mass ratio of the raw materials used is as follows: 80%-92% natural flake graphite; 2%-10% concentrated sulfuric acid, 1%-5% concentrated nitric acid, 0.5%-3% potassium permanganate, and 0.3%-2% hydrogen peroxide.

[0029] Furthermore, in step S2d, the calendering process is as follows: First calendering: roll gap 1mm-8mm, rolling pressure 0.5MPa-2MPa, calendered thickness controlled at 1mm-5mm; Second calendering: roll gap 0.5mm-3mm, rolling pressure 2MPa-5MPa, calendered thickness controlled at 0.3mm-2mm; Third calendering: roll gap 0.1mm-1mm, rolling pressure 5MPa-15MPa, calendered thickness controlled at 0.1mm-0.8mm; If a higher density is required, 1-2 additional calendering passes are added, the roll gap is adjusted to 0.05mm-0.5mm, and the rolling pressure is 10MPa-25MPa.

[0030] Furthermore, in step S3b, the resin is any one of phenolic resin, epoxy resin, or furan resin, and the resin solid content is controlled at 30%-60%; the spraying pressure is controlled at 0.1MPa-0.8MPa, the distance between the spray gun and the substrate surface is controlled at 15cm-50cm, the spray gun moving speed is controlled at 5cm / s-30cm / s, and the spraying overlap rate is controlled at 30%-50%.

[0031] Furthermore, in step S3c, the pressing settings are as follows:

[0032] The pressing temperature is controlled by gradient heating: the initial temperature is 40℃-60℃, the heating rate is controlled at 1℃ / min-3℃ / min, the final pressing temperature is controlled at 80℃-180℃, and the pressing pressure is controlled at 5MPa-50MPa.

[0033] A stepped pressurization process is adopted: first, pressurize at a rate of 1MPa / min-5MPa / min to 30% of the set pressure, and maintain the temperature and pressure for 5min-20min; then continue to pressurize at a rate of 0.5MPa / min-2MPa / min to the set pressure, with the total pressing time controlled between 30min-120min.

[0034] Furthermore, in step S3d, the curing temperature range is 100℃-250℃, using a three-stage heating program: the first stage heats up to 100℃-120℃ at a rate of 1℃ / min-3℃ / min, and holds for 30min-90min; the second stage heats up to 150℃-180℃ at a rate of 0.5℃ / min-2℃ / min, and holds for 60min-180min; the third stage heats up to 200℃-250℃ at a rate of 0.5℃ / min-2℃ / min, and holds for 30min-120min; high-purity nitrogen or argon gas at 0.02MPa-0.1MPa is introduced throughout the curing process for protection, and the oxygen content in the furnace is ≤500ppm;

[0035] In step S3e, the carbonization temperature range is 800℃-1600℃, and the heating rate is controlled in stages: the heating rate is 0.5℃ / min-2℃ / min in the stage from room temperature to 600℃, and the heating rate is 2℃ / min-5℃ / min in the stage from 600℃ to the target temperature. After reaching the target temperature, the temperature is held for 60min-240min. The vacuum degree is controlled at 10Pa-1000Pa throughout the carbonization process, or high-purity nitrogen or argon gas with a flow rate of 0.5L / min-5L / min is introduced as a protective atmosphere, and the oxygen content in the furnace is ≤100ppm.

[0036] Furthermore, in step S3f, the CVI process densification parameters are as follows: the precursor is any one of methane, propylene, or natural gas; the carrier gas is hydrogen, nitrogen, or argon; the precursor to carrier gas flow rate ratio is controlled at 1:2-1:10; the total gas flow rate is controlled at 5L / min-50L / min; the furnace temperature is controlled at 900℃-1200℃; the furnace pressure is controlled at 1kPa-20kPa; the deposition time is controlled at 50h-200h; and the density of the billet after densification reaches 1.5g / cm³. 3 -2.2g / cm 3 ;

[0037] The density-enhancing parameters for the PIP process are as follows: The precursor is any one of phenolic resin, furan resin, or asphalt, with a solid content controlled between 30% and 70%. Before impregnation, the carbonized preform is placed in an impregnation tank and evacuated to 10 Pa to 1000 Pa, maintained for 10 to 60 minutes, then the precursor is injected, followed by a pressure of 1 MPa to 10 MPa. The impregnation time for each cycle is controlled between 1 hour and 10 hours. After impregnation, the preform is removed and subjected to curing and carbonization treatment, completing one impregnation-curing-carbonization cycle. This cycle is repeated until the preform density reaches 1.5 g / cm³. 3 -2.2g / cm 3 ;

[0038] In step S3g, the graphitization temperature is controlled between 1800℃ and 3000℃, and the heating rate is controlled in stages: the heating rate is 5℃ / min to 10℃ / min in the stage from room temperature to 1500℃, and the heating rate is 1℃ / min to 5℃ / min in the stage from 1500℃ to the target temperature. After reaching the target temperature, the temperature is held for 30min to 120min. The vacuum degree is controlled between 1Pa and 100Pa throughout the graphitization process, or high-purity argon gas is introduced for protection, and the pressure inside the furnace is 100Pa to 500Pa slightly positive pressure.

[0039] Secondly, the present invention provides a flow channel plate for a flow battery, which is achieved through the following technical solution.

[0040] A flow battery channel plate prepared by the above preparation method.

[0041] This application has the following beneficial effects:

[0042] This invention employs a composite process of carbon fiber fabric and graphite paper, which is then pressed together and integrally manufactured into a composite flow channel plate with high conductivity, high strength, and high corrosion resistance. It possesses the following characteristics:

[0043] 1. Combining the high corrosion resistance and stability of carbon-carbon composite materials with the high conductivity of graphite, it can be used stably in batteries. Due to the following two important factors in the process, the material does not have bubbling or swelling problems. The main reasons are: (1) Due to the perforation of the graphite paper layer, the carbon fibers on both sides of the graphite paper have been firmly formed into a whole by the resin carbon and the subsequent densified cracked carbon, locking the graphite paper from top to bottom and inhibiting its bubbling and swelling; (2) The graphite paper has a certain porosity. Through densification, cracked carbon will also seep into its pores, thereby filling the pores. Hydrogen, oxygen and electrolyte are difficult to enter, which also inhibits its bubbling and swelling.

[0044] 2. Due to the support of carbon fiber materials, the material has extremely high mechanical strength, with compressive strength > 200 MPa and tensile strength > 100 MPa, which greatly improves the assembly yield and efficiency;

[0045] 3. The material price is moderate to low, and the large-scale production equipment and processes can be industrialized, giving it good characteristics for industrial application. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the flow channel plate of the flow battery of the present invention. Detailed Implementation

[0047] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Before description, it should be understood that the terminology used in the specification and appended claims should not be construed as limited to its general and dictionary meaning, but rather should be interpreted based on the principle of allowing the inventors to appropriately define the terminology for the best interpretation, and based on its meaning and concept corresponding to the technical level of the invention. Therefore, the description herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention; thus, it should be understood that other equivalent implementations and modifications can be made without departing from the spirit and scope of the invention.

[0048] I. Preparation of carbon fiber base fabric:

[0049] 1. Raw materials and proportions

[0050] The raw materials used in this process and their mass ratio ranges are as follows:

[0051] (1) Reinforcing substrate: carbon fiber woven fabric or carbon fiber filament unidirectional fabric, with the substrate surface density controlled at 50 g / m². 2 -300g / m 2 The tensile strength of a single filament is ≥3500MPa, and the tensile modulus is ≥230GPa;

[0052] (2) Matrix resin: one or more of epoxy resin, phenolic resin, furan resin, and asphalt resin;

[0053] (3) Additives: 0.5%-3% curing agent, 1%-4% diluent, 0.2%-1.5% coupling agent, with the total mass of additives accounting for 2%-8% of the total mass of resin.

[0054] The curing agent is selected from any one of amines or imidazoles, the diluent is selected from any one of acetone or anhydrous ethanol, and the coupling agent is selected from any one of silane coupling agents KH550 or KH560.

[0055] 2. Preparation process flow

[0056] (1) Preparation of resin solution

[0057] Add the resin to the reactor, heat it to 40℃-100℃, control the stirring speed at 80r / min-150r / min, and stir for 10min-20min until the resin forms a completely flowable fluid.

[0058] Add the diluent and coupling agent in sequence, keep the temperature at 45℃-55℃, continue stirring for 15min-30min, then let it cool naturally to 25℃-35℃, add the curing agent and stir for 5min-10min to obtain a uniform resin solution without precipitation. Control the viscosity of the solution at 150mPa·s-500mPa·s, and let it stand for 5min-15min to remove bubbles before use.

[0059] (2) Substrate pretreatment

[0060] Carbon fiber cloth is sequentially fed into a drying oven, with the drying temperature controlled at 80℃-120℃ and the drying time at 10min-30min, to remove the moisture and organic impurities adsorbed on the surface of the substrate.

[0061] (3) Impregnation and quantity control

[0062] The pretreated substrate is passed through the impregnation tank at a uniform speed of 0.5m / min-2m / min. The temperature of the adhesive in the impregnation tank is maintained at 30℃-40℃. The impregnation time of the substrate in the adhesive is controlled at 10s-30s to ensure that the resin completely wets the fiber gaps.

[0063] After impregnation, the substrate is subjected to controlled extrusion by rollers with the roller gap controlled at 0.1mm-0.5mm and the roller surface pressure at 0.2MPa-0.8MPa to remove excess adhesive and obtain a prepreg blank with preliminary impregnation. At this time, the resin content of the blank is controlled at 30%-45%.

[0064] (4) Drying and winding

[0065] After impregnation, the prepreg blank is fed into a stepped drying oven, which is divided into three temperature control sections: the first section is 60℃-80℃, with a residence time of 2-5 minutes; the second section is 90℃-110℃, with a residence time of 3-8 minutes; and the third section is 50℃-70℃, with a residence time of 1-3 minutes. This ensures that the volatile content of the prepreg fabric is controlled at 1%-3%, and the resin curing degree reaches 5%-15%.

[0066] After drying, the prepreg fabric is naturally cooled to room temperature. After the tension is adjusted to 5N / m-20N / m by the tension roller, it is wound up. The winding tightness is controlled so that the deviation of the roll diameter per meter is ≤2mm.

[0067] II. Preparation of Graphite Paper:

[0068] 1. Raw materials and proportions

[0069] The raw materials used in this process and their mass ratio ranges are as follows:

[0070] (1) Main material: 80%-92% natural flake graphite, with graphite particle size controlled at 32-100 mesh and fixed carbon content ≥99%;

[0071] (2) Intercalation oxidant: 2%-10% of 98% concentrated sulfuric acid and 1%-5% of 65% concentrated nitric acid, with the mass ratio of the two controlled at 2-5:1;

[0072] (3) Intercalation aids: potassium permanganate 0.5%-3%, hydrogen peroxide 0.3%-2%, the total mass of the aids accounts for 1%-5% of the mass of graphite;

[0073] (4) Post-treatment agent: sodium carboxymethyl cellulose (CMC) aqueous solution with a mass concentration of 0.2%-1%.

[0074] 2. Preparation process flow

[0075] (1) Preparation of expandable graphite by intercalation reaction

[0076] Flake graphite is placed into a jacketed reactor. The reactor temperature is controlled at 10℃-30℃ and the stirring speed is 60r / min-120r / min. First, a mixture of concentrated sulfuric acid and concentrated nitric acid is added and stirred for 5min-10min until it is uniformly mixed.

[0077] Add potassium permanganate in batches, controlling the feeding time to 5-15 minutes, maintaining the temperature at 20℃-40℃, and continue stirring and reacting for 30-90 minutes.

[0078] After the reaction is complete, hydrogen peroxide is added to terminate the reaction. After stirring for 3-8 minutes, the mixture is filtered and washed with deionized water until the pH of the filtrate is 3-6. The filter cake is then dried at 50℃-80℃ for 10-30 minutes to obtain expandable graphite, with its expansion volume controlled at 200mL / g-400mL / g.

[0079] (2) Preparation of worm graphite by high temperature expansion

[0080] Expandable graphite is continuously fed into a high-temperature expansion furnace, with the furnace temperature controlled at 900℃-1200℃. The graphite stays in the furnace for 10s-60s, allowing the intercalated material to rapidly vaporize and decompose, resulting in fluffy worm-like graphite.

[0081] The expanded worm graphite was naturally cooled to room temperature, and incompletely expanded graphite particles and impurities were removed by air classification. The bulk density of the worm graphite was controlled at 2g / L-8g / L, and the length ranged from 0.5mm to 5mm.

[0082] (3) Pre-compression molding

[0083] The worm graphite is fed into an opening machine for opening treatment. The opening speed is 1000r / min-1800r / min and the opening time is 30s-120s, so that the worm graphite fibers are completely dispersed without agglomeration.

[0084] The dispersed worm graphite is evenly spread on a conveyor belt, with a thickness controlled between 5cm and 20cm. It is then fed into a pre-compressor for preliminary compaction at a pressure of 0.1MPa to 0.5MPa. After pre-compression, a foamed graphite preform with a thickness of 1cm to 5cm is obtained, with a surface density controlled at 100g / m³.2 -2000g / m 2 .

[0085] (4) Preparation of high-density graphite paper by multi-pass rolling

[0086] The foamed graphite preform is fed into a multi-roll calender for gradient rolling, with a total of 3 to 5 rolling processes:

[0087] First calendering: roll gap 1mm-8mm, roll pressure 0.5MPa-2MPa, thickness after calendering controlled at 1mm~5mm;

[0088] The second calendering process involves a roll gap of 0.5mm-3mm, a roll pressure of 2MPa-5MPa, and a final thickness of 0.3mm-2mm.

[0089] The third calendering process: roll gap 0.1mm-1mm, roll pressure 5MPa-15MPa, and the thickness after calendering is controlled at 0.1mm-0.8mm;

[0090] For higher density, one or two additional calendering passes can be added, adjusting the roll gap to 0.05mm-0.5mm and the roll pressure to 10MPa-25MPa, ultimately yielding high-density graphite paper with a density controlled at 1.3g / cm³. 3 -1.8g / cm 3 .

[0091] (5) Post-processing and winding

[0092] After being rolled, the graphite paper is fed into a surface treatment tank and impregnated with a sodium carboxymethyl cellulose aqueous solution with a mass concentration of 0.2%-1% for 5-20 seconds. Then it is put into a drying oven and dried at 80℃-120℃ for 5-15 minutes to improve the surface strength and flexibility of the graphite paper.

[0093] After drying, the graphite paper is allowed to cool naturally to room temperature. The uneven edges are removed by an edge trimmer, and the winding tension is adjusted to 10N / m-30N / m before winding.

[0094] III. Carbon fiber and graphite composite

[0095] 1. Graphite paper pretreatment and perforation

[0096] High-density graphite paper is flattened and fixed onto the vacuum worktable of a CNC drilling machine, ensuring a wrinkle-free and curled surface. The array drilling mode is then selected based on application performance requirements.

[0097] The hole diameter is controlled between 0.1mm and 5mm, the hole spacing is controlled between 0.5mm and 20mm, the porosity is between 5% and 30%, and the hole shape can be round, square or irregular. The coaxiality deviation of the channel is ≤ ±0.05mm.

[0098] The punch is made of hard alloy or diamond-coated material, the rotation speed is controlled at 1000r / min-5000r / min, the axial feed speed is controlled at 5mm / s-50mm / s, and the single punching depth error is ≤±0.02mm.

[0099] After drilling, use clean compressed air at 0.2MPa-0.5MPa to blow the graphite paper at a 45° angle to both sides 2-5 times each to remove residual graphite debris from the holes. The surface debris residue should be ≤0.1g / m². 2 The sampling test showed that the pore permeability was ≥99.5%.

[0100] 2. Resin spraying pretreatment

[0101] Carbon fiber prepreg and perforated graphite paper were coated with resin on their surfaces. The spraying environment temperature was controlled at 18℃-28℃, the relative humidity was controlled at 30%-60%, and the cleanliness of the spraying area was ≥100,000.

[0102] The resin used can be any one of phenolic resin, epoxy resin or furan resin, and the resin solid content is controlled at 30%-60%. 0.1%-1% of silane coupling agent (any one of silane coupling agents KH550 or KH560) can be added to improve the interfacial bonding force.

[0103] The spraying process uses an air atomizing spray gun, with the spraying pressure controlled at 0.1MPa-0.8MPa, the distance between the spray gun and the substrate surface controlled at 15cm-50cm, the spray gun moving speed controlled at 5cm / s-30cm / s, and the spray overlap rate controlled at 30%-50%.

[0104] The amount of resin sizing applied to one side of the graphite paper should be controlled at 10g / m². 2 -80g / m 2 The amount of resin applied to one side of the carbon fiber prepreg is controlled at 20g / m. 2 -150g / m 2 The uniformity of adhesive application on the same substrate is ≤±5%;

[0105] After spraying, place the substrate in a stepped heating oven for pre-drying. First, place it at 40℃~50℃ for 2min~10min, then raise the temperature to 60℃~80℃ and keep it for 3min~20min until the resin surface is semi-dry and not sticky. The overall volatile content of the substrate should be controlled at 3%~10%.

[0106] 3. Layered material laying and high-pressure pressing

[0107] The materials are laid alternately according to the basic structure of "carbon fiber prepreg - graphite paper - carbon fiber prepreg", with a total number of layers ranging from 2 to 20. The ratio of graphite paper to carbon fiber prepreg can be adjusted according to performance requirements. The top and bottom layers must be carbon fiber prepreg. The alignment deviation of the materials is ≤ ±0.5mm. After the materials are laid, they are sent to a flatbed press for pressing.

[0108] The pressing temperature is controlled by gradient heating. The initial temperature is 40℃-60℃, the heating rate is controlled at 1℃ / min-3℃ / min, the final pressing temperature is controlled at 80℃-180℃, and the pressing pressure is controlled at 5MPa-50MPa.

[0109] A stepped pressurization process is adopted: first, pressurize at a rate of 1MPa / min-5MPa / min to 30% of the set pressure, hold for 5min-20min to remove residual gas between layers; then continue to pressurize at a rate of 0.5MPa / min-2MPa / min to the set pressure, with the total pressing time controlled between 30min-120min.

[0110] After pressing, the press's circulating water cooling system is turned on, and the plate temperature is cooled to below 40℃ at a rate of 1℃ / min-3℃ / min. Then the mold is opened and the pressure is released to obtain the composite blank. The overall thickness deviation of the blank is ≤±8%, and the interlayer bonding force is ≥5N / mm.

[0111] 4. Curing treatment

[0112] The pressed composite blank is then sent to a programmed temperature curing oven for curing, ensuring that the blank is not deformed by external force throughout the curing process.

[0113] The curing temperature range is 100℃-250℃, using a three-stage heating program: the first stage heats up to 100℃-120℃ at a rate of 1℃ / min-3℃ / min, and holds for 30min-90min to allow the resin to fully level; the second stage heats up to 150℃-180℃ at a rate of 0.5℃ / min-2℃ / min, and holds for 60min-180min to complete the resin crosslinking reaction; the third stage heats up to 200℃-250℃ at a rate of 0.5℃ / min-2℃ / min, and holds for 30min-120min to remove residual small molecule substances.

[0114] The entire curing process is protected by high-purity nitrogen or argon gas at 0.02MPa-0.1MPa, and the oxygen content in the furnace is ≤500ppm to avoid high-temperature oxidation of the resin.

[0115] After curing, the cured blank is cooled to room temperature in the oven and then removed. The cured blank is tested according to GB / T 2567 standard and the degree of resin curing is ≥90%, with no appearance defects such as delamination or bubbling.

[0116] 5. Carbonization treatment

[0117] The cured blank is fed into a vacuum carbonization furnace for carbonization. The blank is vertically clamped using graphite clamps, with the loading gap controlled at 5mm-20mm to ensure uniform atmosphere flow.

[0118] The carbonization temperature range is 800℃-1600℃, and the heating rate is controlled in stages: the heating rate is 0.5℃ / min-2℃ / min in the stage from room temperature to 600℃, the heating rate is 2℃ / min-5℃ / min in the stage from 600℃ to the target temperature, and the temperature is held for 60min-240min after reaching the target temperature.

[0119] Throughout the carbonization process, the vacuum level inside the furnace is controlled at 10Pa-1000Pa, or high-purity nitrogen or argon gas with a flow rate of 0.5L / min-5L / min is introduced as a protective atmosphere, and the oxygen content inside the furnace is ≤100ppm.

[0120] After carbonization, the material is cooled to room temperature in the furnace to obtain a carbonized billet. The carbonization yield is controlled at 50%-80%, the open porosity is controlled at 10%-30%, and there are no defects such as cracking or deformation.

[0121] 6. Densification treatment

[0122] Depending on performance requirements, chemical vapor infiltration (CVI) or precursor impregnation pyrolysis (PIP) processes are selected to densify the carbonized billet until the billet density reaches the target requirement.

[0123] (1) CVI process densification

[0124] The precursor is selected from methane, propylene or natural gas, and the carrier gas is hydrogen, nitrogen or argon. The flow ratio of the precursor to the carrier gas is controlled at 1:2-1:10, and the total ventilation flow rate is controlled at 5L / min-50L / min.

[0125] The furnace temperature is controlled at 900℃-1200℃, the furnace pressure is controlled at 1kPa-20kPa, and the deposition time is controlled at 50h-200h. The process parameters can be adjusted in stages according to the density growth.

[0126] Density was measured every 20-40 hours, and the density of the billet reached 1.5 g / cm³ after densification. 3 -2.2g / cm 3 This will stop the deposition process.

[0127] (2) PIP process densification

[0128] The precursor is selected from any one of phenolic resin, furan resin or asphalt. The solid content of the precursor is controlled at 30%-70%. Before impregnation, the carbonized blank is placed in the impregnation tank and vacuumed to 10Pa~1000Pa. After maintaining the vacuum for 10min-60min, the precursor is injected and then a pressure of 1MPa-10MPa is applied. The single impregnation time is controlled at 1h-10h.

[0129] After impregnation, the blank is removed, excess precursor on the surface is removed, and it is processed sequentially according to the aforementioned curing and carbonization process parameters to complete one impregnation-curing-carbonization cycle.

[0130] After each cycle, the billet density is measured. This process is repeated 3 to 10 times until the billet density reaches 1.5 g / cm³. 3 -2.2g / cm 3 Stop increasing density.

[0131] 7. Graphitization treatment

[0132] The densified billet is then fed into a high-temperature graphitization furnace for graphitization treatment.

[0133] The graphitization temperature is controlled between 1800℃ and 3000℃, and the heating rate is controlled in stages: the heating rate is 5℃ / min to 10℃ / min in the stage from room temperature to 1500℃, and the heating rate is 1℃ / min to 5℃ / min in the stage from 1500℃ to the target temperature. After reaching the target temperature, the temperature is held for 30min to 120min.

[0134] Throughout the graphitization process, the vacuum level inside the furnace is controlled at 1Pa-100Pa, or high-purity argon gas is introduced for protection, and the pressure inside the furnace is slightly positive (100Pa-500Pa) to prevent air from seeping in and causing material oxidation.

[0135] After graphitization, the material is cooled to room temperature in the furnace to obtain graphitized composite components. The degree of graphitization is controlled at 60%-95% according to GB / T 3074.3 standard.

[0136] 8. Post-processing and finished product preparation

[0137] After graphitization, the composite components undergo 100% visual inspection to remove defective parts such as surface blistering, cracking, and delamination. Core properties such as density, tensile strength, thermal conductivity, and resistivity are then sampled and tested according to standards such as GB / T 3074.1, GB / T 8722, and GB / T 1551, with a batch pass rate ≥90%.

[0138] Components that meet performance requirements are die-cut into shape using a CNC die-cutting machine according to customer drawings. Carbide or diamond tools are used for die-cutting, and the die-cutting pressure is controlled between 10MPa and 100MPa. The die-cutting size deviation is ≤ ±0.1mm, and the edge burr height is ≤ 0.05mm.

[0139] After die-cutting, surface impurities are blown away with clean compressed air at 0.1MPa-0.3MPa. After passing the random inspection, the product is sealed in a moisture-proof vacuum bag.

[0140] IV. Testing

[0141] 1. Material flatness: ≤±0.05mm;

[0142] 2. Conductivity: ≥200 S / cm;

[0143] 3. Compressive strength: ≥200 MPa, tensile strength: ≥100 MPa;

[0144] 4. At a value not lower than 300mA / cm 2 At the specified current density, after more than 2000 cycles, there was no swelling or bubbling.

[0145] Example 1

[0146] I. Preparation of carbon fiber base fabric:

[0147] 1. Raw materials and proportions

[0148] The raw materials used in this process and their mass ratio ranges are as follows:

[0149] (1) Reinforcing substrate: unidirectional carbon fiber filament fabric with a surface density of 300 g / m 2 The tensile strength of a single filament is 3500 MPa, and the tensile modulus is 230 GPa.

[0150] (2) Matrix resin: Shandong Shengquan 9701 phenolic resin (60% residual carbon content);

[0151] (3) Additives: 1% curing agent, 2% diluent, 1% coupling agent, with the total mass of additives accounting for 4% of the total mass of resin.

[0152] Among them, the curing agent is hexamethylenetetramine, the diluent is anhydrous ethanol, and the coupling agent is selected from silane coupling agent KH550.

[0153] 2. Preparation process flow

[0154] (1) Preparation of resin solution

[0155] Add the resin to the reactor, heat it to 60°C, control the stirring speed at 100r / min, and stir for 10min until the resin forms a completely flowable fluid.

[0156] Add the diluent and coupling agent in sequence, keep the temperature at 50℃, continue stirring for 20 minutes, then let it cool naturally to 25℃, add the curing agent and stir for 5 minutes to obtain a uniform resin solution without precipitation. The viscosity of the solution is controlled at 200 mPa·s. Let it stand for 15 minutes to remove bubbles before use.

[0157] (2) Substrate pretreatment

[0158] The carbon fiber cloth is fed into the drying oven in sequence. The drying temperature is controlled at 110℃ and the drying time is 10 minutes to remove the moisture and organic impurities adsorbed on the surface of the substrate.

[0159] (3) Impregnation and quantity control

[0160] The pretreated substrate is passed through the impregnation tank at a uniform speed of 1m / min. The temperature of the adhesive in the impregnation tank is maintained at 30℃. The immersion time of the substrate in the adhesive is controlled at 20s to ensure that the resin completely wets the fiber gaps.

[0161] After impregnation, the substrate is subjected to controlled extrusion by rollers with the roller gap controlled at 0.2 mm and the roller surface pressure at 0.5 MPa to remove excess adhesive, resulting in a pre-impregnated blank with a resin content of 40%.

[0162] (4) Drying and winding

[0163] The prepreg blanks after impregnation are fed into a stepped drying oven, which is divided into three temperature control sections: the first section is 60℃ and the residence time is 2 minutes; the second section is 90℃ and the residence time is 3 minutes; the third section is 50℃ and the residence time is 1 minute, so that the volatile content of the prepreg fabric is controlled at 3% and the resin curing degree reaches 10%.

[0164] After drying, the prepreg is naturally cooled to room temperature. After passing through a tension roller to adjust the tension to 10 N / m, it is wound up. The winding tightness is controlled within 1 mm per meter of roll diameter.

[0165] II. Preparation of Graphite Paper:

[0166] 1. Raw materials and proportions

[0167] The raw materials used in this process and their mass ratio ranges are as follows:

[0168] (1) Main material: 90% natural flake graphite, with graphite particle size controlled at 80 mesh and fixed carbon content ≥99%;

[0169] (2) Intercalation oxidizing agent: 4% concentrated sulfuric acid, 1% concentrated nitric acid;

[0170] (3) Intercalation aids: 3% potassium permanganate and 1% hydrogen peroxide, with the total mass of the aids accounting for 4% of the graphite mass;

[0171] (4) Post-treatment agent: 0.8% sodium carboxymethyl cellulose aqueous solution.

[0172] 2. Preparation process flow

[0173] (1) Preparation of expandable graphite by intercalation reaction

[0174] Flake graphite is placed into a jacketed reactor, the reactor temperature is controlled at 30℃, the stirring speed is 100r / min, and a mixture of concentrated sulfuric acid and concentrated nitric acid is added and stirred for 5min to mix evenly.

[0175] Add potassium permanganate in batches, controlling the feeding time to 5 minutes, maintaining the temperature at 25°C, and continue stirring and reacting for 30 minutes.

[0176] After the reaction is complete, hydrogen peroxide is added to terminate the reaction. After stirring for 3 minutes, the mixture is filtered and washed with deionized water until the pH of the filtrate is 6. The filter cake is then dried at 60°C for 20 minutes to obtain expandable graphite, with its expansion volume controlled at 300 mL / g.

[0177] (2) Preparation of worm graphite by high temperature expansion

[0178] Expandable graphite is continuously fed into a high-temperature expansion furnace, the furnace temperature is controlled at 1050℃, and the graphite stays in the furnace for 50 seconds to rapidly vaporize and decompose the intercalated material, resulting in fluffy worm-like graphite.

[0179] The expanded worm graphite was naturally cooled to room temperature, and incompletely expanded graphite particles and impurities were removed by air classification. The bulk density of the worm graphite was controlled at 6 g / L, and the length ranged from 1 mm to 3 mm.

[0180] (3) Pre-compression molding

[0181] The worm graphite is fed into an opening machine for opening treatment at a speed of 1200 r / min for 60 s to completely disperse the worm graphite fibers without clumping.

[0182] The dispersed worm graphite is evenly spread on a conveyor belt with a thickness controlled at 10cm. It is then fed into a pre-compressor for preliminary compaction at a pressure of 0.3MPa. After pre-compression, a 3cm thick foamed graphite preform is obtained with a surface density controlled at 700g / m³. 2 .

[0183] (4) Preparation of high-density graphite paper by multi-pass rolling

[0184] The foamed graphite preform is fed into a multi-roll calender for gradient rolling, with a total of 4 rolling processes:

[0185] First calendering: roll gap 2mm, roll pressure 0.5MPa, thickness controlled at 2.5mm after calendering;

[0186] Second calendering: roll gap 1mm, roll pressure 2MPa, thickness controlled at 1.5mm after calendering;

[0187] The third calendering process: roll gap 0.5mm, roll pressure 5MPa, and the thickness after calendering is controlled at 0.6mm;

[0188] Fourth calendering: roll gap 0.4mm, roll pressure 10MPa, thickness controlled at 0.5mm after calendering;

[0189] Its density is controlled at 1.4 g / cm³. 3 .

[0190] (5) Post-processing and winding

[0191] The rolled graphite paper is fed into a surface treatment tank and impregnated with a sodium carboxymethyl cellulose aqueous solution with a mass concentration of 0.8% for 20 seconds. Then it is put into a drying oven and dried at 90°C for 15 minutes to improve the surface strength and flexibility of the graphite paper.

[0192] After drying, the graphite paper is allowed to cool naturally to room temperature. The uneven edges are removed by an edge trimmer, and the winding tension is adjusted to 10 N / m before winding.

[0193] III. Carbon fiber and graphite composite

[0194] 1. Graphite paper pretreatment and perforation

[0195] High-density graphite paper is flattened and fixed onto the vacuum worktable of a CNC drilling machine, ensuring a wrinkle-free and curled surface. The array drilling mode is then selected based on application performance requirements.

[0196] The hole diameter is controlled at 0.3mm, the hole spacing is controlled at 10mm, the porosity range is 30%, the hole shape is circular, and the coaxiality deviation of the channel is ±0.05mm.

[0197] The punch is made of carbide, with a rotation speed controlled at 1000 r / min, an axial feed speed controlled at 20 mm / s, and a single punch depth error of ±0.02 mm.

[0198] After drilling, clean compressed air at 0.2 MPa is used to blow the graphite paper three times on each side at a 45° angle to remove residual graphite debris from the holes. The surface debris residue should be ≤0.1 g / m². 2 The sampling test showed that the pore permeability was ≥99.5%.

[0199] 2. Resin spraying pretreatment

[0200] Carbon fiber prepreg and perforated graphite paper were coated with resin on their surfaces. The spraying environment temperature was controlled at 25℃, the relative humidity was controlled at 50%, and the cleanliness of the spraying area was 100,000.

[0201] The resin used is Shandong Shengquan 9701 phenolic resin, with the resin solid content controlled at 50%. 0.8% of the resin mass is added as silane coupling agent KH550 to improve interfacial bonding.

[0202] The spraying process uses an air atomizing spray gun, with the spraying pressure controlled at 0.3 MPa, the distance between the spray gun and the substrate surface controlled at 20 cm, the spray gun moving speed controlled at 5 cm / s, and the spray overlap rate controlled at 30%.

[0203] The amount of resin sizing applied to one side of the graphite paper should be controlled at 50g / m². 2 The amount of resin applied to one side of the carbon fiber prepreg is controlled at 100g / m. 2 The uniformity of adhesive application on the same substrate is within ±5%.

[0204] After spraying, place the substrate in a stepped heating oven for pre-drying. First, place it at 40℃ for 5 minutes, then raise the temperature to 80℃ and keep it for 10 minutes until the resin surface is semi-dry and not sticky. The overall volatile content of the substrate is controlled at 5%.

[0205] 3. Layered material laying and high-pressure pressing

[0206] The materials are laid alternately according to the basic structure of "carbon fiber prepreg - graphite paper - carbon fiber prepreg", with a total of 5 layers. The alignment deviation of the materials is ≤ ±0.5mm. After the materials are laid, they are sent to a flatbed press for pressing.

[0207] The pressing temperature is controlled by gradient heating. The initial temperature is 60℃, the heating rate is controlled at 1℃ / min, the final pressing temperature is controlled at 180℃, and the pressing pressure is controlled at 20MPa.

[0208] A stepped pressurization process is adopted: first, pressurize to 30% of the set pressure at a rate of 5 MPa / min, hold for 5 minutes to remove residual gas between layers; then continue to pressurize to the set pressure at a rate of 1 MPa / min, with the total pressing time controlled at 60 minutes.

[0209] After pressing, the press's circulating water cooling system is turned on to cool the platen to below 40°C at a rate of 2°C / min. Then the mold is opened and the pressure is released to obtain the composite blank. The overall thickness deviation of the blank is ±5%, and the interlayer bonding force is ≥10N / mm.

[0210] 4. Curing treatment

[0211] The pressed composite blank is sent into a programmed temperature curing oven for curing treatment, and the blank is prevented from being deformed by external force throughout the curing process.

[0212] The curing temperature range is 100℃-250℃, and a three-stage heating program is adopted: the first stage heats up to 100℃ at a rate of 2℃ / min and holds for 30min to allow the resin to fully level; the second stage heats up to 150℃ at a rate of 1℃ / min and holds for 60min to complete the resin crosslinking reaction; the third stage heats up to 250℃ at a rate of 0.5℃ / min and holds for 30min to remove residual small molecule substances.

[0213] The entire curing process is protected by high-purity nitrogen gas at 0.05MPa, and the oxygen content in the furnace is ≤300ppm to avoid high-temperature oxidation of the resin.

[0214] After curing, the cured blank is cooled to room temperature in the oven and then removed. The cured blank is tested according to GB / T 2567 standard and the degree of resin curing is ≥90%, with no appearance defects such as delamination or bubbling.

[0215] 5. Carbonization treatment

[0216] The solidified blank is fed into a vacuum carbonization furnace for carbonization. The blank is vertically clamped using graphite clamps, and the loading gap is controlled at 5mm to ensure uniform atmosphere flow.

[0217] The carbonization temperature is 1200℃, and the heating rate is controlled in stages: the heating rate is 1℃ / min in the stage from room temperature to 600℃, and the heating rate is 2℃ / min in the stage from 600℃ to 1200℃. After reaching the target temperature, the temperature is held for 60 minutes.

[0218] High-purity argon gas with a flow rate of 0.5 L / min is introduced into the furnace as a protective atmosphere throughout the carbonization process, and the oxygen content in the furnace is ≤100 ppm;

[0219] After carbonization, the material is cooled to room temperature in the furnace to obtain a carbonized billet. The carbonization yield is controlled at 60%, the open porosity is controlled at 30%, and there are no defects such as cracking or deformation.

[0220] 6. Densification treatment: PIP process for densification

[0221] The precursor is Shandong Shengquan 9701 phenolic resin. The solid content of the precursor is controlled at 50%. Before impregnation, the carbonized preform is placed in the impregnation tank and vacuumed to 1000Pa. After maintaining this for 60 minutes, the precursor is injected and then a pressure of 3MPa is applied. The single impregnation time is controlled at 2 hours.

[0222] After impregnation, the blank is removed, excess precursor on the surface is removed, and it is processed sequentially according to the aforementioned curing and carbonization process parameters to complete one impregnation-curing-carbonization cycle.

[0223] After each cycle, the billet density is measured. This process is repeated three times until the billet density reaches 1.5 g / cm³. 3 Stop increasing density.

[0224] 7. Graphitization treatment

[0225] The densified billet is then fed into a high-temperature graphitization furnace for graphitization treatment.

[0226] The graphitization temperature was controlled at 2100℃, and the heating rate was controlled in stages: the heating rate was 5℃ / min in the stage from room temperature to 1500℃, and the heating rate was 2℃ / min in the stage from 1500℃ to the target temperature. After reaching the target temperature, the temperature was held for 60 minutes.

[0227] High-purity argon gas is introduced into the furnace for protection throughout the graphitization process, and the furnace pressure is a slightly positive pressure of 300Pa to prevent air from seeping in and causing material oxidation.

[0228] After graphitization, the material is cooled to room temperature in the furnace to obtain a graphitized composite component. The degree of graphitization is controlled at 95% according to GB / T 3074.3 standard.

[0229] 8. Post-processing and finished product preparation

[0230] After graphitization, the composite components undergo 100% visual inspection to remove defective parts such as surface blistering, cracking, and delamination. Core properties such as density, tensile strength, thermal conductivity, and resistivity are then sampled and tested according to standards such as GB / T 3074.1, GB / T 8722, and GB / T 1551. The thickness is 1.8-1.85 mm, and the batch pass rate is ≥90%.

[0231] Components that meet performance requirements are die-cut into shape using a CNC die-cutting machine according to customer drawings. Carbide or diamond tools are used for die-cutting, the die-cutting pressure is controlled at 20MPa, the die-cutting size deviation is ±0.1mm, and the edge burr height is 0.05mm.

[0232] After die-cutting, surface impurities are blown away with 0.2MPa clean compressed air. After passing the random inspection, the product is sealed in a moisture-proof vacuum bag.

[0233] IV. Test Results

[0234] 1. Material flatness: ±0.05mm;

[0235] 2. Conductivity: 200-300 S / cm;

[0236] 3. Compressive strength: 210-230 MPa, tensile strength: 100-120 MPa;

[0237] 4. At 300mA / cm 2 At a current density of 48 cm², the reaction area is 48 cm². 2 Using a full vanadium electrolyte, after 2000 cycles, there was no swelling or foaming.

[0238] Example 2

[0239] I. Preparation of carbon fiber base fabric:

[0240] 1. Raw materials and proportions

[0241] The raw materials used in this process and their mass ratio ranges are as follows:

[0242] (1) Reinforcing substrate: carbon fiber woven fabric, with the substrate surface density controlled at 100 g / m². 2 The tensile strength of a single filament is 4000±500MPa, and the tensile modulus is 260±30GPa.

[0243] (2) Matrix resin: Shandong Shengquan dicyclopentadiene phenol epoxy resin;

[0244] (3) Additives: 2% curing agent, 1% diluent, 1% coupling agent, with the total mass of additives accounting for 4% of the total mass of resin.

[0245] Among them, the curing agent is m-phenylenediamine, the diluent is acetone, and the coupling agent is selected from silane coupling agent KH560.

[0246] 2. Preparation process flow

[0247] (1) Preparation of resin solution

[0248] Add the resin to the reactor, heat it to 60°C, control the stirring speed at 120r / min, and stir for 15min until the resin forms a completely flowable fluid.

[0249] Add the diluent and coupling agent in sequence, keep the temperature at 50℃, continue stirring for 15 minutes, then let it cool naturally to 25℃, add the curing agent and stir for 10 minutes to obtain a uniform resin solution without precipitation. The viscosity of the solution is controlled at 200 mPa·s. Let it stand for 10 minutes to remove bubbles before use.

[0250] (2) Substrate pretreatment

[0251] The carbon fiber cloth is fed into the drying oven in sequence. The drying temperature is controlled at 110℃ and the drying time is 20 minutes to remove the moisture and organic impurities adsorbed on the surface of the substrate.

[0252] (3) Impregnation and quantity control

[0253] The pretreated substrate is passed through the impregnation tank at a uniform speed of 2m / min. The temperature of the adhesive in the impregnation tank is maintained at 40℃. The immersion time of the substrate in the adhesive is controlled at 30s to ensure that the resin completely wets the fiber gaps.

[0254] After impregnation, the substrate is subjected to controlled extrusion by rollers with the roller gap controlled at 0.1 mm and the roller surface pressure at 0.5 MPa to remove excess adhesive, resulting in a pre-impregnated blank with a resin content of 30%.

[0255] (4) Drying and winding

[0256] The prepreg blanks after resin impregnation are fed into a stepped drying oven, which has three temperature control sections: the first section is 80℃ for 2 minutes; the second section is 110℃ for 3 minutes; and the third section is 70℃ for 1 minute, so that the volatile content of the prepreg fabric is controlled at 1% and the resin curing degree reaches 15%.

[0257] After drying, the prepreg fabric is naturally cooled to room temperature. After passing through a tension roller and adjusting the tension to 20 N / m, it is wound up. The winding tightness is controlled so that the deviation of the roll diameter per meter is ≤2 mm.

[0258] II. Preparation of Graphite Paper:

[0259] 1. Raw materials and proportions

[0260] The raw materials used in this process and their mass ratio ranges are as follows:

[0261] (1) Main material: 92% natural flake graphite, with graphite particle size controlled at 100 mesh and fixed carbon content ≥99%;

[0262] (2) Intercalation oxidizing agent: 2% concentrated sulfuric acid, 1% concentrated nitric acid;

[0263] (3) Intercalation aids: 3% potassium permanganate and 1% hydrogen peroxide, with the total mass of the aids accounting for 4% of the graphite mass;

[0264] (4) Post-treatment agent: 1% sodium carboxymethyl cellulose aqueous solution.

[0265] 2. Preparation process flow

[0266] (1) Preparation of expandable graphite by intercalation reaction

[0267] Flake graphite is placed into a jacketed reactor, the reactor temperature is controlled at 30℃, the stirring speed is 120r / min, and a mixture of concentrated sulfuric acid and concentrated nitric acid is added and stirred for 10min to mix evenly.

[0268] Add potassium permanganate in batches, control the feeding time to 15 minutes, keep the temperature at 40℃, and continue stirring and reacting for 60 minutes.

[0269] After the reaction is complete, hydrogen peroxide is added to terminate the reaction. After stirring for 5 minutes, the mixture is filtered and washed with deionized water until the pH of the filtrate is 6. The filter cake is then dried at 80°C for 30 minutes to obtain expandable graphite, with its expansion volume controlled at 200 mL / g.

[0270] (2) Preparation of worm graphite by high temperature expansion

[0271] Expandable graphite is continuously fed into a high-temperature expansion furnace, the furnace temperature is controlled at 1200℃, and the graphite stays in the furnace for 60 seconds to rapidly vaporize and decompose the intercalated material, resulting in fluffy worm-like graphite.

[0272] The expanded worm graphite was naturally cooled to room temperature, and incompletely expanded graphite particles and impurities were removed by air classification. The bulk density of the worm graphite was controlled at 6 g / L, and the length ranged from 2 mm to 5 mm.

[0273] (3) Pre-compression molding

[0274] The worm graphite is fed into an opening machine for opening treatment. The opening speed is 1500r / min and the opening time is 90s, so that the worm graphite fibers are completely dispersed without clumps.

[0275] The dispersed worm graphite is evenly spread on a conveyor belt with a thickness controlled at 10cm. It is then fed into a pre-compressor for preliminary compaction at a pressure of 0.5MPa. After pre-compression, a foamed graphite preform with a thickness of 1cm and a surface density controlled at 300g / m³ is obtained. 2 .

[0276] (4) Preparation of high-density graphite paper by multi-pass rolling

[0277] The foamed graphite preform is fed into a multi-roll calender for gradient rolling, with a total of 5 calendering processes:

[0278] First calendering: roll gap 2mm, roll pressure 0.5MPa, thickness controlled at 2.5mm after calendering;

[0279] Second calendering: roll gap 1mm, roll pressure 2MPa, thickness controlled at 1.5mm after calendering;

[0280] The third calendering process: roll gap 0.5mm, roll pressure 5MPa, and the thickness after calendering is controlled at 0.5mm;

[0281] Fourth calendering: roll gap 0.25mm, roll pressure 10MPa, thickness controlled at 0.25mm after calendering;

[0282] Fifth calendering: roll gap 0.2mm, roll pressure 15MPa, thickness controlled at 0.2mm after calendering;

[0283] Density controlled at 1.5 g / cm³ 3 .

[0284] (5) Post-processing and winding

[0285] The rolled graphite paper is fed into a surface treatment tank and impregnated with a 1% sodium carboxymethyl cellulose aqueous solution for 20 seconds. Then it is put into a drying oven and dried at 80°C for 15 minutes to improve the surface strength and flexibility of the graphite paper.

[0286] After drying, the graphite paper is allowed to cool naturally to room temperature. The uneven edges are removed by an edge trimmer, and the winding tension is adjusted to 10 N / m before winding.

[0287] III. Carbon fiber and graphite composite

[0288] 1. Graphite paper pretreatment and perforation

[0289] High-density graphite paper is flattened and fixed onto the vacuum worktable of a CNC punching machine, with no wrinkles or curling edges on the surface. The array punching mode is selected according to the application performance requirements.

[0290] The hole diameter is controlled at 0.5mm, the hole spacing is controlled at 10mm, the porosity range is 20%, the hole shape is circular, and the coaxiality deviation of the channel is ±0.05mm.

[0291] The punch is made of carbide, with a rotation speed controlled at 1000 r / min, an axial feed speed controlled at 10 mm / s, and a single punch depth error of ±0.02 mm.

[0292] After drilling, clean compressed air at 0.2 MPa is used to blow the graphite paper twice on both sides at a 45° angle to remove residual graphite debris from the holes. The surface debris residue should be ≤0.1 g / m². 2 The sampling test showed that the pore permeability was ≥99.5%.

[0293] 2. Resin spraying pretreatment

[0294] Carbon fiber prepreg and perforated graphite paper were coated with resin on their surfaces. The spraying environment temperature was controlled at 28℃, the relative humidity was controlled at 30%, and the cleanliness of the spraying area was ≥100,000.

[0295] The resin used is Shandong Shengquan dicyclopentadiene phenol epoxy resin, with the resin solid content controlled at 60%, and a coupling agent accounting for 1% of the resin mass is added to improve the interfacial bonding force.

[0296] The spraying process uses an air atomizing spray gun, with the spraying pressure controlled at 0.6 MPa, the distance between the spray gun and the substrate surface controlled at 15 cm, the spray gun moving speed controlled at 10 cm / s, and the spray overlap rate controlled at 30%.

[0297] The amount of resin sizing applied to one side of the graphite paper should be controlled at 30g / m². 2 The amount of resin applied to one side of the carbon fiber prepreg is controlled at 20g / m. 2 The uniformity of adhesive application on the same substrate is within ±5%.

[0298] After spraying, place the substrate in a stepped heating oven for pre-drying. First, place it at 50℃ for 10 minutes, then raise the temperature to 80℃ and hold for 3 minutes until the resin surface is semi-dry and not sticky. The overall volatile content of the substrate should be controlled at 10%.

[0299] 3. Layered material laying and high-pressure pressing

[0300] The materials are laid alternately according to the basic structure of "carbon fiber prepreg - graphite paper - carbon fiber prepreg", with a total of 9 layers. The alignment deviation of the materials is ±0.5mm. After the materials are laid, they are sent to a flatbed press for pressing.

[0301] The pressing temperature is controlled by gradient heating. The initial temperature is 60℃, the heating rate is controlled at 3℃ / min, the final pressing temperature is controlled at 180℃, and the pressing pressure is controlled at 10MPa.

[0302] A stepped pressurization process is adopted: first, the pressure is increased to 30% of the set pressure at a rate of 2MPa / min, and the temperature and pressure are maintained for 5 minutes to remove residual gas between layers; then, the pressure is increased to the set pressure at a rate of 2MPa / min, and the total pressing time is controlled at 90 minutes.

[0303] After pressing, the press's circulating water cooling system is turned on to cool the platen to below 40°C at a rate of 1°C / min. Then the mold is opened and the pressure is released to obtain the composite blank. The overall thickness deviation of the blank is 7%, and the interlayer bonding force is 15N / mm.

[0304] 4. Curing treatment

[0305] The pressed composite blank is sent into a programmed temperature curing oven for curing treatment, and the blank is prevented from being deformed by external force throughout the curing process.

[0306] The curing temperature range is 100℃-220℃, and a three-stage heating program is adopted: the first stage heats up to 100℃ at a rate of 2℃ / min and holds for 30min to allow the resin to flow fully; the second stage heats up to 160℃ at a rate of 2℃ / min and holds for 60min to complete the resin crosslinking reaction; the third stage heats up to 220℃ at a rate of 1℃ / min and holds for 60min to remove residual small molecule substances.

[0307] The entire curing process is protected by high-purity nitrogen gas at 0.05MPa, and the oxygen content in the furnace is ≤500ppm to avoid high-temperature oxidation of the resin.

[0308] After curing, the cured blank is cooled to room temperature in the oven and then removed. The cured blank is tested according to GB / T 2567 standard and the degree of resin curing is ≥90%, with no appearance defects such as delamination or bubbling.

[0309] 5. Carbonization treatment

[0310] The solidified blank is fed into a vacuum carbonization furnace for carbonization treatment. The blank is vertically clamped using graphite clamps, and the loading gap is controlled at 10mm to ensure uniform atmosphere flow.

[0311] The carbonization temperature range is 1000℃, and the heating rate is controlled in stages: the heating rate is 2℃ / min in the stage from room temperature to 600℃, the heating rate is 5℃ / min in the stage from 600℃ to the target temperature, and the temperature is held for 60min after reaching the target temperature.

[0312] High-purity nitrogen gas with a flow rate of 3L / min is introduced into the furnace as a protective atmosphere throughout the carbonization process, and the oxygen content in the furnace is ≤100ppm.

[0313] After carbonization, the material is cooled to room temperature in the furnace to obtain a carbonized billet. The carbonization yield is controlled at 60%, the open porosity is controlled at 20%, and there are no defects such as cracks or deformation.

[0314] 6. Densification treatment: CVI process for densification

[0315] Methane was selected as the precursor, argon was used as the carrier gas, the flow ratio of the precursor to the carrier gas was controlled at 1:2, and the total ventilation flow rate was controlled at 10L / min.

[0316] The furnace temperature is controlled at 1100℃, the furnace pressure is controlled at 10kPa, and the deposition time is controlled at 150h. The process parameters can be adjusted in stages according to the density growth.

[0317] Density was measured every 30 hours, and the density of the billet after densification reached 1.45 g / cm³. 3 This will stop the deposition process.

[0318] 7. Graphitization treatment

[0319] The densified billet is then fed into a high-temperature graphitization furnace for graphitization treatment.

[0320] The graphitization temperature was controlled at 1900℃, and the heating rate was controlled in stages: the heating rate was 5℃ / min in the stage from room temperature to 1500℃, and the heating rate was 3℃ / min in the stage from 1500℃ to the target temperature. After reaching the target temperature, the temperature was held for 120 minutes.

[0321] High-purity argon gas is introduced into the furnace for protection throughout the graphitization process, and the furnace pressure is a slight positive pressure of 200Pa to prevent air from seeping in and causing material oxidation.

[0322] After graphitization, the material is cooled to room temperature in the furnace to obtain a graphitized composite component. The degree of graphitization is controlled at 90% according to GB / T 3074.3 standard.

[0323] 8. Post-processing and finished product preparation

[0324] After graphitization, the composite components undergo 100% visual inspection to remove defective parts such as surface blistering, cracking, and delamination. Core properties such as density, tensile strength, thermal conductivity, and resistivity are then sampled and tested according to standards such as GB / T 3074.1, GB / T 8722, and GB / T 1551. The thickness is 1.75-1.85 mm, and the batch pass rate is ≥90%.

[0325] Components that meet performance requirements are die-cut into shape using a CNC die-cutting machine according to customer drawings. Carbide or diamond tools are used for die-cutting, the die-cutting pressure is controlled at 50MPa, the die-cutting size deviation is ±0.1mm, and the edge burr height is 0.05mm.

[0326] After die-cutting, surface impurities are blown away with 0.1MPa clean compressed air. After passing the random inspection, the product is sealed in a moisture-proof vacuum bag.

[0327] IV. Test Results

[0328] 1. Material flatness: ±0.05mm;

[0329] 2. Conductivity: 220-250 S / cm;

[0330] 3. Compressive strength: 210-230 MPa, tensile strength: 110-130 MPa;

[0331] 4. At 500mA / cm 2 At a current density of 48 cm², the reaction area is 48 cm². 2 Using vanadium-based electrolyte, it can be cycled more than 2,500 times without any swelling or foaming.

[0332] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a flow channel plate for a flow battery, characterized in that: Includes the following steps: S1. Preparation of carbon fiber substrate a. Resin solution preparation: Add diluent and coupling agent to the resin in sequence, stir at 45℃-55℃ and then cool down to 25℃-35℃, add curing agent and continue stirring to obtain resin solution. The viscosity of the solution is controlled at 150mPa·s-500mPa·s, and allowed to stand to remove bubbles. b. Substrate pretreatment: Dry the carbon fiber woven fabric or carbon fiber filament unidirectional fabric at 80℃-120℃; wherein, the areal density of the carbon fiber fabric is controlled at 50g / m². 2 -300g / m 2 The tensile strength of a single filament is ≥3500MPa, and the tensile modulus is ≥230GPa; c. Impregnation and quantity control: The pretreated substrate is passed through the impregnation tank at a uniform speed of 0.5m / min-2m / min. The temperature of the adhesive solution in the impregnation tank is maintained at 30℃-40℃, and the impregnation time of the substrate in the adhesive solution is controlled at 10s-30s. After impregnation, the substrate is extruded by rollers to control the quantity, resulting in a pre-impregnated blank with a resin content controlled at 30%-45%. d. Drying and winding; S2. Preparation of graphite paper a. Preparation of expandable graphite by intercalation reaction: Flake graphite was mixed with a mixture of concentrated sulfuric acid and concentrated nitric acid at 10℃-30℃ with stirring. Potassium permanganate was added in batches, with the addition time controlled at 5min-15min, and the temperature was maintained at 20℃-40℃. The reaction was continued with stirring for 30min-90min. After the reaction was completed, hydrogen peroxide was added to terminate the reaction. After stirring, the mixture was filtered, washed, and dried to obtain expandable graphite. b. Preparation of worm-shaped graphite by high-temperature expansion: Expandable graphite is continuously fed into a high-temperature expansion furnace, and the temperature inside the furnace is controlled at 900℃-1200℃. The graphite stays in the furnace for 10s-60s to obtain fluffy worm-shaped graphite. c. Pre-compression molding: The worm graphite is loosened and dispersed, then evenly spread to a thickness of 5cm-20cm. Preliminary compaction is then performed at a pre-compression pressure of 0.1MPa-0.5MPa. After pre-compression, a foamed graphite preform with a thickness of 1cm-5cm is obtained, with a surface density controlled at 100g / m³. 2 -2000g / m 2 ; d. High-density graphite paper preparation by multi-stage rolling: Foamed graphite preforms are subjected to gradient rolling, with a total of 3-5 rolling processes, ultimately resulting in high-density graphite paper with a density controlled at 1.3 g / cm³. 3 -1.8g / cm 3 ; e. Post-processing and winding: The rolled graphite paper is impregnated in a sodium carboxymethyl cellulose aqueous solution with a mass concentration of 0.2%-1% for 5-20 seconds, dried, and then wound up. S3. Carbon fiber graphite composite a. Graphite paper pretreatment and perforation: The perforation diameter is controlled between 0.1mm and 5mm, the perforation spacing is controlled between 0.5mm and 20mm, and the porosity ranges from 5% to 30%; b. Resin spraying pretreatment: The carbon fiber prepreg and the perforated graphite paper are subjected to surface resin spraying treatment, with the resin coating amount on one side of the graphite paper controlled at 10g / m². 2 -80g / m 2 The amount of resin applied to one side of the carbon fiber prepreg is controlled at 20g / m. 2 -150g / m 2 ; c. Laying and high-pressure pressing: Lay out materials alternately according to the basic structure of carbon fiber prepreg - graphite paper - carbon fiber prepreg, with a total number of layers ranging from 2 to 20. After laying out the materials, press them together. d. Curing treatment; e. Carbonization treatment; f. Densification treatment: Select chemical vapor infiltration or precursor impregnation pyrolysis process to densify the carbonized billet according to performance requirements; g. Graphitization treatment: After the densified billet is sent into a high-temperature graphitization furnace for graphitization treatment, the finished flow battery flow channel plate is obtained.

2. The method for preparing a flow battery channel plate according to claim 1, characterized in that: In step S1a, the resin is selected from one or more of epoxy resin, phenolic resin, furan resin, and asphalt resin; the curing agent is selected from any one of amines and imidazoles, and the curing agent accounts for 0.5%-3% of the total mass of the resin; the diluent is selected from any one of acetone and anhydrous ethanol, and the diluent accounts for 1%-4% of the total mass of the resin; the coupling agent is selected from any one of silane coupling agents KH550 and KH560, and the coupling agent accounts for 0.2%-1.5% of the total mass of the resin; the total mass of the curing agent, diluent, and coupling agent accounts for 2%-8% of the total mass of the resin.

3. The method for preparing a flow battery channel plate according to claim 1, characterized in that: In step S1d, the prepreg fabric after impregnation is fed into a stepped drying oven, which is divided into three temperature control sections: the first section temperature is 60℃-80℃, and the dwell time is 2min-5min; the second section temperature is 90℃-110℃, and the dwell time is 3min-8min; the third section temperature is 50℃-70℃, and the dwell time is 1min-3min. After drying, the prepreg fabric is wound up after the tension roller is adjusted to 5N / m-20N / m. The winding tightness is controlled so that the deviation of the roll diameter per meter is ≤2mm.

4. The method for preparing a flow battery channel plate according to claim 1, characterized in that: In step S2a, the mass ratio of the raw materials used is as follows: 80%-92% natural flake graphite; 2%-10% concentrated sulfuric acid, 1%-5% concentrated nitric acid, 0.5%-3% potassium permanganate, and 0.3%-2% hydrogen peroxide.

5. The method for preparing a flow battery channel plate according to claim 1, characterized in that: In step S2d, the calendering process is as follows: First calendering: roll gap 1mm-8mm, rolling pressure 0.5MPa-2MPa, calendered thickness controlled at 1mm-5mm; Second calendering: roll gap 0.5mm-3mm, rolling pressure 2MPa-5MPa, calendered thickness controlled at 0.3mm-2mm; Third calendering: roll gap 0.1mm-1mm, rolling pressure 5MPa-15MPa, calendered thickness controlled at 0.1mm-0.8mm; If higher density is required, 1-2 additional calendering passes are added, the roll gap is adjusted to 0.05mm-0.5mm, and the rolling pressure is 10MPa-25MPa.

6. The method for preparing a flow battery channel plate according to claim 1, characterized in that: In step S3b, the resin is any one of phenolic resin, epoxy resin or furan resin, and the resin solid content is controlled at 30%-60%; the spraying pressure is controlled at 0.1MPa-0.8MPa, the distance between the spray gun and the substrate surface is controlled at 15cm-50cm, the spray gun moving speed is controlled at 5cm / s-30cm / s, and the spraying overlap rate is controlled at 30%-50%.

7. The method for preparing a flow battery channel plate according to claim 1, characterized in that: In step S3c, the pressing settings are as follows: The pressing temperature is controlled by gradient heating: the initial temperature is 40℃-60℃, the heating rate is controlled at 1℃ / min-3℃ / min, the final pressing temperature is controlled at 80℃-180℃, and the pressing pressure is controlled at 5MPa-50MPa. A stepped pressurization process is adopted: first, pressurize at a rate of 1MPa / min-5MPa / min to 30% of the set pressure, and maintain the temperature and pressure for 5min-20min; then continue to pressurize at a rate of 0.5MPa / min-2MPa / min to the set pressure, with the total pressing time controlled between 30min-120min.

8. The method for preparing a flow battery channel plate according to claim 1, characterized in that: In step S3d, the curing temperature range is 100℃-250℃, using a three-stage heating program: the first stage heats up to 100℃-120℃ at a rate of 1℃ / min-3℃ / min, and holds for 30min-90min; the second stage heats up to 150℃-180℃ at a rate of 0.5℃ / min-2℃ / min, and holds for 60min-180min; the third stage heats up to 200℃-250℃ at a rate of 0.5℃ / min-2℃ / min, and holds for 30min-120min; high-purity nitrogen or argon gas at 0.02MPa-0.1MPa is introduced throughout the curing process for protection, and the oxygen content in the furnace is ≤500ppm; In step S3e, the carbonization temperature range is 800℃-1600℃, and the heating rate is controlled in stages: the heating rate is 0.5℃ / min-2℃ / min in the stage from room temperature to 600℃, and the heating rate is 2℃ / min-5℃ / min in the stage from 600℃ to the target temperature. After reaching the target temperature, the temperature is held for 60min-240min. The vacuum degree is controlled at 10Pa-1000Pa throughout the carbonization process, or high-purity nitrogen or argon gas with a flow rate of 0.5L / min-5L / min is introduced as a protective atmosphere, and the oxygen content in the furnace is ≤100ppm.

9. The method for preparing a flow battery channel plate according to claim 1, characterized in that: In step S3f, the CVI process densification parameters are as follows: the precursor is any one of methane, propylene, or natural gas; the carrier gas is hydrogen, nitrogen, or argon; the precursor to carrier gas flow rate ratio is controlled at 1:2-1:10; the total gas flow rate is controlled at 5L / min-50L / min; the furnace temperature is controlled at 900℃-1200℃; the furnace pressure is controlled at 1kPa-20kPa; the deposition time is controlled at 50h-200h; and the density of the billet after densification reaches 1.5g / cm³. 3 -2.2g / cm 3 ; The density-enhancing parameters for the PIP process are as follows: The precursor is any one of phenolic resin, furan resin, or asphalt, with a solid content controlled between 30% and 70%. Before impregnation, the carbonized preform is placed in an impregnation tank and evacuated to 10 Pa to 1000 Pa, maintained for 10 to 60 minutes, then the precursor is injected, followed by a pressure of 1 MPa to 10 MPa. The impregnation time for each cycle is controlled between 1 hour and 10 hours. After impregnation, the preform is removed and subjected to curing and carbonization treatment, completing one impregnation-curing-carbonization cycle. This cycle is repeated until the preform density reaches 1.5 g / cm³. 3 -2.2g / cm 3 ; In step S3g, the graphitization temperature is controlled between 1800℃ and 3000℃, and the heating rate is controlled in stages: the heating rate is 5℃ / min to 10℃ / min in the stage from room temperature to 1500℃, and the heating rate is 1℃ / min to 5℃ / min in the stage from 1500℃ to the target temperature. After reaching the target temperature, the temperature is held for 30min to 120min. The vacuum degree is controlled between 1Pa and 100Pa throughout the graphitization process, or high-purity argon gas is introduced for protection, and the pressure inside the furnace is 100Pa to 500Pa slightly positive pressure.

10. A flow battery channel plate prepared by any one of the preparation methods described in claims 1-9.

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