A method, system, and electrode for the preparation of modified carbon felt electrodes for flow batteries

Abstract

This invention relates to the field of battery electrode fabrication technology, and more particularly to a method, system, and electrode for preparing a modified carbon felt electrode for flow batteries. The method includes cleaning and drying a carbon felt to obtain a carbon felt matrix; impregnating the carbon felt matrix with a 0.5 mol / L ferric nitrate nonahydrate solution and then drying it to complete the pretreatment of the carbon felt matrix; placing the pretreated carbon felt matrix in a CVD furnace, purging the air with argon gas, and then heating it to the reaction temperature at a rate of 20°C / min while maintaining a constant argon flow rate; determining the initial concentration of ethanol vapor based on the change in conductivity of the carbon felt matrix within a preset time after pretreatment; continuing to supply ethanol vapor until the reaction is complete; then turning off the ethanol vapor and allowing it to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The modified carbon felt electrode prepared by this invention improves the battery energy efficiency at medium and low current densities by generating carbon nanofibers on its surface.

Description

Technical Field

[0001] This invention relates to the field of battery electrode preparation technology, and in particular to a method, system and electrode for preparing a modified carbon felt electrode for a flow battery. Background Technology

[0002] In vanadium redox flow battery stacks, the electrodes, serving as the sites of vanadium ion redox reactions, are typically made of porous carbon materials, primarily graphite felt or carbon felt. These materials possess good electrical conductivity, acid corrosion resistance, and chemical stability, and are relatively inexpensive.

[0003] Existing technologies include introducing oxygen-containing functional groups through acid oxidation or air / ammonia heat treatment to improve hydrophilicity and activity. However, these treatments are harsh, easily causing a decrease in the mechanical strength of the carbon felt and fiber breakage. The functional groups are also prone to detachment during long-term cycling, leading to performance degradation; it is difficult to significantly improve performance at high current densities. Other methods involve loading metals or their oxides to enhance reactivity, but precious metals are expensive and not suitable for large-scale applications, while non-precious metal oxides have poor stability, easily dissolving or deactivating in strongly acidic electrolytes. The loading process is complex, and uniformity is difficult to control. Other methods introduce CNTs, GO, etc., through coating, electrodeposition, or bonding, but the composite layer has weak adhesion to the carbon felt matrix, easily peeling off during cycling. The preparation process is complex and costly, and some methods require binders, further increasing internal resistance.

[0004] While existing modification techniques can improve electrode performance to some extent, they generally suffer from problems such as complex processes, high costs, insufficient stability, or limited improvement. They are difficult to achieve the requirements of high activity, high stability, low cost, and easy scalability at the same time, and there is still a need to develop new, more efficient, and simpler electrode modification methods. Summary of the Invention

[0005] Therefore, the present invention provides a method, system and electrode for preparing modified carbon felt electrode for flow batteries, which improves the chemical inertness of the carbon felt electrode itself and enhances its electrochemical performance and battery performance.

[0006] To achieve the above objectives, in one aspect, the present invention provides a method for preparing a modified carbon felt electrode for a flow battery, comprising: The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was pretreated by impregnating it with a 0.5 mol / L ferric nitrate nonahydrate solution and then drying it. The pretreated carbon felt matrix was placed in a CVD furnace. Argon gas was introduced to purge the air, and the temperature was increased to the reaction temperature at a rate of 20℃ / min. The argon gas flow rate was kept constant. Ethanol vapor was turned on until the reaction was completed. The ethanol vapor was then turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.1 mol / L to 0.25 mol / L, the flow rate of the argon gas is 80 sccm to 140 sccm, the reaction temperature is 600℃ to 750℃, and the on-time of the ethanol vapor is 30 min to 60 min.

[0007] Furthermore, the concentration of the ferric nitrate nonahydrate solution is 0.5 mol / L, and the immersion time is 60 min.

[0008] Furthermore, the modified carbon felt is ultrasonically cleaned in 3 mol / L hydrochloric acid for 30 min, rinsed with deionized water, and then dried at 80°C.

[0009] Furthermore, it also includes: When it is determined that the preparation of the modified carbon felt does not meet the preset standard based on the result that the first energy density characteristic value of the modified carbon felt is less than the first preset characteristic threshold, the initial inlet concentration is increased, and the adjustment of the initial inlet concentration is checked according to the second energy density characteristic value to see if it meets the preset standard. The first energy density characteristic value is the difference between the energy density of the modified carbon felt at the first current density and the energy density of the carbon felt matrix; the second energy density characteristic value is the difference between the energy density of the modified carbon felt at the second current density and the energy density of the carbon felt matrix. The first current density is 160 mA / cm2, and the second current density is 400 mA / cm2.

[0010] Furthermore, the increase in the initial inlet concentration is positively correlated with the concentration adjustment difference; the concentration adjustment difference is the difference between the first preset feature threshold and the first energy density feature value.

[0011] Furthermore, the adjustment of the initial inlet concentration is checked against a preset standard based on the second energy density characteristic value. Specifically, if the adjustment of the initial inlet concentration does not meet the preset standard when the second energy density characteristic value is less than the second preset characteristic threshold, the initial inlet concentration is corrected. If the adjustment of the initial inlet concentration meets the preset standard when the second energy density characteristic value is greater than or equal to the second preset characteristic threshold and less than the third preset characteristic threshold, the on-time of the ethanol vapor is increased.

[0012] Furthermore, the correction magnitude of the initial inlet concentration is positively correlated with the difference between the second preset characteristic threshold and the second energy density characteristic value, and the increase magnitude of the ethanol vapor on-time is positively correlated with the difference between the third preset characteristic threshold and the second energy density characteristic value.

[0013] On the other hand, the present invention provides a flow battery modified carbon felt electrode preparation system, comprising: a CVD furnace; The parameter acquisition module is used to obtain the first and second energy density characteristic values ​​of the modified carbon felt. The parameter determination module is connected to the parameter acquisition module and the CVD furnace respectively. It is used to determine whether the preparation of the modified carbon felt meets the preset standard based on the first energy density characteristic value of the modified carbon felt, and to verify whether the adjustment of the initial inlet concentration meets the preset standard based on the second energy density characteristic value.

[0014] On the other hand, the present invention also provides an electrode in which the length of the modified carbon felt is greater than 90% of the length of the modified nanofibers.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: By designing the growth of carbon nanofibers on the surface of the carbon felt, this invention effectively increases the specific surface area of ​​the carbon felt electrode, and the defect sites of the carbon nanofibers also provide more active sites for the electrode. This improves the electrochemical inertness of the original electrode and reduces its internal resistance. Traditional batteries typically have an energy efficiency of only 70%-80%, while the modified electrode of this invention improves battery energy efficiency by 5-10% at low to medium current densities. The original carbon felt cannot function properly at high current densities, but the modified electrode allows the battery energy efficiency to remain above 70%, significantly improving the battery rate performance. Simultaneously, the modified electrode shows improved energy density and energy efficiency at low current densities, and significant performance improvements at medium to high current densities.

[0016] Furthermore, this invention uses only two raw materials, ethanol and ferric nitrate nonahydrate, and completes electrode preparation by high-temperature heating in a conventional tube furnace. The process is simple, safe, environmentally friendly, and low-cost, making it suitable for large-scale industrial production.

[0017] Furthermore, this invention also sets a first energy density characteristic value and a second energy density characteristic value to characterize the electrical properties of the modified carbon felt, thereby accurately determining the preparation performance of the modified carbon felt. In turn, the corresponding process range is determined through a self-learning optimization method, which solves the problem of substandard product performance caused by parameter deviation or deviation of carbon felt raw materials, thus improving the stability of product preparation. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the method for preparing a modified carbon felt electrode for a flow battery according to an embodiment of the present invention. Figure 2A This is a scanning electron microscope image of the carbon felt substrate according to an embodiment of the present invention; Figure 2B This is a magnified scanning electron microscope image of the carbon felt substrate according to an embodiment of the present invention; Figure 3A This is a scanning electron microscope image of the modified carbon felt in Example 1 of the present invention; Figure 3B This is a magnified scanning electron microscope image of the modified carbon felt in Example 1 of the present invention; Figure 4 This is a scanning electron microscope image of the modified carbon felt in Example 4 of the present invention. Detailed Implementation

[0019] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0021] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0022] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Figure 1 The flowchart below shows the preparation method of the present invention. In a first aspect, an embodiment of the present invention provides a method for preparing a modified carbon felt electrode for a flow battery, characterized in that it includes: Step S1: The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80℃ to obtain the carbon felt matrix; the carbon felt matrix is ​​shown in a scanning electron microscope image as follows. Figure 2A and Figure 2B As shown; Step S2: The carbon felt matrix is ​​impregnated with a 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix; Step S3: Place the pretreated carbon felt matrix in a CVD furnace, introduce argon gas to purge the air, and heat it to the reaction temperature at a rate of 20℃ / min. Keep the argon gas flow rate constant, turn on ethanol vapor until the reaction is complete, turn off the ethanol vapor, and continue to cool naturally to room temperature under argon protection to obtain modified carbon felt. The concentration of the ethanol vapor is 0.1 mol / L to 0.25 mol / L, the flow rate of the argon gas is 80 sccm to 140 sccm, the reaction temperature is 600℃ to 750℃, and the on-time of the ethanol vapor is 30 min to 60 min.

[0024] Specifically, argon is used as an inert protective gas to purge the air from the furnace, prevent the carbon felt matrix from being oxidized and ablated at high temperatures, and provide an oxygen-free environment for subsequent reactions.

[0025] During the heating process, the supported ferric nitrate nonahydrate first dehydrates and then decomposes above 200°C, generating Fe2O3 nanoparticles. When the temperature continues to rise to the reaction temperature of 650-750°C, the Fe2O3 particles are reduced by ethanol cracking products under an argon atmosphere, forming catalytically active iron or iron carbide nanoparticles. Subsequently, ethanol vapor is introduced into the high-temperature reaction zone as a carbon source. On the surface of the catalytically active iron-based nanoparticles, ethanol molecules undergo catalytic cracking, producing acetylene, hydrogen, and a small amount of CO. The carbon atoms produced by cracking dissolve into the interior of the catalyst particles. When a supersaturated state is reached, the carbon atoms precipitate and form carbon nanofibers.

[0026] Specifically, the concentration of the ferric nitrate nonahydrate solution is 0.5 mol / L, and the impregnation time is 60 min. It is understood that ferric nitrate nonahydrate is highly soluble in water, and this high solubility ensures the preparation of a precursor solution with a precise and uniform concentration. During the impregnation of the carbon felt, iron ions can fully penetrate into the three-dimensional porous structure of the carbon felt and be uniformly adsorbed on the carbon fiber surface. This avoids solution inhomogeneity or particle agglomeration caused by low solubility, laying the foundation for the subsequent growth of a uniform nano-modified layer.

[0027] Specifically, the process includes ultrasonically cleaning the prepared modified carbon felt in 3 mol / L hydrochloric acid for 30 min, rinsing with deionized water, and then drying at 80°C. It is understood that during CVD growth, iron-based catalyst particles used to catalyze the growth of nanostructures often remain at the top or bottom of the carbon nanostructure. These residual metal particles may dissolve in the strongly acidic electrolyte environment of a flow battery, releasing iron ions, contaminating the electrolyte, and potentially triggering side reactions, affecting the long-term stability of the battery. Hydrochloric acid, as a strong acid, can chemically react with iron and its oxides to generate soluble ferric chloride, thereby dissolving and removing them.

[0028] Specifically, it also includes: step S4, when it is determined that the preparation of the modified carbon felt does not meet the preset standard based on the result that the first energy density characteristic value of the modified carbon felt is less than the first preset characteristic threshold, the initial inlet concentration is increased; Step S5: Verify whether the adjustment of the initial inlet concentration meets the preset standard based on the second energy density characteristic value; The first energy density characteristic value is the difference between the energy density of the modified carbon felt at the first current density and the energy density of the carbon felt matrix; the second energy density characteristic value is the difference between the energy density of the modified carbon felt at the second current density and the energy density of the carbon felt matrix. The first current density is 160 mA / cm², and the second current density is 400 mA / cm². The first preset characteristic threshold is 1.50 Wh / L. It can be understood that the first energy density characteristic value is the difference between the energy density of the modified carbon felt and the carbon felt matrix at the first current density, the conventional operating current density of the flow battery. This difference directly reflects the effect of CVD modification on the energy density improvement of the carbon nanofiber on the carbon felt electrode. The larger the difference, the better the modification effect and the more suitable the growth state of the carbon nanofiber is; the smaller the difference, the insufficient modification and the failure of the carbon nanofiber growth or activity to meet expectations. When the first energy density characteristic value is less than the first preset characteristic threshold, it indicates that the initial concentration of ethanol vapor is insufficient, resulting in insufficient carbon source supply, insufficient carbon nanofiber growth, poor dispersion, and an inability to effectively improve the specific surface area and catalytic activity of the electrode, thus causing the energy density improvement effect of the modified carbon felt to fail to meet the standard. Increasing the initial concentration of ethanol vapor at this point increases the carbon source content in the CVD reaction zone, providing sufficient raw materials for the growth of carbon nanofibers. This promotes the growth of more carbon nanofibers on the surface and within the pores of the carbon felt, thereby improving the energy density of the modified carbon felt and bringing it to the preset standard. The second energy density characteristic value is the difference between the energy density of the modified carbon felt and the carbon felt matrix under high-load operating current density in the flow battery. Compared to the first current density, high current density places higher demands on the electrode's mass transfer efficiency, catalytic activity, and structural stability. If the standard is only met under conventional current density, the energy density may drop sharply under high-load conditions due to insufficient carbon nanofiber growth or an unreasonable structure, failing to meet the long-term stable operation requirements of the battery. Therefore, verifying the second energy density characteristic value ensures that the modified carbon felt maintains stable performance under different operating loads, improving the electrode's applicability. The parameter adjustment mechanism is designed through a closed-loop control of performance feedback and precise adjustment, solving the problems of traditional fixed-parameter preparation of modified carbon felt, such as inability to adapt to different operating conditions, poor performance stability, and low preparation yield.

[0029] Specifically, the increase in the initial inlet concentration is positively correlated with the concentration adjustment difference; the concentration adjustment difference is the difference between the first preset feature threshold and the first energy density feature value. It can be understood that the positive correlation is either linear or nonlinear, and there is no specific limitation. It is only necessary to satisfy that the larger the concentration adjustment difference is, the larger the increase in the initial inlet concentration is.

[0030] Specifically, the adjustment of the initial inlet concentration is checked against a preset standard based on a second energy density characteristic value. Specifically, if the second energy density characteristic value is less than a second preset characteristic threshold, indicating that the adjustment of the initial inlet concentration does not meet the preset standard, the initial inlet concentration is corrected. Conversely, if the second energy density characteristic value is greater than or equal to a second preset characteristic threshold and less than a third preset characteristic threshold, indicating that the adjustment of the initial inlet concentration meets the preset standard, the on-time of the ethanol vapor is increased. The second preset characteristic threshold is 0.20 Wh / L, and the third preset characteristic threshold is 0.55 Wh / L. Specifically, the correction magnitude of the initial inlet concentration is positively correlated with the difference between the second preset characteristic threshold and the second energy density characteristic value. The correction of the initial inlet concentration is to reduce the adjusted initial inlet concentration, and the reduction magnitude is 5%-10% of the increase magnitude of the initial inlet concentration.

[0031] Furthermore, the increase in the on-time of the ethanol vapor is positively correlated with the difference between the third preset characteristic threshold and the second energy density characteristic value. It can be understood that as long as the difference between the third preset characteristic threshold and the second energy density characteristic value is larger, the increase in the on-time of the ethanol vapor will be larger.

[0032] In a second aspect, an embodiment of the present invention provides a system for preparing a modified carbon felt electrode for a flow battery, comprising: a CVD furnace; The parameter acquisition module is used to obtain the first and second energy density characteristic values ​​of the modified carbon felt. The parameter determination module is connected to the parameter acquisition module and the CVD furnace respectively. It is used to determine whether the preparation of the modified carbon felt meets the preset standard based on the first energy density characteristic value of the modified carbon felt, and to verify whether the adjustment of the initial inlet concentration meets the preset standard based on the second energy density characteristic value.

[0033] Specifically, the parameter acquisition module and the parameter determination module can be two chips equipped with programs, without any specific limitation. The parameter acquisition module is used to input the first energy density characteristic value and the second energy density characteristic value, and the parameter determination module is used to output the corresponding result according to the input parameters.

[0034] Thirdly, the electrode prepared by the method of the present invention has a length ratio of more than 90% for the modified carbon felt of the electrode. The length ratio is calculated by processing the data of electron microscope images and statistically analyzing the ratio of the total length of modified fibers with a diameter of less than 100 nanometers to the total length of all modified fibers in the electron microscope image. It can be understood that the diameter of the modified nanofibers is less than 100 nanometers.

[0035] Example 1 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 40 min.

[0036] Example 2 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.10 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 40 min.

[0037] Example 3 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.20 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 40 min.

[0038] Example 4 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.25 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 40 min.

[0039] Example 5 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 80 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 40 min.

[0040] Example 6 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 120 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 40 min.

[0041] Example 7 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 140 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 40 min.

[0042] Example 8 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 600℃, and the on-time of the ethanol vapor is 40 min.

[0043] Example 9 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 650℃, and the on-time of the ethanol vapor is 40 min.

[0044] Example 10 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 750℃, and the on-time of the ethanol vapor is 40 min.

[0045] Example 11 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 30 min.

[0046] Example 12 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 50 min.

[0047] Example 13 The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was impregnated with 0.5 mol / L ferric nitrate nonahydrate solution and then dried to complete the pretreatment of the carbon felt matrix. The pretreated carbon felt matrix was placed in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 60 min.

[0048] Comparative Example 1: Untreated carbon felt material.

[0049] Comparative Example 2: The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was placed directly in a CVD furnace, and after purging the air by introducing argon gas, the temperature was increased to the reaction temperature at a rate of 20°C / min. The argon gas flow rate was kept constant, and ethanol vapor was turned on until the reaction was completed. Then, the ethanol vapor was turned off and the carbon felt was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.15 mol / L, the flow rate of the argon gas is 100 sccm, the reaction temperature is 700℃, and the on-time of the ethanol vapor is 40 min.

[0050] The test used the electrode materials prepared in the examples and comparative examples as positive and negative electrodes, Nafion 117 as the separator, and an all-vanadium redox flow battery assembled with 1.6 mol / L vanadium oxysulfate and 4 mol / L sulfuric acid as the electrolyte, achieving a current of 160 mA / cm². 2 The battery was charged and discharged at current density, and the test data are shown in Table 1.

[0051] Table 1: Test results for each embodiment and comparative example.

[0052]

[0053] A comparison of Examples 1-13 with Comparative Examples 1-2 reveals that the energy efficiency and cycle performance of the carbon felt material significantly improve after modification. This demonstrates that the method of the present invention, by generating elemental iron within the three-dimensional structure of the carbon felt material and subsequently growing carbon nanofibers that provide redox sites for vanadium ions, facilitates the transfer of active materials and improves battery cycle performance. Figure 3A and Figure 3BThe scanning electron microscope image shows the diameter of the nano-modified fibers, and the preparation method of this application yields nanoscale modified fibers.

[0054] A comparison of Examples 1 and 2-4 reveals that the concentrations of ethanol vapor differ between Examples 1 and 2-4. Example 1 exhibits better energy efficiency and cycle performance than Example 2 because the carbon source provided by the carbon felt material in Example 2 is less, resulting in a lower density of deposited modified fibers, which in turn slightly reduces the battery's energy efficiency and cycle performance. However, the excessively high carbon source concentrations in Examples 3 and 4 lead to coarser modified fiber diameters, exceeding the nanometer scale, which in turn decreases energy efficiency and cycle performance. Figure 4 As shown.

[0055] Comparing Examples 1 and 5-7, it was found that the protective gas concentrations of Examples 1 and 5-7 were different, but the energy efficiency and cycle performance of Examples 1 and 5-7 were relatively similar. Therefore, it can be inferred that the protective gas concentration has little effect on the growth of modified fibers, and carbon nanofibers can be obtained within the range of 80 sccm-140 sccm for the protective gas argon.

[0056] A comparison of Example 1 with Examples 8-10 revealed that the reaction temperatures of Example 1 and Examples 8-10 were different. Within the reaction temperature range of 600℃-750℃, the energy efficiency and cycle performance first increased and then decreased. At lower temperatures, the density of the deposited modified fibers was lower, while at higher temperatures, the deposition rate was faster, resulting in larger diameter modified fibers. The optimal reaction temperature was 650℃.

[0057] Comparing Example 1 with Examples 11-13, it was found that the ethanol vapor on-time of Example 1 and Examples 11-13 were different, that is, the growth time was different. The internal energy efficiency and cycle performance also showed a trend of first increasing and then decreasing with the change of growth time. The optimal growth time was 40 min, which was between 30 min and 60 min.

[0058] Comparative Example 2 is a process without impregnation with ferric nitrate solution nonahydrate. Compared with the carbon felt material without any treatment, its performance is not improved, that is, no modified fibers are grown.

[0059] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a modified carbon felt electrode for a flow battery, the method comprising: providing a carbon felt; providing a solution comprising a polymer; and contacting the carbon felt with the solution to form a modified carbon felt electrode. include: The carbon felt was ultrasonically cleaned in anhydrous ethanol for 30 min, rinsed with deionized water, and dried at 80°C to obtain the carbon felt matrix. The carbon felt matrix was pretreated by impregnating it with a 0.5 mol / L ferric nitrate nonahydrate solution and then drying it. The pretreated carbon felt matrix was placed in a CVD furnace. Argon gas was introduced to purge the air, and the temperature was increased to the reaction temperature at a rate of 20℃ / min. The argon gas flow rate was kept constant. Ethanol vapor was turned on until the reaction was completed. The ethanol vapor was then turned off and the matrix was allowed to cool naturally to room temperature under argon protection to obtain the modified carbon felt. The concentration of the ethanol vapor is 0.1 mol / L to 0.25 mol / L, the flow rate of the argon gas is 80 sccm to 140 sccm, the reaction temperature is 600℃ to 750℃, and the on-time of the ethanol vapor is 30 min to 60 min.

2. The method of claim 1, wherein the method further comprises: The concentration of the ferric nitrate nonahydrate solution is 0.5 mol / L, and the immersion time is 60 min.

3. The method for preparing a modified carbon felt electrode for a flow battery according to claim 2, characterized in that, It also includes ultrasonically cleaning the prepared modified carbon felt in 3 mol / L hydrochloric acid for 30 min, rinsing it with deionized water, and then drying it at 80°C.

4. The method for preparing a modified carbon felt electrode for a flow battery according to claim 1, characterized in that, Also includes: When it is determined that the preparation of the modified carbon felt does not meet the preset standard based on the result that the first energy density characteristic value of the modified carbon felt is less than the first preset characteristic threshold, the initial inlet concentration is increased, and the adjustment of the initial inlet concentration is checked according to the second energy density characteristic value to see if it meets the preset standard. The first energy density characteristic value is the difference between the energy density of the modified carbon felt at the first current density and the energy density of the carbon felt matrix; the second energy density characteristic value is the difference between the energy density of the modified carbon felt at the second current density and the energy density of the carbon felt matrix. wherein the first current density is 160 mA / cm 2 and the second current density is 400 mA / cm 2 .

5. The method for preparing a modified carbon felt electrode for a flow battery according to claim 4, characterized in that, The increase in the initial inlet concentration is positively correlated with the concentration adjustment difference; the concentration adjustment difference is the difference between the first preset feature threshold and the first energy density feature value.

6. The method for preparing a modified carbon felt electrode for a flow battery according to claim 5, characterized in that, The initial inlet concentration adjustment is checked against a preset standard based on the second energy density characteristic value. Specifically, if the second energy density characteristic value is less than the second preset characteristic threshold, the initial inlet concentration adjustment is checked against the preset standard and the initial inlet concentration is corrected. If the second energy density characteristic value is greater than or equal to the second preset characteristic threshold and less than the third preset characteristic threshold, the initial inlet concentration adjustment is checked against the preset standard and the on-time of ethanol vapor is increased.

7. The method for preparing a modified carbon felt electrode for a flow battery according to claim 6, characterized in that, The correction magnitude of the initial inlet concentration is positively correlated with the difference between the second preset characteristic threshold and the second energy density characteristic value, and the increase magnitude of the ethanol vapor on-time is positively correlated with the difference between the third preset characteristic threshold and the second energy density characteristic value.

8. A system for use in the preparation method according to any one of claims 1-7, characterized in that, include: CVD furnace; The parameter acquisition module is used to obtain the first and second energy density characteristic values ​​of the modified carbon felt. The parameter determination module is connected to the parameter acquisition module and the CVD furnace respectively. It is used to determine whether the preparation of the modified carbon felt meets the preset standard based on the first energy density characteristic value of the modified carbon felt, and to verify whether the adjustment of the initial inlet concentration meets the preset standard based on the second energy density characteristic value.

9. An electrode prepared by the method according to any one of claims 1-7, characterized in that: The length of the modified carbon felt is greater than 90% of the length of the nano-modified fibers.

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