All-vanadium redox flow battery electrolyte and battery

Abstract

The invention relates to the technical field of all-vanadium redox flow battery electrolytes, and discloses an all-vanadium redox flow battery electrolyte and a battery, the all-vanadium redox flow battery electrolyte comprises a supporting electrolyte, vanadium ions and a deep eutectic solvent; the supporting electrolyte is a mixed acid system composed of organic sulfonic acid and sulfuric acid; the mass fraction of the deep eutectic solvent in the electrolyte is 1%-10%. According to the all-vanadium redox flow battery electrolyte provided by the invention, a novel electrolyte system is constructed by introducing the deep eutectic solvent into the organic sulfonic acid-sulfuric acid mixed acid supporting electrolyte. The system effectively improves the physical and chemical properties of the electrolyte, when the total vanadium concentration is 2.8 mol / L, the V < 5 + > solubility is not lower than 2.5 mol / L, and the dynamic viscosity at 25 DEG C is not higher than 4.0 mPa.s. This characteristic contributes to reducing the pumping loss of the battery system while maintaining high energy density. The generation of V2O5 precipitates is inhibited, the stability of the electrolyte at a high temperature is improved, and the deep eutectic solvent also promotes the improvement of the energy efficiency and the cycle stability of the battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrolyte of all-vanadium redox flow battery, and particularly relates to a battery electrolyte composed of a mixed acid type supporting electrolyte composed of organic sulfonic acid and sulfuric acid and a deep eutectic solvent. BACKGROUND

[0002] As a large-scale energy storage technology, all-vanadium redox flow battery has attracted extensive attention due to its advantages of independent design of power and capacity, long cycle life, high safety, etc. The electrolyte, as a core component of the all-vanadium redox flow battery, directly determines the energy density, working efficiency and stability of the battery.

[0003] At present, commercial all-vanadium redox flow battery electrolyte generally uses a single sulfuric acid solution as a supporting electrolyte. Although this system has low cost and simple preparation, its inherent technical defects limit the further improvement of the battery performance. First, the solubility of vanadium ions (especially V 5+ ) in the solution is limited under the single sulfuric acid system, and V2O5 precipitate is easily precipitated at low temperature, which not only leads to loss of active material, but also may block the flow channel and threaten the safety of battery operation. Secondly, the electrochemical window and stability of the system need to be improved. In order to improve the above problems, researchers try to introduce organic sulfonic acid (such as methanesulfonic acid, benzenesulfonic acid, etc.) and sulfuric acid to form a mixed acid supporting electrolyte system. Such mixed acid system can improve the solubility of vanadium and the stability of the solution to a certain extent, but it often brings a new problem of significant increase of the dynamic viscosity of the electrolyte, which leads to increased pump consumption and decreased ion conductivity, and further affects the overall energy efficiency of the battery.

[0004] Therefore, it is a technical problem to be solved in the field to develop an all-vanadium redox flow battery electrolyte which can simultaneously have high vanadium solubility, appropriate viscosity and good stability. SUMMARY

[0005] The application aims to provide an all-vanadium redox flow battery electrolyte to solve the problems of limited vanadium solubility, high electrolyte viscosity and difficult to balance the energy density and energy efficiency of the battery, and to realize the effects of high vanadium solubility, low dynamic viscosity and wide temperature adaptability.

[0006] According to the above idea, the technical solution adopted by the application is as follows: According to a first aspect of the embodiments of the application, an all-vanadium redox flow battery electrolyte is provided, comprising a supporting electrolyte, vanadium ions and a deep eutectic solvent. The supporting electrolyte is a mixed acid system composed of organic sulfonic acid and sulfuric acid. The mass fraction of the deep eutectic solvent in the electrolyte is 1% to 10%.

[0007] In some embodiments, the deep eutectic solvent consists of a hydrogen bond acceptor and a hydrogen bond donor; The hydrogen bond acceptor is choline chloride; The hydrogen bond donor is selected from at least one of urea, ethylene glycol, glycerol, malonic acid, and lactic acid.

[0008] In some embodiments, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1.5 to 1:2.5.

[0009] Furthermore, the mass fraction of the deep eutectic solvent in the electrolyte is 3% to 7%.

[0010] In some embodiments, the mass fraction of the supporting electrolyte in the electrolyte is 30% to 60%.

[0011] Optionally, the organic sulfonic acid includes any one of 2-hydroxyethanesulfonic acid, 2-hydroxy-1-propanesulfonic acid, and 1-hydroxy-2-propanesulfonic acid.

[0012] In some embodiments, the molar ratio of organic sulfonic acid to sulfuric acid in the electrolyte is 1:1 to 1:5.

[0013] In some embodiments, V in the electrolyte 5+ The solubility of the electrolyte is not less than 2.5 mol / L; and / or, when the vanadium concentration is 2.8 mol / L, the dynamic viscosity of the electrolyte at 25°C is not higher than 4.0 mPa·s.

[0014] According to a second aspect of the present invention, a vanadium redox flow battery is provided, including a positive electrode chamber; Negative electrode chamber; The electrolyte as described above; And an ion exchange membrane separating the positive and negative electrode chambers. Furthermore, the electrolyte includes a positive electrode electrolyte and a negative electrode electrolyte; The positive electrode electrolyte includes V 4+ and V 5+ Electric pair; The negative electrode electrolyte includes V 2+ and V 3+ Electric pair.

[0015] The beneficial effects of this invention are as follows: 1. The vanadium redox flow battery electrolyte provided by this invention constructs a novel electrolyte system by introducing a deep eutectic solvent into an organic sulfonic acid-sulfuric acid mixed acid supported electrolyte. This system effectively improves the physicochemical properties of the electrolyte, exhibiting the characteristic of pentavalent vanadium ions (V... 5+ Increased solubility and decreased dynamic viscosity. In an electrolyte with a total vanadium concentration of 2.8 mol / L, V5+ It remains stably soluble, with an effective concentration sufficient to support battery operation at high energy density without precipitation. This characteristic helps reduce pumping losses in the battery system while maintaining high energy density.

[0016] 2. In this invention, the deep eutectic solvent serves as a functional additive. Through its hydrogen bond network, the deep eutectic solvent synergistically works with the mixed acid system to optimize the solvation environment of vanadium ions. This effect not only helps to suppress the formation of V₂O₅ precipitate and improves the stability of the electrolyte at high temperatures, but also jointly contributes to the improvement of battery energy efficiency and cycle stability. The battery using this electrolyte can achieve an energy efficiency of 85.5% and a capacity retention rate of 92% after 1000 cycles. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the charging of the all-vanadium redox flow battery and electrolyte system of the present invention; Figure 2 This is a discharge schematic diagram of the vanadium redox flow battery and electrolyte system of the present invention. Detailed Implementation

[0018] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0019] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise defined, the technical or scientific terms used in this application should be understood in their ordinary sense by one of ordinary skill in the art to which this invention pertains. The words “a” or “one” and similar terms used in this application specification and claims do not indicate a limitation of quantity, but rather indicate the presence of at least one. “A plurality” means two or more. The words “comprising” or “including” and similar terms mean that the element or object preceding “comprising” or “including” covers the element or object listed following “comprising” or “including” and its equivalents, and does not exclude other elements or objects. The words “connected” or “linked” and similar terms are not limited to physical or mechanical connections and can include electrical connections, whether direct or indirect. The words “above” and / or “below” and similar terms are for ease of description only and are not limited to a location or spatial orientation. The singular forms “a,” “the,” and “the” used in this application specification and appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0020] This application provides an all-vanadium redox flow battery electrolyte, comprising a supporting electrolyte, vanadium ions, and a deep eutectic solvent; The supporting electrolyte is a mixed acid system composed of organic sulfonic acid and sulfuric acid; The mass fraction of the deep eutectic solvent in the electrolyte is 1% to 10%.

[0021] The vanadium redox flow battery electrolyte provided by this invention constructs a novel electrolyte system by introducing a specific mass fraction of deep eutectic solvent into an organic sulfonic acid-sulfuric acid mixed acid supported electrolyte. This system effectively improves the physicochemical properties of the electrolyte, exhibiting the characteristic of pentavalent vanadium ions (V6). 5+ Increased solubility and decreased dynamic viscosity. At a total vanadium concentration of 2.8 mol / L, V 5+ The solubility of all components is not less than 2.5 mol / L, and the dynamic viscosity at 25°C is not higher than 4.0 mPa·s. This characteristic helps to reduce pumping losses in the battery system while maintaining high energy density. The deep eutectic solvent, through its hydrogen bond network, works synergistically with the mixed acid system to optimize the solvation environment of vanadium ions. This not only helps to suppress the formation of V2O5 precipitates and improve the stability of the electrolyte at high temperatures, but also contributes to the improvement of battery energy efficiency and cycle stability.

[0022] The vanadium redox flow battery described in this application includes: Positive electrode chamber; Negative electrode chamber; The electrolyte as described above; And an ion exchange membrane separating the positive electrode chamber and the negative electrode chamber.

[0023] The following describes in detail an all-vanadium redox flow battery electrolyte and battery with reference to embodiments.

[0024] Example 1 The hydrogen bond acceptor choline chloride and the hydrogen bond donor urea were weighed and mixed in a molar ratio of 1:2, and stirred continuously in a constant temperature environment of 80°C until a colorless and transparent homogeneous liquid was formed. This is the deep eutectic solvent, which was then cooled to room temperature for later use.

[0025] Add the organic sulfonic acid 2-hydroxyethanesulfonic acid and sulfuric acid sequentially to deionized water, controlling the mass fraction of the supporting electrolyte in the solution to be 45%, wherein the molar ratio of organic sulfonic acid to sulfuric acid is 1:2. Stir thoroughly until completely dissolved to obtain a clear supporting electrolyte mother solution.

[0026] A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 5%.

[0027] Subsequently, excess V₂O₅ powder was added to the mixed solution, and the mixture was stirred at a constant temperature in a 60°C water bath until the V₂O₅ was completely dissolved and reacted to form a product containing V. 4+ The blue electrolyte was adjusted to a vanadium concentration of 2.8 mol / L by adding deionized water. After electrolytic treatment, the electrolyte contained V... 4+ / V 5+ The redox couple is used as the positive electrode electrolyte.

[0028] Using the same proportions of supporting electrolyte mother liquor and deep eutectic solvent, the prepared V-containing solution was reduced by electrochemical reduction or chemical reduction. 4+ The electrolyte was completely reduced to obtain a solution containing V. 2+ / V 3+ The negative electrode electrolyte of the redox couple also has a vanadium concentration of 2.8 mol / L.

[0029] Example 2 Everything else is the same as in Example 1, except that: A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 1%.

[0030] Example 3 Everything else is the same as in Example 1, except that: A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 10%.

[0031] Example 4 Everything else is the same as in Example 1, except that: Choline chloride, the hydrogen bond acceptor, and urea, the hydrogen bond donor, were weighed and mixed at a molar ratio of 1:2.5. The mixture was then placed in a constant temperature environment of 80°C and stirred continuously until a colorless, transparent, homogeneous liquid was formed. This deep eutectic solvent was then cooled to room temperature for later use.

[0032] Add the organic sulfonic acid 2-hydroxyethanesulfonic acid and sulfuric acid sequentially to deionized water, controlling the mass fraction of the supporting electrolyte in the solution to be 45%, wherein the molar ratio of organic sulfonic acid to sulfuric acid is 1:2. Stir thoroughly until completely dissolved to obtain a clear supporting electrolyte mother solution.

[0033] A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 5%.

[0034] Example 5 Everything else is the same as in Example 1, except that: The hydrogen bond acceptor choline chloride and the hydrogen bond donor urea were weighed and mixed at a molar ratio of 1:1.5, and then stirred continuously in a constant temperature environment of 80°C until a colorless and transparent homogeneous liquid was formed. This is the deep eutectic solvent, which was then cooled to room temperature for later use.

[0035] Add the organic sulfonic acid 2-hydroxyethanesulfonic acid and sulfuric acid sequentially to deionized water, controlling the mass fraction of the supporting electrolyte in the solution to be 45%, wherein the molar ratio of organic sulfonic acid to sulfuric acid is 1:2. Stir thoroughly until completely dissolved to obtain a clear supporting electrolyte mother solution.

[0036] A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 5%.

[0037] Example 6 The hydrogen bond acceptor choline chloride and the hydrogen bond donor urea were weighed and mixed in a molar ratio of 1:2, and stirred continuously in a constant temperature environment of 80°C until a colorless and transparent homogeneous liquid was formed. This is the deep eutectic solvent, which was then cooled to room temperature for later use.

[0038] Add the organic sulfonic acid 2-hydroxyethanesulfonic acid and sulfuric acid sequentially to deionized water, controlling the mass fraction of the supporting electrolyte in the solution to be 30%, wherein the molar ratio of organic sulfonic acid to sulfuric acid is 1:2. Stir thoroughly until completely dissolved to obtain a clear supporting electrolyte mother solution.

[0039] A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 5%.

[0040] Example 7 The hydrogen bond acceptor choline chloride and the hydrogen bond donor urea were weighed and mixed in a molar ratio of 1:2, and then stirred continuously in a constant temperature environment of 80°C until a colorless and transparent homogeneous liquid was formed. This is the deep eutectic solvent, which was then cooled to room temperature for later use.

[0041] Add the organic sulfonic acid 2-hydroxyethanesulfonic acid and sulfuric acid sequentially to deionized water, controlling the mass fraction of the supporting electrolyte in the solution to be 60%, wherein the molar ratio of organic sulfonic acid to sulfuric acid is 1:2. Stir thoroughly until completely dissolved to obtain a clear supporting electrolyte mother solution.

[0042] A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 5%.

[0043] Comparative Example 1 Everything else is the same as in Example 1, except that: No deep eutectic solvents or organic sulfonic acids are added.

[0044] Add excess V₂O₅ powder to a sulfuric acid solution and stir at a constant temperature in a 60°C water bath until the V₂O₅ is completely dissolved and reacts to form a product containing V. 4+ The blue electrolyte was used. The vanadium concentration in the electrolyte was adjusted to 2.8 mol / L by adding deionized water. After electrolysis, the electrolyte contained V... 4+ / V 5+ The redox couple is used as the positive electrode electrolyte.

[0045] Using the same sulfuric acid solution, the prepared V-containing solution was reduced by electrochemical reduction or chemical reduction. 4+ The electrolyte was completely reduced to obtain a solution containing V. 2+ / V 3+ The negative electrode electrolyte of the redox couple also has a vanadium concentration of 2.8 mol / L.

[0046] Comparative Example 2 Everything else is the same as in Example 1, except that: No deep eutectic solvents are added.

[0047] Add the organic sulfonic acid 2-hydroxyethanesulfonic acid and sulfuric acid sequentially to deionized water, controlling the mass fraction of the supporting electrolyte in the solution to be 45%, wherein the molar ratio of organic sulfonic acid to sulfuric acid is 1:2. Stir thoroughly until completely dissolved to obtain a clear supporting electrolyte mother solution.

[0048] Subsequently, excess V₂O₅ powder was added to the supporting electrolyte mother liquor, and the mixture was stirred at a constant temperature in a 60°C water bath until the V₂O₅ was completely dissolved and reacted to form a product containing V. 4+ The blue electrolyte was used. The vanadium concentration in the electrolyte was adjusted to 2.8 mol / L by adding deionized water. After electrolysis, the electrolyte contained V... 4+ / V 5+ The redox couple is used as the positive electrode electrolyte.

[0049] Using the same proportions of supporting electrolyte mother liquor and deep eutectic solvent, the prepared V-containing solution was reduced by electrochemical reduction or chemical reduction. 4+ The electrolyte was completely reduced to obtain a solution containing V. 2+ / V 3+ The negative electrode electrolyte of the redox couple also has a vanadium concentration of 2.8 mol / L.

[0050] Comparative Example 3 Everything else is the same as in Example 1, except that: A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 0.1%.

[0051] Comparative Example 4 Everything else is the same as in Example 1, except that: A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 20%.

[0052] Comparative Example 5 Everything else is the same as in Example 1, except that: The hydrogen bond acceptor choline chloride and the hydrogen bond donor urea were weighed and mixed at a molar ratio of 1:0.5, and then stirred continuously in a constant temperature environment of 80°C until a colorless and transparent homogeneous liquid was formed. This is the deep eutectic solvent, which was then cooled to room temperature for later use.

[0053] Add the organic sulfonic acid 2-hydroxyethanesulfonic acid and sulfuric acid sequentially to deionized water, controlling the mass fraction of the supporting electrolyte in the solution to be 45%, wherein the molar ratio of organic sulfonic acid to sulfuric acid is 1:2. Stir thoroughly until completely dissolved to obtain a clear supporting electrolyte mother solution.

[0054] A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 5%.

[0055] Comparative Example 6 Everything else is the same as in Example 1, except that: The hydrogen bond acceptor choline chloride and the hydrogen bond donor urea were weighed and mixed in a molar ratio of 1:2, and then stirred continuously in a constant temperature environment of 80°C until a colorless and transparent homogeneous liquid was formed. This is the deep eutectic solvent, which was then cooled to room temperature for later use.

[0056] Add the organic sulfonic acid 2-hydroxyethanesulfonic acid and sulfuric acid sequentially to deionized water, controlling the mass fraction of the supporting electrolyte in the solution to be 80%, wherein the molar ratio of organic sulfonic acid to sulfuric acid is 1:2. Stir thoroughly until completely dissolved to obtain a clear supporting electrolyte mother solution.

[0057] A certain amount of the prepared supporting electrolyte stock solution was measured, and the prepared deep eutectic solvent was added to it, stirring until completely dissolved. The mass fraction of the added deep eutectic solvent in the final positive electrode electrolyte was controlled to be 5%.

[0058] Table 1. Comparison of electrolyte performance between different embodiments and comparative examples

[0059] As shown in Table 1, the all-vanadium redox flow battery electrolytes prepared in Examples 1 to 7 of the present invention all have a solubility of pentavalent vanadium ions of not less than 2.5 mol / L, and a dynamic viscosity of not more than 4.0 mPa·s under the test conditions of vanadium concentration of 2.8 mol / L and 25°C.

[0060] Analysis of the data in Table 1 reveals that the introduction of deep eutectic solvent has a significant impact on electrolyte performance. Taking the test results of Example 1 and Comparative Example 2 as examples, under the premise of using the same mixed acid-supported electrolyte system, Example 1, with the addition of 5% (w / w) deep eutectic solvent, showed better performance at V... 5+ The electrolyte exhibits superior performance in terms of both solubility and dynamic viscosity. This result indicates that the deep eutectic solvent and the organic sulfonic acid-sulfuric acid mixed acid system have a synergistic effect, jointly optimizing the physicochemical properties of the electrolyte.

[0061] The data in Table 1 also reveal the suitable ranges for each process parameter. When the mass fraction of the deep eutectic solvent is 0.1%, its effect on improving performance is limited; while when the mass fraction reaches 20%, although high solubility is maintained, the dynamic viscosity increases significantly to 5.0 mPa·s, resulting in a decrease in battery energy efficiency to 80.5%.

[0062] Comparative Example 1 used pure sulfuric acid as the electrolyte, without the addition of organic sulfonic acid or deep eutectic solvent, and its V 5+ The solubility was only 2.0 mol / L, the dynamic viscosity reached 4.5 mPa·s, the energy efficiency was 80%, and the capacity retention after 1000 cycles was 85%. Furthermore, significant precipitation occurred at high temperatures, indicating that the single sulfuric acid system had significant deficiencies in vanadium solubility, viscosity, and stability. Comparative Example 2, based on an organic sulfonic acid-sulfuric acid mixed system without the addition of a deep eutectic solvent, showed improved performance compared to Comparative Example 1. 5+ The solubility increased to 2.3 mol / L, the dynamic viscosity decreased to 4.2 mPa·s, the energy efficiency was 82%, and the capacity retention was 87%. Only a small amount of precipitation occurred at high temperatures, but the performance still did not reach the level of Example 1. This indicates that although the mixed acid system can partially improve electrolyte performance, the introduction of a deep eutectic solvent plays a crucial role in further optimizing the vanadium ion solvation environment, reducing viscosity, and improving high-temperature stability.

[0063] When the mass fraction of the deep eutectic solvent is too low, such as 0.1% in Comparative Example 3, the hydrogen bond network formed is insufficient to effectively solvate and stabilize V. 5+ The presence of ions limits the improvement in solubility. When the mass fraction is too high, such as 20% in Comparative Example 4, the excessive high-viscosity deep eutectic solvent itself dominates the rheological properties of the electrolyte, leading to a significant increase in dynamic viscosity, thereby increasing pumping losses and reducing battery energy efficiency. Similarly, when the proportion of hydrogen bond donors is too low, such as the molar ratio of 1:0.5 in Comparative Example 5, it cannot form a stable and homogeneous deep eutectic solvent structure with choline chloride, rendering it ineffective. Furthermore, when the supporting electrolyte concentration is too high, such as 80% in Comparative Example 6, the excessive ionic strength in the system may cause ion aggregation leading to increased viscosity, and may also compress the solvation layer of vanadium ions, which is detrimental to their stable dissolution.

[0064] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. The invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0065] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. An electrolyte for a vanadium redox flow battery, characterised in that, The electrolyte comprises a supporting electrolyte, vanadium ions and a deep eutectic solvent; The supporting electrolyte is a mixed acid system composed of an organic sulfonic acid and sulfuric acid; The mass fraction of the deep eutectic solvent in the electrolyte is 1% to 10%.

2. A vanadium redox flow battery electrolyte according to claim 1, wherein, The deep eutectic solvent is composed of a hydrogen bond acceptor and a hydrogen bond donor; The hydrogen bond acceptor is choline chloride; The hydrogen bond donor is selected from at least one of urea, ethylene glycol, glycerol, malonic acid and lactic acid.

3. A vanadium redox flow battery electrolyte according to claim 2, wherein, The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1.5 to 1:2.

5.

4. The electrolyte for an all-vanadium redox flow battery according to claim 1, characterized by, The mass fraction of the deep eutectic solvent in the electrolyte is 3% to 7%.

5. The electrolyte of the vanadium redox flow battery according to claim 1, characterized in that, The mass fraction of the supporting electrolyte in the electrolyte is 30% to 60%.

6. A vanadium redox flow battery electrolyte according to claim 5, wherein, The organic sulfonic acid comprises any one of 2-hydroxyethanesulfonic acid, 2-hydroxy-1-propanesulfonic acid and 1-hydroxy-2-propanesulfonic acid.

7. A vanadium redox flow battery electrolyte according to claim 1, wherein, The molar concentration ratio of the organic sulfonic acid to sulfuric acid in the electrolyte is 1:1 to 1:

5.

8. The electrolyte of the vanadium redox flow battery according to claim 1, characterized in that, V in the electrolyte 5+ The solubility of the electrolyte is not less than 2.5 mol / L; and / or, when the vanadium concentration is 2.8 mol / L, the dynamic viscosity of the electrolyte at 25°C is not higher than 4.0 mPa·s.

9. An all-vanadium redox flow battery characterised in that, The battery comprises: a positive electrode chamber; a negative electrode chamber; the electrolyte as claimed in any one of claims 1 to 8; and an ion exchange membrane separating the positive electrode chamber and the negative electrode chamber.

10. A vanadium redox flow battery according to claim 9, wherein, The electrolyte comprises a positive electrode electrolyte and a negative electrode electrolyte; The positive electrolyte comprises V 4+ and V 5+ electrolyte; and / or The negative electrolyte comprises V 2+ and V 3+ electrolyte pair.

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