A method for preparing an electrolyte for an all-vanadium redox flow battery

Abstract

This invention belongs to the field of flow batteries, specifically relating to a method for preparing an electrolyte for a vanadium redox flow battery. The method involves mixing and calcining vanadium slag, sodium carbonate, and magnesium oxide; adding the calcined mixture to dilute sulfuric acid, heating and stirring, and filtering to obtain a leachate; adjusting the pH of the leachate to acidic, separating the solid and liquid phases, adding the precipitate to a phosphoric acid-based extractant, and extracting to obtain a chromium-vanadium raffinate; adjusting the pH of the chromium-vanadium raffinate to strongly acidic, adding an amine extractant, and extracting to obtain a vanadium-containing raffinate; adjusting the pH of the vanadium-containing raffinate to 2-4, and passing it through an ion exchange resin to obtain a saturated ion exchange resin; and using a mixed acid of sulfurous acid and sulfuric acid to precipitate the saturated ion exchange resin to obtain the vanadium redox flow battery electrolyte. This method produces an electrolyte with high purity, involves simple steps, and does not generate ammonia nitrogen wastewater or waste gas.

Description

Technical Field

[0001] This invention belongs to the field of flow batteries, specifically relating to a method for preparing an electrolyte for an all-vanadium redox flow battery. Background Technology

[0002] With the rapid development of new energy sources such as wind and solar power, their volatility poses challenges to the stable operation of the power system and the balance between supply and demand. Long-term energy storage, with its long cycle and large capacity characteristics, can smooth out the fluctuations caused by new energy power generation over a long period of time, ensuring power supply during seasonal and extreme weather conditions.

[0003] Energy storage technology is an effective solution to the volatility and intermittency of new energy systems, primarily wind and solar power. It plays a crucial supporting role in establishing new power systems and has significant strategic importance. With the increasing installed capacity and power generation ratio of new energy sources, the requirements for energy storage duration are becoming increasingly stringent, leading to a growing demand for capacity-based energy storage. There are various long-duration energy storage technologies, including pumped hydro storage, compressed air storage, flow battery storage, thermal energy storage, and hydrogen storage. These technologies provide strong support for the large-scale utilization of renewable energy. Among them, flow battery energy storage technology is relatively mature and basically ready for large-scale development. The electrolyte, as the electrolyte in a flow battery, plays a vital role in battery performance.

[0004] To achieve vanadium enrichment during vanadium extraction, solvent extraction or ion exchange are commonly used processes. For example, Cheng Qian (Vanadium extraction from acid leaching solution of vanadium shale coal using D201 resin [J]. Nonferrous Metals, 2022, 5: 38-41.) used D201 resin to adsorb pentavalent vanadium, followed by desorption using a mixed solution of sodium hydroxide and sodium chloride to obtain sodium vanadate solution. This process requires multiple steps such as precipitation, roasting, dissolution, and reduction to obtain vanadium electrolyte, which is cumbersome and results in high electrolyte production costs.

[0005] Chinese invention patent document CN114243042A discloses a method for preparing vanadium electrolyte through ammonium-free, liquid-cycle vanadium extraction. The vanadium source material is leached with sodium calcination to obtain a vanadium-containing leachate. This leachate is then reduced by adding an electrolytic current or a reducing agent. Vanadium is then enriched through extraction, and the electrolyte is obtained through back-extraction. However, this electrolytic reduction method has high energy consumption, requires a large amount of additional reducing agent, has low utilization, and the metal reducing agent easily introduces impurities into the electrolyte, affecting battery performance.

[0006] Chinese invention patent document with publication number CN119465181A discloses a method for preparing a full vanadium electrolyte. Vanadium slag is leached with alkali and precipitated with ammonium salt to obtain vanadium oxide. The vanadium oxide is then dissolved and electrocatalytically reduced. The process generates ammonia nitrogen wastewater and is cumbersome. Impurities are present during the vanadium precipitation process. At the same time, a large amount of ammonia gas is generated during the roasting of vanadium oxide, causing environmental pollution. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing an electrolyte for a vanadium redox flow battery. This method utilizes a mixed acid cycle of sulfurous acid and sulfuric acid to prepare an electrolyte with high purity and high concentration. The steps are simple, no additional reducing agent is required, and it is economically beneficial and environmentally friendly.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention provides a method for preparing an electrolyte for an all-vanadium redox flow battery, comprising the following steps:

[0010] (1) Mix and roast vanadium slag, sodium carbonate and magnesium oxide, add the roasted mixture to dilute sulfuric acid, heat and stir, filter and obtain leachate;

[0011] (2) Adjust the pH of the leachate to acidic, separate the solid and liquid, add phosphoric acid extractant to the liquid, and extract to obtain chromium-vanadium raffinate;

[0012] (3) Adjust the pH of the chromium-vanadium raffinate to 0.5-1.5, add an amine extractant, and extract to obtain the vanadium-containing raffinate;

[0013] (4) Adjust the pH of the vanadium-containing raffinate to 2-4 and pass it through an impregnated ion exchange resin to obtain a saturated ion exchange resin;

[0014] (5) The saturated ion exchange resin was cyclically desorbed using a mixture of sulfurous acid and sulfuric acid. The molar ratio of vanadium adsorbed by the saturated ion exchange resin to sulfurous acid was 1:0.5-0.6, and the molar ratio of sulfurous acid to sulfuric acid was 1:1-2, thus obtaining the electrolyte for the vanadium redox flow battery.

[0015] Preferably, in step (1), the mass ratio of vanadium slag, sodium carbonate, and magnesium oxide is 1:0.3 to 1:0.1 to 0.5; the calcination temperature is 600 to 750°C; the concentration of dilute sulfuric acid is 0.5 to 1 mol / L; and the mass ratio of the mixture to dilute sulfuric acid is 1:3 to 5.

[0016] Preferably, in step (2), the pH of the leachate is adjusted within the range of 1.8 to 3; the phosphoric acid extractant is any one of P204, Cyanex 272, and P538.

[0017] Preferably, in step (3), the amine extractant is one of N1923 and O216.

[0018] Preferably, in step (4), the pH range of the vanadium-containing raffinate is 2 to 3; and the ion exchange resin is one of D202, D453, and D301.

[0019] Preferably, in step (5), the desorption is repeated 4 to 6 times.

[0020] Preferably, in step (4), the preparation steps of the impregnated ion exchange resin are as follows: the ion exchange resin and the chelating extractant are placed in a reaction vessel and impregnated at a constant temperature to obtain the impregnated ion exchange resin.

[0021] More preferably, in step (4), the chelating extractant is one of LIX 63 and LIX 860; the volume ratio of ion exchange resin to chelating extractant is 1:1 to 2; the temperature is 60 to 90°C; and the soaking time is 6 to 12 hours.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention employs impregnated ion exchange resin to enrich vanadium, and uses a mixed acid of sulfurous acid and sulfuric acid for cyclic desorption to prepare the electrolyte. During the desorption process, sulfurous acid acts as a reducing agent, reducing pentavalent vanadium on the ion exchange resin to tetravalent vanadium. It also acts as a supporting electrolyte, directly yielding a vanadium oxysulfate electrolyte. Compared to existing technologies that use alkaline solutions for electrolyte preparation, this method eliminates the need for additional reducing agents, avoids the introduction of impurity ions, has a shorter process flow, is simpler to operate, and has lower production costs. Furthermore, the cyclic desorption method significantly increases the vanadium concentration in the mixed acid solution. The inventors discovered that the sulfurous acid content in the mixed acid should not be too high, and the molar ratio of vanadium to sulfurous acid adsorbed by the saturated ion exchange resin should be controlled at 1:0.5–0.6. This ensures not only complete vanadium reduction but also prevents excessive residual sulfurous acid, avoiding the reduction and desorption of trace impurity ions other than vanadium into the electrolyte.

[0024] This invention achieves high-purity vanadium electrolyte through a step-by-step separation of impurity elements. First, magnesium oxide is added during the roasting process to effectively inhibit the removal of silicon, an impurity element. Magnesium oxide reacts with silicon in the vanadium slag to form magnesium silicate. Next, the roasted mixture is leached in dilute sulfuric acid. During leaching, magnesium silicate reacts with sulfuric acid, and silicon is converted into a precipitate that is removed by filtration, preventing its introduction into the electrolyte. This process lowers the synthesis temperature of soluble vanadium compounds, i.e., reduces the roasting temperature, thereby reducing roasting energy consumption and minimizing the leaching of impurity elements. The magnesium element entering the leachate exists in cationic form, and the phosphoric acid extractant reacts with magnesium via hydrogen ions. Ion exchange was used to remove 99.2% of magnesium impurities. Simultaneously, a large amount of chromium (VI) was introduced during the leaching process. Since chromium and vanadium have similar properties and are difficult to separate, a strongly acidic environment was used to control the pH of the chromium-vanadium raffinate to 0.5–1.5. An amine extractant was then used to perform anion exchange with chromium, removing 99% of the impurities. In the subsequent adsorption and desorption process, the content of sulfurous acid was strictly controlled to inhibit the desorption of impurities, thus achieving a secondary impurity removal effect. The combined effect of the initial impurity removal and the sulfurous acid further improved the purity of the vanadium electrolyte.

[0025] This invention utilizes an impregnated ion exchange resin and a cyclic leaching method to obtain a high-concentration vanadium electrolyte. First, an impregnated ion exchange resin is used to adsorb vanadium. The extractant not only has a chelating effect, binding with vanadium in the vanadium-containing raffinate and assisting the ion exchange resin in vanadium exchange, but also, compared to traditional ion exchange resins, it increases the vanadium adsorption capacity. Furthermore, the dual combination of resin and extractant allows for a wider applicable pH range. The cyclic leaching of sulfurous acid further enhances the vanadium removal process, resulting in a high-concentration vanadium electrolyte.

[0026] This invention employs a closed-loop circulation design to achieve comprehensive utilization of vanadium slag, resulting not only in a high-concentration, high-purity vanadium electrolyte, but also in products such as ferric oxide, magnesium sulfate, and chromium trioxide, thus yielding extensive economic benefits.

[0027] (5) Existing technologies obtain vanadium compound precipitates by alkaline leaching or acid leaching with oxidative roasting, followed by roasting to obtain vanadium oxides. The vanadium oxides are then electrochemically or chemically reduced to obtain vanadium electrolyte. Impurities are introduced during the vanadium precipitation process and enter the vanadium electrolyte during the reduction process. At the same time, a large amount of ammonia nitrogen wastewater is generated during the vanadium precipitation process, and ammonia gas is released during the roasting of vanadium compound precipitates, polluting the environment. This invention does not require the addition of ammonium salts for vanadium compound precipitation, thus eliminating the generation of ammonia nitrogen wastewater and waste gas, making it environmentally friendly. The entire process is carried out in a liquid phase environment, eliminating the need for additional reducing agents, avoiding the introduction of impurity ions, simplifying the process, and significantly reducing the production cost of the electrolyte. Detailed Implementation

[0028] To make the objectives, technical solutions, and effects of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] The method for calculating the vanadium content adsorbed by a saturated ion exchange resin is as follows: First, the vanadium content in the vanadium extraction residue is obtained by ICP-OES test as n. Then, the vanadium content in the remaining aqueous phase after the vanadium extraction residue passes through the impregnated ion exchange resin is measured as m. The vanadium content adsorbed by the saturated ion exchange resin is measured as nm. Example 1

[0030] Preparation of all-vanadium redox flow battery electrolyte 1

[0031] (1) Vanadium slag, sodium carbonate and magnesium oxide are mixed in a mass ratio of 1:1:0.2 and roasted in a roasting furnace at 750°C. The mixture is then mixed with 1 mol / L sulfuric acid in a mass ratio of 1:4, heated and stirred, and filtered to obtain leachate.

[0032] (2) Adjust the pH of the leachate to 2.5 and separate the solid and liquid; add extractant P204 to extract magnesium element to obtain vanadium and chromium raffinate and magnesium-loaded organic phase;

[0033] (3) Adjust the pH of the vanadium raffinate to 0.9, add O216 extractant to extract chromium, and obtain vanadium raffinate and chromium-loaded organic phase. The vanadium content in the vanadium raffinate is 14 g / L by ICP-OES test.

[0034] (4) The total amount of vanadium in the vanadium extract was tested and the pH of the vanadium-containing raffinate was adjusted to 3. The raffinate was then passed through D202 resin impregnated with extractant LIX 63 (impregnation temperature was 80℃ and time was 10h) for adsorption. Saturated ion exchange resin was obtained. The vanadium content in the remaining aqueous phase was tested to be 0.03 g / L, and the vanadium adsorption capacity was calculated to be 13.97 g / L.

[0035] (5) The saturated ion exchange resin was cyclically analyzed 6 times using a mixed acid with a molar ratio of sulfurous acid and sulfuric acid of 1:1. The molar ratio of vanadium adsorbed by the saturated ion exchange resin to sulfurous acid was 1:0.5, thus obtaining the electrolyte for the all-vanadium redox flow battery. Example 2

[0036] Preparation of vanadium redox flow battery electrolyte 2

[0037] (1) Vanadium slag, sodium carbonate and magnesium oxide are mixed in a mass ratio of 1:0.6:0.3 and roasted in a roasting furnace at 750°C. The mixture is then mixed with 0.5 mol / L sulfuric acid in a mass ratio of 1:5, heated and stirred, and filtered to obtain leachate.

[0038] (2) Adjust the pH of the leachate to 2 and separate the solid and liquid components; add the extractant Cyanex 272 to extract magnesium to obtain vanadium- and chromium-containing raffinate and magnesium-loaded organic phase;

[0039] (3) The total amount of vanadium in the vanadium extract was tested and the pH of the chromium-containing vanadium raffinate was adjusted to 1.2. O216 extractant was added to extract chromium, and vanadium-containing raffinate and chromium-loaded organic phase were obtained. The vanadium content in the vanadium raffinate was 13.5 g / L by ICP-OES test.

[0040] (4) Adjust the pH of the vanadium-containing raffinate to 2.5 and pass it through D301 resin impregnated with extractant LIX 63 (impregnation temperature is 90℃, time is 6h) for adsorption; obtain saturated ion exchange resin; test the vanadium content in the remaining aqueous phase to be 0.04 g / L, and calculate the vanadium adsorption capacity to be 13.46 g / L;

[0041] (5) The saturated ion exchange resin was cyclically analyzed 5 times using a mixed acid with a molar ratio of sulfurous acid to sulfuric acid of 1:2. The molar ratio of vanadium adsorbed by the saturated ion exchange resin to sulfurous acid was 1:0.6, thus obtaining the electrolyte for the all-vanadium redox flow battery. Example 3

[0042] Preparation of vanadium redox flow battery electrolyte 3

[0043] (1) Vanadium slag, sodium carbonate and magnesium oxide are mixed in a mass ratio of 1:0.6:0.5 and roasted in a roasting furnace at 650°C. The mixture is then mixed with 0.6 mol / L sulfuric acid in a mass ratio of 1:3, heated and stirred, and filtered to obtain leachate.

[0044] (2) Adjust the pH of the leachate to 1.8 and separate the solid and liquid components; add extractant P538 to extract magnesium to obtain vanadium and chromium raffinate and magnesium-loaded organic phase;

[0045] (3) Adjust the pH of the vanadium-containing raffinate to 1.5, add N1923 extractant for chromium extraction, and obtain the vanadium-containing raffinate and the chromium-loaded organic phase. The vanadium content in the vanadium raffinate was 13.2 g / L by ICP-OES test.

[0046] (4) The total amount of vanadium in the vanadium extract was tested and the pH of the vanadium-containing raffinate was adjusted to 2. The vanadium was then passed through D301 resin impregnated with extractant LIX 860 for adsorption (impregnation temperature was 60℃ and time was 12h). Saturated ion exchange resin was obtained. The vanadium content in the remaining aqueous phase was tested to be 0.05 g / L, and the vanadium adsorption capacity was calculated to be 13.15 g / L.

[0047] (5) The saturated ion exchange resin was cyclically analyzed 4 times using a mixed acid with a molar ratio of sulfurous acid and sulfuric acid of 1:1. The molar ratio of vanadium adsorbed by the saturated ion exchange resin to sulfurous acid was 1:0.5 to obtain the electrolyte for the vanadium redox flow battery. Example 4

[0048] Preparation of vanadium redox flow battery electrolyte 4

[0049] (1) Vanadium slag, sodium carbonate and magnesium oxide are mixed in a mass ratio of 1:1:0.3 and roasted in a roasting furnace at 700°C. The mixture is then mixed with 1 mol / L sulfuric acid in a mass ratio of 1:5, heated and stirred, and filtered to obtain leachate.

[0050] (2) Adjust the pH of the leachate to 1.8 and perform solid-liquid separation;

[0051] (3) Adjust the pH of the vanadium raffinate to 0.6, add N1923 extractant to extract chromium, and obtain vanadium raffinate and chromium-loaded organic phase. The vanadium content in the vanadium raffinate is 13.8% by ICP-OES test.

[0052] (4) The total amount of vanadium in the vanadium extract was tested and the pH of the vanadium-containing raffinate was adjusted to 2. The vanadium was then passed through D453 resin impregnated with extractant LIX 860 (impregnation temperature was 70℃ and time was 10h) for adsorption. Saturated ion exchange resin was obtained. The vanadium content in the remaining aqueous phase was tested to be 0.04 g / L, and the vanadium adsorption capacity was calculated to be 13.76 g / L.

[0053] (5) The saturated ion exchange resin was cyclically analyzed 5 times using a mixed acid (5 mol / L concentration) with a volume ratio of sulfurous acid to sulfuric acid of 1:1.5. The molar ratio of vanadium adsorbed by the saturated ion exchange resin to sulfurous acid was 1:0.6, thus obtaining the electrolyte for the vanadium redox flow battery. Example 5

[0054] Preparation of vanadium redox flow battery electrolyte 5

[0055] (1) Vanadium slag, sodium carbonate and magnesium oxide are mixed in a mass ratio of 1:0.3:0.4 and roasted in a roasting furnace at 600°C. The mixture is then mixed with 0.8 mol / L sulfuric acid in a mass ratio of 1:5, heated and stirred, and filtered to obtain leachate.

[0056] (2) Adjust the pH of the leachate to 2.5 and separate the solid and liquid; add extractant P204 to extract magnesium element to obtain vanadium and chromium raffinate and magnesium-loaded organic phase;

[0057] (3) Adjust the pH of the vanadium raffinate to 1.2, add O216 extractant to extract chromium, and obtain vanadium raffinate and chromium-loaded organic phase. The vanadium content in the vanadium raffinate was 13.2 g / L by ICP-OES test.

[0058] (4) The total amount of vanadium in the vanadium extract was tested and the pH of the vanadium-containing raffinate was adjusted to 2.8. The vanadium was then passed through D202 resin impregnated with extractant LIX 63 (impregnation temperature was 80℃ and time was 8h) for adsorption. Saturated ion exchange resin was obtained. The vanadium content in the remaining aqueous phase was tested to be 0.02 g / L, and the vanadium adsorption capacity was calculated to be 13.18 g / L.

[0059] (5) The saturated ion exchange resin was cyclically analyzed 4 times using a mixed acid with a molar ratio of sulfurous acid and sulfuric acid of 1:1. The molar ratio of vanadium adsorbed by the saturated ion exchange resin to sulfurous acid was 1:0.5, thus obtaining the electrolyte for the all-vanadium redox flow battery. Comparative Example 1

[0060] Preparation of vanadium redox flow battery electrolyte 6

[0061] Step (4) Test the total amount of vanadium in the vanadium extract and adjust the pH of the vanadium-containing raffinate to 3, and pass it through D202 resin for adsorption; test the vanadium content in the remaining aqueous phase to be 1.32 g / L, and calculate the vanadium adsorption amount to be 12.68 g / L; the other conditions and calculation methods are the same as in Example 1. Comparative Example 2

[0062] Preparation of vanadium redox flow battery electrolyte 7

[0063] Step (4) Test the total amount of vanadium in the vanadium extract and adjust the pH of the vanadium-containing raffinate to 3. Use extractant LIX 63 for extraction. Test the vanadium content in the remaining aqueous phase to be 1.29 g / L and calculate the vanadium extraction amount to be 12.71 g / L. The remaining conditions and calculation methods are the same as in Example 1. Comparative Example 3

[0064] Preparation of vanadium redox flow battery electrolyte 8

[0065] The pH of the chromium-vanadium raffinate was adjusted to 0.3, and O216 extractant was added for chromium extraction to obtain a vanadium-containing raffinate and a chromium-loaded organic phase; the remaining conditions and calculation methods were the same as in Example 1. Comparative Example 4

[0066] Preparation of vanadium redox flow battery electrolyte 9

[0067] The pH of the chromium-vanadium raffinate was adjusted to 2.0, and O216 extractant was added for chromium extraction to obtain a vanadium-containing raffinate and a chromium-loaded organic phase; the remaining conditions and calculation methods were the same as in Example 1.

[0068] The physical parameters of the vanadium redox flow battery electrolytes prepared in Examples 1-5 and Comparative Examples 1-4 are listed in Table 1.

[0069]

[0070] In Example 1, the vanadium leaching rate was 95%. In Example 4, the mass ratio of vanadium slag to sodium carbonate and the sulfuric acid concentration were the same as in Example 1, but the roasting temperature was 700℃, lower than that in Example 1. The content of the soluble vanadium compounds generated was slightly lower, and the leaching rate was 94%. In Examples 2 and 3, the leaching rates were not significantly different, and the mass ratio of vanadium slag to sodium carbonate was 1:0.6. However, the magnesium oxide content in Example 3 was slightly higher. Even though the roasting temperature was 650℃, lower than that in Example 2, the leaching rate was not significantly affected, indicating that the addition of magnesium oxide can lower the roasting temperature.

[0071] Comparative Example 1 only passed through D202 resin for vanadium adsorption, while Comparative Example 2 only passed through extractant LIX 63 for vanadium extraction. Therefore, its enrichment of vanadium was relatively low, resulting in a low electrolyte concentration.

[0072] In Comparative Example 3, adjusting the pH of the chromium-vanadium raffinate to 0.3 resulted in a lower chromium removal rate, meaning some chromium remained unremoved, leading to a higher chromium content in the electrolyte. In Comparative Example 4, adjusting the pH of the chromium-vanadium raffinate to 2 caused vanadium co-extraction during chromium extraction, resulting in a lower electrolyte concentration than in Comparative Example 3.

Claims

1. A method for preparing an electrolyte for an all-vanadium redox flow battery, characterized in that, Includes the following steps: (1) Mix and roast vanadium slag, sodium carbonate and magnesium oxide, add the roasted mixture to dilute sulfuric acid, heat and stir, filter and obtain leachate; (2) Adjust the pH of the leachate to acidic, separate the solid and liquid, add phosphoric acid extractant to the liquid, and extract to obtain chromium-vanadium raffinate; (3) Adjust the pH of the chromium-vanadium raffinate to 0.5-1.5, add an amine extractant, and extract to obtain the vanadium-containing raffinate; (4) Adjust the pH of the vanadium-containing raffinate to 2-4 and pass it through an impregnated ion exchange resin to obtain a saturated ion exchange resin; (5) The saturated ion exchange resin was cyclically desorbed using a mixture of sulfurous acid and sulfuric acid. The molar ratio of vanadium adsorbed by the saturated ion exchange resin to sulfurous acid was 1:0.5-0.6, and the molar ratio of sulfurous acid to sulfuric acid was 1:1-2, thus obtaining the electrolyte for the vanadium redox flow battery. In step (4), the impregnated ion exchange resin is prepared by the following steps: placing the ion exchange resin and the chelating extractant in a reaction vessel and impregnating at a constant temperature to obtain the impregnated ion exchange resin; the chelating extractant is one of LIX 63 and LIX 860; the volume ratio of the ion exchange resin to the chelating extractant is 1:1 to 2, the temperature is 60 to 90°C, the impregnation time is 6 to 12 hours, and the ion exchange resin is one of D202, D453, and D301.

2. The method for preparing the all-vanadium redox flow battery electrolyte according to claim 1, characterized in that, In step (1), the mass ratio of vanadium slag, sodium carbonate, and magnesium oxide is 1:0.3 to 1:0.1 to 0.5; the roasting temperature is 600 to 750°C; the concentration of dilute sulfuric acid is 0.5 to 1 mol / L; and the mass ratio of the mixture to dilute sulfuric acid is 1:3 to 5.

3. The method for preparing the all-vanadium redox flow battery electrolyte according to claim 1, characterized in that, In step (2), the pH of the leachate is adjusted within the range of 1.8 to 3; the phosphoric acid extractant is any one of P204, Cyanex 272, and P538.

4. The method for preparing the all-vanadium redox flow battery electrolyte according to claim 1, characterized in that, In step (3), the amine extractant is one of N1923 and O216.

5. The method for preparing the all-vanadium redox flow battery electrolyte according to claim 1, characterized in that, In step (4), the pH range of the vanadium-containing raffinate is adjusted to 2-3.

6. The method for preparing the all-vanadium redox flow battery electrolyte according to claim 1, characterized in that, In step (5), the desorption is repeated 4 to 6 times.

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