A solid-state vanadium 3,5-valent electrolyte and its preparation method

Abstract

This invention provides a method for preparing solid vanadium 3.5-valent electrolyte, comprising: mixing VO2 powder and V3O5 powder, pressing them into blocks, and then calcining them to obtain the product. The VO2 powder is prepared by calcining solid VO(OH)2 in an inert atmosphere at 200-800°C for 4-8 hours. The V3O5 powder is prepared by calcining solid VO(OH)2 in a reducing atmosphere at 400-600°C for 4-6 hours, or by mixing solid VO(OH)2 with a two-stage reducing agent, pressing it into blocks, and then calcining it in an inert atmosphere at 400-800°C for 4-8 hours to obtain V3O5 powder. This invention offers precise valence control, high product consistency, wide raw material adaptability, low production cost, and is clean and environmentally friendly. The solid product significantly reduces transportation and storage costs. The rapid acid dissolution rate of solid V4O7 significantly improves the preparation efficiency of vanadium 3.5-valent electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of vanadium electrolyte manufacturing technology, specifically relating to a solid 3.5-valent vanadium electrolyte and its preparation method. Background Technology

[0002] Vanadium redox flow batteries (vanadium batteries) have become an important technology in large-scale energy storage due to their advantages such as high safety, long cycle life, and the ability to independently design power and capacity. Among the commonly used electrolyte systems in vanadium batteries, 3.5-valent vanadium electrolyte is currently the most widely used commercially. The mainstream production process for 3.5-valent vanadium electrolyte currently uses high-purity V₂O₅ as raw material, first chemically reducing V₂O₅... 5+ Restore to V 4+ The vanadium is then further electro-reduced to a 3.5 valence. This process not only requires high purity raw materials and consumes a large amount of reducing agent, but also has a lengthy process, especially with extremely high electricity consumption during electro-reduction, resulting in high production costs for vanadium electrolytes. More importantly, the vanadium electrolytes produced by traditional methods are liquid systems, containing approximately 70% water and a large amount of sulfuric acid, with a vanadium content of only 1.6~1.8 mol / L, accounting for only about 8.2-9.2% of the electrolyte by mass. This high water, high acid, and low vanadium characteristic makes the electrolyte subject to strict hazardous materials transportation regulations, especially the low effective vanadium content per unit volume, which greatly increases the transportation cost of vanadium electrolytes and has become a major bottleneck restricting the large-scale promotion and commercial application of vanadium battery technology. Therefore, reducing the preparation and transportation costs of vanadium electrolytes is of great significance.

[0003] Chinese patent CN121097155A discloses a method for preparing near-3.5 valent vanadium electrolyte by reducing ammonium metavanadate with coke oven gas. The method uses ammonium metavanadate as raw material, performs reduction and calcination using coke oven gas, and then removes ammonia through displacement to obtain near-3.5 valent vanadium oxide containing V₄O₇. Finally, sulfuric acid is added to dissolve the oxide to obtain the near-3.5 valent vanadium electrolyte. This method utilizes industrial by-product coke oven gas, resulting in lower raw material costs. However, this method struggles to precisely control the valence state of the product during the reduction process, yielding only a "near-3.5" valence rather than a precise 3.5 valence. After dissolving in acid, further adjustment of the vanadium electrolyte valence state is still required. Furthermore, the displacement and ammonia removal process generates difficult-to-treat ammonia-containing wastewater and waste gas, increasing treatment costs.

[0004] Chinese patent CN116995285A discloses a short-process method for preparing vanadium oxysulfate electrolyte with 3.5 valence. The method uses ammonium metavanadate and / or ammonium polyvanadate as raw materials, which are reduced and calcined with a reducing gas to obtain low-valence vanadium oxides. These oxides are then dissolved in sulfuric acid, and the vanadium valence state is adjusted to obtain the target vanadium electrolyte. However, this method still suffers from problems such as difficulty in precisely controlling the composition of the low-valence vanadium oxides, generation of ammonia-containing wastewater, and the frequent need for subsequent vanadium adjustment steps, increasing the complexity of on-site operations.

[0005] Chinese patent CN114361549A discloses a method for preparing vanadium electrolyte for all-vanadium redox flow batteries. The method involves reducing high-purity vanadium pentoxide with a reducing gas to obtain low-valence vanadium oxide, which is then mixed with an activator and heated to activate the electrolyte, resulting in a vanadium-containing paste-like electrolyte. Finally, water is added to dissolve the oxide. While this method is rapid and effective, it still requires high-purity vanadium pentoxide as a raw material, leading to higher costs. Furthermore, this method cannot precisely control the average valence state of the solid product to 3.5, making it difficult to guarantee the consistency of the electrolyte composition.

[0006] Chinese patent CN106684421A discloses a method for preparing vanadium electrolyte, using vanadium pentoxide as raw material, adding a reducing agent to carry out a reduction reaction, removing impurities through multiple water washing and acid washing, and then adding sulfuric acid and heating to dissolve. This method can obtain a high-purity electrolyte with extremely low impurity ion content, but the preparation process is lengthy, involving multiple washing and filtration processes, making the operation cumbersome, and generating a large amount of vanadium-containing waste acid, resulting in a heavy environmental impact. In particular, the valence state of vanadium remains difficult to control precisely.

[0007] Chinese patent CN117819603A discloses a method for preparing low-valent vanadium oxides through gas-solid combined reduction. The method involves first mixing high-valent vanadium solid with a reducing solid for a solid-phase reaction, followed by a gas-solid reaction with a mixture of methane and hydrogen. While this method can yield low-valent vanadium oxides at relatively low temperatures, its two-step reduction process (solid-phase followed by gas-phase) is relatively complex, increasing the difficulty of operational control, and making it difficult to precisely control the phase and valence state of the final product.

[0008] In summary, existing patented methods still have shortcomings in terms of raw material costs, precise control of price, process length, and clean production level, making it difficult to meet the comprehensive requirements of "low cost, precise control of 3.5 price, and clean and environmentally friendly". Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a solid 3.5-valent vanadium electrolyte and its preparation method, aiming to achieve at least one of the following effects: obtaining a +3.5 valent solid vanadium electrolyte with precise control through a simple process; generating no high-salt ammonia nitrogen wastewater or waste gas during production; facilitating the transportation of solid low-valent vanadium electrolyte; directly preparing 3.5-valent vanadium electrolyte by acid dissolution without adjusting the valence state; effectively reducing the production and transportation costs of vanadium electrolyte; and improving the preparation efficiency of 3.5-valent vanadium electrolyte.

[0010] According to one aspect of the present invention, a method for preparing a solid 3.5-valent vanadium electrolyte is provided, comprising the following steps:

[0011] VO2 powder and V3O5 powder are mixed in a molar ratio of 1:1 and pressed into blocks. Then, they are calcined at 400~800℃ for 4~10h under an inert atmosphere to obtain solid 3.5 vanadium electrolyte V4O7.

[0012] The VO2 powder is prepared through the following steps:

[0013] VO(OH)2 solid was calcined at 200-800℃ for 4-8 hours under an inert atmosphere to obtain VO2 powder;

[0014] The V3O5 powder was prepared by the following steps:

[0015] V3O5 powder is obtained by calcining solid VO(OH)2 in a reducing atmosphere at 400-600℃ for 4-6 hours; or by mixing solid VO(OH)2 with a two-stage reducing agent and pressing it into blocks, then calcining it in an inert atmosphere at 400-800℃ for 4-8 hours. The amount of the two-stage reducing agent added is 1-2 times the theoretical amount required for the reaction with solid VO(OH)2.

[0016] As a preferred embodiment of the preparation method of a solid 3.5 vanadium electrolyte of the present invention, the reducing atmosphere includes one or more of H2, NH3, and CO.

[0017] In a preferred embodiment of the preparation method of a solid 3.5-valent vanadium electrolyte of the present invention, the inert atmosphere includes argon.

[0018] As a preferred embodiment of the preparation method of solid 3.5 vanadium electrolyte of the present invention, the pressure of pressing into blocks is 50~200MPa, and the pressure of the blocks is 50~200MPa.

[0019] As a preferred embodiment of the preparation method of a solid 3.5-valent vanadium electrolyte of the present invention, the two-stage reducing agent includes one or more of oxalic acid and citric acid.

[0020] As a preferred embodiment of the preparation method of a solid 3.5-valent vanadium electrolyte of the present invention, the VO(OH)2 solid is prepared by the following method:

[0021] 1) Mix the vanadium-containing material with acid solution, adjust the pH of the mixture to ≤4, add a reducing agent at 1 to 5 times the theoretical required reaction amount, and stir the reaction at 200 to 400 rpm at 40 to 99°C for 0.5 to 5 hours to obtain a tetravalent vanadium solution.

[0022] 2) Adjust the pH of the tetravalent vanadium solution obtained in step 1) to 6~12, stir the reaction at 20~50℃ and 200~400rpm for 0.5~2h, and obtain solid VO(OH)2 after filtration and drying.

[0023] As a preferred embodiment of the preparation method of a solid 3.5-valent vanadium electrolyte of the present invention, the vanadium-containing material includes one or more of sodium vanadate, potassium vanadate, crude vanadium, red vanadium, and vanadium leachate.

[0024] In a preferred embodiment of the preparation method of a solid 3.5-valent vanadium electrolyte of the present invention, the acid solution includes one or more of hydrochloric acid and sulfuric acid.

[0025] As a preferred embodiment of the preparation method of a solid 3.5 vanadium electrolyte of the present invention, the reducing agent includes one or more of sulfite, sulfur dioxide, sodium sulfide, sucrose, glucose, fructose, and formic acid.

[0026] As a preferred embodiment of the preparation method of a solid 3.5-valent vanadium electrolyte of the present invention, the drying temperature is 40~150℃ and the drying environment is vacuum.

[0027] As a preferred embodiment of the preparation method of solid 3.5 vanadium electrolyte of the present invention, the reagents used to adjust the pH value of the tetravalent vanadium solution obtained in step 1) include one or more of NaOH, KOH, Na2CO3, NaHCO3, K2CO3, and KHCO3 at a concentration of 50-500 g / L.

[0028] As another aspect of the present invention, a solid 3.5-valent vanadium electrolyte prepared by any of the methods described above is also provided.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. Precise valence state control and high product consistency: This invention prepares high-purity VO2 (+4 valence) and V3O5 (+3.33 valence) with clearly defined valence states separately, and then mixes them in a precise molar ratio to generate V4O7 (+3.5 valence) through solid-phase reaction. This method precisely controls the valence state of the final product. The resulting solid electrolyte can be directly obtained as a 3.5 valence electrolyte after acid dissolution without any subsequent valence state adjustment.

[0031] 2. Wide adaptability of raw materials and low production cost: This invention starts with various types of vanadium-containing materials such as crude vanadium, vanadium oxide, and vanadates, and directly obtains VO(OH)2 through acid leaching reduction and hydrolysis precipitation. This method does not discriminate against the purity of raw materials and can significantly reduce raw material costs. It is especially suitable for processing low-grade or inexpensive vanadium-containing resources.

[0032] 3. Clean and environmentally friendly, with no high-salt ammonia nitrogen wastewater or waste gas generated. No ammonium salts are introduced in the entire process of this invention. After separating VO(OH)2, the mother liquor can be recycled. The calcination process is carried out in an argon or reducing atmosphere, with no toxic or harmful waste gas. The final product is solid, with no vanadium-containing waste liquid generated.

[0033] 4. The product is solid, significantly reducing transportation and storage costs. This invention directly prepares solid V4O7, which is almost water-free and has a high vanadium mass fraction. During transportation, the effective component (vanadium) per unit mass is several times that of the liquid electrolyte, which can greatly reduce transportation weight and volume, thereby lowering transportation costs.

[0034] 5. Solid V4O7 has a fast acid dissolution rate. The V4O7 powder prepared by heat treatment in this invention has a fine particle size and excellent solubility. It can be completely dissolved in sulfuric acid solution within 60 to 90 seconds, which significantly improves the preparation efficiency of vanadium 3,5-valent electrolyte. Attached Figure Description

[0035] Figure 1 The preparation process flow chart of the present invention. Detailed Implementation

[0036] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Reference Figure 1 As a specific embodiment of the present invention, a method for preparing a solid vanadium 3.5-valent electrolyte is provided, comprising the following steps:

[0038] 1) Mix the vanadium-containing material with acid solution, adjust the pH of the mixture to ≤4, add a reducing agent at 1 to 5 times the theoretical required reaction amount, and stir the reaction at 200 to 400 rpm at 40 to 99°C for 0.5 to 5 hours to obtain a tetravalent vanadium solution.

[0039] In this step, the vanadium-containing material includes one or more of sodium vanadate, potassium vanadate, crude vanadium, red vanadium, and vanadium leaching solution. Its purity is not particularly limited, which can significantly reduce the cost of raw materials and is especially suitable for processing low-grade or inexpensive vanadium-containing resources.

[0040] In this step, the acid solution includes one or more of hydrochloric acid and sulfuric acid. There are no particular limitations on its concentration and amount added, as long as the pH value of the mixture after addition is ≤4. Preferably, the pH value can be controlled within the range of 0, 1, 2, 3, 4 and any two of them.

[0041] In this step, the reducing agent includes one or more of the following: sulfite, sulfur dioxide, sodium sulfide, sucrose, glucose, fructose, and formic acid.

[0042] In this step, the stirring speed and reduction temperature are particularly critical. This is because excessively low stirring speed and / or reduction temperature during the reduction reaction lead to poor reaction kinetics, preventing complete reduction of pentavalent vanadium to tetravalent vanadium. This results in a reduction in the mass of the obtained VO(OH)₂ powder. The unreacted pentavalent vanadium cannot precipitate under alkaline conditions but instead remains trapped within VO(OH)₂. This trapping remains in the VO₂ powder even after calcination in an argon atmosphere, ultimately leading to a higher valence state in the solid vanadium electrolyte after subsequent mixing and heat treatment. Therefore, the stirring speed in this step is preferably within the range of 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, or any two of these values; the reduction temperature is preferably within the range of 40℃, 50℃, 60℃, 70℃, 99℃, or any two of these values.

[0043] 2) Adjust the pH of the tetravalent vanadium solution obtained in step 1) to 6-12 using one or more of the following reagents: NaOH, KOH, Na2CO3, NaHCO3, K2CO3, and KHCO3 at a concentration of 50-500 g / L. Stir the reaction at 200-400 rpm for 0.5-2 h at 20-50 °C. After filtration and drying under vacuum at 40-150 °C, solid VO(OH)2 is obtained.

[0044] 3) VO(OH)2 solid was calcined in an argon atmosphere at 200~800℃ for 4~8h to obtain VO2 powder;

[0045] 4) Calcine solid VO(OH)2 in a reducing atmosphere at 400-600℃ for 4-6 hours to obtain V3O5 powder; or mix solid VO(OH)2 with a two-stage reducing agent and press it into blocks, then calcine it in an argon atmosphere at 400-800℃ for 4-8 hours to obtain V3O5 powder, wherein the amount of the two-stage reducing agent added is 1-2 times the theoretical reaction amount required for the reaction with solid VO(OH)2;

[0046] In this step, the reducing atmosphere includes one or more of H2, NH3, and CO.

[0047] In this step, the reducing agent includes one or more of oxalic acid and citric acid.

[0048] In this step, the calcination temperature is particularly important because if the temperature is too low, the reduction reaction will be insufficient, and the resulting low-valent vanadium oxide powder will be a mixture of VO2 and V3O5 with an average valence state higher than +3.3. This will result in the solid low-valent vanadium electrolyte obtained after mixed heat treatment having a valence state higher than +3.5. If the temperature is too high, over-reduction will occur, and the resulting low-valent vanadium oxide powder will be mostly V2O3 with a valence state of +3, with an average valence state lower than +3.3. This will result in the solid low-valent vanadium electrolyte obtained after mixed heat treatment having a valence state lower than +3.5. Since V2O3 is not easily soluble in sulfuric acid solution, the dissolution rate of the solid low-valent vanadium electrolyte will be significantly slower. Therefore, the calcination temperature under the reducing atmosphere in this step is preferably within the range of 400℃, 420℃, 450℃, 480℃, 500℃, 550℃, 600℃ and any two of these values; the calcination temperature under the reduction reaction involving the reducing agent is preferably within the range of 400℃, 500℃, 600℃, 650℃, 700℃, 800℃ and any two of these values.

[0049] In this step, the calcination time is particularly important. If the calcination time is too short, the reduction of VO(OH)₂ will be insufficient, resulting in a mixture of VO₂ and V₃O₅ low-valent oxide powder with an average valence higher than +3.3. This leads to a valence higher than +3.5 for the solid low-valent vanadium electrolyte obtained after heat treatment. Conversely, if the calcination time is too long, VO(OH)₂ will be over-reduced, resulting in mostly +3 valence V₂O₃ low-valent oxide powder with an average valence lower than +3.3. This leads to a valence lower than +3.5 for the solid low-valent vanadium electrolyte obtained after heat treatment. Since V₂O₃ is not easily soluble in sulfuric acid solution, the dissolution rate of the solid low-valent vanadium electrolyte will be significantly slowed. Therefore, the preferred calcination temperature in this step under a reducing atmosphere is within the range of 4h, 4.5h, 5h, 5.5h, 6h, or any two of these values. Similarly, the preferred calcination temperature under a reduction reaction involving a reducing agent is within the range of 4h, 5h, 6h, 7h, 8h, or any two of these values.

[0050] In this step, the amount of the secondary reducing agent added is particularly important. Insufficient addition leads to incomplete reduction, resulting in a low-valent vanadium oxide powder that is a mixture of VO2 and V3O5 with an average valence higher than +3.3. This results in the solid low-valent vanadium electrolyte obtained after heat treatment having a valence higher than +3.5. Excessive addition, on the other hand, leads to over-reduction, resulting in a low-valent vanadium oxide powder that is mostly V2O3 with a valence of +3, with an average valence lower than +3.3. This results in the solid low-valent vanadium electrolyte obtained after heat treatment having a valence lower than +3.5. Since V2O3 is not easily soluble in sulfuric acid solution, the dissolution rate of the solid low-valent vanadium electrolyte is significantly slowed down. Therefore, the amount of the secondary reducing agent added in this step is preferably within the range of 1, 1.2, 1.4, 1.5, 1.6, 1.8, 2.0 times the theoretical reaction amount with solid VO(OH)2, or any two of these values.

[0051] 5) Mix VO2 powder and V3O5 powder in a molar ratio of 1:1 and press them into blocks under a pressure of 50~200 MPa. Then calcine them in an inert atmosphere at 400~800℃ for 4~10 hours to obtain solid 3.5 vanadium electrolyte V4O7.

[0052] In this step, the purpose of pressing and calcining is to obtain solid vanadium electrolyte with 3.5 valence. Compared with the case without pressing and calcining, the solid low-valence vanadium electrolyte dissolves much faster because the product does not contain V3O5, which dissolves slowly in sulfuric acid solution.

[0053] Example 1

[0054] A method for preparing a solid vanadium 3.5 valence electrolyte includes the following steps:

[0055] 1) Dissolve 100g of sodium metavanadate in 300ml of water, add concentrated sulfuric acid to adjust the pH to 0, add 258.3g (5 times the theoretical reaction amount) of sodium sulfite, and stir the reaction at 400rpm at 99℃ for 0.5h to obtain a tetravalent vanadium solution with a vanadium content of 140g / L.

[0056] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 6 using 50 g / L NaOH. The mixture was stirred at 400 rpm for 0.5 h at 50 °C. After filtration and vacuum drying at 150 °C, 80.3 g of VO(OH)2 solid was obtained.

[0057] 3) 30g of the VO(OH)2 solid obtained in step 2) was calcined at 800℃ for 4h under an argon atmosphere to obtain 24.6g of VO2 powder;

[0058] 4) Take another 30g of the VO(OH)2 solid obtained in step 2) and calcine it at 600℃ for 4h under a hydrogen atmosphere to obtain 23g of V3O5 powder;

[0059] 5) Mix 8.2g of VO2 powder and 23g of V3O5 powder and press them into blocks under a pressure of 200MPa. Then calcine them at 800℃ for 4h under an argon atmosphere to obtain 31.2g of solid 3.5 valence vanadium electrolyte V4O7.

[0060] 31.2 g of V4O7 was dissolved in sulfuric acid solution to obtain 246 ml of 1.6 M vanadium 3.5 electrolyte, with a dissolution time of 72 s.

[0061] Example 2

[0062] A method for preparing a solid vanadium 3.5 valence electrolyte includes the following steps:

[0063] 1) Dissolve 100g of potassium orthovanadate in 300ml of water, add concentrated sulfuric acid to adjust the pH to 4, add 3g (1 times the theoretical reaction amount) of sucrose, stir at 200rpm for 5h at 40℃ to obtain a tetravalent vanadium solution with a vanadium content of 70g / L.

[0064] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 12 using 100 g / L K2CO3. The mixture was stirred at 400 rpm for 2 h at 40 °C. After filtration and vacuum drying at 40 °C, 42.5 g of VO(OH)2 solid was obtained.

[0065] 3) 10g of the VO(OH)2 solid obtained in step 2) was calcined at 200℃ for 8h under an argon atmosphere to obtain 8.2g of VO2 powder;

[0066] 4) Take another 20g of VO(OH)2 solid obtained in step 2) and mix it with 11.8g of oxalic acid (twice the theoretical reaction amount). After pressing it into a block under a pressure of 200Mpa, calcine it at 400℃ for 8h under an argon atmosphere to obtain 15.3g of V3O5 powder.

[0067] 5) Mix 5.4g of VO2 powder and 15.3g of V3O5 powder and press them into blocks under a pressure of 50MPa. Then calcine them at 400℃ for 10h under an argon atmosphere to obtain 20.7g of solid 3.5 valence vanadium electrolyte V4O7.

[0068] 20.7 g of V4O7 was dissolved in sulfuric acid solution to obtain 165 ml of 1.6 M vanadium 3.5 electrolyte, with a dissolution time of 66 s.

[0069] Example 3

[0070] A method for preparing a solid vanadium 3.5 valence electrolyte includes the following steps:

[0071] 1) Place 100g of vanadium pentoxide in 280ml of water, add concentrated sulfuric acid to adjust the pH to 1, add 21.4g (twice the theoretical reaction amount) of sodium sulfide, stir at 300rpm at 60℃ for 1.5h to obtain a tetravalent vanadium solution with a vanadium content of 100g / L.

[0072] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 8 using 200 g / L NaHCO3. The mixture was stirred at 300 rpm for 1 h at 30 °C. After filtration and vacuum drying at 100 °C, 106.4 g of VO(OH)2 solid was obtained.

[0073] 3) 20g of the VO(OH)2 solid obtained in step 2) was calcined at 600℃ for 5h under an argon atmosphere to obtain 16.4g of VO2 powder;

[0074] 4) Take another 60g of the VO(OH)2 solid obtained in step 2) and calcine it at 500℃ for 4h in an NH3 atmosphere to obtain 46.1g of V3O5 powder;

[0075] 5) Mix 16.4g of VO2 powder and 46.1g of V3O5 powder and press them into blocks under 100MPa pressure. Then calcine them at 400℃ for 6h under argon atmosphere to obtain 62.5g of solid 3.5 valence vanadium electrolyte V4O7.

[0076] 62.5g of V4O7 was dissolved in sulfuric acid solution to obtain 494ml of 1.6M vanadium 3.5 electrolyte, with a dissolution time of 89s.

[0077] Example 4

[0078] A method for preparing a solid vanadium 3.5 valence electrolyte includes the following steps:

[0079] 1) Add concentrated hydrochloric acid to 300ml of vanadium leaching solution with a vanadium content of 30g / L, adjust the pH to 3, add 3.9g of glucose (3 times the theoretical reaction amount), and stir at 250rpm for 3h at 50℃ to obtain a tetravalent vanadium solution with a vanadium content of 30g / L.

[0080] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 10 using 300 g / L Na2CO3. The mixture was stirred at 250 rpm for 1.5 h at 50 °C. After filtration and vacuum drying at 80 °C, 17.2 g of VO(OH)2 solid was obtained.

[0081] 3) 4g of the VO(OH)2 solid obtained in step 2) was calcined at 400℃ for 6h under an argon atmosphere to obtain 3.2g of VO2 powder;

[0082] 4) Take another 12g of VO(OH)2 solid obtained in step 2) and mix it with 4.2g of citric acid (1 times the theoretical reaction amount). After pressing it into a block under a pressure of 50Mpa, calcine it at 700℃ for 4h under an argon atmosphere to obtain 9.2g of V3O5 powder.

[0083] 5) Mix 3.2g VO2 powder and 9.2g V3O5 powder and press them into blocks under a pressure of 150 MPa. Then calcine them at 600℃ for 4 hours under an argon atmosphere to obtain 12.4g solid 3.5 valence vanadium electrolyte V4O7.

[0084] 12.4 g of V4O7 was dissolved in sulfuric acid solution to obtain 98 ml of 1.6 M vanadium 3.5 electrolyte, with a dissolution time of 61 s.

[0085] Example 5

[0086] A method for preparing a solid vanadium 3.5 valence electrolyte includes the following steps:

[0087] 1) Dissolve 100g of sodium orthovanadate in 550ml of water, add concentrated sulfuric acid to adjust the pH to 2, add 102.7g (3 times the theoretical reaction amount) of sodium sulfite, stir at 350rpm for 3h at 70℃ to obtain a tetravalent vanadium solution with a vanadium content of 50g / L.

[0088] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 9 using 400 g / L Na2CO3. The mixture was stirred at 350 rpm for 1 h at 30 °C. After filtration and vacuum drying at 60 °C, 52.6 g of VO(OH)2 solid was obtained.

[0089] 3) 10g of the VO(OH)2 solid obtained in step 2) was calcined at 500℃ for 5h under an argon atmosphere to obtain 8.2g of VO2 powder;

[0090] 4) Take another 30g of the VO(OH)2 solid obtained in step 2) and calcine it at 450℃ for 5h under CO atmosphere to obtain 23g of V3O5 powder;

[0091] 5) Mix 8.2g of VO2 powder and 23g of V3O5 powder and press them into blocks under a pressure of 120MPa. Then calcine them at 500℃ for 5h under an argon atmosphere to obtain 31.2g of solid 3.5 valence vanadium electrolyte V4O7.

[0092] 31.2 g of V4O7 was dissolved in sulfuric acid solution to obtain 246 ml of 1.6 M vanadium 3.5 electrolyte, with a dissolution time of 79 s.

[0093] Example 6

[0094] A method for preparing a solid vanadium 3.5 valence electrolyte includes the following steps:

[0095] 1) Dissolve 100g of potassium metavanadate in 300ml of water, add concentrated hydrochloric acid to adjust the pH to 3, add 21.7g (4 times the theoretical reaction amount) of fructose, and stir at 350rpm for 2h at 70℃ to obtain a tetravalent vanadium solution with a vanadium content of 120g / L.

[0096] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 11 using 500 g / L KOH. The mixture was stirred at 350 rpm for 0.5 h at 20 °C. After filtration and vacuum drying at 80 °C, 70.2 g of VO(OH)2 solid was obtained.

[0097] 3) 15g of the VO(OH)2 solid obtained in step 2) was calcined at 700℃ for 6h under an argon atmosphere to obtain 12.3g of VO2 powder;

[0098] 4) Take another 45g of VO(OH)2 solid obtained in step 2) and mix it with 20g of oxalic acid (1.5 times the theoretical reaction amount). After pressing it into a block under a pressure of 100Mpa, calcine it at 500℃ for 5h under an argon atmosphere to obtain 34.6g of V3O5 powder.

[0099] 5) Mix 12.3g of VO2 powder and 34.6g of V3O5 powder and press them into blocks under a pressure of 200 MPa. Then calcine them at 500℃ for 7 hours under an argon atmosphere to obtain 46.9g of solid 3.5 valence vanadium electrolyte V4O7.

[0100] 46.9 g of V4O7 was dissolved in sulfuric acid solution to obtain 370 ml of 1.6 M vanadium 3.5 electrolyte, with a dissolution time of 84 s.

[0101] Comparative Example 1

[0102] A method for preparing a vanadium electrolyte includes the following steps:

[0103] 1) Dissolve 100g of sodium metavanadate in 300ml of water, add concentrated sulfuric acid to adjust the pH to 0, add 258.3g (5 times the theoretical reaction amount) of sodium sulfite, and stir the reaction at 400rpm at 99℃ for 0.5h to obtain a tetravalent vanadium solution with a vanadium content of 140g / L.

[0104] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 6 using 50 g / L NaOH. The mixture was stirred at 400 rpm for 0.5 h at 50 °C. After filtration and vacuum drying at 150 °C, 80.3 g of VO(OH)2 solid was obtained.

[0105] 3) 30g of the VO(OH)2 solid obtained in step 2) was calcined at 800℃ for 4h under an argon atmosphere to obtain 24.6g of VO2 powder;

[0106] 4) Take another 30g of the VO(OH)2 solid obtained in step 2) and calcine it at 1000℃ for 4h under a hydrogen atmosphere to obtain 22.3g of low-valent vanadium oxide powder;

[0107] 5) Mix 8.2g of VO2 powder and 22.3g of low-valent vanadium oxide powder, press them into blocks under a pressure of 200 MPa, and then calcine them at 800℃ for 4 hours under an argon atmosphere to obtain 30.5g of solid low-valent vanadium electrolyte.

[0108] 30.5g of solid low-valent vanadium electrolyte was dissolved in sulfuric acid solution to obtain 246ml of 1.6M vanadium 3.3 electrolyte. The dissolution time was 36min.

[0109] Compared with Example 1, in this comparative example, the calcination temperature of VO(OH)2 powder in a hydrogen atmosphere was too high, resulting in excessive reduction of VO(OH)2. The resulting low-valence vanadium oxide powder was mostly V2O3 with a +3 valence, and the average valence was lower than +3.3. This led to the solid low-valence vanadium electrolyte obtained after mixed heat treatment having a valence lower than +3.5. Furthermore, due to the poor solubility of V2O3 in sulfuric acid solution, the dissolution rate of the solid low-valence vanadium electrolyte was significantly slower.

[0110] Comparative Example 2

[0111] A method for preparing a vanadium electrolyte includes the following steps:

[0112] 1) Dissolve 100g of potassium orthovanadate in 300ml of water, add concentrated sulfuric acid to adjust the pH to 4, add 3g (1 times the theoretical reaction amount) of sucrose, stir at 200rpm for 5h at 40℃ to obtain a tetravalent vanadium solution with a vanadium content of 70g / L.

[0113] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 12 using 100 g / L K2CO3. The mixture was stirred at 400 rpm for 2 h at 40 °C. After filtration and vacuum drying at 40 °C, 42.5 g of VO(OH)2 solid was obtained.

[0114] 3) 10g of the VO(OH)2 solid obtained in step 2) was calcined at 200℃ for 8h under an argon atmosphere to obtain 8.2g of VO2 powder;

[0115] 4) Take another 20g of VO(OH)2 solid obtained in step 2) and mix it with 17.7g of oxalic acid (3 times the theoretical reaction amount). After pressing it into a block under a pressure of 200Mpa, calcine it at 400℃ for 8h under an argon atmosphere to obtain 15g of low-valent vanadium oxide powder.

[0116] 5) Mix 5.4g of VO2 powder and 15g of low-valent vanadium oxide powder, press them into blocks under a pressure of 50 MPa, and then calcine them at 400℃ for 10 hours under an argon atmosphere to obtain 20.4g of solid low-valent vanadium electrolyte.

[0117] 20.4 g of solid low-valent vanadium electrolyte was dissolved in sulfuric acid solution to obtain 165 ml of 1.6 M vanadium electrolyte with a 3.27 valent vanadium content. The dissolution time was 25 min.

[0118] Compared with Example 2, in this comparative example, due to the excessive addition of oxalic acid, VO(OH)2 was over-reduced, and most of the resulting low-valent vanadium oxide powder was V2O3 with a +3 valence, with an average valence lower than +3.3. This resulted in the solid low-valent vanadium electrolyte obtained after mixed heat treatment having a valence lower than +3.5. Furthermore, due to the poor solubility of V2O3 in sulfuric acid solution, the dissolution rate of the solid low-valent vanadium electrolyte was significantly slower.

[0119] Comparative Example 3

[0120] A method for preparing a vanadium electrolyte includes the following steps:

[0121] 1) Place 100g of vanadium pentoxide in 280ml of water, add concentrated sulfuric acid to adjust the pH to 1, add 21.4g (twice the theoretical reaction amount) of sodium sulfide, stir at 300rpm at 60℃ for 1.5h to obtain a tetravalent vanadium solution with a vanadium content of 100g / L.

[0122] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 8 using 200 g / L NaHCO3. The mixture was stirred at 300 rpm for 1 h at 30 °C. After filtration and vacuum drying at 100 °C, 106.4 g of VO(OH)2 solid was obtained.

[0123] 3) 20g of the VO(OH)2 solid obtained in step 2) was calcined at 600℃ for 5h under an argon atmosphere to obtain 16.4g of VO2 powder;

[0124] 4) Take another 60g of the VO(OH)2 solid obtained in step 2) and calcine it at 500℃ for 12h in an NH3 atmosphere to obtain 44.6g of low-valent vanadium oxide powder;

[0125] 5) Mix 16.4g of VO2 powder and 44.6g of low-valent vanadium oxide powder and press them into blocks under a pressure of 100 MPa. Then calcine them at 400℃ for 6 hours under an argon atmosphere to obtain 61g of solid low-valent vanadium electrolyte.

[0126] 61g of solid low-valent vanadium electrolyte was dissolved in sulfuric acid solution to obtain 494ml of 1.6M vanadium electrolyte with a valence of 3.26 valence. The dissolution time was 67min.

[0127] Compared with Example 3, in this comparative example, due to the excessive calcination time of VO(OH)2 powder in NH3 atmosphere, VO(OH)2 was over-reduced, and most of the resulting low-valence vanadium oxide powder had a valence state of +3 V2O3, with an average valence state lower than +3.3. This resulted in the solid low-valence vanadium electrolyte obtained after mixed heat treatment having a valence state lower than +3.5. Furthermore, due to the poor solubility of V2O3 in sulfuric acid solution, the dissolution rate of the solid low-valence vanadium electrolyte was significantly slower.

[0128] Comparative Example 4

[0129] A method for preparing a vanadium electrolyte includes the following steps:

[0130] 1) Dissolve 100g of sodium metavanadate in 300ml of water, add concentrated sulfuric acid to adjust the pH to 0, add 258.3g (5 times the theoretical reaction amount) of sodium sulfite, and stir the reaction at 400rpm at 99℃ for 0.5h to obtain a tetravalent vanadium solution with a vanadium content of 140g / L.

[0131] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 6 using 50 g / L NaOH. The mixture was stirred at 400 rpm for 0.5 h at 50 °C. After filtration and vacuum drying at 150 °C, 80.3 g of VO(OH)2 solid was obtained.

[0132] 3) 30g of the VO(OH)2 solid obtained in step 2) was calcined at 800℃ for 4h under an argon atmosphere to obtain 24.6g of VO2 powder;

[0133] 4) Take another 30g of the VO(OH)2 solid obtained in step 2) and calcine it at 200℃ for 4h under a hydrogen atmosphere to obtain 24.3g of low-valent vanadium oxide powder;

[0134] 5) Mix 8.2g of VO2 powder and 24.3g of low-valent vanadium oxide powder and press them into blocks under a pressure of 200 MPa. Then calcine them at 800℃ for 4 hours under an argon atmosphere to obtain 32.5g of solid low-valent vanadium electrolyte.

[0135] 32.5g of solid low-valent vanadium electrolyte was dissolved in sulfuric acid solution to obtain 246ml of 1.6M vanadium 3.8 electrolyte, with a dissolution time of 69s.

[0136] Compared with Example 1, in this comparative example, because the calcination temperature of VO(OH)2 powder in a hydrogen atmosphere was too low, VO(OH)2 was not completely reduced to V3O5, and the average valence state of the resulting low-valence vanadium oxide powder was higher than +3.3, resulting in the valence state of the solid low-valence vanadium electrolyte obtained after mixed heat treatment being higher than +3.5.

[0137] Comparative Example 5

[0138] A method for preparing a vanadium electrolyte includes the following steps:

[0139] 1) Dissolve 100g of sodium orthovanadate in 550ml of water, add concentrated sulfuric acid to adjust the pH to 2, add 102.7g (3 times the theoretical reaction amount) of sodium sulfite, stir at 350rpm for 3h at 70℃ to obtain a tetravalent vanadium solution with a vanadium content of 50g / L.

[0140] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 9 using 400 g / L Na2CO3. The mixture was stirred at 350 rpm for 1 h at 30 °C. After filtration and vacuum drying at 60 °C, 52.6 g of VO(OH)2 solid was obtained.

[0141] 3) 10g of the VO(OH)2 solid obtained in step 2) was calcined at 500℃ for 5h under an argon atmosphere to obtain 8.2g of VO2 powder;

[0142] 4) Take another 30g of the VO(OH)2 solid obtained in step 2) and calcine it at 450℃ for 5h under CO atmosphere to obtain 23g of V3O5 powder;

[0143] 5) Mix 8.2g VO2 powder and 23g V3O5 powder and dissolve them in sulfuric acid solution to obtain 246ml 1.6M vanadium 3.5 electrolyte. The dissolution time is 33min.

[0144] Compared with Example 5, this comparative example did not involve mixing and heat-treating VO2 and V3O5 to synthesize V4O7. Instead, the mixture was directly dissolved in sulfuric acid. Since V3O5 dissolves slowly in sulfuric acid solution, the dissolution rate of the solid low-valence vanadium electrolyte was significantly slower.

[0145] Comparative Example 6

[0146] A method for preparing a vanadium electrolyte includes the following steps:

[0147] 1) Place 100g of vanadium pentoxide in 280ml of water, add concentrated sulfuric acid to adjust the pH to 1, add 21.4g (twice the theoretical reaction amount) of sodium sulfide, stir at 300rpm at 60℃ for 1.5h to obtain a tetravalent vanadium solution with a vanadium content of 100g / L.

[0148] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 8 using 200 g / L NaHCO3. The mixture was stirred at 300 rpm for 1 h at 30 °C. After filtration and vacuum drying at 100 °C, 106.4 g of VO(OH)2 solid was obtained.

[0149] 3) 20g of the VO(OH)2 solid obtained in step 2) was calcined at 600℃ for 5h under an argon atmosphere to obtain 16.4g of VO2 powder;

[0150] 4) Take another 60g of the VO(OH)2 solid obtained in step 2) and calcine it at 500℃ for 2h under NH3 atmosphere to obtain 48.9g of low-valent vanadium oxide powder;

[0151] 5) Mix 16.4g of VO2 powder and 48.9g of low-valent vanadium oxide powder and press them into blocks under 100MPa pressure. Then calcine them at 400℃ for 6h under argon atmosphere to obtain 65.3g of solid low-valent vanadium electrolyte.

[0152] 65.3 g of solid low-valent vanadium electrolyte was dissolved in sulfuric acid solution to obtain 494 ml of 1.6 M vanadium electrolyte with a valence of 3.86 valence. The dissolution time was 73 s.

[0153] Compared with Example 3, in this comparative example, because the calcination time of VO(OH)2 powder in NH3 atmosphere was too short, VO(OH)2 was not completely reduced to V3O5, and the average valence state of the resulting low-valence vanadium oxide powder was higher than +3.3, resulting in the valence state of the solid low-valence vanadium electrolyte obtained after mixed heat treatment being higher than +3.5.

[0154] Comparative Example 7

[0155] A method for preparing a vanadium electrolyte includes the following steps:

[0156] 1) Dissolve 100g of sodium orthovanadate in 550ml of water, add concentrated sulfuric acid to adjust the pH to 2, add 102.7g (3 times the theoretical reaction amount) of sodium sulfite, stir at 350rpm for 3h at 70℃ to obtain a tetravalent vanadium solution with a vanadium content of 50g / L.

[0157] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 9 using 400 g / L Na2CO3. The mixture was stirred at 350 rpm for 1 h at 30 °C. After filtration and vacuum drying at 60 °C, 52.6 g of VO(OH)2 solid was obtained.

[0158] 3) 10g of the VO(OH)2 solid obtained in step 2) was calcined at 500℃ for 5h under an argon atmosphere to obtain 8.2g of VO2 powder;

[0159] 4) Take another 30g of the VO(OH)2 solid obtained in step 2) and calcine it at 450℃ for 5h under CO atmosphere to obtain 23g of V3O5 powder;

[0160] 5) Mix 8.2g of VO2 powder and 23g of V3O5 powder and press them into blocks under a pressure of 120MPa. Then calcine them at 200℃ for 5h under an argon atmosphere to obtain 31.2g of solid low-valence vanadium electrolyte.

[0161] 31.2 g of solid low-valent vanadium electrolyte was dissolved in sulfuric acid solution to obtain 246 ml of 1.6 M vanadium 3.5 electrolyte. The dissolution time was 41 min.

[0162] Compared with Example 5, the temperature of the heat treatment in this comparative example was too low, which resulted in the incomplete synthesis of V4O7 from VO2 and V3O5. Since V3O5 dissolves slowly in sulfuric acid solution, the dissolution rate of the solid low-valence vanadium electrolyte was significantly slowed down.

[0163] Comparative Example 8

[0164] A method for preparing a vanadium electrolyte includes the following steps:

[0165] 1) Dissolve 100g of sodium orthovanadate in 550ml of water, add concentrated sulfuric acid to adjust the pH to 2, add 102.7g (3 times the theoretical reaction amount) of sodium sulfite, stir at 350rpm for 3h at 70℃ to obtain a tetravalent vanadium solution with a vanadium content of 50g / L.

[0166] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 9 using 400 g / L Na2CO3. The mixture was stirred at 350 rpm for 1 h at 30 °C. After filtration and vacuum drying at 60 °C, 52.6 g of VO(OH)2 solid was obtained.

[0167] 3) 10g of the VO(OH)2 solid obtained in step 2) was calcined at 500℃ for 5h under an argon atmosphere to obtain 8.2g of VO2 powder;

[0168] 4) Take another 30g of the VO(OH)2 solid obtained in step 2) and calcine it at 450℃ for 5h under CO atmosphere to obtain 23g of V3O5 powder;

[0169] 5) Mix 8.2g of VO2 powder and 23g of V3O5 powder and press them into blocks under a pressure of 120MPa. Then calcine them at 500℃ for 1h under an argon atmosphere to obtain 31.2g of solid low-valence vanadium electrolyte.

[0170] 31.2 g of solid low-valent vanadium electrolyte was dissolved in sulfuric acid solution to obtain 246 ml of 1.6 M vanadium trivalent electrolyte. The dissolution time was 35 min.

[0171] Compared with Example 5, the heat treatment time of this comparative example was too short, resulting in the incomplete synthesis of V4O7 from VO2 and V3O5. Since V3O5 dissolves slowly in sulfuric acid solution, the dissolution rate of the solid low-valence vanadium electrolyte was significantly slowed down.

[0172] Comparative Example 9

[0173] A method for preparing a vanadium electrolyte includes the following steps:

[0174] 1) Dissolve 100g of sodium orthovanadate in 550ml of water, add concentrated sulfuric acid to adjust the pH to 2, add 102.7g (3 times the theoretical reaction amount) of sodium sulfite, stir at 10rpm for 3h at 70℃ to obtain a tetravalent vanadium solution with a vanadium content of 50g / L.

[0175] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 9 using 400 g / L Na2CO3. The mixture was stirred at 350 rpm for 1 h at 30 °C. After filtration and vacuum drying at 60 °C, 52.6 g of VO(OH)2 solid was obtained.

[0176] 3) 10g of the VO(OH)2 solid obtained in step 2) was calcined at 500℃ for 5h under an argon atmosphere to obtain 8.2g of VO2 powder;

[0177] 4) Take another 30g of the VO(OH)2 solid obtained in step 2) and calcine it at 450℃ for 5h under CO atmosphere to obtain 23g of V3O5 powder;

[0178] 5) Mix 8.2g of VO2 powder and 23g of V3O5 powder and press them into blocks under a pressure of 120MPa. Then calcine them at 500℃ for 5h under an argon atmosphere to obtain 31.2g of solid low-valence vanadium electrolyte.

[0179] 31.2 g of solid low-valent vanadium electrolyte was dissolved in sulfuric acid solution to obtain 246 ml of 1.6 M vanadium electrolyte with a valence of 3.55 valence. The dissolution time was 71 s.

[0180] Compared to Example 5, this comparative example suffered from poor reaction kinetics due to an excessively low stirring rate during the reduction reaction. Consequently, pentavalent vanadium was not completely reduced to tetravalent vanadium, resulting in a reduced mass of the obtained VO(OH)₂ powder. The unreacted pentavalent vanadium could not precipitate under alkaline conditions but instead remained trapped within the VO(OH)₂. This trapping remained in the VO₂ powder after calcination in an argon atmosphere. Subsequent mixing and heat treatment resulted in a final solid low-valent vanadium electrolyte with an average valence state higher than +3.5.

[0181] Comparative Example 10

[0182] A method for preparing a vanadium electrolyte includes the following steps:

[0183] 1) Dissolve 100g of sodium orthovanadate in 550ml of water, add concentrated sulfuric acid to adjust the pH to 2, add 102.7g (3 times the theoretical reaction amount) of sodium sulfite, stir at 350rpm for 3h at 20℃ to obtain a tetravalent vanadium solution with a vanadium content of 50g / L.

[0184] 2) The pH of the tetravalent vanadium solution obtained in step 1) was adjusted to 9 using 400 g / L Na2CO3. The mixture was stirred at 350 rpm for 1 h at 30 °C. After filtration and vacuum drying at 60 °C, 52.6 g of VO(OH)2 solid was obtained.

[0185] 3) 10g of the VO(OH)2 solid obtained in step 2) was calcined at 500℃ for 5h under an argon atmosphere to obtain 8.2g of VO2 powder;

[0186] 4) Take another 30g of the VO(OH)2 solid obtained in step 2) and calcine it at 450℃ for 5h under CO atmosphere to obtain 23g of V3O5 powder;

[0187] 5) Mix 8.2g of VO2 powder and 23g of V3O5 powder and press them into blocks under a pressure of 120MPa. Then calcine them at 500℃ for 5h under an argon atmosphere to obtain 31.2g of solid low-valence vanadium electrolyte.

[0188] 31.2 g of solid low-valent vanadium electrolyte was dissolved in sulfuric acid solution to obtain 246 ml of 1.6 M vanadium 3.6 electrolyte, and the dissolution time was 64 s.

[0189] Compared to Example 5, this comparative example had poorer thermodynamic and kinetic conditions due to the excessively low temperature during the reduction reaction, resulting in incomplete reduction of pentavalent vanadium to tetravalent vanadium and a decrease in the mass of the obtained VO(OH)2 powder. The unreacted pentavalent vanadium could not precipitate under alkaline conditions but instead remained trapped within VO(OH)2. This trapping remained in the VO2 powder after calcination in an argon atmosphere. Subsequent mixing and heat treatment resulted in a final solid low-valent vanadium electrolyte with an average valence state higher than +3.5.

[0190] It should be noted that, based on the above embodiments of the present invention, those skilled in the art can fully realize the scope of the independent claims and dependent claims of the present invention, and the implementation process and methods are the same as those in the above embodiments; and the parts of the present invention not described in detail belong to the well-known technology in the art. However, the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a solid-state vanadium 3,5-valent electrolyte, characterized in that, Includes the following steps: VO2 powder and V3O5 powder are mixed in a molar ratio of 1:1 and pressed into blocks. Then, they are calcined at 400~800℃ for 4~10h under an inert atmosphere to obtain solid 3.5 vanadium electrolyte V4O7. The VO2 powder is prepared through the following steps: VO(OH)2 solid was calcined at 200-800℃ for 4-8 hours under an inert atmosphere to obtain VO2 powder; The V3O5 powder was prepared by the following steps: VO(OH)2 solid is calcined at 400-600℃ for 4-6 hours in a reducing atmosphere, or VO(OH)2 solid is mixed with a two-stage reducing agent and pressed into blocks, then calcined at 400-800℃ for 4-8 hours in an inert atmosphere to obtain V3O5 powder. The amount of the two-stage reducing agent added is 1-2 times the theoretical reaction amount required for the reaction with VO(OH)2 solid.

2. A method for preparing a solid-state vanadium 3,5-valent electrolyte as described in claim 1, characterized in that, The reducing atmosphere includes one or more of H2, NH3, and CO, and the inert atmosphere includes argon.

3. A method for preparing a solid-state 3,5-valent vanadium electrolyte as described in claim 1, characterized in that, The pressure for pressing the blocks is 50~200MPa.

4. A method for preparing a solid-state vanadium 3,5-valent electrolyte as described in claim 1, characterized in that, The reducing agent in the second stage includes one or more of oxalic acid and citric acid.

5. A method for preparing a solid 3,5-valent vanadium electrolyte as described in any one of claims 1 to 4, characterized in that, The VO(OH)2 solid was prepared by the following method: 1) Mix the vanadium-containing material with acid solution, adjust the pH of the mixture to ≤4, add a reducing agent at 1 to 5 times the theoretical required reaction amount, and stir the reaction at 200 to 400 rpm at 40 to 99°C for 0.5 to 5 hours to obtain a tetravalent vanadium solution. 2) Adjust the pH of the tetravalent vanadium solution obtained in step 1) to 6~12, stir the reaction at 20~50℃ and 200~400rpm for 0.5~2h, and obtain solid VO(OH)2 after filtration and drying.

6. A method for preparing a solid-state vanadium 3,5-valent electrolyte as described in claim 5, characterized in that, The vanadium-containing material includes one or more of sodium vanadate, potassium vanadate, crude vanadium, red vanadium, and vanadium leachate.

7. A method for preparing a solid-state 3,5-valent vanadium electrolyte as described in claim 5 or 6, characterized in that, The acid solution includes one or more of hydrochloric acid and sulfuric acid.

8. A method for preparing a solid-state 3,5-valent vanadium electrolyte as described in claim 5 or 6, characterized in that, The reducing agent includes one or more of the following: sulfite, sulfur dioxide, sodium sulfide, sucrose, glucose, fructose, and formic acid.

9. A method for preparing a solid-state 3,5-valent vanadium electrolyte as described in claim 5 or 6, characterized in that, The reagents used to adjust the pH value of the tetravalent vanadium solution obtained in step 1) include one or more of the following: NaOH, KOH, Na2CO3, NaHCO3, K2CO3, and KHCO3 at a concentration of 50-500 g / L.

10. A solid-state vanadium 3,5-valent electrolyte, characterized in that, The solid 3,5-valent vanadium electrolyte is prepared by the preparation method according to any one of claims 1 to 9.

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