Preparation and application of titanium dioxide / sodium titanate / carbon composite material

Abstract

The application belongs to the technical field of electrode materials, and particularly discloses a preparation and application of a titanium dioxide / sodium titanate / carbon composite material, which comprises the following steps: preparing a graphene oxide aqueous solution and a sodium hydroxide solution; taking the sodium hydroxide solution, adding tetrabutyl titanate, and performing a hydrothermal reaction; cooling to room temperature, centrifuging and washing with water for three times, and vacuum drying; taking deionized water, adding tetrabutyl titanate, and performing a hydrothermal reaction; cooling to room temperature, centrifuging and washing with water for three times, and vacuum drying; adding a sodium titanate precursor and a titanium dioxide precursor into the graphene oxide aqueous solution, fully stirring, centrifuging, and drying; and placing in a tube furnace and performing a heat treatment under inert gas conditions. The preparation and application of the titanium dioxide / sodium titanate / carbon composite material can solve the problem of insufficient chemical kinetic characteristics of existing titanium-based sodium ion battery negative electrode materials.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, specifically relating to the preparation and application of a titanium dioxide / sodium titanate / carbon composite material. Background Technology

[0002] Titanium, as the all-around champion of the metal world, has compounds widely used in various industries. Titanium dioxide (TiO2) and sodium titanate (Na2Ti3O7), as electrode materials, have been extensively studied in the field of secondary ion batteries in recent years. Currently, researchers mainly improve their electrochemical performance through nanostructure design, doping modification, and composite material preparation. For example, increasing specific surface area and ion diffusion rate by preparing nanowires, nanotubes, or mesoporous structures; improving conductivity and structural stability by doping with nitrogen, carbon, or other metal elements; or enhancing electron transport capability by compositing with carbonaceous materials. Sodium titanate, due to its open layered structure and high theoretical specific capacity, is considered a promising anode material for sodium-ion batteries. Researchers improve its cycle stability and rate performance by controlling morphology, optimizing synthesis processes, and surface modification. However, existing technologies still have some problems. First, the theoretical specific capacity of titanium dioxide is relatively low (approximately 335 mAh g⁻¹). -1 Sodium titanate has poor conductivity, limiting its application in high-energy-density batteries. Furthermore, it is prone to structural collapse and volume expansion during charge and discharge, leading to insufficient cycle stability. Further optimization of the material structure, development of low-cost preparation processes, and exploration of its performance in practical battery systems are essential for promoting its industrial application.

[0003] Therefore, there is a need in the field to develop a method for preparing and applying a titanium dioxide / sodium titanate / carbon composite material that can effectively solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing and applying a titanium dioxide / sodium titanate / carbon composite material, which can solve the problem of insufficient chemical kinetic properties in existing titanium-based sodium-ion battery anode materials.

[0005] To achieve the above objectives, the present invention provides a method for preparing a titanium dioxide / sodium titanate / carbon composite material, comprising the following steps:

[0006] Step S1: Prepare an aqueous solution of graphene oxide and a sodium hydroxide solution;

[0007] Step S2: Take 40-70 mL of sodium hydroxide solution and add tetrabutyl titanate to make the volume concentration of tetrabutyl titanate 0.05-0.22 g / mL. -1 Too low a concentration will result in insufficient crystallinity of sodium titanate, while too high a concentration will prevent complete hydrolysis of sodium titanate, thus hindering the hydrothermal reaction.

[0008] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with deionized centrifuged water. Then, it was vacuum dried at 60°C for 12 hours to obtain the sodium titanate precursor.

[0009] Step S3: Take 40-70 mL of deionized water and add tetrabutyl titanate to make the tetrabutyl titanate concentration 0.05-0.22 g / mL. -1 Too low a concentration will result in insufficient crystallinity of titanium dioxide, while too high a concentration will prevent complete hydrolysis of sodium titanate, thus hindering the hydrothermal reaction.

[0010] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with deionized water by centrifugation. Then, it was vacuum dried at 60°C for 12 hours to obtain the titanium dioxide precursor.

[0011] Step S4: Add sodium titanate precursor and titanium dioxide precursor to the graphene oxide aqueous solution, and adjust the mass concentration of both sodium titanate precursor and titanium dioxide precursor to 1-4 mg / mL. -1 The concentration of the suspension is too low, which reduces the sample preparation cycle; the concentration is too high, which affects the concentration of titanium dioxide and sodium titanate. Stir thoroughly for 12-24 hours, then centrifuge and vacuum dry at 60℃ for 12 hours.

[0012] Step S5: Place the material in a tube furnace and perform heat treatment under inert gas conditions to ensure the effective retention of carbonaceous materials during carbonization. If an oxidizing atmosphere is present, the carbonaceous materials will turn into oxides and disappear. This yields a titanium dioxide / sodium titanate / carbon composite material.

[0013] The obtained titanium dioxide / sodium titanate / carbon composite material has the following characteristics:

[0014] 1) Size characteristics:

[0015] Titanium dioxide / sodium titanate / carbon composites are nanocomposite materials, and graphene is a nanoscale carbonaceous material. Supporting nanoscale titanium dioxide / sodium titanate heterostructures on a carbonaceous substrate can provide more channels for electron transport in electrode materials. Nanomaterials can provide more active sites, which enhances the electrochemical stability of the electrode material. To fully utilize the electrochemical activity of titanium dioxide / sodium titanate, the carbonaceous substrate content is best controlled below 20%.

[0016] 2) Structural and performance characteristics:

[0017] Titanium dioxide and sodium titanate achieve energy storage through intercalation reaction, resulting in large volume strain during the electrochemical reaction. Graphene mainly achieves energy storage through ion adsorption / desorption, thus exhibiting excellent electrochemical stability. The synergistic effect of the two constituent unit materials gives it high capacity and long cycle performance.

[0018] 3) Process characteristics: The composite material is obtained by combining the hydrothermal method, which is a traditional method, simple process and easy to implement.

[0019] 5) Cost characteristics: The main components of the titanium dioxide / sodium titanate / carbon composite material are titanium dioxide, sodium titanate, and graphene. Titanium is a conventional transition metal with high abundance in the Earth's crust, and carbon is a human-friendly element. Therefore, developing related technologies for their composite materials has advantages in improving the electrochemical performance of the composite materials and reducing the cost of electrode materials.

[0020] Preferably, in step S1, the concentration of the graphene oxide aqueous solution is 2-5 mg / mL. If the mass concentration of graphene oxide is too low, the dispersion of titanium dioxide and sodium titanate will be insufficient. If the concentration is too high, the carbon content of the composite material will increase, resulting in a decrease in the electrochemical activity of the composite material.

[0021] The concentration of the sodium hydroxide solution is 9-12 mol / L. -1 Too low a concentration of sodium hydroxide will affect the crystallinity of sodium titanate, while too high a concentration will result in a waste of sodium hydroxide.

[0022] Preferably, in step S2, the hydrothermal reaction temperature is 160-200℃ and the hydrothermal time is 16-24h. If the hydrothermal temperature is too low, the pressure inside the reactor will be insufficient and the crystallinity of the product will be poor. If the temperature is too high, it will increase energy consumption and lead to waste.

[0023] The centrifugation speed is 6000-10000 r / min, and the centrifugation time is 5-10 min;

[0024] In step S3, the hydrothermal reaction temperature is 160-200℃ and the hydrothermal time is 16-24h. If the hydrothermal temperature is too low, the pressure inside the reactor will be insufficient and the crystallinity of the product will be poor. If the temperature is too high, it will increase energy consumption and lead to waste.

[0025] The centrifugation speed is 6000-10000 r / min, and the centrifugation time is 5-10 min;

[0026] In step S4, the centrifugation speed is 6000-10000 r / min, and the centrifugation time is 5-10 min.

[0027] Preferably, in step S5, the inert gas includes, but is not limited to, argon and nitrogen; the heat treatment temperature is 600-900℃, and the heat treatment time is 1-3 hours. If the treatment temperature is too low, the crystallinity of titanium dioxide and sodium titanate will not be complete; if the treatment temperature is too high or the time is too long, it will lead to increased energy consumption and waste of resources, resulting in increased preparation costs.

[0028] The present invention also provides an application of the titanium dioxide / sodium titanate / carbon composite material prepared by the preparation of the titanium dioxide / sodium titanate / carbon composite material in sodium-ion batteries.

[0029] The specific application is as follows: The obtained titanium dioxide / sodium titanate / carbon composite material, conductive carbon black or carbon nanotubes, and polyvinylidene fluoride are mixed evenly in N-methylpyrrolidone at a mass ratio of 7-8.5:2-1:1-0.5, and stirred for 0.2-1 hours until fully homogeneous; the resulting uniform electrode paste is then coated onto copper foil, achieving a loading of 3-12 mg / cm³. 2 If the loading is too low, the cycle stability will be insufficient and there will be no reference value for production. If it is too high, the active material near the current collector will not be able to fully exert its electrochemical activity. Therefore, the loading should be appropriate.

[0030] After coating, place it in a vacuum drying oven and dry at 60-120℃ for 24-48 hours. Then, punch it into a circular electrode sheet with a diameter of 12mm (as the negative electrode) or the corresponding electrode sheet size for card batteries. Finally, in a glove box, combine it with sodium foil to form a two-electrode system battery assembly, which is a CR2025 button cell battery or a corresponding card battery.

[0031] The present invention utilizes the preparation and application of the above-mentioned titanium dioxide / sodium titanate / carbon composite material, and the beneficial effects are as follows:

[0032] 1. The titanium-based composite material of this invention has a high sodium storage capacity. This invention introduces carbon into the composite material, providing favorable conditions for the dispersion and distribution of titanium dioxide and sodium titanate. This significantly increases the specific surface area of ​​the composite material and effectively improves its sodium storage capacity. When the composite material prepared in this invention is used as the active material for sodium-ion batteries, the reversible capacity of the assembled sodium-ion battery reaches 110.8 mAh / g at a current density of 0.05 A / g.

[0033] 2. The composite material in this invention can alleviate the volume strain of titanium dioxide and sodium titanate during electrochemical processes. The introduction of graphene provides abundant electron transport channels and has a positive effect on the dispersion and distribution of titanium dioxide and sodium titanate. The unique spatial structure of sheet-like sodium titanate carrying titanium dioxide on the graphene surface provides abundant active sites and a stable electrochemical structure for carrier adsorption / desorption and insertion / extraction, while effectively mitigating the volume expansion of electrode materials during electrochemical reactions.

[0034] 3. The composite material in this invention exhibits good electrochemical structural stability, resulting in electrode sheets with excellent cycle performance. The microstructure and intrinsic properties of a material determine its electrochemical performance. The titanium dioxide / sodium titanate / carbon composite material integrates the advantages of the monomer structure and performance of titanium dioxide, sodium titanate, and graphene. The introduction of sodium titanate enriches the effective electrochemical sites of titanium dioxide, while the introduction of graphene provides reaction sites and transport channels for charge carriers. Through structural regulation of the composite material, the transport dynamics of sodium ions are improved, enhancing the reversibility of the electrochemical reaction of the electrode material, resulting in a sodium-ion battery with excellent cycle performance. When the current density is 0.1 Ag... -1 At that time, after 1000 cycles, the reversible capacity retention rate reached 83.6%.

[0035] 4. The composite material in this invention exhibits good reversibility, resulting in excellent rate performance of the prepared electrode active material. The titanium dioxide / sodium titanate / carbon composite material demonstrates better structural stability and richer electron migration channels than the titanium dioxide / sodium titanate composite material. This improves the thermodynamic stability and ion insertion / extraction kinetics of the electrode material, thereby accelerating ion / electron transport and increasing the specific capacity of the composite electrode material. The rate performance curves show that at 0.05, 0.1, 0.3, 0.5, 0.8, 1.0, 5.0, and 10.0 Ag... -1 At the specified current density, the specific capacity of the titanium dioxide / sodium titanate / carbon composite material reached as high as 546.21 mAh g⁻¹. -1 492.61mAh g -1 425.21mAh g -1 368.91mAh g -1 295.11mAh g -1 209.21mAhg -1 157.61mAh g -1 98.1mAh g -1 And then back to a low current density of 0.3Ag -1 Under these conditions, the capacity shows almost no decay, which again demonstrates that the obtained titanium dioxide / sodium titanate / carbon composite material has good electrochemical reversibility.

[0036] 5. The preparation steps of this invention are simple, the reaction conditions are mild and easy to control, and the raw materials used are low-cost, making it suitable for large-scale production. The hydrothermal reaction used in the preparation process of the composite material can be completed in a common forced-air drying oven, and all heat treatment processes are carried out in a tube furnace at medium to low temperatures. The equipment is conventional and there are no overly harsh conditions, which makes it possible for conventional chemical plants to have ton-scale reactors for large-scale production. The matrix material in the composite material is carbon, which ensures its low cost and environmental friendliness. The transition metal titanium is a conventional non-strategic resource metal with excellent environmental friendliness, which also creates favorable conditions for the large-scale production of this composite material.

[0037] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0038] Figure 1 This is a SEM image of the titanium dioxide / sodium titanate / carbon composite material prepared in Example 1 of the preparation and application of the titanium dioxide / sodium titanate / carbon composite material of the present invention.

[0039] Figure 2 The image shows the XRD pattern of the titanium dioxide / sodium titanate / carbon composite material prepared in Example 1 of the preparation and application of the titanium dioxide / sodium titanate / carbon composite material of the present invention.

[0040] Figure 3 Example 1 of the preparation and application of a titanium dioxide / sodium titanate / carbon composite material of the present invention shows the titanium dioxide / sodium titanate / carbon composite material and the thermogravimetric curve of titanium dioxide / sodium titanate.

[0041] Figure 4 The constant current charge-discharge curves of titanium dioxide / sodium titanate / carbon composite material in Example 1 of the preparation and application of the present invention are shown.

[0042] Figure 5 The constant current charge-discharge curves of titanium dioxide / sodium titanate in Example 1 of the preparation and application of a titanium dioxide / sodium titanate composite material of the present invention are shown.

[0043] Figure 6 The rate performance curve of titanium dioxide / sodium titanate / graphene in Example 1 of the preparation and application of a titanium dioxide / sodium titanate / carbon composite material of the present invention is shown.

[0044] Figure 7 The cycling performance curves of titanium dioxide / sodium titanate / graphene in Example 1 of the preparation and application of a titanium dioxide / sodium titanate / carbon composite material of the present invention are shown.

[0045] Figure 8This is a SEM image of the titanium dioxide / sodium titanate / carbon composite material prepared in Example 2 of the preparation and application of the titanium dioxide / sodium titanate / carbon composite material of the present invention.

[0046] Figure 9 This is a SEM image of the titanium dioxide / sodium titanate / carbon composite material prepared in Example 3 of the preparation and application of the titanium dioxide / sodium titanate / carbon composite material of the present invention.

[0047] Figure 10 This is a SEM image of the titanium dioxide / sodium titanate / carbon composite material prepared in Comparative Example 1, which is used in the preparation and application of the titanium dioxide / sodium titanate / carbon composite material of the present invention.

[0048] Figure 11 This is a SEM image of the titanium dioxide / sodium titanate / carbon composite material prepared in Comparative Example 2, which is a preparation and application of the titanium dioxide / sodium titanate / carbon composite material of the present invention. Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0050] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0051] Example 1

[0052] The preparation of a titanium dioxide / sodium titanate / carbon composite material includes the following steps:

[0053] Step S1: Prepare an aqueous solution of graphene oxide with a concentration of 3.5 mg / mL and a concentration of 10 mol / L. -1 Sodium hydroxide solution;

[0054] Step S2: Take 50 mL of sodium hydroxide solution and add tetrabutyl titanate to make the volume concentration of tetrabutyl titanate 0.15 g / mL. -1 A hydrothermal reaction was carried out at a temperature of 180℃ for 20 hours.

[0055] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with water by deionization centrifugation (parameters 8000 r / min, 8 min). Then, it was vacuum dried at 60 °C for 12 h to obtain the sodium titanate precursor.

[0056] Step S3: Take 50 mL of deionized water and add tetrabutyl titanate to make the tetrabutyl titanate concentration 0.15 g / mL. -1 A hydrothermal reaction was carried out at a temperature of 180℃ for 20 hours.

[0057] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with deionized water by centrifugation (parameters 8000 r / min, 8 min). Then, it was vacuum dried at 60 °C for 12 h to obtain the titanium dioxide precursor.

[0058] Step S4: Add sodium titanate precursor and titanium dioxide precursor to the graphene oxide aqueous solution, and adjust the mass concentration of both sodium titanate precursor and titanium dioxide precursor to 3 mg / mL. -1 The suspension was stirred thoroughly for 18 hours, then centrifuged (8000 r / min, 8 min), and then vacuum dried at 60°C for 12 hours.

[0059] Step S5: Place the material in a tube furnace and perform heat treatment under inert gas (argon or nitrogen) conditions at a temperature of 800℃ for 2 hours. This yields the titanium dioxide / sodium titanate / carbon composite material.

[0060] like Figure 1 As shown, the titanium dioxide / sodium titanate heterostructure is relatively uniformly dispersed on the graphene surface, and the sodium titanate particles are about 30 nm in size.

[0061] like Figure 2 As shown, a titanium dioxide / sodium titanate / carbon composite material was successfully synthesized.

[0062] like Figure 3 As shown, the graphene content in the composite material is approximately 5.4% by mass. The preparation process of titanium dioxide / sodium titanate is as follows: no graphene is involved throughout the process, and other parameters and operations are the same as in Example 1.

[0063] Electrode preparation / battery assembly: The obtained titanium dioxide / sodium titanate / carbon composite material, conductive carbon black, and polyvinylidene fluoride were mixed uniformly in N-methylpyrrolidone at a mass ratio of 7:2:1 and stirred for 0.5 h. The resulting uniform electrode slurry was coated onto copper foil, achieving a loading of 4 mg / cm³. 2 After preparation, the electrode is dried in a vacuum drying oven at 60°C for 12 hours and then punched into a circular electrode sheet with a diameter of 12 mm. In a glove box, it is matched with a sodium metal two-electrode battery system, model CR2025, with a voltage test range of 0.01-3V.

[0064] like Figures 4-5 As shown, after the third cycle, the curves overlap and the performance begins to stabilize. This is due to the formation of the SEI film, and the charge / discharge plateau of this material is approximately 0.59V.

[0065] like Figure 6 As shown, at a current density of 0.05Ag -1 0.1Ag -1 0.3Ag -10.5Ag -1 0.8Ag -1 1.0Ag -1 3.0Ag -1 5.0Ag -1 The reversible capacity can reach 546.2 mAh g. -1 492.6mAh g -1 425.2mAh g -1 368.9mAhg -1 295.1mAh g -1 209.2mAh g -1 157.6mAh g -1 98.1mAh g -1 .

[0066] like Figure 7 As shown, after 1000 cycles, the capacity retention rate reached 83.6%. This demonstrates that the titanium dioxide / sodium titanate / carbon electrode material battery prepared in this embodiment exhibits good cycle stability.

[0067] Example 2

[0068] The preparation of a titanium dioxide / sodium titanate / carbon composite material includes the following steps:

[0069] Step S1: Prepare an aqueous solution of graphene oxide with a concentration of 5 mg / mL and a concentration of 12 mol / L. -1 Sodium hydroxide solution;

[0070] Step S2: Take 70 mL of sodium hydroxide solution and add tetrabutyl titanate to make the volume concentration of tetrabutyl titanate 0.22 g / mL. -1 A hydrothermal reaction was carried out at a temperature of 200℃ for 24 hours.

[0071] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with water by deionization centrifugation (parameters 10000 r / min, 10 min). Then, it was vacuum dried at 60 °C for 12 h to obtain the sodium titanate precursor.

[0072] Step S3: Take 70 mL of deionized water and add tetrabutyl titanate to make the tetrabutyl titanate concentration 0.22 g / mL. -1 A hydrothermal reaction was carried out at a temperature of 200℃ for 24 hours.

[0073] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with deionized water by centrifugation (parameters 10000 r / min, 10 min). Then, it was vacuum dried at 60 °C for 12 h to obtain the titanium dioxide precursor.

[0074] Step S4: Add sodium titanate precursor and titanium dioxide precursor to the graphene oxide aqueous solution, and adjust the mass concentration of both sodium titanate precursor and titanium dioxide precursor to 4 mg / mL. -1 The suspension was stirred thoroughly for 24 hours, then centrifuged (parameters 10000 r / min, 10 min), and then vacuum dried at 60℃ for 12 hours.

[0075] Step S5: Place the material in a tube furnace and perform heat treatment under inert gas (argon or nitrogen) conditions at a temperature of 900℃ for 3 hours. This yields the titanium dioxide / sodium titanate / carbon composite material.

[0076] Electrode fabrication / battery assembly:

[0077] The obtained titanium dioxide / sodium titanate / carbon composite material, conductive carbon black, and polyvinylidene fluoride were mixed uniformly in N-methylpyrrolidone at a mass ratio of 8.5:2:0.5 and stirred for 0.5 h. The resulting uniform electrode paste was then coated onto copper foil, achieving a loading of 8 mg / cm³. 2 After preparation, the electrode is dried in a vacuum drying oven at 60°C for 12 hours and then punched into a circular electrode sheet with a diameter of 12 mm. In a glove box, it is matched with a sodium metal two-electrode battery system, model CR2025, with a voltage test range of 0.01-3V.

[0078] like Figure 8 As shown, the dispersion of titanium dioxide / sodium titanate exhibits more severe agglomeration compared to the titanium dioxide / sodium titanate / carbon composite material prepared in Example 1, which is related to the temperature and time of the hydrothermal reaction. When the mass ratio of titanium dioxide / sodium titanate / carbon composite material, conductive carbon black, and polyvinylidene fluoride was adjusted from 7:2:1 to 8.5:1:0.5, the battery retained 77.1% of its specific capacity after 1000 cycles.

[0079] As can be seen, the electrochemical performance of the composite material obtained in Example 2 is lower than that in Example 1, and the overall battery performance is reduced. The structural characteristics of the composite material determine that the carrier transport efficiency is lower than that in Example 1. At the same time, the reduction in the proportion of conductive agent leads to a decrease in electron collection efficiency, ultimately resulting in the electrochemical performance of the battery electrode material being lower than that in Example 1.

[0080] Example 3

[0081] The preparation of a titanium dioxide / sodium titanate / carbon composite material includes the following steps:

[0082] Step S1: Prepare an aqueous solution of graphene oxide with a concentration of 2 mg / mL and a concentration of 9 mol / L. -1 Sodium hydroxide solution;

[0083] Step S2: Take 40 mL of sodium hydroxide solution and add tetrabutyl titanate to make the volume concentration of tetrabutyl titanate 0.05 g / mL. -1 A hydrothermal reaction was carried out at a temperature of 200℃ for 24 hours.

[0084] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with water by deionization centrifugation (parameters 10000 r / min, 10 min). Then, it was vacuum dried at 60 °C for 12 h to obtain the sodium titanate precursor.

[0085] Step S3: Take 40 mL of deionized water and add tetrabutyl titanate to make the tetrabutyl titanate concentration 0.05 g / mL. -1 A hydrothermal reaction was carried out at a temperature of 200℃ for 24 hours.

[0086] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with deionized water by centrifugation (7000 r / min, 10 min). Then, it was vacuum dried at 60 °C for 12 h to obtain the titanium dioxide precursor.

[0087] Step S4: Add sodium titanate precursor and titanium dioxide precursor to the graphene oxide aqueous solution, and adjust the mass concentration of both sodium titanate precursor and titanium dioxide precursor to 1 mg / mL. -1 The suspension was stirred thoroughly for 24 hours, then centrifuged (6000 r / min, 5 min), and then vacuum dried at 60℃ for 12 hours.

[0088] Step S5: Place the material in a tube furnace and perform heat treatment under inert gas (argon or nitrogen) conditions at a temperature of 700℃ for 3 hours. This yields the titanium dioxide / sodium titanate / carbon composite material.

[0089] Electrode preparation / battery assembly: The obtained titanium dioxide / sodium titanate / carbon composite material, conductive carbon black, and polyvinylidene fluoride (mass ratio 8:1:1) were mixed uniformly in N-methylpyrrolidone and stirred for 0.5 h. The resulting uniform electrode slurry was coated onto copper foil, achieving a loading of 3.5 mg / cm³. 2 In a vacuum drying oven, at 90℃ for 18 hours, the electrode sheets were punched into circular electrode sheets with a diameter of 12mm. In a glove box, they were combined with sodium metal to form a two-electrode system. The battery assembly model was CR2025 button cell, and the voltage test range was 0.01-3V.

[0090] like Figure 9 As shown, the dispersion of titanium dioxide / sodium titanate was not as good as in Examples 1 and 2, and it was not uniformly dispersed on the graphene surface. This is related to insufficient metal ion dosage and short reaction time. At a current density of 0.05 Ag... -1At that time, the reversible capacity was 465.3 mAh g. -1 After 1000 cycles, the capacity retention rate was 52.4%.

[0091] The microstructure and distribution of titanium dioxide / sodium titanate / carbon, the main active materials in the electrode material, directly affect the overall performance of the electrode material. Because the process parameters are lower than in Example 1, its electrochemical performance is relatively lower. Due to the smaller amount of titanium dioxide / sodium titanate formed, the graphene content in the composite material is relatively high, and adjusting the electrode formulation ratio cannot compensate for the reduction in active sites, resulting in a lower specific capacity than in Example 1.

[0092] Comparative Example 1

[0093] The preparation of a titanium dioxide / sodium titanate / carbon composite material includes the following steps:

[0094] Step S1: Prepare an aqueous solution of graphene oxide with a concentration of 8 mg / mL and a concentration of 14 mol / L. -1 Sodium hydroxide solution;

[0095] Step S2: Take 70 mL of sodium hydroxide solution and add tetrabutyl titanate to make the volume concentration of tetrabutyl titanate 0.3 g / mL. -1 A hydrothermal reaction was carried out at a temperature of 200℃ for 24 hours.

[0096] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with water by deionization centrifugation (parameters 10000 r / min, 10 min). Then, it was vacuum dried at 60 °C for 12 h to obtain the sodium titanate precursor.

[0097] Step S3: Take 70 mL of deionized water and add tetrabutyl titanate to make the tetrabutyl titanate concentration 0.4 g / mL. -1 A hydrothermal reaction was carried out at a temperature of 200℃ for 24 hours.

[0098] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with deionized water by centrifugation (parameters 10000 r / min, 10 min). Then, it was vacuum dried at 60 °C for 12 h to obtain the titanium dioxide precursor.

[0099] Step S4: Add the sodium titanate precursor and the titanium dioxide precursor to the graphene oxide aqueous solution, and adjust the mass concentration of both the sodium titanate precursor and the titanium dioxide precursor to 6 mg / mL. -1 Stir thoroughly for 36 hours, then centrifuge (10000 r / min, 10 min), and vacuum dry at 60℃ for 12 hours.

[0100] Step S5: Place the material in a tube furnace and perform heat treatment under inert gas (argon or nitrogen) conditions at a temperature of 900℃ for 3.5 hours. This yields the titanium dioxide / sodium titanate / carbon composite material.

[0101] Electrode preparation / battery assembly: The obtained titanium dioxide / sodium titanate / carbon composite material, conductive carbon black, and polyvinylidene fluoride (mass ratio 7:2:1) were mixed uniformly in N-methylpyrrolidone and stirred for 0.5 h. The slurry was then coated onto copper foil with a loading of approximately 2.5 mg / cm³. 2 Vacuum drying at 60℃ for 12 hours, followed by punching into circular electrode sheets with a diameter of 12mm. These electrodes are then combined with sodium metal in a glove box to form a two-electrode system. The battery assembly model is CR2025 button cell, with a voltage test range of 0.01-3V.

[0102] like Figure 10 As shown, the titanium dioxide / sodium titanate / carbon exhibits severe agglomeration, preventing the acquisition of nanoscale composite materials with excellent structures. Due to the unsatisfactory structure of titanium dioxide / sodium titanate / carbon, its intrinsic electrochemical performance is not fully realized, with a specific capacity of only 386.9 mAh g⁻¹. -1 (0.05Ag -1 ).

[0103] Comparative Example 2

[0104] The preparation of a titanium dioxide / sodium titanate / carbon composite material includes the following steps:

[0105] Step S1: Prepare an aqueous solution of graphene oxide with a concentration of 1.5 mg / mL and a concentration of 7 mol / L. -1 Sodium hydroxide solution;

[0106] Step S2: Take 70 mL of sodium hydroxide solution and add tetrabutyl titanate to make the volume concentration of tetrabutyl titanate 0.05 g / mL. -1 A hydrothermal reaction was carried out at a temperature of 150℃ for 16 hours.

[0107] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with water by deionization centrifugation (parameters 6000 r / min, 5 min). Then, it was vacuum dried at 60 °C for 12 h to obtain the sodium titanate precursor.

[0108] Step S3: Take 70 mL of deionized water and add tetrabutyl titanate to make the tetrabutyl titanate concentration 0.05 g / mL. -1 A hydrothermal reaction was carried out at a temperature of 160℃ for 16 hours.

[0109] After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with deionized water by centrifugation (6000 r / min, 5 min). Then, it was vacuum dried at 60 °C for 12 h to obtain the titanium dioxide precursor.

[0110] Step S4: Add sodium titanate precursor and titanium dioxide precursor to the graphene oxide aqueous solution, and adjust the mass concentration of both sodium titanate precursor and titanium dioxide precursor to 1 mg / mL. -1 Stir thoroughly for 12 hours, then centrifuge (6000 r / min, 5 min), and vacuum dry at 60℃ for 12 hours.

[0111] Step S5: Place the material in a tube furnace and perform heat treatment under inert gas (argon or nitrogen) conditions at a temperature of 600℃ for 0.5 hours. This yields the titanium dioxide / sodium titanate / carbon composite material.

[0112] Electrode fabrication / battery assembly:

[0113] Titanium dioxide / sodium titanate / carbon composite material, conductive carbon black or carbon nanotubes, and polyvinylidene fluoride were mixed in N-methylpyrrolidone at a mass ratio of 8.5:1:0.5 and stirred for 0.1 h until homogeneous. The resulting uniform electrode paste was then coated onto copper foil with a loading of 2 mg / cm³. 2 If the loading is too low, the cycle stability will be insufficient and it will have no production reference value. If it is too high, the active material near the current collector will not be able to fully exert its electrochemical activity. Therefore, the loading should be appropriate. After coating, place it in a vacuum drying oven and dry it at 60°C for 12 hours. Then, cut it into circular electrode sheets with a diameter of 12 mm (as the negative electrode) or the corresponding electrode sheet size for card batteries. Finally, in a glove box, combine it with sodium foil to form a two-electrode system battery assembly for CR2025 coin cells or corresponding card batteries.

[0114] like Figure 11 As shown, due to changes in the preparation process of the titanium dioxide / sodium titanate / carbon composite material, the electrochemical performance of the composite material, which is the main electrode active material, is reduced due to insufficient metal ion source and insufficient processing time and temperature, resulting in a lower specific capacity of the battery.

[0115] Based on the test data from Examples 1-3 and Comparative Examples 1-2, the following summary and analysis are presented:

[0116] Structural factors are considered: the morphology and structure of the titanium dioxide / sodium titanate / carbon composite material directly affect its electrochemical applications. Comparative examples and comparative cases reveal that to ensure the synergistic and efficient interaction of titanium dioxide / sodium titanate and graphene, and to achieve a relatively uniform composite structure, the amount of metal ions used must be neither too much nor too little, and the amount of tetrabutyl titanate used must be appropriate for optimal results.

[0117] Cost considerations: The amount of raw materials used affects the difficulty of process implementation and the possibility of large-scale production. Therefore, the amounts of titanate and graphene used should be kept within limits, the temperature and time of the hydrothermal reaction should be sufficient to ensure the structure of the composite material, and the temperature and time of the annealing treatment should be sufficient to ensure the dispersion and electrochemical performance of titanium dioxide / sodium titanate.

[0118] Process considerations: The process settings directly determine the feasibility of large-scale material application; therefore, process simplification and small-scale production are crucial. Recommended process parameters are as follows: graphene oxide aqueous solution concentration 2-5 mg / mL, carbonization temperature 600-900℃, treatment time 1-3 h, and tetrabutyl titanate volume concentration 0.05-0.22 g / mL. -1 The hydrothermal reaction temperature is 160-200℃, and the hydrothermal time is 16-24h.

[0119] Therefore, the present invention, by employing the preparation and application of the aforementioned titanium dioxide / sodium titanate / carbon composite material, can solve the problem of insufficient chemical kinetic properties in existing titanium-based sodium-ion battery anode materials.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a titanium dioxide / sodium titanate / carbon composite material, characterized in that, Includes the following steps: Step S1: Prepare an aqueous solution of graphene oxide and a sodium hydroxide solution; Step S2: Take 40-70 mL of sodium hydroxide solution and add tetrabutyl titanate to make the volume concentration of tetrabutyl titanate 0.05-0.22 g / mL. -1 A hydrothermal reaction occurs; The hydrothermal reaction temperature is 160-200℃, and the hydrothermal time is 16-24h; After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with deionized centrifuged water. Then, it was vacuum dried at 60°C for 12 hours to obtain the sodium titanate precursor. Step S3: Take 40-70 mL of deionized water and add tetrabutyl titanate to make the tetrabutyl titanate concentration 0.05-0.22 g / mL. -1 A hydrothermal reaction occurs; The hydrothermal reaction temperature is 160-200℃, and the hydrothermal time is 16-24h; After the hydrothermal reaction was completed, the mixture was cooled to room temperature and washed three times with deionized water by centrifugation. Then, it was vacuum dried at 60°C for 12 hours to obtain the titanium dioxide precursor. Step S4: Add sodium titanate precursor and titanium dioxide precursor to the graphene oxide aqueous solution, and adjust the mass concentration of both sodium titanate precursor and titanium dioxide precursor to 1-4 mg / mL. -1 The suspension was stirred thoroughly for 12-24 hours, then centrifuged and vacuum dried at 60°C for 12 hours. Step S5: Place it in a tube furnace and heat treat it under inert gas conditions to obtain titanium dioxide / sodium titanate / carbon composite material. The heat treatment temperature is 600-900℃, and the heat treatment time is 1-3h.

2. The method for preparing a titanium dioxide / sodium titanate / carbon composite material according to claim 1, characterized in that: In step S1, the concentration of the graphene oxide aqueous solution is 2-5 mg / mL, and the concentration of the sodium hydroxide solution is 9-12 mol / L. -1 .

3. The method for preparing a titanium dioxide / sodium titanate / carbon composite material according to claim 1, characterized in that: In step S2, the centrifugation speed is 6000-10000 r / min, and the centrifugation time is 5-10 min; In step S3, the centrifugation speed is 6000-10000 r / min, and the centrifugation time is 5-10 min; In step S4, the centrifugation speed is 6000-10000 r / min, and the centrifugation time is 5-10 min.

4. The method for preparing a titanium dioxide / sodium titanate / carbon composite material according to claim 1, characterized in that: In step S5, the inert gases include argon and nitrogen.

5. The application of the titanium dioxide / sodium titanate / carbon composite material prepared by the method of any one of claims 1-4 in sodium-ion batteries.

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