Vanadium battery electrolyte and preparation method and preparation system thereof

Abstract

The invention belongs to the field of vanadium batteries, and discloses a vanadium battery electrolyte as well as a preparation method and a preparation system thereof. The method comprises the following steps: adding ammonium salt into an alkaline vanadium solution, adjusting the pH value to 4-6 by adopting a pH regulator, and carrying out weak acid ammonium salt vanadium precipitation reaction at the temperature of 20-85 DEG C to obtain a sodium ammonium decavanadate solid; the method comprises the following steps: mixing a sodium ammonium decavanadate solid with a crystal modifier solution containing ammonium radicals, and carrying out solid-phase crystal transformation ammonium sodium replacement reaction under the conditions that the pH is 8-10 and the temperature is 90-100 DEG C to obtain a high-purity ammonium metavanadate solid; calcining the high-purity ammonium metavanadate solid to obtain high-purity vanadium pentoxide; and electrolyzing the high-purity vanadium pentoxide to prepare the vanadium battery electrolyte. According to the scheme, the high-purity vanadium pentoxide with the purity larger than 99.9% can be prepared through one-step vanadium precipitation, and the vanadium electrolyte with excellent electrochemical performance is prepared from the high-purity vanadium pentoxide.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of vanadium batteries, and particularly relates to a vanadium battery electrolyte and a preparation method and system thereof. BACKGROUND

[0002] Vanadium battery, also known as vanadium redox flow battery (VRFB), is a kind of liquid flow energy storage battery taking vanadium ions as the only active electrochemical reactant, and has the core advantages of "capacity and power separation, long service life, and high safety", and is particularly suitable for large-scale and long-time energy storage scenes (such as wind power / photovoltaic consumption, power grid peak shaving), and is one of the key energy storage technologies in the current new power system.

[0003] Vanadium pentoxide (V2O5) is the core raw material for preparing vanadium battery electrolyte, and is converted into vanadium ion active components in the electrolyte by chemical or electrochemical methods, thereby constituting the basis for vanadium battery to realize energy storage and conversion. The vanadium electrolyte is not only the core key material of the vanadium battery system, but also an energy carrier, and its performance is directly subject to the purity level of vanadium pentoxide.

[0004] At present, the preparation methods of high-purity vanadium pentoxide mainly include multistage precipitation method, chemical impurity removal method, extraction method, ion exchange method, and chlorination method. The multistage precipitation method separates impurities through multiple precipitation-dissolution-reprecipitation processes. For example, Chinese patent CN119683681A converts ammonium metavanadate crude product into ammonium polyvanadate through acidification, recrystallizes and calcines the ammonium polyvanadate to prepare vanadium pentoxide with a purity of more than 99.9%, thereby realizing resource recycling and zero emission, but the process is long and costly, and long-term recycling of the mother liquor may lead to impurity enrichment. Similar processes such as CN106044853B purify high-purity ammonium metavanadate by acidifying ammonium metavanadate crude product and recrystallizing with ammonia. Chinese patents CN102603000A and CN102730757A use crude sodium metavanadate to prepare high-purity sodium metavanadate by alkali dissolution, magnesium salt impurity removal, and reprecipitation. These methods all have the problems of introducing new impurities (such as magnesium ions), complex process flow, and high cost. The chemical impurity removal method and the extraction method separate impurities by chemical precipitants and organic extractants, respectively. The chemical impurity removal method such as Chinese patents CN114480883B and CN114477283B uses a metal ion synergistic precipitation method, in which Cr 6+ is converted into Cr 3+ in an alkaline environment, and then Ni 2+ / Zn 2+Silicate and hydroxide coprecipitation is formed to achieve deep removal of silicon and chromium, and products with a purity of 99.99% are prepared, but the pH and the amount of reducing agent need to be accurately controlled, otherwise the chromium residue is easy to exceed the standard, and the generated silicon-chromium slag is difficult to handle, causing resource waste. The extraction method, such as Chinese patent CN111057876B, uses a microemulsion system to selectively extract vanadate ions, and high-purity ammonium metavanadate is obtained after stripping; Chinese patent CN201310377023 separates vanadium and impurities by extracting impurity ions to retain vanadium in the raffinate. The extraction method has good selectivity, high product purity and no impurities introduced, but the multi-stage extraction-stripping process is complex, long cycle, and the organic solvent is flammable and toxic, which is not friendly to the environment. The chlorination method uses vanadium slag or intermediate products as raw materials to generate crude vanadyl trichloride through chlorination, which is purified by rectification according to the boiling point difference, and then hydrolyzed or ammonium salt precipitated and calcined to obtain high-purity products. The impurity separation is complete, there is no ammonia-nitrogen wastewater, and the vanadium loss is low, but the safety requirement of the equipment is extremely high, and at present it is mostly in the laboratory stage (related patents CN109835949A, CN106676289A, etc.). In addition, Chinese patent CN117682557A discloses a process for preparing vanadium pentoxide from sodium vanadate liquid containing silicon and chromium. First, the sodium vanadate liquid is treated with aluminum sulfate to remove silicon, and after standing and filtering, ammonium vanadate sodium (SAV) intermediate product is precipitated by two-stage pH adjustment. Subsequently, the process provides two dissolution and recrystallization paths: one is to heat SAV at 80-95°C, add ammonium sulfate after cooling to ≤70°C, and crystallize ammonium metavanadate (AMV) at 20-50°C; the second is to acid-dissolve SAV at pH=1.8-2.5, add ammonium sulfate, and crystallize polyvanadate ammonium (APV) at 80-95°C. Finally, the obtained ammonium salt is calcined to obtain vanadium pentoxide product. It is worth noting that this technical route always relies on the liquid phase transformation process of complete dissolution and recrystallization of SAV, and does not involve any solid phase transformation technology (i.e. the product directly undergoes crystal type and composition transformation without dissolution). Analysis shows that this method has several significant shortcomings: first, the silicon and chromium impurities in the product still remain relatively high (about 0.01%-0.03%), which is difficult to meet the stringent requirements of high-end applications for purity; second, the silicon removal stage needs to stand for ≥48 hours, which is low in process efficiency; finally, the multi-stage filtrate circulation operation is complex, and it is difficult to scale up for industrialization.

[0005] In general, there is still a lack of an industrialized feasible process for directly preparing high-purity vanadium pentoxide (purity ≥99.9%) from alkaline vanadium liquid with one-step precipitation, simple process, efficient impurity removal, and controllable cost. SUMMARY

[0006] The main purpose of the present application is to overcome the shortcomings of the prior art, and to provide a method for preparing high-purity vanadium pentoxide from alkaline vanadium liquid and preparing vanadium battery electrolyte from the same.

[0007] To achieve the above object, the present application adopts the following technical solutions: According to a first aspect of the present application, a preparation method of vanadium battery electrolyte is provided, which comprises the following steps: S1: adding an ammonium salt into an alkaline vanadium solution, adjusting pH to 4-6 by using a pH adjuster, and performing a weak acid ammonium salt vanadium precipitation reaction at a temperature of 20-85℃ to obtain ammonium sodium decavanadate solid; S2: mixing the ammonium sodium decavanadate solid with an ammonium-containing crystal modifier solution, and performing a solid phase replacement crystal ammonium sodium replacement reaction under conditions of pH 8-10 and temperature 90-100℃ to obtain high-purity ammonium metavanadate solid; S3: calcining the high-purity ammonium metavanadate solid to obtain high-purity vanadium pentoxide; S4: electrolyzing the high-purity vanadium pentoxide to obtain the vanadium battery electrolyte.

[0008] As a further implementation, in step S1, the amount of the ammonium salt added is (0.2-0.4) : 1 in terms of the mass ratio of ammonium to V in the alkaline vanadium solution.

[0009] As a further implementation, in step S1, the amount of the ammonium salt added is (0.27-0.33) : 1 in terms of the mass ratio of ammonium to V in the alkaline vanadium solution.

[0010] As a further implementation, in step S1, the ammonium salt is at least one of ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, and ammonium bicarbonate.

[0011] As a further implementation, in step S1, the pH adjuster is at least one of sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, and carbon dioxide.

[0012] As a further implementation, in step S1, the pH is 5-5.5.

[0013] As a further implementation, in step S1, the temperature is 20-40℃.

[0014] As a further implementation, in step S1, the reaction time is 30-90min.

[0015] As a further implementation, in step S1, the reaction time is 60min.

[0016] As a further implementation, in step S2, the ammonium ion concentration in the ammonium-containing crystal modifier solution is 15-55g / L.

[0017] As a further implementation, in step S2, the ammonium ion concentration in the ammonium-containing crystal modifier solution is 35-45g / L.

[0018] As a further implementation, in step S2, the solid-liquid ratio of the sodium ammonium decavanadate solid and the ammonium-containing crystal modifier solution is 1:(4-8) in grams to milliliters.

[0019] As a further implementation, in step S2, the solid-liquid ratio of the sodium ammonium decavanadate solid and the ammonium-containing crystal modifier solution is 1:6 in grams to milliliters.

[0020] As a further implementation, in step S2, the ammonium-containing crystal modifier solution is at least one of an ammonium sulfate solution, an ammonium chloride solution, an ammonium nitrate solution, an ammonium carbonate solution, and an ammonium bicarbonate solution.

[0021] As a further implementation, in step S2, the temperature is 100°C.

[0022] As a further implementation, in step S2, the reaction time is 60-120 min.

[0023] As a further implementation, in step S2, the reaction time is 90 min.

[0024] As a further implementation, in step S3, the calcination temperature is 500-600°C, and the calcination time is 1-3 h.

[0025] As a further implementation, step S4 includes: placing the high-purity vanadium pentoxide and sulfuric acid solution mixture into a negative electrode storage tank of an electrolytic device, adjusting the total vanadium concentration to 1.5-1.7 mol / L, adding a sulfuric acid solution with the same acidity as the negative electrode to a positive electrode storage tank, and performing constant current electrolysis under the condition of a current density of 100-500 mA / cm 2 to obtain a vanadium battery electrolyte with a valence of 3.5.

[0026] According to a second aspect of the present application, a vanadium battery electrolyte is provided, which is prepared by the preparation method of the vanadium battery electrolyte according to any one of the above embodiments.

[0027] According to a third aspect of the present application, a preparation system of a vanadium battery electrolyte is provided, which is used to implement the preparation method of the vanadium battery electrolyte according to any one of the above embodiments, and the preparation system includes: The weak acid ammonium salt vanadium precipitation subsystem comprises: a vanadium precipitation reaction tank for carrying out a weak acid ammonium salt vanadium precipitation reaction, an ammonium salt storage bin for adding an ammonium salt into the vanadium precipitation reaction tank, a pH regulator storage tank for adding a pH regulator into the vanadium precipitation reaction tank, a pH meter for detecting the pH of slurry in the vanadium precipitation reaction tank, a vanadium precipitation temperature control device for controlling the temperature of slurry in the vanadium precipitation reaction tank, and a vanadium precipitation solid-liquid separation device in fluid communication with the vanadium precipitation reaction tank for carrying out solid-liquid separation on the product after the vanadium precipitation reaction. The solid phase metavanadate replacement subsystem comprises: a metacrysis reaction tank for receiving the metavanadate solid obtained after the solid-liquid separation from the vanadium precipitation solid-liquid separation device and carrying out a solid phase metavanadate replacement reaction, a metacrysis agent storage tank for adding a metacrysis agent solution containing an ammonium radical into the metacrysis reaction tank, a pH meter for detecting the pH of slurry in the metacrysis reaction tank, a metacrysis temperature control device for controlling the temperature of slurry in the metacrysis reaction tank, and a metacrysis solid-liquid separation device in fluid communication with the metacrysis reaction tank for carrying out solid-liquid separation on the product after the replacement reaction. The di-vanadium pentoxide preparation subsystem comprises: a drying device for receiving the high-purity ammonium metavanadate obtained after the solid-liquid separation from the metacrysis solid-liquid separation device and drying the high-purity ammonium metavanadate, a calcination device for receiving the dried high-purity ammonium metavanadate from the drying device and calcining the high-purity ammonium metavanadate, and a di-vanadium pentoxide storage bin for receiving the high-purity di-vanadium pentoxide produced after the calcination from the calcination device. The electrolyte preparation subsystem comprises: an electrolysis system for receiving the high-purity di-vanadium pentoxide from the di-vanadium pentoxide storage bin and electrolyzing the high-purity di-vanadium pentoxide, and a vanadium electrolyte storage tank for storing the vanadium battery electrolyte obtained by electrolysis.

[0028] As a further implementation, the preparation system further comprises: a vanadium slag leaching subsystem for leaching the vanadium slag to obtain a crude alkaline vanadium liquid, the metacrysis solid-liquid separation device of the solid phase metavanadate replacement subsystem is connected to the vanadium slag leaching subsystem for supplying the filtrate and washing water produced after the solid-liquid separation thereto for leaching the vanadium slag; a raw material pretreatment subsystem for pretreating the crude alkaline vanadium liquid and supplying the alkaline vanadium liquid obtained after the pretreatment to the weak acid ammonium salt vanadium precipitation subsystem, the raw material pretreatment subsystem comprises: a storage tank for storing the crude alkaline vanadium liquid, a filtering device for filtering the crude alkaline vanadium liquid to remove solid suspensions, and a buffer tank for storing the alkaline vanadium liquid obtained after the filtering, wherein the buffer tank is in fluid communication with the vanadium precipitation reaction tank of the weak acid ammonium salt vanadium precipitation subsystem to supply the alkaline vanadium liquid thereto.

[0029] As a further implementation, the preparation system further comprises: a steam injection subsystem connected with the weak-acid ammonium salt vanadium precipitation subsystem and the solid-phase crystal transformation ammonium sodium replacement subsystem, for injecting steam into the vanadium precipitation reaction tank of the weak-acid ammonium salt vanadium precipitation subsystem and the crystal transformation reaction tank of the solid-phase crystal transformation ammonium sodium replacement subsystem for controlling the reaction temperature.

[0030] As a further implementation, the preparation system further comprises: a pure water supply subsystem connected with the weak-acid ammonium salt vanadium precipitation subsystem, the solid-phase crystal transformation ammonium sodium replacement subsystem, and the vanadium pentoxide preparation subsystem, for supplying pure water to the vanadium precipitation solid-liquid separation device of the weak-acid ammonium salt vanadium precipitation subsystem, the crystal transformation reaction tank of the solid-phase crystal transformation ammonium sodium replacement subsystem, and the crystal transformation solid-liquid separation device.

[0031] As a further implementation, the preparation system further comprises: a wastewater treatment subsystem connected with the vanadium precipitation solid-liquid separation device of the weak-acid ammonium salt vanadium precipitation subsystem, for receiving and treating the filtrate and washing water generated after solid-liquid separation.

[0032] With the above technical solution, the present application has the following beneficial effects compared with the prior art: The scheme of the present application uses alkaline vanadium solution as raw material, realizes comprehensive reduction of main impurity elements such as K, Na, Si, and Cr through weak-acid ammonium salt vanadium precipitation and solid-phase crystal transformation ammonium sodium replacement, achieves the purpose of deep impurity removal, thereby preparing high-purity ammonium metavanadate, and further preparing high-purity vanadium pentoxide. The purity of the high-purity vanadium pentoxide product is greater than 99.9%, and the vanadium battery electrolyte prepared from the high-purity vanadium pentoxide as raw material has excellent electrochemical performance and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed to be used in the description of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and other embodiments can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0034] Figure 1 The flow chart of the preparation method of the vanadium battery electrolyte provided by the present application; Figure 2 The process flow chart of the preparation method of the vanadium battery electrolyte provided by an embodiment of the present application; Figure 3 The block diagram of the preparation system of the vanadium battery electrolyte provided by the present application; Figure 4 The configuration diagram of the preparation system of the vanadium battery electrolyte provided by an embodiment of the present application; Figure 5 XRD patterns of the product of the solid phase transformation of sodium amylate at different reaction times; Figure 6 XRD patterns of the product of step (1), (2), (3) in Example 1; Figure 7 SEM image of the product of step (1) in Example 1; Figure 8 SEM image of the product of step (2) in Example 1; Figure 9 SEM image of the product of step (3) in Example 1. DETAILED DESCRIPTION

[0035] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in details below with specific examples. It should be understood that the specific examples described herein are only used to explain the present application and should not be used to limit the present application.

[0036] According to the need, the specific embodiments of the present application are disclosed in the specification of the present application; however, it should be understood that the embodiments disclosed herein are only examples of the present application which can be implemented in various, alternative forms. In the following description, a plurality of operation parameters and components are described in the conceived embodiments. These specific parameters and components are only used as examples in the present specification and should not be considered as limiting.

[0037] The endpoints of the ranges and any values disclosed in the present application are not limited to the precise values stated. The ranges or values should be construed to be approximations that are understood to include values approximately around those end points. For numeric values, the endpoints of each range, the endpoints of each range and individual point values, and individual point values can be combined with each other to form one or more new numeric ranges, which should be considered as specifically disclosed in the present application.

[0038] Alkaline vanadium solution is a leachate obtained from vanadium slag through a sodium roasting-water leaching process. While rich in vanadium, it also contains impurities such as silicon (Si), chromium (Cr), and phosphorus (P) in anionic form. These impurities significantly increase the difficulty of vanadium product purification, severely restricting product quality and limiting its application in high-end fields. Although approximately 85% of global vanadium consumption is still concentrated in the steel industry, vanadium shows great potential in emerging fields as a high-performance catalyst, a glass-ceramic colorant, and especially as a key raw material for vanadium redox flow battery (VRFB) electrolytes and high-end bismuth vanadate pigments. These high-tech applications place extremely high demands on the purity of vanadium products. For example, the vanadium pentoxide purity for vanadium redox flow battery electrolytes is typically not less than 99.5%; bismuth vanadate pigments have extremely strict limits on chromium content (e.g., chromium content must be less than 5 ppm). Traditional purification processes are costly, complex, and prone to vanadium loss during impurity removal.

[0039] Against this backdrop, abandoning the traditional multi-step purification and conversion process and exploring innovative methods to directly prepare high-purity vanadium pentoxide from primary vanadium solutions has significant strategic value.

[0040] To achieve the aforementioned objectives, the first aspect of this invention provides a method for preparing a vanadium battery electrolyte, such as... Figure 1 As shown, the method includes the following steps: S1: Adding ammonium salt to alkaline vanadium solution, adjusting the pH to 4-6 using a pH adjuster, and carrying out a weakly acidic ammonium salt precipitation reaction at a temperature of 20-85℃ to obtain solid sodium decavanadate; S2: Mixing the solid sodium decavanadate with a crystallization agent solution containing ammonium ions, and carrying out a solid-phase crystallization sodium ammonium sodium displacement reaction at a pH of 8-10 and a temperature of 90-100℃ to obtain high-purity solid ammonium metavanadate; S3: Calcining the high-purity solid ammonium metavanadate to obtain high-purity vanadium pentoxide; S4: Electrolyzing the high-purity vanadium pentoxide to obtain a vanadium battery electrolyte.

[0041] The preparation method of this invention uses alkaline vanadium solution as raw material. By precipitation of vanadium with weakly acidic ammonium salt and replacement with sodium ammonium in solid-phase crystallization, the main impurity elements such as K, Na, Si, and Cr are comprehensively reduced, achieving the purpose of deep impurity removal. This process yields high-purity ammonium metavanadate, which in turn yields high-purity vanadium pentoxide. The purity of the high-purity vanadium pentoxide product is greater than 99.9%. The vanadium battery electrolyte prepared using this high-purity vanadium pentoxide as raw material exhibits excellent electrochemical performance and low cost.

[0042] The preparation method of the present application highly integrates impurity removal and product preparation core steps, greatly reduces intermediate links and operation units, and significantly shortens the process flow. This not only means faster production cycle and response speed, but also reduces the complexity of process control and equipment investment. The preparation method of the present application discards the steps of chlorination, ion exchange, extraction and chemical impurity removal in the conventional high-purity vanadium pentoxide preparation process, the process does not introduce impurity ions and does not produce new solid waste, and completely avoids chlorine and organic pollution. The whole process is simple, the equipment demand is low, the environment is friendly, and it is highly consistent with the requirements of industrial production.

[0043] The basic vanadium solution is a core intermediate product connecting "vanadium-containing raw materials" and "vanadium products (such as vanadium pentoxide, vanadium iron, vanadium electrolyte)" in the vanadium smelting industry chain. The preparation method of the present application uses basic vanadium solution as raw material, which is more basic than using other vanadium intermediates or crude products to prepare high-purity vanadium pentoxide. The use of the most basic primary raw material in the vanadium smelting industry chain not only greatly reduces production cost, but also has wide adaptability to raw materials, which is helpful to the rapid development of vanadium industry. The present application does not have specific requirements for the composition of the basic vanadium solution.

[0044] In some embodiments, the basic vanadium solution is specifically a sodiumized vanadium solution, i.e. the leaching solution obtained by sodiumizing roasting-water leaching process of vanadium slag. The solution is alkaline and rich in anion impurities such as silicon Si, Cr and P.

[0045] The preparation method of the present application is further described below for each step.

[0046] In step S1, the pH range is 4-6, and a lower or higher pH will affect the vanadium precipitation yield. The pH can be typically but not limitedly set to 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0. Preferably, the pH is 5-5.5.

[0047] In step S1, the reaction temperature is 20-85℃, and a higher temperature not only cannot produce the target product, but also has a low product yield. The reaction temperature can be typically but not limitedly set to 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃. Preferably, the temperature is 20-40℃.

[0048] In step S1, the reaction time is 30-90 min. When the reaction time is shorter, the reaction does not proceed completely, and the yield of sodium ammonium decavanadate is low. When the reaction time is too long, the yield does not change, and the production efficiency is reduced. The reaction time can be typically but not limitedly set to 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, or 90 min. Preferably, the reaction time is 60 min.

[0049] In step S1, the ammonium salt is at least one of ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, and ammonium bicarbonate.

[0050] In step S1, the amount of ammonium salt added (also referred to as the ammonium addition coefficient) is (0.2-0.4) : 1 in terms of the mass ratio of ammonium to V in the basic vanadium solution. When the ammonium addition coefficient is in the range of (0.2-0.4) : 1, too high an ammonium addition coefficient leads to waste of ammonium salt and increased production cost, and too low an ammonium addition coefficient affects the yield of vanadium precipitation. The ammonium addition coefficient can be typically but not limitedly set to 0.2:1, 0.22:1, 0.25:1, 0.27:1, 0.30:1, 0.33:1, 0.35:1, 0.38:1, or 0.4:1. Preferably, the ammonium addition coefficient is (0.27-0.33) : 1.

[0051] In step S1, the pH adjuster is at least one of sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, and carbon dioxide.

[0052] In one specific example, step S1 is implemented by the following method: a certain volume of the basic vanadium solution is measured, ammonium salt is added in a mass ratio of m(NH4 + ) : m(V) = (0.2-0.4) : 1, the solution is stirred until the ammonium salt is completely dissolved, a pH adjuster is used to adjust the pH of the solution to 4-6, the solution is continuously stirred at a temperature of 20-85°C for 30-90 min, after the reaction is completed, the vanadium precipitation product and the filtrate are obtained by filtration, the vanadium precipitation product is washed with deionized water, filtered, and dried to obtain sodium ammonium decavanadate ((NH4)4Na2V 10 O 28 ).

[0053] In step S2, the pH range is 8-10. When the pH is lower or higher, a single pure phase of the target ammonium metavanadate product cannot be obtained. The pH can be typically but not limitedly set to 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, or 10.0.

[0054] In step S2, the reaction temperature is 90-100°C, and the reaction temperature can be typically but not limited to 90°C, 92°C, 94°C, 96°C, 98°C, or 100°C. Preferably, the reaction temperature is 100°C, at which the rate of the vanadium crystallization reaction is fast and the vanadium yield is the highest.

[0055] In step S2, the reaction time is 60-120 min. If the reaction time is short, the vanadium precipitation reaction is not completely performed, and the vanadium yield is low. If the reaction time is too long, the yield does not change, and the process energy consumption increases. The reaction time can be typically but not limited to 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min. Preferably, the reaction time is 90 min.

[0056] In step S2, the concentration of ammonium ions in the ammonium-containing crystallization agent solution is 15-55 g / L. If the concentration is too low, the vanadium yield is affected. If the concentration is too high, the ammonium salt is wasted, and the preparation cost increases. The concentration of ammonium ions can be typically but not limited to 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, or 50 g / L. Preferably, the concentration of ammonium ions in the ammonium-containing crystallization agent solution is 35-45 g / L.

[0057] In step S2, the solid-liquid ratio of the ammonium sodium decavanadate solid and the ammonium-containing crystallization agent solution is 1:(4-8) in grams to milliliters. If the volume of deionized water is too high, the volume of the filtrate to be treated is large, the cost is high, and the vanadium loss rate is high. If the volume of deionized water is too low, the conversion of the crystal form of the product and the removal of impurities are affected. The solid-liquid ratio can be typically but not limited to 1:4, 1:5, 1:6, 1:7, or 1:8. Preferably, the solid-liquid ratio is 1:6.

[0058] In step S2, the ammonium-containing crystallization agent solution is at least one of an ammonium sulfate solution, an ammonium chloride solution, an ammonium nitrate solution, an ammonium carbonate solution, and an ammonium bicarbonate solution. Preferably, the ammonium-containing crystallization agent solution is at least one of an ammonium carbonate solution and an ammonium bicarbonate solution. It should be noted that when an alkaline ammonium salt solution such as an ammonium carbonate solution or an ammonium bicarbonate solution is used as the ammonium-containing crystallization agent solution, after mixing with the ammonium sodium decavanadate solid, the solution pH is in the range of 8-10 without additional pH adjustment, and the solid-phase crystalline ammonium replacement reaction can be directly performed to obtain a single pure-phase ammonium metavanadate solid product, further simplifying the process. When other acidic ammonium salt solutions are used as the ammonium-containing crystallization agent solution, after mixing with the ammonium sodium decavanadate solid, an alkali solution needs to be additionally used to adjust the solution pH to 8-10, and then the solid-phase crystalline ammonium replacement reaction can be performed to obtain a single pure-phase ammonium metavanadate solid product.

[0059] In one specific example, step S2 is implemented by first adding a specified amount of ammonium-containing crystal modifier into deionized water to configure a crystal modifier solution, with the ammonium ion concentration being 15-55 g / L, and then adding a certain amount of sodium ammonium decavanadate into the crystal modifier solution. The amount of sodium ammonium decavanadate is added according to a solid-liquid ratio S (g) : L (ml) = 1 : (4-8), and after being stirred and mixed uniformly, heating is performed at a temperature of 90-100°C for 60-120 min under continuous stirring. After the reaction is completed, the vanadium precipitation product and the filtrate are obtained by filtration, the vanadium precipitation product is washed, filtered and dried with deionized water to obtain high-purity ammonium metavanadate solid, and the filtrate enters the leaching system of the production link.

[0060] In step S3, the calcination temperature is 500-600°C, and the calcination time is 1-3 h. If the calcination temperature is too low, the calcination is insufficient, and low-valence vanadium oxide by-products are formed. If the calcination temperature is too high, the energy consumption is significantly increased. The calcination temperature can be typically but non-limitingly set to 500°C, 520°C, 540°C, 560°C, 580°C, 600°C. If the calcination time is too short, the reduction is incomplete. If the calcination time is too long, the energy consumption is increased. The calcination time can be typically but non-limitingly set to 1 h, 1.5 h, 2 h, 2.5 h, 3 h. Preferably, the calcination temperature is 550°C, and the calcination time is 2 h.

[0061] Step S4 includes: placing the mixed solution of high-purity vanadium pentoxide and sulfuric acid solution in the negative electrode storage tank of the electrolytic device, adjusting the total vanadium concentration to 1.5-1.7 mol / L, adding a sulfuric acid solution with the same acidity as the negative electrode to the positive electrode storage tank, and performing constant-current electrolysis under the condition of a current density of 100-500 mA / cm 2 to a valence of 3.5 valence to obtain a vanadium battery electrolyte. The total vanadium concentration can be typically but non-limitingly set to 1.5 mol / L, 1.6 mol / L, 1.7 mol / L. Preferably, the total vanadium concentration is adjusted to 1.6 mol / L. The current density can be typically but non-limitingly set to 100 mA / cm 2 , 200 mA / cm 2 , 300 mA / cm 2 , 400 mA / cm 2 , 500 mA / cm 2 . Preferably, the current density is set to 200 mA / cm 2 .

[0062] In some embodiments, the preparation method further includes: returning the filtrate and washing water generated during the solid-liquid separation process after the solid-phase crystallization sodium ammonium displacement reaction to the vanadium slag leaching process for leaching the vanadium slag to obtain a crude alkaline vanadium solution. The filtrate and washing water generated during the solid-liquid separation process after the solid-phase crystallization sodium ammonium displacement reaction have low impurity content and can be directly reused in the vanadium slag leaching process of large-scale production. This not only recovers residual V and ammonium ions but also reduces the wastewater treatment volume of the entire large-scale production system, resulting in significant economic and social benefits.

[0063] The following combination Figure 2 The preparation method of the vanadium battery electrolyte provided in one embodiment of the present invention is further explained. For example... Figure 2 As shown, this method uses alkaline vanadium solution as raw material. Vanadium is precipitated by weakly acidic ammonium salt, and after solid-liquid separation, sodium decavanadate and filtrate are obtained. The filtrate can be treated in the wastewater treatment process. The sodium decavanadate is replaced by solid-phase crystallization with sodium ammonium, and after solid-liquid separation, high-purity ammonium metavanadate and filtrate are obtained. The filtrate can be reused in the vanadium slag leaching process. The high-purity ammonium metavanadate is dried and calcined to obtain 99.95% grade vanadium pentoxide. The 99.95% grade vanadium pentoxide can be electrolyzed to produce vanadium battery electrolyte.

[0064] The specific steps of this method and the main chemical reactions involved are described below: (1) Vanadium precipitation with weakly acidic ammonium salts Using alkaline vanadium solution as raw material, ammonium salt is first added at a temperature below 85°C to generate the precipitate sodium decavanadate (NH4)4Na2V. 10 O 28 The reaction formula is as follows: NH 4+ +Na + +V 10 O 28 6- →3(NH4)4Na2V 10 O 28 ↓ (20~85℃) Formula (1) (2) Solid-phase conversion to sodium ammonium peroxide displacement Then, ammonium salt is added to the deionized water to prepare a solution containing ammonium ions (NH4+). + The solution of sodium decavanadate (1) was prepared, and the pH was adjusted to be in the range of 8-10. The sodium decavanadate was then added, and the mixture was stirred and heated for a set time. After filtration, washing, and drying, high-purity ammonium metavanadate (pure phase NH4VO3) was obtained. The reaction formula is as follows: 3(NH4)4Na2V 10 O 28 +12OH - +18NH4 +→ 30NH4VO3↓ + 6H2O + 6Na + Formula (2) (3) Preparation of high-purity vanadium pentoxide Finally, the high-purity ammonium metavanadate is calcined to obtain high-purity vanadium pentoxide. The reaction formula is as follows: 2NH4VO3→ V2O5+ 2NH3+ H2O↑ Formula (3) The core principles of this method include the following aspects: (1) Weak acid ammonium salt vanadium precipitation, also known as ammonium sodium decavanadate precipitation reaction, has excellent effect on removing impurities such as silicon (Si) and chromium (Cr), and the content of Si and Cr in the product can be reduced to below 0.005% in one precipitation. The key of this process is to add ammonium sodium decavanadate to the solution containing ammonium ions (NH4 + ), and to inhibit the dissolution of ammonium sodium decavanadate by means of the same ion effect (because its solubility in pure water is very high), that is, the reverse dissolution process of formula (1). This inhibition effect ensures the efficient removal of impurities such as silicon and chromium. The main reason is that once ammonium sodium decavanadate dissolves, it will release Si and Cr ions into the solution again. This process is equivalent to changing the crystallization reaction into a recrystallization reaction, which has poor effect on removing impurities, and finally affects the removal effect and yield of the subsequent precipitation step.

[0065] (2) After ammonium sodium decavanadate is added to the solution containing ammonium ions, the pH of the solution is in the range of 8-10, and when heated, the ammonium ions will be reorganized and release potassium and sodium ions. This process causes the depolymerization of the macromolecular structure of the decavanadate (V 10 O 28 6- ) group, forming a metavanadate (VO 3- ) with lower polymerization degree. It is worth noting that ammonium sodium decavanadate does not dissolve significantly at this stage, but its internal crystal structure has undergone significant changes, so this step is called solid phase crystallization, that is, the chemical process represented by formula (2).

[0066] (3) The high-polymerization-state decavanadate is more likely to adsorb a large number of impurity ions through strong electrostatic interaction and coordination exchange due to its large molecular size and many unsaturated coordination sites (such as exposed V-O bonds). The low-polymerization-state ammonium metavanadate has a simple structure and limited adsorption capacity for impurities. This phase change crystallization process not only excludes the pollution of sodium ions to the final product, but also simplifies the structure itself, which is beneficial to improving the purity of the precipitate, thereby obtaining high-purity ammonium metavanadate.

[0067] The second aspect of the present application provides a vanadium battery electrolyte prepared by the above preparation method.

[0068] Based on the same concept, the third aspect of the present application provides a preparation system for vanadium battery electrolyte for implementing the above preparation method, such asFigure 3 and Figure 4 As shown in FIG. 1, the preparation system comprises a raw material pretreatment subsystem 1, a weak-acid ammonium salt vanadium precipitation subsystem 2, a solid-phase replacement subsystem 3, a vanadium pentoxide preparation subsystem 4, and a vanadium battery electrolyte preparation subsystem 5.

[0069] The raw material pretreatment subsystem 1 is used for pretreating the crude alkaline vanadium solution and supplying the pretreated alkaline vanadium solution to the weak-acid ammonium salt vanadium precipitation subsystem 2. The raw material pretreatment subsystem 1 comprises a liquid storage tank 1-1 for storing the crude alkaline vanadium solution, a filtering device 1-3 for filtering the crude alkaline vanadium solution to remove solid suspensions, and a buffer tank 1-4 for storing the filtered alkaline vanadium solution, wherein the buffer tank 1-4 is in fluid communication with the weak-acid ammonium salt vanadium precipitation subsystem 2 to supply the alkaline vanadium solution thereto.

[0070] Specifically, the outlet pipeline of the liquid storage tank 1-1 is connected to the inlet pipeline of the filtering device 1-3 via a centrifugal pump 1-2; the outlet pipeline of the filtering device 1-3 is connected to the inlet pipeline of the buffer tank 1-4; and the outlet pipeline of the buffer tank 1-4 is connected to the inlet pipeline of the weak-acid ammonium salt vanadium precipitation subsystem 2 via a centrifugal pump 2-1. The filtering device 1-3 can be a precision filter.

[0071] The weak-acid ammonium salt vanadium precipitation subsystem 2 is used for preparing ammonium sodium decavanadate through a weak-acid ammonium salt vanadium precipitation reaction. The weak-acid ammonium salt vanadium precipitation subsystem 2 comprises a vanadium precipitation reaction tank 2-6 for performing the weak-acid ammonium salt vanadium precipitation reaction, an ammonium salt storage bin 2-4 for adding ammonium salt into the vanadium precipitation reaction tank 2-6, a pH adjuster storage tank 2-5 for adding a pH adjuster into the vanadium precipitation reaction tank 2-6, a pH meter 2-2 for detecting the pH of the slurry in the vanadium precipitation reaction tank 2-6, a vanadium precipitation temperature control device for controlling the temperature of the slurry in the vanadium precipitation reaction tank 2-6, and a vanadium precipitation solid-liquid separation device 2-8 in fluid communication with the vanadium precipitation reaction tank 2-6 for performing solid-liquid separation on the product after the vanadium precipitation reaction.

[0072] Specifically, the inlet pipeline of the vanadium precipitation reaction tank 2-6 is connected to the outlet pipeline of the buffer tank 1-4 via a centrifugal pump 2-1; the electrode of the pH meter 2-2 is in contact with the slurry in the vanadium precipitation reaction tank 2-6; the vanadium precipitation temperature control device comprises a thermometer 2-3 for detecting the temperature of the slurry, the thermometer 2-3 being in contact with the slurry in the vanadium precipitation reaction tank 2-6; the outlet of the ammonium salt storage bin 2-4 is connected to the inlet of the vanadium precipitation reaction tank 2-6; the outlet pipeline of the pH adjuster storage tank 2-5 is connected to the inlet pipeline of the vanadium precipitation reaction tank 2-6; and the outlet pipeline of the vanadium precipitation reaction tank 2-6 is connected to the inlet pipeline of the vanadium precipitation solid-liquid separation device 2-8 via a slurry pump 2-7. The vanadium precipitation solid-liquid separation device 2-8 can be a filtering centrifuge.

[0073] The solid phase transformation ammonium sodium replacement subsystem 3 is used for preparing high-purity ammonium metavanadate by solid phase transformation ammonium sodium replacement reaction. The solid phase transformation ammonium sodium replacement subsystem 3 comprises: a transformation reaction tank 3-6 for receiving ammonium sodium decavanadate solid obtained after solid-liquid separation and carrying out solid phase transformation ammonium sodium replacement reaction on the ammonium sodium decavanadate solid, a transformation agent storage tank 3-7 for preparing a transformation agent solution containing ammonium and adding the transformation agent solution containing ammonium into the transformation reaction tank 3-6, a pH meter 3-4 for detecting the pH of slurry in the transformation reaction tank 3-6, a transformation temperature control device for controlling the temperature of slurry in the transformation reaction tank 3-6, and a transformation solid-liquid separation device 3-9 in fluid communication with the transformation reaction tank 3-6 for carrying out solid-liquid separation on the product after the replacement reaction.

[0074] Specifically, the discharge port of the vanadium precipitation solid-liquid separation device 2-8 is connected to the feed inlet of the transformation reaction tank 3-6 through the feeding belt 3-1; the electrode of the pH meter 3-4 is in contact with the slurry in the transformation reaction tank 3-6; the transformation temperature control device comprises a thermometer 3-5 for detecting the temperature of the slurry, and the thermometer 3-5 is in contact with the slurry in the transformation reaction tank 3-6; the liquid outlet pipeline of the transformation agent storage tank 3-7 is connected to the liquid inlet pipeline of the transformation reaction tank 3-6; the liquid outlet pipeline of the transformation reaction tank 3-6 is connected to the liquid inlet pipeline of the transformation solid-liquid separation device 3-9 through the slurry pump 3-8. The transformation solid-liquid separation device 3-9 can be a filtering centrifuge.

[0075] The vanadium pentoxide preparation subsystem 4 is used for preparing vanadium pentoxide by calcining high-purity ammonium metavanadate. The vanadium pentoxide preparation subsystem 4 comprises: a drying device 4-1 for receiving high-purity ammonium metavanadate solid obtained after solid-liquid separation from the transformation solid-liquid separation device 3-9 of the solid phase transformation ammonium sodium replacement subsystem 3 and drying the high-purity ammonium metavanadate solid, a calcining device 4-4 for receiving the dried high-purity ammonium metavanadate solid from the drying device 4-1 and calcining the high-purity ammonium metavanadate solid, and a vanadium pentoxide storage bin 4-5 for receiving high-purity vanadium pentoxide produced after calcination from the calcining device 4-4.

[0076] Specifically, the discharge port of the transformation solid-liquid separation device 3-9 is connected to the feed inlet of the drying device 4-1 through the feeding belt 3-11; the discharge port of the drying device 4-1 is connected to the feed inlet of the ammonium metavanadate storage bin 4-3 through the feeding belt 4-2; the discharge port of the ammonium metavanadate storage bin 4-3 is connected to the feed inlet of the calcining device 4-4; the discharge port of the calcining device 4-4 is connected to the feed inlet of the vanadium pentoxide storage bin 4-5; and the discharge port of the vanadium pentoxide storage bin 4-5 is connected to the feed inlet of the high-purity vanadium pentoxide packaging barrel 4-6. The drying device 4-1 can be a microwave dryer, and the calcining device 4-4 can be a rotary kiln.

[0077] The vanadium battery electrolyte preparation subsystem 5 is used to prepare vanadium battery electrolyte by electrolyzing high-purity vanadium pentoxide. The vanadium battery electrolyte preparation subsystem 5 comprises an electrolysis system 5-1 receiving high-purity vanadium pentoxide from the vanadium pentoxide storage bin 4-5 and electrolyzing the high-purity vanadium pentoxide, and a vanadium electrolyte storage tank 5-2 storing the electrolyzed vanadium battery electrolyte.

[0078] Specifically, the electrolysis system 5-1 comprises a positive electrode storage tank and a negative electrode storage tank, and the negative electrode storage tank feed inlet is connected to the high-purity vanadium pentoxide packaging barrel 4-6 discharge outlet; the electrolysis system 5-1 discharge outlet is connected to the vanadium electrolyte storage tank 5-2 feed inlet.

[0079] In some embodiments, the preparation system further comprises a pure water supply subsystem connected to the weak acid ammonium salt vanadium precipitation subsystem 2 and the solid phase crystal transformation ammonium sodium replacement subsystem 3, and used to supply pure water to the vanadium precipitation solid-liquid separation device 2-8 of the weak acid ammonium salt vanadium precipitation subsystem 2 and the crystal transformation reaction tank 3-6 and the crystal transformation solid-liquid separation device 3-9 of the solid phase crystal transformation ammonium sodium replacement subsystem 3.

[0080] Specifically, the pure water supply subsystem comprises a pure water pipeline, the pure water pipeline is connected to the vanadium precipitation solid-liquid separation device 2-8 water inlet pipeline through the pure water valve 2-9; the pure water pipeline is connected to the crystal transformation reaction tank 3-6 water inlet pipeline through the pure water valve 3-2; the pure water pipeline is connected to the crystal transformation solid-liquid separation device 3-9 water inlet pipeline through the pure water valve 3-3.

[0081] In some embodiments, the preparation system further comprises a vanadium residue leaching subsystem, which is used to leach the vanadium residue to obtain a crude alkaline vanadium solution. The vanadium residue leaching subsystem is connected to the raw material pretreatment subsystem 1 to supply the crude alkaline vanadium solution thereto. Preferably, the crystal transformation solid-liquid separation device 3-9 of the solid phase crystal transformation ammonium sodium replacement subsystem 3 is connected to the vanadium residue leaching subsystem to supply the filtrate and washing water generated after solid-liquid separation to the vanadium residue leaching subsystem for leaching the vanadium residue. Specifically, the crystal transformation solid-liquid separation device 3-9 outlet pipeline is connected to the vanadium residue leaching subsystem through the centrifugal pump 3-10.

[0082] In some embodiments, the preparation system further comprises a steam injection subsystem connected to the weak acid ammonium salt vanadium precipitation subsystem 2 and the solid phase crystal transformation ammonium sodium replacement subsystem 3, and used to inject steam into the vanadium precipitation reaction tank 2-6 of the weak acid ammonium salt vanadium precipitation subsystem 2 and the crystal transformation reaction tank 3-6 of the solid phase crystal transformation ammonium sodium replacement subsystem 3 to control the reaction temperature. Specifically, the steam injection subsystem comprises a medium-pressure steam pipeline, the medium-pressure steam pipeline is connected to the vanadium precipitation reaction tank 2-6 gas inlet pipeline through the steam valve 2-11, and the medium-pressure steam pipeline is connected to the crystal transformation reaction tank 3-6 gas inlet pipeline through the steam valve 3-12.

[0083] In some embodiments, the preparation system further comprises a wastewater treatment subsystem connected to the vanadium precipitation solid-liquid separation device 2-8 of the weak-acid ammonium salt vanadium precipitation subsystem 2 for receiving the filtrate and washing water generated after the solid-liquid separation therefrom and treating them to recover residual V and Cr. Specifically, the outlet pipeline of the vanadium precipitation solid-liquid separation device 2-8 is connected to the wastewater treatment subsystem via a centrifugal pump 2-10.

[0084] The following description will be made in conjunction with the accompanying drawings. Figure 4 Further description will be made to the specific operation steps of the preparation system of the vanadium battery electrolyte provided in an embodiment of the present application.

[0085] (1) Raw material preparation process: the centrifugal pump 1-2 is used to pump the crude alkaline vanadium solution in the storage tank 1-1 into the filtering device 1-3 to remove the solid suspensions in the solution by filtering, and the filtered alkaline vanadium solution is pumped into the buffer tank 1-4 for standby.

[0086] (2) Weak-acid ammonium salt vanadium precipitation process: a certain volume of alkaline vanadium solution is pumped from the buffer tank 1-4 into the vanadium precipitation reaction tank 2-6, and ammonium salt (for example, ammonium sulfate) and pH adjuster (for example, sulfuric acid) are added into the vanadium precipitation reaction tank 2-6 from the ammonium salt storage bin 2-4 and the pH adjuster storage tank 2-5 respectively, the amount of ammonium salt is controlled to be m(NH4 + ): m(V)=(0.2~0.4)∶1, the pH of the solution is controlled to be 4~6 by the pH meter 2-2, the temperature of the solution is controlled to be 20~85℃ by the thermometer 2-3 and the steam valve 2-11, and the stirring is continued for 30~90 min. After the stirring is completed, the slurry in the vanadium precipitation reaction tank 2-6 is pumped into the solid-liquid separation device 2-8 by the slurry pump 2-7 for solid-liquid separation, the filtrate generated in the solid-liquid separation device 2-8 is pumped into the wastewater treatment process by the centrifugal pump 2-10 to recover residual V and Cr. After the filtration is completed, the pure water valve 2-9 is opened, the solid product in the solid-liquid separation device 2-8 is washed using pure water, the washing water generated in the solid-liquid separation device 2-8 is also pumped into the wastewater treatment process by the centrifugal pump 2-10 to recover residual V and Cr, and after the washing is completed, ammonium sodium decavanadate (NH4)4Na2V 10 O 28 .

[0087] (3) Solid phase crystal transformation ammonium sodium replacement process: the ammonium sodium decavanadate reaction product in the solid-liquid separation device 2-8 is added into the crystal transformation reaction tank 3-6 through the feeding belt 3-1, the crystal transformation agent solution with the ammonium ion concentration of 15-55 g / L is configured in the crystal transformation agent storage tank 3-7, the configured crystal transformation agent solution is added into the crystal transformation reaction tank 3-6, wherein the ammonium sodium decavanadate is added in the solid-liquid ratio S (g) : L (ml) = 1 : (4-8), and the weight of the ammonium sodium decavanadate needs to deduct the water content. After uniform stirring, the solution temperature is controlled to be 90-100 DEG C through the thermometer 3-5 and the steam valve 3-12, and the stirring is continuously conducted for 60-120 min. After the stirring is completed, the slurry in the crystal transformation reaction tank 3-6 is punched into the solid-liquid separation device 3-9 through the slurry pump 3-8 to conduct solid-liquid separation, the filtrate generated in the solid-liquid separation device 3-9 is punched into the vanadium slag leaching process through the centrifugal pump 3-10 to recover the residual V and ammonium ions therein. After the filtration is completed, the pure water valve 3-3 is opened, and the solid product in the solid-liquid separation device 3-9 is washed using pure water. The washing water generated in the solid-liquid separation device 3-9 is also punched into the vanadium slag leaching process through the centrifugal pump 3-3 to recover the residual V and ammonium ions therein. After the washing is completed, the high-purity ammonium metavanadate product is obtained.

[0088] (4) Vanadium pentoxide preparation process: the high-purity ammonium metavanadate product in the filter centrifuge 3-9 is added into the drying device 4-1 through the feeding belt 3-11 to conduct drying. The dried high-purity ammonium metavanadate is discharged from the drying device 4-1 through the feeding belt 4-2, enters the ammonium metavanadate storage bin 4-3, and then is sent into the calcining device 4-4 from the ammonium metavanadate storage bin 4-3 to conduct calcining. The calcining temperature is 500-600 DEG C, and the calcining time is 1-3 h. After the calcining is completed, the vanadium pentoxide is discharged from the calcining device 4-4 into the vanadium pentoxide storage bin 4-5, and then is loaded into the vanadium pentoxide packaging barrel 4-6 from the vanadium pentoxide storage bin 4-5 to complete the packaging work. Finally, the vanadium pentoxide with the purity greater than 99.9% is obtained.

[0089] (5) Vanadium electrolyte preparation process: the high-purity vanadium pentoxide in the vanadium pentoxide packaging barrel 4-6 is added into the electrolysis system 5-1 to conduct electrolysis, and the vanadium battery electrolyte obtained by electrolysis is stored in the vanadium electrolyte storage tank 5-2.

[0090] The following is an embodiment for explaining the process method mentioned in the application, but the application is not limited to the following embodiment.

[0091] The basic vanadium solution used in the following examples is from the Panzhihua Vanadium Products Branch of the Panzhihua Iron and Steel Group, which is a vanadium leaching solution obtained by sodium roasting and water leaching of vanadium slag. First, the initial vanadium solution in the storage tank 1-1 is pumped into the filtering device 1-3 using a centrifugal pump 1-2, and the solid suspended matter in the solution is removed by filtering through the filtering device 1-3. The filtered vanadium solution is pumped into the buffer tank 1-4 for standby use. The specific components of the solution are detected as follows: K-0.674 g / L, Na-41.92 g / L, Si-1.28 g / L, Ca-0.11 g / L, Cr-3.91 g / L, P-0.039 g / L, and TV-47.33 g / L.

[0092] Example 1: (1) 10 m 3 of the basic vanadium solution is pumped from the buffer tank 1-4 into the vanadium precipitation reaction tank 2-6, stirring is started, and 573 kg of ammonium sulfate (the mass ratio of ammonium to V in the basic vanadium solution is 0.33) is added from the ammonium salt storage bin 2-4 into the vanadium precipitation reaction tank 2-6. After the ammonium sulfate is completely dissolved, sulfuric acid is added from the pH regulator storage tank 2-5 into the vanadium precipitation reaction tank 2-6, the pH of the solution is controlled to 5.5 by the pH meter 2-2, and the temperature of the solution is controlled to 20°C by the thermometer 2-3. The stirring is continued for 60 min. After the stirring is completed, the slurry in the vanadium precipitation reaction tank 2-6 is pumped into the solid-liquid separation device 2-8 by the slurry pump 2-7 for solid-liquid separation, and ammonium sodium decavanadate (NH4)4Na2V 10 O 28 is obtained. The filtrate and washing liquid generated in the process are pumped into the wastewater treatment process. The ammonium sodium decavanadate solid contains 10.12% water and 40.21% vanadium.

[0093] (2) 567 kg of ammonium carbonate (containing about 30 wt% NH3) and 4 m 3 of pure water are added into the crystal modifier storage tank 3-7 to configure an ammonium carbonate solution with a concentration of 45 g / L and are added into the crystal modification reaction tank 3-6. Then, 742 kg of ammonium sodium decavanadate solid is added into the crystal modification reaction tank 3-6 by the feeding belt 3-1 (the solid-liquid ratio is 1:6), the material is stirred and mixed uniformly, the steam valve 3-12 is opened to heat the material, the temperature of the solution is controlled to 100°C by the thermometer 3-5, and the stirring is continued for 90 min. After the stirring is completed, the slurry in the crystal modification reaction tank 3-6 is pumped into the solid-liquid separation device 3-9 by the slurry pump 3-8 for solid-liquid separation, and high-purity ammonium metavanadate solid is obtained. The filtrate and washing liquid generated in the process are pumped into the vanadium slag leaching process.

[0094] (3) The high-purity ammonium metavanadate product in the solid-liquid separation device 3-9 is sent into the drying device 4-1 through the feeding belt 3-11 for drying, and the dried product is sent into the calcining device 4-4 from the storage bin 4-3 for calcining, the calcining temperature is 550 DEG C, and the calcining time is 2 h. After the calcining is completed, the calcined product is subjected to chemical detection analysis.

[0095]

[0096] (Unit: %) (4) The calcined product obtained in step (3) is electrolyzed in the electrolysis system 5-1 to obtain vanadium electrolyte, and the quality of the obtained electrolyte meets the requirements of the national standard GB / T 37204-2018 "Electrolyte for all-vanadium redox flow battery" first-class product.

[0097] Comparative Example One: (1) 10 m 3 of alkaline vanadium solution is pumped into the vanadium precipitation reaction tank 2-6, 573 kg of ammonium sulfate is added into the vanadium precipitation reaction tank 2-6, and stirring is started. After the ammonium sulfate is completely dissolved, sulfuric acid is added into the vanadium precipitation reaction tank 2-6 from the pH regulator storage tank 2-5, the pH of the solution is controlled to be 5.5 by the pH meter 2-2, and the temperature of the solution is controlled to be 20 DEG C by the thermometer 2-3. The stirring is continued for 60 min. After the stirring is completed, the slurry in the vanadium precipitation reaction tank 2-6 is subjected to solid-liquid separation in the solid-liquid separation device 2-8 to obtain ammonium sodium decavanadate (NH4)4Na2V 10 O 28 solid. The detection shows that the ammonium sodium decavanadate solid contains 10.12% of water and 40.21% of vanadium.

[0098] (2) The pure water valve 3-2 is opened, 4 m 3 of pure water is added into the crystal transformation reaction tank 3-6, 742 kg of ammonium sodium decavanadate solid is added into the crystal transformation reaction tank 3-6 through the feeding belt 3-1, and sodium hydroxide is added to adjust the pH to 9.0 by the pH meter 3-4. At the same time, the steam valve 3-12 is opened, and the stirring is heated until the solid is completely dissolved. Then, 567 kg of ammonium carbonate (containing about 30 wt% of NH3) is continuously added, and the stirring is continued for 90 min after the temperature is reduced to 30 DEG C. After the reaction is completed, the slurry in the crystal transformation reaction tank 3-6 is subjected to solid-liquid separation in the solid-liquid separation device 3-9 to obtain high-purity ammonium metavanadate solid.

[0099] (3) The ammonium metavanadate is dried in the drying device 4-1, and is calcined in the calcining device 4-4, the calcining temperature is 550 DEG C, and the calcining time is 2 h. After the calcining is completed, the calcined product is subjected to chemical detection analysis.

[0100]

[0101] (Unit: %) (4) The calcined product obtained in step (3) is electrolyzed in an electrolysis system to obtain a vanadium electrolyte. The obtained electrolyte fails to meet the requirements of the national standard GB / T 37204-2018 “Electrolyte for all-vanadium redox flow battery”.

[0102] Comparative Example Two: (1) 10 m 3 of sodium vanadate solution is pumped into the vanadium precipitation reaction tank 2-6, 573 kg of ammonium sulfate is added, and stirring is started. After the ammonium sulfate is completely dissolved, sulfuric acid is added from the pH regulator storage tank 2-5 to the vanadium precipitation reaction tank 2-6, the pH is controlled to 5.5 by the pH meter 2-2, and the temperature is controlled to 20°C by the thermometer 2-3. The stirring is continued for 60 min. After the stirring is completed, the slurry in the vanadium precipitation reaction tank 2-6 is subjected to solid-liquid separation in the solid-liquid separation device 2-8 to obtain ammonium sodium decavanadate (NH4)4Na2V 10 O 28 solid. The ammonium sodium decavanadate solid is detected to contain 10.12% water and 40.21% vanadium.

[0103] (2) The pure water valve 3-2 is opened, 4 m 3 of pure water is added to the crystal transformation reaction tank 3-6, 742 kg of ammonium sodium decavanadate solid is added to the crystal transformation reaction tank 3-6 through the feeding belt 3-1, 567 kg of ammonium carbonate (containing about 30 wt% NH3) is added, and sulfuric acid solution is added to adjust the pH to 2.5 by the pH meter 3-4. The steam valve 3-12 is opened, and the temperature is heated to 96°C. The stirring is continued for 80 min. After the reaction is completed, the slurry in the crystal transformation reaction tank 3-6 is subjected to solid-liquid separation in the solid-liquid separation device 3-9 to obtain high-purity APV solid (ammonium polyvanadate).

[0104] (3) The APV is dried in the drying device 4-1 and calcined in the calcining device 4-4. The calcining temperature is 550°C, and the calcining time is 2 h. After the calcining is completed, the calcined product is subjected to chemical detection analysis.

[0105]

[0106] (unit: %) (4) The calcined product obtained in step (3) is electrolyzed in an electrolysis system to obtain a vanadium electrolyte. The obtained electrolyte fails to meet the requirements of the national standard GB / T 37204-2018 “Electrolyte for all-vanadium redox flow battery”.

[0107] Example Two: (1) 10 m 3The basic vanadium solution is opened for stirring and 422 kg of ammonium chloride is added from the ammonium salt storage bin 2-4 to the vanadium precipitation reaction tank 2-6 (the mass ratio of ammonium to V in the basic vanadium solution is 0.3), after the ammonium chloride is completely dissolved, hydrochloric acid is added from the pH regulator storage tank 2-5 to the vanadium precipitation reaction tank 2-6, the pH of the solution is controlled to be 5.0 by the pH meter 2-2, the temperature of the solution is controlled to be 35°C by the thermometer 2-3, and the stirring is continued for 75 min. After the stirring is completed, the slurry in the vanadium precipitation reaction tank 2-6 is pumped into the solid-liquid separation device 2-8 by the slurry pump 2-7 for solid-liquid separation, and ammonium sodium decavanadate (NH4)4Na2V 10 O 28 The solid, the filtrate and the washing liquid generated in the process are pumped into the wastewater treatment process. It is detected that the ammonium sodium decavanadate solid contains 9.9% of water and 41.02% of vanadium.

[0108] (2) 178 kg of ammonium chloride and 4 m 3 Pure water is added to the crystal modifier storage tank 3-7 to configure a 15 g / L ammonium chloride solution, and the pH is adjusted to 8.0 with sodium hydroxide and added to the crystal modification reaction tank 3-6, and then 1110 kg of ammonium sodium decavanadate solid is added to the crystal modification reaction tank 3-6 through the feeding belt 3-1 (the solid-liquid ratio is 1:4), and the mixture is stirred uniformly, the steam valve 3-12 is opened to heat the material, the temperature of the solution is controlled to be 93°C by the thermometer 3-5, and the stirring is continued for 105 min. After the stirring is completed, the slurry in the crystal modification reaction tank 3-6 is pumped into the solid-liquid separation device 3-9 by the slurry pump 3-8 for solid-liquid separation, and high-purity ammonium metavanadate solid is obtained, and the filtrate and washing liquid generated in the process are pumped into the vanadium slag leaching process.

[0109] (3) The high-purity ammonium metavanadate product in the solid-liquid separation device 3-9 is sent to the drying device 4-1 for drying through the feeding belt 3-11, and the dried product is sent to the calcining device 4-4 for calcining from the storage bin 4-3, the calcining temperature is 525°C, and the calcining time is 2.5 h. After calcining, the calcined product is subjected to chemical detection analysis.

[0110]

[0111] (Unit: %) (4) The calcined product obtained in step (3) is electrolyzed in the electrolysis system 5-1 to obtain vanadium electrolyte, and it is detected that the quality of the obtained electrolyte meets the requirements of national standard GB / T 37204-2018 "Electrolyte for all-vanadium redox flow battery" first-class product.

[0112] Example Three: (1) 10 m 3The basic vanadium solution is opened for stirring and 510 kg of ammonium nitrate is added from the ammonium salt storage bin 2-4 to the vanadium precipitation reaction tank 2-6 (the mass ratio of ammonium to V in the basic vanadium solution is 0.2), after the ammonium nitrate is completely dissolved, nitric acid is added from the pH regulator storage tank 2-5 to the vanadium precipitation reaction tank 2-6, the pH of the solution is controlled to be 4.5 by the pH meter 2-2, the temperature of the solution is controlled to be 50°C by the thermometer 2-3, and the stirring is continued for 90 min. After the stirring is completed, the slurry in the vanadium precipitation reaction tank 2-6 is pumped into the solid-liquid separation device 2-8 by the slurry pump 2-7 for solid-liquid separation, and ammonium sodium decavanadate (NH4)4Na2V 10 O 28 The solid, the filtrate and the washing liquid generated in the process are pumped into the wastewater treatment process. It is detected that the ammonium sodium decavanadate solid contains 9.2% of water and 41.29% of vanadium.

[0113] (2) 622 kg of ammonium nitrate and 4 m 3 Pure water is added to the crystal modifier storage tank 3-7 to configure a 35 g / L ammonium nitrate solution, and the pH is adjusted to 10.0 with sodium hydroxide and added to the crystal modification reaction tank 3-6, and then 629 kg of ammonium sodium decavanadate solid is added to the crystal modification reaction tank 3-6 through the feeding belt 3-1 (the solid-liquid ratio is 1:7), and the mixture is stirred uniformly, the steam valve 3-12 is opened to heat the material, the temperature of the solution is controlled to be 97°C by the thermometer 3-5, and the stirring is continued for 60 min. After the stirring is completed, the slurry in the crystal modification reaction tank 3-6 is pumped into the solid-liquid separation device 3-9 by the slurry pump 3-8 for solid-liquid separation, and high-purity ammonium metavanadate solid is obtained, and the filtrate and washing liquid generated in the process are pumped into the vanadium slag leaching process.

[0114] (3) The high-purity ammonium metavanadate product in the solid-liquid separation device 3-9 is sent to the drying device 4-1 through the feeding belt 3-11 for drying, and the dried product is sent to the calcining device 4-4 from the storage bin 4-3 for calcining, the calcining temperature is 575°C, and the calcining time is 1.5 h. After calcining, the calcined product is subjected to chemical detection analysis.

[0115]

[0116] (Unit: %) (4) The calcined product obtained in step (3) is electrolyzed in the electrolysis system 5-1 to obtain a vanadium electrolyte, and it is detected that the quality of the obtained electrolyte meets the requirements of the national standard GB / T 37204-2018 "Electrolyte for all-vanadium redox flow battery".

[0117] Example Four: (1) 10 m 3The basic vanadium solution is opened for stirring, and 487 kg of ammonium carbonate (containing NH3 about 30wt%) is added from the ammonium salt storage bin 2-4 to the vanadium precipitation reaction tank 2-6 (the mass ratio of ammonium to V in the basic vanadium solution is 0.33), and after the ammonium carbonate is completely dissolved, carbonic acid is added from the pH regulator storage tank 2-5 to the vanadium precipitation reaction tank 2-6, the pH of the solution is controlled to be 4.0 by the pH meter 2-2, and the temperature of the solution is controlled to be 85°C by the thermometer 2-3, and the stirring is continued for 30 min. After the stirring is finished, the slurry in the vanadium precipitation reaction tank 2-6 is pumped into the solid-liquid separation device 2-8 by the slurry pump 2-7 for solid-liquid separation, and ammonium sodium decavanadate (NH4)4Na2V10O38 is obtained. 10 O 28 The solid, the filtrate and the washing liquid generated in the process are pumped into the wastewater treatment process. It is detected that the ammonium sodium decavanadate solid contains water 10.34% and vanadium 39.88%.

[0118] (2) 189 kg of ammonium carbonate and 4 m 3 Pure water is added to the crystal modifier storage tank 3-7 to configure an ammonium carbonate solution with a concentration of 15 g / L and is added to the crystal modification reaction tank 3-6, and then 558 kg of ammonium sodium decavanadate solid is added to the crystal modification reaction tank 3-6 through the feeding belt 3-1 (the solid-liquid ratio is 1:8), and the mixture is stirred uniformly, the steam valve 3-12 is opened to heat the material, the temperature of the solution is controlled to be 90°C by the thermometer 3-5, and the stirring is continued for 120 min. After the stirring is finished, the slurry in the crystal modification reaction tank 3-6 is pumped into the solid-liquid separation device 3-9 by the slurry pump 3-8 for solid-liquid separation, and high-purity ammonium metavanadate solid is obtained, and the filtrate and washing liquid generated in the process are pumped into the vanadium slag leaching process.

[0119] (3) The high-purity ammonium metavanadate product in the solid-liquid separation device 3-9 is sent to the drying device 4-1 through the feeding belt 3-11 for drying, and after drying, the product is sent to the calcining device 4-4 from the storage bin 4-3 for calcining, the calcining temperature is 600°C, and the calcining time is 1 h. After calcining, the calcined product 1# is subjected to chemical detection analysis.

[0120]

[0121] (unit: %) (4) The calcined product obtained in step (3) is electrolyzed in the electrolysis system 5-1 to obtain vanadium electrolyte, and it is detected that the quality of the obtained electrolyte meets the requirements of national standard GB / T 37204-2018 "Electrolyte for all-vanadium redox flow battery".

[0122] Example Five: (1) 10 m 3The basic vanadium solution is stirred and 1052 kg of ammonium bicarbonate (the mass ratio of ammonium to V in the basic vanadium solution is 0.4) is added from the ammonium salt storage bin 2-4 to the vanadium precipitation reaction tank 2-6. After the ammonium bicarbonate is completely dissolved, carbon dioxide gas is continuously introduced into the vanadium precipitation reaction tank 2-6 through an external pipeline, the pH of the solution is controlled to be 6.0 by the pH meter 2-2, and the temperature of the solution is controlled to be 65°C by the thermometer 2-3. Stirring is continued for 45 min. After the stirring is completed, the slurry in the vanadium precipitation reaction tank 2-6 is pumped into the solid-liquid separation device 2-8 by the slurry pump 2-7 for solid-liquid separation, and ammonium sodium decavanadate (NH4)4Na2V 10 O 28 The solid, the filtrate and the washing liquid generated in the process are pumped into the wastewater treatment process. It is detected that the ammonium sodium decavanadate solid contains 10.22% of water and 40.04% of vanadium.

[0123] (2) 1222 kg of ammonium bicarbonate and 4 m 3 Pure water is added to the crystal modifier storage tank 3-7 to prepare a 55 g / L ammonium bicarbonate solution, which is then added to the crystal modification reaction tank 3-6. Then, 891 kg of ammonium sodium decavanadate solid is added to the crystal modification reaction tank 3-6 through the feeding belt 3-1 (the solid-liquid ratio is 1:5), and the mixture is stirred uniformly. The steam valve 3-12 is opened to heat the material, and the temperature of the solution is controlled to be 95°C by the thermometer 3-5. Stirring is continued for 75 min. After the stirring is completed, the slurry in the crystal modification reaction tank 3-6 is pumped into the solid-liquid separation device 3-9 by the slurry pump 3-8 for solid-liquid separation, and high-purity ammonium metavanadate solid is obtained. The filtrate and washing liquid generated in the process are pumped into the vanadium slag leaching process.

[0124] (3) The high-purity ammonium metavanadate product in the solid-liquid separation device 3-9 is sent to the drying device 4-1 through the feeding belt 3-11 for drying, and the dried product is sent to the calcination device 4-4 from the storage bin 4-3 for calcination at a calcination temperature of 500°C for 3 h. After calcination, the calcined product 1# is subjected to chemical detection analysis.

[0125]

[0126] (Unit: %) (4) The calcined product obtained in step (3) is electrolyzed in the electrolysis system 5-1 to obtain a vanadium electrolyte. It is detected that the quality of the obtained electrolyte meets the requirements of the national standard GB / T 37204-2018 "Electrolyte for all-vanadium redox flow battery".

[0127] From the results of the above embodiment one and comparative example one, it can be seen that: in the preparation process of high-purity ammonium metavanadate, the solid phase crystallization method has significant advantages compared with the liquid phase crystallization method, and the solid phase crystallization process is more conducive to improving the purity of the precipitate, so that high-purity vanadium pentoxide meeting the use requirements of vanadium battery electrolyte can be prepared.

[0128] From the results of the above embodiment one and comparative example two, it can be seen that: in the solid phase crystallization ammonium sodium replacement process, pH plays a crucial role in product control, when ammonium carbonate is used as a crystallization agent, the solution pH itself is 8-10, and the product is ammonium metavanadate, and when the pH is adjusted to 2.5, the product is ammonium polyvanadate.

[0129] Figure 5 The XRD patterns of the crystallization products under different reaction times in the solid phase crystallization ammonium sodium replacement process are shown in the figure. As can be seen from the figure, when the reaction time is 10 min, the XRD shows the characteristic peaks of NH4VO3, and the product is pure phase NH4VO3. It shows that the solid phase crystallization rule is (NH4)4Na2V 10 O 28 →NH4VO3, and does not need to pass through an intermediate product conversion.

[0130] Figure 6 The XRD patterns of the products of steps (1), (2) and (3) in embodiment one are shown in the figure. As can be seen from the figure, the product of step (1) is ammonium sodium decavanadate, the product of step (2) is ammonium metavanadate, and the product of step (3) is vanadium pentoxide.

[0131] Figure 7 The SEM image of the product of step (1) in embodiment one is shown in the figure. As can be seen from the figure, the product of step (1) (i.e. ammonium sodium decavanadate) is a triclinic crystal.

[0132] Figure 8 The SEM image of the product of step (2) in embodiment one is shown in the figure. As can be seen from the figure, the product of step (2) (i.e. ammonium metavanadate) is an orthorhombic crystal.

[0133] Figure 9 The SEM image of the product of step (3) in embodiment one is shown in the figure. As can be seen from the figure, the product of step (3) (i.e. high-purity vanadium pentoxide) is an orthorhombic crystal.

[0134] In summary, the present application has the following advantages compared with the prior art: 1. This invention innovatively employs a one-step vanadium precipitation process to prepare high-purity vanadium pentoxide, which is then used to prepare vanadium electrolyte. Its significant advantage lies in eliminating the chlorination, ion exchange, extraction, and chemical purification steps inherent in conventional high-purity vanadium preparation processes. The process introduces no impurity ions, generates no new solid waste, and completely avoids chlorine and organic pollution. The entire process is simple, requires minimal equipment, is environmentally friendly, and highly meets the requirements of industrial production.

[0135] 2. This invention uses alkaline vanadium solution as raw material. Compared with the preparation of high-purity vanadium pentoxide and vanadium electrolyte using vanadium intermediates or crude products, it uses the most basic primary raw material in the vanadium industry chain, which not only significantly reduces production costs, but also has a wide range of adaptability to raw materials, thus helping the vanadium industry to develop rapidly.

[0136] 3. This invention innovatively proposes a core impurity removal technology based on solid-phase to crystalline ammonium sodium substitution, achieving a comprehensive reduction in major impurity elements such as K, Na, Si, and Cr in the product. The purity of the high-purity vanadium pentoxide product is greater than 99.9%, achieving deep impurity removal. The vanadium electrolyte prepared with this high-purity vanadium pentoxide exhibits excellent electrochemical performance and low cost. Furthermore, this high-purity vanadium pentoxide can fully meet the stringent purity requirements of various vanadium-based new materials.

[0137] 4. The solid-phase crystallization sodium ammonium replacement technology proposed in this invention uses at least one of ammonium carbonate and ammonium bicarbonate as the crystallization agent. The pH of the ammonium carbonate and ammonium bicarbonate solutions is 8-10. Therefore, there is no need to adjust the solution pH during the process, and (NH4)4Na2V can be directly converted into sodium carbonate. 10 O 28 The crystallization process yields NH4VO3, during which the solid product does not completely dissolve. The method is simple and has excellent impurity removal effect.

[0138] Finally, it should be noted that the embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a vanadium battery electrolyte, characterized in that, Includes the following steps: S1: Add ammonium salt to alkaline vanadium solution, adjust the pH to 4-6 using a pH adjuster, and carry out a weakly acidic ammonium salt precipitation reaction at a temperature of 20-85℃ to obtain sodium decavanadate solid. S2: The sodium decavanadate solid is mixed with a crystallizer solution containing ammonium ions, and a solid-phase crystallization sodium substitution reaction is carried out under the conditions of pH 8~10 and temperature 90~100℃ to obtain high-purity ammonium metavanadate solid. S3: Calcining the high-purity ammonium metavanadate solid to obtain high-purity vanadium pentoxide; S4: Electrolyze the high-purity vanadium pentoxide to obtain a vanadium battery electrolyte.

2. The method for preparing the vanadium battery electrolyte according to claim 1, characterized in that, In step S1, the ammonium salt is at least one of ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, and ammonium bicarbonate. The amount of ammonium salt added is (0.2~0.4):1 based on the mass ratio of ammonium ions to V in the alkaline vanadium solution. The pH adjuster is at least one of sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, and carbon dioxide. The reaction time is 30~90 min.

3. The method for preparing the vanadium battery electrolyte according to claim 2, characterized in that, In step S1, the amount of ammonium salt added is (0.27~0.33):1 based on the mass ratio of ammonium ions to V in alkaline vanadium solution, the pH is 5~5.5, the temperature is 20~40℃, and the reaction time is 60min.

4. The method for preparing the vanadium battery electrolyte according to claim 1, characterized in that, In step S2, the concentration of ammonium ions in the ammonium-containing crystallizer solution is 15~55 g / L, the solid-liquid ratio of the sodium decavanadate solid to the ammonium-containing crystallizer solution is 1:(4~8) in grams and milliliters, the ammonium-containing crystallizer solution is at least one of ammonium sulfate solution, ammonium chloride solution, ammonium nitrate solution, ammonium carbonate solution, and ammonium bicarbonate solution, and the reaction time is 60~120 min.

5. The method for preparing the vanadium battery electrolyte according to claim 4, characterized in that, In step S2, the concentration of ammonium ions in the ammonium-containing crystallizer solution is 35~45 g / L, the solid-liquid ratio of the sodium decavanadate solid to the ammonium-containing crystallizer solution is 1:6 in grams to milliliters, the temperature is 100℃, and the reaction time is 90 min.

6. The method for preparing the vanadium battery electrolyte according to claim 1, characterized in that, In step S3, the calcination temperature is 500~600℃ and the calcination time is 1~3h.

7. The method for preparing the vanadium battery electrolyte according to claim 1, characterized in that, Step S4 includes: placing the mixture of high-purity vanadium pentoxide and sulfuric acid solution into the negative electrode storage tank of the electrolysis device, adjusting the total vanadium concentration to 1.5~1.7 mol / L, adding sulfuric acid solution with the same acidity as the negative electrode to the positive electrode storage tank, and applying the solution at a current density of 100~500 mA / cm². 2 Under constant current electrolysis conditions, the vanadium battery electrolyte is obtained by valence state of 3.

5.

8. A vanadium battery electrolyte, characterized in that, The vanadium battery electrolyte is prepared using the preparation method described in any one of claims 1-4.

9. A system for preparing a vanadium battery electrolyte, characterized in that, A method for preparing vanadium battery electrolyte according to any one of claims 1-7, the preparation system comprising: A weakly acidic ammonium salt vanadium precipitation subsystem includes: a vanadium precipitation reaction tank for carrying out the weakly acidic ammonium salt vanadium precipitation reaction; an ammonium salt storage tank for adding ammonium salt to the vanadium precipitation reaction tank; a pH adjuster storage tank for adding pH adjuster to the vanadium precipitation reaction tank; a pH meter for detecting the pH of the slurry in the vanadium precipitation reaction tank; a vanadium precipitation temperature control device for controlling the temperature of the slurry in the vanadium precipitation reaction tank; and a vanadium precipitation solid-liquid separation device fluidly connected to the vanadium precipitation reaction tank for solid-liquid separation of the products after the vanadium precipitation reaction. A solid-phase crystallization sodium ammonium substitution subsystem includes: a crystallization reaction tank for receiving solid sodium decavanadate obtained after solid-liquid separation from the vanadium precipitation solid-liquid separation device and performing a solid-phase crystallization sodium ammonium substitution reaction on it; a crystallization agent storage tank for adding a crystallization agent solution containing ammonium ions to the crystallization reaction tank; a pH meter for detecting the pH of the slurry in the crystallization reaction tank; a crystallization temperature control device for controlling the temperature of the slurry in the crystallization reaction tank; and a crystallization solid-liquid separation device fluidly connected to the crystallization reaction tank for solid-liquid separation of the product after the substitution reaction. The vanadium pentoxide preparation subsystem includes: a drying device for receiving and drying high-purity ammonium metavanadate obtained after solid-liquid separation from the crystallization solid-liquid separation device; a calcination device for receiving and calcining the dried high-purity ammonium metavanadate from the drying device; and a vanadium pentoxide storage silo for receiving high-purity vanadium pentoxide produced after calcination from the calcination device. An electrolyte preparation subsystem includes: an electrolysis system that receives high-purity vanadium pentoxide from the vanadium pentoxide storage silo and electrolyzes the high-purity vanadium pentoxide, and a vanadium electrolyte storage tank for storing the vanadium battery electrolyte obtained by electrolysis.

10. The vanadium battery electrolyte preparation system according to claim 9, characterized in that, It also includes one or more of the following: The vanadium slag leaching subsystem is used to leach vanadium slag to obtain alkaline vanadium crude liquor. The solid-phase crystallization sodium ammonium sodium replacement subsystem is connected to the vanadium slag leaching subsystem and is used to supply the filtrate and washing water generated after solid-liquid separation to it for leaching vanadium slag. A raw material pretreatment subsystem is used to pretreat the crude alkaline vanadium solution and supply the pretreated alkaline vanadium solution to the weakly acidic ammonium salt vanadium precipitation subsystem. The raw material pretreatment subsystem includes: a storage tank for storing the crude alkaline vanadium solution, a filter device for filtering the crude alkaline vanadium solution to remove suspended solids, and a buffer tank for storing the filtered alkaline vanadium solution. The buffer tank is fluidly connected to the vanadium precipitation reaction tank of the weakly acidic ammonium salt vanadium precipitation subsystem to supply the alkaline vanadium solution to it. A steam injection subsystem, which is connected to the weakly acidic ammonium salt vanadium precipitation subsystem and the solid-phase crystallization ammonium sodium replacement subsystem, is used to inject steam into the vanadium precipitation reaction vessel of the weakly acidic ammonium salt vanadium precipitation subsystem and the crystallization reaction vessel of the solid-phase crystallization ammonium sodium replacement subsystem to control the reaction temperature. A pure water supply subsystem is connected to the weakly acidic ammonium salt vanadium precipitation subsystem, the solid-phase crystallization ammonium sodium replacement subsystem, and the vanadium pentoxide preparation subsystem, and is used to supply pure water to the vanadium precipitation solid-liquid separation device of the weakly acidic ammonium salt vanadium precipitation subsystem, the crystallization reaction tank of the solid-phase crystallization ammonium sodium replacement subsystem, and the crystallization solid-liquid separation device; A wastewater treatment subsystem, connected to the vanadium precipitation solid-liquid separation device of the weakly acidic ammonium salt vanadium precipitation subsystem, is used to receive and treat the filtrate and washing water generated after solid-liquid separation.

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