Method for preparing titanium niobate material with assistance of ice crystal guiding-salting-out and application

Abstract

The invention discloses a method for preparing a titanium niobate material with assistance of ice crystal guiding and salting-out and application, and belongs to the field of secondary batteries. According to the specific scheme, the method comprises the following steps that firstly, niobium pentachloride and tetrabutyl titanate are dissolved in absolute ethyl alcohol, a salting-out agent and a conductive additive are added into the absolute ethyl alcohol, and the mixture is mixed to be uniform to obtain a precursor solution; 2, freezing the precursor solution, and then carrying out vacuum drying treatment; and calcining for 4-6 hours at the temperature of 800-1000 DEG C under the protection of inert gas to obtain the titanium niobate material. The microstructure of the material is regulated and controlled through an innovative process, the electronic and ionic conductivity is remarkably improved, the electrochemical performance of the material under the high-rate condition is improved, and technical support is provided for wide application of titanium niobate in the field of energy storage.

Description

Technical Field

[0001] This invention belongs to the field of secondary batteries, specifically relating to a method for preparing highly oriented titanium niobate materials using ice crystal guiding combined with salting-out assisted methods, and its application in energy storage batteries and other fields. Background Technology

[0002] In modern society, with the rapid development of technology, energy storage technology is crucial for ensuring the stable operation of various electronic devices, electric vehicles, and large-scale grid energy storage. As the mainstream energy storage device, the performance of lithium-ion batteries directly impacts the development of related industries. Currently, the market is placing increasingly higher demands on lithium-ion batteries in terms of energy density, charge / discharge rate, cycle life, and low-temperature performance.

[0003] While graphite is widely used in traditional lithium-ion battery anode materials, its inherent low lithium plating potential makes it highly susceptible to lithium dendrite formation during battery charging and discharging. The growth of lithium dendrites not only leads to internal short circuits, causing rapid capacity decay and shortened cycle life, but in severe cases, it can also puncture the battery separator, causing electrolyte leakage and potentially resulting in fires, explosions, and other safety accidents. This significantly limits the application of lithium-ion batteries in fields with extremely high safety and stability requirements.

[0004] Compared to traditional anodes, titanium niobate (TiNb2O7, TNO) materials exhibit a high performance of 387.6 mA hg. -1 The theoretical specific capacitance, while its operating potential is approximately 1.6 V vs Li + Lithium niobate (TiNiO) can effectively suppress lithium dendrite formation and offers advantages in safety and cycle stability, making it an ideal new choice for achieving high-power, long-life lithium-ion batteries. However, titanium niobate materials obtained under conventional preparation conditions exhibit diverse internal crystal forms and disordered structures, hindered electronic conduction pathways, and complex and lengthy ion diffusion paths, resulting in low electronic and ionic conductivity. This problem prevents batteries from fully realizing their theoretical specific capacity under high-rate charge / discharge and low-temperature environments, leading to rapid capacity decay and a sharp decline in performance, failing to meet the demands of rapid response and stable low-temperature operation in practical applications. Therefore, developing a novel preparation process that can effectively regulate the internal structure of titanium niobate materials, improve their electronic and ionic conductivity, and thus enhance battery performance under various operating conditions has become a critical issue urgently needing to be addressed in the current lithium-ion battery field.

[0005] Cryo casting, a preparation technique based on the solidification properties of materials at low temperatures, has emerged as a promising field in the preparation of functional materials in recent years. This technique primarily utilizes the directional crystallization of solvents at low temperatures, displacing solutes into the interstitial spaces between ice crystals, thereby inducing the ordered arrangement of solute particles and forming materials with unique microstructures. Its unique preparation principle provides a new approach for obtaining high-performance materials with directional channels and gradient structures. Introducing cryo casting technology into the preparation of titanium niobate materials holds promise for overcoming the limitations of traditional preparation processes and solving problems such as disordered internal structure and low electrical conductivity. Summary of the Invention

[0006] Based on the above technical background, this invention provides a method for preparing highly oriented titanium niobate materials with ice crystal guidance-salting out assistance and its application in the field of energy storage. The aim is to significantly improve the electronic and ionic conductivity and enhance the electrochemical performance of the material under high-rate conditions by controlling the microstructure of the material through innovative processes, thereby providing technical support for the widespread application of titanium niobate in the field of energy storage.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing titanium niobate materials by ice crystal guidance and salting out includes the following steps:

[0009] Step 1: Dissolve niobium pentachloride and tetrabutyl titanate in anhydrous ethanol, and add salting-out agent and conductive additive. Stir for 1-2 hours to ensure homogeneity. Vacuum filter the resulting solution to remove impurities, and then process the solution in a high-pressure homogenizer to obtain the driving solution.

[0010] Step 2: Pour the precursor solution into a shallow stainless steel dish lined with polytetrafluoroethylene, place it in a freezing chamber, control the freezing rate to promote the directional growth of ice crystals, and then transfer the frozen sample to a vacuum drying oven for low-temperature vacuum drying to allow the ice crystals to fully sublimate. After drying, place the sample in a muffle furnace and calcine it at 800-1000℃ for 4-6 hours under inert gas protection, and then allow it to cool naturally to obtain titanium niobate material.

[0011] In step one, the concentration of niobium ions in the precursor solution is 0.1 ~ 0.5 mol / L, preferably 0.3 mol / L, and the molar ratio of niobium to titanium is 1:2 ~ 1:4, preferably 1:2.

[0012] In step one, niobium pentachloride and tetrabutyl titanate are dissolved in anhydrous ethanol to form a single-component solution. Then, the anhydrous ethanol solution of tetrabutyl titanate is slowly added dropwise to the anhydrous ethanol solution of niobium pentachloride at 50-60°C.

[0013] In step one, the salting-out agent includes one or more of ammonium chloride, ammonium carbonate, ammonium sulfate, and sodium citrate, and its addition amount is 5% to 15% of the total mass of niobium pentachloride and tetrabutyl titanate. The conductive additive includes one or more of carbon-based materials such as carbon nanotubes, carbon fibers, and graphene nanosheets, and its addition amount is 2% to 5% of the total mass of niobium pentachloride and tetrabutyl titanate.

[0014] In step one, the solution containing the salting-out agent and conductive additive is subjected to high-pressure homogenization in a high-pressure homogenizer to make the precursor solution clear and transparent without visible particulate impurities, thus ensuring the uniformity of the subsequent crystallization process. Preferably, the pressure of the high-pressure homogenization is 50-100 MPa, and the number of cycles is 3-5.

[0015] In step two, the specific steps of the freezing treatment are as follows: first, rapidly cool down to -10~-20℃ at a rate of -10~-20℃ / min to promote the formation of a large number of crystal nuclei, and then slowly cool down to -80~-90℃ at a rate of -5~-10℃ / h for 6~12 hours to allow ice crystals to grow in a directional manner, preferably 8 hours.

[0016] In step two, during the freezing process, a uniform magnetic field with a magnetic induction intensity of 0.5-1T parallel to the bottom surface is set around the container containing the precursor solution to assist in the directional alignment of the precursor.

[0017] In step two, the vacuum drying process is as follows: first, dry at -10℃ and a vacuum degree below 10Pa for 12 hours; then, heat to 20℃ at a rate of 1~10℃ / h and dry for 6 hours.

[0018] In step two, the calcination process first involves purging the air with high-purity argon gas for 10-30 minutes. During the heating process, the flow rate is switched to a mixture of argon and hydrogen gas with a volume ratio of 9:1 and a flow rate of 20-50 mL / min to promote crystallization. During the heat preservation stage, 20-50 mL / min of high-purity argon gas is introduced to prevent oxidation. The preferred heat preservation temperature is 800℃.

[0019] An application of titanium niobate prepared by the method, wherein the titanium niobate is used as a negative electrode material for lithium-ion batteries.

[0020] The prepared titanium niobate material, used as the negative electrode active material, is dispersed in a solvent along with a conductive agent and a binder to obtain a negative electrode slurry. This slurry is then coated onto a negative electrode current collector, and after drying, rolling, and punching, a negative electrode sheet is obtained. The binder is polyvinylidene fluoride (PVDF), the conductive agent is acetylene black, and the solvent is N-methylpyrrolidone (NMP). The mass ratio of negative electrode active material: conductive agent: binder is 80%~90%:5%~10%:5%~10%.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1) The titanium niobate material prepared by this invention is arranged and crystallized in an orderly manner along the ice crystal growth direction, forming a highly oriented lamellar structure. This suppresses lattice distortion during lithium insertion / extraction, significantly improving the structural stability of the material. Simultaneously, the salting-out agent, by adjusting the ionic strength, suppresses the formation of non-oriented crystal nuclei, strengthens the directional crystallization kinetics, and creates continuous, interconnected ion transport channels within the material. This reduces the tortuosity of the ion diffusion path and greatly improves the lithium-ion diffusion coefficient.

[0023] 2) The conductive additives added in this method are directionally adsorbed at the grain boundaries of titanium niobate during the salting-out process, forming a three-dimensional conductive network, which significantly improves the electronic conductivity of the material.

[0024] 3) In this method, the salting-out agents such as ammonium sulfate induce a multi-level porous structure within the titanium niobate particles through decomposition during calcination. Mesopores provide more active sites, increasing lithium-ion adsorption capacity, while macropores effectively buffer volume expansion during charge and discharge. Furthermore, the porous structure enhances electrolyte wettability and accelerates interfacial reaction kinetics. Attached Figure Description

[0025] Figure 1 This is the XRD pattern of a titanium niobate (TiNb2O7) electrode material prepared in Example 1;

[0026] Figure 2 This is a comparison chart of the rate performance of a titanium niobate (TiNb2O7) electrode material prepared in Example 1 and a titanium niobate (TiNb2O7) electrode material prepared by solid-state method at 0°C. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Example 1:

[0029] A method for preparing titanium niobate anode materials by ice crystal guidance and salting out includes the following steps:

[0030] Step 1: Dissolve 1.35g of niobium pentachloride in 100mL of anhydrous ethanol and stir magnetically at 60℃ for 30min until clear and transparent. Separately, dissolve 3.4g of tetrabutyl titanate in 200mL of anhydrous ethanol, and then slowly add it dropwise to the niobium pentachloride solution while simultaneously turning on 40kHz ultrasound (power 200W) and stirring continuously for 2h to form a homogeneous solution. Then, add 0.475g of ammonium sulfate (10% of the total precursor mass) and 0.14255g of graphene nanosheets (3% of the total precursor mass) to the obtained solution, stir at 25℃ for 1h, and then circulate the solution three times at 100MPa pressure in a high-pressure homogenizer to obtain the precursor solution.

[0031] Step 2: Pour the precursor solution into a shallow stainless steel dish lined with polytetrafluoroethylene. First, rapidly cool it to -10℃ at a rate of -10℃ / min, and then slowly cool it to -80℃ at a rate of -5℃ / h. During the freezing process, apply a uniform magnetic field of 0.5T parallel to the bottom of the dish.

[0032] Step 3: The frozen sample was vacuum dried at -10℃ for 12 hours, then heated to 20℃ at a rate of 5℃ / h for 6 hours. It was then transferred to a muffle furnace, initially purged with high-purity argon (50 mL / min) for 30 minutes, and then heated to a 9:1 argon-hydrogen mixture (30 mL / min). The mixture was held at 800℃ for 4 hours, and after natural cooling, it was ground to obtain titanium niobate material. The XRD pattern of the titanium niobate material prepared by this method is shown below. Figure 1 As shown.

[0033] The highly oriented titanium niobate material obtained in this embodiment is applied to the anode of a low-temperature fast-charging lithium-ion battery to improve the battery's cycle stability and rate performance at low temperatures.

[0034] The prepared titanium niobate anode material, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 85:6:9, and N-methylpyrrolidone (NMP) was added to prepare a uniform slurry with a solid content of 30%. The slurry was uniformly coated onto a copper foil current collector, dried, and punched into circular electrode sheets with a diameter of 12 mm. These were then assembled into coin cells, and electrochemical tests were subsequently performed.

[0035] The rate performance of the titanium niobate material obtained in this embodiment and the titanium niobate material obtained by the ordinary solid-state method were tested at 0°C. The test structure is as follows. Figure 2 As shown, the discharge specific capacity of titanium niobate prepared by the ice crystal method at 1C is 195.52 mAh g. -1 Superior to solid-phase titanium niobate (179.67 mAh g) -1 Meanwhile, it exhibits a capacity of 158.72 mAh / g at an ultra-high charge / discharge rate of 15C. -1 The discharge specific capacity demonstrates excellent low-temperature, high-rate performance.

[0036] Example 2

[0037] The difference between the preparation method of titanium niobate material in this embodiment and that in Example 1 is that: ammonium sulfate is replaced with ammonium chloride (accounting for 8% of the total mass of the precursor), and its low-temperature decomposition characteristics are used to control the porous structure; the conductive additive is replaced with carbon nanotubes (CNTs) accounting for 2% of the total mass of the precursor, and CNTs are uniformly wound on the surface of titanium niobate nanorods through high-pressure homogenization; the remaining parameters are the same as in Example 1.

[0038] Example 3

[0039] The difference between the preparation method of titanium niobate material in this embodiment and that in Example 1 is that ammonium sulfate (8% of the total mass of the precursor) and sodium citrate (5% of the total mass of the precursor) are compounded to inhibit the aggregation of niobium titanium ions by utilizing the coordination effect of sodium citrate; all other parameters are the same as in Example 1.

[0040] Example 4

[0041] The difference between the preparation method of titanium niobate material in this embodiment and that in Example 1 is that: the freeze crystallization process is first rapidly cooled to -10℃ at a rate of -20℃ / min, and then slowly cooled to -80℃ at a rate of -5℃ / h; a uniform magnetic field of 0.5T parallel to the bottom of the plate is applied during the freezing process; all other parameters are the same as in Example 1.

[0042] Example 5

[0043] The difference between the preparation method of titanium niobate material in this embodiment and that in Example 1 is that: during the freeze crystallization process, the temperature is first rapidly reduced to -20°C at a rate of -10°C / min, and then slowly reduced to -90°C at a rate of -5°C / h; a uniform magnetic field of 0.5T parallel to the bottom of the plate is applied during the freezing process; all other parameters are the same as in Example 1.

[0044] Example 6

[0045] The difference between the preparation method of titanium niobate material in this embodiment and that in Example 1 is that: during the freeze crystallization process, the temperature is first rapidly reduced to -10℃ at a rate of -10℃ / min, and then slowly reduced to -80℃ at a rate of -5℃ / h; a uniform magnetic field of 1T parallel to the bottom of the plate is applied during the freezing process; all other parameters are the same as in Example 1.

[0046] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing titanium niobate materials by ice crystal guidance and salting out, characterized in that, Includes the following steps: Step 1: Dissolve niobium pentachloride and tetrabutyl titanate in anhydrous ethanol, and add salting-out agent and conductive additive to it, and mix well to obtain a precursor solution. Step 2: Freeze the precursor solution and then vacuum dry it; calcine it at 800-1000℃ for 4-6 hours under inert gas protection to obtain titanium niobate material.

2. The method according to claim 1, characterized in that: In step one, the concentration of niobium ions in the precursor solution is 0.1~0.5 mol / L, and the molar ratio of niobium to titanium is 1:2~1:

4.

3. The method according to claim 1, characterized in that: In step one, niobium pentachloride and tetrabutyl titanate are dissolved in anhydrous ethanol to form a single-component solution. Then, the anhydrous ethanol solution of tetrabutyl titanate is slowly added dropwise to the anhydrous ethanol solution of niobium pentachloride at 50-60°C.

4. The method according to claim 1, characterized in that: In step one, the salting-out agent includes one or more of ammonium chloride, ammonium carbonate, ammonium sulfate, and sodium citrate, and its addition amount is 5% to 15% of the total mass of niobium pentachloride and tetrabutyl titanate. The conductive additive includes one or more of carbon nanotubes, carbon fibers, and graphene nanosheets, and its addition amount is 2% to 5% of the total mass of niobium pentachloride and tetrabutyl titanate.

5. The method according to claim 1, characterized in that: In step one, the solution containing the salting-out agent and conductive additive is subjected to high-pressure homogenization in a high-pressure homogenizer to make the precursor solution clear and transparent without visible particulate impurities, so as to ensure the uniformity of the subsequent crystallization process.

6. The method according to claim 1, characterized in that: In step two, the specific steps of the freezing treatment are as follows: first, rapidly cool down to -10~-20℃ at a rate of -10~-20℃ / min to promote the formation of a large number of crystal nuclei, and then slowly cool down to -80~-90℃ at a rate of -5~-10℃ / h for 6~12 hours to allow ice crystals to grow in a directional manner.

7. The method according to claim 1, characterized in that: In step two, during the freezing process, the precursor solution is placed in a uniform magnetic field parallel to the bottom surface with a magnetic induction intensity of 0.5-1T to assist the precursor in oriented alignment.

8. The method according to claim 1, characterized in that: In step two, the vacuum drying process is as follows: first, dry at -10℃ and a vacuum degree below 10Pa for 12 hours; then, heat to 20℃ at a rate of 1~10℃ / h and dry for 6 hours.

9. The method according to claim 1, characterized in that: In step two, the calcination process first involves purging the air with high-purity argon gas. During the heating process, the flow rate is switched to a mixture of argon and hydrogen gas with a volume ratio of 9:1 and a flow rate of 20-50 mL / min to promote crystallization. During the heat preservation stage, 20-50 mL / min of high-purity argon gas is introduced to prevent oxidation, and the heat preservation temperature is 800℃.

10. An application of titanium niobate prepared by the method of any one of claims 1-9, characterized in that: Titanium niobate is used as a negative electrode material for lithium-ion batteries.

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