Tetravalent vanadium electrolyte, preparation method thereof and battery

Abstract

The invention relates to a tetravalent vanadium electrolyte, a preparation method thereof and a battery, and the method comprises the following steps: S1, mixing vanadium pentoxide with a sulfuric acid solution to obtain a first mixture; and S2, in an inert atmosphere, enabling the first mixture to be in contact with reducing sugar for a reduction reaction. The method disclosed by the invention is simple in process, and the high-stability tetravalent vanadium electrolyte can be prepared.

Description

Technical Field

[0001] This application relates to a tetravalent vanadium electrolyte, its preparation method, and a battery. Background Technology

[0002] Vanadium battery technology is an advanced energy storage solution that stores and releases electrical energy based on the redox reactions of vanadium ions in different valence states. It utilizes the multiple valence states of vanadium circulating in a sulfuric acid electrolyte, achieving energy conversion and storage through electrochemical reactions on the electrode surface. Vanadium battery technology features high safety, long lifespan, easy scalability, and environmental friendliness. Its electrolyte ions exist in an aqueous solution, avoiding the risks of thermal runaway, combustion, and explosion. Furthermore, the battery stack and electrolyte are independent, allowing for increased storage capacity by increasing stack power and electrolyte volume, facilitating expansion into large-scale energy storage systems. In addition, vanadium batteries exhibit excellent cycle life and overall lifespan, and their materials are easily recyclable, resulting in low total lifespan costs.

[0003] Current mainstream vanadium battery electrolytes suffer from poor stability and complex preparation processes, especially when using vanadium pentoxide as the vanadium source. There are generally two methods for producing vanadium electrolytes using vanadium pentoxide as a raw material: the electrolytic cell reduction method and the chemical reduction method. The electrolytic cell reduction method involves placing a mixture of vanadium pentoxide and sulfuric acid solution at the negative electrode of an electrolytic cell, adding a sulfuric acid solution with the same acidity as the mixture at the positive electrode, and then electrolyzing the mixture to obtain the electrolyte. This method is inefficient and struggles to produce electrolytes with high stability. The chemical reduction method typically involves adding reducing agents such as oxalic acid or hydrogen peroxide to the vanadium pentoxide and sulfuric acid mixture, or introducing reducing gases such as hydrogen, carbon monoxide, or sulfur dioxide to chemically reduce pentavalent vanadium to tetravalent vanadium. However, even slight residues of the reducing agents used in these methods can degrade electrolyte performance, and the reducing gases used are often flammable or toxic, making industrial-scale production impractical and difficult to achieve with high stability. Summary of the Invention

[0004] The purpose of this disclosure is to provide a tetravalent vanadium electrolyte, its preparation method, and a battery. The method disclosed herein is simple and can prepare a highly stable tetravalent vanadium electrolyte.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a method for preparing a tetravalent vanadium electrolyte, the method comprising: S1. Vanadium pentoxide is mixed with sulfuric acid solution to obtain the first mixture; S2. In an inert atmosphere, the first mixture is brought into contact with reducing sugar to carry out a reduction reaction.

[0006] Optionally, in step S1, the concentration of the sulfuric acid solution is 2.0-8.0 mol / L, preferably 4.0-6.0 mol / L; relative to 1L of the sulfuric acid solution, the amount of vanadium pentoxide used is 45-364g, preferably 110-227g.

[0007] Optionally, the purity of the vanadium pentoxide is 98-99.5% by weight.

[0008] Optionally, in step S2, the amount of reducing sugar used is 0.5-10g, preferably 4.0-8.0g, relative to 0.1L of the first mixture.

[0009] Optionally, in step S2, the reducing sugar is selected from one or more of glucose, fructose, xylose, lactose, galactose and maltose.

[0010] Optionally, in step S2, the conditions for the reduction reaction include: a temperature of 45-70°C and a time of 5-75 min; preferably, a temperature of 50-60°C and a time of 25-45 min.

[0011] Optionally, in step S2, the inert atmosphere contains one or more of nitrogen, argon, and helium.

[0012] The second aspect of this disclosure provides a tetravalent vanadium electrolyte prepared using the method provided in the first aspect of this disclosure.

[0013] Optionally, the tetravalent vanadium electrolyte contains V 4+ Ions, SO4 2- Ions and reducing sugars.

[0014] The third aspect of this disclosure provides a battery containing a tetravalent vanadium electrolyte provided in the second aspect of this disclosure.

[0015] Through the above technical solution, the method disclosed herein uses reducing sugar as a reducing agent and stabilizer, does not use flammable or toxic reducing gases, has a simple preparation method, and produces an electrolyte with high stability.

[0016] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0017] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0018] The first aspect of this disclosure provides a method for preparing a tetravalent vanadium electrolyte, the method comprising: S1, mixing vanadium pentoxide with a sulfuric acid solution to obtain a first mixture; S2, in an inert atmosphere, contacting the first mixture with a reducing sugar to carry out a reduction reaction.

[0019] The method disclosed herein uses reducing sugars to prepare tetravalent vanadium electrolytes. The reducing sugars act as both reducing agents and stabilizers, without the need to introduce other metal impurities. This method has no effect on the pH of the electrolyte and can prepare tetravalent vanadium electrolytes with higher stability.

[0020] According to this disclosure, the concentration of the sulfuric acid solution and the amount of vanadium pentoxide can vary within a wide range. In one specific embodiment of this disclosure, in step S1, the concentration of the sulfuric acid solution is 2.0-8.0 mol / L, preferably 4.0-6.0 mol / L; relative to 1L of the sulfuric acid solution, the amount of vanadium pentoxide is 40-364g, preferably 110-227g. In the above embodiment, vanadium pentoxide can be fully activated under the action of sulfuric acid, which is beneficial for the subsequent reduction reaction to proceed more fully. In this disclosure, the sulfuric acid solution can be prepared using methods well known to those skilled in the art. For example, concentrated sulfuric acid and deionized water can be mixed at a mass ratio of 1:(1.25-5) to prepare a sulfuric acid solution with a concentration of 2.0-8.0 mol / L.

[0021] This disclosure does not impose specific limitations on the mixing temperature, which can be, for example, from -10 to 100°C. Mixing can be performed using methods well known to those skilled in the art, as long as uniform mixing is achieved, such as magnetic stirring.

[0022] According to this disclosure, the purity of vanadium pentoxide can vary within a wide range. In one specific embodiment, the purity of vanadium pentoxide is 98-99.5% by weight.

[0023] According to this disclosure, the amount of reducing sugar can vary within a wide range. In order to ensure the reduction reaction proceeds fully and the prepared electrolyte has better stability, in one specific embodiment of this disclosure, in step S2, the amount of reducing sugar is 0.5-10 g, preferably 4.0-8.0 g, relative to 0.1 L of the first mixture. In this embodiment, the appropriate amount of reducing sugar allows the reduction reaction to proceed more fully, thereby preparing a tetravalent vanadium electrolyte with higher stability.

[0024] According to this disclosure, reducing sugars can be monosaccharides containing a free aldehyde or ketone group, or disaccharides containing a free aldehyde group. In one specific embodiment of this disclosure, in step S2, the reducing sugar is selected from one or more of glucose, fructose, xylose, lactose, galactose, and maltose.

[0025] To ensure a more complete and rapid reduction reaction, in one specific embodiment of this disclosure, step S2 includes the following conditions for the reduction reaction: a temperature of 45-70°C and a time of 5-75 min; preferably, a temperature of 50-60°C and a time of 25-45 min. Under these conditions, the first mixture and the reducing sugar can undergo a sufficient reduction reaction, resulting in a tetravalent vanadium electrolyte with higher stability.

[0026] According to this disclosure, inert atmospheres are well known to those skilled in the art, and inert atmospheres may contain inert gases and / or nitrogen. In one specific embodiment, the inert atmosphere contains one or more of nitrogen, argon, and helium.

[0027] In a preferred embodiment, in step S2, the first mixture is mixed and stirred with reducing sugar to allow the reaction to proceed more rapidly and fully. This disclosure does not impose specific limitations on the stirring method; for example, a magnetic stirrer may be used.

[0028] The second aspect of this disclosure provides a tetravalent vanadium electrolyte prepared by the method provided in the first aspect of this disclosure.

[0029] In one specific embodiment of this disclosure, the tetravalent vanadium electrolyte contains V 4+ Ions, SO4 2- Ions and reducing sugars. In one embodiment, V in the tetravalent vanadium electrolyte 4+ The concentration is 0.5-4 mol / L, preferably 1-2.5 mol / L, SO4 2- The concentration of ions is 2.0-8.0 mol / L, preferably 4.0-6.0 mol / L, and the concentration of reducing sugar is 0.5-5.0 g / 100 mL. In this disclosure, the reducing sugar contained in the tetravalent vanadium electrolyte can inhibit the oxidation of tetravalent vanadium ions to pentavalent vanadium ions, thus maintaining the stability of the electrolyte composition. The tetravalent vanadium electrolyte in this disclosure also contains a solvent, which is a sulfuric acid solution.

[0030] This disclosure provides a battery in a third aspect, the battery comprising a tetravalent vanadium electrolyte provided in a second aspect of this disclosure. The battery of this disclosure has superior stability.

[0031] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0032] Unless otherwise specified, all reagents used in the following examples and comparative examples were commercially available. Vanadium pentoxide was purchased from Aladdin with a purity of 99.5% by weight.

[0033] Example 1 (1) Add 11g of vanadium pentoxide to 100mL of 4.5mol / L sulfuric acid solution and mix to obtain the first mixture; (2) Under the conditions of stirring and heating to 55°C and nitrogen protection, 5g of xylose was added to the first mixture as a reducing agent and stabilizer. After reacting for 35 minutes, tetravalent vanadium electrolyte was obtained.

[0034] Example 2 (1) Add 11g of vanadium pentoxide to 100mL of 3.0mol / L sulfuric acid solution and mix to obtain the first mixture; (2) Under the conditions of stirring and heating to 45°C and argon protection, 4.5g of glucose was added to the first mixture as a reducing agent and stabilizer. After reacting for 40min, tetravalent vanadium electrolyte was obtained.

[0035] Example 3 (1) Add 14.5g of vanadium pentoxide to 100mL of 3.8mol / L sulfuric acid solution and mix to obtain the first mixture; (2) Under the conditions of stirring and heating to 70°C and nitrogen protection, 6.5g of fructose was added to the first mixture as a reducing agent and stabilizer. After reacting for 35 minutes, tetravalent vanadium electrolyte was obtained.

[0036] Example 4 (1) Add 16.4g of vanadium pentoxide to 100mL of 3.2mol / L sulfuric acid solution and mix to obtain the first mixture; (2) Under the conditions of stirring and heating to 60°C and nitrogen protection, 7.5g of glucose was added to the first mixture as a reducing agent and stabilizer. After reacting for 38 minutes, tetravalent vanadium electrolyte was obtained.

[0037] Example 5 The tetravalent vanadium electrolyte was prepared using the same method as in Example 1, except that in step S1, 10g of vanadium pentoxide was added to 100mL of 6.5mol / L sulfuric acid solution and mixed to obtain the first mixture.

[0038] Example 6 The tetravalent vanadium electrolyte was prepared using the same method as in Example 1, except that in step S2, 3.5 g of glucose was added to the first mixture as a reducing agent and stabilizer.

[0039] Example 7 The tetravalent vanadium electrolyte was prepared using the same method as in Example 1, except that in step S2, 12g of xylose was added to the first mixture as a reducing agent and stabilizer.

[0040] Comparative Example 1 26g of vanadium oxysulfate trihydrate with a purity of 99% was dissolved in 100mL of 4.5mol / L sulfuric acid solution at room temperature and stirred until no precipitate was formed to obtain a tetravalent vanadium electrolyte.

[0041] Comparative Example 2 A mixture of 14.5 g of vanadium pentoxide and 100 mL of 3.8 mol / L sulfuric acid solution was placed at the negative electrode of an electrolytic cell. The mixture was then added to the positive electrode of the electrolytic cell. Electrolysis was performed by passing an electric current through the electrolytic cell. After 100% discharge, a tetravalent vanadium electrolyte was obtained in the positive electrode storage tank.

[0042] Test case The vanadium ion concentration in the vanadium electrolyte was determined by analyzing the liquid at a depth of 1 cm below the surface of the electrolyte after standing for different periods. The automatic potentiometric titrator used was a Model 794 automatic potentiometric titrator manufactured by Metrohm, Switzerland, and the determination method adopted was from Appendix A of GB / T37204-2018 ("Electrolytes for Vanadium Redox Flow Batteries"), "Determination of Vanadium Ion Content in Vanadium Electrolytes".

[0043] Table 1

[0044] As can be seen from the above, compared with the electrolyte prepared by directly dissolving high-purity vanadium oxysulfate hydrate in sulfuric acid solution (Comparative Example 1) and the electrolyte prepared by the reduction method in an electrolytic cell (Comparative Example 2), the tetravalent vanadium electrolyte prepared by the method of this disclosure has higher stability.

[0045] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0046] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0047] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing a tetravalent vanadium electrolyte, the method comprising: S1. Vanadium pentoxide is mixed with sulfuric acid solution to obtain the first mixture; S2. In an inert atmosphere, the first mixture is brought into contact with reducing sugar to carry out a reduction reaction.

2. The method according to claim 1, wherein, In step S1, the concentration of the sulfuric acid solution is 2.0-8.0 mol / L, preferably 4.0-6.0 mol / L; relative to 1L of the sulfuric acid solution, the amount of vanadium pentoxide used is 45-364g, preferably 110-227g.

3. The method according to claim 1, wherein, The purity of the vanadium pentoxide is 98-99.5% by weight.

4. The method according to claim 1, wherein, In step S2, the amount of reducing sugar used is 0.5-10g, preferably 4.0-8.0g, relative to 0.1L of the first mixture.

5. The method according to claim 1, wherein, In step S2, the reducing sugar is selected from one or more of glucose, fructose, xylose, lactose, galactose and maltose.

6. The method according to claim 1, wherein, In step S2, the conditions for the reduction reaction include: a temperature of 45-70°C and a time of 5-75 min; preferably, a temperature of 50-60°C and a time of 25-45 min.

7. The method according to claim 1, wherein, In step S2, the inert atmosphere contains one or more of nitrogen, argon and helium.

8. The tetravalent vanadium electrolyte prepared by the method according to any one of claims 1-7.

9. The tetravalent vanadium electrolyte according to claim 8, wherein, The tetravalent vanadium electrolyte contains V 4+ Ions, SO4 2- Ions and reducing sugars.

10. A battery comprising the tetravalent vanadium electrolyte of claim 8 or 9.

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