Pure-phase vanadium trioxide material and preparation method thereof

Abstract

The invention belongs to the technical field of chemical material synthesis, and particularly relates to a pure-phase vanadium trioxide material and a preparation method thereof. The preparation method comprises the following steps: (1) mixing vanadium pentoxide and citric acid monohydrate, and grinding; (2) accurately weighing a proper mass of the mixture powder, and pressing the mixture powder into round tablets; (3) the tablets are assembled in a heating cavity of heating equipment, and vacuumizing-inflating treatment is carried out; (4) under argon / nitrogen atmospheres with different air pressures, fixed heat treatment parameters are input, and rapid flash burning is conducted for 10-60 s; and (5) cooling, and collecting to obtain a black fluffy pure vanadium trioxide product. Based on the Joule heating flash burning technology, by accurately controlling the pressure of the reaction atmosphere, efficient conversion from a V2O3 precursor containing a VO2 impure phase to pure-phase V2O3 is achieved, and a high-quality vanadium trioxide material is provided for the fields of zinc ion batteries and the like.

Description

Technical Field

[0001] This invention belongs to the field of chemical material synthesis technology, specifically relating to a pure-phase vanadium trioxide material and its preparation method. Background Technology

[0002] With the rapid development of renewable energy technologies, aqueous zinc-ion batteries, with their advantages of high safety, low cost, and environmental friendliness, have become a research hotspot in the field of large-scale energy storage. In aqueous zinc-ion batteries, the performance of the cathode material directly affects the battery's energy density, cycle life, and power characteristics. Vanadium trioxide, as an important vanadium oxide, possesses unique electronic structure and crystal properties, and is considered a highly promising candidate for cathode materials in zinc-ion batteries.

[0003] Currently, there are various methods for preparing vanadium trioxide, but all of them have obvious limitations:

[0004] (1) Hydrogen reduction method: Vanadium pentoxide (V2O5) is reduced to vanadium trioxide (V2O3) using hydrogen at high temperature. This method is complex, and the use of hydrogen poses safety hazards. It also requires high control of reaction conditions and consumes a lot of energy. (2) Carbothermic reduction method: Vanadium pentoxide is reduced using carbon as a reducing agent at high temperature. This method easily introduces carbon impurities, limiting the purity of the product. The high reaction temperature and long reaction time result in high energy consumption and low production efficiency. (3) Thermal decomposition method: Vanadium trioxide is obtained by heating and decomposing vanadates such as ammonium vanadate and ammonium metavanadate. This method produces products with low purity, and various vanadium oxide mixtures may be generated during the decomposition process, making separation and purification difficult. (4) Chemical vapor deposition method: Vanadium trioxide is deposited on a substrate using vanadium-containing volatile precursors (such as VO(acac)2, VOCl3, etc.) and reaction gases (H2, O2). This method has complex equipment, high cost, and is not suitable for large-scale production. (5) Hydrothermal / solvothermal method: Vanadium source and reducing agent are placed in a high-pressure reactor, and vanadium trioxide is generated by utilizing a certain temperature and the self-generated pressure of the reactor. This method has a long reaction cycle, usually requiring tens of hours, poor repeatability, and high equipment requirements.

[0005] Furthermore, vanadium trioxide prepared by traditional methods is unstable in air and easily oxidizes slowly into high-valence vanadium oxides, affecting its performance. In particular, during the preparation process, vanadium trioxide (V₂O₃) containing vanadium dioxide (VO₂) impurities is readily generated, severely impacting its performance in electrochemical devices. Therefore, developing an efficient, energy-saving, and controllable method for preparing pure-phase vanadium trioxide is of great significance for promoting the development of zinc-ion battery technology.

[0006] In recent years, Joule heating flash calcination technology has attracted attention as a novel material preparation method due to its rapid heating and cooling, low energy consumption, and controllable process. This technology directly applies a large current to the precursor, causing it to reach the reaction temperature in a very short time, thus achieving rapid phase transformation and crystallization. However, there are no reports on applying this technology to the preparation of pure-phase vanadium trioxide, particularly in eliminating impurity phases by controlling the atmosphere pressure. Summary of the Invention

[0007] The purpose of this invention is to address the aforementioned problems by providing a simple, efficient, and energy-saving method for preparing vanadium trioxide with a single phase, thus solving the problems of complex processes, high energy consumption, and impurity phases in the products of existing technologies. This invention is based on Joule heating flash calcination technology and achieves efficient conversion from a V₂O₃ precursor containing VO₂ impurities to pure V₂O₃ through precise control of the reaction atmosphere pressure, providing high-quality vanadium trioxide materials for high-tech fields such as zinc-ion batteries.

[0008] The present invention provides a method for preparing a pure-phase vanadium trioxide material, comprising the following steps:

[0009] (1) Raw material mixing: Vanadium pentoxide (V2O5) and citric acid monohydrate (C6H8O7·H2O) are mixed in a certain molar ratio and ground thoroughly with a mortar until a uniform powder is formed. Citric acid monohydrate acts as both a reducing agent and a binder in the subsequent tableting process.

[0010] (2) Tableting: Accurately weigh an appropriate amount of the above-mentioned mixture powder and compress it into round tablets using a tablet press under a pressure of 10 MPa. The tableting process helps to increase the bulk density of the material, enhance conductivity, and promote the uniform distribution of current during Joule heating.

[0011] (3) Equipment assembly and vacuuming: Place the tablet in a conductive graphite boat, and then place the graphite boat into the heating chamber of the Joule heating device. After sealing the heating chamber, perform a vacuuming-gas-filling cycle to ensure that the air in the reaction chamber is completely removed to avoid interference from oxygen in the reduction process.

[0012] (4) Flash burning treatment: Under argon / nitrogen atmospheres of different pressures (3-10 atm), after inputting fixed heating parameters into the Joule heating device, rapid flash burning is performed, with the flash burning duration controlled between 10-60 seconds. During this process, vanadium pentoxide is rapidly reduced to vanadium trioxide, while the VO2 impurity phase is effectively eliminated.

[0013] (5) Product collection: After flash burning, cool to room temperature and collect the black, fluffy pure phase vanadium trioxide (V2O3) product.

[0014] Preferably, the molar ratio of vanadium pentoxide to citric acid monohydrate in step (1) is 1:1 to 1:1.2.

[0015] Preferably, the grinding time in step (1) is 20-40 minutes.

[0016] Preferably, the mass of the mixed powder weighed in step (2) is 0.3-0.8g.

[0017] Preferably, the pressing in step (2) is performed using a tablet press at a pressure of 10 MPa.

[0018] Preferably, the vacuuming and inflation cycles in step (3) are repeated 3 times.

[0019] Preferably, the pressure of the argon / nitrogen gas in step (4) is 3 atm-10 atm.

[0020] Preferably, the heat treatment parameters in step (4) are 800℃, 40V, and 220A.

[0021] Preferably, the cooling in step (5) is water cooling provided by the Joule heating device, and the water cooling temperature is 15°C.

[0022] The present invention also provides a pure-phase vanadium trioxide material prepared according to the above preparation method.

[0023] Compared to existing technologies, the core innovation of this invention lies in discovering and utilizing the crucial influence of atmospheric pressure on product purity during Joule flash combustion. Through systematic research on the elimination effect of VO2 impurities under different pressure conditions, the optimal pressure range (3-10 atm) for obtaining pure V2O3 was determined. Compared to traditional methods, this invention not only significantly shortens the reaction time and reduces energy consumption but also effectively improves product purity, exhibiting excellent charge-discharge performance when applied to zinc-ion battery cathode materials.

[0024] Compared with the prior art, the present invention has the following outstanding features and advantages:

[0025] (1) High efficiency and speed: Using Joule heating flash burning technology, the reaction time is only 10-60 seconds, which is tens or even hundreds of times more efficient than the traditional method that requires several hours of reaction time.

[0026] (2) Energy consumption is significantly reduced: The instantaneous characteristics of the flash combustion process enable concentrated energy utilization, avoiding the energy waste of traditional high-temperature furnaces that maintain high temperature for a long time, and the overall energy consumption is greatly reduced.

[0027] (3) High product purity: By precisely controlling the atmosphere pressure, the generation of VO2 impurity phase is effectively suppressed, and pure phase V2O3 is obtained.

[0028] (4) Simple process and low cost: No complicated equipment or multi-step processing is required, the process flow is simplified, and it is easy to scale up production. Moreover, the raw materials used, vanadium pentoxide and citric acid monohydrate, are inexpensive, and the preparation cost of vanadium trioxide is low, which has significant economic benefits.

[0029] (5) When applied to zinc-ion battery cathode materials, it exhibits good charge-discharge performance at 2A g. -1 The initial charge specific capacity at the current density is 267 mAh g. -1 Even after 800 charge cycles, the specific capacity still maintains 198 mAh g. -1 It exhibits excellent cycle performance, providing high-quality vanadium trioxide materials for fields such as zinc-ion batteries. Attached Figure Description

[0030] Figure 1 This is a diagram of a disc-shaped tablet of the mixture of vanadium pentoxide and citric acid monohydrate in this invention;

[0031] Figure 2 This is a diagram showing the state of the medicinal tablets in the graphite boat assembled in the heating chamber according to the present invention;

[0032] Figure 3 These are the XRD patterns of pure-phase V2O3 synthesized under argon atmospheres of 3 atm, 5 atm, and 10 atm in this invention.

[0033] Figure 4 This is the XRD pattern of V2O3 containing VO2 impurity phase synthesized under vacuum, 1 atm, and 2 atm argon atmosphere in this invention;

[0034] Figure 5 This is a SEM image of pure-phase V2O3 synthesized under 3 atm conditions in this invention;

[0035] Figure 6 This is a SEM image of V2O3 containing VO2 impurity phase synthesized under vacuum conditions in this invention;

[0036] Figure 7 This is a comparison chart of the charge / discharge specific capacity and charge / discharge efficiency of vanadium trioxide materials obtained in the embodiments and comparative examples of the present invention when applied as cathode materials for zinc-ion batteries. Detailed Implementation

[0037] The technical effects of the present invention are further illustrated below through specific embodiments and comparative examples, but the scope of protection of the present invention is not limited to these embodiments.

[0038] Example 1

[0039] A method for preparing a pure-phase vanadium trioxide material includes the following steps:

[0040] 1. Raw material preparation: Weigh 1.82g of vanadium pentoxide (V2O5) and 2.10g of citric acid monohydrate (C6H8O7·H2O) in a molar ratio of 1:1. Mix the two together in an agate mortar and grind for 40 minutes until a homogeneous mixture is obtained.

[0041] 2. Tableting process: Accurately weigh 0.5g of the above mixture and compress it into round tablets with a diameter of 10mm using a tablet press at a pressure of 10MPa (e.g., ...). Figure 1 ).

[0042] 3. Equipment Preparation: Place the tablet in a conductive graphite boat, then install the conductive graphite boat into the heating chamber of the Joule heating device (e.g., Figure 2 After sealing, perform three cycles of vacuuming and argon filling to ensure that all air is completely removed.

[0043] 4. Flash burning process: Adjust the argon atmosphere pressure in the Joule heating device to 3 atm, and input the heating parameters: 800℃, 40V voltage, 220A current, and flash burning time of 60 seconds.

[0044] 5. Product collection: After flash calcination, cool to room temperature and collect the black, fluffy pure vanadium trioxide (V2O3) product.

[0045] Product characterization: such as Figure 3 As shown, X-ray diffraction (XRD) analysis revealed that the product was pure vanadium trioxide, with no VO2 impurities present. Figure 5 Scanning electron microscopy (SEM) observation showed that the product has a rice-grain-like porous and fluffy structure, which is conducive to electrolyte wetting and is suitable for battery applications.

[0046] Example 2

[0047] A method for preparing a pure-phase vanadium trioxide material includes the following steps:

[0048] 1. Raw material preparation: Weigh 1.82g of vanadium pentoxide (V2O5) and 2.10g of citric acid monohydrate (C6H8O7·H2O) in a molar ratio of 1:1. Mix the two together in an agate mortar and grind for 40 minutes until a homogeneous mixture is obtained.

[0049] 2. Tableting process: Accurately weigh 0.5g of the above mixture and compress it into round tablets with a diameter of 10mm using a tablet press at a pressure of 10MPa (e.g., ...). Figure 1 ).

[0050] 3. Equipment Preparation: Place the tablet in a conductive graphite boat, then install the conductive graphite boat into the heating chamber of the Joule heating device (e.g., Figure 2 After sealing, perform three cycles of vacuuming and argon filling to ensure that all air is completely removed.

[0051] 4. Flash burn treatment: Adjust the argon atmosphere pressure in the Joule heating device to 5 atm, and input the heating parameters: 800℃, 40V voltage, 220A current, and flash burn time of 60 seconds.

[0052] 5. Product collection: After flash calcination, cool to room temperature and collect the black, fluffy pure vanadium trioxide (V2O3) product.

[0053] Product characterization: such as Figure 3 As shown, X-ray diffraction (XRD) analysis revealed that the product was pure vanadium trioxide with no VO2 impurity phase present.

[0054] Example 3

[0055] A method for preparing a pure-phase vanadium trioxide material includes the following steps:

[0056] 1. Raw material preparation: Weigh 1.82g of vanadium pentoxide (V2O5) and 2.10g of citric acid monohydrate (C6H8O7·H2O) in a molar ratio of 1:1. Mix the two together in an agate mortar and grind for 40 minutes until a homogeneous mixture is obtained.

[0057] 2. Tableting process: Accurately weigh 0.5g of the above mixture and compress it into round tablets with a diameter of 10mm using a tablet press at a pressure of 10MPa (e.g., ...). Figure 1 ).

[0058] 3. Equipment Preparation: Place the tablet in a conductive graphite boat, then install the conductive graphite boat into the heating chamber of the Joule heating device (e.g., Figure 2 After sealing, perform three cycles of vacuuming and argon filling to ensure that all air is completely removed.

[0059] 4. Flash burn treatment: Adjust the argon atmosphere pressure in the Joule heating device to 10 atm, and input the heating parameters: 800℃, 40V voltage, 220A current, and flash burn time of 30 seconds.

[0060] 5. Product collection: After flash calcination, cool to room temperature and collect the black, fluffy pure vanadium trioxide (V2O3) product.

[0061] Product characterization: such as Figure 3 As shown, X-ray diffraction (XRD) analysis revealed that the product was pure vanadium trioxide with no VO2 impurity phase present.

[0062] Comparative Example 1 (Flash treatment under vacuum conditions)

[0063] The operation steps of this comparative example, including raw material ratio, tableting process and heating parameters, are basically the same as those in Example 1. The difference is that the system is kept in a vacuum state (0.01 atm) during the flash burning process.

[0064] Characterization analysis: such as Figure 4 As shown, XRD analysis of the product revealed obvious diffraction peaks of the VO2 impurity phase in addition to the V2O3 main phase, indicating that complete purification could not be achieved under vacuum conditions. Figure 6 Observation using scanning electron microscopy (SEM) and combined with Figure 5 It can be seen that rice-grain-shaped V2O3 adheres to the surface of blocky VO2.

[0065] Comparative Example 2 (Flash treatment under 1 atm atmosphere pressure)

[0066] The operating steps and conditions of this comparative example are basically the same as those of Example 1, except that the flash burning process is carried out under a 1 atm argon atmosphere.

[0067] Characterization analysis: such as Figure 4 As shown, XRD analysis indicates that the product still contains a small amount of VO2 impurity phase, and pure phase V2O3 cannot be obtained, proving that atmospheric pressure conditions are insufficient to completely eliminate impurity phases.

[0068] Comparative Example 3 (Flash treatment under 2 atm atmosphere pressure)

[0069] The operating steps and conditions of this comparative example are basically the same as those of Example 1, except that the flash burning process is carried out under a 2 atm argon atmosphere.

[0070] Characterization analysis: such as Figure 4 As shown, XRD analysis revealed that trace amounts of VO2 impurities remained in the product, indicating that complete purification could not be achieved. This suggests that a pressure of 2 atm was insufficient to completely eliminate the impurities.

[0071] Table 1. Phase composition analysis of products from the Examples and Comparative Examples under different pressure conditions.

[0072]

[0073] The above examples and comparative examples fully demonstrate that atmospheric pressure is a key factor affecting the purity of vanadium trioxide. When the pressure is below 3 atm, varying degrees of VO2 impurities will be present in the product; while when the pressure reaches 3 atm or above, pure V2O3 can be obtained. This discovery provides a new technical approach for the preparation of single-phase vanadium trioxide.

[0074] The pure-phase vanadium trioxide prepared according to this invention was used as the positive electrode material for an aqueous zinc-ion battery. The electrochemical test results are as follows: at 2A g... -1 At current density, the initial charge specific capacity is 267 mAh g. -1 The 100th cycle yielded 286 mAh g. -1 It still maintains 198 mAh g after 800 cycles.-1 Compared with the comparative example, the pure-phase vanadium trioxide obtained in this invention has a higher charge-discharge specific capacity at a similar coulombic efficiency.

[0075] The above demonstrates that the pure-phase vanadium trioxide prepared by this invention can be widely used in the field of electrochemical energy storage, especially as a cathode material for aqueous zinc-ion batteries. Its unique fluffy porous structure is beneficial for electrolyte wetting and ion transport, thereby improving the overall performance of the battery.

[0076] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made based on the content of the present invention specification, or direct / indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a pure-phase vanadium trioxide material, characterized in that, Includes the following steps: (1) Raw material mixing: Vanadium pentoxide and citric acid monohydrate are mixed in a certain proportion and ground evenly to obtain a mixture powder; (2) Tableting: Accurately weigh an appropriate amount of the above mixture powder and compress it into round tablets; (3) Equipment assembly and vacuuming: Place the tablets in a conductive graphite boat, then place the conductive graphite boat in the heating chamber of the heating equipment. After assembly, seal it and perform vacuuming-gas filling cycle treatment. (4) Flash burning treatment: Under argon / nitrogen atmospheres of different pressures, input fixed heat treatment parameters and flash burn for 10-60s under certain conditions; (5) Product collection: After flash burning, cool to room temperature and collect the black, fluffy pure vanadium trioxide product.

2. The method for preparing pure-phase vanadium trioxide material according to claim 1, characterized in that, The molar ratio of vanadium pentoxide to citric acid monohydrate in step (1) is 1:1 to 1:1.

2.

3. The method for preparing pure-phase vanadium trioxide material according to claim 1, characterized in that, The grinding time in step (1) is 20-40 minutes.

4. The method for preparing pure-phase vanadium trioxide material according to claim 1, characterized in that, The mass of the mixed powder weighed in step (2) is 0.3-0.8g.

5. The method for preparing pure-phase vanadium trioxide material according to claim 1, characterized in that, The pressing in step (2) is performed using a tablet press at a pressure of 10 MPa.

6. The method for preparing pure-phase vanadium trioxide material according to claim 1, characterized in that, The vacuuming-gas-filling cycle in step (3) is repeated 3 times.

7. The method for preparing pure-phase vanadium trioxide material according to claim 1, characterized in that, The heat treatment parameters in step (4) are: heating temperature 800℃, voltage 40V, and current 220A.

8. The method for preparing pure-phase vanadium trioxide material according to claim 1, characterized in that, The pressure of the argon / nitrogen gas in step (4) is 3 atm-10 atm.

9. A pure-phase vanadium trioxide material obtained by the preparation method according to any one of claims 1-8.

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