Titanium dioxide / three-dimensional carbon composite material as well as preparation method and sodium storage application thereof

Abstract

The invention discloses a titanium dioxide / three-dimensional carbon composite material and a preparation method and sodium storage application thereof, and belongs to the technical field of electrode materials. The method comprises the following steps: preparing a graphene oxide aqueous solution and a water / ethanol mixed solution; the preparation method comprises the following steps: adding tetrabutyl titanate into a water / ethanol mixed solution, stirring, hydrolyzing, carrying out hydrothermal reaction and heat preservation, cooling, and carrying out centrifugal cleaning and vacuum drying to obtain a titanium dioxide precursor; placing the precursor in a graphene oxide aqueous solution to prepare a suspension, dipping melamine foam, and freeze-drying; finally, carbonizing in a tubular furnace under a nitrogen atmosphere, preserving heat, soaking and cleaning with deionized water, and drying in vacuum to obtain a target product. Parameters such as solution concentration, reaction temperature, reaction time, rate and the like are limited in each step, the preparation of the composite material is realized, the prepared composite material is used for preparing the sodium-ion battery, the problem of insufficient chemical kinetic characteristics of a titanium-oxygen-based sodium-ion battery negative electrode material is solved, and the service life of the sodium-ion battery is prolonged. And the rate capability and the cycle performance of the electrode plate (battery) are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and in particular to a titanium dioxide / three-dimensional carbon composite material, a preparation method thereof, and sodium storage applications. Background Art

[0002] Titanium dioxide (TiO2) has become a research hotspot in electrochemistry due to its inherent transition metal properties and environmentally friendly advantages. Compared with traditional sulfides and oxides, TiO2 exhibits superior electrochemical stability and environmental friendliness, thus offering promising prospects for energy storage applications. However, its inherent low electrical conductivity leads to limited electrochemical performance, low specific capacity, poor rate capability, and rapid capacity decay after cycling. Current strategies to address these issues primarily include structural design, carbon modification, and heterostructure construction. For example, Guo et al. constructed MoSe2 nanosheets on the surface of TiO2 hollow nanospheres and further doped them, utilizing a hierarchical structure to overcome the shortcomings of MoSe2's high surface energy and weak interlayer van der Waals forces. Through morphological design, they improved the electronic structure of TiO2-based battery anodes, thereby enhancing the battery's cycle life and rate performance. However, titanium-based sodium-ion battery anode materials still commonly suffer from insufficient chemical kinetics. Summary of the Invention

[0003] The purpose of the present invention is to provide a titanium dioxide / three-dimensional carbon composite material and its preparation method and sodium storage application, so as to solve the problem of insufficient chemical kinetic properties of the existing titanyl sodium ion battery negative electrode material mentioned in the background art.

[0004] To achieve the above object, the present invention provides a method for preparing a titanium dioxide / three-dimensional carbon composite material, which specifically comprises the following steps:

[0005] Step 1, preparing a graphene oxide aqueous solution and a water / ethanol mixed solution;

[0006] Step 2: adding tetrabutyl titanate to a water / ethanol mixed solution, stirring and hydrolyzing, and then transferring the mixture to a reactor for hydrothermal reaction and then keeping the mixture warm;

[0007] Step 3: Cool to room temperature, then centrifuge and wash with deionized water, and vacuum dry to obtain a titanium dioxide precursor;

[0008] Step 4: placing a titanium dioxide precursor in a graphene oxide aqueous solution to prepare a suspension, impregnating the suspension with melamine foam, and freezing and then drying the suspension;

[0009] Step 5: Transfer to a tube furnace, carbonize under a nitrogen atmosphere and keep warm, soak and clean with deionized water and then vacuum dry to obtain the target product, titanium dioxide / three-dimensional carbon composite material.

[0010] Preferably, in step 1, the concentration of the graphene oxide aqueous solution is 2.0-5.0 mg / mL; and in the water / ethanol mixed solution, the volume ratio of water to ethanol is 1:2-2:1.

[0011] Preferably, in step 2, the concentration of tetrabutyl titanate after hydrolysis is 0.05-0.22 g / mL.

[0012] Preferably, in step 2, the stirring hydrolysis time is 12-24 hours, the temperature of the hydrothermal reaction is 160-200° C., and the insulation time is 16-24 hours.

[0013] Preferably, in step 3, the centrifugal speed is 6000-10000 r / min, and the centrifugal time is 5-10 min; the vacuum drying temperature is 60° C., and the vacuum drying time is 12 h.

[0014] Preferably, in step 4, the mass concentration of the suspension is 1-3 mg / mL.

[0015] Preferably, in step 4, the freezing time is 8-12 hours and the drying time is 8-12 hours.

[0016] Preferably, in step five, the temperature is raised to 600-900°C at a heating rate of 2-5°C for carbonization, and the holding time is 1.5-3h; the soaking time is 12-24h, and the water is changed 3-5 times; the vacuum drying temperature is 60°C, and the vacuum drying time is 12-24h.

[0017] The present invention also provides a titanium dioxide / three-dimensional carbon composite material prepared by the above preparation method.

[0018] The present invention also provides application of the titanium dioxide / three-dimensional carbon composite material in sodium ion batteries.

[0019] Therefore, the titanium dioxide / three-dimensional carbon composite material provided by the present invention, its preparation method, and sodium storage application have the following beneficial effects:

[0020] 1. The titanium-based composite material disclosed in the present invention has a high sodium storage capacity.

[0021] The present invention introduces three-dimensional composite carbon into the composite material, which is beneficial to improving the dispersion of titanium dioxide and increasing the specific surface area of ​​the composite material (such as Figure 1 As shown), it provides sufficient active sites for the sodium ion deintercalation process of the titanium-based composite material, thereby improving the sodium storage capacity of the composite material. The battery prepared by using the composite material (electrode) disclosed in the present invention has a current density of 0.05A·g -1 The reversible capacity can reach 213 mAh g -1 .

[0022] 2. The composite material disclosed in the present invention can alleviate the volume strain of titanium dioxide during the electrochemical process.

[0023] The introduction of three-dimensional carbon skeleton and two-dimensional graphene can provide abundant electron transport channels and have a positive effect on the distribution of titanium dioxide. The unique spatial structure of composite carbon provides abundant active sites and a stable electrochemical structure basis for the insertion / extraction of sodium ions. At the same time, it can alleviate the volume strain of semiconductor material titanium dioxide during the charging and discharging process.

[0024] 3. The composite material disclosed in the present invention has good electrochemical structural stability, and the electrode sheet prepared has excellent cycle performance.

[0025] The intrinsic properties of electrode materials determine their electrochemical properties. Titanium dioxide / three-dimensional carbon composite materials combine the reaction kinetics advantages of titanium dioxide, three-dimensional carbon skeleton, and graphene. The introduction of carbon skeleton expands the microscopic spatial structure of the composite material, and the introduction of graphene increases the dispersion of titanium dioxide. The structural modification improves the carrier transport kinetics and enhances the structural stability of the electrochemical reaction of the composite material, resulting in a sodium ion battery with excellent cycle performance. When the current density is 1.0A·g -1 When the cycle is repeated for 1000 times, the reversible capacity retention rate reaches 86.8%.

[0026] 4. The composite material disclosed in the present invention has good reaction reversibility, and the electrode sheet (battery) prepared therefrom has excellent rate performance.

[0027] Compared with carbon dioxide, titanium dioxide / three-dimensional carbon can improve the sodium ion insertion and extraction kinetics of the material by regulating the electron ion transport channel and provide more abundant sodium ion reaction active centers, which accelerates the transport of carriers and improves the specific capacity of the composite electrode material. As can be seen from the rate curve, at 0.05, 0.1, 0.3, 0.5, 0.8, 1.0, 3.0, 5.0, 8.0, 10.0 A·g -1 At the current density of 1.5 GHz, the specific capacity of the titanium dioxide / three-dimensional carbon composite material is as high as 213, 201.7, 176.1, 159.7, 141.9, 137.8, 106.2, 89.9, 76.1, and 69.2 mAh·g -1 . And back to 0.1A·g -1 At a current density of 1.5 GHz, the capacity shows almost no attenuation, which once again demonstrates that the obtained carbon dioxide / three-dimensional carbon composite material has excellent electrochemical reaction reversibility.

[0028] 5. The preparation steps of the present invention are simple, the reaction conditions are mild, easy to control, and the raw materials used are low in cost, which is suitable for large-scale production.

[0029] The preparation process of titanium dioxide / three-dimensional carbon composite materials uses ordinary blast drying ovens and tubular furnaces, both of which are ordinary conventional low-risk material preparation equipment. There are no harsh conditions in the preparation process of the composite materials, which makes conventional large-scale production possible; the base material in the composite material is carbon material, and the active material is carbon dioxide, which provides guarantees for the low cost and environmental friendliness of the composite material. Titanium metal is a conventional non-strategic resource metal and is non-toxic, which also creates favorable conditions for the large-scale production and utilization of the composite material.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a SEM morphology of the titanium dioxide precursor prepared in Example 1 of the present invention;

[0032] Figure 2 This is an SEM morphology image of the titanium dioxide / three-dimensional carbon composite material prepared in Example 1 of the present invention;

[0033] Figure 3 XRD patterns of titanium dioxide and titanium dioxide / three-dimensional carbon composite materials prepared in Example 1 of the present invention;

[0034] Figure 4 Thermogravimetric curves of titanium dioxide and titanium dioxide / three-dimensional carbon composite materials prepared in Example 1 of the present invention;

[0035] Figure 5 Isothermal nitrogen adsorption-desorption curves of titanium dioxide and titanium dioxide / three-dimensional carbon composite materials prepared in Example 1 of the present invention;

[0036] Figure 6 The pore size distribution curves of titanium dioxide and titanium dioxide / three-dimensional carbon composite materials prepared in Example 1 of the present invention are shown;

[0037] Figure 7 The sodium ion battery prepared in Example 1 of the present invention has a current density of 0.05A·g -1 Constant current charge and discharge curve when

[0038] Figure 8 This is a comparison chart of the rate performance of sodium ion batteries made from titanium dioxide and titanium dioxide / three-dimensional carbon composite materials prepared in Example 1 of the present invention;

[0039] Figure 9 The sodium ion battery prepared in Example 1 of the present invention has a current density of 1.0 A·g -1 The cycle performance curve diagram below;

[0040] Figure 10This is a SEM morphology image of the titanium dioxide / three-dimensional carbon composite material prepared in Example 2 of the present invention;

[0041] Figure 11 This is a SEM morphology image of the titanium dioxide / three-dimensional carbon composite material prepared in Example 3 of the present invention;

[0042] Figure 12 This is a SEM morphology image of the titanium dioxide / three-dimensional carbon composite material prepared in Comparative Example 1 of the present invention;

[0043] Figure 13 This is a SEM morphology image of the titanium dioxide / three-dimensional carbon composite material prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0044] The present invention provides a method for preparing a titanium dioxide / three-dimensional carbon composite material, which specifically comprises the following steps:

[0045] Step 1: prepare a graphene oxide aqueous solution and a water / ethanol mixed solution.

[0046] Among them, the concentration of the graphene oxide aqueous solution is 2.0-5.0 mg / mL. Too low a concentration will lead to insufficient alleviation of titanium dioxide agglomeration, and too high a concentration will lead to excessively high carbon content, reducing the electrochemical properties of the composite material; the volume ratio of water to ethanol is 1:2-2:1.

[0047] Step 2: Add tetrabutyl titanate to a water / ethanol mixed solution, stir and hydrolyze for 12-24 hours, then transfer to a reactor for hydrothermal reaction at 160-200° C. and keep warm for 16-24 hours.

[0048] The concentration of tetrabutyl titanate is 0.05-0.22 g / mL, preferably 0.05, 0.10, 0.15, 0.18, or 0.22 mg / mL. Too low a concentration of tetrabutyl titanate will result in insufficient titanium dioxide production, while too high a concentration will cause agglomeration during the hydrolysis process, reducing the utilization rate of the titanium dioxide's surface active sites.

[0049] Step 3: Cool to room temperature, then wash three times with deionized water by centrifugation (centrifugal speed is 6000-10000 r / min, centrifugation is 5-10 min), and dry at 60° C. under vacuum conditions for 12 h to obtain a titanium dioxide precursor.

[0050] Step 4: Place the titanium dioxide precursor in a graphene oxide aqueous solution to prepare a suspension, fully impregnate the melamine foam, freeze for 8-12 hours, and then dry for 8-12 hours.

[0051] Among them, the mass concentration of the graphene suspension of the titanium dioxide precursor is 1-3 mg / mL. If the concentration is too low, the dispersion of the titanium dioxide precursor will be insufficient, and if the concentration is too high, the utilization rate of the graphene will be insufficient.

[0052] Step 5: Transfer to a tubular furnace, heat to 600-900°C at a heating rate of 2-5°C under a nitrogen atmosphere for carbonization, keep warm for 1.5-3 hours, soak and wash with deionized water for 12-24 hours, change the water 3-5 times, and finally dry at 60°C under vacuum conditions for 12-24 hours to obtain the target product, titanium dioxide / three-dimensional carbon composite material.

[0053] Among them, if the carbonization heating rate is too low, it will lead to increased energy consumption and cost. If the rate is too high, the melamine will shrink too quickly and the resulting carbon skeleton will have insufficient microscopic pores, which will ultimately make the electrochemical activity of the composite material low.

[0054] The present invention also provides a titanium dioxide / three-dimensional carbon composite material prepared by the above preparation method, which has the following characteristics:

[0055] 1) Size Characteristics: Titanium dioxide / 3D carbon composites are micro-nano composites. The carbon fibers derived from melamine carbonization are micron-sized, while titanium dioxide and graphene are nanoscale materials. Micron-sized materials can enhance the rate capability of electrode materials, while nanomaterials can ensure the electrochemical activity of electrode materials, thereby improving the electrochemical reaction kinetics. To fully utilize the electrochemical activity of titanium dioxide, the carbonaceous substrate content is preferably controlled below 20%.

[0056] 2)Structure and performance characteristics:

[0057] Titanium is a transition metal element with empty orbitals in the outermost layer of its electronic structure. Therefore, titanium dioxide is a semiconductor material. This results in the problem that its electrochemical properties cannot be fully utilized during the electrochemical reaction process due to its low electronic conductivity and large volume strain. The energy storage mechanism of carbonaceous base materials is mainly the adsorption / desorption of alkali metal ions, so its electrochemical properties are relatively stable. After the two constituent unit materials are combined, the synergistic effect makes the composite material have both high specific capacity and excellent cycle stability.

[0058] 3) Process characteristics: The composite material is obtained by combining hydrothermal method and carbonization heat treatment. The method is traditional, the process is simple and easy to implement.

[0059] 4) Cost characteristics: The main component of titanium dioxide / three-dimensional carbon composite materials is titanium dioxide. Titanium is a conventional transition metal with high abundance in the earth's crust and is non-toxic and harmless. Therefore, developing related technologies for its composite materials has advantages in improving the electrochemical properties of its composite materials and promoting the environmentally friendly development of energy storage materials.

[0060] The present invention also discloses an electrode sheet and a sodium ion battery. The electrode sheet is made of the titanium dioxide / three-dimensional carbon composite material, and the sodium ion battery contains the electrode sheet.

[0061] Specifically, the preparation method of the electrode sheet and the sodium ion battery is as follows:

[0062] Mix titanium dioxide / three-dimensional carbon composite material, conductive carbon black or carbon nanotubes and polyvinylidene fluoride in N-methylpyrrolidone at a mass ratio of 7.5-8.5:2-1:0.5, stir for 0.2-1h, and stir until uniform; coat the obtained uniform electrode slurry on copper foil with a loading of 5-12 mg / cm 2 If the loading is too low, it will have no production reference value, while if it is too high, the material near the current collector will not be able to fully exert its performance. Therefore, the loading should be within an appropriate range. After coating, place it in a vacuum drying oven and dry it at 60-120℃ for 12-48 hours. Punch it into a circular electrode sheet with a diameter of 12mm (as the negative electrode) or the corresponding electrode sheet size for a card battery. Finally, in a glove box, combine it with sodium foil to form a two-electrode system battery assembly model CR2025 button cell or the corresponding card battery.

[0063] The technical solution of the present invention is further described below by means of the accompanying drawings and examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Any other changes, modifications, substitutions, combinations, and simplifications made without violating the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the protection scope of the present invention. In addition, it should be understood that after reading the contents of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application and belong to the scope of protection of the present invention.

[0064] References to "embodiments" herein mean that the specific features, structures, or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the word "embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or relevance to other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the various technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution.

[0065] Unless otherwise defined, the technical terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms herein is only for describing specific embodiments and is not intended to limit this application.

[0066] Unless otherwise specified in the present invention, the reagents, instruments, equipment and performance testing methods used are those commonly used by those skilled in the art.

[0067] Example 1

[0068] This embodiment provides a method for preparing a titanium dioxide / three-dimensional carbon composite material, which specifically includes the following steps:

[0069] Step 1: First, prepare a 3 mg / mL graphene oxide aqueous solution and 60 mL of a water / ethanol mixed solution (volume ratio 1:1).

[0070] Step 2: Take 4.0 mL of tetrabutyl titanate and add it to the water / ethanol mixed solution, stir it thoroughly for 24 hours, transfer it to a reactor, and keep it at 180°C for 18 hours.

[0071] Step 3: Cool to room temperature, wash three times with deionized water by centrifugation (8000 r / min, 8 min), and then dry under vacuum at 60° C. for 12 h to obtain a titanium dioxide precursor.

[0072] Step 4: Place the titanium dioxide precursor in a graphene oxide aqueous solution to prepare a graphene oxide aqueous solution of the precursor, adjust the mass concentration to 2 mg / mL, and then immerse an appropriate volume of melamine foam. After sufficient immersion, freeze for 12 hours and then dry for 12 hours.

[0073] Step 5: Transfer to a tubular furnace and carbonize under an argon atmosphere at a heating rate of 4°C / min, 800°C, keep warm for 2 hours, soak and clean with 1000mL deionized water for 24 hours, change the water 3 times, 60°C, and vacuum dry for 24 hours to obtain a titanium dioxide / three-dimensional carbon composite material.

[0074] Electrode preparation / battery assembly: The final target product, copper zinc selenide / three-dimensional carbon composite material, conductive carbon black, and polyvinylidene fluoride were mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 and stirred for 0.5 hours. The resulting uniform electrode slurry was coated on copper foil with a loading of 8 mg / cm 2 After preparation, it was dried in a vacuum drying oven at 60°C for 12 hours, punched into circular electrode sheets with a diameter of 12 mm, and matched with metallic sodium in a glove box to form a two-electrode battery system, model CR2025, with a voltage test range of 0.01-3V.

[0075] Figure 1 This is an SEM morphology image of the titanium dioxide precursor in this example (the titanium dioxide preparation process is: no carbonaceous material is involved in the whole process, and other parameters and operations are the same as Example 1). It can be seen from the figure that the titanium dioxide is a nanorod with a cross-sectional diameter of about 50 nm.

[0076] Figure 2 This is a SEM morphology image of the titanium dioxide / three-dimensional carbon composite material in this embodiment. It can be seen from the image that titanium dioxide is relatively evenly dispersed on the surface of the gap between the graphene / three-dimensional carbon skeleton.

[0077] Figure 3 : is the XRD spectrum of titanium dioxide and titanium dioxide / three-dimensional carbon composite material in this embodiment. It can be seen from the figure that the titanium dioxide / three-dimensional carbon composite material was successfully synthesized.

[0078] Figure 4 3 is the thermogravimetric curve of the titanium dioxide / three-dimensional carbon composite material and titanium dioxide in this embodiment. It can be seen from the figure that the mass content of carbon in the composite material is about 8.84%.

[0079] Figure 5 The isothermal nitrogen adsorption-desorption curves and pore size distribution curves of titanium dioxide and titanium dioxide / three-dimensional carbon composite materials in this embodiment are shown in FIG. Figure 6 ), it can be seen from the figure that titanium dioxide and titanium dioxide / three-dimensional carbon composite materials are mainly mesoporous materials, with specific surface areas of 134.54m 2 g -1 , 184.75m 2 g -1 .

[0080] Figure 7 The sodium ion battery in this embodiment has a current density of 0.05A·g -1 The constant current charge and discharge curves at the time of the cycle show that after the fourth cycle, the curves overlap. This is because the SEI film is formed and tends to be stable, and the charge and discharge platform of the material is about 0.55V.

[0081] Figure 8 The rate performance diagram of the battery in this embodiment shows that the current density is 0.05, 0.1, 0.3, 0.5, 0.8, 1.0, 3.0, 5.0, 8.0, 10.0 A·g -1 The reversible capacities of titanium dioxide and titanium dioxide / three-dimensional carbon composites can reach 194.1, 180.9, 153.3, 137.3, 123.9, 118.3, 93.5, 81.5, 75.3, 69.2, and 213, 201.7, 176.1, 159.7, 141.9, 137.8, 106.2, 89.9, 76.1, 69.2 mAh·g, respectively. -1 .

[0082] Figure 9 In this embodiment, the battery is at a current density of 1.0 A·g -1The cycle life under the condition of 1000 cycles is shown in Figure 2. The capacity retention rate reaches 86.8% after 1000 cycles. It can be seen that the prepared electrode material / battery exhibits good cycle stability.

[0083] Example 2

[0084] This embodiment provides a method for preparing a titanium dioxide / three-dimensional carbon composite material, which specifically includes the following steps:

[0085] Step 1: First, prepare a graphene oxide aqueous solution with a concentration of 4.5 mg / mL and prepare 60 mL of a water / ethanol mixed solution (volume ratio 1:2).

[0086] Step 2: Take 5.0 mL of tetrabutyl titanate and add it to the water / ethanol mixed solution, stir it thoroughly for 24 hours, transfer it to a reactor, and keep it at 200°C for 18 hours.

[0087] Step 3: Cool to room temperature, wash three times with deionized water by centrifugation (8000 r / min, 8 min), and then dry under vacuum at 60° C. for 12 h to obtain a titanium dioxide precursor.

[0088] Step 4: Place the titanium dioxide precursor in a graphene oxide aqueous solution to prepare a graphene oxide aqueous solution of the precursor, adjust the mass concentration to 3 mg / mL, and then immerse an appropriate volume of melamine foam. After sufficient immersion, freeze for 12 hours and then dry for 12 hours.

[0089] Step 5: Transfer to a tubular furnace and carbonize under an argon atmosphere at a heating rate of 4°C / min, 900°C, keep warm for 2 hours, soak and clean with 1000mL deionized water for 24 hours, change the water 3 times, 60°C, and vacuum dry for 24 hours to obtain a titanium dioxide / three-dimensional carbon composite material.

[0090] Electrode preparation / battery assembly: The final target product, titanium dioxide / three-dimensional carbon composite material, conductive carbon black, and polyvinylidene fluoride were mixed in N-methylpyrrolidone at a mass ratio of 7.5:2:0.5 and stirred for 0.5 hours. The resulting uniform electrode slurry was coated on copper foil with a loading of 6 mg / cm 2 After preparation, it was dried in a vacuum drying oven at 60°C for 12 hours, punched into circular electrode sheets with a diameter of 12 mm, and matched with metallic sodium in a glove box to form a two-electrode battery system, model CR2025, with a voltage test range of 0.01-3V.

[0091] Figure 10This is a SEM image of the titanium dioxide / three-dimensional carbon composite material from this example. The image shows that the dispersed titanium dioxide has a higher density than that in Example 1, which is related to the temperature and duration of the hydrothermal reaction. When the mass ratio of the titanium dioxide / three-dimensional carbon composite, conductive carbon black, and polyvinylidene fluoride was adjusted from 8:1:1 to 7.5:2:0.5, the battery maintained a specific capacity of 697% after 1000 cycles.

[0092] The electrochemical performance of the composite material obtained in this example was lower than that of Example 1, resulting in a decrease in the overall performance of the sodium-ion battery. The composite material's microstructure determined that its carrier transport dynamics were inferior to those of Example 1. Furthermore, the adjustment in the conductive agent ratio altered the electron collection efficiency, ultimately leading to changes in the battery's cycling performance.

[0093] Example 3

[0094] This embodiment provides a method for preparing a titanium dioxide / three-dimensional carbon composite material, which specifically includes the following steps:

[0095] Step 1: First, prepare a graphene oxide aqueous solution with a concentration of 2.0 mg / mL and prepare 60 mL of a water / ethanol mixed solution (volume ratio 2:1).

[0096] Step 2: Take 3.0 mL of tetrabutyl titanate and add it to the water / ethanol mixed solution, stir it thoroughly for 24 hours, transfer it to a reactor, and keep it at 180°C for 16 hours.

[0097] Step 3: Cool to room temperature, wash three times with deionized water by centrifugation (9000 r / min, 8 min), and then dry under vacuum at 60° C. for 12 h to obtain a titanium dioxide precursor.

[0098] Step 4: Place the titanium dioxide precursor in a graphene oxide aqueous solution to prepare a graphene oxide aqueous solution of the precursor, adjust the mass concentration to 1 mg / mL, and then immerse an appropriate volume of melamine foam. After sufficient immersion, freeze for 12 hours and then dry for 12 hours.

[0099] Step 5: Transfer to a tubular furnace and carbonize under an argon atmosphere at a heating rate of 3°C / min, 800°C, keep warm for 1.5 hours, soak and clean with 1000mL deionized water for 24 hours, change water 3 times, 60°C, and vacuum dry for 15 hours to obtain a titanium dioxide / three-dimensional carbon composite material.

[0100] Electrode preparation / battery assembly: The final target product, titanium dioxide / three-dimensional carbon composite material, conductive carbon black, and polyvinylidene fluoride (mass ratio 7:2:1) were mixed in N-methylpyrrolidone and stirred for 1 hour. The resulting uniform electrode slurry was coated on copper foil with a loading of 10 mg / cm 2, in a vacuum drying oven, at 120℃, keep warm for 6h, punch out circular electrode sheets with a diameter of 12mm, and form a two-electrode system with sodium metal in a glove box. The battery assembly model is CR2025 button battery, and the voltage test range is 0.01-3V.

[0101] Figure 11 The SEM morphology of the titanium dioxide / three-dimensional carbon composite material in this example shows that the dispersion of the three-dimensional titanium dioxide / carbon is not as good as that of Examples 1 and 2, and the dispersion within the three-dimensional carbon voids is poor. This is related to the insufficient amount of metal ions and the short reaction time. -1 The reversible capacity is 206.5 mAh g -1 , after 1000 cycles, the capacity retention rate is 62.5%.

[0102] The microstructure and distribution of titanium dioxide, the primary active material in the electrode, directly influence the electrochemical performance of the titanium-based composite electrode. Because the process parameters were lower than those in Example 1, the electrochemical performance was relatively low. Due to the insufficient active sites provided by titanium dioxide, the carbon content in the composite material was relatively high. Adjusting the electrode ingredient ratio was unable to compensate for the loss in electrochemical activity, resulting in performance lower than that in Example 1.

[0103] Comparative Example 1

[0104] This comparative example provides a method for preparing a titanium dioxide / three-dimensional carbon composite material, which specifically comprises the following steps:

[0105] Step 1: First, prepare a graphene oxide aqueous solution with a concentration of 6.5 mg / mL and prepare 60 mL of a water / ethanol mixed solution (volume ratio 4:1).

[0106] Step 2: Take 7.0 mL of tetrabutyl titanate and add it to the water / ethanol mixed solution, stir it thoroughly for 24 hours, transfer it to a reactor, and keep it at 180°C for 18 hours.

[0107] Step 3: Cool to room temperature, wash three times with deionized water by centrifugation (10000 r / min, 8 min), and then dry under vacuum at 60° C. for 12 h to obtain a titanium dioxide precursor.

[0108] Step 4: Place the titanium dioxide precursor in a graphene oxide aqueous solution to prepare a graphene oxide aqueous solution of the precursor, adjust the mass concentration to 4.5 mg / mL, and then immerse an appropriate volume of melamine foam. After sufficient immersion, freeze for 12 hours and then dry for 12 hours.

[0109] Step 5: Transfer to a tubular furnace and carbonize under an argon atmosphere at a heating rate of 5°C / min, 800°C, keep warm for 2 hours, soak and clean with 1000mL deionized water for 24 hours, change water 3 times, 60°C, and vacuum dry for 12 hours to obtain a titanium dioxide / three-dimensional carbon composite material.

[0110] Electrode preparation / battery assembly: The final target product, titanium dioxide / three-dimensional carbon composite material, conductive carbon black, and polyvinylidene fluoride (mass ratio 7.5:2:1) were mixed in N-methylpyrrolidone and stirred for 0.5 hours. The slurry was coated on copper foil with a loading of about 8 mg / cm 2 , vacuum drying, 60℃, 12h, punched into circular electrode sheets with a diameter of 12mm, and composed of a two-electrode system with sodium metal in a glove box. The battery assembly model is CR2025 button battery, and the voltage test range is 0.01-3V.

[0111] Figure 12 This is the SEM morphology of the titanium dioxide / three-dimensional carbon composite material in this comparative example. It can be seen that the titanium dioxide is agglomerated into blocks, and a nano-scale composite material with excellent structure cannot be obtained. Because the three-dimensional titanium dioxide / carbon structure is not ideal, its intrinsic electrochemical performance is not fully utilized, and its specific capacity is only 199.7 mAh·g -1 (0.05A·g -1 ).

[0112] Comparative Example 2

[0113] This comparative example provides a method for preparing a titanium dioxide / three-dimensional carbon composite material, which specifically comprises the following steps:

[0114] Step 1: First, prepare a graphene oxide aqueous solution with a concentration of 1.0 mg / mL and prepare 60 mL of a water / ethanol mixed solution (volume ratio 1:4).

[0115] Step 2: Take 2 mL of tetrabutyl titanate and add it to the water / ethanol mixed solution, stir it thoroughly for 24 hours, transfer it to a reactor, and keep it at 160°C for 18 hours.

[0116] Step 3: Cool to room temperature, wash three times with deionized water by centrifugation (10000 r / min, 8 min), and then dry under vacuum at 60° C. for 12 h to obtain a titanium dioxide precursor.

[0117] Step 4: Place the titanium dioxide precursor in a graphene oxide aqueous solution to prepare a graphene oxide aqueous solution of the precursor, adjust the mass concentration to 0.5 mg / mL, and then immerse an appropriate volume of melamine foam. After sufficient immersion, freeze for 12 hours and then dry for 12 hours.

[0118] Step 5: Transfer to a tubular furnace and carbonize under an argon atmosphere at a heating rate of 5°C / min, 800°C, keep warm for 1 hour, soak and clean with 1000mL deionized water for 24 hours, change water 3 times, 60°C, and vacuum dry for 12 hours to obtain a titanium dioxide / three-dimensional carbon composite material.

[0119] Electrode preparation / battery assembly: The final target product, titanium dioxide / three-dimensional carbon composite material, conductive carbon black, and polyvinylidene fluoride (mass ratio of 8:1:1) were mixed in N-methylpyrrolidone and stirred for 0.5 hours. The resulting slurry was coated on copper foil with a loading of approximately 1.5 mg / cm 2 The electrode was vacuum dried (60°C, 12h) and punched into circular electrode sheets with a diameter of 12mm. The two-electrode system battery was assembled with sodium foil in a glove box. The battery model was CR 2025 button cell. The voltage test range was 0.01-3V, and its specific capacity was only 196.9mA h·g -1 (0.05A·g -1 ).

[0120] Figure 13 This is the SEM morphology of the titanium dioxide / three-dimensional carbon composite material in this comparative example. Due to changes in the preparation process of the titanium dioxide / three-dimensional carbon composite material, three-dimensional titanium dioxide is used as the main electrode active material. Due to insufficient metal ion source and insufficient processing time and temperature, the electrochemical performance of the composite material is reduced, resulting in a low final specific capacity of the battery.

[0121] Based on the above examples and comparative example data, the summary and analysis are as follows:

[0122] Structural considerations: The morphology of the titanium dioxide / three-dimensional carbon composite directly impacts its electrochemical applications. Comparing the examples and comparative examples reveals that ensuring the synergistic efficiency of titanium dioxide and composite carbon, and a relatively uniform composite structure, requires a moderate amount of titanium ions, and optimal hydrolysis rates.

[0123] Cost considerations: The amount of raw materials used influences the difficulty of process implementation and the feasibility of large-scale production. Therefore, the amounts of titanate, graphene, and melamine used should be within a reasonable range. The hydrothermal reaction temperature and duration should be sufficient to achieve the composite material structure, and the heat treatment temperature and duration should be sufficient to ensure sufficient carbonization.

[0124] Process considerations: The process setup directly determines the material's scalable application potential, so process simplification and minimization are prerequisites. Therefore, the process parameters used are: graphene oxide aqueous solution concentration of 2-5 mg / mL, carbonization temperature of 600-900°C, tetrabutyl titanate concentration of 0.05-0.22 g / mL, hydrothermal reaction temperature of 160-200°C, hydrothermal time of 16-24 hours, and carbonization heat treatment time of 1-3 hours.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements 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 / three-dimensional carbon composite material, characterized in that: The specific steps include: Step 1, preparing a graphene oxide aqueous solution and a water / ethanol mixed solution; Step 2: adding tetrabutyl titanate to a water / ethanol mixed solution, stirring and hydrolyzing, and then transferring the mixture to a reactor for hydrothermal reaction and then keeping the mixture warm; Step 3: Cool to room temperature, then centrifuge and wash with deionized water, and vacuum dry to obtain a titanium dioxide precursor; Step 4: placing a titanium dioxide precursor in a graphene oxide aqueous solution to prepare a suspension, impregnating the suspension with melamine foam, and freezing and then drying the suspension; Step 5: Transfer to a tube furnace, carbonize under a nitrogen atmosphere and keep warm, soak and clean with deionized water and then vacuum dry to obtain the target product, titanium dioxide / three-dimensional carbon composite material.

2. The method for preparing a titanium dioxide / three-dimensional carbon composite material according to claim 1, wherein: In step 1, the concentration of the graphene oxide aqueous solution is 2.0-5.0 mg / mL; in the water / ethanol mixed solution, the volume ratio of water to ethanol is 1:2-2:

1.

3. The method for preparing a titanium dioxide / three-dimensional carbon composite material according to claim 1, wherein: In step 2, the concentration of tetrabutyl titanate after hydrolysis is 0.05-0.22 g / mL.

4. The method for preparing a titanium dioxide / three-dimensional carbon composite material according to claim 1, wherein: In step 2, the stirring and hydrolysis time is 12-24 hours, the temperature of the hydrothermal reaction is 160-200° C., and the insulation time is 16-24 hours.

5. The method for preparing a titanium dioxide / three-dimensional carbon composite material according to claim 1, wherein: In step 3, the centrifugal speed is 6000-10000 r / min, and the centrifugal time is 5-10 min; the vacuum drying temperature is 60° C., and the vacuum drying time is 12 h.

6. The method for preparing a titanium dioxide / three-dimensional carbon composite material according to claim 1, wherein: In step 4, the mass concentration of the suspension is 1-3 mg / mL.

7. The method for preparing a titanium dioxide / three-dimensional carbon composite material according to claim 1, wherein: In step 4, the freezing time is 8-12 hours and the drying time is 8-12 hours.

8. The method for preparing a titanium dioxide / three-dimensional carbon composite material according to claim 1, wherein: In step five, the temperature is raised to 600-900°C at a heating rate of 2-5°C for carbonization, and the holding time is 1.5-3h; the soaking time is 12-24h, and the water is changed 3-5 times; the vacuum drying temperature is 60°C, and the vacuum drying time is 12-24h.

9. A titanium dioxide / three-dimensional carbon composite material, characterized in that: The titanium dioxide / three-dimensional carbon composite material is prepared by the preparation method according to any one of claims 1 to 8.

10. The titanium dioxide / three-dimensional carbon composite material according to claim 9, characterized in that: The titanium dioxide / three-dimensional carbon composite material is applied in sodium ion batteries.

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