A Modified Flow Battery Electrode with Simultaneously Enhanced Activity and Stability and Its Preparation Method

Abstract

The present invention provides a modified flow battery electrode that simultaneously improves activity and stability and a preparation method thereof. The method includes the following steps: adding a carbon felt electrode material into a mixed solution of tin tetrachloride, manganese nitrate, melamine, and urea, performing magnetic stirring, then subjecting it to high-pressure treatment, ultrasonic cleaning, and drying to obtain a modified electrode; adding the modified electrode into a mixed solution of nickel nitrate, melamine, and urea and performing magnetic stirring, subjecting it to high-pressure treatment, ultrasonic cleaning, and drying to obtain a modified electrode; immersing the modified electrode in a mixed solution of nickel nitrate, dopamine hydrochloride, polyamino acid, sodium citrate, and ethanol, washing and drying, then performing high-temperature treatment and acid washing and drying to obtain an activated electrode. The voltage efficiency, energy efficiency, and peak power density are greatly improved, significantly enhancing the electrocatalytic activity of the flow battery. While enhancing the electrocatalytic activity, the stability of the electrode is also greatly improved.

Description

Technical Field

[0001] The present invention relates to a flow battery energy storage technology, and particularly to a modified flow battery electrode that can improve both activity and stability and a preparation method thereof. Background Art

[0002] As a new energy storage method, flow battery energy storage has become an important form of energy storage due to its intrinsic safety, environmental friendliness and other advantages. The electrode, as the place for the redox reaction of the flow battery, directly affects the performance of the flow battery. To improve the electrode performance, physical and chemical treatments, modifications, heteroatoms, etc. are commonly used to improve the electrode voltage efficiency, energy efficiency and specific surface area, and reduce the activation polarization, concentration polarization and ohmic polarization of the electrochemical reaction. However, since the substances introduced from the outside cannot exist stably in a strong acid environment for a long time, these treatment methods often cannot improve the cycle stability of the electrode, and may even lead to a decrease in stability, which directly affects the service life of the flow battery after long-term cycling. Therefore, there is an urgent need for a modified flow battery electrode that can improve both activity and stability at the present stage. Summary of the Invention

[0003] To overcome the problems in the prior art, the present application provides a modified flow battery electrode that can improve both activity and stability and a preparation method thereof.

[0004] To achieve the above object, the present invention provides a preparation method of a modified flow battery electrode that can improve both activity and stability, which includes the following steps:

[0005] (1) The carbon felt is cleaned with ethanol and deionized water, and then ultrasonically treated and dried to obtain a treated electrode material;

[0006] (2) The treated electrode material is added to a mixed solution of tin tetrachloride, manganese nitrate, melamine and urea, magnetically stirred, then treated under high pressure, ultrasonically cleaned and dried to obtain a modified electrode;

[0007] (3) The modified electrode is added to a mixed solution of nickel nitrate, melamine and urea, magnetically stirred, treated under high pressure, ultrasonically cleaned and dried to obtain a modified electrode;

[0008] (4) The modified electrode is immersed in a mixed solution of nickel nitrate, hydrochloric acid dopamine, polyamino acid, sodium citrate and ethanol, washed and dried, then treated at high temperature and pickled and dried to obtain an activated electrode.

[0009] Preferably, in step (1), the ultrasonic treatment is ultrasonic oscillation treatment for 20 - 30 min, the cleaning is first cleaning with ethanol and then cleaning with deionized water 2 - 3 times, and the drying is drying at 60 °C for 10 - 12 h.

[0010] Preferably, in steps (2) and (3), for the ultrasonic cleaning, it is ultrasonic cleaning for 2 - 3 times followed by drying at 60 °C for 6 - 8 h.

[0011] Preferably, in steps (2) and (3), for the high - pressure treatment, it is reacting in a high - pressure reactor at a temperature of 122 - 128 °C for 2 - 2.5 h.

[0012] Preferably, in step (4), by mass, the dopamine hydrochloride is 0.30 - 0.40 parts, the polyamino acid is 0.28 - 0.30 parts, the nickel nitrate is 0.20 - 0.35 parts, the sodium citrate is 0.48 - 0.50 parts, and the volume ratio of ethanol to deionized water is 1:1.

[0013] Preferably, in step (4), by mass, the dopamine hydrochloride is 0.32 - 0.36 parts, the polyamino acid is 0.28 - 0.30 parts, the nickel nitrate is 0.24 - 0.25 parts, the sodium citrate is 0.48 - 0.50 parts, and the volume ratio of ethanol to deionized water is 1:1.

[0014] Preferably, in step (4), for the high - temperature treatment, it is heating to 780 - 820 °C at a heating rate of 1 - 2 °C / min in a nitrogen atmosphere and holding for 1.5 - 2 h.

[0015] Preferably, in step (4), for the pickling, it is immersing the sample in a 1 - 2 mol / L oxalic acid or sulfamic acid solution for washing 2 - 3 times, and washing with deionized water until the pH of the washing liquid is greater than 6.

[0016] Preferably, in step (1), by mass, stannic chloride is 0.80 - 1.0 part, manganese nitrate is 0.45 - 0.60 parts, melamine is 0.25 - 0.33 parts, and urea is 0.11 - 0.13 parts.

[0017] Preferably, in step (1), by mass, stannic chloride is 0.86 - 0.94 parts, manganese nitrate is 0.51 - 0.55 parts, melamine is 0.25 - 0.33 parts, and urea is 0.11 - 0.13 parts.

[0018] The present invention also provides a modified flow - battery electrode with simultaneously improved activity and stability obtained by the above - mentioned method: the surface of the activated electrode has a needle - shaped nanostructure coating film.

[0019] Preferably, the surface area of the activated electrode is greater than 50 m 2 / g, the energy efficiency is increased by 13.9% compared with the original electrode, and the stability is 5 times that of the original electrode.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] After the pretreatment of the electrode, the modification of the nanosheets, the modification of the material loading, and the formation of the defect structure and activation, the specific surface area of the electrode of the present invention is increased by 2 times compared with the original electrode after physical and chemical pretreatment, reaching 69.4 m 2 / g, providing rich reaction sites for the redox reaction of the flow battery, improving the chemical reaction kinetics, and promoting the utilization of the electrolyte.

[0022] After the introduction of tin (Sn), the potential is adjusted and optimized. The introduction of nickel (Ni) strengthens the adsorption of the electrode to the electroactive ions, enhancing the reaction kinetics of the reactants, significantly improving the electrocatalytic activity of the flow battery with a substantial increase in voltage efficiency, energy efficiency, and peak power density. After treatment, the energy efficiency is increased by 13.9% compared with the original electrode, and the performance is greatly improved.

[0023] After the defect and optimization steps, the present invention realizes the in-situ polymerization of dopamine hydrochloride on the surface of the modified electrode under the protection of polyamino acid, inducing the formation of surface defects of the electrode and an acid-resistant sacrificial protective film, promoting the transfer of the redox reaction center to the nanosheets and the loaded active sites, and creating more active areas. While enhancing the electrocatalytic activity, the stability of the electrode is also greatly improved. After treatment, the number of cycles in which the stability can stably maintain the energy efficiency above 95% of the energy efficiency in the first cycle is 5 times that of the original electrode. Description of the Drawings

[0024] Figure 1 It is the scanning electron microscope micrograph of Example 1 of the present invention. Among them, (a) is the structure of the modified electrode obtained in step (2), and it can be seen that 1-5 μm nanosheets are attached. The surface area of the electrode is about 41.5 m 2 / g through specific surface area measurement; (b) is the structure of the modified electrode obtained in step (3), and it can be seen that the structure is more complex and the size of the nanostructure is reduced, and its surface area is about 50.2 m 2 / g; (c) is the structure of the activated electrode obtained in step (3), and it can be seen that needle-like nanostructures are coated on the surface, and its surface area is about 69.4 m 2 / g.

[0025] Figure 2 It is the peak current of the current-voltage curve of Example 1 of the present invention at different scanning rates. The peak potential ratios of the electroactive pairs VO 2+ / VO 2 + and V 3+ / V 2+ in Example 1 are all lower than those in Comparative Example 4, indicating the improvement of the electrode performance in Example 1.

[0026] Figure 3 For Example 1 of the present invention, when the current density is 100 mA / cm 2 After multiple cycles, the change in energy efficiency can exceed 1600 cycles, while the cycle stability of Comparative Example 4 remains at 306 cycles.

[0027] Figure 4 This is the technical roadmap of the method of the present invention. Detailed implementation manners

[0028] To better illustrate the purpose, technical solution and advantages of the present invention, the present application will be further described below in conjunction with specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention. In addition, in the following description, the description of well-known technical information is omitted to avoid confusion and chaos.

[0029] A modified flow battery electrode that simultaneously improves activity and stability includes the following steps:

[0030] (1) Carbon felt pretreatment. Cut the commercial carbon felt into square small pieces with a side length of 8-10 cm. Wash it with absolute ethanol 2-3 times, treat it for 20-30 min under ultrasonic vibration, then wash it with deionized water 2-3 times, and place it in an oven at 60°C for drying for 10-12 h for later use.

[0031] (2) Nanosheet modification. Under magnetic stirring, mix 0.86-0.94 g of tin tetrachloride, 0.71-0.77 g of manganese nitrate tetrahydrate, 0.25-0.33 g of melamine, and 0.11-0.13 g of urea in 23-27 mL of deionized water, and treat it under magnetic stirring for 20-30 min. Put the 2 carbon felts obtained in step 1 and the solution obtained above into a polytetrafluoroethylene inner liner and react in a high-pressure reaction kettle at 122-128°C for 2-2.5 h. After the reaction is completed and cooled to room temperature, ultrasonically clean it 2-3 times and place it in an oven at 60°C for drying for 6-8 h to obtain SnMnO4 nanosheets loaded on the electrode.

[0032] (3)Loading modification of carbon felt material. Under magnetic stirring, 0.78 - 0.80 g of nickel nitrate hexahydrate, 0.25 - 0.33 g of melamine, and 0.11 - 0.13 g of urea were mixed in 23 - 27 mL of deionized water and treated under magnetic stirring for 20 - 30 min. The SnMnO4 nanosheets loaded on the two electrodes obtained in step 2 and the solution obtained above were placed in a polytetrafluoroethylene liner and reacted in a high-pressure reactor at 122 - 128 °C for 2 - 2.5 h. After the reaction ended and cooled to room temperature, it was ultrasonically cleaned 2 - 3 times and placed in an oven at 60 °C for drying for 6 - 8 h. The SnMnO4 / Ni(OH) 2 composite nanosheets were obtained;

[0033] (4)Forming defects and activation. Under the condition of magnetic stirring, 0.32 - 0.36 g of dopamine hydrochloride, 0.28 - 0.30 g of polyamino acid, 0.39 - 0.40 g of nickel nitrate hexahydrate, and 0.55 - 0.57 g of sodium citrate dihydrate were added to 35 - 45 mL of ethanol and deionized water (volume ratio 1:1). The two electrodes obtained in step 3 were immersed in the above solution and magnetically stirred for 2 - 3 h, then dried at 60 °C for 10 - 12 h. The obtained electrodes were treated at 780 - 820 °C for 1.5 - 2 h in a nitrogen atmosphere at a heating rate of 1 - 2 °C / min. After natural cooling, the samples were immersed in 1 - 2 mol / L oxalic acid or sulfamic acid solution for washing 2 - 3 times, and washed with deionized water until the pH of the washing solution was greater than 6. The electrode products were dried at 60 °C for 10 - 12 h. The obtained activated electrodes were assembled into a stack and various performance tests were carried out.

[0034] Example 1

[0035] (1)The commercial carbon felt was cut into small square pieces with a side length of 9 cm. It was washed 3 times with absolute ethanol, treated for 25 min under ultrasonic vibration, then washed 3 times with deionized water, and placed in an oven at 60 °C for drying for 11 h for standby. Its surface area was about 23.2 m 2 / g,

[0036] (2)Under magnetic stirring, 0.90 g of tin tetrachloride, 0.74 g of manganese nitrate tetrahydrate, 0.29 g of melamine, and 0.12 g of urea were mixed in 25 mL of deionized water and treated under magnetic stirring for 25 min. The two carbon felts obtained in step 1 and the solution obtained above were placed in a polytetrafluoroethylene liner and reacted in a high-pressure reactor at 125 °C for 2.5 h. After the reaction ended and cooled to room temperature, it was ultrasonically cleaned 3 times and placed in an oven at 60 °C for drying for 7 h to obtain the SnMnO 4 nanosheets loaded on the electrode. This structure was a nanosheet structure grown on the electrode surface, as Figure 1In part (a), the specific surface area of the electrode is greatly increased. The areal mass loading of this structure is 0.53 mg / cm 2 . Due to reasons such as potential adjustment, the introduction of Sn improves the energy efficiency by 6.7% compared to the original electrode and maintains higher cycle stability. Its surface area is approximately 41.5 m 2 / g;

[0037] (3) Under magnetic stirring, 0.79 g of nickel nitrate hexahydrate, 0.29 g of melamine, and 0.12 g of urea are mixed in 25 mL of deionized water and treated under magnetic stirring for 25 min. The SnMnO 4 nanosheets loaded on the 2 electrodes obtained in step 2 and the solution obtained above are placed in a polytetrafluoroethylene inner liner and reacted in a high-pressure reactor at 125 °C for 2.5 h. After the reaction is completed and cooled to room temperature, it is ultrasonically cleaned 3 times and placed in an oven at 60 °C for drying for 7 h. The SnMnO 4 / Ni(OH) 2 composite nanosheets are obtained. The areal mass loading of this structure is 0.66 mg / cm 2 , and the structure is as shown in Figure 1 part (b). The introduction of Ni strengthens the adsorption of redox ions, improves the reaction kinetics, and further improves the energy efficiency by 2.1% compared to the electrode in step 2. Its surface area is approximately 50.2 m 2 / g;

[0038] (4) Under magnetic stirring, 0.34 g of dopamine hydrochloride, 0.29 g of polyamino acid, 0.40 g of nickel nitrate hexahydrate, and 0.56 g of sodium citrate dihydrate are added to 40 mL of ethanol and deionized water (volume ratio 1:1). After the 2 electrodes obtained in step 3 are immersed in the above solution and stirred magnetically for 2.5 h, they are dried at 60 °C for 11 h. The obtained electrodes are heated in a nitrogen atmosphere at a heating rate of 1.5 °C / min to 800 °C and held for 1.5 h. After natural cooling, the samples are immersed in 1.5 mol / L oxalic acid or sulfamic acid solution for washing 3 times, and washed with deionized water until the pH of the washing solution is greater than 6. The electrode products are dried at 60 °C for 11 h. The obtained electrodes are assembled into a stack and various performance tests are carried out. By increasing the specific surface area, more reaction sites are provided for the redox reaction, as shown in Figure 1 part (c). The energy efficiency and peak power density are greatly improved, significantly enhancing the electrocatalytic activity and stability of the all-vanadium redox flow battery. Its surface area is approximately 69.4 m 2 / g, which is three times that of the original electrode. The energy efficiency is improved by 13.9% compared to the original electrode, and the stability is 5 times that of the original electrode.

[0039] Example 2

[0040] (1) Cut commercial carbon felt into small square pieces with a side length of 8 cm. Wash it 3 times with absolute ethanol, treat it for 20 min under ultrasonic vibration, then wash it 3 times with deionized water, and place it in an oven at 60 °C for drying for 12 h for later use.

[0041] (2) Under magnetic stirring, mix 0.86 g of tin tetrachloride, 0.77 g of manganese nitrate tetrahydrate, 0.25 g of melamine, and 0.13 g of urea in 27 mL of deionized water, and treat it for 20 min under magnetic stirring. Put the 2 pieces of carbon felt obtained in step 1 and the solution obtained above into a polytetrafluoroethylene inner liner and react in a high-pressure reactor at 128 °C for 2 h. After the reaction is completed and cooled to room temperature, wash it ultrasonically 3 times and place it in an oven at 60 °C for drying for 6 h to obtain SnMnO 4 nanosheets loaded on the electrode. The areal mass loading of this structure is 0.54 mg / cm 2 ;

[0042] (3) Under magnetic stirring, mix 0.78 g of nickel nitrate hexahydrate, 0.33 g of melamine, and 0.11 g of urea in 27 mL of deionized water, and treat it for 20 min under magnetic stirring. Put the 2 pieces of SnMnO 4 nanosheets loaded on the electrode obtained in step 2 and the solution obtained above into a polytetrafluoroethylene inner liner and react in a high-pressure reactor at 122 °C for 2.5 h. After cooling to room temperature, wash it ultrasonically 2 times and place it in an oven at 60 °C for drying for 8 h. Obtain SnMnO 4 / Ni(OH) 2 composite nanosheets, and the areal mass loading is 0.64 mg / cm 2 ;

[0043] (4) Under the condition of magnetic stirring, add 0.36 g of dopamine hydrochloride, 0.28 g of polyamino acid, 0.40 g of nickel nitrate hexahydrate, and 0.55 g of sodium citrate dihydrate to 45 mL of ethanol and deionized water (volume ratio 1:1). Immerse the 2 electrodes obtained in step 3 into the above solution and stir magnetically for 2 h, then dry at 60 °C for 12 h. Treat the obtained electrodes in a nitrogen atmosphere at a heating rate of 1 °C / min at 820 °C for 1.5 h. After natural cooling, immerse the sample in 2 mol / L oxalic acid or sulfamic acid solution and wash it 2 times, and wash it with deionized water until the pH of the washing solution is greater than 6. Dry the electrode product at 60 °C for 12 h. Assemble the obtained electrodes into a stack and conduct various performance tests.

[0044] Example 3

[0045] (1) Cut commercial carbon felt into small square pieces with a side length of 10 cm. Wash it twice with absolute ethanol, treat it for 30 min under ultrasonic vibration, then wash it twice with deionized water, and place it in an oven at 60 °C for drying for 10 h for later use.

[0046] (2) Under magnetic stirring, mix 0.94 g of tin tetrachloride, 0.71 g of manganese nitrate tetrahydrate, 0.33 g of melamine, and 0.11 g of urea in 23 mL of deionized water, and treat it under magnetic stirring for 30 min. Put the 2 pieces of carbon felt obtained in step 1 and the solution obtained above into a polytetrafluoroethylene inner liner and react in a high-pressure reactor at 122 °C for 2.5 h. After the reaction is completed and cooled to room temperature, wash it ultrasonically twice and place it in an oven at 60 °C for drying for 8 h to obtain SnMnO 4 nanosheets. The areal mass loading of this structure is 0.52 mg / cm 2 ;

[0047] (3) Under magnetic stirring, mix 0.80 g of nickel nitrate hexahydrate, 0.25 g of melamine, and 0.13 g of urea in 23 mL of deionized water, and treat it under magnetic stirring for 30 min. Put the 2 pieces of SnMnO 4 nanosheets with electrodes obtained in step 2 and the solution obtained above into a polytetrafluoroethylene inner liner and react in a high-pressure reactor at 128 °C for 2 h. After cooling to room temperature, wash it ultrasonically three times and place it in an oven at 60 °C for drying for 6 h. Obtain SnMnO 4 / Ni(OH) 2 composite nanosheets. The areal mass loading is 0.68 mg / cm 2 ;

[0048] (4) Under the condition of magnetic stirring, add 0.32 g of dopamine hydrochloride, 0.30 g of polyamino acid, 0.39 g of nickel nitrate hexahydrate, and 0.57 g of sodium citrate dihydrate to 35 mL of ethanol and deionized water (volume ratio 1:1). Immerse the 2 electrodes obtained in step 3 into the above solution and stir magnetically for 3 h, then dry at 60 °C for 10 h. Treat the obtained electrodes in a nitrogen atmosphere at a heating rate of 2 °C / min at 780 °C for 2 h. After natural cooling, immerse the sample in 1 mol / L oxalic acid or sulfamic acid solution and wash it three times, and wash it with deionized water until the pH of the washing solution is greater than 6. Dry the electrode product at 60 °C for 10 h. Assemble the obtained electrodes into an electric stack and conduct various performance tests.

[0049] Example 4

[0050] (1) Cut commercial carbon felt into small square pieces with a side length of 8 cm. Wash it twice with absolute ethanol, treat it for 20 min under ultrasonic vibration, then wash it twice with deionized water, and place it in an oven at 60 °C for drying for 10 h for later use.

[0051] (2) Under magnetic stirring, mix 0.86 g of tin tetrachloride, 0.71 g of manganese nitrate tetrahydrate, 0.25 g of melamine, and 0.11 g of urea in 23 mL of deionized water, and treat it under magnetic stirring for 20 min. Put the 2 pieces of carbon felt obtained in step 1 and the solution obtained above into a polytetrafluoroethylene inner liner and react in a high-pressure reactor at 122 °C for 2 h. After the reaction is completed and cooled to room temperature, ultrasonically clean it twice and place it in an oven at 60 °C for drying for 6 h to obtain SnMnO 4 nanosheets loaded on the electrode. The areal mass loading of this structure is 0.52 mg / cm 2 ;

[0052] (3) Under magnetic stirring, mix 0.78 g of nickel nitrate hexahydrate, 0.25 g of melamine, and 0.11 g of urea in 23 mL of deionized water, and treat it under magnetic stirring for 20 min. Put the 2 pieces of SnMnO 4 nanosheets loaded on the electrode obtained in step 2 and the solution obtained above into a polytetrafluoroethylene inner liner and react in a high-pressure reactor at 122 °C for 2 h. After cooling to room temperature, ultrasonically clean it twice and place it in an oven at 60 °C for drying for 6 h. Obtain SnMnO 4 / Ni(OH) 2 composite nanosheets. The mass loading is 0.64 mg / cm 2 ;

[0053] (4) Under the condition of magnetic stirring, add 0.32 g of dopamine hydrochloride, 0.28 g of polyamino acid, 0.39 g of nickel nitrate hexahydrate, and 0.55 g of sodium citrate dihydrate to 35 mL of ethanol and deionized water (volume ratio 1:1). Immerse the 2 electrodes obtained in step 3 into the above solution and stir magnetically for 2 h, then dry at 60 °C for 10 h. Treat the obtained electrode in a nitrogen atmosphere at a heating rate of 1 °C / min at 780 °C for 1.5 h. After natural cooling, immerse the sample in 1 mol / L oxalic acid or sulfamic acid solution and wash it twice, and wash it with deionized water until the pH of the washing solution is greater than 6. Dry the electrode product at 60 °C for 10 h. Assemble the obtained electrodes into a stack and conduct various performance tests.

[0054] Example 5

[0055] (1) Cut the commercial carbon felt into small square pieces with a side length of 10 cm. Wash it 3 times with absolute ethanol, treat it for 30 min under ultrasonic vibration, then wash it 3 times with deionized water, and place it in an oven at 60 °C for drying for 12 h for later use.

[0056] (2) Under magnetic stirring, mix 0.94 g of tin tetrachloride, 0.77 g of manganese nitrate tetrahydrate, 0.33 g of melamine, and 0.13 g of urea in 27 mL of deionized water, and treat it for 30 min under magnetic stirring. Put 2 pieces of carbon felt obtained in step 1 and the above-obtained solution into a polytetrafluoroethylene inner lining and react in a high-pressure reactor at 128 °C for 2.5 h. After the reaction is completed and cooled to room temperature, ultrasonically clean it 3 times and place it in an oven at 60 °C for drying for 8 h to obtain SnMnO 4 nanosheets. The areal mass loading of this structure is 0.54 mg / cm 2 ;

[0057] (3) Under magnetic stirring, mix 0.80 g of nickel nitrate hexahydrate, 0.33 g of melamine, and 0.13 g of urea in 27 mL of deionized water, and treat it for 30 min under magnetic stirring. Put 2 pieces of the electrode-supported SnMnO 4 nanosheets and the above-obtained solution into a polytetrafluoroethylene inner lining and react in a high-pressure reactor at 128 °C for 2.5 h. After cooling to room temperature, ultrasonically clean it 3 times and place it in an oven at 60 °C for drying for 8 h. Obtain the electrode-supported SnMnO 4 / Ni(OH) 2 composite nanosheets. The areal mass loading is 0.68 mg / cm 2 ;

[0058] (4) Under the condition of magnetic stirring, add 0.36 g of dopamine hydrochloride, 0.30 g of polyamino acid, 0.40 g of nickel nitrate hexahydrate, and 0.57 g of sodium citrate dihydrate to 45 mL of ethanol and deionized water (volume ratio 1:1). Immerse the electrode obtained in step 3 into the above solution. Immerse 2 pieces of the electrode obtained in step 3 into the above solution and stir magnetically for 3 h, then dry it at 60 °C for 12 h. Treat the obtained electrode in a nitrogen atmosphere at a heating rate of 2 °C / min at 820 °C for 2 h. After natural cooling, immerse the sample in 2 mol / L oxalic acid or sulfamic acid solution and wash it 3 times, and wash it with deionized water until the pH of the washing solution is greater than 6. Dry the electrode product at 60 °C for 12 h. Assemble the obtained electrodes into a stack and conduct various performance tests.

[0059] Comparative Example 1

[0060] (1) Cut the commercial carbon felt into small square pieces with a side length of 9 cm. Wash it 3 times with absolute ethanol, treat it for 25 min under ultrasonic oscillation, then wash it 3 times with deionized water, and place it in an oven at 60 °C for drying for 11 h for later use.

[0061] (2) Under magnetic stirring, mix 0.90 g of tin tetrachloride, 0.74 g of manganese nitrate tetrahydrate, 0.29 g of melamine, and 0.12 g of urea in 25 mL of deionized water, and treat it for 25 min under magnetic stirring. Put the 2 pieces of carbon felt obtained in step 1 and the above-obtained solution into a polytetrafluoroethylene inner liner and react in a high-pressure reactor at 125 °C for 2.5 h. After the reaction is completed and cooled to room temperature, ultrasonically clean it 3 times and place it in an oven at 60 °C for drying for 7 h to obtain SnMnO 4 nanosheets;

[0062] (3) Under magnetic stirring, mix 0.79 g of nickel nitrate hexahydrate, 0.29 g of melamine, and 0.12 g of urea in 25 mL of deionized water, and treat it for 25 min under magnetic stirring. Put the 2 pieces of electrode-supported SnMnO 4 nanosheets and the above-obtained solution into a polytetrafluoroethylene inner liner and react in a high-pressure reactor at 125 °C for 2.5 h. After the reaction is completed and cooled to room temperature, ultrasonically clean it 3 times and place it in an oven at 60 °C for drying for 7 h. Assemble the obtained electrodes into a stack and conduct various performance tests.

[0063] Comparative Example 2

[0064] (1) Cut the commercial carbon felt into small square pieces with a side length of 9 cm. Wash it 3 times with absolute ethanol, treat it for 25 min under ultrasonic oscillation, then wash it 3 times with deionized water, and place it in an oven at 60 °C for drying for 11 h for later use.

[0065] (2) Under magnetic stirring, mix 0.90 g of tin tetrachloride, 0.74 g of manganese nitrate tetrahydrate, 0.29 g of melamine, and 0.12 g of urea in 25 mL of deionized water, and treat it for 25 min under magnetic stirring. Put the 2 pieces of carbon felt obtained in step 1 and the above-obtained solution into a polytetrafluoroethylene inner liner and react in a high-pressure reactor at 125 °C for 2.5 h. After the reaction is completed and cooled to room temperature, ultrasonically clean it 3 times and place it in an oven at 60 °C for drying for 7 h. Assemble the obtained electrodes into a stack and conduct various performance tests.

[0066] Comparative Example 3

[0067] (1) Cut commercial carbon felt into small square pieces with a side length of 9 cm. Wash it three times with absolute ethanol, treat it for 25 min under ultrasonic vibration, then wash it three times with deionized water, and place it in an oven at 60 °C for drying for 11 h for later use.

[0068] (2) Under magnetic stirring, mix 0.79 g of nickel nitrate hexahydrate, 0.29 g of melamine, and 0.12 g of urea in 25 mL of deionized water, and treat it for 25 min under magnetic stirring. Put the two electrodes obtained in step 1 and the solution obtained above into a polytetrafluoroethylene inner lining and react in a high-pressure reactor at 125 °C for 2.5 h. After the reaction is completed and cooled to room temperature, ultrasonically clean it three times and place it in an oven at 60 °C for drying for 7 h. Assemble the obtained electrodes into an electric stack and conduct various performance tests.

[0069] Comparative Example 4

[0070] (1) Cut commercial carbon felt into small square pieces with a side length of 9 cm. Wash it three times with absolute ethanol, treat it for 25 min under ultrasonic vibration, then wash it three times with deionized water, and place it in an oven at 60 °C for drying for 11 h. Assemble the obtained electrodes into an electric stack and conduct various performance tests.

[0071] Table 1. Performance comparison of examples and comparative examples

[0072] ,

[0073] As can be seen from the above table, the specific surface area, energy efficiency, voltage efficiency, and cycle stability of the electrodes in several examples are not very different, but are greatly improved compared with several comparative examples, indicating that after the pretreatment of the electrodes, nanosheet modification, material loading modification, and the formation of defect structures and activation, the present invention effectively improves the electrochemical activity and stability of the electrodes.

[0074] The performance is slightly improved when comparing Comparative Example 3 and Comparative Example 4, indicating that the introduction of Ni strengthens the adsorption of the electrode and electroactive ions, enhances the reaction kinetics of the reactants, and significantly improves the electrocatalytic activity of the flow battery with a large increase in voltage efficiency, energy efficiency, and peak power density. The performance is improved when comparing Comparative Example 2 and Comparative Example 4, indicating that the introduction of Sn adjusts and optimizes the potential, reduces the reaction overpotential, reduces the efficiency loss, and improves the stability. The performance of Comparative Example 2 is improved compared with that of Comparative Example 3, indicating that Sn has a higher promoting effect on performance improvement in this invention than Ni. The performance of Comparative Example 1 is improved compared with that of Comparative Example 2 and Comparative Example 3, indicating that the synergistic effect of Sn and Ni is better than the gain brought by the addition of a single metal.

[0075] In addition, the performance improvement of the examples compared with Comparative Example 1 indicates that through the defect and optimization steps, the in-situ polymerization of dopamine hydrochloride on the surface of the modified electrode under the protection of polyamino acids is achieved, inducing the formation of defects on the electrode surface and an acid-resistant sacrificial protective film, and promoting the transfer of redox reaction centers to the nanosheets and the loaded active sites, while creating more active areas. While enhancing the electrocatalytic activity, the stability of the electrode is also greatly improved.

[0076] By adjusting and optimizing the raw material ratios and experimental parameters of the examples, the specific surface area, energy efficiency, voltage efficiency, cycle stability and other indicators can be slightly improved. This is manifested as partial differences in the performance of Examples 1 to 5 in the table, which is mainly related to the introduction ratios of Sn and Ni. Adjusting and optimizing the potential and strengthening the adsorption of the electrode to the redox ions can improve the electrochemistry activity of the flow battery. The ratio of dopamine hydrochloride to polyamino acids also affects the in-situ polymerization degree on the surface of the modified electrode and the number of redox reaction centers transferred to the nanosheets and the loaded active sites, thus having a certain impact on the cycle stability. The voltage efficiency of several examples is 87.9 - 89.2%, the energy efficiency is 85.8 - 87.1%, the specific surface area is 66.7 - 69.4 m 2 / g, and the cycle stability is 1412 - 1649 times.

[0077] The present invention provides a modified flow battery electrode that simultaneously improves activity and stability. Through the pretreatment of the electrode, nanosheet modification, material loading modification, and formation of defect structures and activation, the activity and stability of the electrode are simultaneously improved. The specific surface area of the electrode of the present invention is increased compared with the original electrode after physical and chemical pretreatment, improving the chemical reaction kinetics and promoting the utilization of the electrolyte. Through the introduction of Sn, the potential is adjusted and optimized, and through the introduction of Ni, the adsorption of the electrode to the redox ions is strengthened. The present invention enhances the reaction kinetics of the reactants, and the voltage efficiency, energy efficiency and peak power density are greatly improved, significantly improving the electrocatalytic activity of the flow battery. Through the defect and optimization steps, the transfer of redox reaction centers to the nanosheets and the loaded active sites is promoted, while creating more active areas. While enhancing the electrocatalytic activity, the stability of the electrode is also greatly improved.

[0078] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a modified flow battery electrode with improved activity and stability, characterized in that: The following steps are included: (1) The carbon felt is cleaned with ethanol and deionized water, then ultrasonicated and dried to obtain the treated electrode material; (2) adding the treated electrode material to a mixture of tin tetrachloride, manganese nitrate, melamine and urea, subjecting the material to high pressure treatment after magnetic stirring, ultrasonic cleaning and drying to obtain a modified electrode; (3) adding the modified electrode to a mixture of nickel nitrate, melamine and urea and subjecting the mixture to magnetic stirring, high pressure treatment, ultrasonic cleaning and drying to obtain a modified electrode; (4) immersing the modified electrode in a mixture of nickel nitrate, dopamine hydrochloride, polyamino acid, sodium citrate and ethanol, washing and drying, and then high temperature treatment, acid washing and drying to obtain an activated electrode; Wherein, in steps (2) and (3), the high pressure treatment is carried out in a high pressure reactor at a temperature of 122-128° C. for 2-2.5 h.

2. The method for preparing a modified liquid flow battery electrode with improved activity and stability according to claim 1, characterized in that: In step (1), the ultrasonic treatment is an ultrasonic oscillation treatment for 20 to 30 min, the cleaning is firstly cleaning with ethanol and then cleaning with deionized water for 2 to 3 times, and the drying is drying at 60° C. for 10 to 12 h.

3. The method for preparing a modified liquid flow battery electrode with improved activity and stability according to claim 1, characterized in that: In steps (2) and (3), the ultrasonic cleaning is performed by ultrasonic cleaning 2 to 3 times and then drying at 60° C. for 6 to 8 hours.

4. The method for preparing a modified liquid flow battery electrode with improved activity and stability according to claim 1, characterized in that: In step (4), by weight, the dopamine hydrochloride is 0.30-0.40 parts, the polyamino acid is 0.28-0.30 parts, the nickel nitrate is 0.20-0.35 parts, the sodium citrate is 0.48-0.50 parts, and the volume ratio of ethanol to deionized water is 1:

1.

5. The method for preparing a modified liquid flow battery electrode with improved activity and stability according to claim 1, characterized in that: In step (4), the high temperature treatment is to heat the mixture to 780-820°C at a heating rate of 1-2°C / min under a nitrogen atmosphere and keep the temperature for 1.5-2 h.

6. The method for preparing a modified liquid flow battery electrode with improved activity and stability according to claim 1, characterized in that: In step (4), the acid washing is performed by immersing the sample in a 1-2 mol / L oxalic acid or aminosulfonic acid solution for 2-3 times, and then washing with deionized water until the pH of the washing solution is greater than 6.

7. The method for preparing a modified liquid flow battery electrode with improved activity and stability according to claim 1, characterized in that: In step (1), by weight, tin tetrachloride is 0.80-1.0 part, manganese nitrate is 0.45-0.60 part, melamine is 0.25-0.33 part, and urea is 0.11-0.13 part.

8. A modified liquid flow battery electrode with improved activity and stability obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The surface of the activated electrode is coated with a needle-shaped nanostructure film.

9. The modified liquid flow battery electrode with improved activity and stability according to claim 8, characterized in that: The specific surface area of ​​the activated electrode is greater than 50 m 2 / g, the energy efficiency is improved by 13.9% compared with the original electrode, and the stability is 5 times that of the original electrode.

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