Electrochemical oxidation resistant carbon felt for flow battery as well as preparation method and application of electrochemical oxidation resistant carbon felt

Abstract

The invention provides an electrochemical oxidation resistant carbon felt for a flow battery and a preparation method and application thereof, the electrochemical oxidation resistant carbon felt comprises a carbon felt and a carbon protection layer loaded on the surface of the carbon felt, and the orbital hybridization mode of carbon atoms in the carbon protection layer comprises sp3 hybridization. The electrochemical oxidation resistant carbon felt provided by the invention not only effectively prevents the oxidation corrosion of the carbon felt and the side reaction of electrolyzed water under high potential, but also improves the interface contact between a carbon felt electrode material and electrolyte, enhances the ion transmission characteristic of an electrode, and improves the electrochemical performance of a battery; moreover, the preparation method provided by the invention is simple and convenient, byproducts generated in the whole preparation process are gaseous and liquid, a waste gas treatment system can conveniently treat the byproducts, and industrial production is easy.

Description

Technical Field

[0001] This invention belongs to the field of redox flow batteries, and relates to an anti-electrochemical oxidation carbon felt for flow batteries, its preparation method and application. Background Technology

[0002] Redox flow batteries have advantages such as high energy density, good scalability, long service life, low maintenance cost, and environmental friendliness. They can be used in grid-side energy storage and shared energy storage projects to help grid peak shaving, frequency regulation, and emergency power supply. In addition, flow battery energy storage devices can also be used in conjunction with renewable energy devices to smooth out the fluctuations in power transmission from renewable energy devices. They have broad application prospects in electrochemical energy storage and large-scale energy storage devices.

[0003] Vanadium redox flow batteries are currently the most mature energy storage system among flow battery energy storage devices. The aqueous vanadium solution they rely on exhibits high cycle stability, safety, and reliability at room temperature and pressure, showing promising industrialization prospects. Compared to vanadium redox flow batteries, organic flow batteries have easier-to-control organic active molecules, mature organic synthesis methods, and can effectively reduce costs through customized organic molecule strategies. Furthermore, they possess high solubility in neutral systems, effectively avoiding the use of high-concentration acid and alkali solutions, thus showing broad application prospects in the flow battery energy storage field. Cerium-based flow batteries have a higher open-circuit potential than vanadium redox flow batteries, exhibiting superior power characteristics, and compared to vanadium (V₂O₃) cathode batteries... 2+ / VO 2+ Electrolyte, cerium (Ce) 3+ / Ce 4+ The electrolyte is cheaper and less biotoxic. Therefore, rare earth-based vanadium-cerium flow batteries have significant advantages in the field of flow battery energy storage.

[0004] Electrode materials, as a key component of flow batteries, determine the battery's lifespan and energy density. Carbon felt materials are widely used in flow batteries due to their excellent three-dimensional porous structure and good conductivity. However, traditional carbon felt electrodes still face some problems, such as low conductivity and poor catalytic activity. In flow batteries, the main factor affecting battery performance in carbon felt cathode materials is that carbon felt is easily oxidized at high cathode potentials, leading to intensified side reactions in water electrolysis, causing cathode corrosion, and affecting the stability and electrochemical performance of the flow battery.

[0005] Therefore, developing anti-electrochemical oxidation carbon felt for flow batteries to avoid the decrease in stability and degradation of electrochemical performance of flow batteries caused by carbon felt corrosion and the aggravation of side reactions in water electrolysis is of great practical significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an anti-electrochemical oxidation carbon felt for flow batteries, its preparation method, and its application. The anti-electrochemical oxidation carbon felt provided by the present invention not only effectively prevents carbon felt oxidation corrosion and water electrolysis side reactions at high potentials, but also improves the interfacial contact between the carbon felt electrode material and the electrolyte, enhances the ion transport characteristics of the electrode, and improves the electrochemical performance of the battery. Furthermore, the preparation method provided by the present invention is simple, and the byproducts generated throughout the process are all gaseous and liquid, facilitating treatment by waste gas treatment systems and making it suitable for industrial production.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an electrochemically resistant carbon felt for a flow battery, the electrochemically resistant carbon felt comprising a carbon felt and a carbon protective layer loaded on the surface of the carbon felt, wherein the carbon atoms in the carbon protective layer have an orbital hybridization mode including sp 3 Hybridization.

[0009] In this invention, sp 3 Hybridized carbon atoms compared to sp or sp 2 Hybridized carbon atoms possess greater stability, thus more effectively preventing carbon felt oxidation corrosion and water electrolysis side reactions. Furthermore, this carbon protective layer improves the interfacial contact between the carbon felt electrode material and the electrolyte, enhancing the electrode's ion transport characteristics and improving its electrochemical performance. Therefore, when applied to flow battery electrodes, it can significantly reduce corrosion of carbon felt electrode materials at high potentials, while simultaneously improving the flow battery's performance.

[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0011] Preferably, with the total number of carbon atoms being 100 at%, the sp 3 The percentage of hybridized carbon atoms is 5 at% to 100 at%, more preferably 30 at% to 50 at%, such as 5 at%, 20 at%, 30 at%, 35 at%, 40 at%, 45 at%, 50 at%, 60 at%, 70 at%, 90 at% or 100 at%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0012] In this invention, when sp 3The proportion of hybridized carbon atoms ranges from 5% to 50%. A higher proportion results in stronger resistance to electrochemical oxidation of the carbon felt. However, when the proportion exceeds 50%, the improvement in resistance slows down, and the electrochemical performance of the electrode begins to decline. Therefore, controlling the proportion within the range of 30 at% to 50 at% ensures that both the oxidation resistance and electrochemical performance of the carbon felt are at an optimal level.

[0013] Preferably, the carbon protective layer further includes doping elements.

[0014] Preferably, the doping element includes any one or a combination of at least two of boron, sulfur, selenium, nitrogen, oxygen or transition metals, and more preferably any one or a combination of at least two of boron, sulfur, selenium, nitrogen or cobalt.

[0015] In this invention, when the above-mentioned elements are doped into the carbon protective layer, the doping elements can provide catalytic active sites and increase charge density, thereby enhancing charge transport, further improving the catalytic activity of the carbon protective layer, and improving the electrochemical performance of the carbon felt.

[0016] Preferably, the atomic percentage of the dopant element in the carbon protective layer is 1 at% to 30 at%, more preferably 3 at% to 10 at%, such as 1 at%, 3 at%, 5 at%, 7 at%, 9 at%, 10 at%, 15 at%, 20 at%, 25 at% or 30 at%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0017] In this invention, when the atomic ratio of the dopant element is controlled within the above-mentioned preferred range, the carbon felt can better balance its antioxidant capacity and electrochemical performance.

[0018] In a second aspect, the present invention provides a method for preparing an anti-electrochemical oxidation carbon felt as described in the first aspect, the method comprising: first activating the carbon felt, and then loading a substance with sp onto the surface of the activated carbon felt. 3 Carbon protective layer for hybrid orbitals.

[0019] This invention first activates the carbon felt, and then prepares a surface layer with sp... 3 The carbon protective layer of the hybrid orbitals effectively suppresses corrosion of the carbon felt electrode and the occurrence of side reactions in water electrolysis, while improving the electrochemical performance of the carbon felt electrode material and increasing the efficiency of the flow battery. The preparation method provided by this invention is simple, and the byproducts generated throughout the process are all in gaseous and liquid states, which facilitates treatment by waste gas treatment systems and is easy for industrial production.

[0020] Preferably, the loading method includes any one of chemical vapor deposition, physical vapor deposition, electrochemical synthesis, or thermal treatment, with thermal treatment being the preferred method.

[0021] Preferably, the heat treatment method includes: immersing the activated carbon felt in a precursor solution, and then taking it out for calcination, wherein the precursor solution includes a carbon source and a solvent.

[0022] Preferably, the carbon source includes any one or a combination of at least two of hydrocarbons, hydrocarbon derivatives, or sugars.

[0023] Preferably, the mass concentration of the carbon source in the precursor solution is 5wt% to 90wt%, such as 5wt%, 10wt%, 15wt%, 20wt%, 30wt%, 50wt%, 70wt%, or 100wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0024] Preferably, the hydrocarbon derivatives include any one or a combination of at least two of alcohols, phenols, aldehydes, ketones, esters, amines, nitro compounds or urea compounds, and more preferably esters.

[0025] Preferably, the esters include polyester resins.

[0026] It should be noted that the polyester resin in this invention can be purchased directly or synthesized in a laboratory. For example, the synthesis method includes: polymerizing terephthalic acid and ethylene glycol at 200°C to 300°C under a nitrogen atmosphere. The temperature is, for example, 200°C, 220°C, 250°C, 270°C or 300°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] In this invention, esters are more suitable for preparing carbon protective layers due to their mild pyrolysis properties and good solubility; in particular, when the ester is a polyester resin, its cross-linked three-dimensional network structure can restrict the movement of carbon atoms during carbonization, thus making it easier to prepare sp... 3 A carbon protective layer with a relatively high proportion.

[0028] Preferably, the average molecular weight of the polyester resin is 3500 to 4500, such as 3500, 3700, 4000, 4200 or 4500, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the mass concentration of the ester in the precursor solution is 12wt% to 25wt%, such as 12wt%, 15wt%, 17wt%, 20wt%, 22wt%, or 25wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0030] Preferably, the mass concentration of the polyester resin in the precursor solution is 12wt% to 18wt%, such as 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, or 18wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, when the carbon source is a sugar, the precursor solution further includes an auxiliary agent, which includes nitrogen-containing organic compounds and / or sulfur-containing organic compounds.

[0032] Preferably, the mass ratio of the sugar to the additive is (2-4):1, such as 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] In this invention, because carbohydrates can generate a large number of HMF intermediates and small organic molecules during pyrolysis, they are prone to rearrangement and polymerization, resulting in disordered sp... 3 Hybrid structure, and additives can increase sp during pyrolysis. 3 The proportion of hybrid carbon is important; therefore, when an auxiliary agent is added to the precursor solution and the mass ratio of the sugar carbon source to the auxiliary agent is controlled within the above range, it is more beneficial to obtain sp. 3 A carbon protective layer with a high degree of hybridization.

[0034] Preferably, the total mass of the sugars and auxiliaries in the precursor solution is 20wt% to 25wt%, such as 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, or 25wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0035] In this invention, by controlling the total mass concentration of esters, sugars, and auxiliaries within the aforementioned preferred range, and further controlling the mass concentration of polyester resin within the range of 12wt% to 18wt%, the prepared carbon protective layer can achieve a higher concentration of sp... 3 A hybrid carbon atom ratio in the range of 30 at% to 50 at% is more conducive to improving the overall performance of carbon felt.

[0036] Preferably, the precursor solution further includes additives.

[0037] Preferably, the additive comprises any one or a combination of at least two of soluble boron-containing compounds, sulfur-containing compounds, selenium-containing compounds, or transition metal salts.

[0038] Preferably, the boron-containing compound includes boric acid, the sulfur-containing compound includes sodium sulfide, and the selenium-containing compound includes sodium selenide.

[0039] Preferably, the mass concentration of the additive in the precursor solution is 3wt% to 30wt%, more preferably 3wt% to 10wt%, such as 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 15wt%, 20wt%, 25wt%, or 30wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0040] Preferably, the soaking time is 10 min to 30 min, such as 10 min, 15 min, 20 min, 25 min or 30 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Preferably, the impregnation is performed under ultrasonic conditions.

[0042] Preferably, the power of the ultrasound is 600W to 1000W, such as 600W, 700W, 800W, 900W or 1000W, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, after the impregnation is completed, the carbon felt is subjected to a first wash and a first dry in sequence.

[0044] Preferably, the temperature of the first drying is 60℃ to 100℃, such as 60℃, 70℃, 80℃, 90℃ or 100℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, the first drying time is 1h to 3h, such as 1h, 1.5h, 2h, 2.5h or 3h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the calcination is carried out in a protective gas or reducing gas atmosphere.

[0047] Preferably, the reducing gas includes carbon monoxide or methane.

[0048] Preferably, the protective gas includes nitrogen.

[0049] Preferably, the flow rate of the protective gas or reducing gas is 80 mL / min to 120 mL / min, such as 80 mL / min, 90 mL / min, 100 mL / min, 110 mL / min or 120 mL / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] Preferably, the calcination temperature is 750℃~850℃, such as 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃ or 850℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] In this invention, the calcination temperature affects the form of carbon atoms. When controlled within the preferred range described above, the chemical bonds in the carbon source can obtain sufficient energy for bond breaking and rearrangement within the temperature range of 750°C to 850°C. Too low a temperature leads to insufficient bond breaking, while too high a temperature results in excessive graphitization and the formation of sp atoms. 2 Therefore, a calcination temperature of 750℃~850℃ is more conducive to the carbon atoms in the carbon source using sp electrons. 3 Hybrid bonding occurs.

[0052] Preferably, the calcination time is 1 hour to 3 hours, such as 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Preferably, the activation treatment includes immersing the carbon felt in an acidic solution.

[0053] Preferably, the mass concentration of the acidic solution is 10wt% to 15wt%, such as 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, or 15wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] In this invention, carbon felt with impurity groups removed can be obtained by activating the carbon felt with a low-concentration acid solution.

[0055] Preferably, the activation treatment temperature is 20℃ to 100℃, such as 20℃, 40℃, 60℃, 80℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0056] Preferably, the activation treatment time is 2h to 4h, such as 2h, 2.5h, 3h, 3.5h or 4h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] Preferably, after the soaking is completed, the carbon felt is subjected to a second washing and a second drying in sequence.

[0058] Preferably, the temperature of the second drying is 80°C to 120°C, such as 80°C, 90°C, 100°C, 110°C or 120°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0059] Preferably, the second drying time is 2h to 4h, such as 2h, 2.5h, 3h, 3.5h or 4h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] Thirdly, the present invention also provides an application of the anti-electrochemical oxidation carbon felt as described in the first aspect, the application including its application in a flow battery.

[0061] Preferably, the flow battery comprises a rare-earth-based vanadium-cerium flow battery.

[0062] Preferably, the operating voltage of the flow battery is 0.6V to 2.4V, such as 0.6V, 0.8V, 1V, 1.3V, 1.5V, 1.8V, 2V or 2.4V, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] The anti-electrochemical oxidation carbon felt provided by this invention can effectively prevent carbon felt oxidation corrosion and water electrolysis side reactions at high potentials, thus making it more suitable for rare earth-based vanadium-cerium redox flow batteries with higher operating voltages. Compared with the prior art, this invention has the following advantages:

[0064] The anti-electrochemical oxidation carbon felt provided by this invention not only effectively prevents the oxidation and corrosion of carbon felt and the side reactions of water electrolysis under high potential, but also improves the interfacial contact between the carbon felt electrode material and the electrolyte, enhances the ion transport characteristics of the electrode, and improves the electrochemical performance of the battery. Furthermore, the preparation method provided by this invention is simple, and the byproducts generated in the entire process are all in gaseous and liquid states, which facilitates the treatment of waste gas by the waste gas treatment system and is easy for industrial production. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the structure and effect of the anti-electrochemical oxidation carbon felt provided in Example 1.

[0066] Figure 2 This is the carbon dioxide electrochemical differential mass spectrum of a rare-earth-based vanadium-cerium redox flow battery using Example 7 as the positive electrode material.

[0067] Figure 3This is the oxygen electrochemical differential mass spectrum of a rare-earth-based vanadium-cerium flow battery using Example 7 as the positive electrode material.

[0068] Figure 4 This is the carbon dioxide electrochemical differential mass spectrum of a rare-earth-based vanadium-cerium flow battery using Comparative Example 1 as the cathode material.

[0069] Figure 5 This is the oxygen electrochemical differential mass spectrum of a rare-earth-based vanadium-cerium flow battery using Comparative Example 1 as the positive electrode material. Detailed Implementation

[0070] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0071] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0072] Example 1

[0073] This embodiment provides an anti-electrochemical oxidation carbon felt for use in flow batteries, such as... Figure 1 As shown, it includes a carbon felt and a carbon protective layer supported on the surface of the carbon felt. The carbon protective layer contains carbon and doped boron, wherein the carbon atoms are bonded in the manner of sp... 3 Hybridization, sp 3 Hybridized carbon atoms account for 40 at% of the total number of carbon atoms, and boron accounts for 5 at% of the carbon protective layer. The preparation method is as follows:

[0074] (1) Soak the carbon felt in a 10wt% hydrochloric acid solution and activate it at 25°C for 3 hours. Then rinse it repeatedly with deionized water until the pH value is 7. Place the rinsed carbon felt in an oven at 80°C and dry it for 3 hours to obtain the activated carbon felt.

[0075] (2) Dissolve the carbon source polyester resin and the additive boric acid in ethanol to obtain a precursor solution with a polyester resin mass concentration of 15wt% and a boric acid mass concentration of 5wt%. Then, immerse the activated carbon felt in the precursor solution and place it in an ultrasonic cleaner with a power of 1000W at 25℃ for 30min. After immersion, place it in an oven at 80℃ for 2h to dry.

[0076] (3) The dried carbon felt was placed in a tube furnace and calcined at 800°C for 2 hours in a nitrogen atmosphere with a flow rate of 100 mL / min to obtain the anti-electrochemical oxidation carbon felt.

[0077] In step (2), the polyester resin is obtained by polymerizing phthalic acid and ethylene glycol at 250°C under a nitrogen atmosphere.

[0078] Example 2

[0079] This embodiment provides an anti-electrochemical oxidation carbon felt for a flow battery, comprising a carbon felt and a carbon protective layer loaded on the surface of the carbon felt. The carbon protective layer contains carbon and doped boron, wherein the carbon atoms are bonded in a sp... 3 Hybridization, sp 3 Hybridized carbon atoms account for 30 at% of the total number of carbon atoms, and boron accounts for 3 at% of the carbon protective layer. The preparation method is as follows:

[0080] (1) Soak the carbon felt in a 12wt% hydrochloric acid solution and activate it at 20°C for 4 hours. Then rinse it repeatedly with deionized water until the pH value is 7. Place the rinsed carbon felt in an oven at 100°C and dry it for 2 hours to obtain the activated carbon felt.

[0081] (2) Dissolve the carbon source polyester resin and the additive boric acid in ethanol to obtain a precursor solution with a polyester resin mass concentration of 12wt% and a boric acid mass concentration of 3wt%. Then, immerse the activated carbon felt in the precursor solution and place it in an ultrasonic cleaner with a power of 600W for ultrasonic treatment at 20℃ for 20min. After immersion, place it in a 60℃ oven for drying for 3h.

[0082] (3) The dried carbon felt was placed in a tube furnace and calcined at 750°C for 3 hours in a nitrogen atmosphere with a flow rate of 80 mL / min to obtain the anti-electrochemical oxidation carbon felt.

[0083] In step (2), the polyester resin is obtained by polymerizing phthalic acid and ethylene glycol at 250°C under a nitrogen atmosphere.

[0084] Example 3

[0085] This embodiment provides an anti-electrochemical oxidation carbon felt for a flow battery, comprising a carbon felt and a carbon protective layer loaded on the surface of the carbon felt. The carbon protective layer contains carbon and doped boron, wherein the carbon atoms are bonded in a sp... 3 Hybridization, sp 3 Hybridized carbon atoms account for 50 at% of the total number of carbon atoms, and boron accounts for 10 at% of the carbon protective layer. The preparation method is as follows:

[0086] (1) Soak the carbon felt in a 15wt% hydrochloric acid solution and activate it at 100℃ for 2h. Then rinse it repeatedly with deionized water until the pH value is 7. Place the rinsed carbon felt in an oven at 120℃ and dry it for 2h to obtain the activated carbon felt.

[0087] (2) Dissolve the carbon source polyester resin and the additive boric acid in ethanol to obtain a precursor solution with a polyester resin mass concentration of 18wt% and a boric acid mass concentration of 10wt%. Then, immerse the activated carbon felt in the precursor solution and place it in an ultrasonic cleaner with a power of 800W at 30℃ for 10min. After immersion, place it in a 100℃ oven to dry for 1h.

[0088] (3) The dried carbon felt was placed in a tube furnace and calcined at 850°C for 1 hour in a nitrogen atmosphere with a flow rate of 120 mL / min to obtain the anti-electrochemical oxidation carbon felt.

[0089] In step (2), the polyester resin is obtained by polymerizing phthalic acid and ethylene glycol at 250°C under a nitrogen atmosphere.

[0090] Example 4

[0091] The difference between this embodiment and embodiment 1 is that in this embodiment, the carbon protective layer includes carbon and doped selenium, the atomic percentage of selenium in the carbon protective layer is 10 at%, the additive in step (2) is sodium selenide, and the molar concentration of sodium selenide is 0.1 mol / L.

[0092] The remaining preparation methods and parameters are consistent with those in Example 1.

[0093] Example 5

[0094] The difference between this embodiment and embodiment 1 is that in this embodiment, the carbon protective layer includes carbon and doped sulfur elements, and the atomic percentage of sulfur elements in the carbon protective layer is 10 at%, the additive in step (2) is sodium sulfide, and the molar concentration of sodium sulfide is 0.1 mol / L.

[0095] The remaining preparation methods and parameters are consistent with those in Example 1.

[0096] Example 6

[0097] The difference between this embodiment and embodiment 1 is that in this embodiment, the carbon protective layer includes carbon and doped cobalt, and the atomic percentage of cobalt in the carbon protective layer is 10 at%, the additive in step (2) of the preparation method is cobalt nitrate, and the mass concentration of cobalt nitrate is 5 wt%.

[0098] The remaining preparation methods and parameters are consistent with those in Example 1.

[0099] Example 7

[0100] The difference between this embodiment and embodiment 1 is that in this embodiment, the carbon protective layer contains only carbon and no doped elements, and no additives are added to the precursor solution in step (2).

[0101] The remaining preparation methods and parameters are consistent with those in Example 1.

[0102] Example 8

[0103] The difference between this embodiment and Embodiment 1 is that, in this embodiment, sp 3 Hybridized carbon atoms account for 15 at% of the total number of carbon atoms, and the mass concentration of polyester resin in step (2) is 5 wt%.

[0104] The remaining preparation methods and parameters are consistent with those in Example 1.

[0105] Example 9

[0106] The difference between this embodiment and Embodiment 1 is that, in this embodiment, sp 3 Hybridized carbon atoms account for 2 at% of the total number of carbon atoms. In step (2), the mass concentration of polyester resin is 1 wt%.

[0107] The remaining preparation methods and parameters are consistent with those in Example 1.

[0108] Example 10

[0109] The difference between this embodiment and embodiment 1 is that in this embodiment, step (2) uses triethyl citrate as a carbon source;

[0110] The remaining preparation methods and parameters are consistent with those in Example 1.

[0111] Example 11

[0112] The difference between this embodiment and embodiment 1 is that in this embodiment, cellulose is used as the carbon source in step (2), and urea is added to the precursor solution. The mass ratio of cellulose to urea is 3:1, and the total mass concentration of cellulose and urea in the precursor solution is 22wt%.

[0113] The remaining preparation methods and parameters are consistent with those in Example 1.

[0114] Example 12

[0115] The difference between this embodiment and embodiment 1 is that in this embodiment, step (2) uses 2-methylimidazole as the carbon source;

[0116] The remaining preparation methods and parameters are consistent with those in Example 1.

[0117] Example 13

[0118] The difference between this embodiment and embodiment 1 is that in this embodiment, the calcination temperature of step (3) is 700℃;

[0119] The remaining preparation methods and parameters are consistent with those in Example 1.

[0120] Example 14

[0121] The difference between this embodiment and embodiment 1 is that in this embodiment, the calcination temperature of step (3) is 900℃;

[0122] The remaining preparation methods and parameters are consistent with those in Example 1.

[0123] Comparative Example 1

[0124] The difference between this comparative example and Example 7 is that in this comparative example, the carbon felt does not have a carbon protective layer and steps (2) and (3) are not performed.

[0125] The remaining preparation methods and parameters are consistent with those in Example 7.

[0126] Comparative Example 2

[0127] The difference between this comparative example and Example 7 is that in this comparative example, the carbon felt does not have a carbon protective layer, steps (2) and (3) are not performed, and hydrochloric acid is replaced with sulfuric acid in step (1).

[0128] The remaining preparation methods and parameters are consistent with those in Example 7.

[0129] Comparative Example 3

[0130] The difference between this comparative example and Example 7 is that in this comparative example, the carbon felt does not have a carbon protective layer and step (2) is not performed.

[0131] The remaining preparation methods and parameters are consistent with those in Example 7.

[0132] Comparative Example 4

[0133] The difference between this comparative example and Example 7 is that in this comparative example, the carbon felt does not have a carbon protective layer, step (2) is not performed, and hydrochloric acid is replaced with sulfuric acid in step (1).

[0134] The remaining preparation methods and parameters are consistent with those in Example 7.

[0135] Comparative Example 5

[0136] The difference between this comparative example and Example 1 is that this comparative example does not perform step (1);

[0137] The remaining preparation methods and parameters are consistent with those in Example 1.

[0138] Performance testing

[0139] The carbon felts prepared in Examples 1-14 and Comparative Examples 1-5 were applied to rare earth-based vanadium-cerium flow batteries. The positive electrode solution was a 0.2M cerium solution with a volume of 20 mL, and the negative electrode solution was a 1M vanadium solution with a volume of 8 mL.

[0140] (1) Antioxidant performance test: Electrochemical differential mass spectrometry was used at a current density of 200 mA cm⁻¹. -1 The changes in oxygen and carbon dioxide in the battery were tested under constant current conditions: temperature 25℃, pump flow rate 60 mL / min. -1 The cutoff voltage is 0.6–2.4V. Test results are shown in Table 1 and... Figures 2-5 As shown.

[0141] (2) Battery energy efficiency test: at a current density of 40–200 mA cm⁻¹ -2 A single-cell constant-current charge-discharge test was conducted at a constant temperature of 25℃, with a cutoff voltage of 0.6–2.4V and a pump flow rate of 60 mL / min. -1 The battery's charge / discharge capacity is at a current density of 40 mA / cm². -1 A constant current test was conducted under the following conditions: temperature 25℃, pump flow rate 60 mL / min. -1 The cutoff voltage is 0.6 to 2.4V.

[0142] Table 1

[0143]

[0144]

[0145] Table 2

[0146]

[0147]

[0148] Depend on Figures 2-5It can be seen that Example 7, with its carbon protective layer, produced less carbon dioxide during single-cell testing compared to Comparative Example 1. This indicates that the anti-electrochemical oxidation protective carbon layer effectively prevents the carbon felt electrode from being corroded by oxygen. Furthermore, compared to Comparative Example 1, Example 7 produced almost no oxygen during single-cell testing, demonstrating that the carbon protective layer effectively suppressed the occurrence of side reactions in water electrolysis. The data results of Example 7 and Comparative Examples 2-4 in Table 1 further confirm the above advantages. Meanwhile, the comparison between Comparative Examples 1-2 and Comparative Examples 3-4 shows that even without preparing a carbon protective layer on the outer surface of the carbon felt, calcining the carbon felt improves its performance. The comparisons between Comparative Examples 1 and 2, and Comparative Examples 3 and 4, also show that hydrochloric acid activation achieves better results than sulfuric acid activation.

[0149] As can be seen from the comparison of data from Example 1 and Examples 8-14 in Table 1, the sp in the carbon protective layer 3 The proportion of hybridized carbon atoms, as well as the type of carbon source and calcination temperature used in the preparation process, also affect the performance of carbon felt. By controlling these within the preferred range of this invention, it is more beneficial to reduce side reactions of carbon felt during use and improve the electrochemical performance of the battery.

[0150] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A carbon felt resistant to electrochemical oxidation for use in flow batteries, characterized in that, The anti-electrochemical oxidation carbon felt comprises a carbon felt and a carbon protective layer loaded on the surface of the carbon felt, wherein the orbital hybridization of carbon atoms in the carbon protective layer includes sp... 3 Hybridization.

2. The anti-electrochemical oxidation carbon felt according to claim 1, characterized in that, With the total number of carbon atoms being 100 at%, the sp 3 The proportion of hybridized carbon atoms is 5 at% to 100 at%, more preferably 30 at% to 50 at%.

3. The anti-electrochemical oxidation carbon felt according to claim 1 or 2, characterized in that, The carbon protective layer also includes doping elements; Preferably, the doping element includes any one or a combination of at least two of boron, sulfur, selenium, nitrogen, oxygen or transition metals, and more preferably any one or a combination of at least two of boron, sulfur, selenium, nitrogen or cobalt. Preferably, the atomic percentage of the dopant element in the carbon protective layer is 1 at% to 30 at%, more preferably 3 at% to 10 at%.

4. A method for preparing an anti-electrochemical oxidation carbon felt as described in any one of claims 1-3, characterized in that, The preparation method includes: first activating the carbon felt, and then loading the activated carbon felt surface with sp... 3 Carbon protective layer for hybrid orbitals.

5. The preparation method according to claim 4, characterized in that, The loading method includes any one of chemical vapor deposition, physical vapor deposition, electrochemical synthesis or thermal treatment, preferably thermal treatment; Preferably, the heat treatment method includes: immersing the activated carbon felt in a precursor solution, and then taking it out for calcination, wherein the precursor solution includes a carbon source and a solvent; Preferably, the carbon source includes any one or a combination of at least two of hydrocarbons, hydrocarbon derivatives, or sugars; Preferably, the carbon source has a mass concentration of 5 wt% to 90 wt% in the precursor solution; Preferably, the hydrocarbon derivatives include any one or a combination of at least two of alcohols, phenols, aldehydes, ketones, esters, amines, nitro compounds or urea compounds, and more preferably esters; Preferably, the esters include polyester resins; Preferably, the average molecular weight of the polyester resin is 3500 to 4500; Preferably, the mass concentration of the ester in the precursor solution is 12 wt% to 25 wt%. Preferably, the mass concentration of the polyester resin in the precursor solution is 12wt% to 18wt%. Preferably, when the carbon source is a sugar, the precursor solution further includes an auxiliary agent, which includes nitrogen-containing organic compounds and / or sulfur-containing organic compounds; Preferably, the mass ratio of the sugars to the additives is (2-4):1; Preferably, the total mass of the sugars and auxiliaries in the precursor solution accounts for 20 wt% to 25 wt%.

6. The preparation method according to claim 5, characterized in that, The precursor solution also includes additives; Preferably, the additive comprises any one or a combination of at least two of the following: soluble boron-containing compounds, sulfur-containing compounds, selenium-containing compounds, nitrogen-containing compounds, or transition metal salts; Preferably, the boron-containing compound includes boric acid, the sulfur-containing compound includes sodium sulfide, and the selenium-containing compound includes sodium selenide. Preferably, the mass concentration of the additive in the precursor solution is 3 wt% to 30 wt%, more preferably 3 wt% to 10 wt%.

7. The preparation method according to claim 5 or 6, characterized in that, The immersion time is 10 min to 30 min; Preferably, the impregnation is performed under ultrasonic conditions; Preferably, the power of the ultrasound is 600W to 1000W; Preferably, the calcination is carried out in an atmosphere of protective gas or reducing gas; Preferably, the reducing gas includes carbon monoxide or methane; Preferably, the protective gas includes nitrogen; Preferably, the flow rate of the protective gas or reducing gas is 80 mL / min to 120 mL / min; Preferably, the calcination temperature is 750℃~850℃; Preferably, the calcination time is 1 hour to 3 hours.

8. The preparation method according to any one of claims 4-7, characterized in that, The activation treatment includes: immersing the carbon felt in an acidic solution; Preferably, the mass concentration of the acidic solution is 10 wt% to 15 wt%. Preferably, the activation treatment temperature is 20℃~100℃; Preferably, the activation treatment time is 2h to 4h.

9. The application of the anti-electrochemical oxidation carbon felt as described in any one of claims 1-3, characterized in that, The applications include those in flow batteries.

10. The application according to claim 9, characterized in that, The flow battery includes a rare-earth-based vanadium-cerium flow battery. Preferably, the operating voltage of the flow battery is 0.6V to 2.4V.

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