Method for electrolytically preparing electrolytes for all-vanadium redox flow batteries

Abstract

The application relates to preparation of electrolyte of a full vanadium liquid flow battery, and discloses a method for electrolytically preparing electrolyte of a full vanadium liquid flow battery. The method comprises adding a catalyst into a cathode electrolyte; the catalyst contains modified nano carbon, and the modified nano carbon is carboxylated nano carbon and / or hydroxylated nano carbon. The method can effectively improve an electrolysis rate, effectively reduce energy consumption in an electrolysis process, and reduce the manufacturing cost of the electrolyte of the full vanadium liquid flow battery.

Description

Technical Field

[0001] This invention relates to the preparation of electrolytes for vanadium redox flow batteries, and more specifically to a method for preparing vanadium redox flow battery electrolytes by electrolysis. Background Technology

[0002] Energy is the material foundation for the existence and development of human society. For many years, the energy system based on fossil fuels such as coal, oil, and natural gas has greatly propelled human societal development. However, with development, resources are becoming increasingly depleted, and the environment is continuously deteriorating. In response, my country has proposed a "dual-carbon" target, with the traditional power system gradually being replaced by clean and renewable energy sources such as wind and solar power, becoming the mainstay of my country's future power generation system. However, the instability, intermittency, and uncontrollability of these renewable energy sources limit power generation and transmission. Therefore, developing large-scale energy storage technology to effectively promote clean energy has become an inevitable trend. Electrochemical energy storage, with its advantages of being unaffected by environmental constraints and being environmentally friendly, has become one of the preferred choices for large-scale energy storage power stations. Among these, the mature vanadium redox flow battery technology, with its high safety and long cycle life, is a promising electrochemical energy storage technology.

[0003] The methods for synthesizing electrolytes for vanadium redox flow batteries include physical methods, chemical methods, and electrolytic methods. The physical method mainly involves dissolving trivalent or tetravalent vanadium oxides in a sulfuric acid solution of a certain concentration to obtain the electrolyte directly. However, due to the high price of vanadium oxide raw materials, the cost is relatively high, thus preventing large-scale industrial application.

[0004] Currently, the synthesis of electrolytes for industrial-scale vanadium redox flow batteries mainly involves chemical and electrolytic methods. The chemical method primarily utilizes reducing agents (reducing organic solvents, reducing gases) to reduce inexpensive vanadium pentoxide powder into a tetravalent electrolyte after heating and activation. The use of reducing gases requires a high-pressure reactor, thus placing high demands on equipment and processes. Furthermore, impurities are easily generated during the process, affecting electrolyte performance; the conversion rate is low, making it difficult to obtain high-concentration electrolytes; and the reducing gases SO2 are toxic, while H2 is flammable and explosive, posing significant safety risks.

[0005] Electrolysis typically employs a two-chamber electrolytic cell with a diaphragm, using constant current or constant voltage for electrolysis. A reduction reaction occurs at the cathode, while the opposite occurs at the anode. Several electrolysis methods are possible: both the anode and cathode can contain tetravalent vanadium ions, yielding a pentavalent vanadium ion electrolyte at the anode and a trivalent vanadium ion electrolyte at the cathode; alternatively, the anode can be a sulfuric acid solution and the cathode a compound containing high-valent vanadium ions, respectively. After heating and activation, electrolysis can be performed, yielding tetravalent, trivalent, and divalent vanadium electrolytes by controlling the electrolysis time. Electrolysis produces no impurities and has low processing costs, but it consumes a large amount of electrical energy and has a relatively slow electrolysis rate. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of slow electrolysis rate and high energy consumption in the electrolytic preparation of vanadium redox flow battery electrolyte in the prior art, and to provide a method for electrolytic preparation of vanadium redox flow battery electrolyte. This method can effectively improve the electrolysis rate and effectively reduce the energy consumption in the electrolysis process, thereby reducing the production cost of vanadium redox flow electrolyte.

[0007] To achieve the above objectives, the present invention provides a method for preparing an all-vanadium redox flow battery electrolyte by electrolysis, the method comprising: adding a catalyst to a cathode electrolyte; wherein the catalyst contains modified nano-carbon, and the modified nano-carbon is carboxylated nano-carbon and / or hydroxylated nano-carbon.

[0008] Preferably, the amount of catalyst added is 0.5-2g relative to 1L of cathode electrolyte.

[0009] Preferably, the modified nanocarbon is carboxylated nanocarbon or hydroxylated nanocarbon.

[0010] More preferably, the mass ratio of the carboxylated nanocarbon to the hydroxylated nanocarbon is 1:2-4.

[0011] More preferably, the carboxylated carbon nanotubes are selected from at least one of carboxylated carbon nanotubes, carboxylated graphene, and carboxylated carbon black; the hydroxylated carbon nanotubes are selected from at least one of hydroxylated carbon nanotubes, hydroxylated graphene, and hydroxylated carbon black.

[0012] Preferably, the catalyst further contains polyvinylpyrrolidone (PVP).

[0013] More preferably, the mass ratio of the PVP to the modified nano-carbon is 1:0.5-2.

[0014] Preferably, the method for preparing the cathode electrolyte includes: activating V2O5 and sulfuric acid by mixing, and then mixing with an aqueous solvent to obtain the cathode electrolyte, wherein the aqueous solvent is water or a sulfuric acid solution.

[0015] More preferably, the activation conditions include at least a temperature of 60-90°C.

[0016] More preferably, in the mixing and activation step, the molar ratio of V2O5 to sulfuric acid is 1:2-4.

[0017] More preferably, the concentration of V2O5 in the cathode electrolyte is 0.2-0.8 mol.

[0018] More preferably, the method further includes dispersing the catalyst in the cathode electrolyte.

[0019] More preferably, the method for dispersing the catalyst in the cathode electrolyte includes: stirring and ultrasonicating the cathode electrolyte containing the catalyst.

[0020] Preferably, the conditions for the stirring treatment include at least: a stirring rate of 200-400 rad / min and a time of 1-2 h; the conditions for the ultrasonic treatment include at least: an ultrasonic power of 200-500 W and a time of 1-2 h.

[0021] Preferably, the method employs constant current electrolysis, wherein the constant current electrolysis current density is 20-120 mA / cm². 2 .

[0022] Preferably, the anolyte is a sulfuric acid solution.

[0023] More preferably, the concentration of the sulfuric acid solution is 2-4M.

[0024] By using the above technical solution, adding carboxylated nano-carbon and / or hydroxylated nano-carbon as catalysts to the cathode electrolyte can effectively improve the electrolysis rate and reduce energy consumption during the electrolysis process, thereby reducing the production cost of the all-vanadium liquid flow electrolyte. Attached Figure Description

[0025] Figure 1 The ultraviolet absorbance of the electrolyte (diluted to 0.1M) prepared in Example 9 and Comparative Example 1 of the present invention and 0.1M VOSO4 are shown, where A is 0.1M VOSO4, B is the electrolyte prepared in Comparative Example 1 (diluted to 0.1M), and C is the electrolyte prepared in Example 9 (diluted to 0.1M).

[0026] Figure 2 The graph shows the average conversion rate changes of Example 9 and Comparative Example 1 of the present invention, where A is Comparative Example 1 and B is Example 9;

[0027] Figure 3 The average power variation of Embodiment 9 and Comparative Example 1 of the present invention is shown, where A is Comparative Example 1 and B is Embodiment 9;

[0028] Figure 4 The graph shows the average conversion rate changes of Example 6 and Comparative Example 3 of the present invention, where A is Comparative Example 3 and B is Example 6;

[0029] Figure 5 The figures show the cyclic voltammetric characteristic curves of Example 6 and Comparative Example 3 of the present invention, where A is the electrolyte of Example 6 after filtration, B is the electrolyte of Example 6 without filtration, and C is the electrolyte of Comparative Example 3 without filtration. Detailed Implementation

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] As mentioned above, the present invention provides a method for preparing an all-vanadium redox flow battery electrolyte by electrolysis, the method comprising: adding a catalyst to a cathode electrolyte; wherein the catalyst contains modified nano-carbon, and the modified nano-carbon is carboxylated nano-carbon and / or hydroxylated nano-carbon.

[0032] During their research, the inventors unexpectedly discovered that adding carboxylated and / or hydroxylated nanocarbon nanoparticles as catalysts to the cathode electrolyte can effectively improve the electrolysis rate and reduce energy consumption during the electrolysis process, thereby reducing the production cost of the all-vanadium liquid flow electrolyte.

[0033] Preferably, the amount of catalyst added relative to 1L of cathode electrolyte is 0.4-3g, specifically 0.4g, 1g, 1.5g, 2g, 2.5g, 3g, or any value between these values. More preferably, it is 0.5-2g. Controlling the amount of catalyst added within the above range can effectively improve the electrolysis rate and reduce electrolysis energy consumption while reducing the amount of catalyst used, further reducing the cost of preparing the electrolyte for vanadium redox flow batteries.

[0034] The modified nano-carbon can be carboxylated nano-carbon alone, hydroxylated nano-carbon alone, or a mixture of carboxylated and hydroxylated nano-carbon. To further improve the electrolysis rate and reduce electrolysis energy consumption, preferably, the modified nano-carbon is a mixture of carboxylated and hydroxylated nano-carbon. Further preferably, considering further improving the electrolysis rate and reducing electrolysis energy consumption, the mass ratio of the carboxylated nano-carbon to the hydroxylated nano-carbon is 1:2-4, specifically 1:2, 1:2.5, 1:3, 1:3.5, 1:4, or any value between these values.

[0035] Preferably, the carboxylated carbon nanotubes are selected from at least one of carboxylated carbon nanotubes, carboxylated graphene, and carboxylated carbon black; the hydroxylated carbon nanotubes are selected from at least one of hydroxylated carbon nanotubes, hydroxylated graphene, and hydroxylated carbon black. Using the above-mentioned carboxylated and hydroxylated carbon nanotubes can further improve the electrolysis rate and reduce electrolysis energy consumption.

[0036] Preferably, the catalyst further contains PVP. PVP can enhance the stability of modified nano-carbon, and in synergy with it, can further improve the electrolysis rate and reduce electrolysis energy consumption. Further preferably, considering the need to further improve the electrolysis rate and reduce electrolysis energy consumption, the mass ratio of PVP to modified nano-carbon is 1:0.5-2, specifically 1:0.5, 1:1, 1:1.5, 1:2, or any value between these values.

[0037] Preferably, the method for preparing the cathode electrolyte includes: activating V₂O₅ with sulfuric acid, and then mixing it with an aqueous solvent to obtain the cathode electrolyte. The aqueous solvent is water or an aqueous sulfuric acid solution, preferably an aqueous sulfuric acid solution. The concentration of the aqueous sulfuric acid solution is not particularly limited, as long as the concentration of sulfuric acid in the obtained cathode electrolyte is 2-4 M. This method enables as much V₂O₅ as possible to be converted into free pentavalent vanadium ions. To further improve the conversion rate of V₂O₅ to free pentavalent vanadium ions, more preferably, the activation conditions include at least a temperature of 60-90°C, specifically 60°C, 70°C, 80°C, 90°C, or any value between these values.

[0038] According to the present invention, the sulfuric acid used in the mixed activation process is concentrated sulfuric acid, and the concentration of the concentrated sulfuric acid can be above 90% (by mass).

[0039] Preferably, in the mixing and activation step, the molar ratio of V₂O₅ to sulfuric acid is 1:2-4, specifically 1:2, 1:3, 1:4, or any value between these values. Controlling the mass ratio of V₂O₅ to sulfuric acid within the above range can further improve the conversion rate of V₂O₅ to free pentavalent vanadium ions. More preferably, the concentration of V₂O₅ in the cathode electrolyte is 0.2-0.8 mol / L.

[0040] Preferably, the method further includes dispersing the catalyst in the cathode electrolyte, which can further improve the electrolysis rate. As a specific embodiment of the present invention, the method for dispersing the catalyst in the cathode electrolyte is to subject the cathode electrolyte containing the catalyst to stirring and ultrasonic treatment. Preferably, the stirring conditions include at least: a stirring rate of 200-400 rad / min and a time of 1-2 h; the ultrasonic treatment conditions include at least: an ultrasonic power of 200-500 W and a time of 1-2 h.

[0041] Preferably, the method employs constant current electrolysis, wherein the constant current electrolysis current density is 20-120 mA / cm². 2 Under the above conditions, the electrolysis rate can be further increased.

[0042] Preferably, the anolyte is a sulfuric acid solution. To further improve electrolysis efficiency, the concentration of the sulfuric acid solution is preferably 2-4 M.

[0043] According to a particularly preferred embodiment of the present invention, a method for electrolytically preparing an all-vanadium redox flow battery electrolyte is provided.

[0044] (1) V2O5 and concentrated sulfuric acid are activated at a temperature of 60-90℃, and after cooling, they are mixed with dilute sulfuric acid to obtain a mixed solution containing pentavalent vanadium ions (the concentration of sulfuric acid is 2-4M); the catalyst is added to the mixed solution and stirred at a stirring rate of 200-400 rad / min for 1-2 h; then ultrasonicated under ultrasonic conditions of 200-500 W for 1-2 h to obtain the cathode electrolyte;

[0045] The amount of catalyst added relative to 1L of cathode electrolyte is 0.5-2g. The catalyst contains modified nano-carbon and PVP, and the mass ratio of PVP to modified nano-carbon is 1:0.5-2. The modified nano-carbon is carboxylated nano-carbon and hydroxylated nano-carbon, and the mass ratio of carboxylated nano-carbon to hydroxylated nano-carbon is 1:2-4.

[0046] (2) Using a 2-4M sulfuric acid solution as the anolyte, perform constant current electrolysis with stirring, controlling the current density to 20-120 mA / cm². 2 .

[0047] After the electrolyte is used, the catalyst can be separated from the electrolyte through solid-liquid separation, enabling the recycling of carbon catalysts and reducing costs. Solid-liquid separation can be achieved through methods such as filtration, gravity separation, or centrifugation.

[0048] The method provided by the above preferred embodiments can significantly improve the electrolysis rate and effectively reduce energy consumption during the electrolysis process, thereby reducing the production cost of vanadium liquid flow.

[0049] The present invention will be described in detail below through examples. In the following examples, the UV-Vis spectrophotometer was manufactured by Shimadzu, instrument number UV-2600; carboxylated multi-walled carbon nanotubes were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product number C295051; hydroxylated multi-walled carbon nanotubes were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product number C409346; hydroxylated carbon black was purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd., product number XFDZ66; carboxylated graphene was purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd., product number XF004; hydroxylated graphene was purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd., product number XF307; and PVP was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product number P110608.

[0050] Carboxylated carbon black was obtained by the following method, wherein the graphitized carbon black was purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd., product number XF080; and the hydrogen peroxide solution was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product number XF080H433856.

[0051] Add 150 mL of 30% hydrogen peroxide and 5 g of carbon black to a beaker and react at 25 °C for 96 h. After the reaction is complete, filter to obtain the reaction product. Wash the reaction product with deionized water until the pH of the washing solution is constant. Dry the reaction product in a vacuum oven at 120 °C and 0.3 kPa until constant mass (usually for 3 h), then seal and dry for later use.

[0052] Example 1

[0053] S1. Weigh 11.375g of V2O5 (99.5%) using a balance, add 12.5mL of concentrated sulfuric acid (98%), and activate by heating on an 80℃ heating plate. After cooling, dilute with 28.25mL of concentrated sulfuric acid and pour into a 250mL volumetric flask to make up to volume, yielding 0.5MV. 5+ A 3M sulfuric acid solution was used. Three 80mL portions of the solution were measured using a graduated cylinder and poured into different electrolytic cells as cathode electrolytes. The anode electrolyte was the same volume of 3M dilute sulfuric acid solution.

[0054] S2. Weigh 0.01g of carboxylated multi-walled carbon nanotubes (MWCNT-COOH), 0.03g of hydroxylated multi-walled carbon nanotubes, and 0.04g of PVP using a balance, and place them in a 0.5MV container. 5+ In a +3M sulfuric acid solution, the mixture was stirred and sonicated for 1 hour at a stirring rate of 400 rad / min and an ultrasonic power of 400 W.

[0055] S3. Perform constant current electrolysis on the prepared electrolyte while stirring, with the current density controlled at 20 mA / cm². 2 The stirring speed is 50 rad / min.

[0056] Example 2

[0057] S1. Weigh 4.625g of V₂O₅ (99.5%) using a balance, add 2.75mL of concentrated sulfuric acid (98%), and activate by heating on a 90℃ heating plate. After cooling, add another 24.5mL of concentrated sulfuric acid to dilute, then pour into a 250mL volumetric flask and make up to volume to obtain 0.2MV. 5+ A 2M sulfuric acid solution was used. Three 80mL portions of the solution were measured using a graduated cylinder and poured into different electrolytic cells as cathode electrolytes. The anode electrolyte was the same volume of 2M dilute sulfuric acid solution.

[0058] S2. Weigh 0.01g of carboxylated graphene, 0.02g of hydroxylated carbon black, and 0.015g of PVP using a balance, and place them in a 0.2MV container. 5+ In a +2M sulfuric acid solution, the mixture was stirred and sonicated for 1 hour at a stirring rate of 300 rad / min and an ultrasonic power of 500 W.

[0059] S3. Perform constant current electrolysis on the prepared electrolyte while stirring, with the current density controlled at 60 mA / cm². 2 The stirring speed is 50 rad / min.

[0060] Example 3

[0061] S1. Weigh 18.3g of V2O5 (99.5%) using a balance, add 27mL of concentrated sulfuric acid (98%), and activate by heating on a 60℃ heating plate. After cooling, add another 49mL of concentrated sulfuric acid to dilute, then pour into a 250mL volumetric flask and make up to volume to obtain 0.8MV. 5+ A 4M sulfuric acid solution was used to measure three 80mL portions, which were then poured into different electrolytic cells as cathode electrolytes. The anode electrolyte was the same volume of 4M dilute sulfuric acid solution.

[0062] S2. Weigh 0.011g of carboxylated carbon black, 0.044g of hydroxylated graphene, and 0.105g of PVP using a balance, and place them in a 0.8MV container. 5+ In a +5M sulfuric acid solution, the mixture was stirred and sonicated for 2 hours at a stirring rate of 200 rad / min and an ultrasonic power of 200 W.

[0063] S3. Perform constant current electrolysis on the prepared electrolyte while stirring, with the current density controlled at 120 mA / cm². 2 The stirring speed is 50 rad / min.

[0064] Example 4

[0065] The all-vanadium liquid electrolyte was prepared according to the method in Example 2, except that the amount of PVP added was 0.006 g.

[0066] Example 5

[0067] The all-vanadium liquid electrolyte was prepared according to the method in Example 3, except that the amount of PVP added was 0.165g.

[0068] Example 6

[0069] The all-vanadium liquid electrolyte was prepared according to the method in Example 3, except that the amount of PVP added was 0g.

[0070] Example 7

[0071] The all-vanadium liquid electrolyte was prepared according to the method in Example 1, except that the amount of carboxylated multi-walled carbon nanotubes (MWCNT-COOH) added was 0.02 g and the amount of hydroxylated multi-walled carbon nanotubes added was 0.02 g.

[0072] Example 8

[0073] The all-vanadium redox flow electrolyte was prepared according to the method in Example 3, except that the amount of carboxylated carbon black added was 0.009 g and the amount of hydroxylated graphene added was 0.046 g.

[0074] Example 9

[0075] The all-vanadium liquid electrolyte was prepared according to the method in Example 1, except that the amount of carboxylated multi-walled carbon nanotubes (MWCNT-COOH) added was 0.04 g and the amount of hydroxylated multi-walled carbon nanotubes added was 0 g.

[0076] Example 10

[0077] The all-vanadium liquid electrolyte was prepared according to the method in Example 1, except that the amount of carboxylated multi-walled carbon nanotubes (MWCNT-COOH) added was 0 g, and the amount of hydroxylated multi-walled carbon nanotubes added was 0.04 g.

[0078] Comparative Example 1

[0079] S1. Weigh 11.375g of V2O5 (99.5%) using a balance, add 12.5mL of concentrated sulfuric acid (98%), and activate by heating on an 80℃ heating plate. After cooling, dilute with 28.25mL of concentrated sulfuric acid and pour into a 250mL volumetric flask to make up to volume, yielding 0.5MV. 5+ A 3M sulfuric acid solution was used. Three 80mL portions of the solution were measured using a graduated cylinder and poured into different electrolytic cells as cathode electrolytes. The anode electrolyte was the same volume of 3M dilute sulfuric acid solution.

[0080] S2. The prepared electrolyte is subjected to constant current electrolysis with stirring, and the current density is controlled at 20 mA / cm². 2 The stirring speed is 50 rad / min.

[0081] Comparative Example 2

[0082] S1. Weigh 4.625g of V₂O₅ (99.5%) using a balance, add 2.75mL of concentrated sulfuric acid (98%), and activate by heating on a 90℃ heating plate. After cooling, add another 24.5mL of concentrated sulfuric acid to dilute, then pour into a 250mL volumetric flask and make up to volume to obtain 0.2MV. 5+ A 2M sulfuric acid solution was used. Three 80mL portions of the solution were measured using a graduated cylinder and poured into different electrolytic cells as cathode electrolytes. The anode electrolyte was the same volume of 2M dilute sulfuric acid solution.

[0083] S2. The prepared electrolyte is subjected to constant current electrolysis with stirring, and the current density is controlled at 60 mA / cm². 2 The stirring speed is 50 rad / min.

[0084] Comparative Example 3

[0085] S1. Weigh 18.3g of V2O5 (99.5%) using a balance, add 27mL of concentrated sulfuric acid (98%), and activate by heating on a 60℃ heating plate. After cooling, add another 49mL of concentrated sulfuric acid to dilute, then pour into a 250mL volumetric flask and make up to volume to obtain 0.8MV. 5+ A 4M sulfuric acid solution was used to measure three 80mL portions, which were then poured into different electrolytic cells as cathode electrolytes. The anode electrolyte was the same volume of 4M dilute sulfuric acid solution.

[0086] S2. The prepared electrolyte is subjected to constant current electrolysis with stirring, and the current density is controlled at 120 mA / cm². 2 The stirring speed is 50 rad / min.

[0087] Test Example 1

[0088] The electrolytes prepared in Example 9 and Comparative Example 1 were diluted to 0.1 M, and a 0.1 M VOSO4 solution was provided for UV absorbance measurement to obtain... Figure 1 ,Depend on Figure 1 It can be seen that the absorbance of the electrolyte obtained by adding nanoparticles and the absorbance of the electrolyte obtained by electrolysis without adding nanoparticles are basically the same as the absorbance of VOSO4, indicating that the electrolyte obtained by the present invention is actually a tetravalent vanadium electrolyte.

[0089] The conversion rate and power variations of all examples and comparative examples were statistically analyzed. The conversion rate was determined by sampling and testing the concentrations of tetravalent vanadium and total vanadium at equal time intervals, using the formula... Calculated, α is the conversion rate, C IV For tetravalent vanadium concentration, C 总 The total vanadium concentration was measured using a ZDJ-4A automatic potentiometric titrator from Shanghai Yifen Scientific Instruments Co., Ltd., with ferrous ammonium sulfate standard solution as the titrant and ferrous ammonium sulfate titration method (standard number: GB / T 8704.5-2020). Power changes were automatically recorded by a high-performance battery detection system, recording the voltage and current at the anode and cathode of the electrolytic cell during electrolysis. These changes were calculated using the formula P = UI. The high-performance battery detection system was a CT-4008Tn-5V / 12A-S1-F from Shenzhen Xinwei Electronics Co., Ltd. The average values ​​are shown in Table 1.

[0090] Table 1

[0091] Example 1 4.5 0.6785 Example 2 2 0.4686 Example 3 15 0.9528 Example 4 2.2 0.5126 Example 5 15.5 0.9579 Example 6 16 0.9626 Example 7 4.8 0.6790 Example 8 18 0.9765 Example 9 5 0.6801 Example 10 5.1 0.6801 Comparative Example 1 6 0.7089 Comparative Example 2 2.5 0.5674 Comparative Example 3 20 0.9874

[0092] As can be seen from the results in Table 1, in electrolytes with the same sulfuric acid concentration, compared with the comparative example, the examples with the addition of carbon nanoparticles and PVP or with the addition of carbon nanoparticles have a higher conversion rate in the same time and a lower power consumption to reach 100% conversion, showing significantly better performance.

[0093] Figure 2 This is a graph showing the conversion rate changes of Embodiment 9 and Comparative Example 1 of the present invention; Figure 3 This refers to the power variation in Embodiment 9 and Comparative Example 1 of the present invention; by Figure 2 and Figure 3 Yes, compared to Comparative Example 1, Example 9 showed an increase in electrolysis rate of 16.67% and a reduction in power consumption of 14.59%.

[0094] Depend on Figure 4 and Figure 5 It can be seen that, compared with Comparative Example 3 and Example 6, the electrolysis rate in Example 6 was increased by 20%, the peak current density was significantly increased, and the peak potential difference was significantly reduced, indicating that the electrochemical activity and electrochemical reversibility were improved compared with the comparative example.

[0095] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for electrolytically preparing an all-vanadium redox flow battery electrolyte, characterized in that, The method includes: adding a catalyst to the cathode electrolyte; The catalyst contains modified nano-carbon, which is carboxylated nano-carbon and / or hydroxylated nano-carbon.

2. The method according to claim 1, characterized in that, The amount of catalyst added is 0.5-2g relative to 1L of cathode electrolyte.

3. The method according to claim 1 or 2, characterized in that, The modified nanocarbon is carboxylated nanocarbon and hydroxylated nanocarbon.

4. The method according to claim 3, characterized in that, The mass ratio of the carboxylated nanocarbon to the hydroxylated nanocarbon is 1:2-4.

5. The method according to claim 4, characterized in that, The carboxylated carbon nanotubes are selected from at least one of carboxylated carbon nanotubes, carboxylated graphene, and carboxylated carbon black. The hydroxylated carbon nanotubes are selected from at least one of hydroxylated carbon nanotubes, hydroxylated graphene, and hydroxylated carbon black.

6. The method according to claim 1 or 2, characterized in that, The catalyst also contains polyvinylpyrrolidone.

7. The method according to claim 6, characterized in that, The mass ratio of the polyvinylpyrrolidone to the modified nano-carbon is 1:0.5-2.

8. The method according to claim 1 or 2, characterized in that, The method for preparing the cathode electrolyte includes: activating V2O5 and sulfuric acid by mixing, and then mixing with an aqueous solvent to obtain the cathode electrolyte, wherein the aqueous solvent is water or a sulfuric acid solution.

9. The method according to claim 8, characterized in that, The activation conditions include at least the following: a temperature of 60-90°C.

10. The method according to claim 9, characterized in that, In the mixed activation step, the molar ratio of V2O5 to sulfuric acid is 1:2-4.

11. The method according to claim 10, characterized in that, The concentration of V2O5 in the cathode electrolyte is 0.2-0.8 mol / L.

12. The method according to claim 1 or 2, characterized in that, The method further includes dispersing the catalyst in the cathode electrolyte.

13. The method according to claim 12, characterized in that, The method for dispersing the catalyst in the cathode electrolyte includes: stirring and ultrasonicating the cathode electrolyte to which the catalyst is added.

14. The method according to claim 13, characterized in that, The conditions for the stirring treatment include at least the following: a stirring rate of 200-400 rad / min and a time of 1-2 h. The conditions for ultrasonic treatment include at least: ultrasonic power of 200-500W and time of 1-2h.

15. The method according to claim 1 or 2, characterized in that, The method employs constant current electrolysis, with a constant current electrolysis current density of 20-120 mA / cm². 2 .

16. The method according to claim 1 or 2, characterized in that, The anolyte is a sulfuric acid solution.

17. The method according to claim 16, characterized in that, The concentration of the sulfuric acid solution is 2-4M.

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