CN117276560A

CN117276560A - Method for batch treatment of carbon-based electrode for flow battery

Info

Publication number: CN117276560A
Application number: CN202310078839.6A
Authority: CN
Inventors: 贾传坤; 伏虎; 刘俊伟
Original assignee: Zhangjiagang Detai Energy Storage Equipment Co ltd
Current assignee: Zhangjiagang Detai Energy Storage Equipment Co ltd
Priority date: 2023-02-08
Filing date: 2023-02-08
Publication date: 2023-12-22

Abstract

The invention discloses a method for batched treatment of carbon-based electrodes for flow batteries, which comprises the following steps: pretreating a carbon felt; performing low-temperature oxidation in an atmosphere with the oxygen volume content of 5-30%; in an inert atmosphere, adjusting the oxygen content to be lower than 1200ppm, heating to 1000-1500 ℃ and performing high-temperature activation; regulating the oxygen content to be lower than 150ppm, heating to 2000-2250 ℃ and graphitizing; introducing an inert gas plasma source to etch the surface of the carbon fiber in the temperature range of 2000-2200 ℃; heating to 2250deg.C-2300 deg.C, maintaining for 1-5min, and naturally cooling to room temperature. The modified carbon-based electrode prepared by the invention has the advantages of high conductivity, good catalytic performance and good stability, and improves the cycle life, the power density and the energy conversion efficiency of the redox flow battery.

Description

Method for batch treatment of carbon-based electrode for flow battery

Technical Field

The invention belongs to the technical field of flow batteries, and relates to a method for batch treatment of carbon-based electrodes for flow batteries.

Background

Development of sustainable and renewable energy sources such as wind energy and solar energy is an effective way to solve the energy crisis. The intermittence and instability of renewable energy sources in the power output process must be effectively balanced by the capabilities of advanced energy storage systems to ensure a continuous or on-demand safe and reliable power supply. The power of redox flow batteries is determined by the size and number of cells, and the energy density is controlled by the concentration of active species, the number of electrons transferred by the redox reaction, and the voltage. The redox flow battery is one of the first choice of large-scale energy storage technology due to the advantages of energy and power separation, long cycle life, low cost, short maintenance time, high safety, environmental protection and the like. In order to encourage market adoption of redox flow battery technology, researchers are striving to improve their power density performance while maintaining high energy efficiency. Wherein the cost of the power module is mainly determined by the electrode material properties, in particular the conductivity and the catalytic properties. At present, no electrode material for a commercial redox flow battery exists, and an electrode mainly used for application is a carbon-based material used for heat preservation and heat insulation. The insufficient performance of the carbon-based material directly causes low power density and excessive high cost of the power module of the electric pile, and becomes a bottleneck to be broken through currently. As redox flow battery yields increase rapidly, there is a growing need for electrode materials. The most widely-used electrode preparation technology at present is to carry out modification treatment on carbon-based materials (carbon felt, graphite felt, carbon cloth and the like) so as to obtain the electrode with high conductivity and electrochemical activity, but the current electrode preparation technology is not mature, the preparation cost is high, and batch production and application are difficult to realize, so that no electrode for a commercial redox flow battery exists at present.

Up to now, there is no suitable method to solve the above-mentioned key problems, and development of a method capable of industrialized batch treatment of carbon-based electrodes, improving the conductivity and catalytic activity thereof is needed, which provides an important contribution to the large-scale development of redox flow batteries.

Disclosure of Invention

In order to solve the problems, the invention provides a method for batched treatment of carbon-based electrodes for flow batteries, and the prepared modified carbon-based electrodes have the advantages of high conductivity, good catalytic performance and good stability, so that the cycle life, power density and energy conversion efficiency of redox flow batteries are improved, and the problems in the prior art are solved.

The technical scheme adopted by the invention is that the method for batched treatment of the carbon-based electrode for the flow battery comprises the following steps:

s1, pretreating a carbon felt;

s2, heating to 100-400 ℃ under the atmosphere of 5-30% of oxygen volume content, heating up to 4-8 ℃/min, preserving heat for 20-120 min, and carrying out low-temperature oxidation;

s3, under an inert atmosphere, adjusting the oxygen content to be lower than 1200ppm (oxygen volume concentration), heating to 1000-1500 ℃, keeping the temperature for 30-300 min at a heating rate of 4-6 ℃/min, and performing high-temperature activation;

S4, adjusting the oxygen content to be lower than 150ppm, heating to 2000-2250 ℃, heating at a speed of 3-5 ℃/min, and preserving the temperature for 1-5min for graphitization;

s5, introducing an inert gas plasma source to etch the surface of the carbon fiber in a temperature range of 2000-2200 ℃, wherein the volume ratio of the plasma source to the ambient gas is 0.02-0.2, the plasma power is 100-1200W, and the etching time is 30-360S;

s6, heating to 2250-2300 ℃, preserving heat for 1-5min, and naturally cooling to room temperature to obtain the product.

Further, the graphitization degree of the carbon felt in the step S1 is below 30%, before the inert gas plasma source is introduced in the step S5, the carbon-containing gas plasma source is introduced to deposit the carbon fiber surface, the volume ratio of the carbon-containing gas plasma source to the environmental gas is 0.3-0.5, the plasma power is 1000-1200w, and the deposition time is 40-60min; wherein the etching time of the inert gas plasma source is 30-120s.

Further, in the step S1, the graphitization degree of the carbon felt is 30-60%, and before the step S2, etching the pretreated carbon felt in an alkali solution, cleaning to be neutral, and drying; before S5, introducing an inert gas plasma source, introducing a carbon-containing gas plasma source to deposit the surface of the carbon fiber, wherein the carbon-containing gas plasma source occupies 0.3-0.5 of the volume ratio of the environmental gas, the plasma power is 1000-1200w, and the deposition time is 40-60min; wherein the etching time of the inert gas plasma source is 120-240s.

Further, in the step S1, the graphitization degree of the carbon felt is more than 60%, and before the step S2, the pretreated carbon felt is soaked and oxidized in an acid solution, washed to be neutral and dried; wherein the etching time of the inert gas plasma source is 240-360s.

Further, the S1 specifically is:

s11, immersing the carbon felt in excessive deionized water for 30-60min, and taking out after full wetting;

s12, cutting the impregnated carbon felt into the size of an electrode, cleaning with ethanol solution for 10-15 times, and then soaking for ultrasonic treatment for 15-60min; cleaning impurities on the surface of the carbon fiber;

s13, placing the carbon felt after ultrasonic treatment in a blast drying oven, adjusting the temperature to 40-80 ℃ and drying for 4-12h.

Further, in the step S3, after the temperature is raised to 1200 ℃, the oxygen content is required to be lower than 540ppm.

Further, in S4, after the temperature reaches 2200 ℃, the oxygen content is required to be lower than 60ppm.

Further, the alkali solution is potassium hydroxide or sodium hydroxide solution, the concentration is 2-5mol/L, and the treatment time is 24-72h.

Further, the acid solution is sulfuric acid, hydrochloric acid or nitric acid solution, the concentration is 0.5-3mol/L, and the treatment time is 6-48h.

Further, the carbon-containing gas plasma source is an olefin gas, and the mass content of other elements except C, H, O is lower than 5%; the inert gas plasma source is helium, neon, argon, krypton or xenon.

The beneficial effects of the invention are as follows:

(1) According to the specific embodiment of the invention, aiming at carbon fibers with any graphitization degree, impurities can be washed away by adopting carbon felt cleaning, channels among the carbon fibers are expanded, and the contact area between the carbon fibers and electrolyte is increased; aiming at carbon fibers with graphitization degree higher than 60%, the carbon felt is soaked and oxidized to increase oxygen-containing functional groups on the surfaces of the carbon fibers, so that the hydrophilicity is improved; aiming at the carbon fiber with the graphitization degree of 30-60%, a large number of micropores and mesopores can be manufactured on the surface of the carbon fiber by soaking and etching of a carbon felt, so that more active sites are provided for oxidation-reduction reaction; these surface treatments facilitate subsequent regulation of the internal structure of the carbon felt.

(2) According to the carbon fiber with any graphitization degree in the specific embodiment of the invention, the amorphous carbon in the carbon fiber can be converted into a graphite structure by heat treatment of the carbon felt, and the order of the carbon structure is increased, so that the conductivity of the carbon fiber is improved; aiming at carbon fibers with graphitization degree higher than 60%, the folds and unstable carbon atoms at the edge of a graphite structure can be etched by etching with an inert gas plasma source, so that the stability of the performance of the carbon fibers is effectively improved; for carbon fibers with graphitization degree of 30-60%, firstly adopting an inert gas plasma source for etching and then matching with a carbon-containing gas plasma source for deposition to remove unstable carbon atoms, providing more carbon sources and increasing graphitization degree of the carbon fibers; for carbon fibers with graphitization degree of 0-30%, carbon-containing gas plasma source deposition is adopted first, and then inert gas plasma source etching is matched, so that more carbon sources can be provided, and graphitization degree of the carbon fibers is increased.

(3) According to the specific embodiment of the invention, the surface treatment and the structure regulation are carried out on the internal carbon fibers of the carbon-based materials with different graphitization degrees, so that the electrochemical performance of the carbon fibers can be obviously enhanced by the synergistic effect of the surface treatment and the structure regulation, and the application performance of the carbon-based materials in redox flow batteries is integrally improved; the processing method has the advantages of low cost of raw materials/equipment, simple and convenient process flow, easiness in mass expansion production, and the prepared sample has the advantages of high conductivity, large specific surface area, good catalytic performance and good stability, and is beneficial to large-scale production of commercial electrodes for flow batteries.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a process flow diagram of a batch process for carbon fibers with different graphitization degrees in an embodiment of the present invention.

FIG. 2 is a cyclic voltammogram of a sample and a raw sample in an acid vanadium redox flow battery system for a carbon fiber batch treatment of 0-30% graphitization degree in an embodiment of the present invention.

FIG. 3 is a cyclic voltammogram of a sample and a raw sample in an acid vanadium redox flow battery system for a carbon fiber batch treatment of 30-60% graphitization degree in an embodiment of the present invention.

Fig. 4 is a cyclic voltammogram of a sample after batch processing of carbon fibers for graphitization degrees of 60% or more and a raw sample in an acid vanadium redox flow battery system in an embodiment of the present invention.

Fig. 5 is a graph comparing energy efficiency in an acid vanadium redox flow battery system of samples after batch treatment of carbon fibers for 0-30% graphitization degree in an embodiment of the present invention and raw samples.

Fig. 6 is a graph comparing energy efficiency in an acid vanadium redox flow battery system for samples subjected to carbon fiber batch treatment for 30-60% graphitization degree and original samples in an embodiment of the present invention.

Fig. 7 is a graph comparing energy efficiency in an acid vanadium redox flow battery system of samples after carbon fiber batch treatment for graphitization degrees of 60% or more and original samples in an embodiment of the present invention.

FIG. 8 is an XRD spectrum of a sample and a raw sample after a batch treatment for carbon fibers of different graphitization degrees in an embodiment of the present invention.

Detailed Description

The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The design idea of the embodiment of the invention is as follows: as shown in fig. 1, the carbon-based electrode for the flow battery, which has high conductivity, good catalytic performance, large specific surface area and excellent stability, is obtained by carrying out surface treatment and structural optimization on carbon fibers by taking the low-cost carbon-based electrode as a raw material and through the synergistic effect of the carbon-based electrode and the carbon fibers.

In the case of example 1,

a method of mass processing carbon-based electrodes for flow batteries, comprising the steps of:

s1, immersing a carbon felt with the graphitization degree of less than 30% in excessive deionized water for 60min, and taking out after full wetting;

cutting the impregnated carbon felt into the size of an electrode, cleaning with ethanol solution for 15 times, and then soaking for 60min by ultrasonic treatment; cleaning impurities on the surface of the carbon fiber, and treating the surface of the carbon felt;

Placing the carbon felt after ultrasonic treatment in a blast drying oven, adjusting the temperature to 80 ℃, and drying for 12 hours;

s2, placing a sample in a heating cavity of a graphite furnace, closing a valve, regulating the volume content of oxygen to be 30% through a high-vacuum pump valve, regulating the heating rate of the graphite furnace to be 4 ℃/min, heating to 100 ℃, preserving heat for 120min, and performing low-temperature oxidation;

s3, after the heat preservation is finished, introducing inert gas (argon), regulating the temperature rising rate of the graphite furnace to be 4 ℃/min, regulating the oxygen content through a high vacuum pump valve, ensuring that the oxygen content is lower than 1200ppm (oxygen volume concentration) at 400 ℃, ensuring that the oxygen content is lower than 540ppm at 1200 ℃, heating to 1500 ℃, and preserving the heat for 250min, and performing high-temperature activation; the oxygen content is adjusted to prevent the carbon felt from being burnt;

s4, increasing the volume flow of inert gas, wherein the volume content of argon is more than 99.985%, the oxygen content is reduced to 150ppm, the heating rate of a graphite furnace is regulated to 3 ℃/min, the oxygen content is regulated by a high vacuum pump valve, the oxygen content is ensured to be lower than 150ppm at 2000 ℃ and lower than 60ppm at 2200 ℃, and the temperature is kept for 1min to graphitize;

s5, introducing a carbon-containing gas plasma source (methane) at 2200 ℃ to deposit the carbon fiber surface, wherein the volume ratio of the plasma source to the ambient gas is 0.3, the plasma power is 1200w, and the deposition time is 60min. Then introducing an inert gas (argon) plasma source to etch the surface of the carbon fiber, wherein the plasma source occupies 0.02 volume percent of the ambient gas, the plasma power is 100W, and the etching time is 60s;

S6, heating to 2250 ℃, preserving heat for 5min, ensuring sufficient completion of graphitization, and naturally cooling to room temperature after heat preservation is finished to obtain a sample 1.

The carbon-containing gas plasma source is olefin gas, and the purity requirement is higher than 95%; including but not limited to methane, ethane, propane, butane, neopentane, ethylene, propylene, butene, acetylene, propyne, butyne, higher purity natural gas, most preferably high purity methane, to ensure adequate cracking of the carbon. The inert gas plasma source is helium, neon, argon, krypton or xenon.

As shown in fig. 2 and 5, the peak current of sample 1-1 in the acid vanadium redox flow battery system is 300mA and 278mA measured at room temperature, the original carbon felt is only 169mA and 158mA, the potential difference of sample 1-1 is 0.53V, the original carbon felt is 0.83V, the energy efficiency of sample 1-1 is 85.10%, the original carbon felt is 56.44%, which indicates that the conductivity and catalytic activity of sample 1-1 are higher than those of the original carbon felt, and the application requirements of the redox flow battery are met.

In the case of example 2,

s1, immersing a carbon felt with the graphitization degree of less than 30% in excessive deionized water for 30min, and taking out after full wetting;

Cutting the impregnated carbon felt into the size of an electrode, cleaning with ethanol solution for 10 times, and then soaking for 15min by ultrasonic waves; cleaning impurities on the surface of the carbon fiber, and treating the surface of the carbon felt;

placing the carbon felt after ultrasonic treatment in a blast drying oven, adjusting the temperature to 40 ℃, and drying for 10 hours;

s2, placing a sample in a heating cavity of a graphite furnace, closing a valve, regulating the volume content of oxygen to be 5% through a high-vacuum pump valve, regulating the heating rate of the graphite furnace to be 8 ℃/min, heating to 400 ℃, preserving heat for 20min, and performing low-temperature oxidation;

s3, after the heat preservation is finished, introducing inert gas (nitrogen), regulating the temperature rising rate of the graphite furnace to be 6 ℃/min, regulating the oxygen content by a high vacuum pump valve, ensuring that the oxygen content is lower than 1200ppm at 400 ℃, ensuring that the oxygen content is lower than 540ppm at 1200 ℃, rising the temperature to 1300 ℃, and preserving the heat for 300min, and performing high-temperature activation;

s4, increasing the volume flow of inert gas, wherein the volume content of nitrogen is more than 99.985%, the oxygen content is reduced to 150ppm, the heating rate of the graphite furnace is regulated to 5 ℃/min, the oxygen content is regulated by a high vacuum pump valve, the oxygen content is ensured to be lower than 150ppm at 2000 ℃, and the temperature is kept for 5min for graphitization;

S5, introducing a carbon-containing gas plasma source (ethylene) at 2000 ℃ to deposit the carbon fiber surface, wherein the volume ratio of the plasma source to the ambient gas is 0.5, the plasma power is 1000w, and the deposition time is 50min. Then introducing an inert gas (helium) plasma source to etch the surface of the carbon fiber, wherein the volume ratio of the plasma source to the ambient gas is 0.2, the plasma power is 1200W, and the etching time is 30s;

and S6, heating to 2300 ℃, preserving heat for 1min to ensure that graphitization is fully completed, and naturally cooling to room temperature after heat preservation is finished to obtain a sample 1-2.

The peak current of the sample 1-2 in the acid vanadium redox flow battery system is 234mA and 213mA measured at room temperature, the original carbon felt is only 169mA and 158mA, the potential difference of the sample 1-2 is 0.75V, and the original carbon felt is 0.83V, which indicates that the conductivity and the catalytic activity of the sample 1-2 are higher than those of the original carbon felt, and the sample 1-2 is suitable for the application requirements of the redox flow battery.

In the case of example 3,

s1, immersing a carbon felt with the graphitization degree of less than 30% in excessive deionized water for 50min, and taking out after full wetting;

cutting the impregnated carbon felt into the size of an electrode, cleaning with ethanol solution for 12 times, and then soaking for ultrasonic treatment for 30min; cleaning impurities on the surface of the carbon fiber, and treating the surface of the carbon felt;

Placing the carbon felt after ultrasonic treatment in a blast drying oven, adjusting the temperature to 70 ℃, and drying for 4 hours;

s2, placing a sample in a heating cavity of a graphite furnace, closing a valve, regulating the volume content of oxygen to 20% by a high-vacuum pump valve, regulating the heating rate of the graphite furnace to 5 ℃/min, heating to 300 ℃, preserving heat for 600min, and performing low-temperature oxidation;

s3, after the heat preservation is finished, introducing inert gas (helium), regulating the temperature rising rate of the graphite furnace to be 5 ℃/min, regulating the oxygen content by a high vacuum pump valve, ensuring that the oxygen content is lower than 1200ppm at 400 ℃ and lower than 540ppm at 1000 ℃, rising the temperature to 1000 ℃, and preserving the heat for 30min, and performing high-temperature activation;

s4, increasing the volume flow of inert gas, wherein the volume content of helium is more than 99.985%, the oxygen content is reduced to 150ppm, the heating rate of the graphite furnace is regulated to 4 ℃/min, the oxygen content is regulated through a high vacuum pump valve, the oxygen content is ensured to be lower than 150ppm at 2250 ℃, and the temperature is kept for 3min for graphitization;

s5, firstly introducing a carbon-containing gas (propyne) plasma source at 2100 ℃ to deposit the surface of the carbon fiber, wherein the volume ratio of the plasma source to the ambient gas is 0.4, the plasma power is 1100w, and the deposition time is 40min. Then introducing an inert gas (helium) plasma source to etch the surface of the carbon fiber, wherein the volume ratio of the plasma source to the ambient gas is 0.1, the plasma power is 500W, and the etching time is 120s;

S6, heating to 2280 ℃, preserving heat for 3min to ensure that graphitization is fully completed, and naturally cooling to room temperature after heat preservation is finished to obtain the sample 1-3.

The volume content of oxygen for low-temperature oxidation is 5-30%, and under the condition of overhigh oxygen content, the carbon felt can be burnt due to overhigh temperature (higher than 400 ℃); below 100 ℃, the surface carbon fiber cannot generate oxidation, and a chemical bond which promotes the combination of carbon atoms and oxygen in the air to be stable is required to be high-temperature, so that oxygen-containing functional groups are formed on the surface.

The graphitization temperature range is 2000-2250 ℃, so that the cost is increased due to the fact that the temperature of the carbon fiber is sufficiently graphitized at too high temperature, and the carbon felt after graphitization has low toughness at high temperature and is easy to break in the industrial preparation process. Below 2000 c does not fully ensure that all structures have been graphitized.

The peak current of the sample 1-3 in the acid vanadium redox flow battery system is 268mA and 246mA, the original carbon felt is only 169mA and 158mA, the potential difference of the sample 1-3 is 0.68V, and the original carbon felt is 0.83V, which indicates that the conductivity and the catalytic activity of the sample 1-3 are higher than those of the original carbon felt, and the sample is suitable for the application requirement of the redox flow battery.

In the case of example 4,

a method for batch processing of carbon-based electrodes for flow batteries, except that the heat preservation time in S3 was 200min, was the same as in example 1, and samples 1 to 4 were produced.

The peak current of the samples 1-4 prepared in the embodiment in the acid vanadium redox flow battery system is 295mA and 272mA, the original carbon felt is only 169mA and 158mA, the potential difference of the samples 1-4 is 0.55V, and the original carbon felt is 0.83V, which indicates that the conductivity and the catalytic activity of the samples 1-4 are higher than those of the original carbon felt, and the samples are suitable for the application requirements of the redox flow battery.

In example 5 the process was carried out,

a method for batch processing of carbon-based electrodes for flow batteries, except that the heat preservation time in S3 was 300min, was the same as in example 1, and samples 1 to 5 were produced.

The peak current of the samples 1-5 prepared in the embodiment in the acid vanadium redox flow battery system is 294mA and 271mA, the original carbon felt is only 169mA and 158mA, the potential difference of the samples 1-5 is 0.54V, and the original carbon felt is 0.83V, which indicates that the conductivity and the catalytic activity of the samples 1-5 are higher than those of the original carbon felt, and the samples are suitable for the application requirements of the redox flow battery.

The graphitization degree of 0-30% is low, and the strength of the carbon fiber is damaged by directly adopting acid-base treatment, so that the carbon fiber is directly cleaned. The carbon fiber with 0-30% graphitization degree has more disordered structure due to less initial graphite structure. When graphitization is performed, insufficient carbon atom content may occur, so that insufficient graphitization is caused, and carbon-containing gas deposition is required to be performed first to improve an additional carbon source; the carbon defects generated at the edge of the graphite structure are then etched by using an inert gas plasma source (if the inert gas etching is directly performed, the initial disordered structure may be completely destroyed, so that the graphite interlayer is unstable, and a complete interlayer carbon structure is difficult to form in the subsequent graphitization interval).

The graphitization degree is low, and the temperature is kept for a long time at a low temperature under a high oxygen-containing environment, so that the oxidation purpose can be fully achieved, and the irreversible damage to the strength of the carbon fiber caused by burning the carbon material is avoided.

In example 6 the process was carried out,

s1, immersing a carbon felt with graphitization degree of 30-60% in excessive deionized water for 60min, and taking out after full wetting;

cutting the impregnated carbon felt into the size of an electrode, cleaning with ethanol solution for 15 times, and then soaking for 60min by ultrasonic treatment; cleaning impurities on the surface of the carbon fiber;

soaking the cleaned carbon felt in a potassium hydroxide solution with the concentration of 3mol/L for 24 hours, then taking out, cleaning to be neutral by adopting deionized water, placing the carbon felt in a blast drying oven, adjusting the temperature to 80 ℃, and drying for 12 hours for surface treatment of the carbon felt;

s2, placing a sample in a heating cavity of a graphite furnace, closing a valve, regulating the volume content of oxygen to 15% by a high-vacuum pump valve, regulating the heating rate of the graphite furnace to 5 ℃/min, heating to 200 ℃, preserving heat for 60min, and performing low-temperature oxidation;

s3, after the heat preservation is finished, introducing inert gas (neon), regulating the temperature rising rate of the graphite furnace to be 6 ℃/min, regulating the oxygen content by a high vacuum pump valve, ensuring that the oxygen content is lower than 1200ppm at 400 ℃, ensuring that the oxygen content is lower than 540ppm at 1200 ℃, rising the temperature to 1500 ℃, and preserving the heat for 180min, and performing high-temperature activation;

S4, increasing the volume flow of inert gas, wherein the volume content of neon is more than 99.985%, the oxygen content is reduced to 150ppm, the heating rate of the graphite furnace is regulated to 5 ℃/min, the oxygen content is regulated by a high vacuum pump valve, the oxygen content is ensured to be lower than 150ppm at 2000 ℃ and the oxygen content is ensured to be lower than 60ppm at 2200 ℃ for graphitization;

s5, introducing a carbon-containing gas (propane) plasma source at 2200 ℃ to deposit the carbon fiber surface, wherein the volume ratio of the plasma source to the ambient gas is 0.4, the plasma power is 1100w, and the deposition time is 50min. Then introducing an inert gas plasma source to etch the surface of the carbon fiber, wherein the plasma source occupies 0.02 volume percent of the ambient gas, the plasma power is 150W, and the etching time is 180s;

s6, heating to 2250 ℃, preserving heat for 3min to ensure that graphitization is fully completed, and naturally cooling to room temperature after heat preservation is finished to prepare a sample 2-1.

As shown in FIG. 3 and FIG. 6, the peak current of sample 2-1 prepared in this example in the acid vanadium redox flow battery system is 305mA and 282mA, the original carbon felt is 191mA and 170mA only, the potential difference of sample 2-1 is 0.52V, the original carbon felt is 0.77V, the energy efficiency of sample 2-1 is 85.22%, the original carbon felt is 69.65%, which indicates that the conductivity and catalytic activity of sample 2-1 are higher than those of the original carbon felt, and the method is suitable for the application requirements of redox flow batteries.

In example 7,

a method for batch treatment of carbon-based electrodes for flow batteries comprises the steps of removing 5mol/L sodium hydroxide from an alkaline washing solution in S1, and soaking for 36h; s3, the heat preservation time of high-temperature activation in the S3 is 120min; s5, etching time of the inert gas plasma source is 120S; the remainder of the procedure was the same as in example 6, to obtain sample 2-2.

The peak current of the sample 2-2 prepared by the embodiment in the acid vanadium redox flow battery system is 303mA and 280mA, the original carbon felt is only 191mA and 170mA, the potential difference of the sample 2-2 is 0.53V, and the original carbon felt is 0.77V, which indicates that the conductivity and the catalytic activity of the sample 2-2 are higher than those of the original carbon felt, and the sample 2-2 is suitable for the application requirements of the redox flow battery.

In the case of example 8,

a method for batch treatment of carbon-based electrodes for flow batteries comprises the steps of removing 2mol/L sodium hydroxide from an alkaline washing solution in S1, and soaking for 72h; s3, the heat preservation time of high-temperature activation in the S3 is 240min; s5, etching time of the inert gas plasma source is 240S; the remainder of the procedure was the same as in example 6, to obtain samples 2-3.

The peak current of the sample 2-3 prepared by the embodiment in the acid vanadium redox flow battery system is 300mA and 277mA, the original carbon felt is only 191mA and 170mA, the potential difference of the sample 2-3 is 0.55V, and the original carbon felt is 0.77V, which indicates that the conductivity and the catalytic activity of the sample 2-3 are higher than those of the original carbon felt, and the sample is suitable for the application requirement of the redox flow battery.

The carbon defect at the edge of the graphite structure is etched by inert gas, the etching time of an inert gas plasma source is 120-240s, and the graphite structure is damaged by too long time, so that more carbon atoms are needed for subsequent carbon deposition, and the cost is increased; therefore, the adjustment of etching time parameters is important for carbon fibers with different graphitization degrees.

The alkali solution is potassium hydroxide or sodium hydroxide solution, and unstable carbon atoms are etched, so that micropores and mesopores are manufactured on the surface of the carbon fiber, and the specific surface area is increased; the concentration of the alkali solution is 2-5mol/L, the treatment time is 24-72h, and if the concentration is too high or the treatment time is too long, irreversible damage is caused to the carbon structure; aiming at carbon fibers with different graphitization degrees, the balance of the two is important to adjust by adopting alkali solutions with different types and different concentrations.

The graphitization degree of 30-60% adopts alkali treatment to manufacture micropores and mesopores on the surface of the carbon fiber, and meanwhile, unstable carbon defects are etched away, so that beneficial conditions are provided for the re-etching of the carbon deposited in the later stage.

The initial graphite structure of the carbon fiber with the graphitization degree of 30-60% is moderate, which shows that the proportion of the graphite structure and the disordered carbon structure in the carbon fiber is close, so that the defects at the edge of the graphite structure can be etched by adopting an inert gas plasma source, and then, the graphitization degree is improved by adopting carbon-containing gas deposition to provide an additional carbon source.

In example 9 the process was carried out,

s1, immersing a carbon felt with the graphitization degree of more than 60% in excessive deionized water for 60min, and taking out after full wetting;

soaking the cleaned carbon felt in sulfuric acid solution with the concentration of 2mol/L for 6 hours, then taking out, cleaning to be neutral by adopting deionized water, placing the carbon felt in a blast drying oven, adjusting the temperature to 80 ℃, and drying for 12 hours for surface treatment of the carbon felt;

s2, placing a sample in a heating cavity of a graphite furnace, closing a valve, regulating the volume content of oxygen to be 5% through a high-vacuum pump valve, regulating the heating rate of the graphite furnace to be 8 ℃/min, heating to 300 ℃, preserving heat for 20min, and performing low-temperature oxidation;

s3, after heat preservation is finished, introducing inert gas (argon), regulating the temperature rising rate of the graphite furnace to be 6 ℃/min, regulating the oxygen content by a high vacuum pump valve, ensuring that the oxygen content is lower than 1200ppm at 400 ℃, ensuring that the oxygen content is lower than 540ppm at 1200 ℃, rising the temperature to 1500 ℃, and preserving the heat for 90min, and performing high-temperature activation;

S4, increasing the volume flow of the ambient gas, wherein the volume content of argon is more than 99.985%, the oxygen content is reduced to 150ppm, the heating rate of the graphite furnace is regulated to 5 ℃/min, the oxygen content is regulated by a high vacuum pump valve, the oxygen content is ensured to be lower than 150ppm at 2000 ℃ and lower than 60ppm at 2200 ℃, and graphitization is performed;

s5, introducing an inert gas plasma source at 2200 ℃ to etch the surface of the carbon fiber, wherein the volume ratio of the plasma source to the ambient gas is 0.2, the plasma power is 200W, and the etching time is 300S;

s6, heating to 2250 ℃, preserving heat for 5min, ensuring sufficient completion of graphitization, and naturally cooling to room temperature after heat preservation is finished, thus obtaining sample 3-1.

As shown in FIG. 4 and FIG. 7, the peak current of sample 3-1 prepared in this example in the acid vanadium redox flow battery system is 294mA and 271mA, the original carbon felt is only 212mA and 188mA, the potential difference of sample 3-1 is 0.52V, the original carbon felt is 0.68V, the energy efficiency of sample 3-1 is 86.05%, the original carbon felt is 72.86%, which indicates that the conductivity and catalytic activity of sample 3-1 are higher than those of the original carbon felt, and the application requirements of the redox flow battery are met.

In the case of example 11,

a method for batch treatment of carbon-based electrodes for flow batteries comprises the steps of removing 0.5mol/L hydrochloric acid from an acid washing solution in S1, and soaking for 48 hours; the low-temperature oxidation temperature in S2 is 200 ℃; s5, etching time of the inert gas plasma source is 240S; the remainder of the procedure was the same as in example 9 to obtain sample 3-2.

The peak current of the sample 3-2 prepared in the embodiment in the acid vanadium redox flow battery system is 292mA and 269mA measured at room temperature, the original carbon felt is only 212mA and 188mA, the potential difference of the sample 3-2 is 0.53V, and the original carbon felt is 0.68V, which indicates that the conductivity and the catalytic activity of the sample 3-2 are higher than those of the original carbon felt, and the sample is suitable for the application requirements of the redox flow battery.

In example 12 the process was carried out,

a method for batched treatment of carbon-based electrodes for flow batteries comprises the steps of removing 3mol/L nitric acid from an acid washing solution in S1, and soaking for 15 hours; the temperature of low-temperature oxidation in S2 is 400 ℃; s5, etching time of the inert gas plasma source is 360S; the remainder of the procedure was the same as in example 9, to obtain sample 3-3.

The peak current of the sample 3-3 prepared by the embodiment in the acid vanadium redox flow battery system is 291mA and 268mA, the original carbon felt is only 212mA and 188mA, the potential difference of the sample 3-3 is 0.54V, and the original carbon felt is 0.68V, which indicates that the conductivity and the catalytic activity of the sample 3-3 are higher than those of the original carbon felt, and the sample 3-3 is suitable for the application requirements of the redox flow battery.

In example 13 the process was carried out,

a method for batch treatment of carbon-based electrodes for flow batteries, except that the heat preservation time for high-temperature activation in S3 was 30min, the rest of the steps were the same as in example 9, to prepare samples 3-4.

The peak current of the sample 3-4 prepared by the embodiment in the acid vanadium redox flow battery system is 291mA and 270mA, the original carbon felt is only 212mA and 188mA, the potential difference of the sample 3-4 is 0.54V, and the original carbon felt is 0.68V, which indicates that the conductivity and the catalytic activity of the sample 3-4 are higher than those of the original carbon felt, and the sample is suitable for the application requirement of the redox flow battery.

In example 14 the process was carried out,

a method for batch treatment of carbon-based electrodes for flow batteries, except that the heat preservation time for high-temperature activation in S3 was 150min, the rest of the steps were the same as in example 9, to prepare samples 3-5.

The peak current of the sample 3-5 prepared by the embodiment in the acid vanadium redox flow battery system is 288mA and 265mA, the original carbon felt is only 212mA and 188mA, the potential difference of the sample 3-5 is 0.52V, and the original carbon felt is 0.68V, which indicates that the conductivity and the catalytic activity of the sample 3-5 are higher than those of the original carbon felt, and the sample 3-5 is suitable for the application requirement of the redox flow battery.

More than 60% of graphitization degree adopts acid treatment to graft more oxygen-containing functional groups (less than 60% of graphitization degree contains more oxygen-containing functional groups per se), and the grafted functional groups can break part of carbon-carbon double bonds, and carbon-oxygen single bonds can be broken in a subsequent carbonization zone to form a complete carbon structure.

The carbon fiber with the graphitization degree of more than 60% has more initial graphite structure, and the defects at the edge of the graphite structure are directly etched by adopting an inert gas plasma source. (if carbon deposition would result in too high a degree of graphitization, resulting in poor hydrophilicity, performance would be degraded in the flow battery field).

The graphitization degree is higher, and the heat preservation is needed to be carried out for a short time at a higher temperature under a low oxygen-containing environment.

The carbon fiber with low graphitization degree and high graphitization degree needs longer carbonization and graphitization heat preservation time and higher temperature, so that sufficient graphitization is realized and the ordered degree of the carbon structure is ensured.

In comparative example 1,

step 1, immersing a carbon felt with graphitization degree lower than 30% in excessive deionized water for 60min, and taking out after full wetting;

step 2, cutting the impregnated carbon felt into the size of an electrode, cleaning with ethanol solution for 15 times, and then soaking for 60 minutes by ultrasonic waves; cleaning impurities on the surface of the carbon fiber;

and 3, placing the carbon felt after ultrasonic treatment in a blast drying oven, adjusting the temperature to 80 ℃, and drying for 12 hours to obtain a sample A.

The peak current of the sample A prepared in the comparative example in the acid vanadium redox flow battery system is 195mA and 163mA, the potential difference is 0.74V, and the energy efficiency is 68.18% measured at room temperature, and is shown in FIG. 5.

Comparative example 2,

step 1, immersing a carbon felt with graphitization degree of 30-60% in excessive deionized water for 60min, and taking out after full wetting;

and 3, soaking the cleaned carbon felt in a potassium hydroxide solution with the concentration of 3mol/L for 6 hours, then taking out, cleaning to be neutral by adopting deionized water, placing the carbon felt in a blast drying oven, adjusting the temperature to 80 ℃, and drying for 12 hours to obtain a sample B.

The peak current of the sample B prepared in the comparative example in the acid vanadium redox flow battery system is 212mA and 192mA, the potential difference is 0.65V, and the energy efficiency is 79.82% measured at room temperature, as shown in FIG. 6.

Comparative example 3,

and 3, soaking the cleaned carbon felt in a sodium hydroxide solution with the concentration of 3mol/L for 6 hours, then taking out, cleaning to be neutral by adopting deionized water, placing the carbon felt in a blast drying oven, adjusting the temperature to 80 ℃, and drying for 12 hours to obtain a sample C.

The peak current of sample C prepared in this comparative example in the acid vanadium redox flow battery system was measured at room temperature to be 210mA and 191mA, the potential difference was 0.65V, and the energy efficiency was 78.21%, as shown in FIG. 6.

The etching degree of alkali is different, the alkalinity of potassium hydroxide is stronger (the activity of alkali metal is stronger), the etching capability is stronger, and the alkali etching mainly shows the unstable carbon atoms of etching, so that micropores and mesopores are manufactured on the surface of the carbon fiber, and the specific surface area is improved. Also, if the etching defects are too many, irreversible damage is caused to the carbon structure, so that for carbon fibers with different graphitization degrees, it is important to adjust the balance of the two alkali solutions with different types and different concentrations.

Comparative example 4,

Step 1, immersing a carbon felt with the graphitization degree of more than 60% in excessive deionized water for 60min, and taking out after full wetting;

and 3, soaking the cleaned carbon felt in 2mol/L sulfuric acid solution for 6 hours, taking out, cleaning to be neutral by adopting deionized water, placing the carbon felt in a blast drying oven, adjusting the temperature to 80 ℃, and drying for 12 hours to obtain a sample D.

The peak current of the sample D prepared in the comparative example in the acid vanadium redox flow battery system is 230mA and 217mA, the potential difference is 0.74V, and the energy efficiency is 82.02% measured at room temperature, and is shown in FIG. 7.

Comparative example 5,

Step 3, soaking the cleaned carbon felt in hydrochloric acid solution with the concentration of 2mol/L for 6 hours, then taking out, cleaning to be neutral by adopting deionized water, placing the carbon felt in a blast drying oven, adjusting the temperature to 80 ℃, and drying for 12 hours to obtain a sample E;

the peak current of the sample E prepared in the comparative example in the acid vanadium redox flow battery system is 228mA and 215mA, the potential difference is 0.75V, and the energy efficiency is 80.41% measured at room temperature, and is shown in FIG. 7.

Comparative example 6,

step 3, soaking the cleaned carbon felt in 2mol/L nitric acid solution for 6 hours, then taking out, cleaning to be neutral by adopting deionized water, placing the carbon felt in a blast drying oven, adjusting the temperature to 80 ℃, and drying for 12 hours to obtain a sample F;

the peak current of sample F prepared in this comparative example in the acid vanadium redox flow battery system was 226mA and 216mA, the potential difference was 0.74V, and the energy efficiency was 78.94% as shown in FIG. 7.

The types of the acids in the comparative examples 4, 5 and 6 are different, the oxidation degrees are different, the oxidation of the acids mainly grafts carbon-oxygen single bonds (plays a positive role in a certain range), but the oxidation degree is too low, a certain number of carbon-oxygen double bonds are connected, the negative effect is played, and part of performances are reduced; and too high an oxidation level can result in too many oxygen-containing functional groups on the surface and a significant decrease in conductivity.

Comparative example 7,

in the step 7, an inert gas plasma source is firstly introduced in the temperature range of 2000-2200 ℃ to etch the surface of the carbon fiber, the volume ratio of the plasma source to the ambient gas is 0.02-0.2, the plasma power is 100W, and the etching time is 60s. Then introducing a carbon-containing gas plasma source to deposit the surface of the carbon fiber, wherein the volume ratio of the plasma source to the ambient gas is 0.3-0.5, the plasma power is 1200w, and the deposition time is 60min; the rest of the procedure is the same as in example 1; sample G was prepared.

The peak current of the sample G prepared in the comparative example in the acid vanadium redox flow battery system is 238mA and 216mA, the potential difference is 0.63V, and the energy efficiency is 78.85% measured at room temperature, and is shown in FIG. 5.

In comparative example 8,

In the step 7, an inert gas plasma source is firstly introduced in the temperature range of 2000-2200 ℃ to etch the surface of the carbon fiber, the volume ratio of the plasma source to the ambient gas is 0.02-0.2, the plasma power is 150W, and the etching time is 180s. Then introducing a carbon-containing gas plasma source to deposit the surface of the carbon fiber, wherein the volume ratio of the plasma source to the ambient gas is 0.3-0.5, the plasma power is 1100w, and the deposition time is 50min; the rest of the procedure is the same as in example 6; sample H was prepared.

The peak current of sample H prepared in this comparative example in the acid vanadium redox flow battery system was 180mA and 179mA, the potential difference was 0.71V, and the energy efficiency was 73.30% as shown in FIG. 6.

Comparative example 9,

the graphitization degree of the carbon felt in the step S1 is less than 30%, etching treatment is carried out on the pretreated carbon felt in an alkali solution (3 mol/L potassium hydroxide) for 24 hours before the step S2, and the carbon felt is cleaned to be neutral and dried; the rest of the procedure is the same as in example 1; sample I was prepared.

The peak current of the sample I prepared in the comparative example in the acid vanadium redox flow battery system is measured at room temperature to be 18mA and 14mA, and the potential difference is 0.84V.

Comparative example 10,

the graphitization degree of the carbon felt in the step S1 is 30% -60%, before the step S2, the pretreated carbon felt is soaked and oxidized in an acid solution (2 mol/L sulfuric acid solution) for 6 hours, and is washed to be neutral and dried; the rest of the procedure is the same as in example 6; sample J was prepared.

The peak currents of the sample J prepared in the comparative example in the acid vanadium redox flow battery system are 183mA and 159mA, and the potential difference is 0.79V.

Comparative example 11,

the graphitization degree of the carbon felt in the step S1 is more than 60%, etching treatment is carried out on the pretreated carbon felt in an alkali solution (3 mol/L potassium hydroxide) for 24 hours before the step S2, and the carbon felt is cleaned to be neutral and dried; the rest of the procedure is the same as in example 9; sample K was prepared.

The peak current of sample K prepared in this comparative example in the acid vanadium redox flow battery system is 206mA and 186mA, and the potential difference is 0.73V.

Comparative example 12,

the graphitization degree of the carbon felt in the S1 step is more than 60 percent; in S5, at 2200 ℃, a carbon-containing gas plasma source (methane) is firstly introduced to deposit the surface of the carbon fiber, wherein the volume ratio of the plasma source to the ambient gas is 0.3, the plasma power is 1200w, and the deposition time is 60min. Then introducing an inert gas (argon) plasma source to etch the surface of the carbon fiber, wherein the volume ratio of the plasma source to the ambient gas is 0.2, the plasma power is 200W, and the etching time is 300s; the rest of the procedure is the same as in example 9; sample L was prepared.

The peak current of sample L prepared in this comparative example in the acid vanadium redox flow battery system is 120mA and 84mA, and the potential difference is 0.79V.

In the prior art, only the temperature and the heat preservation time are adopted to adjust the carbon structure of the carbon fiber, the order of the carbon structure is largely determined by the raw material of the carbon fiber (most of the raw materials in the market adopt polypropylene-based fiber or viscose-based fiber), which means that under the condition that the difference of the carbon structure of the raw material is large, large errors exist only by adjusting the performance of the carbon fiber by means of the temperature and the heat preservation time, and large-scale mass production of carbon fiber products with high performance requirements is difficult. According to the embodiment of the invention, acid-base treatment is adopted as pretreatment, a foundation is provided for subsequent carbonization and graphitization, the carbon fibers on the market are divided into three different types according to graphitization degree aiming at the required performance characteristics of electrode materials for the flow battery, different pretreatment modes are adopted for different types, the respective proper oxidation, carbonization and graphitization temperature intervals and heat preservation time are adjusted, and carbon deposition and etching are carried out on the carbon fiber surfaces aiming at specific structures of different raw materials and combined with the electrode performance requirements of the flow battery so as to achieve the proper graphitization degree.

According to the embodiment of the invention, the carbon-containing plasma source is used for depositing to supplement more carbon atoms by controlling the depositing time and the etching time, so that intrinsic carbon defects in the carbon fiber are supplemented, line defects are inevitably generated at the boundary of a graphite structure in the depositing process, and unstable defects can be etched by plasma etching.

In the embodiment, the power and the deposition time of the plasma source of the carbon-containing gas are key parameters, the out-of-range performance is reduced, the graphitization degree is too high, the hydrophilicity is poor, and the balance of the hydrophilicity and the conductivity cannot be ensured.

In the embodiment, the power of the inert gas plasma source, the etching time is a key parameter, the out-of-range performance is reduced, the defect degree is too high, the conductivity is poor, and the balance of hydrophilicity and conductivity cannot be ensured.

The carbon-based electrode raw material can directly use the pre-oxidized felt as a raw material except the carbon felt, the aim of the invention is to prepare the electrode material suitable for the flow battery, the final effect mainly depends on the technological process, and the original felt only needs to ensure good hydrophilic performance and density in a proper range. The pre-oxidized fiber felt is a raw material of the carbon felt, all carbon fibers are obtained by carbonizing or graphitizing pre-oxidized fiber, but the current commercial carbon felt and graphite felt treatment process in the market cannot completely meet the electrode material requirements of the flow battery, and the market of the electrode material special for the flow battery is blank.

In the embodiment of the invention, a plasma source is introduced to deposit and etch the surface of the carbon felt in the temperature range of 2200-2200 ℃, and the graphitization degree of the carbon felt can be obviously improved and the stable combination of carbon bonds is ensured only through one heating process, which is a further optimization and improvement on the combination of the two technologies. According to the embodiment of the invention, other elements are not introduced in the calcination, only the carbon structure in the carbon felt is changed, stable sp2 structure with good conductivity can be obtained by balancing deposition and etching, as shown in fig. 8, all samples diffract obvious (002) crystal face and (100) crystal face, and the sp2 structure of graphite corresponding to the (002) crystal face can be seen, the (002) crystal face is enhanced along with the increase of graphitization degree in the original samples, all the treated samples are obviously enhanced, the order degree of the carbon structure is improved in the treatment process, the graphitization degree of the samples is increased, the electrochemical performance of the carbon fiber is enhanced, the composite of doping or materials of other elements is not existed, the cost is low, the process flow is convenient, and the batch production is easy to realize. The improvement of different processes of the invention enables the carbon felt electrode sample to have different electrochemical performances, obviously improves the catalytic activity of the carbon felt surface on oxidation reduction, is widely applicable to a plurality of redox flow battery systems, and in the specific embodiment of the invention, only an all-vanadium redox flow battery is selected as an embodiment, and all other redox flow battery system electrodes prepared by adopting the method belong to the protection scope of the invention. By utilizing the synergistic effect of the preparation method, the surface treatment and the structural optimization of the carbon fibers in the original carbon felt are carried out, and the conductivity and the catalytic activity of the electrode are greatly improved. The method for batched treatment of the carbon-based electrode for the flow battery is simple and feasible in operation, environment-friendly, low in raw material cost and easy for large-scale industrial production, and can be widely applied to the commercialization field of various flow batteries.

The embodiment of the invention greatly improves the activation capability of carbon atoms in the fiber, improves the performance controllability, and facilitates the application of the electrode in different flow battery systems instead of a single system. The whole heating process does not need manual regulation and control, the cost increase caused by temperature increase is limited, but the requirement on the gas environment is higher, so the heating process is carried out in a large continuous graphite furnace meeting the safety standard, thereby avoiding the burning of carbon felt materials.

The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A method for batch processing carbon-based electrodes for flow batteries, comprising the steps of:

s1, pretreating a carbon felt;

s2, heating to 100-400 ℃ under the atmosphere with the oxygen volume content of 5-30%, heating up to 4-8 ℃/min, preserving heat for 20-120 min, and carrying out low-temperature oxidation;

S3, under an inert atmosphere, adjusting the oxygen content to be lower than 1200ppm, heating to 1000-1500 ℃, keeping the temperature for 30-300 min at a heating rate of 4-6 ℃/min, and performing high-temperature activation;

2. The method for batch processing carbon-based electrodes for flow batteries according to claim 1, wherein the graphitization degree of a carbon felt in the step S1 is below 30%, before introducing an inert gas plasma source in the step S5, introducing a carbon-containing gas plasma source to deposit the surface of carbon fibers, wherein the carbon-containing gas plasma source occupies 0.3-0.5 volume percent of the environmental gas, the plasma power is 1000-1200w, and the deposition time is 40-60min; wherein the etching time of the inert gas plasma source is 30-120s.

3. The method for batch processing of carbon-based electrodes for flow batteries according to claim 1, wherein the graphitization degree of the carbon felt in S1 is 30-60%, and before S2, the pretreated carbon felt is etched in an alkali solution, washed to be neutral, and dried; before S5, introducing an inert gas plasma source, introducing a carbon-containing gas plasma source to deposit the surface of the carbon fiber, wherein the carbon-containing gas plasma source occupies 0.3-0.5 of the volume ratio of the environmental gas, the plasma power is 1000-1200w, and the deposition time is 40-60min; wherein the etching time of the inert gas plasma source is 120-240s.

4. The method for batch processing of carbon-based electrodes for flow batteries according to claim 1, wherein the graphitization degree of the carbon felt in S1 is 60% or more, and before S2, the pretreated carbon felt is immersed in an acid solution for oxidation, washed to neutrality and dried; wherein the etching time of the inert gas plasma source is 240-360s.

5. The method for mass processing of carbon-based electrodes for flow batteries according to claim 1, wherein S1 is specifically:

6. The method for mass-treating carbon-based electrodes for flow batteries according to claim 1, wherein in S3, the oxygen content is lower than 540ppm after the temperature reaches 1200 ℃.

7. The method for mass-treating carbon-based electrodes for flow batteries according to claim 1, wherein in S4, the oxygen content is less than 60ppm after the temperature reaches 2200 ℃.

8. The method for batch processing of carbon-based electrodes for flow batteries according to claim 3, wherein the alkaline solution is potassium hydroxide or sodium hydroxide solution, the concentration is 2-5mol/L, and the processing time is 24-72h.

9. The method for batch processing of carbon-based electrodes for flow batteries according to claim 4, wherein the acid solution is sulfuric acid, hydrochloric acid or nitric acid solution, the concentration is 0.5-3mol/L, and the processing time is 6-48h.

10. The method for mass-treating carbon-based electrodes for flow batteries according to claim 2, wherein the carbon-containing gas plasma source is an olefin gas, and the mass content of other elements except C, H, O is less than 5%; the inert gas plasma source is helium, neon, argon, krypton or xenon.