CN107611364A - A kind of polyimides/graphene flexible composite and its preparation method and application - Google Patents

Abstract

The present invention relates to a kind of polyimides/graphene flexible composite, its preparation process includes：The synthesis of viscous fluid of polyamide acid, polyimides coat the synthesis of graphene oxide composite material, the synthesis of polyimides/graphene flexible composite；The polyimides/graphene flexible composite may be used as the flexible self-supporting electrode material of lithium ion battery.The preparation method of the present invention is simple, and easily operated, cost is low, environmental protection；The polyimides that the present invention obtains/graphene flexible composite has preferable pliability and electric conductivity, has higher reversible capacity and excellent cyclical stability.

Description

A kind of polyimide/graphene flexible composite material and its preparation method and application

technical field

The invention belongs to the field of carbon nanocomposite materials, in particular to a polyimide/graphene flexible composite material and its preparation method and application.

Background technique

In order to meet the sustainable development of social economy and ecology, reduce the emission of carbon dioxide and the consumption of fossil fuels, the development of renewable clean energy devices has become a research hotspot for scientists. Lithium-ion battery is a secondary battery that uses lithium ions to migrate between positive and negative electrodes to store electrical energy. It has broad application prospects due to its long cycle life, high output power, and high energy density. However, with the continuous improvement of people's requirements for the energy storage performance of lithium-ion batteries, commercially available electrode materials can no longer meet people's needs, so the development of high-performance electrode materials has always been the focus of research. Graphene is widely used in catalyst supports, polymer nanocomposites, flexible substrate materials for energy conversion and storage devices due to its large specific surface area, good electrical conductivity, and excellent mechanical properties. One of the most promising new materials.

Polyimide is a typical conjugated ladder polymer, because of its excellent mechanical properties, high thermal stability, structural stability, and excellent electrochemical properties, it has been widely used in aerospace, national defense, and biomedicine And microelectronics, energy storage and other fields. However, as an electrode material, it has poor electrical conductivity, and the specific surface area of the film or particle is small, so that the active sites cannot be fully exposed, which seriously affects the energy storage performance. Therefore, it is of great significance to combine graphene with high specific surface area, good electrical conductivity, and excellent mechanical properties with polyimide to improve its electrical conductivity and specific surface area.

Contents of the invention

The technical problem to be solved by the present invention is to provide a polyimide/graphene flexible composite material and its preparation method and application, the preparation method is simple, low in cost, and the prepared polyimide/graphene flexible composite material has Excellent electrochemical performance.

The polyimide/graphene flexible composite material of the present invention has a three-dimensional interconnected porous structure, and the polyimide is coated on the graphene.

A kind of preparation method of polyimide/graphene flexible composite material of the present invention, concrete steps are as follows:

(1) Pyromellitic dianhydride and p-phenylenediamine are added to the solvent in a molar ratio of 1:1-1:3, dissolved, polycondensed under nitrogen environment to obtain a polyamic acid solution, and the obtained polyamic acid solution is mixed with Graphene oxide is mixed to form a uniform viscous liquid, wherein the mass ratio of pyromellitic dianhydride to graphene oxide is 15:1-35:1;

(2) adding the viscous solution in the step (1) to the solvent for dilution, hydrothermal reaction, and cooling to obtain polyimide-coated graphene oxide composite material;

(3) Dissolve graphene oxide in a solvent to form a graphene oxide solution, and the polyimide-coated graphene oxide composite material in step (2) and the graphene oxide solution are in a ratio of 1g: 10mL-3g: 10mL Mixing, suction filtration, and heat treatment under nitrogen atmosphere to obtain polyimide/graphene flexible composite material.

The solvents in the steps (1), (2) and (3) are all N,N-dimethylformamide.

The solid content of the polycondensation reaction in the step (1) is 10%-20%, the time of the polycondensation reaction is 15-25h, and the temperature of the polycondensation reaction is -5°C.

The solid content of the polycondensation reaction in the step (1) is 15%, and the time of the polycondensation reaction is 20h.

The concentration diluted in the step (2) is 9.1-45.5mg/mL; the process parameters of the hydrothermal reaction: the hydrothermal reaction temperature is 180°C, the constant temperature time is 6-12h, and the heating rate is 5°C/min.

The concentration diluted in the step (2) is 27.3mg/mL.

The concentration of the graphene oxide solution in the step (3) is 2mg/mL.

The technical parameters of the heat treatment in the step (3): the heat treatment temperature is 300-400° C., the constant temperature time is 2 hours, and the heating rate is 5° C./min.

A kind of polyimide/graphene flexible composite material of the present invention can be used as the flexible self-supporting electrode material of lithium ion battery.

A polyimide/graphene flexible composite material of the present invention has good electrical conductivity and high specific surface area, and can greatly improve the electrical conductivity of polyimide and fully expose active sites when used as an electrode material, which is beneficial to electrolyte Diffusion and adsorption of ions; moreover, the excellent electrical conductivity and mechanical properties of graphene enhance the overall mechanical flexibility and electrical conductivity of polyimide/graphene flexible composites. Therefore, the effective combination of polyimide and graphene can achieve a good synergistic reinforcement effect to prepare a composite electrode material with excellent performance.

Beneficial effect

(1) The preparation method of the present invention is simple, easy to operate, low in cost and environmentally friendly;

(2) the present invention obtains the three-dimensional interconnected porous polyimide/graphene flexible composite material;

(3) The polyimide/graphene flexible composite material that the present invention obtains has better flexibility and electrical conductivity, has higher reversible capacity and excellent cycle stability, and is ideal for new energy devices such as lithium-ion batteries electrode material.

Description of drawings

Fig. 1 is the picture of (A) polyimide/graphene flexible composite material in embodiment 1, the SEM figure of (B) polyimide/graphene flexible composite material section, (C) polyimide coating SEM images of graphene oxide composites;

Fig. 2 is the FTIR figure of polyimide-coated graphene oxide composite material in embodiment 1;

Fig. 3 is the cycle performance diagram of the polyimide/graphene flexible composite material in Example 1, the polyimide powder in Comparative Example 1 and the graphene film in Comparative Example 2 at a current density of 100 mA g ^-1 respectively.

detailed description

Below in conjunction with specific embodiment, further illustrate the present invention. 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. In addition, it should be understood that after reading the teachings 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 appended claims of the present application.

Example 1

(1) Prepared by the Hummers method, mix graphite, sodium nitrate, and concentrated sulfuric acid in an ice-water bath, add potassium permanganate in batches to react at 35°C for 2h, react at 98°C for 20min, add deionized water and stir to cool to room temperature before adding Hydrogen peroxide solution, stirring, static stratification, suction filtration, pickling, and water washing for many times to obtain graphene oxide.

(2) Add pyromellitic dianhydride (3.34g) and p-phenylenediamine (3.34g) into N,N-dimethylformamide for dissolution, and control the solid content at 10%. Under the condition of ℃, the polycondensation reaction was carried out for 20 hours to obtain a polyamic acid solution, and 0.1 g of graphene oxide in step (1) was mixed with the obtained polyamic acid solution to form a uniform viscous liquid.

(3) Add the viscous solution in step (2) to N,N-dimethylformamide and dilute to a concentration of 9.1 mg/mL, then carry out hydrothermal reaction on the diluted viscous solution, and the volume of the hydrothermal kettle 40mL, the filling volume is 30mL, the hydrothermal reaction temperature is 180°C, the heating rate is 5°C/min, the constant temperature time is 6h, and the polyimide-coated graphene oxide composite material is obtained by natural cooling to room temperature.

(4) Graphene oxide 0.1g in step (1) is dissolved in N,N-dimethylformamide to form a graphene oxide solution, the concentration of this solution is 2mg/mL, and the polymer in step (3) 1.0 g of the imide-coated graphene oxide composite material was mixed with 10.0 mL of the solution, filtered by suction, and heat-treated under a nitrogen atmosphere. Imine/graphene flexible composites.

Use Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectrometer (FTIR) to characterize the morphology and structure of the polyimide/graphene flexible composite material prepared in the present embodiment 1, and the results are as follows:

(1) The SEM test results in Fig. 1 show that the polyimide/graphene flexible composite material prepared in Example 1 has a three-dimensional interconnected porous structure, and the polyimide is coated on the graphene.

(2) The FTIR test results in Fig. 2 show that: the vibration peaks at 1774cm ^-1 and 1709cm ^-1 of the polyimide-coated graphite oxide prepared in Example 1 belong to the polyimide ring carbonyl (C=O ) symmetric and asymmetric peaks; the vibration peak at 1372cm ^-1 is attributed to the absorption vibration peak of the CN bond of the polyimide ring; the vibration peak at 1124cm ^-1 and 725cm ^-1 is attributed to the distortion of the polyimide ring Deformation vibration peaks. The infrared characteristic vibration peak fully demonstrates the successful preparation of polyimide-coated graphene.

Example 2

(1) Prepared by the Hummers method, mix graphite, sodium nitrate, and concentrated sulfuric acid in an ice-water bath, add potassium permanganate in batches to react at 35°C for 2h, react at 98°C for 20min, add deionized water and stir to cool to room temperature before adding Hydrogen peroxide solution, stirring, static stratification, suction filtration, pickling, and water washing for many times to obtain graphene oxide.

(2) Add pyromellitic dianhydride (3.34g) and p-phenylenediamine (5.01g) into N,N-dimethylformamide for dissolution, and control the solid content at 15%. Under the condition of ℃, the polycondensation reaction was carried out for 20 hours to obtain a polyamic acid solution, and 0.15 g of graphene oxide in step (1) was mixed with the obtained polyamic acid solution to form a uniform viscous liquid.

(3) Add the viscous solution in step (2) to N,N-dimethylformamide and dilute to a concentration of 27.3mg/mL, then carry out hydrothermal reaction on the diluted viscous solution, and the volume of the hydrothermal kettle 40mL, the filling volume is 30mL, the hydrothermal reaction temperature is 180°C, the heating rate is 5°C/min, the constant temperature time is 9h, and the polyimide-coated graphene oxide composite material is obtained by natural cooling to room temperature.

(4) 0.15g of graphene oxide in step (1) is dissolved in N, N-dimethylformamide to form a graphene oxide solution, the concentration of this solution is 2mg/mL, and the polymer in step (3) 1.5g of imide-coated graphene oxide composite material was mixed with 10.0mL of the solution, filtered by suction, and heat-treated under nitrogen atmosphere. Imine/graphene flexible composites.

Example 3

(1) Prepared by the Hummers method, mix graphite, sodium nitrate, and concentrated sulfuric acid in an ice-water bath, add potassium permanganate in batches to react at 35°C for 2h, react at 98°C for 20min, add deionized water and stir to cool to room temperature before adding Hydrogen peroxide solution, stirring, static stratification, suction filtration, pickling, and water washing for many times to obtain graphene oxide.

(2) Add pyromellitic dianhydride (3.34g) and p-phenylenediamine (6.68g) into N,N-dimethylformamide for dissolution, and control the solid content at 20%. Under the condition of ℃, the polycondensation reaction was carried out for 20 hours to obtain a polyamic acid solution, and 0.2 g of graphene oxide in step (1) was mixed with the obtained polyamic acid solution to form a uniform viscous liquid.

(3) Add the viscous solution in step (2) to N,N-dimethylformamide and dilute to a concentration of 45.5 mg/mL, then carry out hydrothermal reaction on the diluted viscous solution, and the volume of the hydrothermal kettle 40mL, the filling volume is 30mL, the hydrothermal reaction temperature is 180°C, the heating rate is 5°C/min, the constant temperature time is 12h, and the polyimide-coated graphene oxide composite material is obtained by natural cooling to room temperature.

(4) Get 0.2g graphene oxide in step (1) and dissolve it in N,N-dimethylformamide to form a graphene oxide solution, the concentration of this solution is 2mg/mL, and the polymer in step (3) 2.0 g of the imide-coated graphene oxide composite material was mixed with 10.0 mL of the solution, filtered by suction, and heat-treated under a nitrogen atmosphere. Imine/graphene flexible composites.

Comparative example 1

(1) Add pyromellitic dianhydride (3.34g) and p-phenylenediamine (3.34g) into N,N-dimethylformamide for dissolution, and control the solid content at 10%. Under the condition of ℃, the polycondensation reaction was carried out for 20 hours to obtain a polyamic acid solution.

(2) Add the polyamic acid solution in step (1) to N,N-dimethylformamide and dilute to a concentration of 9.1mg/mL, then carry out the hydrothermal reaction of the diluted viscous liquid, and heat it in a kettle The volume is 40mL, the filling volume is 30mL, the temperature of the hydrothermal reaction is 180°C, the heating rate is 5°C/min, the constant temperature time is 6h, and the polyimide solution is naturally cooled to room temperature.

(3) Suction filter the polyimide solution in step (2), heat treatment under nitrogen atmosphere, the heat treatment temperature is 300°C, the heating rate is 5°C/min, and the constant temperature time is 2h, to obtain polyimide powder.

Comparative example 2

(1) Prepared by the Hummers method, mix graphite, sodium nitrate, and concentrated sulfuric acid in an ice-water bath, add potassium permanganate in batches to react at 35°C for 2h, react at 98°C for 20min, add deionized water and stir to cool to room temperature before adding Hydrogen peroxide solution, stirring, static stratification, suction filtration, pickling, and water washing for many times to obtain graphene oxide.

(2) 0.1 g of graphene oxide in step (1) is dissolved in N, N-dimethylformamide to form a graphene oxide solution, the concentration of the solution is 2 mg/mL, suction filtered, and heat treated in a nitrogen environment, The heat treatment temperature is 300° C., the heating rate is 5° C./min, and the constant temperature time is 2 hours to obtain a graphene film.

In the electrochemical test, the polyimide/graphene flexible composite material prepared in Example 1, the polyimide powder prepared in Comparative Example 1, and the graphene film prepared in Comparative Example 2 were used as the positive electrode, and the lithium sheet was used as the positive electrode. The negative electrode is assembled with a button-type half-cell, and the charge-discharge curve of the battery is used to study the capacitance of the composite material.

The electrochemical test results in Figure 3 show that the polyimide/graphene flexible composite material prepared in Example 1 has a higher reversible capacity value and better cycle stability. After 200 charge-discharge cycles, its reversible capacity can still be as high as 53mA hg ^-1 . This indicates that the construction of polyimide/graphene flexible composites with a three-dimensional interconnected porous structure plays a very important role in the improvement of its reversible capacity value and cycle stability.

Claims (10)

1. A polyimide/graphene flexible composite material is characterized in that it has a three-dimensional interconnected porous structure, and polyimide is coated on the graphene. 2. A preparation method of polyimide/graphene flexible composite material, the concrete steps are as follows: (1) Pyromellitic dianhydride and p-phenylenediamine are added to the solvent in a molar ratio of 1:1-1:3, dissolved, polycondensed under nitrogen environment to obtain a polyamic acid solution, and the obtained polyamic acid solution is mixed with Graphene oxide is mixed to form a uniform viscous liquid, wherein the mass ratio of pyromellitic dianhydride to graphene oxide is 15:1-35:1; (2) adding the viscous solution in the step (1) to the solvent for dilution, hydrothermal reaction, and cooling to obtain polyimide-coated graphene oxide composite material; (3) Dissolve graphene oxide in a solvent to form a graphene oxide solution, and the polyimide-coated graphene oxide composite material in step (2) and the graphene oxide solution are in a ratio of 1g: 10mL-3g: 10mL Mixing, suction filtration, and heat treatment under nitrogen atmosphere to obtain polyimide/graphene flexible composite material. 3. according to the preparation method of a kind of polyimide/graphene flexible composite material described in claim 2, it is characterized in that, in described step (1), (2), (3), solvent is N, N -dimethylformamide. 4. according to the preparation method of a kind of polyimide/graphene flexible composite material described in claim 2, it is characterized in that, the solid content of polycondensation reaction in described step (1) is 10%-20%, polycondensation reaction The time of the reaction is 15-25h, and the temperature of the polycondensation reaction is -5°C. 5. according to the preparation method of a kind of polyimide/graphene flexible composite material described in claim 2, it is characterized in that, the solid content of polycondensation reaction is 15% in the described step (1), and the time of polycondensation reaction is 20h. 6. according to the preparation method of a kind of polyimide/graphene flexible composite material described in claim 2, it is characterized in that, the concentration diluted in the described step (2) is 9.1-45.5mg/mL; Hydrothermal reaction Process parameters: the hydrothermal reaction temperature is 180°C, the constant temperature time is 6-12h, and the heating rate is 5°C/min. 7. according to the preparation method of a kind of polyimide/graphene flexible composite material according to claim 2, it is characterized in that, the concentration diluted in the described step (2) is 27.3mg/mL. 8. according to the preparation method of a kind of polyimide/graphene flexible composite material described in claim 2, it is characterized in that, the concentration of graphene oxide solution in the described step (3) is 2mg/mL. 9. according to the preparation method of a kind of polyimide/graphene flexible composite material described in claim 2, it is characterized in that, the processing parameter of heat treatment in described step (3): heat treatment temperature is 300-400 ℃, constant temperature The time is 2h, and the heating rate is 5°C/min. 10. an application of polyimide/graphene flexible composite material as claimed in claim 1, is characterized in that, is used as the flexible self-supporting electrode material of lithium-ion battery.