Sulfuric acid-based energy storage medium precursor of all-vanadium redox flow battery, preparation method and application

Abstract

The invention belongs to the field of all-vanadium redox flow batteries, and particularly relates to a sulfuric acid-based energy storage medium precursor of an all-vanadium redox flow battery as well as a preparation method and application of the sulfuric acid-based energy storage medium precursor. A preparation method of a sulfuric acid-based energy storage medium precursor of an all-vanadium redox flow battery comprises the following steps: mixing ammonium metavanadate and a vulcanizing agent in a mass ratio of (0.8-1): 1 to obtain a mixture, and then dissolving the mixture in a sulfuric acid solution to prepare a mixed acid energy storage medium precursor of the all-vanadium redox flow battery; the preparation method is simple and convenient to operate and relatively low in cost; according to the preparation method, the required low-valence vanadium sulfide solid powder is synthesized in one step by adopting a high-temperature solid-phase method, different low-valence vanadium sulfide mixtures with different proportions can be prepared by adjusting reaction conditions, and the preparation method is suitable for the subsequent preparation of the mixed acid energy storage medium of the all-vanadium redox flow battery.

Description

Technical Field

[0001] The present invention belongs to the field of all-vanadium liquid flow batteries, and in particular relates to a sulfuric acid-based energy storage medium precursor for all-vanadium liquid flow batteries, a preparation method and an application thereof. Background Art

[0002] All vanadium redox flow battery (VFB) is a new type of pollution-free chemical energy storage power source with the characteristics of long life, deep charge and discharge, easy operation and maintenance. VFB is mainly used in energy storage systems for large-scale renewable energy power generation such as wind power generation and solar power generation, as well as peak load balancing in power plants. The electrolyte is the active substance of the electrochemical reaction of VFB and the carrier of electric energy. Its quality directly determines the energy storage capacity of VFB. According to different application configurations, the cost of the electrolyte can account for 30% to 60% of the energy storage system. Therefore, it is very important to find an effective way to prepare the electrolyte and reduce the production cost of VFB to promote the commercialization and practical application of VFB. VFB uses sulfuric acid solution of vanadium ions of different valence states as electrolyte. Usually, the positive electrode electrolyte uses a tetravalent vanadium ion solution, which is oxidized to a pentavalent vanadium ion solution when charged; the negative electrode electrolyte uses a trivalent vanadium ion solution, which is reduced to a divalent vanadium ion solution when charged, so the preparation of trivalent and tetravalent vanadium ion solutions is crucial for actual field operations.

[0003] However, V2O5 has very low solubility in water and is not easily soluble in acid, so sulfuric acid solution cannot be directly used as the electrolyte of VFB. It needs to be reduced. The main methods of treatment are chemical reduction and electrolytic reduction. The chemical method mainly uses vanadium oxide or other vanadium salts as raw materials, heats them in a certain concentration of sulfuric acid solution and adds a reducing agent (such as S, SO2, etc.) to dissolve and reduce them to low-priced and soluble vanadium compounds, thereby preparing a vanadium electrolyte of a certain concentration. The advantage of the chemical synthesis method is that the production equipment is simple, but the dissolution rate of the solid is slow, and the added reducing agent will remain in the vanadium electrolyte and is difficult to eradicate, affecting the purity and performance of the vanadium electrolyte. The electrolytic reduction method can overcome the shortcomings of the chemical method, but because the solubility of V2O5 powder is low, the initial electrolyte is a slurry material, and there are problems such as low initial electrolyte concentration and easy precipitation.

[0004] In summary, the existing methods all adopt the method of dissolving V2O5 in sulfuric acid solution, and forming a low-valent vanadium ion acid solution by chemical or electrolytic methods. And finally making an all-vanadium liquid flow battery energy storage medium. However, V2O5 is dissolved in sulfuric acid solution, and it cannot be reduced to low-valent ions at a higher temperature, resulting in low reduction efficiency. Therefore, there is an urgent need for a sulfuric acid-based energy storage medium for all-vanadium liquid flow batteries, a preparation method and an application. Summary of the invention

[0005] In view of the defects of the prior art, the present invention provides a method for preparing a sulfuric acid-based energy storage medium precursor for an all-vanadium liquid flow battery, comprising the following steps:

[0006] Ammonium metavanadate and a sulfiding agent are mixed in a mass ratio of 0.8 to 1:1 to obtain a mixture, and then the mixture is dissolved in a sulfuric acid solution to obtain a mixed acid energy storage medium precursor for an all-vanadium liquid flow battery.

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

[0008] Furthermore, the reaction time in the mixing process is 1-2h.

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

[0010] Furthermore, the atmosphere of the mixed reaction is any one of argon and nitrogen.

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

[0012] A sulfuric acid-based energy storage medium precursor for all-vanadium liquid flow batteries.

[0013] The invention discloses an application of a sulfuric acid-based energy storage medium precursor for an all-vanadium liquid flow battery. The precursor is applied in the preparation of an all-vanadium liquid flow battery.

[0014] Beneficial Effects

[0015] (1) The present invention provides a method for preparing a sulfuric acid-based energy storage medium precursor for an all-vanadium liquid flow battery. The method is simple to operate, convenient and low in cost. The method uses a high-temperature solid phase method to synthesize the required low-valent vanadium sulfide solid powder in one step. By adjusting the reaction conditions, a mixture of different low-valent vanadium sulfides in different proportions can be prepared, which is suitable for the subsequent configuration of a mixed acid energy storage medium for an all-vanadium liquid flow battery. The method uses vanadium sulfide as an electrolyte precursor. After being dissolved in sulfuric acid, the reducing properties of sulfur ions can continue to be used to continue to reduce high-valent vanadium ions, making it more suitable for use as an energy storage medium for an all-vanadium liquid flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0017] In the figure:

[0018] Figure 1 The XRD diagrams of the precursors obtained in Examples 1 to 5 of the present invention;

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

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

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

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

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

[0024] Figure 7 This is a performance diagram of Example 5 of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with embodiments 1 to 5 of the present invention and the attached Figures 1 to 7 , the technical solution of the present invention is clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1

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

[0028] The solution was used to assemble an all-vanadium redox flow battery for performance testing to evaluate the performance of the electrolyte. All-vanadium redox flow battery test conditions: The positive and negative electrodes are 800 cm 2 Carbon felt electrode, positive and negative electrodes are made of the prepared solution, using 80mA / cm 2 The charge and discharge cycles are carried out at a current density of , the charge cut-off condition is that the voltage is not higher than 1.5V, and the discharge cut-off condition is that the voltage is not lower than 0.1V.

[0029] Example 2

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

[0031] The solution was used to assemble an all-vanadium redox flow battery for performance testing to evaluate the performance of the electrolyte. All-vanadium redox flow battery test conditions: The positive and negative electrodes are 800 cm 2 Carbon felt electrode, positive and negative electrodes are made of the prepared solution, using 80mA / cm 2 The charge and discharge cycles are carried out at a current density of , the charge cut-off condition is that the voltage is not higher than 1.5V, and the discharge cut-off condition is that the voltage is not lower than 0.1V.

[0032] Example 3

[0033] 10 g of ammonium metavanadate powder and 10 g of thioacetamide were mixed to obtain a mixture, and the mixture was reacted at 1200° C. under nitrogen gas protection for 1 hour, cooled to room temperature, taken out, dissolved in 4M sulfuric acid solution, and prepared into a mixed acid energy storage medium precursor for all-vanadium liquid flow battery with a total vanadium ion concentration of 1.6M.

[0034] The solution was used to assemble an all-vanadium redox flow battery for performance testing to evaluate the performance of the electrolyte. All-vanadium redox flow battery test conditions: The positive and negative electrodes are 800 cm 2 Carbon felt electrode, positive and negative electrodes are made of the prepared solution, using 80mA / cm 2 The charge and discharge cycles are carried out at a current density of , the charge cut-off condition is that the voltage is not higher than 1.5V, and the discharge cut-off condition is that the voltage is not lower than 0.1V.

[0035] Example 4

[0036] 9 g of ammonium metavanadate powder and 10 g of sulfur are mixed to obtain a mixture, and the mixture is reacted at 800° C. under argon gas protection for 1.5 hours, cooled to room temperature, taken out, dissolved in 5M sulfuric acid solution, and prepared into a mixed acid energy storage medium precursor for all-vanadium liquid flow battery with a total vanadium ion concentration of 1.6M.

[0037] The solution was used to assemble an all-vanadium redox flow battery for performance testing to evaluate the performance of the electrolyte. All-vanadium redox flow battery test conditions: The positive and negative electrodes are 800 cm 2 Carbon felt electrode, positive and negative electrodes are made of the prepared solution, using 80mA / cm 2 The charge and discharge cycles are carried out at a current density of , the charge cut-off condition is that the voltage is not higher than 1.5V, and the discharge cut-off condition is that the voltage is not lower than 0.1V.

[0038] Example 5

[0039] 15 g of ammonium metavanadate powder and 15 g of thioacetamide were mixed to obtain a mixture, and the mixture was reacted at 1200° C. under nitrogen gas protection for 2 hours, cooled to room temperature, taken out, dissolved in 4M sulfuric acid solution, and prepared into a mixed acid energy storage medium precursor for all-vanadium liquid flow battery with a total vanadium ion concentration of 1.6M.

[0040] The solution was used to assemble an all-vanadium redox flow battery for performance testing to evaluate the performance of the electrolyte. All-vanadium redox flow battery test conditions: The positive and negative electrodes are 36cm 2 Carbon felt electrode, positive and negative electrodes are made of the prepared solution, using 80mA / cm 2 The charge and discharge cycles were carried out at a current density of 1.5 V, and the cut-off condition for charging was that the voltage was not higher than 1.5 V, and the cut-off condition for discharging was that the voltage was not lower than 0.1 V. Table 1 shows the concentration of total vanadium, vanadium ion ratio, and sulfate ion in the solution. Table 2 shows the battery performance comparison table.

[0041] Table 1 Total vanadium, vanadium ion ratio, sulfate ion concentration

[0042]

[0043] Table 2 is a performance comparison table

[0044]

[0045] from Figure 1 It can be seen from (ae) that although the composition and ratio of each substance in each embodiment are different, the solid powders produced after sintering are all vanadium sulfides, and depending on the composition, the XRD peak intensities of the sintered products are slightly different, indicating that the valence composition of vanadium is different. Figure 2 (ae) shows the morphology of the solid powder after sintering in each embodiment, which is not much different, all of which are cubic. At the same time, according to the parameters such as vanadium ion concentration in Table 1, it can be found that the total vanadium concentration is basically around 1.6M, and the ratio of trivalent and tetravalent vanadium ions is around 1. The sulfate concentration is stable at around 2M, which is in line with the preparation expectations. Figure 3-7 The battery performance parameters obtained from the battery cycle performance test are shown in Table 2. From the data in Table 2, it can be found that the application of the all-vanadium liquid flow battery mixed acid energy storage medium synthesized by adding a chlorinating agent to the all-vanadium liquid flow battery can obtain higher coulombic efficiency and energy efficiency.

[0046] The present invention provides a method for preparing a sulfuric acid-based energy storage medium precursor for an all-vanadium liquid flow battery. The low-valent vanadium sulfide solid powder is synthesized in one step by a high-temperature solid phase method, which avoids complex synthesis steps, makes the production process more efficient and easy to control, and reduces the operation risk. By adjusting the reaction conditions, a low-valent vanadium sulfide mixture of different proportions can be prepared, which provides a wide range of selection space for the subsequent energy storage medium configuration of the all-vanadium liquid flow battery and adapts to different battery performance requirements. Using vanadium sulfide as an electrolyte precursor, after dissolving in sulfuric acid, the reducing properties of vanadium sulfide can further reduce high-valent vanadium ions. This process not only improves the charge and discharge efficiency of the battery, but also enhances the cycle stability of the battery and prolongs its service life. The electrolyte preparation route proposed by the present invention is relatively low-priced, and the abundant raw materials are used to significantly reduce the production cost of the all-vanadium liquid flow battery, which promotes its promotion and popularization in large-scale energy storage applications. The present invention not only provides a new material basis and technical route for the efficient energy storage of the all-vanadium liquid flow battery, but also provides important reference and reference for the research and application of related fields, and has a good market prospect.

Claims

1. A method for preparing a sulfuric acid-based energy storage medium precursor for an all-vanadium liquid flow battery, characterized in that: The following steps are involved: Ammonium metavanadate and a sulfiding agent are mixed in a mass ratio of 0.8 to 1:1, sintered to obtain a mixture, and then the mixture is dissolved in a sulfuric acid solution to obtain a precursor of a mixed acid energy storage medium for an all-vanadium liquid flow battery.

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 temperature during the mixing process is 700-1200°C.

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 reaction time in the mixing process is 1-2h.

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 vulcanizing agent is any one of sulfur, thioacetamide, organic or inorganic sulfur-containing substances.

5. 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 of the mixed reaction is any one of argon and nitrogen.

6. 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 3-5M.

7. A sulfuric acid-based energy storage medium precursor for an all-vanadium liquid flow battery obtained according to the preparation method of any one of claims 1 to 6.

8. The use of a sulfuric acid-based energy storage medium precursor for an all-vanadium redox flow battery according to claim 7, characterized in that: The precursor is used in preparing all-vanadium liquid flow batteries.

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