Graphene / polyaniline composite film with gradient structure as well as preparation method and application of graphene / polyaniline composite film

Abstract

The invention discloses a graphene / polyaniline composite film with a gradient structure and a preparation method and application thereof, the preparation method comprises the following steps: S1, preparing a coating template, and uniformly coating the coating template with a graphene oxide dispersion liquid to obtain a graphene oxide porous template; s2, performing electrochemical reduction on the graphene oxide porous template to obtain a reduced graphene oxide porous template; and S3, carrying out polyaniline electrodeposition on the reduced graphene oxide porous template to obtain the graphene / polyaniline composite film with a gradient structure. The graphene / polyaniline composite film prepared by the invention has a gradient structure, and can improve various ion energy storage characteristics and conductivity of the material.

Description

Technical Field

[0001] The present invention relates to the technical fields of energy storage and new materials, and particularly relates to a graphene / polyaniline composite film with a gradient structure, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of the global economy, the demand for energy is also increasing rapidly. However, environmental problems caused by the use of fossil energy around the world are becoming increasingly serious. To balance the growing energy demand and the increasingly serious environmental problems, gradually replacing fossil energy with renewable energy is the best choice. However, the volatility and intermittency of renewable energy mean that they cannot directly provide a continuous and stable power supply, and a large-scale stationary energy storage system (EES) is required for transition.

[0003] Aqueous hybrid capacitors are a new type of energy storage device. They use an aqueous electrolyte and combine the working principles of supercapacitors and batteries. They have the characteristics of high safety, environmental friendliness, and low cost, and are very attractive for large-scale EES storage. However, the transition metal oxides, layered double hydroxides, and intercalation compounds commonly used in existing aqueous hybrid capacitors have problems such as low electronic conductivity and poor structural stability, which limit their development. At the same time, it is difficult to achieve the coordinated regulation of electron transport and ion diffusion in conventional homogeneous graphene / polyaniline composites. Summary of the Invention

[0004] In view of the above problems, the present invention aims to provide a graphene / polyaniline composite film with a gradient structure, a preparation method thereof, and an application thereof.

[0005] The technical solution of the present invention is as follows:

[0006] On the one hand, a preparation method of a graphene / polyaniline composite film with a gradient structure is provided, including the following steps:

[0007] S1: Prepare a coating template, and uniformly coat a graphene oxide dispersion on the coating template to obtain a graphene oxide porous template;

[0008] S2: Electrochemically reduce the graphene oxide porous template to obtain a reduced graphene oxide porous template;

[0009] S3: Perform electrodeposition of polyaniline on the reduced graphene oxide porous template to obtain a graphene / polyaniline composite film with a gradient structure.

[0010] Preferably, in step S1, the coating template is titanium-platinum, a graphite sheet, or stainless steel.

[0011] Preferably, in step S1, the graphene oxide dispersion is uniformly coated on the coating template by a casting method.

[0012] Preferably, in step S1, the concentration of the graphene oxide dispersion is 15-25 mg / mL.

[0013] Preferably, in step S2, during the electrochemical reduction, a constant voltage reduction method or a cyclic voltammetry reduction method is adopted.

[0014] Preferably, in step S3, during the electrodeposition of polyaniline, the concentration of polyaniline is 0.01-0.1 mol / L.

[0015] Preferably, in step S3, during the electrodeposition of polyaniline, a two-electrode system or a three-electrode system is adopted.

[0016] Preferably, in step S3, during the electrodeposition of polyaniline, a cyclic voltammetry deposition method is adopted.

[0017] On the other hand, there is also provided a gradient-structured graphene / polyaniline composite film prepared by the preparation method of the gradient-structured graphene / polyaniline composite film described in any one of the above, and its application as an electrode material in an aqueous hybrid capacitor or a zinc-iodine battery.

[0018] The beneficial effects of the present invention are as follows:

[0019] The present invention can prepare a gradient-structured graphene / polyaniline composite film. Through the gradient structure design of the present invention, the inner dense layer can be used to optimize the electron transport performance, and the outer loose layer can be used to optimize the ion diffusion path, which can improve various ion energy storage characteristics and electrical conductivity of the graphene / polyaniline composite film. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is the cross-sectional SEM image of the graphene / polyaniline composite film in Example 1;

[0022] Figure 2 It is a schematic diagram of the analysis result of the cross-sectional pore structure image of the graphene / polyaniline composite film in Example 1;

[0023] Figure 3 It is the cross-sectional SEM image of the graphene / polyaniline composite film in Comparative Example 2;

[0024] Figure 4Cross-sectional SEM image of the graphene / polyaniline composite film for Comparative Example 3;

[0025] Figure 5 FT-IR comparison diagrams of graphene / polyaniline composite film, graphene oxide, and reduced graphene oxide during the preparation process of the graphene / polyaniline composite film in Example 1;

[0026] Figure 6 Nyquist plot comparison diagram of the films prepared in Example 1 and Comparative Example 1 as electrode materials in a copper ion hybrid capacitor;

[0027] Figure 7 CV comparison diagram of the films prepared in Example 1 and Comparative Example 1 as electrode materials in a copper ion hybrid capacitor;

[0028] Figure 8 Galvanostatic charge-discharge curve comparison diagram of the films prepared in Example 1 and Comparative Example 1 as electrode materials in a copper ion hybrid capacitor;

[0029] Figure 9 CV comparison diagram of the graphene / polyaniline composite films prepared in Examples 1-3 as electrode materials in a copper ion hybrid capacitor;

[0030] Figure 10 Schematic diagram of the long cycle test results of the graphene / polyaniline composite film prepared in Example 1 as an electrode material in a copper ion hybrid capacitor;

[0031] Figure 11 Electrochemical performance comparison diagram of the graphene / polyaniline composite films prepared in Example 1, Comparative Examples 2-3 as electrode materials in a copper ion hybrid capacitor;

[0032] Figure 12 Specific capacitance of the graphene / polyaniline composite film prepared in Example 1 as an electrode material in a copper ion hybrid capacitor;

[0033] Figure 13 CV curve of the graphene / polyaniline composite film prepared in Example 4 as an electrode material in a copper ion hybrid capacitor;

[0034] Figure 14 CV diagram of the graphene / polyaniline composite film prepared in Example 1 as an electrode material in a zinc-iodine battery;

[0035] Figure 15 Schematic diagram of the long cycle test results of the graphene / polyaniline composite film prepared in Example 1 as an electrode material in a zinc-iodine battery. Detailed implementation manners

[0036] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, without conflict, the embodiments in the present application and the technical features in the embodiments may be combined with each other. It should be pointed out that unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs. As used in the disclosure of the present invention, words such as "including" or "comprising" and the like are intended to mean that the elements or items appearing before the word cover the elements or items listed after the word and their equivalents, without excluding other elements or items.

[0037] On the one hand, the present invention provides a method for preparing a graphene / polyaniline composite film with a gradient structure, comprising the following steps:

[0038] S1: Prepare a coating template, and uniformly coat a graphene oxide dispersion on the coating template to obtain a graphene oxide porous template.

[0039] In a specific embodiment, the coating template is titanium-platinum, graphite sheet or stainless steel. It should be noted that the coating templates in this embodiment are only some commonly used coating templates, and other conductive substrates with good conductivity and capable of electrochemical reduction in the prior art can also be applicable to the present invention. Optionally, a tape with a thickness of 0.1 - 0.3 mm is adhered to a conductive titanium foil to be used as the coating template, so as to control the electrode area.

[0040] In a specific embodiment, the graphene oxide dispersion is uniformly coated on the coating template by a casting method. In this embodiment, the casting method is used for coating, which can enable the graphene oxide dispersion to form a porous gel of graphene oxide gel, providing support for the formation of a porous gradient structure in the subsequent electrochemical reduction process.

[0041] In a specific embodiment, the concentration of the graphene oxide dispersion is 15 - 25 mg / mL.

[0042] S2: Electrochemically reduce the graphene oxide porous template to obtain a reduced graphene oxide porous template.

[0043] In a specific embodiment, during electrochemical reduction, a constant voltage reduction method or a cyclic voltammetry reduction method is adopted. Optionally, the voltage range is -1.6 - 0 V, and the time is 600 s - 3000 s. Optionally, the graphene oxide porous template is used as the working electrode, a platinum sheet is used as the counter electrode, a saturated calomel electrode is used as the reference electrode, and a 0.1 M lithium perchlorate, 0.1 M lithium chloride or 0.1 M sodium sulfate solution is used as the electrolyte. It should be noted that in addition to the counter electrode, reference electrode and electrolyte in this embodiment, other counter electrodes, reference electrodes and electrolytes in the prior art can also be applicable to the present invention.

[0044] In a specific embodiment, when electrochemically reducing the graphene oxide porous template, the graphene oxide porous template used is the undried graphene oxide porous template directly obtained in step S1.

[0045] S3: Conduct electrodeposition of polyaniline on the reduced graphene oxide porous template to obtain a graphene / polyaniline composite film with a gradient structure.

[0046] In a specific embodiment, when conducting electrodeposition of polyaniline, the concentration of polyaniline is 0.01 - 0.1 mol / L.

[0047] In a specific embodiment, when conducting electrodeposition of polyaniline, cyclic voltammetric deposition is used for electrodeposition of polyaniline under a two - electrode system or a three - electrode system. Optionally, the voltage range is 0 - 1 V, the scanning rate is 5 mV / s, and the number of deposition cycles is 5 - 15 cycles. Optionally, the reduced graphene oxide porous template is used as the working electrode, a platinum sheet is used as the counter electrode, a saturated calomel electrode is used as the reference electrode, and a 0.5 M sulfuric acid + 0.1 M aniline mixed solution is used as the electrolyte. It should be noted that in addition to the counter electrode, reference electrode, and electrolyte in this embodiment, other counter electrodes, reference electrodes, and aniline - containing electrolytes in the prior art can also be applicable to the present invention.

[0048] On the other hand, the present invention also provides a graphene / polyaniline composite film with a gradient structure prepared by the preparation method of the graphene / polyaniline composite film with a gradient structure described in any one of the above, and its application as an electrode material in an aqueous hybrid capacitor or a zinc - iodine battery.

[0049] Example 1

[0050] A graphene / polyaniline composite film with a gradient structure is prepared by the following steps:

[0051] (1) Paste two layers of tape with a thickness of 0.1 mm on a titanium foil, and cut a 1×2 cm window as a coating template.

[0052] (2) Uniformly coat a graphene oxide dispersion with a concentration of 20 mg / mL on the cut titanium foil window by a casting method to prepare a graphene oxide porous template with a porous structure, denoted as GO.

[0053] (3) Clamp the coated titanium foil on an electrode clamp as the working electrode, use a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, and conduct electrochemical reduction in a 0.1 M potassium perchlorate solution. The set voltage range is - 1.6 - 0 V, the deposition time is 1800 s, and the number of deposition cycles is 1 cycle to obtain a reduced graphene oxide porous template, denoted as rGO.

[0054] (4) Immerse the coated titanium foil in deionized water to completely detach the reduced graphene oxide porous template from the titanium foil, obtaining a graphene film.

[0055] (5) Conduct electrodeposition of polyaniline through a three-electrode system. Among them, a platinum sheet is used as the counter electrode, the graphene film is used as the working electrode, a saturated calomel electrode is used as the reference electrode, and a mixed solution of 0.5 M sulfuric acid + 0.1 M aniline is used as the electrolyte. Electrochemical deposition is carried out using cyclic voltammetry. The voltage range is 0 - 1 V, the scanning rate is 5 mV / s, and the number of scanning cycles is 10. Obtain a graphene / polyaniline composite film, denoted as rGO-P-10.

[0056] Example 2

[0057] Different from Example 1, the number of scanning cycles in step (5) of this example is 5; the obtained graphene / polyaniline composite film is denoted as rGO-P-5.

[0058] Example 3

[0059] Different from Example 1, the number of scanning cycles in step (5) of this example is 15; the obtained graphene / polyaniline composite film is denoted as rGO-P-15.

[0060] Example 4

[0061] Different from Example 1, the conductive substrate used in step (1) of this example is a graphite sheet, and the concentration of aniline in the electrolyte in step (5) of this example is 0.01 mol / L, and the concentration of sulfuric acid is 0.05 mol / L.

[0062] Comparative Example 1

[0063] Different from Example 1, this comparative example does not include step (5); the obtained graphene film is denoted as rGO-2.

[0064] Comparative Example 2

[0065] Different from Example 1, the reduction method used in step (3) of this comparative example is to reduce in 45% hydroiodic acid at 80 °C for 40 min; other steps are the same as those in Example 1, and the obtained graphene / polyaniline composite film is denoted as GO-HI-P-10.

[0066] Comparative Example 3

[0067] Different from Example 1, the reduction method used in step (3) of this comparative example is to reduce in 0.1 M ascorbic acid at 80 °C for 40 min; other steps are the same as those in Example 1, and the obtained graphene / polyaniline composite film is denoted as GO-VC-P-10.

[0068] Test Example 1

[0069] The morphology of the films of each example and each comparative example was observed by a scanning electron microscope, and some of the results are as Figures 1-4 shown.

[0070] Figure 1 is the SEM image of Example 1. From Figure 1 it can be seen that the cross-sectional image of the graphene / polyaniline composite film prepared in this example shows obvious stratification of the top layer and the bottom layer. Since it is closer to the titanium foil during the casting operation, the upper layer is an obvious dense stacked layer structure, and the lower layer is graphene that was in the upper position during the casting operation, which presents a loose layered stacked structure.

[0071] Figure 2 is the analysis result of the cross-sectional pore structure image of Case 1. From Figure 2 it can be seen that in the cross-sectional direction of the graphene / polyaniline composite film, the change in density shows an obvious gradient change, which is significantly different from the composite film structures obtained by other methods. The formation of this gradient structure benefits from the preferential reduction of the graphene oxide porous template and the metal current collector during the electrochemical reduction process, as well as the density difference caused by the difference in the reduction degree in the cross-sectional direction.

[0072] Figure 3 and Figure 4 are the cross-sectional morphologies of Comparative Example 2 and Comparative Example 3 respectively. From Figure 3 it can be seen that the composite film prepared by reduction with hydroiodic acid is a dense layered structure due to the strong reducibility of hydroiodic acid, which leads to the rapid reduction of graphite oxide gel. From Figure 4 it can be seen that the composite film obtained by reduction with ascorbic acid has very poor structural uniformity, and the distribution of polyaniline is uneven, mainly distributed on the outer surface of the composite film.

[0073] In the present invention, through the combination of electrochemical reduction of graphene oxide porous hydrogel and electrodeposition of polyaniline, a composite electrode material with a gradient structure is constructed. The unique multi-level and multi-porous structure of graphene can effectively relieve the volume expansion and contraction generated by polyaniline during charge and discharge after electrodeposition of polyaniline, thereby improving the structural stability and cycling performance of the material. In addition, the dense graphene stacked layer can be used as a current collector without the need to additionally introduce other current collectors, which can promote electron transfer, and the interlayer structure inside the graphene film can be used to store electrolytes and provide effective electrolyte transfer.

[0074] Test Example 2

[0075] Fourier transform infrared spectroscopy was used to analyze the changes in functional groups among the graphene / polyaniline composite film, reduced graphene oxide, and graphene oxide during the preparation of the graphene / polyaniline composite film of Example 1 of the present invention, and the results are as Figure 5 shown. FromFigure 5 It can be seen that as the reduction progresses, the peaks corresponding to oxygen-containing functional groups such as carboxyl groups and carbonyl groups are greatly inhibited, which also confirms the successful reduction of reduced graphene oxide. At the same time, the C═C aromatic stretching band is still clearly visible, which proves that the structure of sp2 honeycomb graphene remains well unchanged after the reduction process, playing an important role in subsequent inhibiting the shuttle of polyiodides and alleviating the volume expansion and contraction generated by polyaniline during charge and discharge. The graphene / polyaniline composite film prepared in Example 1 has absorption peaks at 750, 1088, 1238 / 1296, 1489, and 1567 cm -1 The absorption peaks at these positions are the out-of-plane bending vibration of C-H, the in-plane bending vibration of C-N / C-H, the stretching vibration of C-N, and the stretching vibration of C═C on the benzene ring and quinone ring, respectively, which confirm the formation of PANI. Secondly, the characteristic peaks at 669 and 1170 cm -1 are from the out-of-plane and in-plane C-H bending vibrations of the aromatic ring, respectively, which confirm the formation of polyaniline.

[0076] Test Example 3

[0077] The films prepared in each example and each comparative example were used as electrode materials to assemble a copper ion hybrid capacitor, and electrochemical impedance spectroscopy tests, cyclic voltammetry tests, and constant current charge and discharge tests were carried out using a three-electrode system on an electrochemical workstation. The test results are as Figures 6-13 shown.

[0078] Figure 6 Figure is a comparative diagram of the results of electrochemical impedance spectroscopy tests of copper ion hybrid capacitors assembled with the films prepared in Example 1 and Comparative Example 1 as electrode materials. From Figure 6 it can be seen that both the equivalent resistance and the charge transfer resistance of Example 1 are significantly better than those of Comparative Example 1.

[0079] Figure 7 Figure is a comparative diagram of cyclic voltammetry test curves of copper ion hybrid capacitors assembled with the films prepared in Example 1 and Comparative Example 1 as electrode materials. From Figure 7 it can be seen that the CV curve of Example 1 has more obvious oxidation-reduction peaks, indicating that Example 1 has a more significant promoting effect on the conversion reaction of iodine.

[0080] Figure 8 Figure is a comparative diagram of constant current charge and discharge test curves of copper ion hybrid capacitors assembled with the films prepared in Example 1 and Comparative Example 1 as electrode materials. From Figure 8 it can be seen that Example 1 has a longer charge and discharge time, indicating that its specific capacity is significantly higher than that of Comparative Example 1, and the equivalent resistance in the charge and discharge curve is also significantly lower than that of Comparative Example 1.

[0081] Figure 9The figure shows the comparison of cyclic voltammetry test curves of copper ion hybrid capacitors assembled with graphene / polyaniline composite films prepared in Example 1, Example 2, and Example 3 as electrode materials. From Figure 8 it can be seen that at a scanning rate of 5 mV s -1 , different redox pairs can be verified between 0.2 - 0.6 V. This obvious redox pair is due to the pseudocapacitance generated by the nitrogen-containing functional groups in the conductive polymer polyaniline deposited on the graphene layer. At a scanning rate of 5 mV s -1 , the capacitance of the copper ion battery does not increase with the increase in the deposition amount of polyaniline. This is because in the case of low deposition amount of the graphene / polyaniline composite film, the graphene layer presents a loose structure, which is beneficial to the diffusion of ions but not conducive to the conduction of electrons. In the case of high deposition amount, the graphene layer presents a dense structure, which is conducive to the conduction of electrons but not conducive to the diffusion of ions.

[0082] Figure 10 The figure shows the results of the long-term cycling performance test of a copper ion hybrid capacitor assembled with the graphene / polyaniline composite film prepared in Example 1 as the electrode material. From Figure 9 it can be seen that rGO-P-10 still maintains a capacity retention rate of 82% after 10,000 cycles, showing good long-term cycling performance.

[0083] Figure 11 The figure shows the results of the electrochemical performance comparison of copper ion hybrid capacitors assembled with the films of Example 1, Comparative Example 2, and Comparative Example 3 as electrode materials. From Figure 10 it can be seen that the graphene / polyaniline composite film with a gradient structure prepared by the present invention exhibits more excellent specific capacitance at different current densities.

[0084] Figure 12 The figure shows the capacity change curve of a copper ion hybrid capacitor assembled with the graphene / polyaniline composite film prepared in Example 1 as the electrode material, and its specific capacitance can reach 121 mAh / g at a current density of 0.1 mA / cm 2 .

[0085] Figure 13 The figure shows the cyclic voltammetry curve of a copper ion hybrid capacitor assembled with the graphene / polyaniline composite film prepared in Example 4 as the electrode material at a scanning rate of 5 mV / s. From Figure 12 it can be seen that on the basis of retaining a certain rectangular characteristic, obvious polyaniline redox peaks appear in the CV curve of this hybrid capacitor.

[0086] Test Example 4

[0087] The graphene / polyaniline composite film prepared in Example 1 was used as the electrode material to assemble a zinc-iodine battery. Cyclic voltammetry and long-term cycling tests were carried out on an electrochemical workstation using a two-electrode system. The test results are as Figures 14-15 shown.

[0088] It can be seen from Figure 14 that at 0.5 mV s -1 , two discharge peaks and two charge peaks can be observed. The two peaks are separated by about 0.3 V. The generation of this group of peaks is due to the adsorption of polyiodide ions by polyaniline, followed by pseudocapacitive energy storage behavior, which improves the electrode capacitance. During the charging process, I - ions migrate from the bulk electrolyte solution, transfer electrons to the film surface and the rGO layer, and spontaneously form PANI adsorbed I3 - at the interface between the GO and PANI layers. The generated PANI adsorbed I3 - ions will then migrate into the bulk rGO layer solution under the concentration gradient and expose other I3 - adsorption sites. During the discharging process, under the concentration gradient, PANI adsorbed I3 - will diffuse from PANI to the interface and accept electrons from the film surface to regenerate I - .

[0089] It can be seen from Figure 15 that at a current of 5 mA, since the rGO-P-10 electrode can effectively adsorb I3 - , the self-discharge of the zinc-iodine battery is inhibited. The electrodeposited polyaniline confines iodine in the framework through the electrostatic embedding of non-protonated amines (-NH-) and protonated imines (-NH + =), and then inhibits its dissolution and shuttle effect, making rGO-P-10 exhibit good cycle stability, and still maintaining a capacity retention rate of 90% after 1000 cycles.

[0090] It should be noted that the above-mentioned examples and test examples are only partial examples and test examples of the present invention. The graphene / polyaniline composite films with gradient structures prepared by the preparation method described in the present invention all have similar properties.

[0091] In summary, the graphene / polyaniline composite film prepared by the present invention has a gradient structure. Using it as the electrode material can improve the electrochemical performance of the battery. Compared with the prior art, the present invention has made significant progress.

[0092] As described above, it is only a representative embodiment of the present invention and does not impose any formal restrictions on the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, makes some modifications or modifications to the above-disclosed technical content, and such embodiments are equivalent embodiments of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation method of a graphene / polyaniline composite film with a gradient structure, characterized in that It includes the following steps: S1: Prepare a coating template, and uniformly coat the graphene oxide dispersion on the coating template to obtain a graphene oxide porous template; S2: Electrochemically reduce the graphene oxide porous template to obtain a reduced graphene oxide porous template; S3: Perform electrodeposition of polyaniline on the reduced graphene oxide porous template to obtain a graphene / polyaniline composite film with a gradient structure.

2. The preparation method of the gradient structure graphene / polyaniline composite film according to claim 1, characterized in that In step S1, the coating template is titanium platinum, a graphite sheet or stainless steel.

3. The preparation method of the graphene / polyaniline composite film with a gradient structure according to claim 1, characterized in that In step S1, the graphene oxide dispersion is uniformly coated on the coating template by a casting method.

4. The preparation method of the gradient-structured graphene / polyaniline composite film according to claim 1, characterized in that, In step S1, the concentration of the graphene oxide dispersion is 15 - 25 mg / mL.

5. The preparation method of the gradient-structured graphene / polyaniline composite film according to claim 1, wherein In step S2, during the electrochemical reduction, a constant voltage reduction method or a cyclic voltammetry reduction method is used.

6. The preparation method of the gradient-structured graphene / polyaniline composite film according to claim 1, characterized in that, In step S3, during the electrodeposition of polyaniline, the concentration of polyaniline is 0.01 - 0.1 mol / L.

7. The preparation method of the graphene / polyaniline composite film with a gradient structure according to claim 1, characterized in that, In step S3, during the electrodeposition of polyaniline, a two - electrode system or a three - electrode system is used.

8. The preparation method of the gradient-structured graphene / polyaniline composite film according to any one of claims 1-7, characterized in that, In step S3, during the electrodeposition of polyaniline, a cyclic voltammetry deposition method is used.

9. A graphene / polyaniline composite film with a gradient structure, characterized in that, It is prepared by using the preparation method of the graphene / polyaniline composite film with a gradient structure described in any one of claims 1 - 8.

10. Application of the graphene / polyaniline composite film with a gradient structure as described in claim 9 as an electrode material in an aqueous hybrid capacitor or a zinc - iodine battery.

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