A vanadium-based material and its preparation method and application

Abstract

The present invention discloses a vanadium-based material, a preparation method and an application thereof, and belongs to the field of new material technology. The preparation method of the vanadium-based material provided by the present invention comprises the following steps: vanadium pentoxide and a solution containing organic matter are separated and placed in the same closed container, and subjected to a heating reaction; wherein the organic matter comprises at least one of ethanol, acetaldehyde, acetone, ethylenediamine, aniline and thiourea; and the temperature of the heating reaction is ≥120°C. The preparation method provided by the present invention has the advantages of being simple and easy to implement, low in cost, high in efficiency and environmentally friendly. When the prepared vanadium-based material is used as a positive electrode material for a zinc ion battery, it can effectively improve the cycle performance of the zinc ion battery. The present invention also provides a vanadium-based material prepared by the above-mentioned preparation method and the application of the corresponding vanadium-based material.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a vanadium-based material and a preparation method and application thereof. Background Art

[0002] With the advancement of science and technology and humanity's pursuit of a more comfortable living environment, the market demand for sustainable energy storage devices is becoming increasingly strong. Aqueous zinc-ion batteries, due to their low cost, high safety, and environmental friendliness, are considered a potential alternative battery technology for sustainable energy storage. However, the practical application of aqueous zinc-ion batteries remains challenging due to the poor rate performance, low cycling stability, and limited capacity of their cathode materials. Therefore, it is of great significance to develop cathode materials with stable and fast ion transport channels to ensure their ideal rate performance and stability during long-term cycling.

[0003] Vanadium oxides have multivalence and an open and tunable layered crystal structure, which is beneficial for Zn 2+ However, these vanadium oxides also have structural instability, slow ion diffusion kinetics, and poor compatibility with Zn 2+ Strong electrostatic interaction leads to poor cycle performance and rate performance. Many improvement strategies have been developed to address the above problems, such as defect engineering and the integration of water molecules (H2O), cations (such as Na + 、Mn 2+ 、Al 3+ NH4 + Small molecules such as , etc.) or polymers (PANI, EDA, and PEDOT) are inserted into the [VOn] interlayer to effectively shield Zn 2+ The electrostatic interaction with the matrix skeleton expands the interlayer spacing and enables rapid ion diffusion.

[0004] Currently, the insertion of intercalated small molecules is mainly prepared by the traditional liquid-phase hydrothermal method, but this method has obvious shortcomings. All reactions must be carried out in the bulk solution, and the target structure will only be formed when the solute concentration in the reaction medium reaches saturation. This process is largely controlled by the diffusion of substances, resulting in long reaction times (12h to 48h), cumbersome operations, low yields, high energy consumption, and the solution after the reaction cannot be recycled and reused, which easily leads to waste of resources and increased costs. Most importantly, the electrochemical performance of intercalated vanadium oxides prepared by traditional methods is still not ideal.

[0005] Therefore, it is crucial to develop a fast, efficient, and green preparation method for high-performance small-molecule intercalated vanadium oxides. Summary of the Invention

[0006] The present invention aims to address at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing a vanadium-based material, which has the advantages of being simple, cost-effective, efficient, and environmentally friendly. The prepared vanadium-based material, when used as a positive electrode material for zinc-ion batteries, can effectively improve the cycling performance of zinc-ion batteries.

[0007] The present invention also provides a vanadium-based material prepared by the above preparation method.

[0008] The present invention also provides applications of the vanadium-based material.

[0009] According to an embodiment of the first aspect of the present invention, a method for preparing a vanadium-based material is provided, the method comprising the following steps:

[0010] The vanadium pentoxide and the solution containing organic matter are separated and placed in the same closed container, and heated to react;

[0011] The temperature of the heating reaction is ≥120°C;

[0012] The organic matter includes at least one of ethanol, acetaldehyde, acetone, ethylenediamine, aniline and thiourea;

[0013] When the organic matter is selected from at least one of ethanol, acetaldehyde, acetone, ethylenediamine and aniline, the volume percentage of the organic matter in the solution is greater than 50%;

[0014] When the organic matter is selected from thiourea, the concentration of the organic matter in the solution is ≥1 mM.

[0015] The reaction mechanism of the preparation method is as follows:

[0016] In the preparation method, the heating reaction creates a special gas phase reaction environment for the solution. The reducing and volatile organic vapor uses its own reducing properties to drive the crystal structure transformation of vanadium pentoxide. At the same time, under the high pressure of the steam, small molecules (including the organic matter) are inserted into the interlayer of the main structure of the material along with the transformation of the vanadium oxide structure, which can effectively shield the Zn 2+ It interacts electrostatically with the material skeleton and acts as an interlayer pillar to stabilize the structure, forming a small molecule intercalated vanadium oxide with rich electrochemical active surface area and excellent electrochemical activity.

[0017] The preparation method according to the embodiment of the present invention has at least the following beneficial effects:

[0018] (1) In the preparation method provided by the present invention, the vanadium pentoxide does not come into contact with the solution, and the conversion reaction is directly carried out by high-temperature steam, which greatly improves the reaction rate; and the solution does not need to soak the solid vanadium pentoxide. Therefore, the preparation method provided by the present invention is not limited by the solid-liquid ratio, which can save the amount of solution chemicals and improve the batch output (preparation efficiency) of vanadium-based materials.

[0019] (2) The preparation method provided by the present invention does not require complicated pretreatment steps or solid-liquid separation steps because there is no contact between the solid and the liquid. The solution after the reaction can be recycled and reused. The operation is simple and easy, and the production cost is low. It effectively solves the problems of complicated operation steps, long reaction time, low preparation efficiency, high energy consumption, and high cost in the traditional liquid phase hydrothermal method.

[0020] According to some embodiments of the present invention, the separation method includes suspending the vanadium pentoxide above a liquid surface formed by the solution.

[0021] (3) In the preparation method provided by the present invention, the proportion of the organic matter in the solution is determined by the type of organic matter, specifically related to parameters such as the reducibility, volatility, and vapor pressure of the organic matter. The present invention has found that when the organic matter is selected from at least one of ethanol, acetaldehyde, acetone, ethylenediamine, and aniline, the volume percentage of the organic matter in the solution is greater than 50%; when the organic matter is selected from thiourea, the concentration of the organic matter in the solution is ≥1 mM. In this manner, a small molecule intercalated vanadium oxide with excellent electrochemical activity can be prepared.

[0022] According to some embodiments of the present invention, the suspending method includes placing the vanadium pentoxide in a beaker and then suspending the beaker in a sealed container.

[0023] According to some embodiments of the present invention, the beaker is made of polytetrafluoroethylene.

[0024] According to some embodiments of the present invention, the sealed container includes a high-pressure reactor.

[0025] The inner container of the high-pressure reactor is made of at least one of polytetrafluoroethylene and stainless steel.

[0026] According to some embodiments of the present invention, when the organic matter is selected from at least one of ethanol, acetaldehyde, acetone, ethylenediamine and aniline, the volume percentage of the organic matter in the solution is 75-100%.

[0027] The specific concentration ratios described above also depend on the type of the organic matter. For example, when the organic matter is selected from at least one of ethanol, acetaldehyde, and acetone, the volume percentage of the organic matter in the solution is greater than 50%, for example, approximately 80%. According to some embodiments of the present invention, when the organic matter is selected from at least one of ethylenediamine and aniline, the volume percentage of the organic matter in the solution is between 75% and 100%, for example, approximately 100%.

[0028] According to some embodiments of the present invention, the proportion of the organic matter in the solution can be adjusted according to the type of the organic matter in actual production. When the organic matter is selected from thiourea, the concentration of the organic matter in the solution can be 5mM, 10mM or above.

[0029] According to some embodiments of the present invention, the solution further comprises water, that is, the solution is a mixture of water and the organic matter.

[0030] According to some embodiments of the present invention, the solution is the organic matter, that is, except for the organic matter, water is not included.

[0031] According to some embodiments of the present invention, the solution is one of the following combinations: a mixture of ethanol and water, a mixture of thiourea and water, pure ethylenediamine, and pure aniline.

[0032] According to some embodiments of the present invention, the solid-to-liquid ratio of the vanadium pentoxide to the solution is 5g:1-5ml.

[0033] According to some embodiments of the present invention, the heating reaction lasts for 1 hour to 8 hours.

[0034] According to some embodiments of the present invention, the heating reaction time is 3 to 8 hours, for example, about 6 hours.

[0035] According to some embodiments of the present invention, the temperature of the heating reaction is ≤240°C.

[0036] According to some embodiments of the present invention, the temperature of the heating reaction is 150-240°C, for example, specifically about 180°C or 200°C.

[0037] According to some embodiments of the present invention, the preparation method includes cooling and drying the obtained solid material after the heating reaction.

[0038] According to some embodiments of the present invention, the drying temperature is 60-100°C, for example, specifically about 80°C.

[0039] According to an embodiment of the second aspect of the present invention, a vanadium-based material prepared by the preparation method is provided.

[0040] Since the vanadium-based material adopts all the technical solutions of the preparation method of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment.

[0041] The vanadium-based material has abundant electrochemically active surface area and larger interlayer spacing than ordinary vanadium oxide, which can shield Zn 2+ The electrostatic interaction between the nanostructured ZnO and the matrix skeleton leads to excellent electrochemical performance in aqueous Zn-ion batteries.

[0042] According to some embodiments of the present invention, the vanadium-based material is a small molecule intercalated vanadium oxide;

[0043] The small molecule includes at least one of H2O, NH3, ethylenediamine and aniline.

[0044] The valence state of vanadium in the vanadium oxide is at least one of +4 and +5.

[0045] According to an embodiment of the third aspect of the present invention, there is provided a use of the vanadium-based material in preparing a secondary battery.

[0046] Since the application adopts all the technical solutions of the vanadium-based materials of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment. In the specific application, the cycle performance and capacity of the secondary battery are both very excellent.

[0047] According to some embodiments of the present invention, the secondary battery comprises a zinc ion battery.

[0048] According to some embodiments of the present invention, the zinc ion battery includes a positive electrode, a negative electrode, an electrolyte and a separator.

[0049] According to some embodiments of the present invention, the positive electrode includes a current collector and a positive electrode coating;

[0050] The positive electrode current collector comprises at least one of a stainless steel mesh and a carbon paper;

[0051] The positive electrode coating is formed by coating the positive electrode slurry on the positive electrode current collector and then drying it;

[0052] The positive electrode slurry comprises a mixture of the vanadium-based material, a conductive agent, a binder and N-methylpyrrolidone (NMP); the conductive agent comprises at least one of acetylene black, Super P and carbon black; and the binder comprises polyvinylidene fluoride (PVDF).

[0053] The mass ratio of the vanadium-based material, the conductive agent and the binder is 7:2:1.

[0054] The negative electrode is a zinc sheet; the thickness of the zinc sheet is about 300 μm; the purity of zinc in the zinc sheet is ≥99.9%.

[0055] According to some embodiments of the present invention, the electrolyte is a 2 mol / L Zn(CF3SO3)2 solution.

[0056] Unless otherwise specified, the term “about” in the present invention actually means that the error is allowed to be within the range of ±2%, for example, about 100 actually means 100±2%×100.

[0057] Unless otherwise specified, “between” in the present invention includes the number itself, for example, “between 2 and 3” includes the endpoint values ​​2 and 3.

[0058] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0060] Figure 1 The XRD pattern of the product prepared in Comparative Example 4 of the present invention is shown below:

[0061] Figure 2 This is a scanning electron microscope image of the product prepared in Comparative Example 4 of the present invention;

[0062] Figure 3 is a transmission electron microscope image of the product prepared in Comparative Example 4 of the present invention;

[0063] Figure 4 This is a cycle performance diagram of the product prepared in Comparative Example 4 of the present invention;

[0064] Figure 5 The XRD pattern of the water molecule intercalated vanadium oxide prepared in Example 1 of the present invention;

[0065] Figure 6 The scanning electron microscope image and transmission electron microscope image of the water molecule intercalated vanadium oxide prepared in Example 1 of the present invention;

[0066] Figure 7 This is a cycling performance diagram of the water molecule intercalated vanadium oxide prepared in Example 1 of the present invention;

[0067] Figure 8 The XRD pattern of the product prepared in Example 2 of the present invention;

[0068] Figure 9 This is the Raman spectrum of the product prepared in Comparative Example 1 of the present invention;

[0069] Figure 10 The XRD pattern of the product prepared in Comparative Example 2 of the present invention is shown below:

[0070] Figure 11 The XRD pattern of the NH3 molecule intercalated vanadium oxide prepared in Example 3 of the present invention;

[0071] Figure 12 This is a cycle performance diagram of NH3 molecule intercalated vanadium oxide prepared in Example 3 of the present invention;

[0072] Figure 13 This is the FTIR spectrum of the ethylenediamine molecule intercalated vanadium oxide prepared in Example 4 of the present invention;

[0073] Figure 14 This is the FTIR spectrum of the aniline molecule intercalated vanadium oxide prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0074] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0075] Example 1

[0076] This embodiment prepares a vanadium-based material, and the specific steps are as follows:

[0077] S1. A polytetrafluoroethylene beaker containing 5 g of vanadium pentoxide was suspended in a hydrothermal reactor containing 1 ml of a mixture of ethanol and water (4:1 by volume). The reactor was sealed.

[0078] S2. The system obtained in step S1 was heated to 200°C and kept at this temperature for 3h for high temperature reaction;

[0079] S3. After the reaction is completed, the mixture is cooled to room temperature, the product in the beaker is taken out, and vacuum dried at 80°C to obtain a vanadium-based material, specifically water molecule intercalated vanadium oxide.

[0080] Examples 2 to 5 and Comparative Examples 1 to 3 respectively prepared a vanadium-based material. The steps of Examples 2 to 5 and Comparative Examples 1 to 3 differ from those of Example 1 in that some parameters are different. The key parameters of specific Examples 1 to 5 and Comparative Examples 1 to 3 are listed in Table 1.

[0081] Table 1 Key parameters of Examples 1 to 5 and Comparative Examples 1 to 3

[0082]

[0083]

[0084] In Table 1, the composition ratios of the solutions are by volume. The “ / ” in the product type indicates that no intercalation layer was formed.

[0085] Comparative Example 4

[0086] This comparative example prepared a vanadium-based material, and the specific steps were:

[0087] D1. Mix 5g of commercial vanadium pentoxide with 1ml of a mixture of ethanol and water (4:1 by volume), stir well, and pour into a polytetrafluoroethylene liner of a high-pressure reactor. Seal the reactor.

[0088] D2 heating step D1 obtained system to 200 ℃ and heat for 3h hydrothermal reaction;

[0089] D3. After the reaction is completed, cool to room temperature, filter and separate, wash the filter cake with ethanol and deionized water in sequence, and dry in vacuo at 80°C to obtain the product.

[0090] Test Case

[0091] In the first aspect of this test example, the appearance of the obtained product was observed visually, and the type of the vanadium-based material obtained in each example and comparative example was determined using at least one of XRD, Raman, and Fourier transform infrared (FTIR) spectra. The test results showed:

[0092] The vanadium-based material obtained in Example 1 contains V in mixed valence states. 10 O 24 ·12H2O phase, which shows that the vanadium pentoxide crystal structure is driven by the pressure of high-temperature steam (mixed steam formed by ethanol and water) to transform into V 4+ and V 5+ Mixed valence defect structure. At the same time, water molecules are inserted into the interlayer spacing of the main structure in conjunction with the structural transformation, and finally form intercalation defect hydrated vanadium oxide with interlayer crystallization water. At the same time, due to V 4+ and V 5+ Mixed-valence defect structures can cause dislocation and disorder in the lattice fringes, resulting in weaker crystallinity. The more such defect structures there are, the worse the crystallinity. Furthermore, the intercalation of water molecules loosens the main structure, resulting in poorer crystallinity. Therefore, the crystallinity of the product obtained in Example 1 is inferior to that of Comparative Example 4. A comparison of Example 1 and Comparative Example 1 shows that when the organic compound is ethanol, a crystal transformation and water intercalation can be achieved when the ethanol concentration reaches 75%.

[0093] The type and crystallization condition of the vanadium-based material obtained in Example 2 are similar to those in Example 1, both of which are water molecule intercalated vanadium oxides. This shows that within the temperature range provided by the present invention, the target vanadium-based material can also be obtained by appropriately lowering the temperature, but the reaction time needs to be extended accordingly, for example, if the temperature is lowered by 10°C, the reaction time is extended by 1 hour.

[0094] The test results of the appearance and type of vanadium-based materials are as follows Figure 1 、 Figure 5 、 Figure 8 、 Figure 9 、 Figure 10 、 Figure 11 、 13 , as shown in 14.

[0095] This test example also tested the morphology of the vanadium-based materials obtained in the specific implementation method. The test results showed that the morphology of the vanadium-based material obtained in Example 1 was a nano-sheet structure. The morphology of the vanadium-based materials obtained in Comparative Examples 1 to 3 was the same as that of the vanadium pentoxide used, and the microscopic morphology was a layered block. The morphology of the vanadium-based material obtained in Comparative Example 4 showed a nano-belt structure. According to the mass-thickness contrast, its thickness was significantly thicker than that of the vanadium-based material obtained in Example 1. The morphology test results of the specific implementation method are shown in FIG. Figure 2 、 3 and 6.

[0096] This test example also tested the performance of the vanadium-based materials obtained in Example 1, Example 3 and Comparative Example 4 as positive electrode materials for aqueous zinc ion batteries, specifically:

[0097] The vanadium-based material obtained in Examples 1, 3, and Comparative Example 4, acetylene black (conductive agent), and polyvinylidene fluoride (PVDF, binder) were thoroughly mixed and ground at a mass ratio of 7:2:1. N-methylpyrrolidone (NMP) solvent was then added dropwise to form a slurry. The slurry was then coated onto a stainless steel mesh to form a positive electrode. A zinc sheet with a purity of ≥99.9% and a thickness of 300 μm was used as the negative electrode, and a glass fiber separator was placed between the positive and negative electrodes. The resulting aqueous zinc ion button cells were assembled to test their cycling performance. A 2 mol / L aqueous Zn(CF3SO3)2 electrolyte was used.

[0098] The above aqueous zinc ion battery was subjected to a cycle test. The results showed that the vanadium-based material obtained in Example 1 still maintained a capacity of 245.2 mAh·g after 2000 cycles. -1 The specific capacity of the vanadium-based material obtained in Comparative Example 4 was low (about 115 mAh g) after 2000 cycles. -1) and decays quickly. The initial activation process is slow, and it takes about 80 cycles before it is activated to the highest capacity. The vanadium-based material obtained in Example 3 has a high specific capacity of 350.9 mAh·g -1 , and after 50 cycles, the capacity decay is weak and the cycle stability is good. The test results of electrochemical performance are as follows Figure 4 、 7 and 12.

[0099] According to the above analysis, it can be seen that the preparation method provided by the present invention breaks the solid-liquid ratio limitation of traditional hydrothermal method (Example 1 and Comparative Example 4), simplifies the process procedure, and shortens the reaction time by nearly two-thirds, greatly improving the preparation efficiency; and the vanadium-based material prepared by the present invention has a rich electrochemically active surface area and exhibits more excellent electrochemical performance. And if a vanadium-based material with corresponding reaction activity is to be prepared, it is necessary to be within the temperature range provided by the present invention. If the temperature is lower than 120°C, it is difficult to drive the crystal transformation and intercalation of vanadium pentoxide (Examples 1-2 and Comparative Example 3); In addition, the preparation of vanadium-based materials also requires ensuring the presence of organic matter (reducing property) in the solution, otherwise the crystal transformation and intercalation cannot be achieved (Example 1 and Comparative Examples 1-2). It should also be emphasized that the small molecules that can form intercalation are not only water, but can also be at least one of ammonia (and its cations), aniline, and ethylenediamine. And various small molecule intercalated vanadium-based materials can obtain excellent electrochemical properties.

[0100] In summary, the present invention uses the high-pressure driving crystal structure transformation of reducing organic vapor generated in a high-temperature gas phase environment, and synergistically induces small molecules to be inserted into the interlayer of the material body to form a vanadium oxide (vanadium-based material) with small molecule intercalation. This small molecule intercalation vanadium oxide has a rich electrochemically active surface area, which allows more electrons to contribute to the delocalized electron cloud, promotes interfacial electron transfer, and exhibits more excellent electrochemical performance in aqueous zinc ion batteries. The preparation method of the present invention effectively solves the problems of the traditional liquid phase hydrothermal method, such as long reaction time, high energy consumption, low preparation efficiency, cumbersome steps, large consumption of pharmaceutical reagents, and high cost, and realizes a fast, efficient, and green preparation method for small molecule intercalation vanadium oxide.

[0101] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for preparing a vanadium-based material, characterized in that: The preparation method comprises the following steps: The vanadium pentoxide and the solution containing organic matter are separated and placed in the same closed container, and heated to react; The heating reaction temperature is 120-240° C. and the duration is 1-8 hours; The solution is a mixture of ethanol and water, wherein the volume percentage of ethanol is greater than 50% and less than or equal to 80%.

2. The preparation method according to claim 1, characterized in that The solid-liquid ratio of the vanadium pentoxide to the solution is 5g:1-5ml.

3. The preparation method according to any one of claims 1 to 2, characterized in that The separation setting method includes suspending the vanadium pentoxide above the liquid surface formed by the solution.

4. A vanadium-based material obtained by the preparation method according to any one of claims 1 to 3.

5. Use of the vanadium-based material according to claim 4 in preparing a secondary battery.

6. The use according to claim 5, characterized in that The secondary battery includes a zinc ion battery.

Images