Carbon paper electrode for flow battery as well as preparation method and application of carbon paper electrode

Abstract

The invention relates to a preparation method of a carbon paper electrode for a flow battery, which comprises the following steps: impregnating carbon fiber raw paper in an impregnating solution, and then drying, carbonizing and activating to obtain the carbon paper electrode, wherein the impregnation liquid comprises resin, an electrocatalyst, a pore-forming agent and a solvent. According to the carbon paper electrode for the flow battery prepared by the preparation method disclosed by the invention, on one hand, the ohmic internal resistance of the battery is reduced, and the mass and the volume of the battery are reduced, and on the other hand, the prepared carbon paper electrode has uniformly distributed and adjustable pores by adding the pore forming agent, so that the liquid transmission capability of the flow battery is enhanced; the mass transfer resistance of the electrolyte is reduced, and the conductivity of the carbon paper is improved and the reaction activation energy of the positive electrode and the negative electrode is reduced by loading the electrocatalyst, so that the carbon paper has excellent electrochemical activity. In addition, the preparation method is simple and easy to implement, and industrial production is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a carbon paper electrode for a liquid flow battery and a preparation method and application thereof. Background Art

[0002] Electrode material is one of the key materials of liquid flow battery. The quality of its material performance directly affects the electrochemical reaction rate, battery internal resistance, and the uniformity and diffusion state of electrolyte distribution, and ultimately affects the power density and energy conversion efficiency of liquid flow battery. The electrode materials of all-vanadium liquid flow battery can be divided into metal electrode materials and carbon electrode materials according to the material type. Metal electrode materials have high electrical conductivity and good mechanical properties, but they are expensive and easily corroded. Currently, carbon electrode materials are mainly used, such as carbon felt, graphite felt, carbon cloth, carbon paper, etc. In contrast, carbon paper has excellent conductivity. Compared with carbon felt, it is thinner, making the battery components more compact and in good contact, which can greatly reduce the distance between the positive and negative electrodes of the all-vanadium liquid flow energy storage battery, thereby reducing the battery's ohmic internal resistance and reducing the battery's mass and volume.

[0003] However, although carbon paper can reduce the distance between electrodes and reduce the internal resistance of the battery, it also reduces the effective active area of ​​the electrode. To maintain a faster charge transfer kinetic rate and avoid a large electrode reaction polarization overpoint, the carbon paper electrode needs to have a higher electrochemical reaction activity. However, the untreated raw carbon paper has poor reaction activity and kinetic reversibility for all-vanadium liquid flow batteries, and it needs to be surface modified. In addition, the electrode material should have a stable three-dimensional network structure, moderate porosity and uniform distribution, providing a suitable channel for the flow of electrolyte to achieve effective transmission and uniform distribution of active substances.

[0004] At present, the electrocatalysts loaded on the surface of carbon fiber electrode materials are mainly introduced into the carbon fiber surface by ion exchange, impregnation reduction, chemical vapor deposition or electrochemical deposition, so as to enhance the electrochemical reaction activity of the electrode. The introduction of these active components improves the electrical conductivity of the carbon fiber on the one hand, and acts as an electrocatalyst on the other hand, changing the electrode reaction pathway, accelerating the reaction rate and reducing the polarization resistance of the electrode reaction.

[0005] Although the performance of modified carbon fiber electrodes has been improved, it is still necessary to provide more carbon paper electrodes with simple preparation methods and excellent performance. Summary of the invention

[0006] The purpose of the present invention is to provide a carbon paper electrode for a liquid flow battery with a simple preparation method and excellent performance, and a preparation method and application thereof.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A first aspect of the present invention provides a method for preparing a carbon paper electrode for a liquid flow battery, wherein a carbon fiber base paper is impregnated in an impregnation liquid, and then dried, carbonized, and activated to obtain the carbon paper electrode; wherein the impregnation liquid comprises a resin, an electrocatalyst, a pore-forming agent, and a solvent.

[0009] In the present invention, on the one hand, the pore-forming agent component added to the impregnation solution can form corresponding pores on the carbon paper during the drying or carbonization process, so that the final carbon paper electrode has uniform and controllable pores and the flow resistance of the electrolyte is small; on the other hand, active substances with electrocatalytic effects can be loaded on the carbon paper to improve the electrochemical activity of the electrode.

[0010] According to some specific embodiments, the solid content of the impregnation liquid is 10-35%, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%. Further, the solid content of the impregnation liquid is 20-35%.

[0011] The solid content of the impregnation liquid is calculated by dividing the total mass of the resin, the electrocatalyst and the pore-forming agent by the total mass of the impregnation liquid.

[0012] According to some specific embodiments, the mass of the electrocatalyst accounts for 5-35% of the mass of the solids in the impregnation solution, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%. Further, the mass of the electrocatalyst accounts for 5-20% of the mass of the solids in the impregnation solution.

[0013] According to some specific embodiments, the mass of the pore-forming agent accounts for 5-35% of the mass of the solids in the impregnation solution, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%. Further, the mass of the pore-forming agent accounts for 5-30% of the mass of the solids in the impregnation solution.

[0014] According to some specific embodiments, the mass of the resin accounts for 30-80% of the mass of the solids in the impregnation liquid, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%. Further, the mass of the resin accounts for 50-80% of the mass of the solids in the impregnation liquid, for example, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79% or 80%.

[0015] The solid mass in the impregnation solution is the total mass of the resin, the electrocatalyst and the pore-forming agent.

[0016] According to some specific embodiments, the resin is one or more of phenolic resin, furfural resin, furan resin, and epoxy resin.

[0017] According to some specific embodiments, the electrocatalyst is one or more of graphene, graphene oxide, and carbon nanotubes.

[0018] According to some specific embodiments, the solvent is one or both of deionized water and ethanol.

[0019] According to some specific embodiments, the pore former is an inorganic pore former or an organic pore former.

[0020] Furthermore, the inorganic pore-forming agent is one or more of ammonium bicarbonate, ammonium sulfate, sodium sulfate, and ammonium chloride.

[0021] Furthermore, the organic pore-forming agent is PS microspheres and / or methyl cellulose.

[0022] Furthermore, the particle size of the PS microspheres is 15 to 100 μm.

[0023] According to some specific embodiments, the impregnation liquid is prepared by mechanical dispersion. Furthermore, the mechanical dispersion time is controlled to be no less than 4 hours to ensure that the components in the impregnation liquid are evenly dispersed.

[0024] According to some specific embodiments, the carbon fiber base paper is a product obtained by papermaking from chopped carbon fibers, and is a PAN-based material.

[0025] According to some specific embodiments, the thickness of the carbon fiber base paper is 15 to 800 μm, for example, 15 μm, 25 μm, 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, 175 μm, 200 μm, 225 μm, 250 μm, 275 μm, 300 μm, 325 μm, 350 μm, 375 μm, 400 μm, 425 μm, 450 μm, 475 μm, 500 μm, 525 μm, 550 μm, 575 μm, 600 μm, 625 μm, 650 μm, 675 μm, 700 μm, 725 μm, 750 μm, 775 μm, and 800 μm. Furthermore, the thickness of the carbon fiber base paper is 400-800 μm, and the method of the present invention has a good performance improvement for the carbon fiber base paper with a thickness exceeding 400 μm.

[0026] According to some specific embodiments, after the carbon fiber base paper is impregnated, excess impregnation liquid is removed by squeezing with a pressing roller, and then the paper is dried.

[0027] Furthermore, the impregnation and extrusion are repeated 1 to 3 times to ensure that the carbon paper is evenly and fully impregnated.

[0028] According to some specific embodiments, the drying is performed using an oven or a heat press setting machine.

[0029] According to some specific embodiments, the drying temperature is controlled to be 100-300°C, for example, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C or 300°C.

[0030] According to some specific embodiments, the drying time is controlled to be 3 to 60 min, for example, 3 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0031] According to some specific embodiments, the carbonization is performed using a carbonization furnace.

[0032] According to some specific embodiments, the carbonization temperature is controlled to be 1500-2200°C, for example, 1500°C, 1550°C, 1600°C, 1650°C, 1700°C, 1750°C, 1800°C, 1850°C, 1900°C, 1950°C, 2000°C, 2050°C, 2100°C, 2150°C or 2200°C.

[0033] According to some specific embodiments, the carbonization time is controlled to be 5 to 10 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min.

[0034] According to some specific embodiments, the activation is performed using a muffle furnace.

[0035] According to some specific embodiments, the activation is performed under air atmosphere.

[0036] According to some specific embodiments, the activation is performed by heating the temperature to 350-600°C at a heating rate of 5-10°C / min. The heating rate is 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min. The activation temperature is 350°C, 400°C, 450°C, 500°C, 550°C or 600°C.

[0037] According to some specific embodiments, the activation is carried out by keeping warm for 0.5 to 48 hours. Wherein, the activation time is 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 38h, 39h, 40h, 41h, 42h, 43h, 44h, 45h, 46h, 47h or 48h.

[0038] A second aspect of the present invention provides a carbon paper electrode for a liquid flow battery produced by the above-described production method.

[0039] A third aspect of the present invention provides a liquid flow battery, which includes a carbon paper electrode prepared by the preparation method described above.

[0040] According to some specific embodiments, the flow battery is a vanadium flow battery.

[0041] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0042] The carbon paper electrode for liquid flow battery prepared by the preparation method of the present invention reduces the ohmic internal resistance of the battery, reduces the mass and volume of the battery, and on the other hand, by adding a pore-forming agent, the prepared carbon paper electrode has uniformly distributed and controllable pores, enhances the ability of the liquid flow battery to transmit liquid, reduces the mass transfer resistance of the electrolyte, and increases the conductivity of the carbon paper by loading an electrocatalyst, reduces the activation energy of the positive and negative electrode reactions, and makes the carbon paper have excellent electrochemical activity. In addition, the preparation method of the present invention is simple and easy to implement, and is convenient for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0044] In view of the shortcomings of the prior art, the present invention adopts Figure 1 The production process shown is used to prepare carbon paper electrodes. In addition, the present invention improves the conductivity of carbon paper and reduces the activation energy of positive and negative electrode reactions by adding a carbon-based electrocatalyst with a high specific surface area, such as carbon nanotubes, graphene, etc., to the impregnation slurry of carbon paper. The present invention adds a pore-forming agent to the impregnation slurry of carbon paper. The pore-forming agent is divided into two types: inorganic and organic, such as ammonium bicarbonate, ammonium chloride, PS microspheres, etc. This makes the pore distribution of carbon paper uniform, with a high porosity, reduces the flow resistance of the electrolyte, and has a higher battery performance.

[0045] The present invention is further described below in conjunction with the examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to the different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0046] Unless otherwise specified, the reagents, instruments, etc. used in the following examples are all commercially available products commonly used in the art, or can also be prepared by conventional preparation methods in the art. In the present invention, unless otherwise specified, the contents are all mass contents, "%" is mass percentage, and the number of parts is mass parts.

[0047] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Among them, the terms "optional" and "optional" all mean that they can be included or not (or can be included or not).

[0048] Example 1

[0049] Weigh 20 grams of graphene oxide, 30 grams of ammonium chloride, 60 grams of furfural resin, add 380 grams of deionized water, mix and put into a blender for thorough stirring and mixing. Use a carbon paper base with a thickness of 180 μm, cut it into a size of 15 cm × 15 cm, immerse it completely in the impregnation liquid, use a roller to squeeze out the excess impregnation liquid, and repeat the impregnation three times. Then place it in an oven for drying and curing at a temperature of 200 ° C for 30 minutes. The shaped carbon paper is placed in a carbonization furnace for carbonization at a carbonization temperature of 1800 ° C for 5 minutes. The carbonized carbon paper is placed in a muffle furnace, and in an air atmosphere, the temperature is raised to 400 ° C at a heating rate of 10 ° C / min for 36 hours to obtain a carbon paper electrode that can be used for a liquid flow battery as sample 1.

[0050] Example 2

[0051] Weigh 40g of carbon nanotubes, 20g of ammonium bicarbonate, 150g of phenolic resin, add 500g of deionized water, mix and put into a blender for thorough stirring and mixing. Use a carbon paper base with a thickness of 350μm, cut it into a size of 15cm×15cm, immerse it completely in the impregnation liquid, use a roller to squeeze out the excess impregnation liquid, and repeat the impregnation three times. Then put it in an oven for drying and curing at a temperature of 300℃ for 30 minutes. Put the shaped carbon paper into a carbonization furnace for carbonization at a carbonization temperature of 1800℃ for a treatment time of 5 minutes. Put the carbonized carbon paper into a muffle furnace, and heat it to 500℃ at a heating rate of 10℃ / min in an air atmosphere for 2h to obtain a carbon paper electrode that can be used for a liquid flow battery as sample 2.

[0052] Example 3

[0053] Weigh 20g of carbon nanotubes, 30g of PS microspheres, 180g of epoxy resin, add 500g of deionized water, mix and put into a blender for thorough stirring and mixing. Use a carbon paper base with a thickness of 450μm, cut it into a size of 15cm×15cm, immerse it completely in the impregnation liquid, use a roller to squeeze out the excess impregnation liquid, and repeat the impregnation three times. Then put it in an oven for drying and curing at a temperature of 300℃ for 60 minutes. Put the shaped carbon paper into a carbonization furnace for carbonization at a carbonization temperature of 1800℃ for a treatment time of 5 minutes. Put the carbonized carbon paper into a muffle furnace, and heat it to 500℃ at a heating rate of 10℃ / min in an air atmosphere for 2h to obtain a carbon paper electrode that can be used for a liquid flow battery as sample 3.

[0054] Comparative Example 1

[0055] In this example, the carbon paper base paper used in Example 1 was used without impregnation treatment. It was placed in a muffle furnace and heated to 400°C at a heating rate of 10°C / min for 36 hours in an air atmosphere to obtain a carbon paper electrode that can be used for a liquid flow battery, as Sample 4.

[0056] Comparative Example 2

[0057] The method is basically the same as Example 2, except that no ammonium bicarbonate pore former is added to the impregnation solution, which is sample 5.

[0058] Comparative Example 3

[0059] The method is basically the same as Example 3, except that no carbon nanotube electrocatalyst is added to the impregnation solution, which is referred to as Sample 6.

[0060] In order to further illustrate the technical effect of the embodiment of the present invention, the performance test of vanadium flow battery was carried out on different samples prepared in the above embodiment and comparative example. The charge and discharge instrument used was Xinwei charge and discharge tester. The vanadium electrolyte with a concentration of 1.6 mol / L and a valence of 3.5 was assembled into a single cell for testing. 2 The charge and discharge test was carried out at a current density of 1.50 W. The test results are shown in Table 1 below.

[0061] Table 1

[0062]

[0063] As can be seen from Table 1 above, the porous adjustable carbon paper of the present invention is used as an electrode of a vanadium flow battery and has excellent battery performance at 160 mA / cm 2 At the current density, the voltage efficiency can reach up to 87%.

[0064] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a carbon paper electrode for a flow battery, characterized in that: The carbon fiber base paper is impregnated in an impregnation liquid, and then dried, carbonized and activated to obtain the carbon paper electrode; wherein the impregnation liquid comprises a resin, an electrocatalyst, a pore-forming agent and a solvent.

2. The method for preparing a carbon paper electrode for a flow battery according to claim 1, characterized in that: The solid content of the impregnation liquid is 10-35%, the mass of the electrocatalyst accounts for 5-35% of the solid mass in the impregnation liquid, the mass of the pore former accounts for 5-35% of the solid mass in the impregnation liquid, and the mass of the resin accounts for 30-80% of the solid mass in the impregnation liquid.

3. The method for preparing a carbon paper electrode for a flow battery according to claim 1, characterized in that: The resin is one or more of phenolic resin, furfural resin, furan resin, and epoxy resin; the electrocatalyst is one or more of graphene, graphene oxide, and carbon nanotubes; and the solvent is one or both of deionized water and ethanol.

4. The method for preparing a carbon paper electrode for a flow battery according to claim 1, characterized in that: The pore-forming agent is an inorganic pore-forming agent or an organic pore-forming agent; the inorganic pore-forming agent is one or more of ammonium bicarbonate, ammonium sulfate, sodium sulfate, and ammonium chloride; the organic pore-forming agent is PS microspheres and / or methyl cellulose.

5. The method for preparing a carbon paper electrode for a flow battery according to claim 1, characterized in that: The carbon fiber base paper is a product obtained by papermaking from chopped carbon fibers, and is a PAN-based material; and / or the thickness of the carbon fiber base paper is 15 to 800 μm.

6. The method for preparing a carbon paper electrode for a flow battery according to claim 1, characterized in that: After the carbon fiber base paper is impregnated, excess impregnation liquid is removed by squeezing with a pressing roller, and then the paper is dried; the impregnation and squeezing are repeated 1 to 3 times.

7. The method for preparing a carbon paper electrode for a flow battery according to claim 1, characterized in that: The drying is performed using an oven or a heat press setting machine; and / or, The drying temperature is controlled to be 100-300° C. and the drying time is controlled to be 3-60 min; and / or, The carbonization is performed using a carbonization furnace; and / or, Controlling the carbonization temperature to be 1500-2200° C. and the carbonization time to be 5-10 min; and / or, The activation is performed using a muffle furnace; and / or, The activation is carried out under an air atmosphere; and / or, The activation is performed by heating the mixture to 350-600° C. at a heating rate of 5-10° C. / min and maintaining the temperature for 0.5-48 hours.

8. A carbon paper electrode for a liquid flow battery prepared by the preparation method according to any one of claims 1 to 7.

9. A liquid flow battery, characterized in that: It comprises a carbon paper electrode prepared by the preparation method according to any one of claims 1 to 7.

10. The liquid flow battery according to claim 9, characterized in that: The liquid flow battery is a vanadium liquid flow battery.

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