Supporting electrolyte of positive and negative electrolyte of all-vanadium redox flow battery and preparation method of battery

Abstract

The invention relates to the technical field of all-vanadium redox flow batteries, and discloses a supported electrolyte of all-vanadium redox flow battery positive and negative electrolyte and a preparation method thereof, and the supported electrolyte comprises an aqueous solution containing vanadium ions, sulfonate ions, sulfate ions and phosphonic acid groups. The sulfonic acid group (-SO3H) has strong polarity and high ionization degree, after the sulfonic acid group (-SO3H) is mixed with the phosphonic acid group (-PO3H2) and sulfuric acid, the ionic environment of the electrolyte can be optimized, the activation energy of V (II) / V (III) and V (IV) / V (V) electricity on electron transfer is reduced, and compared with an existing sulfuric acid supported electrolyte, the reversibility of electrochemical reaction is remarkably improved, and the electrochemical activity of the electrolyte is enhanced; meanwhile, phosphonic acid groups have high complexing ability, can form stable chelates with vanadium ions and can form complexing-dispersing synergy with sulfonic acid groups, the solubility of the vanadium ions is improved, and agglomeration and crystallization of the vanadium ions are inhibited.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of all-vanadium redox flow batteries, and particularly relates to a supporting electrolyte for positive and negative electrolyte of an all-vanadium redox flow battery, and especially relates to application of a mixed acid of 1-propanesulfonic acid, hydroxyethylidene diphosphonic acid and sulfuric acid in the positive and negative electrolyte of the all-vanadium redox flow battery. BACKGROUND

[0002] As a high-efficiency and safe energy storage device, the all-vanadium redox flow battery has a wide application prospect in the fields of renewable energy consumption and smart grid construction, and the performance of the supporting electrolyte of the electrolyte directly determines the charge-discharge efficiency, applicable environment and energy storage capacity of the battery. At present, the industry uses single sulfuric acid or single sulfuric acid + organic acid as the supporting electrolyte, which can provide certain ion conduction capacity, but in actual application, many defects that are difficult to avoid are exposed, which becomes a key bottleneck restricting the large-scale development of the all-vanadium redox flow battery.

[0003] The supporting electrolyte system of sulfuric acid has problems of poor electrochemical reaction reversibility and high viscosity: the resistance of the electron transfer process of V(II) / V(III) and V(IV) / V(V) is large, the reaction reversibility is low, and the electrochemical activity of the electrolyte and the charge-discharge efficiency of the battery are directly affected; at the same time, the high viscosity characteristic increases the migration resistance of vanadium ions, not only reduces the ion conduction efficiency, but also delays the dynamic response speed of the battery, which is difficult to meet the demand of efficient energy storage, and the existing technology improves it by adding sulfonic acid-based substances, but it is still difficult to meet the current high demand.

[0004] In addition, the improved electrolyte system is still prone to vanadium ion crystallization in a low-temperature environment, which blocks the flow channel of the battery; the stability of the electrolyte decreases at high temperature, which also causes the crystallization problem, so that it can only work in a narrow temperature range of 0℃-40℃, and cannot adapt to extreme climate areas; and limited by the solubility and stability, the energy density of the electrolyte is low, which cannot meet the demand of the development of the all-vanadium redox flow battery in the direction of high capacity and high energy storage density. SUMMARY

[0005] The present application aims at the problems of poor electrochemical reaction reversibility, narrow working temperature range, high viscosity of the electrolyte and low vanadium ion concentration leading to insufficient energy density of the existing supporting electrolyte of the all-vanadium redox flow battery, overcomes the limitations that the supporting electrolyte cannot balance the electrochemical activity, environmental adaptability and energy storage performance of the battery, and realizes the effects of optimizing the charge-discharge efficiency, environmental adaptability and energy storage capacity of the all-vanadium redox flow battery.

[0006] According to the above idea, the technical scheme adopted by the present application is: According to the first aspect of the embodiment of the present application, a supporting electrolyte for positive and negative electrolyte of an all-vanadium redox flow battery is provided, which comprises an aqueous solution containing vanadium ions, sulfonic acid ions, sulfate ions and phosphonic acid groups.

[0007] Optionally, the sulfonate ions are provided by at least one of 1-propanesulfonic acid, methylsulfonic acid and sulfamic acid.

[0008] Optionally, the phosphonate groups are provided by at least one of hydroxyethylidene diphosphonic acid, amino-tris-methylene phosphonic acid and ethylenediamine tetra-methylene phosphonic acid.

[0009] Preferably, the concentration of the sulfonate ions is 0.5-1.0 mol / L.

[0010] Preferably, the concentration of the phosphonate groups is 0.2-1.0 mol / L.

[0011] Preferably, the concentration of the vanadium ions is 1.0-3.0 mol / L.

[0012] Preferably, the concentration of the sulfate ions is 1.0-3.0 mol / L.

[0013] According to a second aspect of the embodiments of the present application, a preparation method of a vanadium redox flow battery is provided, comprising the following steps: S1, support electrolyte preparation A phosphonate group solution is added into a solution containing sulfonate ions, a sulfuric acid solution is added, stirred uniformly, and water is added to constant volume, to obtain a mixed acid support electrolyte of 1-propanesulfonic acid, hydroxyethylidene diphosphonic acid and sulfuric acid; S2, positive electrolyte preparation VOSO4 powder is added into the above mixed acid support electrolyte, stirred until completely dissolved, to prepare a vanadium ion positive electrolyte containing V(IV) / V(V) electric pairs; S3, negative electrolyte preparation Another identical mixed acid support electrolyte is prepared, V2(SO4)3 powder is added, to prepare a vanadium ion negative electrolyte containing V(II) / V(III) electric pairs; S4, battery assembly The above positive and negative electrolytes are respectively injected into the positive and negative chambers of a vanadium redox flow battery, graphite felt is used as an electrode, and Nafion117 film is used as an ion exchange film, to form the vanadium redox flow battery.

[0014] According to a third aspect of the embodiments of the present application, a vanadium redox flow battery is provided.

[0015] Preferably, the electrolyte of the vanadium redox flow battery is stable in a temperature range of-18℃ to 58℃.

[0016] The present application has the following advantages: 1. The sulfonic acid group (-SO3H) of this invention has strong polarity and high ionization. When mixed with phosphonic acid group (-PO3H2) and sulfuric acid, it can optimize the ionic environment of the electrolyte, reduce the activation energy of electron transfer of V(II) / V(III) and V(IV) / V(V) pairs, significantly improve the reversibility of electrochemical reactions, and enhance the electrochemical activity of the electrolyte.

[0017] 2. The phosphonic acid group (-PO3H2) of the present invention has a strong complexing ability, which can form a stable chelate with vanadium ions and form a "complexing-dispersion" synergy with sulfonic acid groups, thereby improving the solubility of vanadium ions and inhibiting their aggregation and crystallization. At the same time, the ionic strength of the mixed acid system is higher than that of the existing sulfuric acid system, which can inhibit the nucleation and growth of crystals at low temperatures and enhance the stability of the electrolyte at high temperatures, thus delaying the hydrolysis and precipitation of vanadium ions. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the charging of the vanadium redox flow battery of the present invention.

[0019] Figure 2 This is a schematic diagram of the discharge of the vanadium redox flow battery of the present invention. Detailed Implementation

[0020] 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.

[0021] 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.

[0022] like Figure 1 and Figure 2 As shown, the present invention comprises an aqueous solution containing vanadium ions, sulfonate ions, sulfate ions and phosphonic acid groups.

[0023] Example 1 A mixed acid electrolyte consisting of 1-propanesulfonic acid (0.5 mol / L), hydroxyethylidene diphosphonic acid (0.3 mol / L), and sulfuric acid (1.5 mol / L) is used.

[0024] Electrolyte preparation: Take 250 mL of 2 mol / L 1-propanesulfonic acid solution, add 300 mL of 1 mol / L hydroxyethylidene diphosphonic acid solution, add 300 mL of 5 mol / L sulfuric acid solution, stir well, and add water to make up to 1000 mL to obtain a mixed acid supporting electrolyte of 1-propanesulfonic acid (0.5 mol / L), hydroxyethylidene diphosphonic acid (0.3 mol / L), and sulfuric acid (1.5 mol / L).

[0025] Preparation of positive electrode electrolyte: In the above mixed acid supported electrolyte, 326g of VOSO4 powder was added and stirred until completely dissolved to prepare a positive electrode electrolyte with a vanadium ion concentration of 2.0 mol / L (containing V(IV) / V(V) redox couple). Preparation of negative electrode electrolyte: Take another mixed acid supporting electrolyte, add 390g of V2(SO4)3 powder, and prepare a negative electrode electrolyte with a vanadium ion concentration of 2.0mol / L (containing V(II) / V(III) redox couple). Battery assembly: The above-mentioned positive and negative electrolytes were injected into the positive and negative electrode chambers of the vanadium redox flow battery, respectively. Graphite felt was used as the electrode and Nafion 117 membrane was used as the ion exchange membrane. Charge and discharge tests were conducted at 25°C.

[0026] Example 2 Everything else is the same as in Example 1, except that: Take 250 mL of 4 mol / L 1-propanesulfonic acid solution, add 250 mL of 2 mol / L hydroxyethylidene diphosphonic acid solution, add 500 mL of 6 mol / L sulfuric acid solution, stir well, and add water to make up to 1000 mL to obtain a mixed acid supporting electrolyte of 1-propanesulfonic acid (1.0 mol / L), hydroxyethylidene diphosphonic acid (0.5 mol / L), and sulfuric acid (3.0 mol / L).

[0027] 489 g of VOSO4 was added to the positive electrode solution and 585 g of V2(SO4)3 powder was added to the negative electrode solution to prepare positive and negative electrode electrolytes with vanadium ion concentrations of 3.0 mol / L, respectively.

[0028] Example 3 Everything else is the same as in Example 1, except that: Take 250 mL of 2 mol / L 1-propanesulfonic acid solution, add 200 mL of 1 mol / L hydroxyethylidene diphosphonic acid solution, add 500 mL of 2 mol / L sulfuric acid solution, stir well, and add water to make up to 1000 mL to obtain a mixed acid-supported electrolyte of 1-propanesulfonic acid (0.5 mol / L), hydroxyethylidene diphosphonic acid (0.2 mol / L), and sulfuric acid (1.0 mol / L).

[0029] 163g of VOSO4 was added to the positive electrode solution and 195g of V2(SO4)3 powder was added to the negative electrode solution to prepare positive and negative electrode electrolytes with vanadium ion concentrations of 1.0 mol / L, respectively.

[0030] Comparative Example 1 Everything else is the same as in Example 1, except that: Hydroxyethylidene diphosphonic acid is not added in the preparation of the supporting electrolyte.

[0031] Comparative Example 2 Everything else is the same as in Example 1, except that: 1-Propanesulfonic acid is not added during the preparation of the supporting electrolyte.

[0032] Comparative Example 3 Everything else is the same as in Example 1, except that: 1-Propanesulfonic acid and hydroxyethylidene diphosphonic acid are not added in the preparation of the supporting electrolyte.

[0033] Comparative Example 4 Everything else is the same as in Example 1, except that: The hydroxyethylidene diphosphonic acid in the electrolyte formulation is replaced with citric acid. Comparative Example 5 Everything else is the same as in Example 1, except that: In the preparation of the supporting electrolyte, hydroxyethylidene diphosphonic acid was replaced with tartaric acid.

[0034] Table 1. Effects of different electrolytes on battery performance

[0035] The sulfonic acid group (-SO3H) of 1-propanesulfonic acid has strong polarity and high ionization. When mixed with sulfuric acid, it can optimize the ionic environment of the electrolyte and reduce the activation energy of electron transfer in V(II) / V(III) and V(IV) / V(V) pairs. At the same time, hydroxyethylidene diphosphonic acid, as an organophosphonic acid, has a strong complexing ability with its phosphonic acid group (-PO3H2). It can form a stable chelate with vanadium ions and can also form a "complexation-dispersion" synergy with the sulfonic acid group of 1-propanesulfonic acid, which can improve the solubility of vanadium ions and jointly inhibit their aggregation and crystallization, as well as the nucleation and growth of crystals at low temperatures.

[0036] Phosphonic acid (-PO3H2) is a polydentate ligand that can form a stable chelate with vanadium ions (V(IV) / V(III)), preventing vanadium ions from freely detaching from the chelate structure and thus losing the ability to form ordered crystal nuclei with other vanadium ions, sulfate ions, etc. Simultaneously, sulfonic acid (-SO3H) has strong polarity, forming a "charge barrier" on the surface of the phosphonic acid-vanadium chelate through electrostatic repulsion, preventing the chelate from agglomerating into "large aggregates" due to intermolecular forces. In Comparative Example 3, the crystallization temperature of monosulfonic acid is 0℃. When 1-propanesulfonic acid is added to the monosulfonic acid solution, the crystallization temperature decreases by 5℃. The supporting electrolyte obtained from the mixed acid solution of 1-propanesulfonic acid, hydroxyethylidene diphosphonic acid and sulfuric acid in Example 1 has a crystallization temperature of -15°C in the battery, while the crystallization temperature in Example 2 is -18°C and the crystallization temperature in Example 3 is -12°C. These temperatures are all much lower than the 0°C of sulfuric acid alone in Comparative Example 3 and the -2°C to -3°C in Comparative Examples 4-5. This demonstrates that the mixed acid system of the present invention can lower the stable low-temperature operating range and is irreplaceable.

[0037] Example 1 has an energy density of 35 Wh / L, Example 2 reaches 42 Wh / L, and Example 3 has an energy density of 30 Wh / L. Compared with 22 Wh / L in Comparative Example 3, the energy density is nearly doubled. This is because the phosphonic acid group of hydroxyethylidene diphosphonic acid forms a stable chelate with vanadium ions in the mixed acid system. At the same time, the mixed acid solution has a lower viscosity. Combined with the dispersing effect of the sulfonic acid group of 1-propanesulfonic acid, the vanadium ion concentration is kept at a high level and the migration resistance is low, so higher energy efficiency can be obtained.

[0038] The ionic strength of the mixed acid system is higher than that of the single sulfuric acid system, which can enhance the stability of the electrolyte at high temperatures, so that precipitation only occurs in Example 2 when the temperature reaches 58°C.

[0039] Working principle: Charging process: Under the action of an external power source, V(IV) ions in the positive electrode electrolyte lose electrons at the surface of the positive electrode and are oxidized to V(V) ions; V(III) ions in the negative electrode electrolyte gain electrons at the surface of the negative electrode and are reduced to V(II) ions; simultaneously, H+ in the mixed acid support electrolyte... + The charge migrates from the positive electrode chamber to the negative electrode chamber through the ion exchange membrane, maintaining the internal charge balance of the battery.

[0040] Discharge process: When the battery supplies power, V(V) ions in the positive electrode electrolyte gain electrons at the positive electrode surface and are reduced to V(IV) ions; V(II) ions in the negative electrode electrolyte lose electrons at the negative electrode surface and are oxidized to V(III) ions; H + Charge transfer is completed by the ion exchange membrane, which allows the charge to migrate from the negative electrode chamber to the positive electrode chamber.

[0041] Supporting electrolyte function: The mixed acid system of 1-propanesulfonic acid, hydroxyethylidene diphosphonic acid, and sulfuric acid provides a high concentration of H₂O throughout the entire charge and discharge process. + On the one hand, it ensures ion conduction; on the other hand, through its own structural characteristics, it optimizes the existence environment of vanadium ions, improves the reversibility of redox reactions, inhibits crystallization, and ensures stable and efficient operation of the battery.

[0042] 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.

[0043] 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. A supporting electrolyte for the positive and negative electrode electrolytes of an all-vanadium redox flow battery, characterized in that, This includes aqueous solutions containing vanadium ions, sulfonate ions, sulfate ions, and phosphonic acid groups.

2. The supporting electrolyte for the positive and negative electrode electrolytes of a vanadium redox flow battery according to claim 1, characterized in that, The sulfonate ion is provided by at least one of 1-propanesulfonic acid, methanesulfonic acid, and aminosulfonic acid.

3. The supporting electrolyte for the positive and negative electrode electrolytes of a vanadium redox flow battery according to claim 1, characterized in that, The phosphonic acid group includes at least one selected from hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, and ethylenediaminetetramethylene phosphonic acid.

4. The supporting electrolyte for the positive and negative electrode electrolytes of a vanadium redox flow battery according to claim 1, characterized in that, The concentration of the sulfonate ions is 0.5~1.0 mol / L.

5. The supporting electrolyte for the positive and negative electrode electrolytes of a vanadium redox flow battery according to claim 1, characterized in that, The concentration of the phosphonic acid group is 0.2~1.0 mol / L.

6. The supporting electrolyte for the positive and negative electrode electrolytes of a vanadium redox flow battery according to claim 1, characterized in that, The vanadium ion concentration is 1.0~3.0 mol / L.

7. The supporting electrolyte for the positive and negative electrode electrolytes of a vanadium redox flow battery according to claim 1, characterized in that, The concentration of sulfate ions is 1.0~3.0 mol / L.

8. A method for preparing a battery using the supporting electrolyte of the positive and negative electrode electrolytes of the all-vanadium redox flow battery according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1, Preparation of Supporting Electrolyte Phosphonic acid solution and sulfuric acid solution are added to a solution containing sulfonate ions, stirred evenly, and then diluted with water to obtain a mixed acid-supported electrolyte of 1-propanesulfonic acid, hydroxyethylidene diphosphonic acid and sulfuric acid. S2, Preparation of positive electrode electrolyte VOSO4 powder was added to the above mixed acid supported electrolyte and stirred until completely dissolved to prepare a vanadium ion positive electrode electrolyte containing V(IV) / V(V) redox couple. S3, Preparation of negative electrode electrolyte Take another mixed acid-supported electrolyte, add V2(SO4)3 powder, and prepare a vanadium ion negative electrode electrolyte containing V(II) / V(III) redox couple; S4, Battery Assembly The above-mentioned positive and negative electrolytes are injected into the positive and negative electrode chambers of the vanadium redox flow battery, respectively. Graphite felt is used as the electrode and Nafion 117 membrane is used as the ion exchange membrane to form the vanadium redox flow battery.

9. The application of the supporting electrolyte according to any one of claims 1 to 7 in a vanadium redox flow battery.

10. The application according to claim 9, characterized in that, The stable operating temperature range of the vanadium redox flow battery is -18℃ to 58℃.

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