A high oxygen vacancy titanate nanomaterial and preparation method thereof

Abstract

The present invention discloses a high oxygen vacancy titanate nanomaterial and a preparation method thereof, which belongs to the technical field of nanomaterial preparation. Titanium silicon carbide is mixed with an alkaline solution containing potassium fluoride, and oxygen is continuously introduced while heating in an oil bath to obtain a high oxygen vacancy titanate nanomaterial. The high oxygen vacancy content gives the material more potassium storage sites, effectively improving the diffusion rate and storage capacity of potassium ions. In addition, the increase in the lamellar tissue distance in the structure allows potassium ions to shuttle more freely between nanolayers, greatly enhancing the electrochemical properties of the material. This excellent lamellar structure also provides more channels for electron conduction, effectively promoting the rapid transfer of electrons inside and outside the active particles, thereby further improving the rate performance of the electrode material. The high oxygen vacancy titanate nanomaterial has broad application prospects in the fields of sustainable energy, energy storage devices, and electric vehicles.

Description

Technical Field

[0001] The invention belongs to the technical field of nano material preparation, and particularly relates to a high oxygen vacancy titanate nano material and a preparation method thereof. Background Art

[0002] The energy shortages and environmental pollution caused by the widespread use of fossil fuels have seriously impacted the sustainable development of human society. The development of efficient new energy sources has received significant global attention in recent years. Traditional renewable energy sources, such as wind, hydro, solar, and geothermal energy, are often subject to time and space constraints, resulting in low energy efficiency. To improve the efficiency of renewable energy, it is crucial to develop energy storage devices that are energy-dense, safe, and cost-effective.

[0003] Batteries and supercapacitors are two high-performance energy storage technologies that have made great progress. Among them, lithium-ion batteries (LIBs) are widely used in electronic products due to their high energy density (reaching 180Wh / kg). However, due to the scarcity of lithium on the earth and its uneven geographical distribution, lithium-ion batteries cannot meet the needs of industrial-scale electrochemical energy storage systems. In addition, the slow transmission of electrons and ions leads to increased resistance, and high-power operation may cause dendrite formation, which impairs battery safety. In comparison, supercapacitors have the advantages of high power density, fast charging, and extremely long cycle life (more than 100,000 cycles), and can partially or even completely replace batteries in some scenarios.

[0004] To date, breakthroughs have been made in the research of supercapacitor cathode materials. On this basis, constructing high-performance anodes is undoubtedly an important way to further improve the energy density of asymmetric supercapacitors (ASCs). The operating voltage range of the anode materials of aqueous ASCs mainly depends on their redox potential and hydrogen evolution overpotential. Titanium-based electrodes with high hydrogen evolution overpotential, excellent chemical / electrochemical stability, non-toxicity, low cost and high natural abundance have broad application prospects in the field of high-pressure aqueous ASCs. However, the inherent low electronic / ionic conductivity of titanium-based electrodes will limit their practical application. Therefore, optimizing the conductivity and ion transport channels of titanium-based electrodes is crucial to improving the energy density of high-pressure aqueous ASCs.

[0005] At present, the titanium-based materials commonly used in the negative electrode of aqueous ASCs are mainly TiO2, and titanium-based materials similar to K2Ti2O5 are rarely reported. K2Ti2O5 belongs to the monoclinic crystal system, and is composed of TiO5 trigonal bipyramids connected by common vertices to form a chain layered structure, with K2Ti2O5 between the layers. + Occupies, the interlayer spacing is approximately The layers are parallel to the crystal axes, and they have fast and large-scale ion transport capabilities and low operating voltage characteristics, making them promising for use in the field of anodes for aqueous ASCs. However, K2Ti2O5-based materials also have corresponding shortcomings, including slow potassium ion kinetics embedded in the main body and insufficient electron transfer capacity between active particles. These problems result in relatively insufficient electrochemical active sites, low specific capacitance, poor conductivity, and rapid degradation of electrochemical performance during cycling. Therefore, it is necessary to explore new preparation methods to improve the conductivity of K2Ti2O5-based titanium-based materials and introduce more oxygen vacancies so that they can be used more efficiently as anode materials for ASCs. This will expand the application prospects of supercapacitors / batteries prepared based on these materials in fields such as sustainable energy, energy storage devices, and electric vehicles, providing stronger support for the development of sustainable energy technologies.

[0006] At present, there are many methods for introducing oxygen vacancies in materials, such as heat treatment, hydrogen reduction, flame reduction, electrochemical reduction and plasma treatment under conditions of insufficient oxygen. The heat treatment method usually needs to be carried out in a high-temperature and high-pressure reactor. For example, Chinese patent CN 108722384 B discloses a kind of oxygen-vacancy-rich titanium dioxide nanoflower and its preparation method, which introduces oxygen vacancies into titanium dioxide nanoflowers by a solvent thermal method. Although this method has the characteristics of high product purity, the operating conditions are complex and not easy to control. The hydrogen reduction method has very high requirements for hydrogen. If the purity of hydrogen is impure, it is easy to explode, there are hidden dangers, and the storage and transportation of hydrogen are also problematic. Flame reduction and electrochemical methods have very high requirements for operation, and temperature, current and voltage must be controlled at all times. The plasma treatment method requires high-energy particle bombardment. The generation of high-energy particles usually requires a high breakdown voltage, and the operating conditions are complex and not easy to achieve.

[0007] Therefore, it is necessary to further explore the method of introducing oxygen vacancies in materials, further simplify the processing conditions and process flow based on the existing scheme, and further reduce the energy and resource consumption in the production process. Summary of the Invention

[0008] The present invention aims to provide a high-oxygen-vacancy titanate nanomaterial and its preparation method. The high oxygen vacancy content provides the material with more potassium storage sites, effectively increasing the diffusion rate and storage capacity of potassium ions. Furthermore, the layered structure allows potassium ions to move more freely between the nanolayers, significantly enhancing the material's electrochemical performance.

[0009] The technical solution of the present invention is: a method for preparing a high oxygen vacancy titanate nanomaterial, comprising the following steps:

[0010] 1) preparing an aqueous solution of a strong base, and adding potassium fluoride dihydrate to the aqueous solution of the strong base;

[0011] 2) adding titanium silicon carbide (Ti3SiC2) powder to the solution prepared in step 1);

[0012] 3) heating the mixed solution obtained in step 2) in an oil bath, stirring while heating, and continuously introducing oxygen into the mixed solution during the heating process;

[0013] 4) Repeat centrifugation and washing to obtain an upper emulsion, collect the emulsion and centrifuge it, collect the solid, and wash it to obtain a high oxygen vacancy titanate nanomaterial.

[0014] Furthermore, in step 1), the strong base is any one of potassium hydroxide and sodium hydroxide.

[0015] Furthermore, in step 1), the mass ratio of the strong base, potassium fluoride dihydrate and water is 1:0.5-1.5:1-2.

[0016] Furthermore, in step 2), the mass ratio of titanium silicon carbide to strong base is 1:40-50.

[0017] Furthermore, in step 3), the oil bath heating temperature is 80-90° C., and the heating time is 7-12 days.

[0018] Furthermore, in step 3), the flow rate of oxygen is 1 to 5 L / min.

[0019] Furthermore, in step 3), the stirring speed is 300-500 rpm.

[0020] Based on the above method, titanate nanomaterials with high oxygen vacancy characteristics can be prepared. The high oxygen vacancy content gives the material more potassium storage sites, effectively improving the diffusion rate and storage capacity of potassium ions.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. This application uses a wet chemical method to prepare high-oxygen-vacancy potassium titanate nanomaterials. The high oxygen vacancy content gives the material more potassium storage sites, thereby effectively improving the diffusion rate and storage capacity of potassium ions, solving the problem of slow potassium ion kinetics in conventional potassium titanate materials;

[0023] 2. The layered structure of the potassium titanate nanomaterial prepared in this application enables potassium ions to shuttle more freely between the nanolayers, greatly enhancing the electrochemical performance of the material. The layered structure also provides more channels for electron conduction, effectively promoting the rapid transfer of electrons inside and outside the active particles, solving the problem of insufficient electron transfer capacity between active particles in conventional potassium titanate materials, and further improving the rate performance of the electrode material.

[0024] 3. When using the method disclosed in this application to prepare high oxygen vacancy titanate nanomaterials, the process of strong base etching titanium silicon carbide and the process of synthesizing potassium titanate nanostructures are carried out simultaneously. The addition of potassium fluoride improves the wettability of the reaction solution, enhances the dispersibility of titanium silicon carbide, and can stabilize the morphology of the synthesized potassium titanate nanostructures.

[0025] 4. When preparing titanate nanomaterials using the method disclosed in this application, oxygen must be continuously introduced during the oil bath heating process. Oxygen introduction is not only conducive to the synthesis of nanomaterials with high oxygen vacancies, but also can accelerate the synthesis reaction;

[0026] 5. This application significantly improves the rate performance of electrode materials and effectively increases the specific capacity of potassium titanate materials by optimizing reaction conditions and controlling key steps. It has broad application prospects in the field of energy storage and can provide strong support for the development of sustainable energy technologies.

[0027] 6. This application utilizes a wet chemical method to prepare potassium titanate nanomaterials. Compared with traditional methods, this method simplifies the process flow and does not require high-temperature treatment, thereby reducing energy and resource consumption during the production process. It is simple, safe, and has lower production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a SEM image of ov-KTO prepared in Example 1;

[0029] Figure 2 are the XRD patterns of Ti3SiC2 and ov-KTO prepared in Example 1;

[0030] Figure 3 is a TEM image of ov-KTO prepared in Example 1;

[0031] Figure 4 This is the mapping diagram of ov-KTO prepared in Example 1;

[0032] Figure 5 are XPS images of ov-KTO prepared in Example 1 and ao-KTO prepared in Comparative Example 1, wherein panel a is XPS SO 1s of ov-KTO, panel b is XPS O 1s of ao-KTO, panel c is XPS Ti 2p of ov-KTO, and panel d is XPS Ti 2p of ao-KTO;

[0033] Figure 6 This is the TGA analysis image of ov-KTO in air and nitrogen atmosphere;

[0034] Figure 7 This is the charge and discharge curve of the ov-KTO / / AC supercapacitor at different current densities;

[0035] Figure 8 The ov-KTO / / AC supercapacitor has a current density of 5A g -1 Long cycle performance diagram when . DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0037] Example 1

[0038] 1. Prepare a 40% potassium hydroxide solution, sonicate for 90 seconds to completely dissolve it, and add potassium fluoride dihydrate to the potassium hydroxide solution to enhance wettability. The mass ratio of potassium fluoride dihydrate to potassium hydroxide is 1:1.

[0039] 2. Add titanium silicon carbide powder (granular, 98%-200 mesh) to the mixed solution prepared in the previous step. The mass ratio of titanium silicon carbide to potassium hydroxide is 1:40. Stir with a magnetic stirrer to ensure uniform distribution of titanium silicon carbide.

[0040] 3. Place the mixture in an oil bath, maintain a constant temperature of 90°C, and stir while heating at 300 rpm. Continuously introduce oxygen into the mixture at a flow rate of 3 L / min. Allow the mixture to react for 10 days.

[0041] 4. First, centrifuge the reaction solution at 8000 rpm for 5 minutes, wash once with ultrapure water, and aspirate the upper reddish-brown liquid; add water to the solid, ultrasonicate for 10-15 minutes, centrifuge at 9000 rpm for 10 minutes, and aspirate the supernatant; add water to the solid again, ultrasonicate for 10-15 minutes, and centrifuge at 9000 rpm for 8 minutes; aspirate the supernatant, add ethanol to the solid, ultrasonicate for 10 minutes, centrifuge at 8500 rpm for 8 minutes, aspirate the supernatant, add water to the solid, ultrasonicate for 4-5 minutes, and centrifuge at 8000 rpm. Repeat the operation until the upper emulsion appears after centrifugation.

[0042] After the upper emulsion appears, transfer the upper emulsion. Continue adding water to the solid, sonicate for 8 minutes, centrifuge at 7000 rpm for 5 minutes, and transfer the upper emulsion. Continue adding water, sonicate for 8 minutes, centrifuge at 6000 rpm for 5 minutes, and transfer the upper emulsion. Repeat this process, reducing the speed by 1000 rpm each time, until the speed is reduced to 2000 rpm and no emulsion is produced.

[0043] All emulsions were placed in batches into the same centrifuge tube for centrifugation at a speed of 9000 rpm. After solids were generated during centrifugation, ultrasonication was not required. The emulsion was continued to be added until all the emulsions were centrifuged.

[0044] Water was added to the obtained solid, and the solid was washed once by centrifugation, then washed twice with a water / ethanol mixture with a volume ratio of 1:1, and finally washed twice with ethanol to obtain potassium titanate nanomaterials with high oxygen vacancies, which were recorded as ov-KTO.

[0045] Comparative Example 1

[0046] A portion of the obtained ov-KTO was dried in a vacuum drying oven at 100°C for 12 hours, then poured into a clean small crucible, placed in a muffle furnace, and calcined at 600°C for 12 hours in an air atmosphere to obtain potassium titanate nanomaterials after high-temperature air oxidation, which was recorded as ao-KTO.

[0047] Related performance tests:

[0048] 1. Figure 1 This is a scanning electron microscope (SEM) image of ov-KTO prepared in Example 1, showing the formation of ov-KTO nanowires.

[0049] 2. Figure 2 XRD patterns of Ti3SiC2 and ov-KTO; the disappearance of the Ti3SiC2 peak and the presence of a single peak at ~9.5° of the (001) interlayer plane of potassium titanate confirm the complete transformation of Ti3SiC2 to ov-KTO.

[0050] 3. Figure 3 This is a TEM image of ov-KTO prepared in Example 1. It can be seen from the figure that the ov-KTO nanowires are bundle-like structures with a wire diameter of less than 10 nm. The interlayer spacing of ~0.85 nm corresponds to the spacing between the (001) planes of ov-KTO.

[0051] 4. Figure 4 This is the mapping diagram of ov-KTO prepared in Example 1, which confirms that K, Ti and O are uniformly distributed in the nanowires.

[0052] 5. Figure 5 The XPS images of ov-KTO prepared in Example 1 and ao-KTO prepared in Comparative Example 1 show that ov-KTO contains a large amount of oxygen defects and Ti 3+ .

[0053] 6. Figure 6These are TGA analysis images of ov-KTO prepared in Example 1 in air and nitrogen atmospheres. The figure shows that when heated, the material reacts with oxygen, resulting in lower mass loss than in nitrogen, which is consistent with the XPS analysis results.

[0054] 7. Mix the active material (potassium titanate nanomaterial ov-KTO prepared in Example 1), acetylene black, and PVDF in a mass ratio of 8:1:1, for a total of 100 mg. After grinding, add 250-270 mL of N-methylpyrrolidone (NMP) and stir until it becomes a paste. This paste is then coated on a 20 μm thick titanium foil and a 40 μm thick electrode. After drying, the electrode piece is cut using a microtome and vacuum-dried at 100°C to form an electrode.

[0055] Commercially available powdered activated carbon, acetylene black, and PVDF were mixed in a mass ratio of 8:1:1, totaling 100 mg. After grinding, 250–270 mL of N-methylpyrrolidone (NMP) was added and stirred into a paste. The paste was then coated onto a 20 μm thick titanium foil and a 100 μm thick electrode. After drying, the electrode was cut using a microtome and vacuum-dried at 100°C to serve as the second electrode.

[0056] Asymmetric aqueous supercapacitors were assembled using 30 mol / kg KAc aqueous solution as the electrolyte and filter paper as the separator to demonstrate the practical application of ov-KTO.

[0057] Figure 7 The charge and discharge curves of the ov-KTO / / AC supercapacitor at different current densities show that compared with traditional water-ion capacitors (working voltage is usually <1V), the increased working voltage greatly enhances the performance of the energy storage device.

[0058] 8. Figure 8 It is shown that the ov-KTO / / AC supercapacitor has a current density of 5A g -1 As can be seen from the figure, the device exhibits ultra-stable cycle performance (at 5A g -1 After 4000 cycles at a current density of 1A g, the capacity decay was only 10%. Further tests found that at 1A g -1 The capacity decay is only 19% after 20,000 cycles at a current density of 1.5 GHz. This excellent performance is the result of a combination of faradaic and non-faradaic charge storage mechanisms.

[0059] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a high oxygen vacancy titanate nanomaterial, characterized in that: The steps include: 1) Prepare an aqueous solution of a strong base, and add potassium fluoride dihydrate to the aqueous solution of the strong base, with the mass ratio of the strong base, potassium fluoride dihydrate, and water being 1:0.5~1.5:1~2; 2) adding titanium silicon carbide powder to the solution prepared in step 1), with the mass ratio of titanium silicon carbide to strong base being 1:40-50; 3) heating the mixture obtained in step 2) in an oil bath at a temperature of 80-90°C for 7-12 days, while stirring, and continuously introducing oxygen into the mixture during the heating process; 4) Repeat centrifugation and washing to obtain the upper emulsion, collect the emulsion and centrifuge it, collect the solid, and wash it to obtain high oxygen vacancy titanate nanomaterials.

2. The method for preparing a high oxygen vacancy titanate nanomaterial according to claim 1, wherein: In step 1), the strong base is any one of potassium hydroxide and sodium hydroxide.

3. The method for preparing a high oxygen vacancy titanate nanomaterial according to claim 1, wherein: In step 3), the flow rate of oxygen is 1~5 L / min.

4. The method for preparing a high oxygen vacancy titanate nanomaterial according to claim 1, wherein: In step 3), the stirring speed is 300-500 rpm.

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