Titanium dioxide / graphene composite material, and preparation method and application thereof

Abstract

The application belongs to the technical field of battery materials, and particularly relates to a titanium dioxide / graphene composite material and a preparation method and application thereof. The preparation method of the titanium dioxide / graphene composite material comprises the following steps: S1, stirring titanium alkoxide into anhydrous ethanol to form a uniform and transparent titanium alkoxide solution; S2, ultrasonically dispersing graphene in pure water to form a uniform graphene dispersion liquid; S3, dropping the titanium alkoxide solution into the graphene dispersion liquid to perform stirring treatment to obtain a mixed liquid; S4, dropping glacial acetic acid into the mixed liquid to perform heating and stirring to form a sol, and after aging, performing drying and crushing to obtain a composite precursor powder; and S5, performing annealing treatment on the composite precursor powder under a nitrogen atmosphere, and cooling to room temperature to obtain the titanium dioxide / graphene composite material. When applied to a battery, the application can ensure extremely low electrode internal resistance, and simultaneously strongly inhibit a hydrogen evolution side reaction.

Description

Technical Field

[0001] This invention belongs to the technical field of battery materials, specifically relating to a titanium dioxide / graphene composite material, its preparation method, and its application. Background Technology

[0002] Lead-acid batteries, as one of the oldest electrochemical energy storage systems, remain a mainstream choice in automotive starting power supplies, electric light vehicle power sources, industrial energy storage, and communication backup power supplies due to their significant cost advantages, high technical reliability, complete process technology, and excellent instantaneous high-current discharge capability. However, during long-term cycling, especially under partial state of charge or overcharge conditions, severe hydrogen evolution side reactions continuously occur at the negative electrode. Lead sulfate has a lower hydrogen overpotential than metallic lead, providing a more favorable environment for hydrogen evolution. Long-term presence of lead sulfate leads to gradual recrystallization and coarsening, forming irreversible sulfation, further exacerbating hydrogen evolution and capacity loss. Hydrogen evolution not only directly causes energy loss and reduces charging efficiency but also triggers electrolyte dehydration and density imbalance. Over time, the evolved hydrogen damages the structure of the negative electrode active material, accelerating its softening and shedding, thus accelerating capacity decay and battery failure, easily leading to decreased charging efficiency and safety risks. Therefore, effectively suppressing hydrogen evolution is a core technology for improving the overall performance of lead-acid batteries.

[0003] To address this challenge, the industry commonly employs the method of adding functional materials to the negative electrode lead paste, primarily focusing on carbon materials and metal oxides. Carbon materials (such as carbon black, graphene, and carbon nanotubes) aim to construct a highly conductive network, improving the poor conductivity of the negative electrode active material (lead / lead sulfate), thereby reducing polarization and enhancing power performance and charge acceptance. However, many high specific surface area carbon materials, due to their surface characteristics, may actually provide active sites for hydrogen ion reduction, posing a potential risk of catalyzing hydrogen evolution. On the other hand, metal oxides (such as ZnO and TiO2) have been proven to suppress hydrogen evolution by altering electrode surface properties and increasing hydrogen evolution overpotential. However, these materials typically have poor conductivity, and adding large quantities can significantly increase electrode internal resistance, impairing the battery's high-rate discharge performance, creating a performance contradiction between "suppressing hydrogen evolution" and "maintaining conductivity."

[0004] In recent years, researchers have attempted to combine these two technologies to achieve synergy. For example, Chinese patent application (publication number CN113764627A) discloses a high-performance lead-carbon battery negative electrode paste formulation and its preparation method, which uses graphene and carbon nanotubes. However, its hydrogen suppression mechanism still mainly relies on traditional barium sulfate, with limited effectiveness. Chinese patent application (publication number CN117199344A) discloses a negative electrode paste and its preparation method that inhibits hydrogen evolution and extends battery cycle life. It combines modified graphene and zinc oxide, which provides some performance improvement. However, its physical mixing method makes it difficult to achieve optimal synergy of functional components at the nanoscale. This often leads to oxide agglomeration blocking conductive pathways, or the carbon material failing to effectively modify the oxide surface. Consequently, the improvement in conductivity and the inhibition of hydrogen evolution are not maximized simultaneously, and the synergistic effect does not meet expectations.

[0005] In summary, current technologies have not fundamentally solved the performance conflict between carbon materials and metal oxides. Developing a novel composite material additive that can achieve a precise and robust combination of a highly conductive network and highly dispersed hydrogen-suppressing active sites in the microstructure, thereby effectively suppressing hydrogen evolution side reactions while ensuring extremely low electrode internal resistance, has become an urgent need to promote the upgrading of lead-acid battery technology and has significant research value and application prospects. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a titanium dioxide / graphene composite material, its preparation method, and its applications. The complete three-dimensional graphene network in the composite material significantly enhances the electronic conductivity of the negative electrode active material, substantially reduces charge transfer impedance, and improves the battery's power characteristics and charge acceptance. The titanium dioxide nanounits uniformly anchored on the graphene surface effectively increase the overpotential for hydrogen evolution through interfacial electronic effects and surface property regulation, kinetically suppressing hydrogen evolution side reactions during charging. The synergistic effect of these two materials resolves the contradictions caused by the performance deficiencies of individual materials, significantly improving hydrogen evolution suppression and cycle stability while reducing battery internal resistance. This invention effectively solves the common technical problems of insufficient functional synergy between carbon materials and metal oxides in existing lead-acid battery negative electrode additives, making it difficult to simultaneously achieve high conductivity and strong hydrogen evolution suppression.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0008] A first aspect of the present invention provides a method for preparing a titanium dioxide / graphene composite material, comprising the following steps:

[0009] S1. Add titanium alkoxide to anhydrous ethanol and stir to form a uniform and transparent titanium alkoxide solution;

[0010] S2. Graphene is ultrasonically dispersed in pure water to form a uniform graphene dispersion.

[0011] S3. The titanium alkoxide solution described in step S1 is added dropwise to the graphene dispersion described in step S2 and stirred to obtain a mixture;

[0012] S4. Add glacial acetic acid dropwise to the mixture described in step S3, heat and stir to form a sol, age it, dry it and pulverize it to obtain composite precursor powder;

[0013] S5. Anneal the composite precursor powder obtained in step S4 under a nitrogen atmosphere and cool it to room temperature to obtain a titanium dioxide / graphene composite material.

[0014] The titanium dioxide / graphene composite material of this invention constructs a strongly coupled nanocomposite structure of titanium dioxide and graphene, simultaneously optimizing conductivity and interfacial properties. Through sol-gel and low-temperature heat treatment, uniformly anchored titanium dioxide nanounits are formed in situ on the graphene surface, with stable Ti-OC chemical bonds between them. This structure maximizes the preservation of the intrinsic high conductivity network integrity of graphene while achieving high dispersion and maximizing the active interface with low titanium dioxide loading. The three-dimensional continuous conductive pathway constructed by graphene significantly reduces the ohmic impedance and charge transfer resistance of the electrodes, improving the electron transport efficiency and reaction kinetics of the active material.

[0015] As a preferred embodiment of the present invention, the stirring time in step S1 is 10~60 min, the temperature is 25~65℃, and the rotation speed is 400~800 rpm.

[0016] As a preferred technical solution of the present invention, the ultrasonic power of ultrasonic dispersion in step S2 is 300~400W and the ultrasonic time is 10~60min.

[0017] As a preferred technical solution of the present invention, the stirring conditions in step S3 are: stirring time of 1~5h, stirring temperature of 25~100℃, and stirring speed of 400~800rpm.

[0018] As a preferred technical solution of the present invention, the heating and stirring conditions in step S4 are: temperature of 25~65℃, time of 1~5h, and rotation speed of 400~800rpm.

[0019] As a preferred embodiment of the present invention, the aging time is 12-48 hours.

[0020] As a preferred embodiment of the present invention, the drying temperature is 50~80℃.

[0021] As a preferred embodiment of the present invention, the power of the pulverizer is 1000~1200W and the rotation speed is 28000~30000r / min.

[0022] As a preferred technical solution of the present invention, the annealing conditions in step S5 are: heating rate of 3~5℃ / min, annealing temperature of 200~600℃, and annealing time of 1~5h.

[0023] The annealing treatment of this invention can enhance the bonding force between TiO2 nanoparticles and graphene sheets, prevent particle shedding during cycling, and maintain electrode integrity. Unannealed materials are prone to pulverization or peeling under repeated volume changes, resulting in rapid capacity decay. At the same time, unannealed TiO2 is usually amorphous or has poor crystallinity. During charge and discharge, low crystallinity may lead to structural collapse or irreversible phase transition, thereby reducing material performance.

[0024] As a preferred embodiment of the present invention, the mass ratio of the titanium alkoxide to the anhydrous ethanol is 1:(2-20).

[0025] As a preferred embodiment of the present invention, the mass ratio of the titanium alkoxide to the graphene is 1:(2-20).

[0026] As a preferred embodiment of the present invention, the mass ratio of the titanium alkoxide to the glacial acetic acid is 1:(1-5).

[0027] As a preferred embodiment of the present invention, the mass ratio of the graphene to the pure water is 1:(10-200).

[0028] As a preferred embodiment of the present invention, the titanium alkoxide is selected from one or more of tetraisopropyl titanate, tetraethyl titanate, and tetrabutyl titanate.

[0029] As a preferred technical solution of the present invention, the method for preparing the modified three-dimensional porous graphene is as follows: using graphene oxide dispersion and polyvinyl alcohol as raw materials, and preparing three-dimensional porous graphene with nitric acid solution, the three-dimensional porous graphene and cerium chloride heptahydrate are mixed and subjected to hydrothermal reaction to obtain modified three-dimensional porous graphene.

[0030] The modified three-dimensional porous graphene of this invention has a high specific surface area and porous structure, providing ample channels for ion transport and expanding the contact area of ​​active materials. The three-dimensional interconnected structure can construct continuous conductive pathways in lead paste, significantly reducing electron transport resistance. The modification of cerium can adjust the electronic structure and further improve conductivity. The excellent conductive network and ion channels make the current distribution more uniform, promote the full participation of particles inside the electrode in the reaction, improve the utilization rate of active materials, and thus enhance the overall performance of the material.

[0031] As a preferred technical solution of the present invention, the preparation steps of the three-dimensional porous graphene are as follows: by weight, 400-500 parts of 1 mg / mL graphene oxide dispersion and 40-80 parts of 1 mg / mL polyvinyl alcohol aqueous solution are mixed evenly, freeze-dried to obtain mixed powder, 1-2 parts of the mixed powder are added to 60-80 parts of 40% nitric acid solution and stirred and refluxed for 10-12 hours, centrifuged, washed with deionized water, and vacuum dried to obtain three-dimensional porous graphene.

[0032] The nitric acid solution of the present invention has a dual function. On the one hand, nitric acid can act as a decomposing agent for polyvinyl alcohol, thereby achieving the decomposition and pore-forming of polyvinyl alcohol. On the other hand, nitric acid can act as an activator for graphene, introducing more oxygen-containing groups on the surface of three-dimensional porous graphene through long-term stirring and reflux, which can provide additional transport channels and thus improve the electrochemical performance of the material.

[0033] As a preferred technical solution of the present invention, the hydrothermal reaction steps are as follows: by weight, 1-2 parts of the three-dimensional porous graphene are added to 500-600 parts of deionized water and ultrasonically dispersed for 2-4 hours, then 0.16-0.24 parts of cerium chloride heptahydrate are added and magnetically stirred for 3-5 hours, hydrothermally treated at 120-130°C for 10-12 hours, filtered, washed with deionized water, and freeze-dried to obtain modified three-dimensional porous graphene.

[0034] This invention first adds polyvinyl alcohol to a graphene oxide dispersion, using polyvinyl alcohol as a structure directing agent and nitric acid solution to achieve cross-linking and pore formation, thereby obtaining three-dimensional porous graphene. Subsequently, the three-dimensional porous graphene is mixed with cerium chloride heptahydrate, and cerium is fixed in situ on the surface and inner wall of the pores of the three-dimensional porous graphene by hydrothermal method. In addition, some cerium forms CeO2 nanoparticles during the hydrothermal process and is firmly anchored on the pore walls, thereby obtaining modified three-dimensional porous graphene.

[0035] In this invention, the Ce–O groups in the modified three-dimensional porous graphene can coordinate with titanium ions in titanium alkoxide to form Ti-O-Ce bonds. At the same time, some CeO2 and TiO2 can form heterojunctions to enhance interfacial charge transfer. The bonding between titanium dioxide and graphene is strengthened by cerium, which significantly improves the performance of the composite material.

[0036] A second aspect of the present invention provides a titanium dioxide / graphene composite material prepared by the method described in the first aspect.

[0037] A third aspect of the present invention provides an application of a titanium dioxide / graphene composite material prepared by the method described in the first aspect in a negative electrode lead paste.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The titanium dioxide / graphene composite material of the present invention significantly suppresses the hydrogen evolution side reaction of the negative electrode through interfacial electronic regulation. The interfacial electronic interaction between graphene and surface titanium dioxide nanounits effectively modulates the electronic state and adsorption performance of the composite material surface. This modulation increases the adsorption energy barrier of hydrogen atoms on the electrode surface, thereby significantly increasing the overpotential of the hydrogen evolution reaction.

[0040] (2) The titanium dioxide / graphene composite material of the present invention can enhance the stability of the electrode structure and has application feasibility; the mechanical flexibility of graphene buffers the volume strain in the cycle of active material, and the strong interfacial bonding ensures the durability of titanium dioxide function, which together delays capacity decay and prolongs cycle life; the design achieves significant performance improvement under low titanium dioxide load, balancing effect and cost; its preparation process is compatible with the traditional lead paste process, the material is easy to disperse, and has good industrialization prospects. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is the XRD pattern of the modified three-dimensional porous graphene in Example 1 of the present invention. Detailed Implementation

[0043] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0044] The sources of some components in the examples and comparative examples are as follows:

[0045] Commercially available titanium dioxide powder, product number T431952, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0046] Commercially available graphene powder, product number G196544, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0047] Tetraisopropyl titanate, CAS No. 546-68-9, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0048] Tetraethyl titanate, CAS No. 3087-36-3, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0049] Tetrabutyl titanate, CAS No. 5593-70-4, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0050] Anhydrous ethanol, CAS No. 64-17-5, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0051] Glacial acetic acid, CAS No. 64-19-7, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0052] Graphene oxide dispersion, catalog number G196548, with a concentration of 1 mg / mL, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0053] Polyvinyl alcohol, product number P434374, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0054] Cerium chloride heptahydrate, CAS No. 18618-55-8, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0055] Example 1

[0056] This embodiment provides a method for preparing a titanium dioxide / graphene composite material, including the following steps:

[0057] S1. By weight, add 5 parts of tetrabutyl titanate to 50 parts of anhydrous ethanol and stir (for 60 minutes, at 25°C and at 400 rpm) to form a uniform and transparent titanium alkoxide solution.

[0058] S2. Disperse 10 parts of graphene powder in 300 parts of pure water by ultrasonication (ultrasonic power of 300W, ultrasonic time of 60min) to form a uniform graphene dispersion.

[0059] S3. Add 50 parts of the titanium alkoxide solution described in step S1 dropwise to 300 parts of the graphene dispersion described in step S2 and stir (stirring time is 2 hours, stirring temperature is 100℃, stirring speed is 800 rpm) to obtain a mixture.

[0060] S4. Add 5 parts of glacial acetic acid to the mixture described in step S3, heat and stir (temperature 65℃, time 1h, speed 800rpm) to form a sol, age for 48h, dry at 60℃ for 12h, and crush into powder using a crusher (power 1200W, speed 30000r / min) to obtain composite precursor powder.

[0061] S5. The composite precursor powder described in step S4 is annealed in a nitrogen atmosphere, heated to 500°C at a heating rate of 5°C / min for 2 hours, and then naturally cooled to room temperature under nitrogen protection to obtain the titanium dioxide / graphene composite material.

[0062] Example 2

[0063] This embodiment provides a method for preparing a titanium dioxide / graphene composite material. The difference from Example 1 is that 5 parts of tetrabutyl titanate are replaced with 7.5 parts of tetrabutyl titanate, while the rest remains the same as in Example 1.

[0064] Example 3

[0065] This embodiment provides a method for preparing a titanium dioxide / graphene composite material. The difference from Example 1 is that 5 parts of tetrabutyl titanate are replaced with 2.5 parts of tetrabutyl titanate, while the rest remains the same as in Example 1.

[0066] Example 4

[0067] This embodiment provides a method for preparing a titanium dioxide / graphene composite material. The difference from Example 1 is that 10 parts of graphene powder are replaced with 10 parts of modified three-dimensional porous graphene, while the rest remains the same as in Example 1.

[0068] Preparation of the modified three-dimensional porous graphene: 500 parts by weight of 1 mg / mL graphene oxide dispersion and 80 parts by weight of 1 mg / mL polyvinyl alcohol aqueous solution were mixed evenly and freeze-dried to obtain a mixed powder. Two parts of the mixed powder were added to 80 parts by weight of 40% nitric acid solution and stirred under reflux for 12 h. After centrifugation, the mixture was washed with deionized water and vacuum dried to obtain three-dimensional porous graphene. Two parts of the three-dimensional porous graphene were added to 600 parts by weight of deionized water and ultrasonically dispersed for 4 h. Then, 0.24 parts by weight of cerium chloride heptahydrate were added and magnetically stirred for 5 h. The mixture was then hydrothermally treated at 130℃ for 10 h, filtered, washed with deionized water, and freeze-dried to obtain the modified three-dimensional porous graphene.

[0069] Comparative Example 1

[0070] The difference between this comparative example and Example 1 is that 5 parts of tetrabutyl titanate were replaced with 1 part of titanium dioxide.

[0071] Comparative Example 2

[0072] The difference between this comparative example and Example 1 is that step S5 does not involve annealing.

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 4 is that deionized water was used instead of nitric acid solution for the preparation of three-dimensional porous graphene.

[0075] Application examples

[0076] The above-described embodiments, comparative examples, and commercially available graphene powder were used as composite additives in the fabrication of negative electrode lead paste and electrode plates. The specific steps are as follows:

[0077] By weight, 100 parts of lead powder, 1.5 parts of composite additives, 0.15 parts of sodium lignosulfonate, 0.4 parts of humic acid, 0.8 parts of ultrafine barium sulfate, and 0.15 parts of polyester short fiber are mixed evenly, then 11 parts of water are added and stirred. Then, 9 parts of dilute sulfuric acid are added to adjust the density to 4.3 g / cm³ to obtain negative electrode lead paste.

[0078] The negative electrode lead paste was coated onto the grid and cured at 95% humidity and 35℃ for 36 hours, followed by drying at 70℃ for 5 hours and 40℃ for 2 hours to obtain the negative electrode plate.

[0079] Performance testing:

[0080] The positive electrode of the battery uses a conventional PbO2-coated grid as the active material carrier, and the negative electrode uses the negative electrode plate prepared in the application example. The electrolyte is a dilute sulfuric acid aqueous solution with an initial density of 1.28 ± 0.01 g / cm³. 3 .

[0081] Initial discharge capacity (Ah): After constant current and constant voltage charging of the battery according to national standard GB / T 7403.1-2018, the discharge capacity is measured by constant current discharge at 0.2 C to the termination voltage.

[0082] Cycle life (cycles): According to IEC61427-1:2013 standard, the battery is cycled at 100% depth of discharge, and the number of cycles is recorded when the battery capacity decays to 80% of the initial capacity.

[0083] The three-electrode system was tested using an electrochemical workstation: linear scanning voltammetry at the negative electrode (scan rate 50 mV / s); electrochemical impedance spectroscopy (EIS) with an amplitude of 5 mV and a test frequency range of 0.01 Hz to 10 kHz.

[0084] The performance test data above are shown in Table 1.

[0085] Table 1 Performance Test Results

[0086]

[0087] This invention utilizes a TiO2 / graphene strongly coupled structure constructed through sol-gel and heat treatment to effectively suppress hydrogen evolution side reactions while providing a highly conductive network. By controlling the TiO2 content and composite process, this invention successfully prepared a negative electrode additive with high conductivity, strong hydrogen evolution suppression capability, and excellent structural stability, providing an effective solution to the problems of hydrogen evolution and capacity decay in lead-acid battery negative electrodes.

[0088] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a titanium dioxide / graphene composite material, characterized in that, Includes the following steps: S1. Add titanium alkoxide to anhydrous ethanol and stir to form a uniform and transparent titanium alkoxide solution; S2. Modified three-dimensional porous graphene is ultrasonically dispersed in pure water to form a uniform graphene dispersion. S3. The titanium alkoxide solution described in step S1 is added dropwise to the graphene dispersion described in step S2 and stirred to obtain a mixture; S4. Add glacial acetic acid dropwise to the mixture described in step S3, heat and stir to form a sol, age it, dry it and pulverize it to obtain composite precursor powder; S5. Anneal the composite precursor powder obtained in step S4 under a nitrogen atmosphere and cool it to room temperature to obtain a titanium dioxide / graphene composite material. The modified three-dimensional porous graphene is prepared by using graphene oxide dispersion and polyvinyl alcohol as raw materials, combined with nitric acid solution to prepare three-dimensional porous graphene, and then mixing the three-dimensional porous graphene with cerium chloride heptahydrate for hydrothermal reaction to obtain modified three-dimensional porous graphene.

2. The method for preparing a titanium dioxide / graphene composite material according to claim 1, characterized in that, The stirring time in step S1 is 10~60 min, the temperature is 25~65℃, and the speed is 400~800 rpm; The ultrasonic power for ultrasonic dispersion in step S2 is 300~400W, and the ultrasonic time is 10~60min; The stirring conditions described in step S3 are: stirring time of 1-5 hours, stirring temperature of 25-100°C, and stirring speed of 400-800 rpm.

3. The method for preparing a titanium dioxide / graphene composite material according to claim 1, characterized in that, The heating and stirring conditions in step S4 are as follows: temperature 25~65℃, time 1~5h, rotation speed 400~800rpm; aging time 12~48h; drying temperature 50~80℃; and pulverizer power 1000~1200W, rotation speed 28000~30000r / min. The annealing conditions described in step S5 are: heating rate of 3~5℃ / min, annealing temperature of 200~600℃, and annealing time of 1~5h.

4. The method for preparing a titanium dioxide / graphene composite material according to claim 1, characterized in that, The mass ratio of the titanium alkoxide to the anhydrous ethanol is 1:(2-20); the mass ratio of the titanium alkoxide to the graphene is 1:(2-20); the mass ratio of the titanium alkoxide to the glacial acetic acid is 1:(1-5); and the mass ratio of the graphene to the pure water is 1:(10-200).

5. The method for preparing a titanium dioxide / graphene composite material according to claim 1, characterized in that, The titanium alkoxide is selected from one or more of tetraisopropyl titanate, tetraethyl titanate, and tetrabutyl titanate.

6. The method for preparing a titanium dioxide / graphene composite material according to claim 1, characterized in that, The preparation steps of the three-dimensional porous graphene are as follows: by weight, 400-500 parts of 1 mg / mL graphene oxide dispersion and 40-80 parts of 1 mg / mL polyvinyl alcohol aqueous solution are mixed evenly, freeze-dried to obtain mixed powder, 1-2 parts of the mixed powder are added to 60-80 parts of 40% nitric acid solution and stirred and refluxed for 10-12 hours, centrifuged, washed with deionized water, and vacuum dried to obtain three-dimensional porous graphene.

7. The method for preparing a titanium dioxide / graphene composite material according to claim 1, characterized in that, The hydrothermal reaction steps are as follows: by weight, 1-2 parts of the three-dimensional porous graphene are added to 500-600 parts of deionized water and ultrasonically dispersed for 2-4 hours, then 0.16-0.24 parts of cerium chloride heptahydrate are added and magnetically stirred for 3-5 hours, hydrothermally treated at 120-130℃ for 10-12 hours, filtered, washed with deionized water, and freeze-dried to obtain modified three-dimensional porous graphene.

8. A titanium dioxide / graphene composite material, characterized in that, It is prepared according to any one of claims 1 to 7.

9. The application of the titanium dioxide / graphene composite material obtained by the preparation method according to any one of claims 1 to 7 in negative electrode lead paste.

Images