Preparation process of a carbon felt rich in functional groups, carbon felt electrode and flow battery

Abstract

The present invention discloses a preparation process of a carbon felt rich in functional groups, a carbon felt electrode and a flow battery. Among them, the preparation process includes: a step of subjecting a pre-cut carbon felt to oxidation treatment with ozone to functionalize the surface of the carbon felt to obtain an intermediate carbon felt material; a step of preparing an aqueous solution of carbon powder containing a binder; and a step of immersing the intermediate carbon felt material with the aqueous solution of carbon powder and drying it to coat the surface load of the intermediate carbon felt material to obtain a finished carbon felt. The present invention uses ozone catalytic oxidation to perform surface treatment on the carbon felt, which can increase the oxygen-containing functional groups such as hydroxyl groups and carboxyl groups on the surface of the carbon felt, improve the hydrophilicity of the carbon felt, and ensure the stability of the carbon felt structure; at the same time, the surface-loaded carbon can protect the functional groups of the carbon felt, delay defunctionalization, and increase the specific surface area of the carbon felt, effectively reducing the current density; at the same time, the surface-loaded carbon also increases the surface area of the carbon felt, improving the apparent current density and power density of the stack operation.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and particularly to a preparation process of a functional group-rich carbon felt, a carbon felt electrode and a flow battery. Background Art

[0002] Flow batteries are favored because of their simple structure, no safety hazards, no fire risks, and suitability for long-term energy storage. Generally, they can be charged and discharged up to 20,000 times. Although flow batteries have low energy density, large volume and high cost, they have an absolute advantage in terms of safety. Therefore, they play an irreplaceable role in some special application fields.

[0003] Currently, the common problem of flow batteries is low power density. Increasing the current density is the key factor to improve the power density of flow batteries. Therefore, how to increase the electrode current density is extremely crucial. Flow battery electrodes are generally carbon-based materials, such as carbon felt and graphite felt. Due to the poor hydrophilicity of carbon-based materials, it seriously affects the Coulomb efficiency at high current densities. Currently, heat treatment is usually used to improve the hydrophilicity of carbon-based materials. However, during the cycling process, functional groups are easily removed, resulting in performance degradation. Moreover, the heat treatment method destroys the structure of the carbon felt to a certain extent and reduces the stability of the carbon felt electrode. Therefore, there is an urgent need to propose a new treatment method to reduce the loss of functional groups in carbon-based materials and improve their stability. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a preparation process of a functional group-rich carbon felt, a carbon felt electrode and a flow battery.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] According to the first aspect of the embodiments of the present disclosure, a preparation process of a functional group-rich carbon felt is provided, including:

[0007] A step of oxidizing a pre-cut carbon felt with ozone to functionalize the surface of the carbon felt to obtain a carbon felt intermediate;

[0008] A step of preparing an aqueous solution of carbon powder containing a binder;

[0009] A step of immersing the carbon felt intermediate in the aqueous solution of carbon powder and drying it to coat the surface load of the carbon felt intermediate to obtain a carbon felt finished product.

[0010] In some exemplary embodiments, the step of oxidizing a pre-cut carbon felt with ozone to functionalize the surface of the carbon felt to obtain a carbon felt intermediate specifically includes:

[0011] Configuring an alkaline aqueous solution with a pH of 8-12 in a reactor;

[0012] Ozone is introduced into the reactor by bottom aeration;

[0013] The pre-cut carbon felt is placed in the alkaline aqueous solution for continuous oxidation reaction for 8 - 24 h to functionalize the surface of the carbon felt to obtain the carbon felt intermediate material.

[0014] In some exemplary embodiments, the method for preparing the alkaline aqueous solution is as follows:

[0015] An appropriate amount of aqueous solution is added to the reactor, the pH is adjusted to 8 - 12 with sodium hydroxide, and then an oxidant is added to obtain the alkaline aqueous solution.

[0016] In some exemplary embodiments, when introducing ozone, the inlet gas flow rate is adjusted to 1.8 - 2.5 L / min, and the ozone concentration is 80 - 120 mg / L.

[0017] In some exemplary embodiments, the step of preparing the aqueous solution of carbon powder containing a binder specifically includes:

[0018] Polyethylene glycol and carbon material are mixed evenly at a temperature of 100 - 200 °C according to a mass ratio of 1:10 - 1:100. After cooling, pyrolysis is carried out at 700 - 1050 °C in an atmosphere with a volume ratio of ammonia to hydrogen of 1:1 to obtain a carbon material rich in groups;

[0019] An aqueous solution is prepared with the carbon material rich in groups as the raw material, and a binder is added to obtain an aqueous solution of carbon powder, wherein the weight ratio of the binder in the aqueous solution of carbon powder is 20% - 30% of the carbon material.

[0020] In some exemplary embodiments, the carbon material is EC600 or BP2000; the binder is Nafion, PVDF or PTFE.

[0021] In some exemplary embodiments, the step of using the aqueous solution of carbon powder to immerse the carbon felt intermediate material and drying it to wrap the surface load of the carbon felt intermediate material specifically includes:

[0022] The carbon felt intermediate material is placed in a flat plate with a frame, and the aqueous solution of carbon powder is poured into the frame to immerse the upper surface of the carbon felt intermediate material to form a surface load;

[0023] After there is no obvious liquid flow on the surface of the carbon felt intermediate material, it is placed in an oven for drying treatment at a constant temperature to wrap the surface load;

[0024] The above steps are repeated until the weight of the surface load accounts for 3% - 10% of the weight of the carbon felt to obtain the carbon felt finished product.

[0025] In some exemplary embodiments, during the drying process, the drying temperature is controlled to be 160-200° C., each drying time is 3.5-4 hours, and the last drying time is 7-8 hours.

[0026] According to a second aspect of an embodiment of the present disclosure, a carbon felt electrode is provided, which is made of a carbon felt product obtained by the preparation process described in the first aspect as a raw material.

[0027] According to a third aspect of an embodiment of the present disclosure, a liquid flow battery is provided, comprising a first bipolar plate, a first carbon felt electrode, a proton membrane, a second carbon felt electrode and a second bipolar plate arranged in sequence, wherein the first carbon felt electrode and the second carbon felt electrode both adopt the carbon felt electrode described in the second aspect.

[0028] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0029] The embodiment of the present invention provides a preparation process of carbon felt rich in functional groups, a carbon felt electrode and a liquid flow battery, and uses ozone catalytic oxidation to treat the surface of the carbon felt, which can increase the oxygen-containing functional groups such as hydroxyl and carboxyl on the surface of the carbon felt and improve the hydrophilicity of the carbon felt. Compared with the heat treatment method used in the prior art, which will destroy the stability of the carbon felt to a certain extent, resulting in the easy loss of functional groups during operation and the loosening and easy falling of carbon, the ozone catalytic oxidation method is more gentle and will not damage the carbon felt structure, thereby ensuring the stability of the carbon felt structure; and the hydroxyl free radicals are generated by ozone catalysis, and the oxidation potential can reach 2.87V, the direct oxidation potential of ozone is 2.07V, and the oxidation potential of carbon felt is greater than 0.2V, so ozone and hydroxyl catalysis ozone to generate hydroxyl free radicals can effectively functionalize the surface of the carbon felt;

[0030] The heat treatment method used in the prior art can easily make the carbon felt surface loose, and the functional groups are on the surface layer. These two factors can easily lead to the loss of functional groups due to disturbance, scouring, temperature changes and other factors during the subsequent test operation; while the chemical oxidation method using ozone avoids the influence on the carbon felt structure. At the same time, in order to reduce the influence of external forces on the surface functional groups, a large area of carbon material is loaded on the functionalized carbon felt, which can protect the carbon felt functional groups, buffer the surface external forces, and delay defunctionalization, and on the other hand, increase the specific surface area of the carbon felt, effectively reducing the current density;

[0031] By adding adhesives, since the adhesives have hydrophilic groups, they have strong hydrophilicity. Therefore, the surface carbon-coated functionalized carbon felt not only improves the stability of the functional groups on the surface of the carbon felt, but also improves the hydrophilicity of the surface-loaded carbon. At the same time, the surface-loaded carbon also increases the surface area of the carbon felt, which can improve the apparent current density and power density of the stack. DETAILED DESCRIPTION

[0032] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] The first aspect of the embodiments of the present invention provides a preparation process of a carbon felt rich in functional groups, including:

[0034] S100. A step of oxidizing the pre-cut carbon felt with ozone to functionalize the surface of the carbon felt to obtain an intermediate carbon felt material.

[0035] Among them, S100 specifically includes:

[0036] S101. Configure an alkaline aqueous solution with a pH of 8-12 in the reactor. The configuration method of the alkaline aqueous solution is: add an appropriate amount of aqueous solution to the reactor, adjust the pH to 8-12 with sodium hydroxide, and then add an oxidant to obtain the alkaline aqueous solution. The reactor can be, for example, an organic glass columnar reactor, and the oxidant can be, for example, an aqueous hydrogen peroxide solution;

[0037] S102. Pass ozone into the reactor by bottom aeration. Specifically, there is an aeration port at the bottom of the reactor, and the gas enters from the aeration port. The upper end of the reactor is connected to a water-gas separator, and the ozone is treated by the water-gas separator and the waste gas is treated by a tail gas destruction device. When passing ozone, the inlet gas flow rate is adjusted to 1.8-2.5 L / min, and the ozone concentration is 80-120 mg / L;

[0038] S103. Place the pre-cut carbon felt in the alkaline aqueous solution and carry out an oxidation reaction for 8-24 h to functionalize the surface of the carbon felt to obtain an intermediate carbon felt material. The size of the pre-cut carbon felt can be set according to actual needs.

[0039] S200. A step of preparing an aqueous solution of carbon powder containing a binder.

[0040] Among them, S200 specifically includes:

[0041] S201. Mix polyethylene glycol and carbon materials in a mass ratio of 1:10-1:100 at a temperature of 100-200 °C and mix evenly. After cooling, pyrolyze in an atmosphere of 700-1050 °C with a volume ratio of ammonia to hydrogen of 1:1 to obtain a carbon material rich in groups. The carbon materials can be of the following two types: EC600 or BP2000, both of which are excellent conductive carbon blacks;

[0042] S202. Prepare an aqueous solution using the carbon material rich in groups as the raw material, and add a binder to obtain an aqueous carbon powder solution. The weight ratio of the binder in the aqueous carbon powder solution is 20%-30% of the carbon material. The binder used is Nafion (Nafion Macromolecule, perfluorosulfonic acid resin), PVDF (Polyvinylidene Difluoride), or PTFE (Polytetrafluoroethylene).

[0043] S300. A step of using the aqueous carbon powder solution to immerse the carbon felt intermediate material and drying it to wrap the surface load of the carbon felt intermediate material to obtain a carbon felt finished product.

[0044] Among them, S300 specifically includes:

[0045] S301. Place the carbon felt intermediate material in a flat plate with a frame, pour the aqueous carbon powder solution into the frame to immerse the upper surface of the carbon felt intermediate material to form a surface load. Among them, after the oxidation of the carbon felt intermediate material is completed, it is first washed with water until it is close to neutral. The frame is located around the flat plate and its height is greater than the thickness of the carbon felt, so as to be able to hold a certain amount of aqueous carbon powder solution;

[0046] S302. After there is no obvious liquid flow on the surface of the carbon felt intermediate material, place it in an oven for drying treatment at a constant temperature to wrap the surface load;

[0047] S303. Repeat the above steps until the weight of the surface load accounts for 3%-10% of the weight of the carbon felt to obtain a carbon felt finished product. During the drying treatment, control the drying temperature at 160-200°C, the drying duration each time is 3.5-4h, and the last drying duration is 7-8h. After multiple drying treatments, the process of wrapping the surface load of the carbon felt intermediate material is completed.

[0048] In the second aspect of the embodiments of the present invention, a carbon felt electrode is provided, which is made of the carbon felt finished product prepared by the preparation process in the first aspect as the raw material. It can directly be the carbon felt finished product, or it can be obtained by trimming the carbon felt finished product to a certain extent.

[0049] In the third aspect of the embodiments of the present invention, a flow battery is provided, which includes a first bipolar plate, a first carbon felt electrode, a proton membrane, a second carbon felt electrode, and a second bipolar plate arranged in sequence. Among them, both the first carbon felt electrode and the second carbon felt electrode adopt the carbon felt electrode described in the second aspect, and both the first bipolar plate and the second bipolar plate can adopt graphite bipolar plates; it can be understood that as a complete flow battery stack, it can also include components such as a frame and a current collector plate to form a complete sealed structure. The overall structure of the flow battery is the same as that in the prior art and will not be elaborated here.

[0050] The present invention uses ozone catalytic oxidation to treat the surface of carbon felt, which can increase the oxygen-containing functional groups such as hydroxyl and carboxyl groups on the surface of the carbon felt, improve the hydrophilicity of the carbon felt. Compared with the heat treatment method in the prior art, it will to a certain extent damage the stability of the carbon felt, resulting in easy loss of functional groups during operation, and will make the carbon loose and easy to fall off. The method of ozone catalytic oxidation is milder and will not damage the structure of the carbon felt, ensuring the stability of the carbon felt structure; and hydroxyl radicals are generated by ozone catalysis, the oxidation potential can reach 2.87V, the direct oxidation potential of ozone is 2.07V, and the oxidation potential of the carbon felt is greater than 0.2V. Therefore, ozone and hydroxyl-catalyzed ozone can efficiently functionalize the surface of the carbon felt;

[0051] In the prior art, the heat treatment method is likely to make the surface of the carbon felt loose, and at the same time, the functional groups are in the surface layer. These two factors are likely to cause the loss of functional groups due to factors such as disturbance, scouring, and temperature change during subsequent tests; while the method of chemical oxidation with ozone avoids the influence on the structure of the carbon felt. At the same time, in order to reduce the influence of external force on the surface functional groups, a large-area carbon material is loaded on the functionalized carbon felt. On the one hand, it protects the functional groups of the carbon felt, buffers the surface external force, and delays defunctionalization. On the other hand, it increases the specific surface area of the carbon felt and effectively reduces the current density;

[0052] By adding a binder, since the binder has hydrophilic groups, it has strong hydrophilicity. Therefore, the surface carbon-coated functionalized carbon felt not only improves the stability of the functional groups on the surface of the carbon felt, but also improves the hydrophilicity problem of the surface-loaded carbon. At the same time, the surface-loaded carbon also increases the surface area of the carbon felt, which can improve the apparent current density and power density of the stack operation.

[0053] The following specific embodiments are used to illustrate the specific implementation manners of the present invention. It should be understood that the following embodiments are only used to illustrate and explain the present invention, and do not limit the scope of the present invention in any way for those skilled in the art to more specifically understand the present invention.

[0054] Example 1

[0055] A preparation process of a functional group-rich carbon felt, including:

[0056] S100. A step of oxidizing the pre-cut carbon felt with ozone to functionalize the surface of the carbon felt to obtain an intermediate carbon felt material.

[0057] Among them, S100 specifically includes:

[0058] S101. Add 50L of water into an organic glass column reactor, adjust the pH to 10.5 with sodium hydroxide, and then add a 3% hydrogen peroxide aqueous solution with a content of 37% to obtain an alkaline aqueous solution;

[0059] S102. Turn on the ozone generator, adjust the intake flow rate to 2 L / min, and the ozone concentration to 100 mg / L. Introduce ozone into the reactor through bottom aeration.

[0060] S103. Place the pre-cut carbon felt with a size of 40 cm * 50 cm in the alkaline aqueous solution and carry out continuous oxidation reaction for 12 h to functionalize the surface of the carbon felt and obtain the carbon felt intermediate material.

[0061] S200. Steps for preparing an aqueous solution of carbon powder containing a binder.

[0062] Among them, S200 specifically includes:

[0063] S201. Mix 1 g of polyethylene glycol and 10 g of BP2000 evenly at a temperature of 100 °C. The molecular weight of polyethylene glycol is 1500. After cooling, carry out pyrolysis in an atmosphere with a temperature of 850 °C and a volume ratio of ammonia to hydrogen of 1:1 to obtain BP2000 rich in groups.

[0064] S202. Prepare a 2% aqueous solution of BP2000 using this BP2000 rich in groups as the raw material, and add a 5% Nafion solution to obtain an aqueous solution of carbon powder, where the weight ratio of Nafion in the aqueous solution of carbon powder is 20% of the carbon material.

[0065] S300. Steps for using the aqueous solution of carbon powder to immerse the carbon felt intermediate material and drying it to wrap the surface load of the carbon felt intermediate material to obtain the carbon felt finished product.

[0066] Among them, S300 specifically includes:

[0067] S301. Wash the carbon felt intermediate material until it is nearly neutral and place it in a flat plate with a frame. The height of the frame is greater than the thickness of the carbon felt, and the height of the frame is about 8 mm. Pour the aqueous solution of carbon powder into the frame to immerse the upper surface of the carbon felt intermediate material to form a surface load, and the aqueous solution of carbon powder just needs to immerse the surface of the carbon felt intermediate material.

[0068] S302. After there is no obvious liquid flow on the surface of the carbon felt intermediate material, place it in an oven and carry out drying treatment at a constant temperature to wrap the surface load. The oven temperature is set to 180 °C, and the constant temperature duration is set to 4 h.

[0069] S303. Repeat the above steps until the weight of the surface load accounts for 6% of the weight of the carbon felt to obtain the carbon felt finished product. Among them, the constant temperature duration of the last drying is set to 8 h, and after multiple drying treatments, the process of wrapping the surface load of the carbon felt intermediate material is completed.

[0070] Example 2

[0071] A preparation process of a carbon felt rich in functional groups, including:

[0072] S100. The step of oxidizing the pre-cut carbon felt with ozone to functionalize the surface of the carbon felt to obtain an intermediate carbon felt material.

[0073] Among them, S100 specifically includes:

[0074] S101. Add 50 L of water into an acrylic glass columnar reactor, adjust the pH to 8 with sodium hydroxide, and then add a 3% aqueous hydrogen peroxide solution with a content of 37% to obtain an alkaline aqueous solution;

[0075] S102. Turn on the ozone generator, adjust the inlet gas flow rate to 1.8 L / min, the ozone concentration to 80 mg / L, and introduce ozone into the reactor by bottom aeration;

[0076] S103. Place the pre-cut carbon felt with dimensions of 40 cm * 50 cm in the alkaline aqueous solution and carry out an oxidation reaction for 8 h to functionalize the surface of the carbon felt to obtain an intermediate carbon felt material.

[0077] S200. The step of preparing an aqueous carbon powder solution containing an adhesive.

[0078] Among them, S200 specifically includes:

[0079] S201. Mix 1 g of polyethylene glycol and 10 g of BP2000 evenly at a temperature of 200 °C. The molecular weight of polyethylene glycol is 1500. After cooling, pyrolyze it in an atmosphere of 700 °C with a volume ratio of ammonia to hydrogen of 1:1 to obtain BP2000 rich in groups;

[0080] S202. Use the BP2000 rich in groups as a raw material to prepare a 2% aqueous BP2000 solution by weight, and add a 5% Nafion solution to obtain an aqueous carbon powder solution, where the weight ratio of Nafion in the aqueous carbon powder solution is 20% of the carbon material.

[0081] S300. The step of immersing the intermediate carbon felt material with the aqueous carbon powder solution and drying it to wrap the surface load of the intermediate carbon felt material to obtain a finished carbon felt.

[0082] Among them, S300 specifically includes:

[0083] S301. Wash the intermediate carbon felt to near neutrality and place it in a flat plate with a frame. The height of the frame is greater than the thickness of the carbon felt. The height of the frame is about 8 mm. Pour the aqueous carbon powder solution into the frame to immerse the upper surface of the intermediate carbon felt to form a surface load, and the aqueous carbon powder solution just needs to immerse the surface of the intermediate carbon felt;

[0084] S302. After there is no obvious liquid flow on the surface of the carbon felt intermediate material, place it in an oven and dry it at a constant temperature to wrap the surface load. The oven temperature is set at 160 °C, and the constant temperature duration is set at 3.5 h;

[0085] S303. Repeat the above steps until the weight of the surface load accounts for 3% of the weight of the carbon felt to obtain the carbon felt finished product. Among them, the constant temperature duration of the last drying is set at 7 h. After multiple drying treatments, the process of wrapping the surface load of the carbon felt intermediate material is completed.

[0086] Example Three

[0087] A preparation process of a carbon felt rich in functional groups, including:

[0088] S100. A step of oxidizing a pre-cut carbon felt with ozone to functionalize the surface of the carbon felt to obtain a carbon felt intermediate material.

[0089] Among them, S100 specifically includes:

[0090] S101. Add 50 L of water into an organic glass columnar reactor, adjust the pH to 12 with sodium hydroxide, and then add a 3% hydrogen peroxide aqueous solution with a content of 37% to obtain an alkaline aqueous solution;

[0091] S102. Turn on the ozone generator, adjust the inlet gas flow rate to 2.5 L / min, and the ozone concentration to 120 mg / L, and introduce ozone into the reactor by bottom aeration;

[0092] S103. Place the pre-cut carbon felt with dimensions of 40 cm * 50 cm in the alkaline aqueous solution and carry out an oxidation reaction for 24 h to functionalize the surface of the carbon felt to obtain a carbon felt intermediate material.

[0093] S200. A step of preparing an aqueous solution of carbon powder containing a binder.

[0094] Among them, S200 specifically includes:

[0095] S201. Mix 1 g of polyethylene glycol and 100 g of BP2000 evenly at a temperature of 150 °C. The molecular weight of polyethylene glycol is 1500. After cooling, pyrolyze it under an atmosphere of 1050 °C, with a volume ratio of ammonia to hydrogen of 1:1, to obtain BP2000 rich in groups;

[0096] S202. Use this BP2000 rich in groups as a raw material to prepare a 2% aqueous solution of BP2000 by weight, and add a 5% Nafion solution to obtain an aqueous solution of carbon powder, where the weight ratio of Nafion in the aqueous solution of carbon powder is 30% of the carbon material.

[0097] Step S300: Submerge the carbon felt intermediate material with the aqueous carbon powder solution and then dry it to coat the surface loading of the carbon felt intermediate material, thereby obtaining a finished carbon felt.

[0098] Among them, S300 specifically includes:

[0099] Step S301: Wash the carbon felt intermediate material with water until it is nearly neutral, then place it in a flat plate with a frame. The height of the frame is greater than the thickness of the carbon felt, and the height of the frame is about 8 mm. Pour the aqueous carbon powder solution into the frame to submerge the upper surface of the carbon felt intermediate material to form a surface loading. The aqueous carbon powder solution just needs to submerge the surface of the carbon felt intermediate material.

[0100] Step S302: After there is no obvious liquid flow on the surface of the carbon felt intermediate material, place it in an oven for drying treatment at a constant temperature to coat the surface loading. The oven temperature is set at 200 °C, and the constant temperature duration is set at 4 h.

[0101] Step S303: Repeat the above steps until the weight of the surface loading accounts for 10% of the weight of the carbon felt, thereby obtaining a finished carbon felt. Among them, the constant temperature duration of the last drying is set at 8 h. After multiple drying treatments, the process of coating the surface loading of the carbon felt intermediate material is completed.

[0102] Example 4

[0103] A preparation process of a carbon felt rich in functional groups includes:

[0104] Step S100: Oxidize the pre-cut carbon felt with ozone to functionalize the surface of the carbon felt, thereby obtaining a carbon felt intermediate material.

[0105] Among them, S100 specifically includes:

[0106] Step S101: Add 50 L of water into an acrylic column reactor, adjust the pH to 10.5 with sodium hydroxide, and then add a 3% aqueous hydrogen peroxide solution with a content of 37% to obtain an alkaline aqueous solution.

[0107] Step S102: Turn on the ozone generator, adjust the inlet gas flow rate to 1.8 L / min, and the ozone concentration to 120 mg / L, and introduce ozone into the reactor by bottom aeration.

[0108] Step S103: Place the pre-cut carbon felt with dimensions of 40 cm * 50 cm in the alkaline aqueous solution and carry out an oxidation reaction for 12 h to functionalize the surface of the carbon felt, thereby obtaining a carbon felt intermediate material.

[0109] Step S200: Prepare an aqueous carbon powder solution containing a binder.

[0110] Among them, S200 specifically includes:

[0111] S201. Mix 1 g of polyethylene glycol with 50 g of BP2000 evenly at a temperature of 120°C. The molecular weight of polyethylene glycol is 1500. After cooling, pyrolyze it in an atmosphere of 900°C with a volume ratio of ammonia to hydrogen of 1:1 to obtain BP2000 rich in groups;

[0112] S202. Prepare an aqueous solution of BP2000 with a weight ratio of 2% using the BP2000 rich in groups as the raw material, and add 5% of Nafion solution to obtain an aqueous solution of carbon powder, where the weight ratio of Nafion in the aqueous solution of carbon powder is 25% of the carbon material.

[0113] S300. A step of immersing the carbon felt intermediate material with the aqueous solution of carbon powder and drying it to wrap the surface load of the carbon felt intermediate material to obtain a formed carbon felt.

[0114] Among them, S300 specifically includes:

[0115] S301. Wash the carbon felt intermediate material with water until it is close to neutral, then place it in a flat plate with a frame. The height of the frame is greater than the thickness of the carbon felt, and the height of the frame is about 8 mm. Pour the aqueous solution of carbon powder into the frame to immerse the upper surface of the carbon felt intermediate material to form a surface load, and the aqueous solution of carbon powder just needs to immerse the surface of the carbon felt intermediate material;

[0116] S302. After there is no obvious liquid flow on the surface of the carbon felt intermediate material, place it in an oven for drying treatment at a constant temperature to wrap the surface load. The oven temperature is set at 195°C, and the constant temperature duration is set at 4 h;

[0117] S303. Repeat the above steps until the weight of the surface load accounts for 8% of the weight of the carbon felt to obtain a formed carbon felt. Among them, the constant temperature duration of the last drying is set at 8 h, and after multiple drying treatments, the process of wrapping the surface load of the carbon felt intermediate material is completed.

[0118] Example Five

[0119] A preparation process of a carbon felt rich in functional groups, including:

[0120] S100. A step of oxidizing the pre-cut carbon felt with ozone to functionalize the surface of the carbon felt to obtain a carbon felt intermediate material.

[0121] Among them, S100 specifically includes:

[0122] S101. Add 50 L of water to an organic glass columnar reactor, adjust the pH to 11 with sodium hydroxide, and then add 3% of an aqueous hydrogen peroxide solution with a content of 37% to obtain an alkaline aqueous solution;

[0123] S102. Turn on the ozone generator, adjust the inlet gas flow rate to 2.2 L / min, and the ozone concentration to 100 mg / L. Then introduce ozone into the reactor by bottom aeration.

[0124] S103. Place the pre-cut carbon felt with a size of 40 cm * 50 cm in the alkaline aqueous solution and carry out continuous oxidation reaction for 12 h to functionalize the surface of the carbon felt and obtain the carbon felt intermediate material.

[0125] S200. Steps for preparing an aqueous solution of carbon powder containing a binder.

[0126] Among them, S200 specifically includes:

[0127] S201. Mix 1 g of polyethylene glycol with 30 g of BP2000 evenly at a temperature of 160 °C. The molecular weight of polyethylene glycol is 1500. After cooling, carry out pyrolysis in an atmosphere of 1000 °C with a volume ratio of ammonia to hydrogen of 1:1 to obtain BP2000 rich in functional groups.

[0128] S202. Use the BP2000 rich in functional groups as raw material to prepare a 2% aqueous solution of BP2000 by weight, and add 5% Nafion solution to obtain an aqueous solution of carbon powder, where the weight ratio of Nafion in the aqueous solution of carbon powder is 28% of the carbon material.

[0129] S300. Steps for using the aqueous solution of carbon powder to immerse the carbon felt intermediate material and drying it to wrap the surface load of the carbon felt intermediate material to obtain the carbon felt finished material.

[0130] Among them, S300 specifically includes:

[0131] S301. Wash the carbon felt intermediate material until it is nearly neutral and place it in a flat plate with a frame. The height of the frame is greater than the thickness of the carbon felt, and the height of the frame is about 8 mm. Pour the aqueous solution of carbon powder into the frame to immerse the upper surface of the carbon felt intermediate material to form a surface load, and the aqueous solution of carbon powder just needs to immerse the surface of the carbon felt intermediate material.

[0132] S302. After there is no obvious liquid flow on the surface of the carbon felt intermediate material, place it in an oven for drying treatment at a constant temperature to wrap the surface load. The oven temperature is set to 180 °C, and the constant temperature duration is set to 3.5 h.

[0133] S303. Repeat the above steps until the weight of the surface load accounts for 5% of the weight of the carbon felt to obtain the carbon felt finished material. Among them, the constant temperature duration of the last drying is set to 8 h, and after multiple drying treatments, the process of wrapping the surface load of the carbon felt intermediate material is completed.

[0134] Example 6

[0135] A preparation process of a carbon felt rich in functional groups, including:

[0136] S100. A step of oxidizing a pre-cut carbon felt with ozone to functionalize the surface of the carbon felt to obtain an intermediate carbon felt material.

[0137] Among them, S100 specifically includes:

[0138] S101. Add 50 L of water into a plexiglass columnar reactor, adjust the pH to 9 with sodium hydroxide, and then add an aqueous hydrogen peroxide solution with a content of 3% and a concentration of 37% to obtain an alkaline aqueous solution.

[0139] S102. Turn on the ozone generator, adjust the inlet gas flow rate to 2 L / min, and the ozone concentration to 120 mg / L, and introduce ozone into the reactor by bottom aeration.

[0140] S103. Place the pre-cut carbon felt with dimensions of 40 cm * 50 cm in the alkaline aqueous solution and carry out an oxidation reaction for 12 h to functionalize the surface of the carbon felt to obtain an intermediate carbon felt material.

[0141] S200. A step of preparing an aqueous solution of carbon powder containing an adhesive.

[0142] Among them, S200 specifically includes:

[0143] S201. Mix 1 g of polyethylene glycol and 60 g of BP2000 evenly at a temperature of 100 °C. The molecular weight of polyethylene glycol is 1500. After cooling, pyrolyze it in an atmosphere of 900 °C with a volume ratio of ammonia to hydrogen of 1:1 to obtain BP2000 rich in groups.

[0144] S202. Use the BP2000 rich in groups as a raw material to prepare an aqueous solution of BP2000 with a weight ratio of 2%, and add a 5% Nafion solution to obtain an aqueous solution of carbon powder, where the weight ratio of Nafion in the aqueous solution of carbon powder is 22% of the carbon material.

[0145] S300. A step of immersing the intermediate carbon felt material with the aqueous solution of carbon powder and drying it to wrap the surface loading of the intermediate carbon felt material to obtain a finished carbon felt.

[0146] Among them, S300 specifically includes:

[0147] S301. Wash the intermediate carbon felt to near neutrality and place it in a flat plate with a frame. The height of the frame is greater than the thickness of the carbon felt. The height of the frame is about 8 mm. Pour the aqueous solution of carbon powder into the frame to immerse the upper surface of the intermediate carbon felt to form a surface loading, and the aqueous solution of carbon powder just needs to immerse the surface of the intermediate carbon felt.

[0148] S302. After there is no obvious liquid flow on the surface of the carbon felt intermediate material, place it in an oven and dry it at a constant temperature to wrap the surface load. The oven temperature is set at 180°C and the constant temperature duration is set at 4h;

[0149] S303. Repeat the above steps until the weight of the surface load accounts for 6% of the weight of the carbon felt to obtain the carbon felt finished product. Among them, the constant temperature duration of the last drying is set at 7h. After multiple drying treatments, the process of wrapping the surface load of the carbon felt intermediate material is completed.

[0150] Among them, Example 1 is the optimal example. The carbon felt finished product obtained by the preparation process of Example 1 is used as the raw material to process the carbon felt electrode for performance testing. The specific testing method is as follows.

[0151] Test Example 1

[0152] Stack bipolar plates, carbon felts, proton membranes, frames, and current collectors of the same size into a stack unit structure. Among them, a single cell includes a first bipolar plate, a first carbon felt electrode, a proton membrane, a second carbon felt electrode, and a second bipolar plate arranged in sequence. Among them, both the first carbon felt electrode and the second carbon felt electrode are carbon felt electrodes processed from the carbon felt finished product obtained by the preparation process of Example 1 as the raw material. Several stack unit structures form the required stack. The electrolyte used includes 1.7 mol of vanadium ions with an average valence state of 3.5, 2 mol / L of sulfuric acid, 4 mol / L of hydrochloric acid, and 5% of methanesulfonic acid based on the total acid weight to improve the stability of the electrolyte. Set the current at 200 A to operate the battery stack. After the operation is stable, perform performance testing. The performance parameters that can be tested include: Coulomb efficiency, energy efficiency, energy efficiency decay after continuous operation 500 times, etc.

[0153] Test Example 2

[0154] Stack bipolar plates, carbon felts, proton membranes, frames, and current collectors of the same size into a stack unit structure. Among them, a single cell includes a first bipolar plate, a first carbon felt electrode, a proton membrane, a second carbon felt electrode, and a second bipolar plate arranged in sequence. Among them, both the first carbon felt electrode and the second carbon felt electrode are carbon felt electrodes processed from the carbon felt finished product obtained by the preparation process of Example 1 as the raw material. Several stack unit structures form the required stack. The electrolyte used includes 1.7 mol of vanadium ions with an average valence state of 3.5, 2 mol / L of sulfuric acid, 4 mol / L of hydrochloric acid, and 5% of methanesulfonic acid based on the total acid weight to improve the stability of the electrolyte. Set the current at 250 A to operate the battery stack. After the operation is stable, perform performance testing. The performance parameters that can be tested include: Coulomb efficiency, energy efficiency, energy efficiency decay after continuous operation 500 times, etc.

[0155] Test Example 3

[0156] Stack bipolar plates, carbon felts, proton exchange membranes, frames, and current collectors of the same size to form a stack unit structure. Among them, a single cell includes a first bipolar plate, a first carbon felt electrode, a proton exchange membrane, a second carbon felt electrode, and a second bipolar plate arranged in sequence. Among them, both the first carbon felt electrode and the second carbon felt electrode are carbon felt electrodes processed from carbon felt materials obtained by the preparation process of Example 1 as raw materials. Several stack unit structures constitute the required stack. The electrolyte used includes 1.7 mol of vanadium ions with an average valence state of 3.5, 2 mol / L of sulfuric acid, 4 mol / L of hydrochloric acid, and 5% of methanesulfonic acid by weight of the total acid to improve the stability of the electrolyte. Set the current to 320 A to operate the battery stack. After the operation is stable, perform performance tests. The performance parameters to be tested can include: Coulomb efficiency, energy efficiency, energy efficiency decay after continuous operation for 500 times, etc.

[0157] Comparative Example 1

[0158] Stack bipolar plates, carbon felts, proton exchange membranes, frames, and current collectors of the same size to form a stack unit structure. Among them, a single cell includes a first bipolar plate, a first carbon felt electrode, a proton exchange membrane, a second carbon felt electrode, and a second bipolar plate arranged in sequence. Among them, both the first carbon felt electrode and the second carbon felt electrode are carbon felt electrodes without any treatment, with a size of 40 cm * 50 cm. Several stack unit structures constitute the required stack. The electrolyte used includes 1.7 mol of vanadium ions with an average valence state of 3.5, 2 mol / L of sulfuric acid, 4 mol / L of hydrochloric acid, and 5% of methanesulfonic acid by weight of the total acid to improve the stability of the electrolyte. Set the current to 200 A to operate the battery stack. After the operation is stable, perform performance tests. The performance parameters to be tested can include: Coulomb efficiency, energy efficiency, energy efficiency decay after continuous operation for 500 times, etc.

[0159] Comparative Example 2

[0160] Stack bipolar plates, carbon felts, proton exchange membranes, frames, and current collectors of the same size to form a stack unit structure. Among them, a single cell includes a first bipolar plate, a first carbon felt electrode, a proton exchange membrane, a second carbon felt electrode, and a second bipolar plate arranged in sequence. Among them, both the first carbon felt electrode and the second carbon felt electrode are carbon felt electrodes without any treatment, with a size of 40 cm * 50 cm. Several stack unit structures constitute the required stack. The electrolyte used includes 1.7 mol of vanadium ions with an average valence state of 3.5, 2 mol / L of sulfuric acid, 4 mol / L of hydrochloric acid, and 5% of methanesulfonic acid by weight of the total acid to improve the stability of the electrolyte. Set the current to 250 A to operate the battery stack. After the operation is stable, perform performance tests. The performance parameters to be tested can include: Coulomb efficiency, energy efficiency, energy efficiency decay after continuous operation for 500 times, etc.

[0161] Comparative Example 3

[0162] Bipolar plates, carbon felts, proton exchange membranes, frames and current collectors of the same size are stacked into a stack unit structure. Among them, a single cell includes a first bipolar plate, a first carbon felt electrode, a proton exchange membrane, a second carbon felt electrode and a second bipolar plate arranged in sequence. Among them, both the first carbon felt electrode and the second carbon felt electrode are carbon felt electrodes without any treatment, with a size of 40 cm * 50 cm, and several stack unit structures form the required stack. The electrolyte used includes 1.7 mol of vanadium ions with an average valence state of 3.5, 2 mol / L of sulfuric acid, 4 mol / L of hydrochloric acid, and methanesulfonic acid accounting for 5% of the total acid weight to improve the stability of the electrolyte. Set the current to 320 A to operate the battery stack, and perform performance tests after the operation is stable. The performance parameters to be tested can include: Coulomb efficiency, energy efficiency, energy efficiency decay after continuous operation for 500 times, etc.

[0163] The performance parameters of each test example and comparative example are shown in the following table:

[0164]

[0165] As can be seen from the above table, the Coulomb efficiency and energy efficiency during operation of the carbon felt electrode prepared by the preparation process of the present invention are significantly higher than those of the carbon felt electrode without treatment, and the energy efficiency decay after 500 times of operation is significantly reduced.

[0166] The above embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can be made, which are all equivalent modifications and evolutions of the above embodiments based on the essence of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. A preparation process of a carbon felt rich in functional groups, characterized in that, Including: The step of oxidizing the pre-cut carbon felt with ozone to functionalize the surface of the carbon felt to obtain a carbon felt intermediate material, specifically including: Configuring an alkaline aqueous solution with a pH of 8-12 in a reactor; Introducing ozone into the reactor by bottom aeration; Placing the pre-cut carbon felt in the alkaline aqueous solution and continuously oxidizing for 8-24 h to functionalize the surface of the carbon felt to obtain a carbon felt intermediate material; The step of preparing an aqueous solution of carbon powder containing a binder, specifically including: Mixing polyethylene glycol and carbon material evenly at a mass ratio of 1:10-1:100 under a temperature condition of 100-200 °C, cooling, and then pyrolyzing under an atmosphere with a volume ratio of ammonia to hydrogen of 1:1 at 700-1050 °C to obtain a carbon material rich in groups; Using the carbon material rich in groups as a raw material to configure an aqueous solution, and adding a binder to obtain an aqueous solution of carbon powder, wherein the weight ratio of the binder in the aqueous solution of carbon powder is 20%-30% of the carbon material; The step of using the aqueous solution of carbon powder to immerse the carbon felt intermediate material and drying to wrap the surface load of the carbon felt intermediate material to obtain a carbon felt finished product, specifically including: Placing the carbon felt intermediate material in a flat plate with a frame, pouring the aqueous solution of carbon powder into the frame to immerse the upper surface of the carbon felt intermediate material to form a surface load; After there is no obvious liquid flow on the surface of the carbon felt intermediate material, placing it in an oven for drying at a constant temperature to wrap the surface load; Repeating the above steps until the weight of the surface load accounts for 3%-10% of the weight of the carbon felt to obtain a carbon felt finished product.

2. The preparation process of the carbon felt rich in functional groups according to claim 1, characterized in that, The preparation method of the alkaline aqueous solution is: Adding an appropriate amount of aqueous solution to the reactor, adjusting the pH to 8-12 with sodium hydroxide, and then adding an oxidant to obtain an alkaline aqueous solution.

3. The preparation process of the carbon felt rich in functional groups according to claim 1 or 2, characterized in that, When introducing ozone, the inlet gas flow rate is adjusted to 1.8-2.5 L / min, and the ozone concentration is 80-120 mg / L.

4. The preparation process of the carbon felt rich in functional groups according to claim 3, characterized in that, The carbon material uses EC600 or BP2000; the binder uses Nafion, PVDF or PTFE.

5. The preparation process of the carbon felt rich in functional groups according to claim 4, characterized in that, During the drying treatment, the drying temperature is controlled at 160-200 °C, the drying time for each time is 3.5-4 h, and the drying time for the last time is 7-8 h.

6. A carbon felt electrode, characterized in that, Made from the carbon felt finished product prepared by the preparation process according to any one of claims 1-5 as the raw material.

7. A flow battery, characterized in that, Including a first bipolar plate, a first carbon felt electrode, a proton membrane, a second carbon felt electrode, and a second bipolar plate arranged in sequence, wherein both the first carbon felt electrode and the second carbon felt electrode use the carbon felt electrode as described in claim 6.

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