A post-treatment method and application of flame-synthesized titanium niobium oxide powder

Abstract

The present invention relates to the technical field of titanium niobium oxides, and discloses a post-treatment method and application of flame-synthesized titanium niobium oxide powder, which includes the following steps: Step 1: The titanium niobium oxide powder obtained by the flame synthesis method is an amorphous powder, which is annealed in an oxygen atmosphere at an annealing temperature of 1000-1200 °C and a holding time of 2-3 h to obtain a monoclinic phase powder; Step 2: The hollow sphere particles in the monoclinic phase powder are ball-milled and crushed, the ball-to-material ratio is 1:1-3, and the ball-milling speed is 100-500 r / min; Step 3: Filter pressing and drying are carried out to obtain the post-treated titanium niobium oxide powder. The present invention performs post-treatment on the titanium niobium oxide obtained by the flame synthesis method, which can efficiently remove impurities and unreacted substances in the titanium niobium oxide powder, obtain a monoclinic phase powder at the same time, and achieve precise control of the particle size distribution of the powder, reducing the complexity of the post-treatment process.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium niobium oxides, and particularly to a post-treatment method and application of flame-synthesized titanium niobium oxide powder. Background Art

[0002] Titanium niobium oxide (TNO) is a composite material with excellent chemical stability and high temperature resistance, and is widely used in the fields of electronics, catalysis, batteries and superconductivity. Traditional preparation methods have problems such as high energy consumption, long production cycle, and difficulty in controlling the composition uniformity. The patent with the publication number CN110465257B discloses a nanoparticle swirl flame atomization doping synthesis system and its synthesis method. The primary air and fuel gas enter the swirl burner through adjacent gas flow channels to form a swirl air flow, and the fuel gas is ignited to form a swirl flame. The metal precursor solution is atomized by a swirl impact atomizer and then enters the swirl flame for combustion to generate a nanoparticle stream, and the nanoparticle stream is diluted and cooled before being collected. Therefore, the flame synthesis method shows great potential in the preparation of titanium niobium oxide powder due to its advantages of rapidity, low energy consumption, simple equipment, high purity and easy industrial production, and is expected to overcome the deficiencies of traditional methods and improve product performance. However, the post-treatment process of the powder prepared by the flame synthesis method is not mentioned in this patent. In fact, after the powder prepared by the flame synthesis method undergoes a rapid combustion reaction, the post-treatment process is crucial for improving the performance and applicability of the powder.

[0003] The post-treatment process can remove impurities and unreacted raw materials generated during the combustion process, improve the purity of the powder, improve the morphology and structure of the powder, enhance its dispersibility and stability in the final product, and adjust the particle size distribution of the powder through subsequent treatment steps such as grinding and classification to meet the requirements of different application fields. However, there are many problems with the current traditional post-treatment process, including: it is difficult to completely remove impurities and unreacted substances, which affects the purity of the final product; precise control of the particle size distribution requires delicate operations and equipment, which increases the complexity of the process to a certain extent; and it is difficult to precisely control the powder properties of titanium niobium oxide through post-treatment. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a post-treatment method and application of flame-synthesized titanium niobium oxide powder. By post-treating the flame-synthesized titanium niobium oxide powder, including the annealing and crystal phase adjustment process and the ball milling and crushing process in an oxygen atmosphere, not only can the impurities in the titanium niobium oxide powder be removed to improve the purity of the powder, but also the uniform crystallization and stable crystal phase of the oxide can be achieved, the morphology and structure of the powder can be improved, precise control of the particle size distribution of the powder can be realized, and the complexity of the post-treatment process can be reduced.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a post-treatment method for flame-synthesized titanium niobium oxide powder, comprising the following steps:

[0007] Step 1: The titanium niobium oxide powder obtained by the flame synthesis method is an amorphous powder with a D50 particle size of 0.9 - 3 μm and a D90 particle size of 10 - 15 μm; it is annealed in an oxygen atmosphere at an annealing temperature of 1000 - 1200 °C for a holding time of 2 - 3 h to obtain a monoclinic phase powder.

[0008] Step 2: The hollow sphere particles in the monoclinic phase powder are ball-milled and broken, with a ball-to-material ratio of 1:1 - 3 and a ball-milling rotation speed of 100 - 500 r / min.

[0009] Step 3: Pressure filtration and drying are carried out to obtain the post-treated titanium niobium oxide powder.

[0010] The flame synthesis method is to add a metal precursor and an organic additive to an organic fuel, and then through the rapid combustion reaction of the fuel gas, titanium niobium oxide powder (TiNb2O7) is obtained. Since the titanium niobium oxide powder obtained by the flame synthesis method is an amorphous powder and contains organic impurities and unreacted metal precursor raw materials, it cannot be directly applied to lithium batteries. The present invention is a post-treatment process for the titanium niobium oxide powder prepared by the flame synthesis method. By controlling the annealing condition parameters (including annealing temperature, time, etc.) during the annealing and crystal phase adjustment process in an oxygen atmosphere, not only can the impurities in the titanium niobium oxide powder be removed to improve the purity of the powder, but also the amorphous powder can be transformed into a powder with a monoclinic m-TNO phase (Monoclinic-TiNb2O7), realizing the uniform crystallization and stable crystal phase of the oxide, and improving the morphology and structure of the powder.

[0011] However, the annealing and crystal phase adjustment process will go through a high-temperature process, and the high temperature will reduce the potential barrier between particles, thus promoting the agglomeration of titanium niobium oxide powder. Agglomeration between crystals will form hollow sphere particles. Ball milling can break the agglomerates of titanium niobium oxide powder, but appropriate ball milling parameters (including ball-to-material ratio, ball-milling rotation speed, etc.) need to be selected to avoid particle damage while dispersing the particles and to achieve precise control of the particle size distribution of the powder.

[0012] Preferably, the impurity content of the titanium niobium oxide powder obtained by the flame synthesis method is 3 - 6 wt%.

[0013] The particle size of the titanium niobium oxide powder obtained by the flame synthesis method is relatively large, and the gap between the D50 and D90 particle sizes is large, with uneven particle size distribution. Through the coordinated control of annealing and ball milling, the titanium niobium oxide powder can have a stable crystal phase while having a smaller particle size and a concentrated particle size distribution.

[0014] Preferably, the heating rate of the annealing is 10-20 °C / min.

[0015] Preferably, the oxygen flow rate during the annealing is 3-5 L / min.

[0016] Preferably, the conditions for the annealing are as follows: heating from room temperature to 1000 °C at a heating rate of 10-20 °C / min, holding for 2-3 h, and then cooling to room temperature.

[0017] Preferably, the time for ball milling is 1-3 h.

[0018] Preferably, the pressure for pressure filtration is 0.2-0.5 MPa, and the time is 20-60 min; the medium for pressure filtration is ethanol.

[0019] Preferably, the temperature for drying is 60-150 °C, and the time is 1-4 h.

[0020] Preferably, the particle size D50 of the post-treated titanium niobium oxide powder is 300-600 nm, and D90 is 800-1200 nm.

[0021] In a second aspect, the present invention also provides an application of the post-treated titanium niobium oxide powder in a lithium battery.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention performs post-treatment on the titanium niobium oxide obtained by the flame synthesis method, which can efficiently remove impurities and unreacted substances in the titanium niobium oxide powder, obtain a monoclinic phase powder at the same time, and achieve precise control of the particle size distribution of the powder, as well as reduce the complexity of the post-treatment process;

[0024] (2) The present invention provides a post-treatment process for the flame-synthesized titanium niobium oxide powder, which has the advantages of simple post-treatment process, stable crystal phase, and precise control of the particle size distribution of the powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the XRD pattern of the powder synthesized by the flame synthesis method of the present invention, the powder after annealing, and the powder after drying.

[0026] Figure 2 It is the particle size distribution diagram of the titanium niobium oxide powder Ⅰ prepared by the flame synthesis method of the present invention.

[0027] Figure 3 It is the particle size distribution diagram of the titanium niobium oxide powder Ⅰ prepared by the flame synthesis method of the present invention after being post-treated in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0028] The technical solutions of the present invention will be described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0029] 1. Post-treatment of titanium niobium oxide powder synthesized by flame:

[0030] Step 1: Titanium niobium oxide powder prepared by flame synthesis method (for the flame synthesis method, refer to the patent: publication number CN110465257B, invention name: a nano-particle swirling flame atomization doping synthesis system and its synthesis method):

[0031] Select and weigh appropriate amounts of titanium and niobium metal nitrates as metal precursors, select and measure an organic additive and an organic fuel, so that the volume ratio of the organic additive to the organic fuel is 1: (4 - 9). The organic additive includes 2-ethylhexanoic acid or naphthenic acid, and the organic fuel includes ethanol, butanol or xylene mixture; mix the metal nitrate, organic additive and organic fuel evenly to obtain a metal precursor solution, the metal ion concentration is less than or equal to 0.5 mol / L and greater than or equal to 0.1 mol / L. Pass the metal precursor solution and atomizing gas (compressed air) into the swirling impinging atomizer through the precursor liquid inlet and atomizing gas inlet respectively, so that the precursor solution is atomized by the atomizing gas into metal precursor droplets with a particle size less than or equal to 30μm. The particle size of the droplets is adjusted by the relative height of the precursor liquid outlet and the atomizing gas outlet. The metal precursor droplets enter the stable swirling pilot flame, are ignited by the swirling pilot flame, and burn to synthesize nanoparticles; the nanoparticles rise with the combustion flue gas to form a high-temperature nanoparticle stream, obtaining titanium niobium oxide powder with a D50 particle size of 0.9 - 3μm and a D90 particle size of 10 - 15μm. The impurities therein are mainly organic impurities and a small amount of Na, Si, P, etc. (impurities such as Na, Si, P are contained in the purchased raw materials themselves, and the quantity will vary from dozens to hundreds of ppm), and the impurity content is 3 - 6wt%.

[0032] Dry the titanium niobium oxide powder collected from the front end of the process. The oven is an explosion-proof oven, and the temperature is set at 80 - 180°C for drying. Anneal the titanium niobium oxide powder to remove carbon and adjust the crystal phase. Use a corundum pot, and load 200 - 500g of titanium niobium oxide into each pot. Cover the corundum pot, but leave a gap so that oxygen around can enter the inside of the corundum pot for annealing treatment. During the annealing process, the heating rate is 10 - 20°C / min, the temperature is raised to 1000 - 1200°C, and kept warm for 2 - 3h. At the same time of heating and keeping warm, an oxygen atmosphere is adopted, and the oxygen flow rate is 3 - 5 L / min. After annealing, cool to room temperature to obtain monoclinic phase powder with a purity of 99.9%.

[0033] Step 2: Annealing and adjusting the crystal phase will go through a high-temperature process. High temperature will reduce the potential barrier between particles, thus promoting the agglomeration of titanium niobium oxide powder. Ball milling can break some of the agglomerates (hollow spherical particles) in the monoclinic phase powder. First, fill a small amount of zirconium beads at the bottom of the ball milling tank, load the powder, with a ball-to-material ratio of 1:1 - 3. Tighten the ball milling tank to prevent the internal powder from spilling during rotation. Then carry out ball milling, with a ball milling speed of 100 - 500 r / min and a ball milling running time of 1 - 3 h.

[0034] Step 3: Carry out pressure filtration on the titanium niobium oxide powder: Use a filtration tank to carry out pressure filtration on the ball-milled titanium niobium oxide powder. The filtration pressure is 0.2 - 0.5 MPa, the filtration accuracy of the filter paper is 0.45 μm, and the time is 20 - 60 min. When filtering 1 - 2 tanks, set the pressure to 0.2 - 0.5 MPa, and the pressure filtration time is 20 - 30 min. The pressure filtration is completed when the water loss rate < 16%. When filtering 3 - 4 tanks, set the pressure to 0.2 - 0.5 MPa, and the pressure filtration time is 30 - 60 min. The pressure filtration is completed when the water loss rate < 20%. Collect the anhydrous ethanol flowing out during pressure filtration. After completing the filtration, before opening the filtration tank, turn off the air compressor to ensure there is no pressure in the filtration tank. Open the filtration tank and check if there are large particle powders in the sieve mesh. If so, use tools such as a scraper and a brush to crush them and manually sieve them. Add a stainless steel filter membrane to the filter paper to prevent the filter paper material from falling and contaminating the powder.

[0035] Step 4: Carry out drying treatment on the titanium niobium oxide powder: Put the titanium niobium oxide powder with a water loss rate less than 20% obtained after pressure filtration (if the water loss rate of the powder is greater than 20%, cover it with a lid and place it in the air for one hour, then measure the water loss rate again) into the oven for drying. The powder needs to be leveled with a scraper. The drying temperature is 60 - 150 °C, and the time is 1 - 4 h. Take 20 g of the dried powder for water loss rate test and whiteness test. A water loss rate of 0% is qualified, and a whiteness above 80 is qualified.

[0036] Step 5: Package the titanium niobium oxide powder: Use a vacuum pumping device to fill and vacuum package the powder, and protect it with nitrogen on the outside. Pay attention to the integrity of the vacuum packaging and nitrogen packaging and check for air leakage.

[0037] 2. Lithium battery:

[0038] Use the titanium niobium oxide powder obtained after post-treatment as the negative electrode material to make a lithium battery.

[0039] Example 1

[0040] Step 1: As Figure 2As shown in the figure, the titanium niobium oxide powder I (amorphous powder, with a D50 particle size of 1362.42 nm, a D90 particle size of 11029.21 nm, and an impurity content of 5 wt%) obtained by flame synthesis and collected from the front end of the process is dried, and the drying temperature is set at 120 °C. The titanium niobium oxide powder is annealed to remove carbon and adjust the crystal phase. Use a corundum pot, and load 300 g of titanium niobium oxide into each pot. Cover the corundum pot, but leave a gap so that oxygen around can enter the inside of the corundum pot for annealing treatment. During the annealing process, the heating rate is 10 °C / min, the temperature is raised to 1000 °C, and it is held for 2 h. An oxygen atmosphere is used while heating and holding, with an oxygen flow rate of 3 L / min. After annealing, it is cooled to room temperature to obtain a monoclinic phase powder with a purity of 99.9%.

[0041] Step 2: Ball mill and break some of the agglomerates (hollow spherical particles) in the monoclinic phase powder. First, fill a small amount of zirconium beads at the bottom of the ball mill pot, load the powder, and the ball-to-powder ratio is 1:1. Tighten the ball mill pot to prevent the internal powder from spilling out during rotation; then carry out ball milling. The ball milling speed is 500 r / min, and the ball milling operation time is 1 h.

[0042] Step 3: Carry out pressure filtration on the titanium niobium oxide powder: Use a filtration tank to carry out pressure filtration on the ball-milled titanium niobium oxide powder. The filtration pressure is 0.3 MPa, the filtration accuracy of the filter paper is 0.45 μm, filter 1 pot, the pressure filtration time is 30 min, and the pressure filtration is completed when the water loss rate is 10%. Collect the anhydrous ethanol flowing out during pressure filtration.

[0043] Step 4: Carry out drying treatment on the titanium niobium oxide powder: Put the titanium niobium oxide powder with a water loss rate of 10% obtained after pressure filtration into an oven for drying. The powder needs to be leveled with a spatula. After drying in the oven at 70 °C for 30 min, it is broken with a glass rod, and then the temperature is raised to 120 °C and baked for 1.5 h; Take 20 g of the baked powder for water loss rate test and whiteness test. The water loss rate is 0%, the whiteness is 85, and the BET test is 2.705 m 2 / g, as Figure 3 shown is the particle size distribution diagram of the powder after post-treatment.

[0044] As Figure 1 shown are the XRD diagrams of the powder obtained by flame synthesis (titanium niobium oxide powder I obtained by flame synthesis), the powder after annealing (the monoclinic phase powder obtained in Step 1), and the powder after drying (the dried powder obtained in Step 4). By comparing with the standard XRD spectrum of the m-TNO phase (Monoclinic-TiNb2O7), it can be seen that the powder obtained by flame synthesis can obtain the m-TNO phase after annealing, and the powder obtained after ball milling and drying still maintains a stable crystal phase.

[0045] Example 2

[0046] Step 1: Dry the titanium niobium oxide powder I prepared by the flame synthesis method collected from the front end of the process at a set temperature of 120 °C. Anneal the titanium niobium oxide powder to remove carbon and adjust the crystal phase. Use a corundum pot, fill 300 g of titanium niobium oxide in each pot. Cover the corundum pot, but leave a gap so that the surrounding oxygen can enter the inside of the corundum pot for annealing. During the annealing process, the heating rate is 20 °C / min, the temperature is raised to 1000 °C, and it is kept warm for 2 h. While heating and keeping warm, an oxygen atmosphere is used, and the oxygen flow rate is 5 L / min. After annealing, cool it to room temperature to obtain a monoclinic phase powder with a purity of 99.9%.

[0047] Step 2: Ball mill and crush some of the agglomerates (hollow sphere particles) in the monoclinic phase powder. First, fill a small amount of zirconium beads at the bottom of the ball mill pot, load the powder, and the ball-to-material ratio is 1:1. Tighten the ball mill pot to prevent the internal powder from spilling out during rotation; then carry out ball milling. The ball milling speed is 300 r / min, and the ball milling operation time is 2 h.

[0048] Step 3: Carry out pressure filtration on the titanium niobium oxide powder: Use a filtration tank to carry out pressure filtration on the ball-milled titanium niobium oxide powder. The filtration pressure is 0.3 MPa, the filtration accuracy of the filter paper is 0.45 μm, filter 1 pot, and the pressure filtration time is 30 min. When the water loss rate reaches 11%, the pressure filtration is completed, and the anhydrous ethanol flowing out during pressure filtration is collected.

[0049] Step 4: Carry out drying treatment on the titanium niobium oxide powder: Put the titanium niobium oxide powder with a water loss rate of 11% obtained after pressure filtration into the oven for drying. The powder needs to be leveled with a spatula. After drying in the oven at 70 °C for 30 min, it is broken with a glass rod, and then heated to 120 °C and baked for 1.5 h; Take 20 g of the baked powder for water loss rate test and whiteness test. The water loss rate is 0%, the whiteness is 86, and the BET test is 2.370 m 2 / g.

[0050] Example 3

[0051] Step 1: Dry the titanium niobium oxide powder I prepared by the flame synthesis method collected from the front end of the process at a set temperature of 120 °C. Anneal the titanium niobium oxide powder to remove carbon and adjust the crystal phase. Use a corundum pot, fill 1000 g of titanium niobium oxide in each pot. Cover the corundum pot, but leave a gap so that the surrounding oxygen can enter the inside of the corundum pot for annealing. During the annealing process, the heating rate is 20 °C / min, the temperature is raised to 1000 °C, and it is kept warm for 2 h. While heating and keeping warm, an oxygen atmosphere is used, and the oxygen flow rate is 5 L / min. After annealing, cool it to room temperature to obtain a monoclinic phase powder with a purity of 99.9%.

[0052] Step 2: Ball-mill and crush some of the agglomerates (hollow spherical particles) in the monoclinic phase powder. First, fill a small amount of zirconium beads at the bottom of the ball-mill tank, load the powder, with a ball-to-material ratio of 1:1. Tighten the ball-mill tank to prevent the internal powder from spilling out during rotation. Then, conduct ball-milling at a rotation speed of 300 r / min for 2 h.

[0053] Step 3: Perform pressure filtration on the titanium niobium oxide powder: Use a filtration tank to perform pressure filtration on the ball-milled titanium niobium oxide powder. The filtration pressure is 0.3 MPa, the filtration accuracy of the filter paper is 0.45 μm, filter 4 tanks, and the pressure filtration time is 60 min. The pressure filtration is completed when the water loss rate reaches 21%, and collect the anhydrous ethanol flowing out during pressure filtration.

[0054] Step 4: Perform drying treatment on the titanium niobium oxide powder: Cover the titanium niobium oxide powder with a water loss rate of 21% obtained after pressure filtration, place it in the air for one hour, and then re-measure the water loss rate to be 18%. Put it into the oven for drying. The powder needs to be leveled with a spatula. After drying in the oven at 70 °C for 30 min, crush it with a glass rod, and then raise the temperature to 120 °C and bake for 1.5 h. Take 20 g of the baked powder for water loss rate test and whiteness test. The water loss rate is 0%, the whiteness is 86, and the BET test is 2.821 m 2 / g.

[0055] Example 4

[0056] Step 1: Perform drying treatment on the titanium niobium oxide powder II (amorphous powder, with particle size D50 of 919.31 nm, D90 of 11486.46 nm, and impurity content of 4 wt%) prepared by flame synthesis method collected from the front end of the process, and set the temperature to 120 °C for drying. Anneal the titanium niobium oxide powder to remove carbon and adjust the crystal phase. Use a corundum pot, load 300 g of titanium niobium oxide in each pot. Cover the corundum pot, but leave a gap to allow oxygen around to enter the inside of the corundum pot for annealing treatment. During the annealing process, the heating rate is 10 °C / min, raise the temperature to 1000 °C, and keep it at this temperature for 2 h. While heating up and keeping the temperature, use an oxygen atmosphere with an oxygen flow rate of 3 L / min. After annealing, cool it to room temperature to obtain a monoclinic phase powder with a purity of 99.9%.

[0057] Step 2: Ball-mill and crush some of the agglomerates (hollow spherical particles) in the monoclinic phase powder. First, fill a small amount of zirconium beads at the bottom of the ball-mill tank, load the powder, with a ball-to-material ratio of 1:1. Tighten the ball-mill tank to prevent the internal powder from spilling out during rotation. Then, conduct ball-milling at a rotation speed of 460 r / min for 1 h.

[0058] Step 3: Filter press the titanium niobium oxide powder: Use a filter tank to perform filter pressing on the ball-milled titanium niobium oxide powder. The filtration pressure is 0.3 MPa, the filtration accuracy of the filter paper is 0.45 μm, filter 1 tank, the filter pressing time is 30 min, and the filter pressing is completed when the water loss rate is 10%. Collect the absolute ethanol flowing out during filter pressing.

[0059] Step 4: Dry the titanium niobium oxide powder: Put the titanium niobium oxide powder with a water loss rate of 10% obtained after filter pressing into an oven for drying. The powder needs to be leveled with a spatula. After baking at 70 °C in the oven for 30 min, crush it with a glass rod, and then raise the temperature to 120 °C and bake for 1.5 h; Take 20 g of the baked powder for water loss rate test and whiteness test. The water loss rate is 0%, the whiteness is 86, and the BET test is 2.775 m 2 / g.

[0060] Comparative Example 1

[0061] The difference from Example 1 is that the annealing temperature is too low, and the annealing temperature is 500 °C.

[0062] Step 1: Dry the titanium niobium oxide powder Ⅰ prepared by flame synthesis collected from the front end of the process. Set the temperature to 120 °C for drying. Anneal the titanium niobium oxide powder to remove carbon and adjust the crystal phase. Use a corundum pot, load 300 g of titanium niobium oxide per pot. Cover the corundum pot, but leave a gap so that oxygen around can enter the inside of the corundum pot for annealing treatment. During the annealing process, the heating rate is 10 °C / min, the temperature is raised to 500 °C, and keep it for 2 h. At the same time of heating up and keeping warm, use an oxygen atmosphere, and the oxygen flow rate is 3 L / min. After annealing, cool it to room temperature to obtain the powder, but this powder is not in the monoclinic crystal phase, and the purity is 99.9%.

[0063] Step 2: Ball mill and crush the powder. First, fill a small amount of zirconium beads at the bottom of the ball mill tank, load the powder, and the ball-to-material ratio is 1:1. Tighten the ball mill tank to prevent the powder inside from spilling out during rotation; Then perform ball milling. The ball milling speed is 500 r / min, and the ball milling operation time is 1 h.

[0064] Step 3: Filter press the titanium niobium oxide powder: Use a filter tank to perform filter pressing on the ball-milled titanium niobium oxide powder. The filtration pressure is 0.3 MPa, the filtration accuracy of the filter paper is 0.45 μm, filter 1 tank, the filter pressing time is 30 min, and the filter pressing is completed when the water loss rate is 10%. Collect the absolute ethanol flowing out during filter pressing.

[0065] Step 4: Drying the titanium niobium oxide powder: The titanium niobium oxide powder with a water loss rate of 10% obtained after filter pressing is put into an oven for drying. The powder needs to be flattened with a scraper, baked in an oven at 70°C for 30 minutes, broken with a glass rod, and then heated to 120°C for 1.5 hours. Take 20g of the dried powder for water loss rate test and whiteness test. The water loss rate is 0%, the whiteness is 84, and the BET test is 5.981m 2 / g.

[0066] Comparative Example 2

[0067] The difference from Example 1 is that the oxygen flow rate during annealing is too large, and the oxygen flow rate is 10 L / min.

[0068] Step 1: Dry the titanium niobium oxide powder I obtained by flame synthesis collected from the front end of the process, and set the drying temperature to 120°C. Anneal the titanium niobium oxide powder to remove carbon and adjust the crystal phase. Use a corundum pot, fill each can with 300g of titanium niobium oxide, cover the corundum pot, but leave a gap to allow the surrounding oxygen to enter the corundum pot, and anneal. During the annealing process, the heating rate is 10°C / min, the temperature is raised to 1000°C, and the temperature is kept for 2h. While heating and keeping the temperature, an oxygen atmosphere is used, and the oxygen flow rate is 10L / min. After annealing, cool to room temperature to obtain a monoclinic phase powder with a purity of 99.9%.

[0069] Step 2: Ball milling is used to crush some agglomerates (hollow spherical particles) in the monoclinic phase powder. First, a small amount of zirconium beads is filled at the bottom of the ball mill, and then the powder is loaded with a ball-to-material ratio of 1:1. The ball mill is tightened to prevent the powder inside from spilling out during rotation. Then, ball milling is performed with a ball mill speed of 500 r / min and a ball mill operation time of 1 h.

[0070] Step 3: Filter press the titanium niobium oxide powder: Use a filter tank to filter press the ball-milled titanium niobium oxide powder, the filtration pressure is 0.3MPa, the filter paper filtration accuracy is 0.45μm, filtration is 1 tank, the filtration time is 30min, the filtration is completed when the water loss rate is 10%, and the anhydrous ethanol flowing out of the filtration is collected.

[0071] Step 4: Drying the titanium niobium oxide powder: The titanium niobium oxide powder with a water loss rate of 10% obtained after filter pressing is put into an oven for drying. The powder needs to be flattened with a scraper, baked in an oven at 70°C for 30 minutes, broken with a glass rod, and then heated to 120°C for 1.5 hours. Take 20g of the dried powder for water loss rate test and whiteness test. The water loss rate is 0%, the whiteness is 85, and the BET test is 1.567m 2 / g.

[0072] Comparative Example 3

[0073] The difference from Example 1 is that the ball-to-material ratio during ball milling is 1:20.

[0074] Step 1: Dry the titanium niobium oxide powder I prepared by flame synthesis collected from the front end of the process. Set the temperature at 120 °C for drying. Anneal the titanium niobium oxide powder to remove carbon and adjust the crystal phase. Use a corundum pot, load 300 g of titanium niobium oxide powder into each pot. Cover the corundum pot, but leave a gap so that oxygen can enter the inside of the corundum pot for annealing. During the annealing process, the heating rate is 10 °C / min, the temperature is raised to 1000 °C, and held for 2 h. While heating and holding, use an oxygen atmosphere with an oxygen flow rate of 3 L / min. After annealing, cool to room temperature to obtain a monoclinic phase powder with a purity of 99.9%.

[0075] Step 2: Ball mill and break some of the agglomerates (hollow sphere particles) in the monoclinic phase powder. First, fill a small amount of zirconium beads at the bottom of the ball mill pot, load the powder, with a ball-to-material ratio of 1:20. Tighten the ball mill pot to prevent the internal powder from spilling during rotation. Then carry out ball milling at a ball milling speed of 500 r / min for 1 h.

[0076] Step 3: Carry out pressure filtration on the titanium niobium oxide powder: Use a filtration tank to carry out pressure filtration on the ball-milled titanium niobium oxide powder. The filtration pressure is 0.3 MPa, the filtration accuracy of the filter paper is 0.45 μm, filter 1 pot, and the pressure filtration time is 30 min. When the water loss rate reaches 10%, the pressure filtration is completed, and collect the anhydrous ethanol flowing out during pressure filtration.

[0077] Step 4: Carry out drying treatment on the titanium niobium oxide powder: Put the titanium niobium oxide powder with a water loss rate of 10% obtained after pressure filtration into the oven for drying. The powder needs to be leveled with a spatula. After baking at 70 °C in the oven for 30 min, break it with a glass rod, and then raise the temperature to 120 °C and bake for 1.5 h. Take 20 g of the baked powder for water loss rate test and whiteness test. The water loss rate is 0%, the whiteness is 85, and the BET test is 1.650 m 2 / g.

[0078] Comparative Example 4

[0079] The difference from Example 1 is that the particle size of the flame-synthesized titanium niobium oxide powder used is too large, with a particle size D50 of 3200 nm and D90 of 7200 nm.

[0080] Step 1: The titanium niobium oxide powder III (amorphous powder, with a particle size D50 of 3200 nm, D90 of 7200 nm, and an impurity content of 6 wt%) obtained by flame synthesis and collected from the front end of the process is dried at a set temperature of 120°C. The titanium niobium oxide powder is annealed to remove carbon and adjust the crystal phase. Use a corundum pot, and load 300 g of titanium niobium oxide into each pot. Cover the corundum pot, but leave a gap so that oxygen can enter the inside of the corundum pot for annealing. During the annealing process, the heating rate is 10°C / min, the temperature is raised to 1000°C, and it is held for 2 h. An oxygen atmosphere is used while heating and holding, with an oxygen flow rate of 3 L / min. After annealing, it is cooled to room temperature to obtain a monoclinic phase powder with a purity of 99.9%.

[0081] Step 2: Ball mill and break some of the agglomerates (hollow spherical particles) in the monoclinic phase powder. First, fill a small amount of zirconium beads at the bottom of the ball mill pot, load the powder, with a ball-to-material ratio of 1:1. Tighten the ball mill pot to prevent the internal powder from spilling during rotation; then perform ball milling at a ball milling speed of 500 r / min for 1 h.

[0082] Step 3: Perform pressure filtration on the titanium niobium oxide powder: Use a filtration tank to perform pressure filtration on the ball-milled titanium niobium oxide powder. The filtration pressure is 0.3 MPa, the filtration accuracy of the filter paper is 0.45 μm, filter 1 pot, and the pressure filtration time is 30 min. The pressure filtration is completed when the water loss rate reaches 10%, and collect the anhydrous ethanol flowing out during pressure filtration.

[0083] Step 4: Perform drying treatment on the titanium niobium oxide powder: The titanium niobium oxide powder with a water loss rate of 10% obtained after pressure filtration is dried in an oven. The powder needs to be leveled with a spatula. After baking in the oven at 70°C for 30 min, it is broken with a glass rod, and then the temperature is raised to 120°C and baked for 1.5 h; Take 20 g of the baked powder for water loss rate test and whiteness test. The water loss rate is 0%, the whiteness is 84, and the BET test is 0.601 m 2 / g.

[0084] The samples of Examples 1-4 and Comparative Examples 1-4 are made into soft-pack batteries: Add the titanium niobium oxide powder to N-methylpyrrolidone to make a slurry. The slurry is coated on aluminum foil, and after drying and pressing, a positive electrode plate with a thickness of 150 μm is obtained. Use a lithium sheet as the negative electrode plate. Stack the made positive electrode plate, negative electrode plate, and separator in a Z-shaped lamination method, and obtain a soft-pack battery through processes such as welding, liquid injection, pre-charging, second sealing, and formation, and conduct backend testing. The test results are shown in Table 1.

[0085] Table 1

[0086]

[0087] As shown in Table 1, in Comparative Example 1, due to the too low annealing temperature, the flame-synthesized titanium niobium oxide could not be transformed from amorphous powder into monoclinic phase powder. Although smaller particle sizes could still be obtained after ball milling, the electrochemical performance of the titanium niobium oxide powder was poor, which was not conducive to its application in lithium batteries. In Comparative Example 2, due to the large oxygen flow rate during the annealing process, the final particle size of the powder was too large, and the particle size distribution was wider compared to Examples 1-3. The electrochemical performance of the obtained titanium niobium oxide powder was also poor. In Comparative Example 3, due to the large ball-to-material ratio in ball milling, the powder was not completely broken, which also resulted in too large particle size of the final titanium niobium oxide powder. In Comparative Example 4, due to the too large particle size of the flame-synthesized titanium niobium oxide powder, even with the same post-treatment means, the powder with the target particle size could not be obtained, and the electrochemical performance of the titanium niobium oxide powder was poor.

[0088] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A post-treatment method for flame-synthesized titanium niobium oxide powder, characterized in that: The steps include: Step 1: The titanium niobium oxide powder prepared by flame synthesis is an amorphous powder with a particle size D50 of 0.9-3 μm and a D90 of 10-15 μm; the powder is annealed in an oxygen atmosphere with an oxygen flow rate of 3-5 L / min, an annealing temperature of 1000-1200° C., and a holding time of 2-3 h to obtain a monoclinic phase powder; Step 2: ball milling to crush the hollow sphere particles in the monoclinic phase powder, with a ball-to-material ratio of 1:1-3 and a ball milling speed of 100-500r / min; Step 3: Perform filter pressing and drying to obtain post-treated titanium niobium oxide powder.

2. The post-treatment method of flame synthesized titanium niobium oxide powder according to claim 1, characterized in that: The impurity content of the titanium niobium oxide powder prepared by the flame synthesis method is 3-6wt%.

3. The post-treatment method of flame synthesized titanium niobium oxide powder according to claim 1, characterized in that: The heating rate of the annealing is 10-20°C / min.

4. The post-treatment method of flame synthesized titanium niobium oxide powder according to any one of claims 1 to 3, characterized in that: The annealing conditions are: heating from room temperature to 1000° C. at a heating rate of 10-20° C. / min, keeping the temperature for 2-3 hours, and then cooling to room temperature.

5. The post-treatment method of flame synthesized titanium niobium oxide powder according to claim 1, characterized in that: The ball milling time is 1-3h.

6. The post-treatment method of flame synthesized titanium niobium oxide powder according to claim 1, characterized in that: The pressure of the filter press is 0.2-0.5 MPa, and the time is 20-60 min.

7. The post-treatment method of flame synthesized titanium niobium oxide powder according to claim 1, 5 or 6, characterized in that: The drying temperature is 60-150° C. and the drying time is 1-4 hours.

8. The post-treatment method of flame synthesized titanium niobium oxide powder according to claim 1, characterized in that: The particle size D50 of the post-treated titanium niobium oxide powder is 300-600nm, and D90 is 800-1200nm.

9. Use of the post-treated titanium niobium oxide powder obtained by the method according to any one of claims 1 to 8 in a lithium battery.

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