Mixed acid-based electrolyte, preparation method and application thereof

Abstract

The application relates to the technical field of all-vanadium redox flow batteries, and discloses a mixed acid-based electrolyte as well as a preparation method and application thereof, at least comprising the following steps: preparing a sulfuric acid-based vanadium electrolyte by adopting a chemical reduction-electrolysis method, pouring the sulfuric acid-based vanadium electrolyte into a rotating container of a rotary evaporator, performing a rotary evaporation operation, obtaining a sulfuric acid-based vanadium concentrated solution, adding a barium chloride solution into the sulfuric acid-based vanadium concentrated solution, fully stirring, obtaining a sulfuric acid-based vanadium crude solution, filtering the sulfuric acid-based vanadium crude solution by adopting a microporous filter membrane, the filtrate being a sulfuric acid-based vanadium concentrated solution, further adding deionized water into the sulfuric acid-based vanadium concentrated solution, diluting the concentrated solution, and adjusting the concentrated solution to obtain a final mixed acid-based vanadium electrolyte, which has the advantages of high energy density, wide use temperature and good vanadium stability, and can avoid the problems of difficult accurate control of hydrochloric acid concentration and environmental pollution caused by volatilization and chlorine precipitation of hydrochloric acid during electrolysis by adopting a conventional method.

Description

Technical Field

[0001] This invention relates to the field of vanadium redox flow battery electrolyte technology, and in particular to a mixed acid-based electrolyte, its preparation method, and its application. Background Technology

[0002] A vanadium redox flow battery (VRFB) is an energy storage battery based on the redox reaction of vanadium ions, utilizing vanadium ions in different valence states (V0, V ...). 2+ / V 3+ and VO 2+ / VO2 + The reversible reaction in the electrolyte enables energy storage and release, offering advantages such as high energy conversion efficiency, long cycle life, convenient capacity adjustment, intrinsic safety, and environmental friendliness. It can be used in large-scale energy storage applications, including renewable energy sources like solar and wind power, and grid peak shaving and valley filling, making it one of the most promising energy storage devices. The electrolyte, as the carrier of active materials, is one of the most crucial components of a vanadium redox flow battery (vanadium redox flow battery). It is the energy module of the vanadium battery system, and its performance and concentration directly affect the battery's performance and energy density. Commonly used vanadium battery electrolytes are sulfuric acid-based electrolytes, with a typical operating temperature range of 5–40°C. Exceeding this temperature limit leads to vanadium ion precipitation, causing irreversible damage to the battery system. Furthermore, the vanadium concentration in sulfuric acid-based electrolytes is generally low, making it difficult to increase the battery's energy density.

[0003] In recent years, mixed acid systems combining hydrochloric acid and sulfuric acid have gradually replaced the pure sulfuric acid system as the energy storage medium for all-vanadium redox flow batteries with supporting electrolytes. This system has advantages such as high energy density and a wide operating temperature range (-20 to 50°C). Currently, the preparation methods for this mixed acid system are similar to those for the sulfuric acid system, mainly employing chemical reduction or electrolysis methods. The chemical method primarily uses high-valence vanadium oxides or vanadates as raw materials, heating them in a sulfuric acid or hydrochloric acid solution of a certain concentration while adding reducing agents (such as H2, CH4, S, SO2, etc.) to dissolve and reduce them, thus preparing a sulfate-hydrochloric acid-based vanadium electrolyte. The advantage of the chemical synthesis method is the simplicity of the production equipment, but the solid dissolution rate is slow, and the added reducing agents remain in the vanadium electrolyte and are difficult to remove, affecting the purity and performance of the vanadium electrolyte. Electrolysis typically employs a diaphragm-equipped electrolytic cell. Vanadium-containing raw materials such as V₂O₅ or metavanadate are used. A sulfuric acid / hydrochloric acid solution containing V₂O₅ or metavanadate is added to the negative electrode region, while the same concentration of sulfuric acid / hydrochloric acid is added to the positive electrode region. An appropriate direct current is applied to both electrodes, causing the V₂O₅ or metavanadate to be reduced on the negative electrode surface, thus producing a sulfate-hydrochloric acid-based vanadium electrolyte. Electrolysis has gradually gained acceptance and adoption in the preparation of vanadium electrolytes in sulfuric acid systems. However, in mixed acid systems of sulfuric acid and hydrochloric acid, problems arise such as difficulty in accurately controlling the hydrochloric acid concentration due to volatilization and chlorine evolution during electrolysis, as well as environmental pollution. Therefore, there is a need to develop a low-cost, high-performance method for preparing a sulfate-hydrochloric acid-based electrolyte for all-vanadium redox flow batteries. Summary of the Invention

[0004] The purpose of this invention is to provide a mixed acid-based electrolyte, its preparation method, and its application, thereby overcoming the shortcomings of the prior art.

[0005] The technical solution adopted in this invention is as follows:

[0006] In a first aspect, a method for preparing a mixed acid-based electrolyte is disclosed, comprising the following steps:

[0007] Step S1: Prepare a vanadium sulfate-based electrolyte with known vanadium ion concentration and sulfuric acid concentration;

[0008] Step S2: Place the vanadium sulfate electrolyte in a rotary evaporator and perform rotary evaporation according to the set heat preservation temperature and circulating cooling liquid temperature to obtain vanadium sulfate concentrate;

[0009] Step S3: Add barium chloride solution to the vanadium sulfate concentrate and stir thoroughly to obtain crude vanadium sulfate hydrochloride solution;

[0010] Step S4: Filter the crude vanadium sulfate hydrochloride solution using a microporous membrane, collect the filtrate, and obtain a concentrated vanadium sulfate hydrochloride solution.

[0011] Step S5: Add deionized water to the vanadium sulfate hydrochloride concentrate to dilute the concentrate and obtain a mixed acid vanadium electrolyte.

[0012] In one implementation, in step S1:

[0013] The vanadium ion concentration is 1.5~2.5 mol / L;

[0014] The sulfuric acid concentration is 3~5 mol / L;

[0015] The average valence state of vanadium ions in the vanadium sulfate-based electrolyte is 3.5.

[0016] A vanadium sulfate-based electrolyte with a certain vanadium concentration and a certain sulfuric acid concentration is prepared using conventional methods. If the vanadium concentration is too high, the dissolution will be slow, and if the concentration is too low, the energy density will be low. If the sulfuric acid concentration is too high, the electrolyte viscosity will be too high, which will affect the voltage efficiency. If the concentration is too low, it will be difficult to dissolve the vanadium-containing raw materials.

[0017] In one implementation, in step S2:

[0018] The insulation temperature is 50~80℃;

[0019] The temperature of the circulating coolant is 0~10℃.

[0020] The vanadium sulfate electrolyte is poured into a rotary evaporator. Under the negative pressure and low temperature environment of the rotary evaporator, the water in the vanadium sulfate electrolyte evaporates, achieving a simultaneous increase in vanadium concentration and acid concentration. In this way, there is no risk of vanadium precipitation. The principle is as shown in equation (1):

[0021] VO 2+ +H2O VO(OH)2+H + (1)

[0022] Tetravalent vanadium (VO₂) 2+ It can also hydrolyze to form hydroxide complexes, which may further form insoluble hydrated vanadium dioxide (VO(OH)2). If the hydrogen ion concentration increases unilaterally, vanadium will be precipitated.

[0023] In one implementation, in step S3:

[0024] The concentration of the barium chloride solution is 0.5~1.5 mol / L;

[0025] The barium chloride used was of analytical grade.

[0026] Adding barium chloride solution to the vanadium sulfate concentrate causes the barium chloride to react with the sulfate ions in the concentrate (reaction equation as shown in equation (2)), generating an insoluble barium sulfate precipitate. This reduces the sulfate concentration while introducing chloride ions, and keeps the hydrogen ion concentration constant, meaning the vanadium concentration and acid concentration remain unchanged. This step is crucial because by controlling the amount of barium chloride added, the hydrochloric acid concentration can be adjusted, which in turn adjusts the ratio of vanadium, sulfuric acid, and hydrochloric acid.

[0027] H2SO4+BaCl2→BaSO4↓+2HCl (2)

[0028] In one embodiment, in step S3: the sum of the volumes of the vanadium sulfate concentrate and the barium chloride solution is equal to the volume of the vanadium sulfate electrolyte.

[0029] In one implementation, in step S4:

[0030] The microporous filter membrane is one of polyethylene membrane, polypropylene membrane, polyethersulfone membrane, polyvinylidene fluoride membrane, polytetrafluoroethylene membrane, polyacrylonitrile membrane, and polyamide membrane;

[0031] The microporous filter membrane has a pore size of 0.2~2μm and a thickness of 100~200μm.

[0032] A microporous membrane was used to filter the crude vanadium sulfate hydrochloride solution containing barium sulfate precipitate. After filtration, the filtrate was a concentrated vanadium sulfate hydrochloride solution. The barium sulfate precipitate was intercepted by the membrane and formed a filter cake, which entered a simple recycling and regeneration stage (the regeneration principle is shown in equations (3) and (4)). Finally, barium chloride was generated and recycled.

[0033] BaSO4+NaCO3→BaCO3+Na2SO4 (3)

[0034] BaCO3+2HCl→BaCl2+H2O+CO2 (4)

[0035] Secondly, a mixed acid-based vanadium electrolyte is disclosed, which is prepared by the above-mentioned method for preparing mixed acid-based vanadium electrolyte.

[0036] Thirdly, an application of a mixed acid-based vanadium electrolyte is disclosed, wherein the mixed acid-based vanadium electrolyte prepared by the above-described preparation method or the mixed acid-based vanadium electrolyte described above is applied to an all-vanadium redox flow battery.

[0037] The beneficial effects of the present invention include at least the following:

[0038] 1. The sulfuric acid-based electrolyte required in the first step of this invention does not require a high vanadium concentration. A stable high-concentration sulfuric acid-based vanadium electrolyte can be formed through subsequent rotary evaporation treatment, which skips the problem of slow dissolution rate of vanadium-containing raw materials and is beneficial to improving the energy density of the battery.

[0039] 2. This invention first prepares a sulfuric acid-based electrolyte, then concentrates it by rotary evaporation, adds barium chloride for filtration, and then adjusts it into a mixed acid-based vanadium electrolyte. This avoids the problems of difficult-to-control hydrochloric acid concentration and environmental pollution caused by hydrochloric acid volatilization and chlorine evolution during electrolysis, as well as potential safety issues, that arise from conventional methods (first preparing a sulfuric acid-hydrochloric acid-based mixed acid electrolyte, then dissolving vanadium-containing raw materials, and then electrolyzing and reducing them).

[0040] 3. The preparation process of this invention is simple and low-cost, and the additional raw material barium chloride can be recycled. Attached Figure Description

[0041] Figure 1 This is a flowchart of a method for preparing a mixed acid-based electrolyte according to the present invention. Detailed Implementation

[0042] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0043] like Figure 1 As shown, a vanadium sulfate electrolyte with a vanadium concentration of 1.5-2.5 mol / L and a sulfuric acid concentration of 3-5 mol / L was prepared by chemical reduction-electrolysis. A volume V1 of the vanadium sulfate electrolyte was poured into the rotating container of a rotary evaporator. The container temperature was set to 50-80℃ and the circulating coolant temperature to 0-10℃. Rotary evaporation was performed to obtain a vanadium sulfate concentrate with a volume V2. A barium chloride solution with a volume V3 and a concentration of 0.5-1.5 mol / L was added to the vanadium sulfate concentrate and stirred thoroughly to obtain a crude vanadium sulfate hydrochloride solution. The crude vanadium sulfate hydrochloride solution was filtered using a microporous membrane with a pore size of 0.2-2 μm and a thickness of 100-200 μm. The filtrate was the vanadium sulfate hydrochloride concentrate. A volume V4 of deionized water was then added to the vanadium sulfate hydrochloride concentrate to dilute the concentrate, and the final mixed acid vanadium electrolyte was obtained.

[0044] The formula for calculating the vanadium concentration C1 in the final mixed acid-based vanadium electrolyte is as follows:

[0045] ;

[0046] In the formula, C VThis represents the vanadium concentration in the vanadium sulfate-based electrolyte.

[0047] The formula for calculating the sulfuric acid concentration C2 in the final mixed acid vanadium electrolyte is as follows:

[0048] ;

[0049] In the formula, C S C represents the sulfuric acid concentration in the vanadium sulfate electrolyte. B This represents the concentration of the barium chloride solution.

[0050] The formula for calculating the hydrochloric acid concentration C3 in the final mixed acid-based vanadium electrolyte is as follows:

[0051] .

[0052] In the following examples and comparative examples, V1 is 1L.

[0053] Example 1: The following technical solution is adopted.

[0054] A vanadium sulfate electrolyte with a vanadium concentration of 1.5 mol / L and a sulfuric acid concentration of 3 mol / L was prepared by chemical reduction-electrolysis. A 1 L volume of the vanadium sulfate electrolyte was poured into the rotating container of a rotary evaporator. The container was kept at 50 °C and the circulating coolant temperature was 0 °C. Rotary evaporation was performed to obtain a 0.65 L volume of concentrated vanadium sulfate. A 0.05 L volume of 0.5 mol / L barium chloride solution was added to the concentrated vanadium sulfate solution, and the mixture was stirred thoroughly to obtain a crude vanadium sulfate hydrochloride solution. The crude vanadium sulfate hydrochloride solution was filtered through a microporous membrane with a pore size of 0.2 μm and a thickness of 100 μm. The filtrate was the concentrated vanadium sulfate hydrochloride solution. 0.02 L volume of deionized water was then added to the concentrated vanadium sulfate hydrochloride solution to dilute it, thus preparing the final mixed acid vanadium electrolyte. In this mixed acid-based vanadium electrolyte, the vanadium concentration is 2.08 mol / L, the sulfuric acid concentration is 4.13 mol / L, and the hydrochloric acid concentration is 0.069 mol / L.

[0055] Example 2: The following technical solution is adopted.

[0056] A vanadium sulfate-based electrolyte with a vanadium concentration of 1.5 mol / L and a sulfuric acid concentration of 3.5 mol / L was prepared using a chemical reduction-electrolysis method. A 1 L volume of the vanadium sulfate-based electrolyte was poured into the rotating container of a rotary evaporator. The container was kept at a temperature of 60 °C and the circulating coolant temperature was 5 °C. Rotary evaporation was performed to obtain a 0.65 L volume of concentrated vanadium sulfate. A 0.05 L volume of 0.8 mol / L barium chloride solution was added to the concentrated vanadium sulfate and stirred thoroughly to obtain a crude vanadium sulfate-hydrochloride solution. This crude solution was filtered through a microporous membrane with a pore size of 0.5 μm and a thickness of 120 μm. The filtrate was the concentrated vanadium sulfate-hydrochloride solution. 0.01 L volume of deionized water was then added to the concentrated vanadium sulfate-hydrochloride solution to dilute it, thus preparing the final mixed acid vanadium electrolyte. In this mixed acid-based vanadium electrolyte, the vanadium concentration is 2.11 mol / L, the sulfuric acid concentration is 4.87 mol / L, and the hydrochloric acid concentration is 0.113 mol / L.

[0057] Example 3: The following technical solution is adopted.

[0058] A vanadium sulfate electrolyte with a vanadium concentration of 2 mol / L and a sulfuric acid concentration of 4 mol / L was prepared by chemical reduction-electrolysis. A 1 L volume of the vanadium sulfate electrolyte was poured into the rotating container of a rotary evaporator. The container was kept at 70 °C and the circulating coolant temperature was 5 °C. Rotary evaporation was performed to obtain a 0.6 L volume of concentrated vanadium sulfate. A 0.1 L volume of 1 mol / L barium chloride solution was added to the concentrated vanadium sulfate solution, and the mixture was stirred thoroughly to obtain a crude vanadium sulfate hydrochloride solution. The crude vanadium sulfate hydrochloride solution was filtered through a microporous membrane with a pore size of 1 μm and a thickness of 150 μm. The filtrate was the concentrated vanadium sulfate hydrochloride solution. 0.1 L volume of deionized water was then added to the concentrated vanadium sulfate hydrochloride solution to dilute it, thus preparing the final mixed acid vanadium electrolyte. In this mixed acid-based vanadium electrolyte, the vanadium concentration is 2.5 mol / L, the sulfuric acid concentration is 4.88 mol / L, and the hydrochloric acid concentration is 0.25 mol / L.

[0059] Example 4: The following technical solution is adopted.

[0060] A vanadium sulfate-based electrolyte with a vanadium concentration of 2 mol / L and a sulfuric acid concentration of 4.5 mol / L was prepared using a chemical reduction-electrolysis method. A 1 L volume of the vanadium sulfate-based electrolyte was poured into the rotating container of a rotary evaporator. The container temperature was set to 75 °C and the circulating coolant temperature to 10 °C, and rotary evaporation was performed to obtain a 0.55 L volume of concentrated vanadium sulfate. A 0.4 L volume of 1.1 mol / L barium chloride solution was added to the concentrated vanadium sulfate and stirred thoroughly to obtain a crude vanadium sulfate-hydrochloride solution. This crude solution was filtered through a microporous membrane with a pore size of 1.5 μm and a thickness of 180 μm. The filtrate was the concentrated vanadium sulfate-hydrochloride solution. 0.1 L volume of deionized water was then added to the concentrated vanadium sulfate-hydrochloride solution to dilute it, thus preparing the final mixed acid vanadium electrolyte. In this mixed acid-based vanadium electrolyte, the vanadium concentration is 1.9 mol / L, the sulfuric acid concentration is 3.9 mol / L, and the hydrochloric acid concentration is 0.84 mol / L.

[0061] Example 5: The following technical solution is adopted.

[0062] A vanadium sulfate-based electrolyte with a vanadium concentration of 2.5 mol / L and a sulfuric acid concentration of 5 mol / L was prepared using a chemical reduction-electrolysis method. A 1 L volume of the vanadium sulfate-based electrolyte was poured into the rotating container of a rotary evaporator. The container temperature was set to 80 °C and the circulating coolant temperature to 10 °C, and rotary evaporation was performed to obtain a 0.55 L volume of concentrated vanadium sulfate. A 0.4 L volume of 1.5 mol / L barium chloride solution was added to the concentrated vanadium sulfate and stirred thoroughly to obtain a crude vanadium sulfate-hydrochloride solution. This crude solution was filtered using a microporous membrane with a pore size of 2 μm and a thickness of 200 μm. The filtrate was the concentrated vanadium sulfate-hydrochloride solution. 0.2 L volume of deionized water was then added to the concentrated vanadium sulfate-hydrochloride solution to dilute it, thus preparing the final mixed acid vanadium electrolyte. In this mixed acid-based vanadium electrolyte, the vanadium concentration is 1.74 mol / L, the sulfuric acid concentration is 3.8 mol / L, and the hydrochloric acid concentration is 1.04 mol / L.

[0063] Comparative Example 1: The following technical solution is adopted.

[0064] The preparation process is the same as in Example 3, except that step S2 is omitted.

[0065] A vanadium sulfate-based electrolyte with a vanadium concentration of 2 mol / L and a sulfuric acid concentration of 4 mol / L was prepared using a chemical reduction-electrolysis method. 0.1 L of a 1 mol / L barium chloride solution was added to 1 L of the vanadium sulfate-based electrolyte, and the mixture was stirred thoroughly to obtain a crude vanadium sulfate-hydrochloride solution. This crude solution was filtered through a microporous membrane with a pore size of 1 μm and a thickness of 150 μm, yielding a concentrated vanadium sulfate-hydrochloride solution. 0.1 L of deionized water was then added to the concentrated solution to dilute it, thus preparing the final mixed-acid vanadium electrolyte. In this mixed-acid vanadium electrolyte, the vanadium concentration was 1.67 mol / L, the sulfuric acid concentration was 3.25 mol / L, and the hydrochloric acid concentration was 0.167 mol / L.

[0066] Comparative Example 2: The following technical solution is adopted.

[0067] The preparation process is the same as in Example 3, except that barium chloride in step S3 is replaced with hydrochloric acid.

[0068] A vanadium sulfate electrolyte with a vanadium concentration of 2 mol / L and a sulfuric acid concentration of 4 mol / L was prepared by chemical reduction-electrolysis. A 1 L volume of the vanadium sulfate electrolyte was poured into the rotating container of a rotary evaporator. The container was kept at 70 °C and the circulating coolant temperature was 5 °C. Rotary evaporation was performed to obtain a 0.6 L volume of concentrated vanadium sulfate. A 0.1 L volume of 1 mol / L hydrochloric acid solution was added to the concentrated vanadium sulfate and stirred thoroughly to obtain a crude vanadium sulfate hydrochloride solution. The crude vanadium sulfate hydrochloride solution was filtered through a microporous membrane with a pore size of 1 μm and a thickness of 150 μm. The filtrate was the concentrated vanadium sulfate hydrochloride solution. Then, 0.1 L volume of deionized water was added to the concentrated vanadium sulfate hydrochloride solution to dilute it, thus preparing the final mixed acid vanadium electrolyte. In this mixed acid-based vanadium electrolyte, the vanadium concentration is 2.5 mol / L, the sulfuric acid concentration is 5 mol / L, and the hydrochloric acid concentration is 0.25 mol / L.

[0069] The vanadium ion concentration, sulfuric acid concentration, and hydrochloric acid concentration of the mixed acid-based vanadium electrolytes prepared in Examples 1-5 and Comparative Examples 1-2 are listed in Table 1.

[0070] Table 1. Physical property parameters of mixed acid-based vanadium electrolyte

[0071]

[0072] The mixed-acid vanadium electrolytes prepared in Examples 1-5 and Comparative Examples 1-2 were tested on a fuel cell stack. Coulombic efficiency, voltage efficiency, and energy efficiency were tested and recorded under the same test conditions. The test results are shown in Table 2.

[0073] Table 2 Battery Performance Test Table for Mixed Acid Vanadium Electrolyte

[0074]

[0075] In the test results above, after rotary evaporation concentration in Examples 1-5, the vanadium and sulfate concentrations increased. The subsequent addition of barium chloride solution and filtration introduced chloride ions, i.e., hydrochloric acid components. This improved the stability of the high-concentration vanadium electrolyte, increased vanadium utilization, and improved battery energy density. Due to the increased acid concentration, the electrolyte conductivity also increased, and the ohmic polarization decreased, resulting in higher voltage efficiency. In contrast, Comparative Example 1 did not undergo rotary evaporation treatment; barium chloride was directly added to the sulfate-based electrolyte, leading to electrolyte dilution and a simultaneous decrease in vanadium and sulfate concentrations. This resulted in lower battery energy density, lower acid concentration, and lower conductivity, manifested as lower voltage efficiency. In Comparative Example 2, barium chloride was replaced with hydrochloric acid. Although hydrochloric acid components were introduced, the sulfate concentration in the vanadium concentrate could not be adjusted, resulting in a higher sulfate concentration and viscosity in the final electrolyte. This, in turn, increased electrolyte flow resistance and pump consumption, resulting in lower voltage and energy efficiency.

[0076] In summary, the preparation method of this invention involves rotary evaporation of a low-to-medium concentration vanadium sulfate electrolyte, causing the water in the electrolyte to evaporate and simultaneously increasing the vanadium and acid concentrations. This eliminates the risk of vanadium precipitation, overcomes the problem of slow dissolution of vanadium-containing raw materials, and is also beneficial for improving battery energy density. The reaction of barium chloride with sulfate ions in the concentrated solution generates insoluble barium sulfate precipitate, reducing the sulfate concentration while introducing chloride ions (through hydrochloric acid) and maintaining a constant hydrogen ion concentration, thus keeping the vanadium and acid concentrations constant. By controlling the amount of barium chloride added, the hydrochloric acid concentration can be adjusted, thereby controlling the ratio of vanadium, sulfuric acid, and hydrochloric acid. Therefore, the prepared mixed-acid vanadium electrolyte has high energy density, a wide operating temperature range, and good vanadium stability.

[0077] This invention first prepares a sulfuric acid-based electrolyte, then concentrates it by rotary evaporation, adds barium chloride for filtration, and then adjusts it into a vanadium sulfate-hydrochloride-based electrolyte. This avoids the problems of difficult-to-control hydrochloric acid concentration and environmental pollution caused by hydrochloric acid volatilization and chlorine evolution during electrolysis, as well as potential safety issues, that arise from conventional methods (first preparing a mixed acid electrolyte based on sulfuric acid and hydrochloric acid, then dissolving vanadium-containing raw materials, and then electrolyzing and reducing). The preparation process is simple, low-cost, and the additional raw material, barium chloride, can be recycled.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a mixed acid-based vanadium electrolyte, characterized in that, The preparation method includes the following steps: Step S1: Prepare a vanadium sulfate-based electrolyte with known vanadium ion concentration and sulfuric acid concentration; wherein the vanadium ion concentration is 1.5~2.5 mol / L; and the sulfuric acid concentration is 3~5 mol / L. Step S2: Place the vanadium sulfate electrolyte in a rotary evaporator and perform rotary evaporation according to the set heat preservation temperature and circulating cooling liquid temperature to obtain vanadium sulfate concentrate; Step S3: Add barium chloride solution to the vanadium sulfate concentrate and stir thoroughly to obtain crude vanadium sulfate hydrochloride solution; Step S4: Filter the crude vanadium sulfate hydrochloride solution using a microporous membrane, collect the filtrate, and obtain a concentrated vanadium sulfate hydrochloride solution. Step S5: Add deionized water to the vanadium sulfate hydrochloride concentrate to dilute the concentrate and obtain a mixed acid vanadium electrolyte.

2. The preparation method according to claim 1, characterized in that, In step S1: The average valence state of vanadium ions in the vanadium sulfate-based electrolyte is 3.

5.

3. The preparation method according to claim 1, characterized in that, In step S2: The insulation temperature is 50~80℃; The temperature of the circulating coolant is 0~10℃.

4. The preparation method according to claim 1, characterized in that, In step S3: The concentration of the barium chloride solution is 0.5~1.5 mol / L; The barium chloride used was of analytical grade.

5. The preparation method according to claim 1, characterized in that, In step S4: The microporous filter membrane is one of polyethylene membrane, polypropylene membrane, polyethersulfone membrane, polyvinylidene fluoride membrane, polytetrafluoroethylene membrane, polyacrylonitrile membrane, and polyamide membrane; The microporous filter membrane has a pore size of 0.2~2μm and a thickness of 100~200μm.

6. A mixed acid-based vanadium electrolyte, characterized in that, The mixed acid-based vanadium electrolyte is prepared using the preparation method of the mixed acid-based vanadium electrolyte as described in any one of claims 1 to 5.

7. An application of a mixed acid-based vanadium electrolyte, characterized in that, The mixed acid-based vanadium electrolyte prepared by the preparation method according to any one of claims 1 to 5 or the mixed acid-based vanadium electrolyte according to claim 6 is applied to an all-vanadium redox flow battery.

Images