Methods for recycling and regenerating waste electrode materials from vanadium redox flow batteries

Abstract

This invention belongs to the field of vanadium battery production technology and discloses a method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. Through steps (1) pretreatment, (2) carboxylation modification of the waste electrode, (3) in-situ growth of carbon nanotubes, (4) surface amination treatment, and (5) grafting and activating carbon nanotubes, a regenerated electrode is obtained. This invention enables waste electrodes to achieve battery performance comparable to or even higher than the initial electrodes, allowing them to be reused as electrodes in vanadium redox flow batteries, thus reducing the cost of electrode materials for vanadium redox flow batteries.

Description

Technical Field

[0001] This invention relates to the field of vanadium battery production technology, and more specifically to a method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. Background Technology

[0002] Vanadium redox batteries, as a highly efficient, clean, and high-capacity energy source, possess advantages such as high charge-discharge efficiency and high power density, and have attracted much attention from scholars. They are expected to serve as a crucial support for future energy sector reforms. However, after long-term operation, the voltage efficiency of vanadium redox flow batteries decreases, leading to a reduction in energy efficiency and affecting the actual discharge power. The main reason for this phenomenon is that during long-term charge-discharge processes, pentavalent vanadium in the positive electrode and divalent vanadium in the negative electrode precipitate onto the electrode material surface, covering reactive sites. Consequently, the electrocatalytic activity of the electrodes decreases, and the electrochemical polarization of the battery increases.

[0003] As a crucial component of vanadium battery systems, electrode materials with high conductivity and long service life are essential for ensuring the performance of vanadium batteries. Carbon-based materials are widely used in flow batteries due to their wide availability, low cost, and good conductivity. However, long-term use has revealed numerous problems, such as high overpotential, poor wettability with electrolytes, and a limited number of active sites. Carbon-based materials can no longer meet the current requirements of vanadium batteries. Directly burning waste carbon electrodes is not only a huge waste of resources but also releases large amounts of carbon dioxide, which is detrimental to the environment.

[0004] Therefore, modification treatment is necessary. Common modification methods in the industry include intrinsic material treatment, metallization, and heteroatom doping. However, these methods all have certain problems. For example, heteroatom doping introduces elements detrimental to vanadium battery performance; intrinsic material treatment is environmentally polluting, difficult to operate, energy-intensive, and often leads to decreased electrode conductivity. Modifying carbon fiber felt with carbon nanotubes is a recently emerging improvement method. The main approach involves introducing a carbon source onto the carbon fiber surface and then generating carbon nanotubes under certain conditions. While this method can effectively introduce and control the amount of carbon nanotubes, it is complex to operate, has a small production scale, and is unsuitable for carbon fiber felt used in vanadium batteries. Another method involves introducing an intermediate layer onto the carbon fiber felt to connect the carbon nanotubes. Compared to adsorbing carbon nanotubes onto the carbon fiber felt, this method achieves a tighter bond between the carbon nanotubes and the felt, but the introduced intermediate layer reduces the conductivity of the carbon fiber felt.

[0005] Therefore, providing a method for recycling and reusing waste vanadium redox flow battery electrode materials is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a method for recycling and regenerating waste electrode materials of vanadium redox flow batteries, aiming to enable waste electrodes to obtain battery performance comparable to or even higher than that of the initial electrodes, and to reuse them as electrodes of vanadium redox flow batteries, thereby reducing the cost of electrode materials for vanadium redox flow batteries.

[0007] To achieve the above objectives, this invention provides a method for recycling and regenerating waste electrode materials from vanadium redox flow batteries, the specific steps of which are as follows:

[0008] (1) Pretreatment: Rinse the waste electrode material with deionized water, immerse it in an acid solution, rinse the acid solution clean, and dry it; immerse the obtained waste electrode material in acetone, then clean it and dry it.

[0009] The waste electrode material is a carbon-based material;

[0010] (2) Modification of waste electrodes: The pretreated waste electrodes are carboxylated to obtain modified waste electrodes;

[0011] (3) In-situ growth of carbon nanotubes: The modified waste electrode is immersed in the carbon nanotube catalyst solution for a certain period of time. After being taken out, it is first roasted in an inert atmosphere, and then a mixture of H2 and C2H2 gas is introduced to continue roasting to obtain the waste electrode with in-situ growth of carbon nanotubes.

[0012] (4) Surface amination treatment: The waste electrode with in-situ grown carbon nanotubes is subjected to plasma modification. The power of the plasma processor is 200W-260W, the gas flow rate is 15ml / min-40ml / min of high-purity NH3, the gas pressure is 1kPa-5kPa, and the treatment time is 1h-2h to obtain the surface amination waste electrode.

[0013] (5) Grafting carbon nanotubes: Take another carbon nanotube and disperse it in a strong acid to oxidize the carbon nanotubes to obtain activated carbon nanotubes, and then disperse it in an acetone solution for later use; immerse the obtained surface-aminated waste electrode in the acetone solution of activated carbon nanotubes, soak it at room temperature for 3-5 hours, wash it with deionized water and dry it to obtain a regenerated electrode with surface-grafted carbon nanotubes.

[0014] Preferably, in step (1), the acid solution is one or both of sulfuric acid and nitric acid solutions, and the concentration of the acid solution is 2 mol / L; the immersion time in the acid solution is 1-3 h, and the immersion time in acetone is more than 10 h.

[0015] Preferably, in step (2), the carboxylation treatment is as follows: the pretreated waste electrode is immersed in an aqueous solution composed of K2S2O8 and AgNO3, heated at 60-80℃ for 2-3 hours, cleaned and dried to obtain the modified waste electrode.

[0016] Preferably, the concentrations of K2S2O8 and AgNO3 in the aqueous solution are both 0.1 mol / L.

[0017] Preferably, in step (3), the carbon nanotube catalyst solution is a cobalt or nickel nitrate solution, the concentration of cobalt or nickel ions in the carbon nanotube catalyst solution is 0.01-0.05 mol / L, and the soaking time is 10-30 min.

[0018] Preferably, in step (3), the calcination operation is as follows: first, in an inert atmosphere, at 450°C, heat for 10-15 minutes, then introduce a mixed gas of H2 and C2H2, heat to 600-700°C, and heat for 5-10 minutes;

[0019] The total flow rate of H2 and C2H2 is 0.1-0.5 L / min, and the flow rate ratio of H2 to C2H2 is 2:1.

[0020] Preferably, in step (5), the strong acid is a mixed solution of concentrated sulfuric acid and concentrated nitric acid, with a volume ratio of 3:1 between the concentrated sulfuric acid and concentrated nitric acid; the carbon nanotube oxidation treatment is performed at 50-80°C for 2-3 hours.

[0021] Preferably, in step (5), the solid-liquid ratio of the carbon nanotube to the strong acid is 0.2-1g:50mL.

[0022] Preferably, in step (5), the mass fraction of activated carbon nanotubes in the acetone solution of activated carbon nanotubes is 5-10%.

[0023] Preferably, in step (5), the mass ratio of the surface-aminated waste electrode to the functionally activated carbon nanotube is 1:(0.01-0.2).

[0024] This invention modifies waste carbon electrodes by generating active oxygen-containing groups (such as carboxyl and hydroxyl groups) on the surface, improving the surface activity and surface roughness of the waste electrodes. Through soaking, carbon nanotube catalysts are uniformly distributed on the modified electrode surface. The catalyst is first reduced to a metallic element, and then C2H2 cleaves on the surface of the metallic element, generating carbon nanotubes in situ at the contact point between the metallic element and the carbon electrode. These carbon nanotubes are intertwined, improving the mechanical properties of the waste electrode. This invention further modifies the electrode by amination and chemically grafting activated carbon nanotubes. By forming chemical bonds between the activated carbon nanotubes and the waste electrode, the carbon nanotubes are firmly bonded to the electrode, preventing the carbon nanotubes from detaching during long-term use in the reuse process, which leads to decreased battery performance and low utilization. Furthermore, by employing carboxylation, amination, and activated carbon nanotube treatments, this invention increases the content of oxygen-containing functional groups on the electrode surface, providing more active sites for the regenerated electrode material and solving the problem of decreased electrical performance of waste electrodes.

[0025] As can be seen from the above technical solution, compared with the prior art, the technical effects achieved by the present invention are as follows:

[0026] This invention utilizes carboxylation, amination, and grafting activation of carbon nanotubes to achieve two main effects: firstly, to uniformly wind in-situ generated carbon nanotubes onto the surface of a carbon electrode, increasing the surface roughness of the waste electrode and improving its mechanical properties; secondly, to chemically graft and activate carbon nanotubes, making them less prone to detachment and allowing the regenerated electrode to maintain operation for a longer period, thus improving cycle life; and thirdly, the preparation method is simple and suitable for industrial production. Finally, multiple modifications provide more active sites, enhancing the electrochemical performance of the regenerated electrode. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1: A method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. The specific steps are as follows:

[0029] (1) Pretreatment: Disassemble the waste vanadium redox flow battery, take out the waste carbon fiber felt, rinse with deionized water, immerse in 2 mol / L sulfuric acid solution at room temperature, sonicate for 2 h, rinse with deionized water and dry; then immerse the waste electrode material in acetone for 12 h, sonicate clean and dry.

[0030] (2) Modification of waste electrodes: The pretreated carbon fiber felt was soaked in a mixed solution of K2S2O8 (0.1mol / L) and AgNO3 (0.1mol / L), heated at 70°C for 3 hours, cleaned with a mixed solution of deionized water and acetone, and dried to obtain carboxylated carbon fiber felt.

[0031] (3) In-situ growth of carbon nanotubes: The carboxylated carbon fiber felt was immersed in a 0.03 mol / L cobalt nitrate solution for 10 min. After being taken out, it was first kept at 450℃ for 10 min in an inert atmosphere, and then a mixture of H2 and C2H2 gas (total flow rate of 0.2 L / min, flow rate ratio of H2 and C2H2 of 2:1) was introduced. The temperature was raised to 600℃ and kept for 5 min to obtain carbon fiber felt with in-situ grown carbon nanotubes.

[0032] (4) Surface amination treatment: The carbon fiber felt with in-situ grown carbon nanotubes was subjected to plasma modification. The plasma processor had a power of 220W, the gas flow rate was 20ml / min of high-purity NH3, the gas pressure was 3kPa, and the treatment time was 1h to obtain surface amination carbon fiber felt.

[0033] (5) Grafting carbon nanotubes: Take carbon nanotubes and disperse them in a strong acid (the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1, the concentration of concentrated sulfuric acid is >90%, and the concentration of concentrated nitric acid is >70%). Heat treat at 60°C for 2 hours to obtain activated carbon nanotubes. Disperse the activated carbon nanotubes in an acetone solution (the mass fraction of activated carbon nanotubes is 5%) for later use. The solid-liquid ratio of carbon nanotubes to strong acid is 0.5g:50mL. Immerse the surface-aminated carbon fiber felt in the acetone solution of activated carbon nanotubes. The mass ratio of the surface-aminated carbon fiber felt to the activated carbon nanotubes in the acetone solution is 1:0.1. Soak at room temperature for 4 hours, wash with deionized water, and dry to obtain a regenerated electrode with surface-grafted carbon nanotubes.

[0034] Example 2: A method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. The specific steps are as follows:

[0035] The only difference from Example 1 is: (2) Waste electrode modification: The pretreated carbon fiber felt was soaked in a mixed solution of K2S2O8 (0.1mol / L) and AgNO3 (0.1mol / L), heated at 70°C for 2 hours, cleaned with a mixed solution of deionized water and acetone, and dried to obtain carboxylated carbon fiber felt.

[0036] The remaining steps are the same.

[0037] Example 3: A method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. The specific steps are as follows:

[0038] The difference from Example 1 is only in that: (3) In-situ growth of carbon nanotubes: The carboxylated carbon fiber felt was immersed in a 0.01 mol / L cobalt nitrate solution for 10 min. After taking it out, it was first kept at 450°C for 12 min in an inert atmosphere, and then a mixture of H2 and C2H2 gas (total flow rate of 0.2 L / min, flow rate ratio of H2 and C2H2 of 2:1) was introduced. The temperature was raised to 600°C and kept for 5 min to obtain carbon fiber felt with in-situ grown carbon nanotubes.

[0039] The remaining steps are the same.

[0040] Example 4: A method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. The specific steps are as follows:

[0041] The difference from Example 1 is only in that: (3) In-situ growth of carbon nanotubes: The carboxylated carbon fiber felt was immersed in a 0.03 mol / L cobalt nitrate solution for 10 min. After taking it out, it was first kept at 450°C for 10 min in an inert atmosphere, and then a mixture of H2 and C2H2 gas (total flow rate of 0.4 L / min, flow rate ratio of H2 and C2H2 of 2:1) was introduced. The temperature was raised to 650°C and kept at 8 min to obtain carbon fiber felt with in-situ grown carbon nanotubes.

[0042] The remaining steps are the same.

[0043] Example 5: A method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. The specific steps are as follows:

[0044] The only difference from Example 1 is: (4) Surface amination treatment: the carbon fiber felt with in-situ grown carbon nanotubes is subjected to plasma modification. The power of the plasma processor is 240W, the gas flow rate is 20ml / min of high-purity NH3, the gas pressure is 3kPa, and the treatment time is 1h to obtain surface amination carbon fiber felt.

[0045] The remaining steps are the same.

[0046] Example 6: A method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. The specific steps are as follows:

[0047] The only difference from Example 1 is: (4) Surface amination treatment: the carbon fiber felt with in-situ grown carbon nanotubes is subjected to plasma modification. The power of the plasma processor is 220W, the gas flow rate is 40ml / min of high-purity NH3, the gas pressure is 4kPa, and the treatment time is 1h to obtain surface amination carbon fiber felt.

[0048] The remaining steps are the same.

[0049] Example 7: A method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. The specific steps are as follows:

[0050] The difference from Example 1 is only in the following aspects: (5) Grafting carbon nanotubes: Take carbon nanotubes and disperse them in a strong acid (the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1), heat-treat at 60°C for 2 hours to obtain activated carbon nanotubes, and ultrasonically disperse the activated carbon nanotubes in an acetone solution (the mass fraction of activated carbon nanotubes is 10%) for later use, wherein the solid-liquid ratio of carbon nanotubes to strong acid is 0.5g:50mL; immerse the surface-aminated carbon fiber felt in the acetone solution of activated carbon nanotubes, wherein the mass ratio of the surface-aminated carbon fiber felt to the activated carbon nanotubes in the acetone solution of activated carbon nanotubes is 1:0.05, soak at room temperature for 4 hours, wash with deionized water and dry to obtain a regenerated electrode with surface-grafted carbon nanotubes.

[0051] The remaining steps are the same.

[0052] Example 8: A method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. The specific steps are as follows:

[0053] The difference from Example 1 is only in the following aspects: (5) Grafting carbon nanotubes: Carbon nanotubes are dispersed in a strong acid (the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1), and heat-treated at 60°C for 2 hours to obtain activated carbon nanotubes. The activated carbon nanotubes are ultrasonically dispersed in an acetone solution (the mass fraction of activated carbon nanotubes is 5%) for later use. The solid-liquid ratio of carbon nanotubes to strong acid is 1 g: 50 mL. The surface-aminated carbon fiber felt is immersed in the acetone solution of activated carbon nanotubes. The mass ratio of the surface-aminated carbon fiber felt to the activated carbon nanotubes in the acetone solution is 1:0.2. The solution is soaked at room temperature for 4 hours, washed with deionized water, and dried to obtain a regenerated electrode with surface-grafted carbon nanotubes.

[0054] Example 9: A method for recycling and regenerating waste electrode materials from vanadium redox flow batteries. The specific steps are as follows:

[0055] The only difference from Example 1 is that: (1) the waste electrode material is replaced by carbon cloth instead of carbon fiber felt.

[0056] The remaining steps are the same.

[0057] The recycled carbon felt from Examples 1-9 was used as electrodes to assemble single cells for charge-discharge performance testing. The positive electrode electrolyte was 1.5 M VOC. 2+ 100 mL of 3M H₂SO₄ solution, and 1.5 MV negative electrode electrolyte. 3+ 100 mL of 3M H2SO4 solution;

[0058] The single-cell performance of the new carbon felt as an electrode before regeneration is: at 80 mA / cm². 2The initial voltage efficiency and energy efficiency reached 85.3% and 80.7%, respectively. After 200 cycles, the voltage efficiency and energy efficiency reached 81.5% and 77.3%, respectively. The single cells in each embodiment achieved an efficiency of 80 mA / cm². 2 The battery efficiency at that time is shown in Table 1:

[0059] Table 1

[0060]

[0061] The regeneration method of this invention can enable waste electrodes to achieve battery performance comparable to or even higher than that of the initial electrodes.

[0062] The only difference between Comparative Example 1 and Example 1 is that:

[0063] Operation 1) Do not perform the processing in step (2). The single-cell performance of this electrode material as an electrode is: at 80 mA / cm 2 The initial voltage efficiency and energy efficiency reached 65.3% and 59.7%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 59.6% and 44.3%, respectively.

[0064] In step (2) of operation 2), the pretreated carbon fiber felt is immersed in a K2S2O8 (0.2 mol / L) solution. The single-cell performance of this electrode material as an electrode is: at 80 mA / cm². 2 The initial voltage efficiency and energy efficiency reached 89.4% and 84.9%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 83.5% and 78.8%, respectively.

[0065] In step (2) of operation 3), the pretreated carbon fiber felt was immersed in a mixed solution of K2S2O8 (0.1 mol / L) and AgNO3 (0.1 mol / L) and heated at 100°C for 3 hours. The single-cell performance of this electrode material as an electrode is: at 80 mA / cm 2 The initial voltage efficiency and energy efficiency reached 74.0% and 70.9%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 70.7% and 65.1%, respectively.

[0066] The only difference between Comparative Example 2 and Example 1 is that:

[0067] Operation 1) without the treatment in step (3); the single-cell performance of the electrode material as an electrode is similar to the electrochemical performance of the pretreated waste electrode.

[0068] In step (3) of operation 2), a mixture of H2, C2H2 and inert gas (total flow rate of 0.2 L / min, flow ratio of H2 to C2H2 of 2:1, volume percentage of 20%) is directly introduced. The mixture is first held at 450℃ for 10 min, then heated to 600℃ and held for 5 min. The single-cell performance of this electrode material as an electrode is: at 80 mA / cm²... 2 The initial voltage efficiency and energy efficiency reached 63.4% and 65.1%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 50.4% and 49.1%, respectively.

[0069] In operation 3) step (3), the flow ratio of H2 to C2H2 is 1:2; the single-cell performance of this electrode material as an electrode is: at 80 mA / cm 2 The initial voltage efficiency and energy efficiency reached 76.9% and 75.0%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 51.6% and 53.4%, respectively.

[0070] The only difference between Comparative Example 3 and Example 1 is that:

[0071] In operation 1) step (4): the power of the plasma processor is 180W, the gas flow rate is 20ml / min of high-purity NH3, the gas pressure is 3kPa, and the processing time is 1h; the single-cell performance of the electrode material as an electrode is: at 80mA / cm 2 The initial voltage efficiency and energy efficiency reached 74.3% and 73.2%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 71.8% and 70.1%, respectively.

[0072] In step (4) of operation 2): the power of the plasma processor is 280W, the gas flow rate is 20ml / min of high-purity NH3, the gas pressure is 3kPa, and the processing time is 1h; the single-cell performance of the electrode material as an electrode is: at 80mA / cm 2 The initial voltage efficiency and energy efficiency reached 78.0% and 71.2%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 73.2% and 63.4%, respectively.

[0073] In operation 3) step (4): the plasma processor has a power of 220W, the inlet gas flow rate is 10ml / min of high-purity NH3, the gas pressure is 3kPa, and the processing time is 1h; the single-cell performance of the electrode material as an electrode is: at 80mA / cm 2 The initial voltage efficiency and energy efficiency reached 73.8% and 74.0%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 66.3% and 63.9%, respectively.

[0074] Operation 4) In step (4): the plasma processor has a power of 220W, the inlet gas flow rate is 50ml / min of high-purity NH3, the gas pressure is 3kPa, and the processing time is 1h. The single-cell performance of this electrode material as an electrode is: at 80mA / cm 2 The initial voltage efficiency and energy efficiency reached 77.6% and 76.2%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 66.8% and 63.1%, respectively.

[0075] The only difference between Comparative Example 4 and Example 1 is that:

[0076] Operation 1) Do not perform the treatment in step (5); the single-cell performance of this electrode material as an electrode is: at 80 mA / cm 2 The initial voltage efficiency and energy efficiency reached 63.2% and 60.5%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 54.9% and 51.5%, respectively.

[0077] In step (5) of operation 2), carbon nanotubes are not activated; instead, the surface-aminated carbon fiber felt is directly immersed in an acetone solution of carbon nanotubes. The single-cell performance of this electrode material as an electrode is: at 80 mA / cm². 2 The initial voltage efficiency and energy efficiency reached 73.7% and 70.0%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 63.6% and 61.2%, respectively.

[0078] In step (5) of operation 3), the mass ratio of surface-aminated carbon fiber felt to activated carbon nanotubes in the acetone solution is 1:1. The single-cell performance of this electrode material as an electrode is: at 80 mA / cm². 2 The initial voltage efficiency and energy efficiency reached 89.7% and 85.2%, respectively, and after 200 cycles, the voltage efficiency and energy efficiency reached 83.0% and 79.4%, respectively.

[0079] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recycling and regenerating waste electrode materials from vanadium redox flow batteries, characterized in that, The specific steps are as follows: (1) Pretreatment: Rinse the waste electrode material with deionized water, immerse it in an acid solution, rinse the acid solution clean, and dry it; immerse the obtained waste electrode material in acetone, then clean it and dry it. The waste electrode material is a carbon-based material; (2) Modification of waste electrode materials: The pretreated waste electrode materials are carboxylated to obtain modified waste electrode materials; The carboxylation treatment is as follows: the pretreated waste electrode material is immersed in an aqueous solution composed of K2S2O8 and AgNO3, heated at 60-80℃ for 2-3 hours, washed and dried to obtain the modified waste electrode material. (3) In-situ growth of carbon nanotubes: The modified waste electrode material is immersed in a carbon nanotube catalyst solution, taken out and first roasted under an inert atmosphere, then a mixture of H2 and C2H2 gas is introduced and roasted again to obtain waste electrode material with in-situ growth of carbon nanotubes. The roasting process is as follows: first, keep the temperature at 450℃ for 10-15 minutes under an inert atmosphere, then introduce a mixed gas of H2 and C2H2, raise the temperature to 600-700℃, and keep the temperature for 5-10 minutes. The total flow rate of H2 and C2H2 is 0.1-0.5 L / min, wherein the flow rate ratio of H2 to C2H2 is 2:1; (4) Surface amination treatment: The waste electrode material with in-situ grown carbon nanotubes is subjected to plasma modification. The plasma processor has a power of 200W-260W, the gas flow rate is 15ml / min-40ml / min of high-purity NH3, the gas pressure is 1kPa-5kPa, and the treatment time is 1h-2h to obtain surface amination waste electrode material. (5) Grafting carbon nanotubes: Carbon nanotubes are dispersed in a strong acid and oxidized to obtain activated carbon nanotubes, which are then dispersed in an acetone solution. The resulting surface-aminated waste electrode material is immersed in the acetone solution of activated carbon nanotubes, soaked at room temperature, washed with deionized water, and dried to obtain a regenerated electrode with surface-grafted carbon nanotubes. The strong acid is a mixed solution of concentrated sulfuric acid and concentrated nitric acid, with a volume ratio of 3:1; the carbon nanotube oxidation treatment is carried out at 50-80℃ for 2-3 hours.

2. The method for recycling and regenerating waste electrode materials from a vanadium redox flow battery according to claim 1, characterized in that, In step (1), the acid solution is one or both of sulfuric acid and nitric acid solutions, and the concentration of the acid solution is 2 mol / L; the immersion time in the acid solution is 1-3 h, and the immersion time in acetone is more than 10 h.

3. The method for recycling and regenerating waste electrode materials from a vanadium redox flow battery according to claim 1, characterized in that, The concentrations of K2S2O8 and AgNO3 in the aqueous solution were both 0.1 mol / L.

4. The method for recycling and regenerating waste electrode materials from a vanadium redox flow battery according to claim 1, characterized in that, In step (3), the carbon nanotube catalyst solution is a cobalt or nickel nitrate solution, the concentration of cobalt or nickel ions in the carbon nanotube catalyst solution is 0.01-0.05 mol / L, and the soaking time is 10-30 min.

5. The method for recycling and regenerating waste electrode materials from a vanadium redox flow battery according to claim 1, characterized in that, In step (5), the solid-liquid ratio of the carbon nanotube to the strong acid is 0.2-1g:50mL.

6. The method for recycling and regenerating waste electrode materials from a vanadium redox flow battery according to claim 1, characterized in that, In step (5), the mass fraction of activated carbon nanotubes in the acetone solution of activated carbon nanotubes is 5-10%.

7. The method for recycling and regenerating waste electrode materials from a vanadium redox flow battery according to claim 1, characterized in that, In step (5), the mass ratio of the surface-aminated waste electrode material to the activated carbon nanotubes is 1:(0.01-0.2).

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