Vanadium-based positive electrode material and vanadium-based calcium battery and preparation method thereof

Abstract

The application discloses a vanadium-based positive material and a vanadium-based calcium battery and a preparation method thereof, and belongs to the technical field of batteries. The preparation of the vanadium-based calcium battery is realized through the steps of multi-additive synergistic thermal phase reconstruction, thermal in-situ self-oxidation coupling acid immersion treatment, aluminum sulfate silicon removal purification and in-situ coordination hydrothermal modification of the vanadium-based positive material and the vanadium-based calcium battery assembly and performance test. The application adopts a liquid phase in-situ coordination integrated process, directly reacts high-purity purified vanadium liquid with an organic ligand to prepare an electrode precursor, simplifies a functional modification process, reduces material loss, has high vanadium resource utilization, realizes short-process and high-added-value conversion of vanadium slag from industrial solid waste to high-end energy storage electrode materials, and has extremely high application value and economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and particularly relates to a vanadium-based cathode material, a vanadium-based calcium battery, and a method for preparing the same. Background Technology

[0002] Vanadium is an important strategic rare metal, widely used in metallurgical alloys, chemical catalysis, and energy storage batteries. Vanadium slag is the core raw material for industrial vanadium extraction. Traditional vanadium slag extraction processes often involve complex steps such as high-temperature roasting, acid-base leaching, and extraction-back-extraction purification, which present several industry pain points: First, vanadium slag contains a large amount of inert vanadium spinel phase, and conventional activation methods are insufficient, resulting in low vanadium extraction and recovery rates. Second, vanadium slag has a high silicon impurity content, and soluble silicon easily precipitates during vanadium extraction, contaminating the vanadium product and significantly reducing product purity. Third, traditional processes are lengthy, with high reagent consumption, energy consumption, and production costs in purification steps such as extraction and back-extraction. Fourth, existing processes mostly only reach the level of crude vanadium extraction, resulting in low product added value and failing to realize the high-end, functional, and energy storage application transformation of vanadium resources, leading to low value in the industrial chain.

[0003] To address the aforementioned technical shortcomings, there is an urgent need to develop an integrated process for high-purity vanadium extraction and vanadium-based calcium battery preparation that is streamlined, thoroughly removes impurities, has a high recovery rate, and enables high-value utilization of vanadium resources. This would establish a complete technology chain encompassing vanadium slag extraction, functional modification, and energy storage applications. Summary of the Invention

[0004] In view of this, the present invention discloses a vanadium-based cathode material and a vanadium-based calcium battery and a method for preparing the same.

[0005] The present invention adopts the following technical solution: A method for preparing a vanadium-based cathode material, wherein the vanadium-based cathode material is prepared by extracting vanadium through phase reconstruction of hot vanadium slag, and the method includes the following steps: S1 Multi-component additive synergistic hot phase reconstruction: High-temperature smelting hot vanadium slag is used, and multi-component composite additives are added to the hot vanadium slag; relying on the high-temperature residual heat of the hot vanadium slag to complete the phase reconstruction and modification, destroy the inert vanadium spinel structure, realize the directional phase separation of vanadium and silicon components, and obtain reconstructed vanadium slag with low residual vanadium and high activity. S2 Hot in-situ self-oxidation coupled with acid leaching treatment: The high-temperature hot reconstructed vanadium slag obtained in S1 is placed in an air atmosphere. Relying on the residual heat of the hot vanadium slag itself and combined with the synergistic catalytic effect of the intrinsic elements Ca, Mg and Mn in the vanadium slag, the low-valent vanadium component is oxidized in-situ by air and completely converted into high-valent vanadium oxide. After oxidation, the oxidized vanadium slag is leached at a constant temperature with dilute sulfuric acid solution. After solid-liquid separation, the high-purity vanadium-containing leachate is collected. S3 Aluminum sulfate for silicon removal and purification: Aluminum sulfate is added to the high-purity vanadium-containing leachate, and the soluble silicon impurities are stirred to control the directional flocculation and precipitation. After filtration and slag removal, a high-purity vanadium purified solution with no sodium ion impurities and high purity and clarity is obtained. S4 In-situ coordination hydrothermal modification for the preparation of vanadium-based cathode materials: Using the high-purity vanadium purification solution as raw material, an in-situ coordination reaction is carried out with a 5-hydroxyquinoline ligand solution. After hydrothermal reaction, centrifugal washing, and vacuum drying, vanadium-based composite cathode powder with 5-hydroxyquinoline doping modification is obtained. The vanadium-based composite cathode powder, binder, and conductive agent are mixed to prepare a uniform electrode slurry. After coating, drying, and roll pressing and slicing, vanadium-based cathode materials are obtained.

[0006] Furthermore, the composite additive mentioned in S1 is a compound of one or more of CaO, MgO, CeO2, MgCO3 and CaCO3.

[0007] Furthermore, the temperature of the hot vanadium slag in S1 is 1100-1500℃, the amount of the composite additive added is 3%-10% of the mass of the hot vanadium slag, and the heat preservation time is 90-150 min.

[0008] Furthermore, the pH value of the dilute sulfuric acid solution described in S2 is 2.5 to 3.0.

[0009] Furthermore, the parameters of the leaching treatment include: liquid-to-solid ratio (2-4): 1 mL / g, leaching temperature 40-60℃, and leaching time 1-2 h.

[0010] Furthermore, the control of the amount of aluminum sulfate added in S3 includes: controlling the molar ratio of Si to Al in the system to be 1:(1-3), and the stirring time to be 15-40 min.

[0011] Further, the in-situ coordination reaction in S4 includes: the molar ratio of vanadium source to 5-hydroxyquinoline in the vanadium-based cathode material is (1-5):1; the vanadium source and 5-hydroxyquinoline ligand solution are mixed and stirred for 20-40 min; the hydrothermal reaction includes: placing it in a hydrothermal reactor and hydrothermally reacting at 100-220℃ for 2-12 h; the centrifugal washing includes: after the hydrothermal reaction is completed, the material is naturally cooled and then centrifuged and washed three times with deionized water and anhydrous ethanol respectively; the vacuum drying is vacuum drying at 80℃ overnight.

[0012] Furthermore, the binder is PVDF, the conductive agent is SUPERP conductive agent, and the vanadium-based composite cathode powder, PVDF, and SUPERP conductive agent are mixed in a mass ratio of 7:2:1 to prepare a uniform electrode slurry. The slurry is stirred for 3 to 6 hours. The drying temperature is 60 to 80°C and the drying time is 8 to 12 hours.

[0013] A vanadium-based cathode material, wherein the vanadium-based cathode material is prepared by the above method.

[0014] A vanadium-based calcium battery is disclosed, using the aforementioned vanadium-based positive electrode material as the working electrode, activated carbon (ACC) material as the negative electrode, and an ethylene glycol dimethyl ether (DME) solution containing dissolved calcium bis(trifluoromethanesulfonyl)imide (CaT) as the electrolyte. A button-type calcium battery is assembled under low-oxygen conditions, and electrochemical performance is tested after static activation. The oxygen content of the low-oxygen environment is below 0.1 ppm, and the static activation time is 10–14 h. The electrolyte is 150 μL of a 0.5 M solution of anhydrous calcium bis(trifluoromethanesulfonyl)imide dissolved in ethylene glycol dimethyl ether. At a low current density of 20 mA / g, the reversible specific capacity of the vanadium-based calcium battery can reach 293 mAh / g; at a high current density of 1 A / g, the reversible specific capacity stably reaches 151.3 mAh / g, and the capacity retention rate is 99% after 1000 long cycles.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention addresses the industry pain points of traditional vanadium slag extraction processes, such as insufficient activation, severe interference from silicon impurities, cumbersome procedures, low product purity, high energy consumption, low vanadium recovery rate, sodium ion contamination due to sodium salt introduction, and low product added value. It employs an in-situ phase reconstruction of hot vanadium slag coupled with aluminum sulfate silicon removal and purification, and a sodium-free short-process purification process. This allows for the direct preparation of battery electrode materials from high-purity vanadium solution, completely resolving the sodium ion residue interference problem of traditional processes. Furthermore, it adds an electrochemical application testing step, possessing several significant technical advantages: First, the S1 process of this invention relies on the residual heat modification of the primary hot vanadium slag from smelting, combined with the synergistic effect of CaO, MgO, CeO2, MgCO3, and CaCO3 multi-component composite additives. CaO directionally fixes silicon impurities, MgO inhibits the formation of inert vanadium spinel, CeO2 enhances catalytic oxidation, and carbonate components assist in regulating the phase structure and promoting efficient conversion of vanadium valence state. This achieves efficient separation of vanadium and silicon from the source, with residual vanadium content in the silicon phase ≤0.5% and vanadium component activation conversion rate ≥99.0%, completely solving the problem of silicon impurity interference and significantly reducing the difficulty of subsequent vanadium product purification.

[0016] Secondly, this invention eliminates the secondary roasting and activation process in traditional vanadium extraction, and completely abandons the use of sodium salt additives such as sodium carbonate. Relying on the heat storage of S1 hot vanadium slag and the synergistic effect of multi-component composite additives, while combining the intrinsic catalytic effect of Ca, Mg, and Mn elements in vanadium slag, it achieves efficient and high-valence activation of vanadium components in one step through multi-effect coupling. It completely eliminates the high-energy-consuming and high-impurity-risk process of traditional external high-temperature roasting and sodium salt additive co-firing, greatly simplifying the process flow, reducing production energy consumption and equipment investment, and preventing the introduction of sodium ion impurities from the source. The activated vanadium components have extremely high reactivity and can be efficiently dissolved by gentle leaching with dilute sulfuric acid, with a vanadium leaching rate of ≥98.5%. The resulting leachate is free of sodium ion doping, has low impurity content, and good purity, providing excellent raw material conditions for the subsequent preparation of high-purity electrode materials.

[0017] Third, this invention employs a targeted quantitative silicon removal process using aluminum sulfate, precisely controlling the aluminum-silicon molar ratio based on the silicon content of the leachate. This process can efficiently remove over 98% of soluble silicon impurities, completely solving the problem of silicon impurity contamination affecting the electrochemical performance of the electrode. The entire process eliminates redundant steps such as traditional extraction, back-extraction, ammonia precipitation, and powder drying, using the high-purity vanadium solution after silicon removal and purification directly as the raw material for electrode preparation. The process is tightly integrated, significantly shortening the preparation cycle and reducing reagent and energy costs, making it highly adaptable to industrial applications.

[0018] Fourth, this invention adopts an integrated liquid-phase in-situ coordination process, which eliminates the need for separate preparation and storage of vanadium-based powder materials. The electrode precursor is prepared directly by reacting high-purity vanadium liquid with 5-hydroxyquinoline ligand solution, simplifying the functionalization modification process, reducing material loss, and achieving high vanadium resource utilization. This enables a short-process, high-value-added transformation of vanadium slag from industrial solid waste to high-end energy storage electrode materials, while also significantly improving the specific capacity of the cathode material.

[0019] Fifth, this invention does not introduce any sodium salt additives throughout the entire process, completely avoiding the sodium ion residue problem caused by the addition of sodium salts in traditional vanadium extraction processes. It also eliminates the defects of sodium ion doping contamination during subsequent hydrolysis, vanadium precipitation, and electrode preparation, effectively avoiding the negative impact of sodium ions on the crystal structure, ion conduction efficiency, and battery cycle stability of vanadium-based electrodes. This ensures the high purity and excellent electrochemical performance of vanadium-based electrode materials from the source. The final vanadium-based calcium battery has both excellent rate performance and ultra-long cycle stability, high capacity at low current density, stable performance under high current conditions, no significant capacity decay after thousands of cycles, and excellent energy storage performance. It has opened up a complete technology chain from vanadium slag resource extraction to functional modification to electrochemical energy storage application, and significantly improved process integration and technology.

[0020] In summary, this invention features a compact process, streamlined procedures, thorough impurity removal, green and low-carbon operation, and high vanadium recovery rate. It is the first to propose a short-process integrated process that combines in-situ modification of hot vanadium slag, waste heat self-oxidation, wet purification, and direct electrode fabrication from vanadium liquid. This process can stably prepare high-performance vanadium-based calcium battery cathode materials, making it suitable for industrial-scale continuous production and high-end energy storage applications. It has extremely high application value and economic benefits. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic flowchart of a vanadium-based cathode material and a vanadium-based calcium battery preparation method according to the present invention. Detailed Implementation

[0023] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] Example 1

[0025] A vanadium-based cathode material and a vanadium-based calcium battery, and a method for preparing the same, wherein the cathode material is a vanadium-based cathode material, such as... Figure 1 As shown, the method includes the following steps: S1 Multi-component additive synergistic hot phase reconstruction: High-temperature smelting hot vanadium slag is used, and multi-component composite additives are added to the hot vanadium slag; relying on the high-temperature residual heat of the hot vanadium slag to complete the phase reconstruction and modification, destroy the inert vanadium spinel structure, realize the directional phase separation of vanadium and silicon components, and obtain reconstructed vanadium slag with low residual vanadium and high activity. S2 Hot In-situ Self-oxidation Coupled with Acid Leaching Treatment: The high-temperature hot reconstructed vanadium slag obtained in S1 is placed in an air atmosphere. Without the need for an additional external heat source or secondary roasting process, relying on the residual heat of the hot vanadium slag itself and combined with the synergistic catalytic effect of the intrinsic elements Ca, Mg, and Mn in the vanadium slag, the low-valent vanadium component is oxidized in-situ in the air and completely converted into high-valent vanadium oxide. After oxidation, the oxidized vanadium slag is leached at a constant temperature with dilute sulfuric acid solution. After solid-liquid separation, the high-purity vanadium-containing leachate is collected. S3 Aluminum sulfate desiliconization purification: Aluminum sulfate is added to the high-purity vanadium-containing leachate, and the soluble silicon impurities are stirred to control the directional flocculation and precipitation. After filtration to remove slag, a high-purity vanadium purified solution with no sodium ion impurities and high purity is obtained. No sodium salt additives are added throughout the process, eliminating sodium ion doping pollution from the source. This step achieves precise silicon removal purification. S4 In-situ coordination hydrothermal modification for preparing vanadium-based cathode materials: Using the high-purity vanadium purification solution as raw material, an in-situ coordination reaction is carried out with a 5-hydroxyquinoline ligand solution, wherein the ligand solution is an ethanol solution. After hydrothermal reaction, centrifugal washing, and vacuum drying, 5-hydroxyquinoline-doped modified vanadium-based composite cathode powder is obtained. The vanadium-based composite cathode powder, binder, and conductive agent are mixed to prepare a uniform electrode slurry, which is then coated, dried, and rolled into slices to obtain the vanadium-based cathode material. S5 Vanadium-based calcium battery assembly and performance testing: Using the vanadium-based positive electrode material as the working electrode, activated carbon (ACC) material as the negative electrode, and ethylene glycol dimethyl ether (DME) solution containing calcium bis(trifluoromethanesulfonyl)imide (CaT) as the electrolyte, a button-type calcium battery was assembled in a low-water-oxygen environment. After static activation, electrochemical performance testing was completed, and a vanadium-based calcium battery with high stability and high rate performance was obtained.

[0026] Furthermore, the composite additive mentioned in S1 is a compound of one or more of CaO, MgO, CeO2, MgCO3 and CaCO3.

[0027] Furthermore, the temperature of the hot vanadium slag in S1 is 1100-1500℃, and the amount of the composite additive added is 3%-10% of the mass of the hot vanadium slag; the heat preservation time is 90-150 min; under this parameter range, efficient phase separation of vanadium and silicon can be achieved, the residual vanadium content in the silicon phase is ≤0.5%, and the activation conversion rate of the vanadium component is ≥99.0%.

[0028] Furthermore, the pH value of the dilute sulfuric acid solution described in S2 is 2.5–3.0. Furthermore, the parameters of the leaching treatment described in S2 include: liquid-to-solid ratio (2-4): 1 mL / g, leaching temperature 40-60℃, and leaching time 1-2 h; under this process, vanadium oxidation and activation are thorough, water solubility is good, vanadium leaching rate is ≥98.5%, and impurity passivation and retention effect is excellent.

[0029] Furthermore, the control of the amount of aluminum sulfate added in S3 includes: controlling the molar ratio of Si to Al in the system to be 1:(1-3), and the stirring time to be 15-40 min; this parameter range can remove more than 98% of soluble silicon impurities, obtain high-purity clear vanadium solution, the comprehensive extraction and utilization rate of valuable vanadium is ≥99.2%, there is no sodium ion impurity residue, and it can be directly used for in-situ coordination preparation of vanadium-based electrode precursors.

[0030] Further, the in-situ coordination reaction in S4 includes: the molar ratio of vanadium source to 5-hydroxyquinoline in the cathode material is (1-5):1, and the vanadium source and 5-hydroxyquinoline ligand solution are mixed and stirred for 20-40 min; the hydrothermal reaction includes: placing it in a hydrothermal reactor and hydrothermally reacting at 100-220℃ for 2-12 h; the centrifugal washing includes: after the hydrothermal reaction is completed, the material is naturally cooled and then centrifuged and washed three times with deionized water and anhydrous ethanol respectively; the vacuum drying is carried out at 80℃ overnight to obtain the vanadium-based composite cathode powder.

[0031] Furthermore, the binder is PVDF, and the conductive agent is SUPERP conductive agent. The vanadium-based composite cathode powder, PVDF, and SUPERP conductive agent are mixed at a mass ratio of 7:2:1 to prepare a uniform electrode slurry. The slurry is stirred for 3 to 6 hours. The drying temperature is 60 to 80°C and the drying time is 8 to 12 hours to prepare a vanadium-based cathode electrode sheet with uniform structure and stable performance.

[0032] Furthermore, the oxygen content of the low-water-oxygen environment described in S5 is less than 0.1 ppm, and the static activation time is 10–14 h; the electrolyte is 150 μL of anhydrous bis(trifluoromethanesulfonyl)imide calcium (CaT) with a concentration of 0.5 M dissolved in dimethyl ethylene glycol (DME).

[0033] A vanadium-based cathode material, wherein the vanadium-based cathode material is prepared by the above method.

[0034] A vanadium-based calcium battery, wherein the vanadium-based calcium battery uses the above-mentioned battery cathode material, and the reversible specific capacity of the vanadium-based calcium battery can reach 293 mAh / g at a low current density of 20 mA / g; at a high current density of 1 A / g, the reversible specific capacity can stably reach 151.3 mAh / g, and the capacity retention rate is 99% after 1000 long cycles.

[0035] Example 2

[0036] Step S1 of the present invention: S1 Synergistic hot phase reconstruction with multiple additives: Hot vanadium slag smelted at 1200℃ is used, and CaO additive with a mass ratio of 20% is added. The vanadium is kept at 1200℃ for 120 min to complete the directional phase separation modification of vanadium and silicon, effectively enhance the fixation effect of silicon impurities, and the residual vanadium content in the silicon phase of the reconstructed vanadium slag is as low as 0.19%, and the vanadium activation conversion rate is ≥99.0%.

[0037] Example 3

[0038] Step S1 of the present invention: S1 Synergistic hot phase reconstruction with multiple additives: Hot vanadium slag smelted at 1200℃ is used, and 10% CaO and 5% CeO2 additives are added by mass. The mixture is kept at 1200℃ for 120 min to complete the directional phase separation modification of vanadium and silicon, effectively enhance the fixation effect of silicon impurities, and the residual vanadium content in the silicon phase of the reconstructed vanadium slag is as low as 0.10%, and the vanadium activation conversion rate is ≥99.0%.

[0039] Example 4

[0040] Steps S1 and S2 of the present invention: S1 Synergistic hot phase reconstruction with multiple additives: Hot vanadium slag smelted at 1200℃ is used, and CaO additive with a mass ratio of 20% is added. The vanadium is kept at 1200℃ for 120 min to complete the directional phase separation modification of vanadium and silicon, effectively enhance the fixation effect of silicon impurities, and the residual vanadium content in the silicon phase of the reconstructed vanadium slag is as low as 0.19%, and the vanadium activation conversion rate is ≥99.0%.

[0041] S2 Hot In-Situ Oxidation Coupled with Acid Leaching: The high-temperature hot-reconstructed vanadium slag produced in S1 is directly placed in an air atmosphere. Relying on its own residual heat and combined with the synergistic catalytic effect of the inherent Ca, Mg, and Mn elements in the vanadium slag, in-situ air oxidation is completed, allowing low-valence vanadium to be fully converted into high-valence vanadium oxides. The oxidized vanadium slag does not require secondary roasting. The pH value of the dilute sulfuric acid solution is pre-adjusted to 2.8 before leaching treatment, with a liquid-to-solid ratio of 3:1 mL / g, a leaching temperature of 50℃, and a leaching time of 1.5 h. After solid-liquid separation, the vanadium-containing leachate is collected, with a vanadium leaching rate ≥98.5%. Example 5

[0042] Steps S1 and S2 of the present invention: S1 Synergistic hot phase reconstruction with multiple additives: Hot vanadium slag smelted at 1200℃ is used, and CaO additive with a mass ratio of 20% is added. The vanadium is kept at 1200℃ for 120 min to complete the directional phase separation modification of vanadium and silicon, effectively enhance the fixation effect of silicon impurities, and the residual vanadium content in the silicon phase of the reconstructed vanadium slag is as low as 0.19%, and the vanadium activation conversion rate is ≥99.0%.

[0043] S2 Hot In-situ Oxidation Coupled with Acid Leaching: The high-temperature hot-reconstructed vanadium slag produced in S1 is directly placed in the air atmosphere. Relying on its own residual heat and combined with the synergistic catalytic effect of the inherent Ca, Mg, and Mn elements in the vanadium slag, in-situ air oxidation is completed, so that low-valent vanadium is fully converted into high-valent vanadium oxide. The oxidized vanadium slag does not need to be roasted again. The pH value of the dilute sulfuric acid solution is pre-adjusted to 3.5 before leaching treatment. The liquid-solid ratio is 3:1 mL / g, the leaching temperature is 50℃, and the leaching time is 1.5 h. After solid-liquid separation, the vanadium-containing leachate is collected, and the vanadium leaching rate is ≥92%.

[0044] Example 6

[0045] Steps S1 and S2 of the present invention: S1 Synergistic hot phase reconstruction with multiple additives: Hot vanadium slag smelted at 1200℃ is used, and CaO additive with a mass ratio of 20% is added. The vanadium is kept at 1200℃ for 120 min to complete the directional phase separation modification of vanadium and silicon, effectively enhance the fixation effect of silicon impurities, and the residual vanadium content in the silicon phase of the reconstructed vanadium slag is as low as 0.19%, and the vanadium activation conversion rate is ≥99.0%.

[0046] S2 Hot In-situ Oxidation Coupled with Acid Leaching: The high-temperature hot reconstructed vanadium slag produced in S1 is directly placed in the air atmosphere. Relying on its own residual heat and combined with the synergistic catalytic effect of the inherent Ca, Mg, and Mn elements in the vanadium slag, in-situ air oxidation is completed, so that low-valence vanadium is fully converted into high-valence vanadium oxide. The oxidized vanadium slag does not need to be roasted again. The pH value of the dilute sulfuric acid solution is pre-adjusted to 2.8 before leaching treatment. The liquid-solid ratio is 3:1 mL / g, the leaching temperature is 50℃, and the leaching time is 1.5 h. After solid-liquid separation, the vanadium-containing leachate is collected, and the vanadium leaching rate is ≥98.5%.

[0047] S3 Aluminum sulfate for silicon removal and purification: Aluminum sulfate is added according to the Si to Al molar ratio of 1:1 in the liquid. Stirring at room temperature for 25 min removes silicon and flocculates for purification. Soluble silicon impurities in the system are efficiently removed. Filtration removes flocculated precipitates to obtain sodium-free, high-purity, clear vanadium-containing raw solution, which can be directly used for subsequent electrode precursor preparation. The silicon removal rate is 90%.

[0048] Example 7

[0049] Steps S1, S2, and S3 of this invention: S1 Synergistic hot phase reconstruction with multiple additives: Hot vanadium slag smelted at 1200℃ is used, and CaO additive with a mass ratio of 20% is added. The vanadium is kept at 1200℃ for 120 min to complete the directional phase separation modification of vanadium and silicon, effectively enhance the fixation effect of silicon impurities, and the residual vanadium content in the silicon phase of the reconstructed vanadium slag is as low as 0.19%, and the vanadium activation conversion rate is ≥99.0%.

[0050] S2 Hot In-situ Oxidation Coupled with Acid Leaching: The high-temperature hot reconstructed vanadium slag produced in S1 is directly placed in the air atmosphere. Relying on its own residual heat and combined with the synergistic catalytic effect of the inherent Ca, Mg, and Mn elements in the vanadium slag, in-situ air oxidation is completed, so that low-valence vanadium is fully converted into high-valence vanadium oxide. The oxidized vanadium slag does not need to be roasted again. The pH value of the dilute sulfuric acid solution is pre-adjusted to 2.8 before leaching treatment. The liquid-solid ratio is 3:1 mL / g, the leaching temperature is 50℃, and the leaching time is 1.5 h. After solid-liquid separation, the vanadium-containing leachate is collected, and the vanadium leaching rate is ≥98.5%.

[0051] S3 Aluminum sulfate for silicon removal and purification: Aluminum sulfate is added according to the Si to Al molar ratio of 1:2 in the liquid. Stirring at room temperature for 25 min removes silicon and flocculates for purification. Soluble silicon impurities in the system are efficiently removed. Filtration removes flocculated precipitates to obtain sodium-free, high-purity, clear vanadium-containing raw solution, which can be directly used for subsequent electrode precursor preparation. The silicon removal rate is 95%.

[0052] Example 8

[0053] Steps S1 to S5 of this invention: S1 Synergistic hot phase reconstruction with multiple additives: Hot vanadium slag smelted at 1200℃ is used, and CaO additive with a mass ratio of 20% is added. The vanadium is kept at 1200℃ for 120 min to complete the directional phase separation modification of vanadium and silicon, effectively enhance the fixation effect of silicon impurities, and the residual vanadium content in the silicon phase of the reconstructed vanadium slag is as low as 0.19%, and the vanadium activation conversion rate is ≥99.0%.

[0054] S2 Hot In-situ Oxidation Coupled with Acid Leaching: The high-temperature hot reconstructed vanadium slag produced in S1 is directly placed in the air atmosphere. Relying on its own residual heat and combined with the synergistic catalytic effect of the inherent Ca, Mg, and Mn elements in the vanadium slag, in-situ air oxidation is completed, so that low-valence vanadium is fully converted into high-valence vanadium oxide. The oxidized vanadium slag does not need to be roasted again. The pH value of the dilute sulfuric acid solution is pre-adjusted to 2.8 before leaching treatment. The liquid-solid ratio is 3:1 mL / g, the leaching temperature is 50℃, and the leaching time is 1.5 h. After solid-liquid separation, the vanadium-containing leachate is collected, and the vanadium leaching rate is ≥98.5%.

[0055] S3 Aluminum sulfate for silicon removal and purification: Aluminum sulfate is added according to the Si to Al molar ratio of 1:2 in the liquid, and stirred at room temperature for 25 min to remove silicon flocculation and purification, which efficiently removes soluble silicon impurities in the system. The flocculated precipitate is removed by filtration to obtain sodium-free, high-purity, clear vanadium-containing raw solution, which can be directly used for the preparation of subsequent electrode precursors.

[0056] Preparation of S4 vanadium-based electrode precursor and electrode sheet: High-purity vanadium-containing raw liquid purified from S3 was used to prepare a vanadium-based active substrate containing V2O5, with the molar ratio of V to 5-hydroxyquinoline controlled at 1.3:1. After mixing and stirring for 30 min to complete in-situ coordination, the mixture was transferred to a 100 mL hydrothermal reactor and reacted at 120℃ for 6 h (within the preferred parameter range of 100-220℃ and 2-12 h). After cooling after the reaction, the mixture was washed three times each with deionized water and anhydrous ethanol by centrifugation, and then vacuum dried overnight at 80℃ to obtain high-purity vanadium-based complex powder. The modified positive electrode active material, PVDF, and SUPERP conductive agent were mixed in a mass ratio of 7:2:1 and stirred continuously for 4 h to prepare a uniform electrode slurry. The slurry was dried at 70℃ for 10 h and then rolled and sliced ​​to obtain a vanadium-based composite positive electrode sheet.

[0057] S5 Calcium Battery Preparation and Testing: Using the vanadium-based composite positive electrode sheet prepared above as the working electrode, activated carbon (ACC) was used as the negative electrode material. A 150 μL solution of 0.5 M anhydrous calcium bis(trifluoromethanesulfonyl)imide (CaT) in dimethyl ethylene glycol (DME) was selected as the electrolyte. A glass fiber separator was used, and a CR2032 button-type calcium battery was assembled in a vacuum glove box with a water and oxygen content of <0.1 ppm. The battery was then allowed to stand for 12 h for activation. Electrochemical performance was tested using a Blue Battery testing system. The results showed a specific capacity of 293 mAh / g at a current density of 20 mA / g, 151.3 mAh / g at a current density of 1 A / g, and a capacity retention of 99% after 1000 cycles. Experimental verification showed that the specific capacity of the prepared calcium battery positive electrode material reached its optimal level when the molar ratio of vanadium (V) to 5-hydroxyquinoline was 1.3:1.

[0058] Example 9

[0059] Steps S1 to S5 of this invention: S1 Synergistic hot phase reconstruction with multiple additives: Hot vanadium slag smelted at 1200℃ is used, and CaO additive with a mass ratio of 20% is added. The vanadium is kept at 1200℃ for 120 min to complete the directional phase separation modification of vanadium and silicon, effectively enhance the fixation effect of silicon impurities, and the residual vanadium content in the silicon phase of the reconstructed vanadium slag is as low as 0.19%, and the vanadium activation conversion rate is ≥99.0%.

[0060] S2 Hot In-situ Oxidation Coupled with Acid Leaching: The high-temperature hot reconstructed vanadium slag produced in S1 is directly placed in the air atmosphere. Relying on its own residual heat and combined with the synergistic catalytic effect of the inherent Ca, Mg, and Mn elements in the vanadium slag, in-situ air oxidation is completed, so that low-valence vanadium is fully converted into high-valence vanadium oxide. The oxidized vanadium slag does not need to be roasted again. The pH value of the dilute sulfuric acid solution is pre-adjusted to 2.8 before leaching treatment. The liquid-solid ratio is 3:1 mL / g, the leaching temperature is 50℃, and the leaching time is 1.5 h. After solid-liquid separation, the vanadium-containing leachate is collected, and the vanadium leaching rate is ≥98.5%.

[0061] S3 Aluminum sulfate for silicon removal and purification: Aluminum sulfate is added according to the Si to Al molar ratio of 1:2 in the liquid, and stirred at room temperature for 25 min to remove silicon flocculation and purification, which efficiently removes soluble silicon impurities in the system. The flocculated precipitate is removed by filtration to obtain sodium-free, high-purity, clear vanadium-containing raw solution, which can be directly used for the preparation of subsequent electrode precursors.

[0062] Preparation of S4 vanadium-based electrode precursor and electrode sheet: High-purity vanadium-containing raw liquid purified from S3 was used to prepare a vanadium-based active substrate containing V2O5. The molar ratio of V to 5-hydroxyquinoline was controlled at 4:1 (within the preferred range of 1 to 5:1) for doping and composite modification. After mixing and stirring for 30 min to complete in-situ coordination, the mixture was transferred to a 100 mL hydrothermal reactor and reacted at 120℃ for 6 h (within the preferred parameter range of 100 to 220℃ and 2 to 12 h). After the reaction was completed and cooled, the mixture was washed three times each with deionized water and anhydrous ethanol by centrifugation, and then vacuum dried overnight at 80℃ to obtain high-purity vanadium-based complex powder. The modified positive electrode active material, PVDF, and SUPERP conductive agent were mixed in a mass ratio of 7:2:1 and stirred continuously for 4 h to prepare a uniform electrode slurry. The slurry was dried at 70℃ for 10 h and then rolled and sliced ​​to obtain a vanadium-based composite positive electrode sheet.

[0063] S5 Calcium Battery Preparation and Testing: Using the vanadium-based composite positive electrode sheet prepared above as the working electrode, activated carbon (ACC) was used as the negative electrode material. A 150 μL solution of 0.5 M anhydrous bis(trifluoromethanesulfonyl)imide calcium (CaT) in dimethyl ethylene glycol (DME) was selected as the electrolyte. A glass fiber separator was used, and CR2032 button calcium batteries were assembled in a vacuum glove box with a water and oxygen content of <0.1 ppm and allowed to stand for 12 h for activation. Electrochemical performance was tested using a Blue Battery Testing System. The test results showed that the specific capacity was 270 mAh / g at a current density of 20 mA / g, 145 mAh / g at a current density of 1 A / g, and the capacity retention rate was 99% after 1000 long cycles.

[0064] Example 10

[0065] A method for extracting vanadium from vanadium slag through hot phase reconstruction and preparing battery cathode materials includes the following steps: S1 Multi-component additive synergistic hot phase reconstruction: Take hot vanadium slag from smelting, add composite additives to the hot vanadium slag, and rely on high-temperature waste heat to achieve directional phase separation modification of vanadium and silicon components, destroy the inert vanadium spinel structure, fix silicon impurity components, and obtain reconstructed vanadium slag with low residual vanadium and high activity.

[0066] S2 Hot In-situ Oxidation Coupled with Acid Leaching: The high-temperature hot reconstructed vanadium slag obtained by S1 modification is placed in an air atmosphere. Relying on the residual heat of the hot vanadium slag itself and the synergistic catalytic effect of the inherent Ca, Mg and Mn elements in the vanadium slag, the vanadium components are oxidized in situ in the air. The low-valence vanadium is fully converted into stable high-valence vanadium oxide to obtain vanadium oxide slag. No additional roasting or external heating source is required. After oxidation, the pH value of the dilute sulfuric acid acid solution is pre-adjusted, and then the vanadium oxide slag is leached. After leaching, solid and liquid are separated, and the high-purity vanadium-containing leachate is collected, while solid impurities are retained.

[0067] S3 Leaching solution is purified by aluminum sulfate to remove silicon and prepare high-purity vanadium purified solution: Aluminum sulfate is added to the crude vanadium-containing leachate obtained in S2 for silicon removal and flocculation purification. The amount of aluminum sulfate added is precisely based on the silicon content in the leachate to complete the flocculation and precipitation of impurities, fully remove soluble silicon impurities from the solution, and obtain a clear, high-purity vanadium purified solution after filtration and slag removal, which can be used as a direct raw material for preparing vanadium-based calcium battery electrodes.

[0068] Preparation of S4 vanadium-based electrode precursor and electrode sheet: Using the high-purity vanadium purified solution obtained in S3 as raw material, an in-situ coordination reaction was carried out with 5-hydroxyquinoline ligand solution. The mixture was stirred continuously for 30 min to obtain a uniformly mixed precursor solution. The precursor solution was transferred into a 100 mL hydrothermal reactor and hydrothermally reacted at 100–220 °C for 2–12 h. After the reaction, the mixture was naturally cooled and washed three times with deionized water and three times with anhydrous ethanol. Then, it was dried overnight in an 80 °C vacuum drying oven to obtain high-purity vanadium-based complex powder. The obtained vanadium-based complex powder was uniformly mixed with a conductive agent and a binder, stirred and dispersed to obtain a uniform electrode slurry. After coating and drying, a vanadium-based positive electrode sheet was prepared.

[0069] S5 Vanadium-based calcium battery preparation and performance testing: Using the vanadium-based positive electrode sheet prepared above as the working electrode, a button-type calcium battery was assembled by matching the counter electrode, electrolyte and separator. After the battery was statically activated, systematic electrochemical performance testing was carried out to complete the performance characterization of the electrode materials.

[0070] The purpose of this invention is to provide a method for extracting vanadium from vanadium slag through phase reconstruction in hot vanadium slag and preparing battery cathode materials, thereby overcoming the technical shortcomings of existing vanadium extraction processes, such as insufficient activation, significant interference from silicon impurities, reliance on sodium salt additives to introduce sodium ion impurities, cumbersome procedures, high energy consumption, and low product added value. This invention relies on in-situ phase reconstruction using residual heat from hot vanadium slag, self-oxidation using residual heat in air atmosphere, and sodium-free wet silicon removal purification processes. It directly prepares vanadium-based battery electrodes using purified high-purity vanadium liquid as raw material, eliminating redundant processes such as powdering, precipitation, and calcination. This short-process achieves high-value conversion of vanadium slag resources and its application in calcium battery energy storage. The process is green, simplified, high-purity, and suitable for industrial production.

[0071] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a vanadium-based cathode material, characterized in that, The vanadium-based cathode material is prepared by extracting vanadium through phase reconstruction of hot vanadium slag, and the method includes the following steps: S1 Synergistic hot phase reconstruction with multi-component additives: Hot vanadium slag from high-temperature smelting is used, and multi-component composite additives are added to the hot vanadium slag; phase reconstruction and modification are completed by relying on the high-temperature residual heat of the hot vanadium slag, destroying the inert vanadium spinel structure, realizing the directional phase separation of vanadium and silicon components, and obtaining reconstructed vanadium slag with low residual vanadium and high activity; the composite additives include one or both of CaO and CeO2. S2 Hot in-situ self-oxidation coupled with acid leaching treatment: The high-temperature hot reconstructed vanadium slag obtained in S1 is placed in an air atmosphere. Relying on the residual heat of the hot vanadium slag itself and combined with the synergistic catalytic effect of the intrinsic elements Ca, Mg and Mn in the vanadium slag, the low-valent vanadium component is oxidized in-situ by air and completely converted into high-valent vanadium oxide. After oxidation, the oxidized vanadium slag is leached at a constant temperature with dilute sulfuric acid solution. After solid-liquid separation, the high-purity vanadium-containing leachate is collected. S3 Aluminum sulfate for silicon removal and purification: Aluminum sulfate is added to the high-purity vanadium-containing leachate, and the soluble silicon impurities are stirred to control the directional flocculation and precipitation. After filtration and slag removal, a high-purity vanadium purified solution with no sodium ion impurities and high purity and clarity is obtained. S4 In-situ coordination hydrothermal modification for the preparation of vanadium-based cathode materials: Using the high-purity vanadium purification solution as raw material, an in-situ coordination reaction is carried out with a 5-hydroxyquinoline ligand solution. After hydrothermal reaction, centrifugal washing, and vacuum drying, vanadium-based composite cathode powder with 5-hydroxyquinoline doping modification is obtained. The vanadium-based composite cathode powder, binder, and conductive agent are mixed to prepare a uniform electrode slurry. After coating, drying, and roll pressing and slicing, vanadium-based cathode materials are obtained.

2. The method according to claim 1, characterized in that, The temperature of the hot vanadium slag in S1 is 1100-1500℃, and the amount of the composite additive added is 3%-10% of the mass of the hot vanadium slag; the heat preservation time is 90-150 min.

3. The method according to claim 2, characterized in that, The pH value of the dilute sulfuric acid solution described in S2 is 2.5 to 3.

0.

4. The method according to claim 3, characterized in that, The parameters of the leaching treatment include: liquid-to-solid ratio (2-4): 1 mL / g, leaching temperature 40-60℃, and leaching time 1-2 h.

5. The method according to claim 4, characterized in that, The control of aluminum sulfate dosage in S3 includes: controlling the molar ratio of Si to Al in the system to be 1:(1-3), and the stirring time to be 15-40 min.

6. The method according to claim 5, characterized in that, The in-situ coordination reaction described in S4 includes: the molar ratio of vanadium source to 5-hydroxyquinoline in the vanadium-based cathode material is (1-5):1; the vanadium source and 5-hydroxyquinoline ligand solution are mixed and stirred for 20-40 min; the hydrothermal reaction includes: placing the mixture in a hydrothermal reactor and reacting it at 100-220℃ for 2-12 h; the centrifugal washing includes: after the hydrothermal reaction is completed, the mixture is naturally cooled and then centrifuged and washed three times with deionized water and anhydrous ethanol respectively; the vacuum drying is performed at 80℃ overnight.

7. The method according to claim 6, characterized in that, The binder is PVDF, and the conductive agent is SUPERP conductive agent. The vanadium-based composite cathode powder, PVDF, and SUPERP conductive agent are mixed in a mass ratio of 7:2:1 to prepare a uniform electrode slurry. The slurry is stirred for 3 to 6 hours. The drying temperature is 60 to 80°C and the drying time is 8 to 12 hours.

8. A vanadium-based cathode material, characterized in that, The vanadium-based cathode material is prepared using the method described in any one of claims 1-7.

9. A vanadium-based calcium battery, characterized in that, Using the vanadium-based positive electrode material as described in claim 8 as the working electrode, activated carbon material as the negative electrode, and an ethylene glycol dimethyl ether solution containing calcium bis(trifluoromethanesulfonyl)imide as the electrolyte, a button-type calcium battery was assembled in a low-water-oxygen environment. After static activation, electrochemical performance testing was performed to obtain a vanadium-based calcium battery. The oxygen content of the low-water-oxygen environment was less than 0.1 ppm, and the static activation time was 10–14 h. The electrolyte was 150 μL of 0.5 M anhydrous calcium bis(trifluoromethanesulfonyl)imide dissolved in ethylene glycol dimethyl ether. At a low current density of 20 mA / g, the reversible specific capacity of the vanadium-based calcium battery can reach 293 mAh / g; at a high current density of 1 A / g, the reversible specific capacity stably reaches 151.3 mAh / g, and the capacity retention rate is 99% after 1000 long cycles.

Images