A vanadium redox flow battery hydrochloric acid / mixed acid-based energy storage medium precursor, a preparation method and application thereof

Abstract

The application belongs to the field of electrochemistry and particularly relates to a vanadium redox flow battery hydrochloric acid / mixed acid-based energy storage medium precursor, a preparation method and application; and a preparation method of a vanadium redox flow battery hydrochloric acid / mixed acid-based energy storage medium precursor, which comprises the following steps: mixing ammonium metavanadate with a chlorinating agent and a reducing agent, reacting under high temperature and gas atmosphere protection, and dissolving the mixture in an acid solution after cooling to obtain the vanadium redox flow battery hydrochloric acid / mixed acid-based energy storage medium precursor. The preparation process is simple in operation, energy-saving and environment-friendly, low in cost, and capable of realizing stable operation of electrolyte in the battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electrochemistry, and particularly relates to a vanadium redox flow battery hydrochloric acid / mixed acid-based energy storage medium precursor, a preparation method and application. BACKGROUND

[0002] Wind energy and solar energy are considered to be the cleanest renewable energy, but due to the influence of natural factors, continuous and stable energy cannot be obtained, and large-scale energy storage technology must be applied for adjustment. However, the backwardness of energy storage technology has become a bottleneck restricting the utilization of the two renewable energies. The vanadium redox flow battery is a new type of energy storage battery, which has the advantages of high energy conversion efficiency, long service life, convenient capacity adjustment, high safety and environmental friendliness, and can be used in the fields of renewable energy such as solar energy and wind energy, and large-scale energy storage such as peak load shifting of power grid, and is one of the most promising energy storage devices. Among them, the electrolyte as the carrier of active substances is one of the most important components in the vanadium redox flow battery, and the performance and concentration of the electrolyte directly affect the performance and energy density of the battery. How to obtain high-performance vanadium electrolyte has become a hot spot for researchers in various countries.

[0003] In recent years, hydrochloric acid and sulfuric acid as supporting electrolyte vanadium redox flow battery energy storage medium gradually replaced the pure sulfuric acid system. The system has the advantages of high power density and good energy efficiency. At present, the mixed acid system mainly uses electrolysis or chemical reduction method to first synthesize low-valence vanadium oxide, and then dissolve in the mixed solution of sulfuric acid and hydrochloric acid.

[0004] The chemical method mainly uses vanadium oxide or other vanadium salts as raw materials, heats in a certain concentration of sulfuric acid solution, and adds a reducing agent (such as S, SO2, etc.) to dissolve and reduce the low-valence vanadium compound, thereby preparing a vanadium electrolyte with a certain concentration. The advantage of the chemical synthesis method is that the production equipment is simple, but the dissolution speed of the solid is slow, and the reducing agent added will be difficult to eliminate and affect the purity and performance of the vanadium electrolyte. The electrolysis method generally uses a diaphragm electrolysis cell device, uses V2O5 or metavanadate as raw material, adds H2SO4 solution containing V2O5 or metavanadate in the negative electrode area of the electrolysis cell, and adds H2SO4 with the same concentration in the positive electrode area. A suitable direct current is applied to the two poles of the electrolysis cell, and V2O5 or metavanadate powder is reduced on the negative electrode surface by contacting with the negative electrode to prepare the electrolyte of the vanadium redox flow battery. The electrolysis method can continuously produce a large amount of high-concentration vanadium electrolyte, and has the advantages of simple operation, easy industrial production, slow reaction rate, high equipment requirement, high energy consumption and high cost.

[0005] In summary, the existing methods all adopt dissolving V2O5 in sulfuric acid or mixed solution of sulfuric acid and hydrochloric acid, forming low valence vanadium ion acid solution by chemical or electrolytic method. And finally, the energy storage medium of all-vanadium redox flow battery is prepared. In practical application, the secondary transportation of concentrated sulfuric acid and sulfuric acid electrolyte is involved, which causes great increase of cost. Moreover, the precursor synthesis and electrolyte configuration process are separated, which causes great waste of resources. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a preparation method of hydrochloric acid / mixed acid-based energy storage medium precursor for all-vanadium redox flow battery, comprising the following steps:

[0007] Ammonium metavanadate is mixed with a chlorinating agent and a reducing agent, and reacted under high temperature and gas atmosphere protection to obtain a mixture. After cooling, the mixture is dissolved in an acid solution to configure the hydrochloric acid / mixed acid-based energy storage medium precursor for all-vanadium redox flow battery.

[0008] Further, the mass ratio of the ammonium metavanadate to the reducing agent is 1:1-5.

[0009] Further, the mass ratio of the ammonium metavanadate to the chlorinating agent is 1:1-10.

[0010] Further, the reaction temperature is 800-1500℃.

[0011] Further, the reaction time is 1-4h.

[0012] Further, the reaction gas atmosphere is any one of argon and nitrogen.

[0013] Further, the acid solution is any one of sulfuric acid and hydrochloric acid.

[0014] Further, the acid solution is 3-8M.

[0015] A hydrochloric acid / mixed acid-based energy storage medium precursor for all-vanadium redox flow battery.

[0016] The application of a hydrochloric acid / mixed acid-based energy storage medium precursor for all-vanadium redox flow battery, wherein the hydrochloric acid / mixed acid-based energy storage medium precursor is applied in the preparation of all-vanadium redox flow battery.

[0017] Advantages

[0018] (1) The application provides a preparation method of a vanadium redox flow battery hydrochloric acid / mixed acid-based energy storage medium precursor. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the application, the drawings needed in the examples will be briefly introduced as follows, and it should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings

[0020] In the drawings:

[0021] Figures 1-5 XRD patterns of vanadium chlorides with different valence states according to the application;

[0022] Figures 6-10 Morphology patterns according to the application;

[0023] Figures 11-15 Performance patterns according to the application. DETAILED DESCRIPTION

[0024] The following will be combined with the examples 1-5 of the application and the drawings Figures 1-15 The technical solutions of the application are described clearly and completely, and obviously the described examples are only some of the examples of the application, rather than all the examples. Based on the examples in the application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0025] The application provides a preparation method of a vanadium redox flow battery hydrochloric acid / mixed acid-based energy storage medium precursor, which comprises the following steps:

[0026] Firstly, the mixture of ammonium metavanadate, chlorinating agent and reducing agent is decomposed at high temperature and in a gas atmosphere to obtain a mixture containing different low-valence vanadium chlorides in different proportions, and the all-vanadium redox flow battery energy storage medium is configured according to the proportion of vanadium chlorides in different valence states, wherein the reducing agent is a carbon material, a sulfide and a carbon-containing organic polymer material; the chlorinating agent is a chlorinated organic polymer material, ammonium chloride and other high-temperature decomposable chlorides. The weight ratio of ammonium metavanadate to reducing agent is between 1:1 and 1:5; the weight ratio of ammonium metavanadate to chlorinating agent is between 1:1 and 1:10. The high-temperature reaction temperature of the mixture is between 800 and 1500 DEG C; the high-temperature reaction time of the mixture is between 1 and 4 hours; the high-temperature reaction atmosphere of the mixture is an inert gas such as argon or nitrogen; and the decomposition product is dissolved in a 3-5M sulfuric acid solution to configure the all-vanadium redox flow battery mixed acid energy storage medium precursor.

[0027] Example 1

[0028] 4g of ammonium metavanadate powder, 20g of sodium sulfite and 20g of chlorinated polyethylene are mixed to obtain a mixture, the mixture is reacted at 800 DEG C under argon gas protection for 1h, and then taken out after being reduced to room temperature, dissolved in a 3M sulfuric acid solution to configure an all-vanadium redox flow battery energy storage medium precursor with a total vanadium ion concentration of 1.6M.

[0029] The solution is used to assemble an all-vanadium redox flow battery for performance test to evaluate the electrolyte performance. The all-vanadium redox flow battery test conditions are as follows: the positive and negative electrodes are 800cm 2 carbon felt electrodes, the positive and negative electrodes both use the prepared solution, and the charging and discharging cycle is carried out at a current density of 80mA / cm 2 , the charging cutoff condition is that the voltage is not higher than 1.5V, and the discharging cutoff condition is that the voltage is not lower than 0.1V.

[0030] Example 2

[0031] 4g of ammonium metavanadate powder, 4g of elemental sulfur and 4g of ammonium chloride are mixed to obtain a mixture, the mixture is reacted at 1000 DEG C under argon gas protection for 2h, and then taken out after being reduced to room temperature, dissolved in a 4M sulfuric acid solution to configure an all-vanadium redox flow battery mixed acid energy storage medium precursor with a total vanadium ion concentration of 1.6M.

[0032] The solution is used to assemble an all-vanadium redox flow battery for performance test to evaluate the electrolyte performance. The all-vanadium redox flow battery test conditions are as follows: the positive and negative electrodes are 800cm 2 carbon felt electrodes, the positive and negative electrodes both use the prepared solution, and the charging and discharging cycle is carried out at a current density of 80mA / cm 2 , the charging cutoff condition is that the voltage is not higher than 1.5V, and the discharging cutoff condition is that the voltage is not lower than 0.1V.

[0033] Example 3

[0034] 2 g of ammonium metavanadate powder, 10 g of activated carbon, and 20 g of chlorinated polypropylene were mixed to obtain a mixture, which was reacted at 1200°C under nitrogen gas protection for 4 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 redox flow batteries with a total vanadium ion concentration of 1.6M.

[0035] 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 were 800 cm 2 Carbon felt electrodes, positive and negative electrodes were made of the prepared solution, using 80mA / cm 2 The charge and discharge cycles are carried out at a current density of 1.5V, 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.

[0036] Example 4

[0037] 5 g of ammonium metavanadate powder, 10 g of graphite, and 25 g of ammonium chloride were mixed to obtain a mixture, which was reacted at 1300° C. under argon gas protection for 4 hours. After cooling to room temperature, the mixture was taken out and dissolved in 5 M sulfuric acid solution to prepare a mixed acid energy storage medium precursor for all-vanadium redox flow batteries with a total vanadium ion concentration of 1.6 M.

[0038] 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 were 800 cm 2 Carbon felt electrodes, positive and negative electrodes were made of the prepared solution, using 80mA / cm 2 The charge and discharge cycles are carried out at a current density of 1.5V, 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.

[0039] Example 5

[0040] 5 g of ammonium metavanadate powder, 25 g of melamine, and 25 g of chlorinated polyethylene were mixed to obtain a mixture, which was reacted at 1500° C. under nitrogen gas protection for 3 hours. After cooling to room temperature, the mixture was taken out and dissolved in 4 M sulfuric acid solution to prepare a mixed acid energy storage medium precursor for all-vanadium redox flow batteries with a total vanadium ion concentration of 1.6 M.

[0041] 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 were 800 cm 2 Carbon felt electrodes, positive and negative electrodes were made of the prepared solution, using 80mA / cm 2 The charge and discharge cycles are carried out at a current density of 1.5V, 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.

[0042] From Figure 1 - Figure 5 It can be seen that although the compositions and proportions of the substances in each embodiment are different, after sintering, the solid powders produced are composed of vanadium tetravalent and trivalent chlorides or sulfates, and according to the different compositions, the sintered product has slightly different XRD peak intensity of tetravalent and trivalent, indicating that the composition of tetravalent and trivalent vanadium is different. Figures 6-10 The morphology of the solid powders after sintering of each embodiment is shown, and the difference is not big, and they are all spherical. According to the vanadium ion concentration and other parameters 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 concentration of sulfate is stable at about 2M, which meets the preparation expectation. According to the battery cycle performance test Figures 11-15 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 mixed acid energy storage medium prepared by adding a chlorinating agent for the synthesis of a full vanadium redox flow battery can be applied to a full vanadium redox flow battery, and a higher coulomb efficiency and energy efficiency can be obtained.

[0043] Table 1 is the data of total vanadium, vanadium ion ratio, chloride ion, and sulfate ion of the solution

[0044]

[0045]

[0046] Table 2 is a performance comparison table

[0047] Serial Number Solution Coulombic Efficiency (%) Voltage Efficiency (%) Energy Efficiency (%) 1 1 95.96 87.07 83.55 2 2 96.51 87.13 84.09 3 3 96.00 87.07 83.58 4 4 97.23 86.84 84.44 5 5 96.98 86.54 84.18

[0048] By the preparation method of the hydrochloric acid / mixed acid-based energy storage medium precursor for a full vanadium redox flow battery provided by the application, low-valence vanadium chloride can be synthesized in one step through a high-temperature solid-phase method, which can effectively reduce the energy consumption and time in the synthesis process and improve the production efficiency. Secondly, adjusting the reaction conditions to realize different proportions of vanadium chloride mixtures provides greater flexibility to meet the needs of full vanadium redox flow batteries in different application scenarios. This preparation route of mixed acid electrolyte not only simplifies the process flow, reduces equipment investment, but also reduces the cost of raw materials, greatly improves the economy and feasibility of the full vanadium redox flow battery. In addition, the prepared energy storage medium has excellent electrochemical performance, which helps to improve the cycle life and energy density of the battery, and promotes the widespread application of this technology in the field of renewable energy storage.

Claims

1. A method for preparing a hydrochloric acid / mixed acid-based energy storage medium precursor for an all-vanadium redox flow battery, characterized in that: The method comprises the following steps: The ammonium metavanadate is mixed with a chlorinating agent and a reducing agent, and is reacted at a high temperature of 800-1500 DEG C under the protection of a gas atmosphere for 1-4 hours to obtain a mixture. After cooling, the mixture is dissolved in a 3-8 M sulfuric acid solution to obtain a vanadium redox flow battery hydrochloric acid / mixed acid-based energy storage medium precursor.

2. A method of preparing a hydrochloric acid / mixed acid based energy storage medium precursor for a vanadium redox flow battery according to claim 1, characterized in that, The reaction atmosphere is any one of argon and nitrogen.

3. A vanadium redox flow battery hydrochloric acid / mixed acid-based energy storage medium precursor prepared by the method according to any one of claims 1-2.

4. Use of a precursor of a hydrochloric acid / mixed acid based energy storage medium for a vanadium redox flow battery according to claim 3, characterized in that, The vanadium redox flow battery hydrochloric acid / mixed acid-based energy storage medium precursor is applied to the preparation of a vanadium redox flow battery.

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