Planar electrode, preparation method thereof and supercapacitor

Abstract

The invention relates to a planar electrode, a preparation method thereof and a supercapacitor. The preparation method of the planar electrode comprises the following steps: mixing a graphene oxide sheet and a nitrogen source compound in a solvent to obtain an electrode precursor solution; removing a solvent in the electrode precursor solution and depositing an electrode precursor mixture on a substrate to form an electrode precursor film; the thickness of the electrode precursor film is 8 [mu] m-20 [mu] m; performing non-contact heating on the electrode precursor film; in the non-contact heating, the temperature of a heating source is 350-600 DEG C, and the heating time is 4-10 seconds; the vertical distance between the heating surface of the heating source and the electrode precursor film is 0.2 cm to 1 cm. According to the preparation method, the planar electrode preparation time can be remarkably shortened, the production time cost is saved, and the production efficiency of planar electrode products is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and in particular to a planar electrode and a preparation method thereof, and a supercapacitor. Background Art

[0002] Graphene has attracted widespread attention due to its excellent specific surface area, flexibility and conductivity; graphene is also considered to be a very promising supercapacitor electrode material. Among the common preparation techniques, chemical oxidation and reduction of graphite is considered to be a low-cost technology for large-scale production of graphene. Compared with other reduction methods, thermal reduction does not require additives, is simple and efficient to operate, is environmentally friendly and easy to scale up, and is often used in the preparation of graphene electrodes. However, graphene as an electrode material has problems such as weak electrochemical activity and low capacity efficiency. Nitrogen atom doping can effectively enhance the electrochemical properties of graphene electrode materials.

[0003] In recent years, many researchers at home and abroad have made many contributions to the preparation and nitrogen doping of graphene-based electrodes. For example, Kim et al. repeatedly dripped graphene oxide solution on the surface of a fabric substrate, and after drying to form a film, heated the sample at 180°C under argon for 2 hours to obtain a thermally reduced graphene electrode. This method requires a long heat treatment time and cannot achieve efficient and large-scale industrial application of nitrogen doping of graphene electrodes. Summary of the invention

[0004] Based on this, it is necessary to provide a convenient and efficient method for preparing a planar electrode. Furthermore, a planar electrode and a supercapacitor are provided.

[0005] The first aspect of the present application provides a method for preparing a planar electrode, comprising the following steps:

[0006] mixing graphene oxide sheets and a nitrogen source compound in a solvent to obtain an electrode precursor solution;

[0007] Removing the solvent in the electrode precursor solution and depositing the electrode precursor mixture on a substrate to form an electrode precursor film; the thickness of the electrode precursor film is 8 μm to 20 μm;

[0008] The electrode precursor film is non-contact heated; in the non-contact heating, the temperature of the heating source is 350° C. to 600° C., and the heating time is 4s to 10s; the vertical distance between the heating surface of the heating source and the electrode precursor film is 0.2cm to 1cm.

[0009] In the above preparation method, the electrode precursor mixture is first deposited to form an electrode precursor film of a specific thickness, and then the electrode precursor film is heated by a non-contact heating method and the temperature, heating time and vertical distance between the heating source and the electrode precursor film are controlled, so that the overall energy of the oxygen-containing functional groups in the graphene oxide is at a higher level, triggering a violent self-propagating chain deoxidation reaction, thereby restoring the conductivity and becoming reduced graphene oxide; at the same time, the doping material is thermally decomposed at high temperature, and the graphene is nitrogen-doped, thereby preparing a nitrogen-doped planar graphene-based electrode. Further, by a non-contact heating method, the film peeling and rupture problem caused by contact thermal stress caused by direct heating of the heating surface and the film can be avoided, so that the film can maintain good integrity and reduce the time consumption of peeling; under specific temperature conditions, the film of a specific thickness is heated, and the distance between the heating source and the film is controlled, so that the electrode precursor material graphene oxide and the nitrogen source compound on the film can absorb enough heat in a short time to carry out deoxidation and thermal decomposition reactions; at the same time, it can also significantly reduce the preparation time of the planar electrode, save production time cost, and improve the production efficiency of planar electrode products.

[0010] In some embodiments, the step of removing the solvent from the electrode precursor solution and depositing the electrode precursor mixture on the substrate comprises: removing the solvent by evaporation, vacuum filtration or freeze drying.

[0011] In some embodiments, the step of removing the solvent from the electrode precursor solution and depositing the electrode precursor mixture on the substrate includes: forming a patterned electrode precursor film on the substrate by a patterned mold.

[0012] In some embodiments, the graphene oxide sheet has a sheet diameter of 5 μm to 15 μm.

[0013] In some embodiments, the nitrogen source compound is selected from at least one of chitosan, urea, ammonium bicarbonate and dicyandiamide.

[0014] In some embodiments, in the electrode precursor solution, the mass ratio of the graphene oxide to the nitrogen source compound is (2-20):1.

[0015] In some embodiments, in the electrode precursor solution, the concentration of graphene oxide is 2 mg / mL to 10 mg / mL.

[0016] In some embodiments, the heating surface is opposite to the electrode precursor film and is spaced apart from it, and the electrode precursor film is located within the outer contour of the projection of the heating surface on the electrode precursor film.

[0017] A second aspect of the present application provides a planar electrode, which is prepared according to the preparation method described in the first aspect.

[0018] A third aspect of the present application provides a supercapacitor, comprising a first electrode and a second electrode arranged opposite to each other and an electrolyte arranged between the first electrode and the second electrode, at least one of the first electrode and the second electrode comprising the planar electrode described in the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are merely embodiments of the present application, and ordinary technicians in this field can obtain other drawings based on the disclosed drawings without paying any creative work.

[0020] FIG1 is an XRD graph of the raw material graphene oxide (GO) used in Example 1 and the prepared reduced graphene oxide (rGO).

[0021] FIG. 2 is a full XPS spectrum of the planar nitrogen-doped graphene-based electrode (N-rGO) prepared in Example 2 and the reduced graphene oxide (rGO) prepared in Example 1.

[0022] FIG3 is a cross-sectional SEM image of the planar nitrogen-doped graphene-based electrode prepared in Example 2.

[0023] FIG4 is a cyclic voltammetry graph of the supercapacitor prepared in Example 2 at scan rates of 5 mV / s, 10 mV / s, 20 mV / s and 30 mV / s, respectively.

[0024] FIG5 is a graph showing the capacitance retention rate of the supercapacitor prepared in Example 2 at different cycle times at a scan rate of 25 mV / s.

[0025] FIG6 is a cyclic voltammetry (CV) graph of the supercapacitor prepared in Example 2 at scan rates of 5 mV / s and 10 mV / s, respectively.

[0026] FIG7 is a comparison diagram of the electrode surface capacitance and volume capacitance of the supercapacitors prepared in Example 6, Example 7, and Example 8, respectively, obtained through cyclic voltammetry testing at different scan rates.

[0027] FIG8 is a comparison of cyclic voltammetry curves of supercapacitors prepared in Example 2 and Comparative Example 1 at 15 mV / s. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present invention, the present invention is described more comprehensively below. And preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0030] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0031] The weight of the relevant components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also indicate the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the description of the embodiments of the present invention, it is within the scope disclosed in the description of the embodiments of the present invention. Specifically, the weight described in the description of the embodiments of the present invention may be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0032] In one embodiment of the present application, a method for preparing a planar electrode is provided, comprising the following steps S10 to S30:

[0033] S10, mixing the graphene oxide sheet and the nitrogen source compound in a solvent to obtain an electrode precursor solution.

[0034] S20, removing the solvent in the electrode precursor solution and depositing the electrode precursor mixture on the substrate to form an electrode precursor film; the thickness of the electrode precursor film is 8 μm to 20 μm.

[0035] S30, performing non-contact heating on the electrode precursor film; during the non-contact heating, the temperature of the heating source is 350°C~600°C, and the heating time is 4s~10s; the vertical distance between the heating surface of the heating source and the electrode precursor film is 0.2cm~1cm.

[0036] In the above preparation method, the electrode precursor mixture is first deposited to form an electrode precursor film of a specific thickness, and then the electrode precursor film is heated by a non-contact heating method and the temperature, heating time and vertical distance between the heating source and the electrode precursor film are controlled, so that the overall energy of the oxygen-containing functional groups in the graphene oxide is at a higher level, triggering a violent self-propagating chain deoxidation reaction, thereby restoring the conductivity and becoming reduced graphene oxide; at the same time, the doping material is thermally decomposed at high temperature, and the graphene is nitrogen-doped, thereby preparing a nitrogen-doped planar graphene-based electrode. Further, by a non-contact heating method, the film peeling and rupture problem caused by contact thermal stress caused by direct heating of the heating surface and the film can be avoided, so that the film can maintain good integrity and reduce the time consumption of peeling; under specific temperature conditions, the film of a specific thickness is heated, and the distance between the heating source and the film is controlled, so that the electrode precursor material graphene oxide and the nitrogen source compound on the film can absorb enough heat in a short time to carry out deoxidation and thermal decomposition reactions; at the same time, it can also significantly reduce the preparation time of the planar electrode, save production time cost, and improve the production efficiency of planar electrode products.

[0037] As an example, the thickness of the electrode precursor film can be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm. Further, the thickness of the electrode precursor film can be a range value consisting of any two of the above point values ​​as end values.

[0038] As an example, in non-contact heating, the temperature of the heating source may be 350°C, 360°C, 380°C, 400°C, 450°C, 480°C, 500°C, 520°C, 550°C, 580°C or 600°C. Further, the temperature of the heating source may be a range value consisting of any two of the above point values ​​as end values. Preferably, the temperature of the heating source is 400°C to 500°C. By controlling the temperature of the heating source, the instantaneous thermal stress of the entire film can be controlled to prevent cracking.

[0039] As an example, the vertical distance between the heating surface of the heating source and the electrode precursor film can be 0.2 cm, 0.4 cm, 0.5 cm, 0.6 cm, 0.7 cm, 0.8 cm, 0.9 cm or 1 cm. Further, the vertical distance between the heating surface of the heating source and the electrode precursor film can be a range value consisting of any two of the above point values ​​as end values. Preferably, the vertical distance between the heating surface of the heating source and the electrode precursor film is 0.5 cm to 1 cm.

[0040] In some embodiments, the heating source may be a heating module, the heating block has a heating component, the heating component is plate-shaped, and the heating component has a planar heating surface. The heating module used in the present application is a conventional heating module with a planar heating surface.

[0041] In some embodiments, in step S30, the heating surface and the electrode precursor film are opposite and spaced apart, and the electrode precursor film is located within the outer contour of the projection of the heating surface on the electrode precursor film. The electrode precursor film is located within the outer contour of the projection of the heating surface on the electrode precursor film, which means that the area of ​​the heating surface is greater than or equal to the area of ​​the electrode precursor film, so that the graphene oxide and the nitrogen source compound in the electrode precursor film can be fully heated for deoxidation and pyrolysis reaction; and the obtained planar electrode has better uniformity.

[0042] In some embodiments, in step S30, the heating surface is disposed directly above the electrode precursor film; the area of ​​the heating surface is greater than or equal to the area of ​​the electrode precursor film. Preferably, the area of ​​the heating surface is equal to the area of ​​the electrode precursor film.

[0043] In some embodiments, the substrate in step S20 is a flexible substrate. The use of a flexible substrate is beneficial for subsequent assembly into a supercapacitor device and its application in wearable, bendable and other occasions requiring mechanical deformation.

[0044] Further, the flexible substrate is selected from one of fabric cloth, polymer-based film and metal foil.

[0045] Furthermore, the polymer-based film may be a polymer-based microporous filter membrane or a polymer-based non-porous membrane.

[0046] In some embodiments, the pore size in the polymer-based microporous filter membrane is 0.1 μm to 0.5 μm.

[0047] In some embodiments, in step S20, the step of removing the solvent in the electrode precursor solution and depositing the electrode precursor mixture on the substrate includes: removing the solvent by at least one of evaporation, vacuum filtration and freeze drying.

[0048] It is understood that the specific method of removing the solvent is related to the material of the flexible substrate. Specifically, when vacuum filtration is used to remove the solvent, the flexible substrate is selected from fabric or polymer-based microporous filter membrane. When evaporation or freeze drying is used to remove the solvent, the flexible substrate is selected from fabric, polymer-based non-porous membrane or metal foil.

[0049] In some embodiments, the solvent may be an inorganic solvent.

[0050] In some embodiments, the solvent may be water or dilute hydrochloric acid.

[0051] In some embodiments, in step S20, the step of removing the solvent in the electrode precursor solution and depositing the electrode precursor mixture on the substrate includes: forming a patterned electrode precursor film on the substrate through a patterned mold. By forming a patterned electrode precursor film on the substrate through a patterned mold, a patterned planar electrode can be directly obtained, and the steps of further patterning and etching of the planar electrode can be omitted.

[0052] In some embodiments, the diameter of the graphene oxide sheet is 5 μm to 15 μm. As an example, the diameter of the graphene oxide sheet can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm. Further, the diameter of the graphene oxide sheet can be a range value consisting of any two of the above point values ​​as end values.

[0053] In some embodiments, the nitrogen source compound is an organic nitrogen source.

[0054] In some embodiments, the organic nitrogen source is selected from at least one of chitosan, urea, ammonium bicarbonate and dicyandiamide. Preferably, the organic nitrogen source is selected from at least one of chitosan and urea.

[0055] In some embodiments, in the electrode precursor solution, the mass ratio of graphene oxide to the nitrogen source compound is (2-20):1. As an example, in the electrode precursor solution, the mass ratio of graphene oxide to the nitrogen source compound may be 2:1, 3:1, 5:1, 6:1, 8:1, 10:1, 12:1, 15:1, 16:1, 18:1, 19:1 or 20:1. The mass ratio of graphene oxide to the nitrogen source compound may also be other ratios within the above range. Preferably, the mass ratio of graphene oxide to the nitrogen source compound is (4-10):1.

[0056] In some embodiments, in the electrode precursor solution, the concentration of graphene oxide is 2 mg / mL to 10 mg / mL. As an example, in the electrode precursor solution, the concentration of graphene oxide can be 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL or 10 mg / mL. Further, the concentration of graphene oxide can be a range value consisting of any two of the above point values ​​as end values. Controlling the concentration of graphene oxide in the electrode precursor solution can change the content ratio of pyrrolic nitrogen, pyridinic nitrogen and graphite nitrogen after nitrogen doping, thereby controlling the electrochemical properties of the planar electrode.

[0057] In one embodiment of the present application, a planar electrode is provided, and the planar electrode is prepared by the above-mentioned preparation method.

[0058] In some embodiments, the resistance of the planar electrode is 44.56Ω·sq -1 ~106.12Ω·sq -1 .

[0059] In some embodiments, the thickness of the planar electrode is 8μm~35μm. After the electrode precursor film is heat treated, the oxygen in the graphene oxide is detached, resulting in the fluffy layer, so that the thickness of the planar electrode is thicker than the thickness of the electrode precursor film. As an example, the thickness of the planar electrode can be 8μm, 9μm, 10μm, 11μm, 15μm, 16μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 34μm or 35μm. The thickness of the planar electrode can be a range value consisting of any two of the above point values ​​as end values. Preferably, the thickness of the planar electrode is 8μm~22μm.

[0060] Another embodiment of the present application provides a supercapacitor, including a first electrode and a second electrode arranged opposite to each other, and also including an electrolyte arranged between the first electrode and the second electrode; at least one of the first electrode and the second electrode includes the above-mentioned planar electrode.

[0061] In some embodiments, the first electrode and the second electrode both include the planar electrode.

[0062] In some embodiments, the electrolyte is a gel electrolyte.

[0063] In some embodiments, the electrolyte comprises KOH and H 3 PO 4 At least one of them is with polyvinyl alcohol (PVA).

[0064] In some embodiments, the supercapacitor further comprises current collectors disposed on the first electrode and the second electrode respectively away from the electrolyte. That is, a current collector is disposed on the first electrode away from the electrolyte; and a current collector is also disposed on the second electrode away from the electrolyte.

[0065] In some embodiments, the current collector is made of copper foil.

[0066] In order to make the purpose, technical solutions and advantages of the present invention more concise and clear, the present invention is described with the following specific embodiments, but the present invention is by no means limited to these embodiments. The embodiments described below are only preferred embodiments of the present invention, which can be used to describe the present invention and cannot be understood as limiting the scope of the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0067] In order to better illustrate the present invention, the present invention is further described below in conjunction with the embodiments. The following are specific embodiments.

[0068] Example 1

[0069] In this embodiment 1, reduced graphene oxide is prepared, and the specific steps are as follows:

[0070] (1) Preparing graphene oxide solution: Add graphene oxide sheets with a thickness of 15 μm into water to prepare a graphene oxide solution with a concentration of 2 mg / mL.

[0071] (2) Preparation of graphene oxide membrane: Spread 30×30 mm cotton cloth as filter paper on the sand core filtration device; clamp a 16 mm diameter PTFE cylindrical mold on the cotton cloth, use a syringe to extract 1 mL of graphene oxide solution and inject it from the top of the cylindrical mold. After the liquid surface is evenly leveled, turn on the filtration pump and filter; after the solvent is completely filtered, remove the sample from the filter paper and dry it in a drying oven at 60°C for 30 min to obtain a graphene oxide membrane with a thickness of 6.62 mm.

[0072] (3) Using a copper block heating device in a ceramic core, the graphene oxide film was heated and reduced in an atmospheric environment: the graphene oxide film was placed on a 6 mm thick glass plate. After the heating module was heated to 450 °C, the heating module was moved above the graphene oxide film and the distance between the graphene oxide film and the heating module was adjusted to 0.5 cm. After maintaining the distance for 6 s, the heating module was removed and the film was removed to obtain reduced graphene oxide.

[0073] Figure 1 shows the XRD graph of the raw material graphene oxide (GO) used in Example 1 and the XRD graph of the reduced graphene oxide (rGO) prepared in Example 1. It can be seen from Figure 1 that the graphene oxide has a strong diffraction characteristic peak near 2θ of about 12.3°; after non-contact heat treatment, the intensity of the characteristic peak of graphene oxide decreases significantly and the position shifts to the right, indicating that the graphene oxide has been reduced to form reduced graphene oxide.

[0074] Example 2

[0075] This embodiment provides a nitrogen-doped graphene-based planar electrode, and uses it to assemble a supercapacitor. The specific operation steps are as follows:

[0076] (1) Preparing graphene oxide solution: Add graphene oxide sheets with a thickness of 15 μm into water to prepare a graphene oxide solution with a concentration of 2 mg / mL.

[0077] (2) Preparing a precursor solution: Add chitosan powder to a 2 mg / mL graphene oxide solution, mix, and stir in a 50°C water bath to evenly disperse the mixture, thereby forming an electrode material precursor solution having a mass ratio of graphene oxide to chitosan powder of 8:1.

[0078] (3) Preparation of graphene oxide / chitosan film: Lay 30×30 mm cotton cloth as filter paper on the sand core filtration device; clamp a 16 mm diameter PTFE cylindrical mold on the cotton cloth, use a syringe to extract 1 mL of the precursor solution and inject it from the top of the cylindrical mold. After the liquid surface is evenly leveled, turn on the filtration pump to filter; after the solvent is completely filtered, remove the sample from the filter paper and dry it in a drying oven at 60°C for 30 min to obtain a graphene oxide / chitosan film (i.e., electrode precursor film) with a thickness of 9.20 μm.

[0079] (4) The graphene oxide / chitosan film was heated and reduced using a copper block heating device in a ceramic core: the graphene oxide / chitosan film was placed on a 6 mm thick glass plate. After the heating module was heated to 450 °C, the heating module was moved above the graphene oxide film and the distance between the graphene oxide film and the heating module was adjusted to 0.5 cm. After keeping the heating module for 6 s, the film was removed to obtain a nitrogen-doped planar graphene-based electrode.

[0080] (5) Preparation of H 3 PO 4 / PVA gel electrolyte: Dissolve PVA in deionized water at 85°C, add H 3 PO 4 , stir evenly and let stand to cool to obtain H 3 PO 4 / PVA gel electrolyte.

[0081] (6) Preparation of capacitor: The gel electrolyte obtained in step (5) is used as the middle interlayer, the nitrogen-doped planar graphene-based electrodes are used as symmetrical positive and negative electrodes, copper foil is pasted on the outside of the two electrodes as a conductive current collector, and a supercapacitor is obtained after packaging.

[0082] Example 3

[0083] This embodiment provides a nitrogen-doped graphene-based planar electrode, and uses it to assemble a supercapacitor. The specific operation steps are as follows:

[0084] (1) Preparing a graphene oxide solution: Add graphene oxide sheets with a thickness of 15 μm into water to prepare a graphene oxide solution with a concentration of 2 mg / mL.

[0085] (2) Preparing a precursor solution: Add urea powder to a 5 mg / mL graphene oxide solution, mix the mixture, and evenly disperse the mixture by magnetic stirring to form an electrode material precursor solution with a mass ratio of graphene oxide to urea powder of 2:1.

[0086] (3) Preparation of graphene oxide / urea film: Using polyimide (PI) as the matrix, a PTFE mold with a cross-finger pattern was clamped on top of the PI. 1 mL of the precursor solution was drawn using a syringe and injected from the top of the mold. The whole was placed in an oven at 80 °C and evaporated for 2 h to obtain a graphene oxide-urea film with a thickness of 18.5 μm.

[0087] (4) Use a ceramic core copper block heating device to heat and reduce the graphene oxide / urea film: place the graphene oxide / urea film on a 6 mm thick glass plate. After the heating module is heated to 400 °C, move the heating module above the graphene oxide film and adjust the distance between the graphene oxide film and the heating module to 1 cm. After keeping for 10 seconds, remove the heating module and remove the film to obtain a nitrogen-doped planar graphene-based electrode.

[0088] (5) Preparation of H 3 PO 4 / PVA gel electrolyte: Dissolve PVA in deionized water at 85°C, add H 3 PO 4 , stir evenly and let stand to cool to obtain H 3 PO 4 / PVA gel electrolyte.

[0089] (6) Preparation of capacitor: The gel electrolyte obtained in step (5) is used as the middle interlayer, the nitrogen-doped planar graphene-based electrodes are used as symmetrical positive and negative electrodes, copper foil is pasted on the outside of the two electrodes as a conductive current collector, and a supercapacitor is obtained after packaging.

[0090] Example 4

[0091] The preparation method of this embodiment is basically the same as that of Embodiment 2, except that the diameter of the graphene oxide sheets used is different. The diameter of the graphene oxide sheets used in this embodiment is 5 μm.

[0092] The other preparation steps and process conditions are basically the same as those in Example 2.

[0093] Example 5

[0094] The preparation method of this embodiment is basically the same as that of Embodiment 2, except that the diameter of the graphene oxide sheets used is different. The diameter of the graphene oxide sheets used in this embodiment is 10 μm.

[0095] The other preparation steps and process conditions are basically the same as those in Example 2.

[0096] Example 6

[0097] The preparation method of this embodiment is basically the same as that of Embodiment 2, except that the mass ratio of graphene oxide to chitosan powder in the electrode material precursor solution is different. The mass ratio of graphene oxide to chitosan powder in the electrode material precursor solution prepared in this embodiment is 5:1.

[0098] The other preparation steps and process conditions are basically the same as those in Example 2.

[0099] Example 7

[0100] The preparation method of this embodiment is basically the same as that of embodiment 6, the only difference being that the nitrogen source material is different. The nitrogen source used in this embodiment is urea.

[0101] The other preparation steps and process conditions are basically the same as those in Example 6.

[0102] Example 8

[0103] The preparation method of this embodiment is basically the same as that of embodiment 6, the only difference being that the nitrogen source material is different, ammonium bicarbonate is used in this embodiment.

[0104] The other preparation steps and process conditions are basically the same as those in Example 6.

[0105] Comparative Example 1

[0106] The preparation method of this comparative example is basically the same as that of Example 2, except that the precursor solution is different. No nitrogen source compound is added to the precursor solution of this comparative example, and only 2 mg / mL graphene oxide solution is used.

[0107] The other preparation steps and process conditions are basically the same as those in Example 2.

[0108] Comparative Example 2

[0109] The preparation method of this comparative example is basically the same as that of Example 2, except that the heating method used is different. In this example, the electrode precursor film is directly contacted with the heating module, and the heating block is removed after heating for 10 seconds. When the heating block is separated from the film, the film is cracked when it is peeled off due to contact thermal stress, thus being incomplete.

[0110] Comparative Example 3

[0111] The preparation method of this comparative example is basically the same as that of Example 2, except that the thickness of the graphene oxide / chitosan film formed in step (3) is different. The thickness of the graphene oxide / chitosan film obtained in this comparative example is 30 μm.

[0112] The performance test results of each embodiment and comparative example are shown in Table 1.

[0113] Table 1

[0114]

[0115] Note: In Table 1, the performance data of the area capacitance, volume capacitance and capacitance retention rate of the supercapacitor after 2000 cycles are all performance data at a scan rate of 25mV / s.

[0116] Figure 2 is a full XPS spectrum of the planar nitrogen-doped graphene-based electrode (N-rGO) prepared in Example 2 and the reduced graphene oxide (rGO) prepared in Example 1. As can be seen from Figure 2, a diffraction peak of the N element appears in the planar nitrogen-doped graphene-based electrode (N-rGO), and the N element is successfully doped into the planar nitrogen-doped graphene-based electrode (N-rGO).

[0117] Figure 3 is a cross-sectional view of the planar nitrogen-doped graphene-based electrode prepared in Example 2. From Figure 3, it can be seen that the planar nitrogen-doped graphene-based electrode is layered, and the thickness of the planar nitrogen-doped graphene-based electrode is about 12 μm.

[0118] Figure 4 is a cyclic voltammetry curve of the supercapacitor prepared in Example 2 at scan rates of 5mV / s, 10mV / s, 20mV / s and 30mV / s, respectively. It can be seen from Figure 4 that at a lower voltage scan rate (5 mV / s, 10 mV / s), the cyclic voltammetry curve shows a slight redox peak, considering that the electrode used in this embodiment is a nitrogen-doped graphene-based electrode. Therefore, the capacity of the supercapacitor comes from the double-layer capacitance of reduced graphene oxide and the pseudocapacitance of nitrogen doping. It can be calculated that the supercapacitor has 28.75mF / cm at a scan rate of 5 mV / s. 2 The specific area capacity and 25.93F / cm 3 Specific volume capacity.

[0119] Figure 5 is a graph showing the capacitance retention rate of the supercapacitor prepared in Example 2 at different cycle times at a scan rate of 25 mV / s. It can be seen from the figure that the capacitance of the supercapacitor prepared in Example 2 is retained at about 85% after 20,000 cycles.

[0120] Figure 6 is a cyclic voltammetry (CV) graph of the supercapacitor prepared in Example 2 at scan rates of 5 mV / s and 10 mV / s. It can be seen from the figure that under the action of a lower voltage scan rate (5 mV / s, 10 mV / s) and an alkaline electrolyte, the cyclic voltammetry curve shows an obvious redox peak.

[0121] Figure 7 is a comparison of the electrode surface capacitance and volume capacitance of the supercapacitors prepared in Example 6, Example 7, and Example 8 at different scan rates obtained by cyclic voltammetry. It can be seen from the figure that at a lower scan rate, the supercapacitors prepared in Examples 6 to 8 all have higher area capacitance and volume capacitance.

[0122] The planar electrode prepared in Comparative Example 1 was not doped with an organic nitrogen source. Figure 8 is a comparison of the cyclic voltammetry curves of the supercapacitors prepared in Example 2 and Comparative Example 1 at a scan rate of 15 mV / s. It can be seen from the figure that the performance of the thin film electrode has been significantly improved after nitrogen atom doping modification. Combined with Table 1, the area capacitance of the supercapacitor prepared in Comparative Example 1 at a scan rate of 25 mV / s is 10.13 mF / cm 2 , volume capacitance is 9.51F / cm 3 It can be seen that when the planar electrode prepared in Comparative Example 1 is not doped with nitrogen, the performance of the supercapacitor prepared therefrom is inferior to that of the supercapacitor prepared in Example 2.

[0123] In the planar electrode prepared in Comparative Example 3, the thickness of the electrode precursor film formed on the substrate reaches 30 μm. Too high a thickness will result in the layer away from the heating block not being reduced, making the resistance to electrons in the longitudinal transmission too large, resulting in an increase in the film impedance and affecting the capacitance of the planar electrode.

[0124] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0125] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A method for preparing a planar electrode, characterized in that: The steps include: mixing graphene oxide sheets and a nitrogen source compound in a solvent to obtain an electrode precursor solution; Removing the solvent from the electrode precursor solution and depositing the electrode precursor mixture on a substrate to form an electrode precursor film; The thickness of the electrode precursor film is 8 μm to 20 μm; The electrode precursor film is subjected to non-contact heating; in the non-contact heating, the temperature of the heating source is 350° C. to 600° C., and the heating time is 4s to 10s; and the vertical distance between the heating surface of the heating source and the electrode precursor film is 0.2cm to 1cm.

2. The preparation method according to claim 1, characterized in that The step of removing the solvent from the electrode precursor solution and depositing the electrode precursor mixture on the substrate comprises: removing the solvent by evaporation, vacuum filtration or freeze drying.

3. The preparation method according to claim 1, characterized in that: The step of removing the solvent in the electrode precursor solution and depositing the electrode precursor mixture on the substrate includes: forming a patterned electrode precursor film on the substrate by a patterned mold.

4. The preparation method according to any one of claims 1 to 3, characterized in that The diameter of the graphene oxide sheet is 5 μm to 15 μm.

5. The preparation method according to any one of claims 1 to 3, characterized in that: The nitrogen source compound is selected from at least one of chitosan, urea, ammonium bicarbonate and dicyandiamide.

6. The preparation method according to any one of claims 1 to 3, characterized in that: In the electrode precursor solution, the mass ratio of the graphene oxide to the nitrogen source compound is (2-20):

1.

7. The preparation method according to any one of claims 1 to 3, characterized in that: In the electrode precursor solution, the concentration of graphene oxide is 2 mg / mL to 10 mg / mL.

8. The preparation method according to any one of claims 1 to 3, characterized in that: The heating surface is opposite to the electrode precursor film and is spaced apart from it. The electrode precursor film is located within the outer contour of the projection of the heating surface on the electrode precursor film.

9. A planar electrode, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 8.

10. A supercapacitor, characterized in that: The device comprises a first electrode and a second electrode which are arranged opposite to each other and an electrolyte which is arranged between the first electrode and the second electrode, wherein at least one of the first electrode and the second electrode comprises the planar electrode according to claim 9.

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