A precursor for sulfuric acid-based energy storage medium in vanadium redox flow batteries, its preparation method and application

Abstract

This invention belongs to the field of vanadium redox flow batteries, specifically relating to a sulfuric acid-based energy storage medium precursor for vanadium redox flow batteries, its preparation method, and its application. A method for preparing a sulfuric acid-based energy storage medium precursor for vanadium redox flow batteries includes the following steps: mixing ammonium metavanadate and a sulfiding agent at a mass ratio of 0.8 to 1:1 to obtain a mixture; then dissolving the mixture in a sulfuric acid solution to prepare a mixed acid energy storage medium precursor for vanadium redox flow batteries. This preparation method is simple, convenient, and low-cost. It employs a high-temperature solid-state method to synthesize the desired low-valence vanadium sulfide solid powder in one step. By adjusting the reaction conditions, mixtures of different low-valence vanadium sulfides in different proportions can be prepared, suitable for subsequent preparation of mixed acid energy storage media for vanadium redox flow batteries.

Description

Technical Field

[0001] This invention belongs to the field of vanadium redox flow batteries, specifically relating to a sulfuric acid-based energy storage medium precursor for vanadium redox flow batteries, its preparation method, and its application. Background Technology

[0002] All-vanadium redox flow batteries (VFBs) are a novel type of pollution-free chemical energy storage power source, characterized by long lifespan, deep charge / discharge capability, and ease of operation and maintenance. VFBs are primarily used in energy storage systems for large-scale renewable energy generation such as wind and solar power, as well as in power plant peak shaving and load balancing. The electrolyte is the active material in the electrochemical reaction of VFBs and the carrier of electrical energy; its quality directly determines the energy storage capacity of the VFB. Depending on the application configuration, the cost of the electrolyte can account for 30% to 60% of the energy storage system cost. Therefore, finding an effective method for preparing the electrolyte and reducing the production cost of VFBs is crucial for accelerating their commercialization and practical application. VFBs use sulfuric acid solutions of vanadium ions in different valence states as electrolytes. Typically, the positive electrode electrolyte uses a tetravalent vanadium ion solution, which is oxidized to a pentavalent vanadium ion solution during charging; the negative electrode electrolyte uses a trivalent vanadium ion solution, which is reduced to a divalent vanadium ion solution during charging. Therefore, the preparation of trivalent and tetravalent vanadium ion solutions is critical for practical field operations.

[0003] However, V₂O₅ has very low solubility in water and is also difficult to dissolve in acids. Therefore, sulfuric acid solution cannot be directly used as the electrolyte for VFB (vanadium flavonoids). It requires reduction treatment, mainly through chemical reduction and electrolytic reduction. The chemical method primarily uses vanadium oxides or other vanadium salts as raw materials. These are heated in a sulfuric acid solution of a certain concentration, and a reducing agent (such as S, SO₂, etc.) is added to dissolve and reduce them to a low-valence, easily soluble vanadium compound, thus producing a vanadium electrolyte of a certain concentration. The advantage of the chemical synthesis method is its simple production equipment, but the solid dissolves slowly, and the added reducing agent remains in the vanadium electrolyte, which is difficult to remove, affecting the purity and performance of the vanadium electrolyte. The electrolytic reduction method overcomes the disadvantages of the chemical method, but because of the low solubility of V₂O₅ powder, the initial electrolyte is a slurry, resulting in low initial electrolyte concentration and easy precipitation.

[0004] In summary, existing methods all involve dissolving V₂O₅ in sulfuric acid solution to form a low-valence vanadium ion acid solution through chemical or electrolytic methods, ultimately producing an all-vanadium redox flow battery energy storage medium. However, V₂O₅ dissolved in sulfuric acid solution cannot be reduced to low-valence ions at higher temperatures, resulting in low reduction efficiency. Therefore, there is an urgent need for a sulfuric acid-based energy storage medium for all-vanadium redox flow batteries, its preparation method, and its applications. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a sulfuric acid-based energy storage medium precursor for vanadium redox flow batteries, comprising the following steps:

[0006] Ammonium metavanadate with a mass ratio of 0.8 to 1:1 was mixed with a sulfiding agent to obtain a mixture. The mixture was then dissolved in sulfuric acid solution to prepare a precursor for a vanadium redox flow battery mixed acid energy storage medium.

[0007] Furthermore, the temperature during the mixing process is 700-1200℃.

[0008] Furthermore, the reaction time during the mixing process is 1-2 hours.

[0009] Furthermore, the vulcanizing agent is any one of sulfur, thioacetamide, or organic or inorganic sulfur-containing substances.

[0010] Furthermore, the atmosphere for the mixed reaction is either argon or nitrogen.

[0011] Furthermore, the sulfuric acid solution is 3-5M.

[0012] A precursor for a sulfuric acid-based energy storage medium in vanadium redox flow batteries.

[0013] Application of a sulfuric acid-based energy storage medium precursor for vanadium redox flow batteries, wherein the precursor is used in the preparation of vanadium redox flow batteries.

[0014] Beneficial effects

[0015] (1) The present invention provides a method for preparing a sulfuric acid-based energy storage medium precursor for vanadium redox flow batteries. This method is simple, convenient and low in cost. The method uses a high-temperature solid-state method to synthesize the required low-valence vanadium sulfide solid powder in one step. By adjusting the reaction conditions, different proportions of different low-valence vanadium sulfide mixtures can be prepared, which are suitable for the subsequent configuration of mixed acid energy storage medium for vanadium redox flow batteries. The method uses vanadium sulfide as an electrolyte precursor. After dissolving in sulfuric acid, the reducing properties of sulfur ions can be used to further reduce high-valence vanadium ions, making it more suitable for use as an energy storage medium in vanadium redox flow batteries. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] In the picture:

[0018] Figure 1 The XRD patterns of the precursors obtained in Examples 1-5 of this invention are shown below.

[0019] Figure 2 These are morphological diagrams of embodiments 1 to 5 of the present invention;

[0020] Figure 3 This is a performance diagram of Embodiment 1 of the present invention;

[0021] Figure 4 This is a performance diagram of Embodiment 2 of the present invention;

[0022] Figure 5 This is a performance diagram of Embodiment 3 of the present invention;

[0023] Figure 6 This is a performance diagram of Embodiment 4 of the present invention;

[0024] Figure 7 This is a performance diagram of Embodiment 5 of the present invention. Detailed Implementation

[0025] The following will describe in conjunction with embodiments 1 to 5 of the present invention and the appendix. Figures 1-7 The technical solutions of the present invention have been clearly and completely described. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] 9.5g of ammonium metavanadate powder and 10g of elemental sulfur were mixed to obtain a mixture. The mixture was reacted at 1000℃ under argon gas protection for 1 hour. After cooling to room temperature, it was taken out and dissolved in 3M sulfuric acid solution to prepare a precursor for a vanadium redox flow battery energy storage medium with a total vanadium ion concentration of 1.6M.

[0028] A vanadium redox flow battery was assembled using this solution for performance testing to evaluate the electrolyte performance. The vanadium redox flow battery test conditions were as follows: positive and negative electrodes were 800 cm⁻¹. 2 The carbon felt electrode uses the prepared solution for both positive and negative electrodes, and operates at 80 mA / cm². 2 The current density is used for charge-discharge cycles, with the charging cut-off condition being a voltage not higher than 1.5V and the discharging cut-off condition being a voltage not lower than 0.1V.

[0029] Example 2

[0030] 8g of ammonium metavanadate powder and 10g of elemental sulfur were mixed to obtain a mixture. The mixture was reacted at 1000℃ under argon gas protection for 2 hours. After cooling to room temperature, it was taken out and dissolved in 4M sulfuric acid solution to prepare a vanadium redox flow battery mixed acid energy storage medium precursor with a total vanadium ion concentration of 1.6M.

[0031] A vanadium redox flow battery was assembled using this solution for performance testing to evaluate the electrolyte performance. The vanadium redox flow battery test conditions were as follows: positive and negative electrodes were 800 cm⁻¹. 2 The carbon felt electrode uses the prepared solution for both positive and negative electrodes, and operates at 80 mA / cm². 2 The current density is used for charge-discharge cycles, with the charging cut-off condition being a voltage not higher than 1.5V and the discharging cut-off condition being a voltage not lower than 0.1V.

[0032] Example 3

[0033] 10g of ammonium metavanadate powder and 10g of thioacetamide were mixed to obtain a mixture. The mixture was reacted at 1200℃ under nitrogen protection for 1 hour. After cooling to room temperature, it was taken out and dissolved in 4M sulfuric acid solution to prepare a vanadium redox flow battery mixed acid energy storage medium precursor with a total vanadium ion concentration of 1.6M.

[0034] A vanadium redox flow battery was assembled using this solution for performance testing to evaluate the electrolyte performance. The vanadium redox flow battery test conditions were as follows: positive and negative electrodes were 800 cm⁻¹. 2 The carbon felt electrode uses the prepared solution for both positive and negative electrodes, and operates at 80 mA / cm². 2 The current density is used for charge-discharge cycles, with the charging cut-off condition being a voltage not higher than 1.5V and the discharging cut-off condition being a voltage not lower than 0.1V.

[0035] Example 4

[0036] 9g of ammonium metavanadate powder and 10g of sulfur were mixed to obtain a mixture. The mixture was reacted at 800℃ under argon gas protection for 1.5h. After cooling to room temperature, it was taken out and dissolved in 5M sulfuric acid solution to prepare a vanadium redox flow battery mixed acid energy storage medium precursor with a total vanadium ion concentration of 1.6M.

[0037] A vanadium redox flow battery was assembled using this solution for performance testing to evaluate the electrolyte performance. The vanadium redox flow battery test conditions were as follows: positive and negative electrodes were 800 cm⁻¹. 2 The carbon felt electrode uses the prepared solution for both positive and negative electrodes, and operates at 80 mA / cm². 2 The current density is used for charge-discharge cycles, with the charging cut-off condition being a voltage not higher than 1.5V and the discharging cut-off condition being a voltage not lower than 0.1V.

[0038] Example 5

[0039] 15g of ammonium metavanadate powder and 15g of thioacetamide were mixed to obtain a mixture. The mixture was reacted at 1200℃ under nitrogen protection for 2 hours. After cooling to room temperature, it was taken out and dissolved in 4M sulfuric acid solution to prepare a vanadium redox flow battery mixed acid energy storage medium precursor with a total vanadium ion concentration of 1.6M.

[0040] A vanadium redox flow battery was assembled using this solution for performance testing to evaluate the electrolyte performance. The vanadium redox flow battery test conditions were: positive and negative electrodes 36cm apart. 2 The carbon felt electrode uses the prepared solution for both positive and negative electrodes, and operates at 80 mA / cm². 2 The battery was subjected to charge-discharge cycles at a current density of [value missing]. The charging cutoff condition was a voltage not exceeding 1.5V, and the discharging cutoff condition was a voltage not falling below 0.1V. Table 1 shows the total vanadium, vanadium ion ratio, and sulfate ion concentration in the solution. Table 2 shows a comparison of battery performance.

[0041] Table 1. Total Vanadium, Vanadium Ion Ratio, and Sulfate Ion Concentration

[0042]

[0043] Table 2 is a performance comparison table.

[0044]

[0045] from Figure 1 As can be seen from (ae), although the composition and ratio of each substance in each embodiment are different, the solid powder produced after sintering is vanadium sulfide. Moreover, the XRD peak intensity of the sintered product is slightly different according to the composition, indicating that the valence state composition of vanadium is different. Figure 2 (ae) shows the morphology of the solid powders after sintering in each embodiment, which are largely similar and all are cubic. Meanwhile, according to the parameters such as vanadium ion concentration in Table 1, the total vanadium concentration is generally around 1.6 M, and the proportions of trivalent and tetravalent vanadium ions are both around 1. The sulfate concentration is stable at around 2 M, all consistent with the expected preparation. This is based on... Figure 3-7 The battery performance parameters obtained from the battery cycle performance test are shown in Table 2. The data in Table 2 show that the mixed acid energy storage medium synthesized by adding a chlorinating agent and applied to vanadium redox flow batteries can achieve high coulombic efficiency and energy efficiency.

[0046] This invention provides a method for preparing a sulfuric acid-based energy storage medium precursor for vanadium redox flow batteries. It utilizes a one-step high-temperature solid-state method to synthesize low-valence vanadium sulfide solid powder, avoiding complex synthesis steps, making the production process more efficient and easier to control, and reducing operational risks. By adjusting the reaction conditions, mixtures of low-valence vanadium sulfides in different proportions can be prepared, providing a wide range of choices for the energy storage medium configuration of subsequent vanadium redox flow batteries, adapting to different battery performance requirements. Using vanadium sulfide as an electrolyte precursor, its reducing properties after dissolving in sulfuric acid can further reduce high-valence vanadium ions. This process not only improves the battery's charge-discharge efficiency but also enhances its cycle stability and extends its service life. The electrolyte preparation route proposed in this invention is relatively inexpensive, utilizing abundant raw materials, significantly reducing the production cost of vanadium redox flow batteries, and promoting its widespread adoption in large-scale energy storage applications. This invention not only provides a new material basis and technical route for the high-efficiency energy storage of vanadium redox flow batteries but also provides important reference and guidance for research and application in related fields, possessing promising market prospects.

Claims

1. A method for preparing a sulfuric acid-based energy storage medium precursor for an all-vanadium redox flow battery, characterized in that, Includes the following steps: Ammonium metavanadate and a sulfiding agent are mixed at a mass ratio of 0.8 to 1:1, sintered, and then dissolved in sulfuric acid solution to prepare a vanadium redox flow battery hybrid acid energy storage medium precursor. The mixing process is carried out at a temperature of 700-1200 °C. The sulfiding agent is any one of sulfur, thioacetamide, or elemental sulfur. The vanadium ions in the vanadium redox flow battery hybrid acid energy storage medium precursor are V0.

05. 3+ and VO 2+ .

2. The method for preparing a sulfuric acid-based energy storage medium precursor for an all-vanadium redox flow battery according to claim 1, characterized in that, The reaction time during the mixing process is 1-2 hours.

3. The method for preparing a sulfuric acid-based energy storage medium precursor for an all-vanadium redox flow battery according to claim 1, characterized in that, The atmosphere for the mixed reaction is either argon or nitrogen.

4. The method for preparing a sulfuric acid-based energy storage medium precursor for an all-vanadium redox flow battery according to claim 1, characterized in that, The sulfuric acid solution is 3-5 M.

5. A vanadium redox flow battery sulfuric acid-based energy storage medium precursor obtained by any of the preparation methods described in claims 1 to 4.

6. The application of the sulfuric acid-based energy storage medium precursor for an all-vanadium redox flow battery according to claim 5, characterized in that, The precursor is used in the preparation of all-vanadium redox flow batteries.

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