Mixed acid-based electrolyte and preparation method and application thereof

Abstract

The invention relates to the technical field of all-vanadium redox flow batteries, and discloses a mixed acid-based electrolyte and a preparation method and application thereof.The preparation method at least comprises the following steps that a sulfuric acid-based vanadium electrolyte is prepared through a chemical reduction-electrolysis method, the sulfuric acid-based vanadium electrolyte is poured into a rotary container of a rotary evaporator, rotary evaporation operation is conducted, and the mixed acid-based electrolyte is obtained; adding a barium chloride solution into the sulfuric acid-based vanadium concentrated solution, fully stirring to obtain a sulfate acid-based vanadium crude solution, filtering the sulfate acid-based vanadium crude solution by using a microfiltration membrane to obtain a filtrate, namely the sulfate acid-based vanadium concentrated solution, adding deionized water into the sulfate acid-based vanadium concentrated solution, diluting the concentrated solution, and filtering to obtain the sulfate acid-based vanadium sulfate. The mixed acid group vanadium electrolyte has the advantages of being high in energy density, wide in use temperature range and good in vanadium stability, and the problems that the hydrochloric acid concentration is difficult to control accurately and the environment is polluted due to hydrochloric acid volatilization and chlorine evolution during electrolysis in a conventional method are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrolyte of all-vanadium redox flow battery, and particularly relates to a mixed acid-based electrolyte and a preparation method and application thereof. BACKGROUND

[0002] All-vanadium redox flow battery (VRFB) is a kind of energy storage battery based on the redox reaction of vanadium ions, which uses the reversible reaction of vanadium ions (V 2+ / V 3+ and VO 2+ / VO2 + ) in electrolyte to realize energy storage and release, and has the advantages of high energy conversion efficiency, long cycle life, convenient capacity adjustment, intrinsic safety and environmental friendliness, and can be used in the fields of renewable energy such as solar energy and wind energy, and large-scale energy storage such as peak load shifting of power grid, and is one of the most promising energy storage devices. Among them, the electrolyte as the carrier of active material is one of the most important components in the all-vanadium redox flow battery, and is the energy module of the vanadium battery system, and the performance and concentration of the electrolyte directly affect the performance and energy density of the battery. The commonly used electrolyte of the vanadium battery is sulfuric acid-based electrolyte, and the boundary temperature thereof is generally in the range of 5-40℃, and exceeding the temperature boundary will cause the precipitation of vanadium ions, which will cause irreversible damage to the battery system, and the vanadium concentration in the sulfuric acid-based electrolyte is generally not high, which leads to the difficulty in improving the energy density of the battery.

[0003] In recent years, mixed acid of hydrochloric acid and sulfuric acid as a supporting electrolyte of vanadium redox flow battery energy storage medium gradually replaced the pure sulfuric acid system, the system has the advantages of high energy density, wide use temperature (-20~50℃). The preparation method of the mixed acid system is similar to the sulfuric acid system, mainly using chemical reduction method or electrolysis method. The chemical method mainly uses high valence vanadium oxide or vanadate as raw material, heated in a certain concentration of sulfate hydrochloric acid solution and added reducing agent (such as H2, CH4, S, SO2, etc.) to make it dissolve and prepare vanadium electrolyte. The advantage of chemical synthesis method is that the production equipment is simple, but the dissolution speed of solid is slow, and the reducing agent added will be difficult to eliminate, which will affect the purity and performance of vanadium electrolyte. The electrolysis method generally uses a diaphragm electrolysis cell device, and vanadium-containing raw materials such as V2O5 or metavanadate are added to the negative electrode area of the electrolysis cell. The same concentration of sulfuric acid hydrochloric acid is added to the positive electrode area, and a suitable direct current is applied to the two poles of the electrolysis cell. V2O5 or metavanadate is reduced on the surface of the negative electrode to prepare a vanadium electrolyte based on sulfuric acid hydrochloric acid. The electrolysis method is gradually recognized and adopted in the preparation of vanadium electrolyte in the sulfuric acid system, but in the mixed acid system of sulfuric acid and hydrochloric acid, the concentration of hydrochloric acid is difficult to accurately control and environmental pollution problems caused by the volatilization and chlorine precipitation of hydrochloric acid during electrolysis. Therefore, it is necessary to develop a low-cost and high-performance preparation method of vanadium electrolyte based on sulfuric acid hydrochloric acid for vanadium redox flow battery. SUMMARY

[0004] The purpose of the present application is to provide a mixed acid-based electrolyte and its preparation method and application, which solves the problems of the prior art.

[0005] The technical scheme adopted by the present application is as follows: In a first aspect, a preparation method of a mixed acid-based electrolyte is disclosed, comprising the following steps: Step S1: preparing a vanadium electrolyte based on sulfuric acid with known vanadium ion concentration and sulfuric acid concentration; Step S2: placing the vanadium electrolyte based on sulfuric acid in a rotary evaporator, and performing rotary evaporation operation according to the set heat preservation temperature and circulating cooling liquid temperature, to obtain a concentrated vanadium electrolyte based on sulfuric acid; Step S3: adding barium chloride solution to the concentrated vanadium electrolyte based on sulfuric acid, and fully stirring to obtain a crude vanadium electrolyte based on sulfuric acid hydrochloric acid; Step S4: filtering the crude vanadium electrolyte based on sulfuric acid hydrochloric acid by using a microporous filter membrane, and collecting the filtrate to obtain a concentrated vanadium electrolyte based on sulfuric acid hydrochloric acid; Step S5: adding deionized water to the concentrated vanadium electrolyte based on sulfuric acid hydrochloric acid to dilute the concentrated electrolyte, to obtain a mixed acid-based vanadium electrolyte.

[0006] In one embodiment, in the step S1: The vanadium ion concentration is 1.5~2.5 mol / L; The concentration of sulfuric acid is 3-5 mol / L; The average valence of vanadium ions in the sulfuric acid-based vanadium electrolyte is 3.5.

[0007] The sulfuric acid-based vanadium electrolyte with a certain vanadium concentration and a certain sulfuric acid concentration is prepared by a conventional method. If the vanadium concentration is too high, the dissolution is slow, and if the concentration is too low, the energy density is low. If the concentration of sulfuric acid is too high, the viscosity of the electrolyte is large, which will affect the voltage efficiency, and if the concentration is too low, it is difficult to dissolve the vanadium-containing raw material.

[0008] In one embodiment, in the step S2: The holding temperature is 50-80℃; The circulating cooling liquid temperature is 0-10℃.

[0009] The sulfuric acid-based vanadium electrolyte is poured into a rotary evaporator, and in the low-pressure and low-temperature environment of the rotary evaporator, the water in the sulfuric acid-based vanadium electrolyte is volatilized, realizing the synchronous increase of vanadium concentration and acid concentration. In this way, vanadium will not have the risk of precipitation, and the principle is as shown in formula (1): VO 2+ +H2O VO(OH)2+H + (1) Tetravalent vanadium (VO 2+ ) will also hydrolyze to form a hydroxyl complex, which may further form insoluble hydrated vanadium dioxide (VO(OH)2). If the concentration of hydrogen ions rises unilaterally, it will cause vanadium precipitation.

[0010] In one embodiment, in the step S3: The concentration of barium chloride solution is 0.5-1.5 mol / L; The barium chloride is of analytical purity.

[0011] Barium chloride solution is added to the sulfuric acid-based vanadium concentrate, and barium chloride reacts with sulfate in the concentrate (reaction equation as shown in formula (2)), generating insoluble barium sulfate precipitate, reducing the concentration of sulfate while introducing chloride ions, and maintaining the concentration of hydrogen ions unchanged, i.e. the concentration of vanadium and acid remains unchanged. This step is crucial, and by controlling the amount of barium chloride added, the purpose of regulating the concentration of hydrochloric acid is achieved, i.e. the purpose of regulating the ratio of vanadium, sulfuric acid and hydrochloric acid is achieved.

[0012] H2SO4+BaCl2→BaSO4↓+2HCl (2) In one embodiment, in the step S3: the sum of the volumes of the sulfuric acid-based vanadium concentrate and the barium chloride solution is equal to the volume of the sulfuric acid-based vanadium electrolyte.

[0013] In one embodiment, the step S4 in the present application is as follows: The microporous filter membrane is one of polyethylene membrane, polypropylene membrane, polyether sulfone membrane, polyvinylidene fluoride membrane, polytetrafluoroethylene membrane, polyacrylonitrile membrane and polyamide membrane. The microporous filter membrane has a pore size of 0.2-2 μm and a thickness of 100-200 μm.

[0014] The microporous filter membrane is used to filter the crude vanadium sulfate hydrochloric acid base solution, and the crude solution contains barium sulfate precipitate. After filtration, the filtrate is a concentrated vanadium sulfate hydrochloric acid base solution. The barium sulfate precipitate is intercepted by the filter membrane to form a filter cake, which enters a simple recovery and regeneration stage (regeneration principle as formulas (3) and (4)), and finally generates barium chloride for recycling.

[0015] BaSO4+NaCO3→BaCO3+Na2SO4 (3) BaCO3+2HCl→BaCl2+H2O+CO2 (4) In the second aspect, a mixed acid base vanadium electrolyte is disclosed, which is prepared by the preparation method of the mixed acid base vanadium electrolyte.

[0016] In the third aspect, the application of the mixed acid base vanadium electrolyte is disclosed, and the mixed acid base vanadium electrolyte prepared by the preparation method or the mixed acid base vanadium electrolyte is applied to a full vanadium redox flow battery.

[0017] The beneficial effects of the present application at least include: 1. The sulfuric acid base electrolyte required in the first step of the present application does not need too high vanadium concentration, and a stable high-concentration sulfuric acid base vanadium electrolyte can be formed through subsequent rotary evaporation treatment, which skips the problem of slow dissolution of vanadium-containing raw materials and is beneficial to the improvement of battery energy density.

[0018] 2. The present application first prepares a sulfuric acid base electrolyte, then concentrates it by rotary evaporation, adds barium chloride for filtration, and then adjusts it into a mixed acid base vanadium electrolyte, which avoids the problems of difficult accurate control of hydrochloric acid concentration and environmental pollution caused by volatilization and chlorine precipitation of hydrochloric acid during electrolysis in the conventional method (first preparing a sulfuric acid hydrochloric acid mixed acid electrolyte, then dissolving vanadium-containing raw materials, and then electrolytic reduction), and even potential safety problems.

[0019] 3. The preparation process of the present application is simple, the cost is low, and the additional raw material barium chloride can be recycled. DETAILED DESCRIPTION

[0020] Figure 1 The flow chart of the preparation method of the mixed acid base electrolyte of the present application is shown. DETAILED DESCRIPTION

[0021] 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.

[0022] 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.

[0023] The formula for calculating the vanadium concentration C1 in the final mixed acid-based vanadium electrolyte is as follows: ; In the formula, C V This represents the vanadium concentration in the vanadium sulfate-based electrolyte.

[0024] The formula for calculating the sulfuric acid concentration C2 in the final mixed acid vanadium electrolyte is as follows: ; 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.

[0025] The formula for calculating the hydrochloric acid concentration C3 in the final mixed acid-based vanadium electrolyte is as follows: .

[0026] In the following examples and comparative examples, V1 is 1L.

[0027] Example 1: The following technical solution is adopted. The sulfuric acid-based vanadium electrolyte with vanadium concentration of 1.5 mol / L and sulfuric acid concentration of 3 mol / L is prepared by using the chemical reduction-electrolysis method, 1L of the sulfuric acid-based vanadium electrolyte is poured into a rotating container of a rotary evaporator, the heat preservation temperature of the container is set to 50℃, the circulating cooling liquid temperature is set to 0℃, the rotary evaporation operation is performed, 0.65L of the sulfuric acid-based vanadium concentrated solution is obtained, 0.05L of the barium chloride solution with a concentration of 0.5 mol / L is added to the sulfuric acid-based vanadium concentrated solution, and the solution is fully stirred to obtain the crude sulfuric acid-hydrochloric acid-based vanadium solution, the crude sulfuric acid-hydrochloric acid-based vanadium solution is filtered by using a microporous filter film with a pore size of 0.2 μm and a thickness of 100 μm, the filtrate is the sulfuric acid-hydrochloric acid-based vanadium concentrated solution, and then 0.02L of deionized water is added to the sulfuric acid-hydrochloric acid-based vanadium concentrated solution to dilute the concentrated solution, so that the final mixed acid-based vanadium electrolyte is obtained. In the 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.

[0028] Example 2: The following technical scheme is adopted The sulfuric acid-based vanadium electrolyte with vanadium concentration of 1.5 mol / L and sulfuric acid concentration of 3.5 mol / L is prepared by using the chemical reduction-electrolysis method, 1L of the sulfuric acid-based vanadium electrolyte is poured into a rotating container of a rotary evaporator, the heat preservation temperature of the container is set to 60℃, the circulating cooling liquid temperature is set to 5℃, the rotary evaporation operation is performed, 0.65L of the sulfuric acid-based vanadium concentrated solution is obtained, 0.05L of the barium chloride solution with a concentration of 0.8 mol / L is added to the sulfuric acid-based vanadium concentrated solution, and the solution is fully stirred to obtain the crude sulfuric acid-hydrochloric acid-based vanadium solution, the crude sulfuric acid-hydrochloric acid-based vanadium solution is filtered by using a microporous filter film with a pore size of 0.5 μm and a thickness of 120 μm, the filtrate is the sulfuric acid-hydrochloric acid-based vanadium concentrated solution, and then 0.01L of deionized water is added to the sulfuric acid-hydrochloric acid-based vanadium concentrated solution to dilute the concentrated solution, so that the final mixed acid-based vanadium electrolyte is obtained. In the 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.

[0029] Example 3: The following technical scheme is adopted The sulfuric acid-based vanadium electrolyte with a vanadium concentration of 2 mol / L and a sulfuric acid concentration of 4 mol / L is prepared by using a chemical reduction-electrolysis method, 1L of the sulfuric acid-based vanadium electrolyte is poured into a rotating container of a rotary evaporator, the heat preservation temperature of the container is set to 70℃, the circulating cooling liquid temperature is set to 5℃, and rotary evaporation operation is performed, so that 0.6L of a sulfuric acid-based vanadium concentrated solution is obtained, 0.1L of a barium chloride solution with a concentration of 1 mol / L is added to the sulfuric acid-based vanadium concentrated solution, and the solution is fully stirred to obtain a crude sulfuric acid-hydrochloric acid-based vanadium solution, the crude sulfuric acid-hydrochloric acid-based vanadium solution is filtered by using a microporous filter membrane with a pore size of 1 μm and a thickness of 150 μm, and the filtrate is a sulfuric acid-hydrochloric acid-based vanadium concentrated solution, and then 0.1L of deionized water is added to the sulfuric acid-hydrochloric acid-based vanadium concentrated solution to dilute the concentrated solution, so that the final mixed acid-based vanadium electrolyte is obtained. In the 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.

[0030] Example 4: The following technical scheme is adopted The sulfuric acid-based vanadium electrolyte with a vanadium concentration of 2 mol / L and a sulfuric acid concentration of 4.5 mol / L is prepared by using a chemical reduction-electrolysis method, 1L of the sulfuric acid-based vanadium electrolyte is poured into a rotating container of a rotary evaporator, the heat preservation temperature of the container is set to 75℃, the circulating cooling liquid temperature is set to 10℃, and rotary evaporation operation is performed, so that 0.55L of a sulfuric acid-based vanadium concentrated solution is obtained, 0.4L of a barium chloride solution with a concentration of 1.1 mol / L is added to the sulfuric acid-based vanadium concentrated solution, and the solution is fully stirred to obtain a crude sulfuric acid-hydrochloric acid-based vanadium solution, the crude sulfuric acid-hydrochloric acid-based vanadium solution is filtered by using a microporous filter membrane with a pore size of 1.5 μm and a thickness of 180 μm, and the filtrate is a sulfuric acid-hydrochloric acid-based vanadium concentrated solution, and then 0.1L of deionized water is added to the sulfuric acid-hydrochloric acid-based vanadium concentrated solution to dilute the concentrated solution, so that the final mixed acid-based vanadium electrolyte is obtained. In the 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.

[0031] Example 5: The following technical scheme is adopted The sulfuric acid-based vanadium electrolyte with a vanadium concentration of 2.5 mol / L and a sulfuric acid concentration of 5 mol / L is prepared by a chemical reduction-electrolysis method. The volume of 1 L of the sulfuric acid-based vanadium electrolyte is poured into a rotating container of a rotary evaporator. The heat preservation temperature of the container is set to 80°C, and the circulating cooling liquid temperature is set to 10°C. The rotary evaporation operation is performed. The volume of 0.55 L of the sulfuric acid-based vanadium concentrated solution is obtained. The volume of 0.4 L of the barium chloride solution with a concentration of 1.5 mol / L is added to the sulfuric acid-based vanadium concentrated solution. The sulfuric acid-based vanadium concentrated solution is obtained after sufficient stirring. The micro-porous filter membrane with a pore size of 2 μm and a thickness of 200 μm is used to filter the sulfuric acid-based vanadium concentrated solution. The filtrate is the sulfuric acid-based vanadium concentrated solution. The volume of 0.2 L of the deionized water is added to the sulfuric acid-based vanadium concentrated solution. The concentrated solution is diluted. The final mixed acid-based vanadium electrolyte is obtained after the adjustment. In the 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.

[0032] Comparative Example 1: The following technical solution is adopted The preparation process is consistent with that of Example 3, and the only difference is that the S2 step is not performed.

[0033] The sulfuric acid-based vanadium electrolyte with a vanadium concentration of 2 mol / L and a sulfuric acid concentration of 4 mol / L is prepared by a chemical reduction-electrolysis method. The volume of 1 L of the sulfuric acid-based vanadium electrolyte is poured into the volume of 0.1 L of the barium chloride solution with a concentration of 1 mol / L. The sulfuric acid-based vanadium concentrated solution is obtained after sufficient stirring. The micro-porous filter membrane with a pore size of 1 μm and a thickness of 150 μm is used to filter the sulfuric acid-based vanadium concentrated solution. The filtrate is the sulfuric acid-based vanadium concentrated solution. The volume of 0.1 L of the deionized water is added to the sulfuric acid-based vanadium concentrated solution. The concentrated solution is diluted. The final mixed acid-based vanadium electrolyte is obtained after the adjustment. In the mixed acid-based vanadium electrolyte, the vanadium concentration is 1.67 mol / L, the sulfuric acid concentration is 3.25 mol / L, and the hydrochloric acid concentration is 0.167 mol / L.

[0034] Comparative Example 2: The following technical solution is adopted The preparation process is consistent with that of Example 3, and the only difference is that the barium chloride in the step S3 is replaced by hydrochloric acid.

[0035] The sulfuric acid-based vanadium electrolyte with a vanadium concentration of 2 mol / L and a sulfuric acid concentration of 4 mol / L is prepared by a chemical reduction-electrolysis method. The volume of the sulfuric acid-based vanadium electrolyte is 1 L. The sulfuric acid-based vanadium electrolyte is poured into a rotating container of a rotary evaporator. The heat preservation temperature of the container is set to 70 DEG C, and the circulating cooling liquid temperature is set to 5 DEG C. The rotary evaporation operation is performed. The volume of the sulfuric acid-based vanadium concentrated solution obtained is 0.6 L. The hydrochloric acid solution with a volume of 0.1 L and a concentration of 1 mol / L is added to the sulfuric acid-based vanadium concentrated solution. The sulfuric acid-hydrochloric acid-based vanadium crude solution is obtained by fully stirring. The sulfuric acid-hydrochloric acid-based vanadium crude solution is filtered by using the microporous filter membrane with a pore size of 1 μm and a thickness of 150 μm. The filtrate is the sulfuric acid-hydrochloric acid-based vanadium concentrated solution. The deionized water with a volume of 0.1 L is added to the sulfuric acid-hydrochloric acid-based vanadium concentrated solution. The concentrated solution is diluted. The final mixed acid-based vanadium electrolyte is obtained by blending. In the 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.

[0036] The vanadium ion concentration, the sulfuric acid concentration, and the 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.

[0037] Table 1: Physical property parameter table of mixed acid-based vanadium electrolyte

[0038] The mixed acid-based vanadium electrolytes prepared in Examples 1-5 and Comparative Examples 1-2 are tested on the electric pile. The coulombic efficiency, the voltage efficiency, and the energy efficiency are tested and recorded under the same test conditions. The test results are shown in Table 2. Table 2: Cell performance test table of mixed acid-based vanadium electrolyte

[0039] In the above test results, the vanadium concentration and the sulfate concentration of the concentrated solutions of Examples 1-5 are increased after the rotary evaporation. The chloride ions, i.e., the hydrochloric acid component, are introduced by adding the barium chloride solution and filtering. The stability of the high-concentration vanadium electrolyte is improved. The vanadium utilization rate is improved. The battery energy density is improved. Due to the increase of the acid concentration, the electrolyte conductivity is increased. The ohmic polarization of the electrolyte is reduced. The voltage efficiency is high. The electrolyte of Comparative Example 1 is not treated by rotary evaporation. The barium chloride is directly added to the sulfuric acid-based electrolyte. The electrolyte is diluted. The vanadium concentration and the sulfate concentration are simultaneously reduced. The battery energy density is not high. The acid concentration is small. The conductivity is low. The voltage efficiency is low. In Comparative Example 2, the barium chloride is replaced by the hydrochloric acid. Although the hydrochloric acid component can be introduced, the sulfate concentration in the vanadium concentrated solution cannot be adjusted. The final electrolyte has a high sulfate concentration. The viscosity of the electrolyte is large. The electrolyte flow resistance and the pump consumption are increased. The voltage efficiency and the energy efficiency are low.

[0040] In summary, the preparation method of the application, the low concentration of sulfuric acid-based vanadium electrolyte is subjected to rotary evaporation operation, and the water in the sulfuric acid-based vanadium electrolyte is volatilized, so that the vanadium concentration and the acid concentration are increased synchronously, so that the vanadium is not at risk of precipitation, the problem of slow dissolution speed of vanadium-containing raw materials is skipped, and the improvement of battery energy density is also beneficial, the reaction of barium chloride and sulfate in the concentrated solution generates insoluble barium sulfate precipitate, reduces the concentration of sulfate and introduces chloride ions (hydrochloric acid), and maintains the concentration of hydrogen ions unchanged, that is, the vanadium concentration and the acid concentration remain unchanged. By controlling the amount of barium chloride added, the purpose of controlling the concentration of hydrochloric acid is achieved, that is, the purpose of controlling the ratio of vanadium, sulfuric acid and hydrochloric acid is achieved, and therefore, the prepared mixed acid-based vanadium electrolyte has high energy density, wide use temperature, good vanadium stability.

[0041] The application first prepares a sulfuric acid-based electrolyte, then concentrates by rotary evaporation, adds barium chloride and filters, and then adjusts to form a sulfate acid-based vanadium electrolyte, thereby avoiding the problems of difficult accurate control of hydrochloric acid concentration and environmental pollution caused by volatilization and chlorine precipitation of hydrochloric acid during electrolysis in the conventional method (first preparing a sulfate acid-based mixed acid electrolyte, then dissolving vanadium-containing raw materials, and then electrolytic reduction), and even potential safety problems, the preparation process is simple, the cost is low, and the additional raw material barium chloride can be recycled.

[0042] The above only describes the preferred embodiments of the application and is not intended to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A method for preparing a mixed acid-based vanadium electrolyte, characterized in that, The preparation method comprises the following steps: Step S1: preparing a vanadium electrolyte with a known vanadium ion concentration and a sulfuric acid concentration; Step S2: placing the vanadium electrolyte in a rotary evaporator, and performing rotary evaporation operation according to a set holding temperature and a circulating coolant temperature, to obtain a concentrated vanadium electrolyte; Step S3: adding a barium chloride solution to the concentrated vanadium electrolyte, and fully stirring, to obtain a crude vanadium electrolyte; Step S4: filtering the crude vanadium electrolyte by using a microporous filter membrane, and collecting a filtrate, to obtain a concentrated vanadium electrolyte; Step S5: adding deionized water to the concentrated vanadium electrolyte, and diluting the concentrated vanadium electrolyte, to obtain a mixed acid vanadium electrolyte.

2. The production method according to claim 1, characterized by, In the step S1: The vanadium ion concentration is 1.5-2.5 mol / L; The sulfuric acid concentration is 3-5 mol / L; The average valence of vanadium ions in the vanadium electrolyte is 3.

5.

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

4. The method of claim 1, wherein, In the step S3: The barium chloride solution concentration is 0.5-1.5 mol / L; The barium chloride is of an analytical purity grade.

5. The preparation method according to claim 1, characterized in that, In the step S3: the sum of the volumes of the concentrated vanadium electrolyte and the barium chloride solution is equal to the volume of the vanadium electrolyte.

6. The method of claim 1, wherein, In the step S4: The microporous filter membrane is one of a polyethylene membrane, a polypropylene membrane, a polyether sulfone membrane, a polyvinylidene fluoride membrane, a polytetrafluoroethylene membrane, a polyacrylonitrile membrane, and a polyamide membrane; The microporous filter membrane has a pore size of 0.2-2 μm and a thickness of 100-200 μm.

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

8. Use of a mixed acid-based vanadium electrolyte, characterized in that, The mixed acid vanadium electrolyte prepared by using the preparation method according to any one of claims 1-6 or the mixed acid vanadium electrolyte according to claim 7 is applied to a full vanadium redox flow battery.

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