Planar electrode, preparation method thereof, and supercapacitor

Abstract

This application relates to a planar electrode, its fabrication method, and a supercapacitor. The planar electrode fabrication method includes the following steps: 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 onto a substrate to form an electrode precursor film; the thickness of the electrode precursor film is 8 μm to 20 μm; and subjecting the electrode precursor film to non-contact heating; in the non-contact heating, the heating source temperature is 350℃ to 600℃, and the heating time is 4 s to 10 s; the vertical distance between the heating surface of the heating source and the electrode precursor film is 0.2 cm to 1 cm. This fabrication method can significantly reduce the fabrication time of planar electrodes, save production time and costs, and improve the production efficiency of planar electrode products.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and in particular to a planar electrode, its preparation method, and a supercapacitor. Background Technology

[0002] Graphene has attracted widespread attention due to its excellent specific surface area, flexibility, and conductivity; it is also considered a promising electrode material for supercapacitors. Among common preparation techniques, the chemical oxidation followed by reduction of graphite is considered a low-cost technology for large-scale production of graphene. Thermal reduction, compared to other reduction methods, requires no additives, is simple and efficient, environmentally friendly, and easy to scale up, and is often used in the preparation of graphene electrodes. However, graphene as an electrode material suffers from weak electrochemical activity and low capacity efficiency. Nitrogen doping can effectively enhance the electrochemical performance of graphene electrode materials.

[0003] In recent years, many researchers both domestically and internationally have made significant contributions to the preparation and nitrogen doping of graphene-based electrodes. For example, Kim et al. repeatedly drop-coated graphene oxide solution onto the surface of a fabric substrate. After drying to form a film, the sample was heated under argon at 180°C for 2 hours to obtain a thermally reduced graphene electrode. However, this method requires a long heat treatment time, making it unsuitable for the efficient and large-scale industrial application of nitrogen-doped graphene electrodes. Summary of the Invention

[0004] Therefore, it is necessary to provide a convenient and efficient method for fabricating planar electrodes. Furthermore, a planar electrode and a supercapacitor are provided.

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

[0006] Graphene oxide sheets and nitrogen source compounds are mixed in a solvent to obtain an electrode precursor solution.

[0007] The solvent in the electrode precursor solution is removed and the electrode precursor mixture is deposited on the 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 heated in a non-contact manner; in the non-contact heating, the temperature of the heating source is 350℃~600℃, 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.

[0009] In the above preparation method, an electrode precursor mixture is first deposited to form an electrode precursor film of a specific thickness. Then, the electrode precursor film is heated using a non-contact heating method, with control over the temperature, heating time, and perpendicular distance between the heating source and the electrode precursor film. This heats the oxygen-containing functional groups in the graphene oxide to a high energy level, triggering a vigorous self-propagating chain deoxidation reaction, thereby restoring conductivity and transforming it into reduced graphene oxide. Simultaneously, the dopant undergoes high-temperature thermal decomposition, resulting in nitrogen doping of the graphene, thus preparing a nitrogen-doped planar graphene-based electrode. Furthermore, the non-contact heating method avoids the problem of film peeling and cracking caused by direct heating between the heating surface and the film, thus maintaining the integrity of the film and reducing peeling time. Heating a film of a specific thickness under specific temperature conditions and controlling the distance between the heating source and the film allows the electrode precursor material, graphene oxide, and the nitrogen source compound on the film to absorb sufficient heat in a short time for deoxidation and thermal decomposition reactions. This also significantly reduces the preparation time of the planar electrode, saves production time and costs, and improves 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 onto the substrate includes removing the solvent by means of 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 onto a substrate includes: forming a patterned electrode precursor film on the substrate using a patterned mold.

[0012] In some embodiments, the diameter of the graphene oxide sheet is 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, the mass ratio of the graphene oxide to the nitrogen source compound in the electrode precursor solution is (2~20):1.

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

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

[0017] The second aspect of this application provides a planar electrode prepared according to the preparation method described in the first aspect.

[0018] A third aspect of this application provides a supercapacitor, including a first electrode and a second electrode disposed opposite to each other, and an electrolyte disposed between the first electrode and the second electrode, wherein at least one of the first electrode and the second electrode includes the planar electrode described in the second aspect. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the disclosed drawings without creative effort.

[0020] Figure 1 The images show the XRD patterns of graphene oxide (GO) used in Example 1 and the prepared reduced graphene oxide (rGO).

[0021] Figure 2 XPS full spectra 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] Figure 3 The image shows a cross-sectional SEM image of the planar nitrogen-doped graphene-based electrode prepared in Example 2.

[0023] Figure 4 Cyclic voltammetry curves of the supercapacitor prepared in Example 2 at scan rates of 5mV / s, 10mV / s, 20mV / s, and 30mV / s.

[0024] Figure 5 The capacitance retention curves of the supercapacitor prepared in Example 2 at different cycle numbers at a scan rate of 25 mV / s.

[0025] Figure 6 Cyclic voltammetry (CV) results of the supercapacitor prepared in Example 2 at scan rates of 5 mV / s and 10 mV / s.

[0026] Figure 7 Comparison of electrode surface capacitance and volumetric capacitance obtained by cyclic voltammetry tests at different scan rates for the supercapacitors prepared in Examples 6, 7, and 8.

[0027] Figure 8 The graph shows a comparison of the cyclic voltammetry curves of the supercapacitors prepared in Example 2 and Comparative Example 1 at 15 mV / s. Detailed Implementation

[0028] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. 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 these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

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

[0031] The weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the weights mentioned in the embodiments of this invention can be well-known units of mass in the chemical industry, such as μg, mg, g, and kg.

[0032] One embodiment of this application provides a method for preparing a planar electrode, comprising the following steps S10-S30:

[0033] S10. Mix graphene oxide sheets and nitrogen source compounds in a solvent to obtain an electrode precursor solution.

[0034] S20. Remove the solvent from the electrode precursor solution and deposit the electrode precursor mixture onto the substrate to form an electrode precursor film; the thickness of the electrode precursor film is 8μm~20μm.

[0035] S30. Non-contact heating of the electrode precursor film; in non-contact heating, the temperature of the heating source is 350℃~600℃, 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, an electrode precursor mixture is first deposited to form an electrode precursor film of a specific thickness. Then, the electrode precursor film is heated using a non-contact heating method, with control over the temperature, heating time, and perpendicular distance between the heating source and the electrode precursor film. This heats the oxygen-containing functional groups in the graphene oxide to a high energy level, triggering a vigorous self-propagating chain deoxidation reaction, thereby restoring conductivity and transforming it into reduced graphene oxide. Simultaneously, the dopant undergoes high-temperature thermal decomposition, resulting in nitrogen doping of the graphene, thus preparing a nitrogen-doped planar graphene-based electrode. Furthermore, the non-contact heating method avoids the problem of film peeling and cracking caused by direct heating between the heating surface and the film, thus maintaining the integrity of the film and reducing peeling time. Heating a film of a specific thickness under specific temperature conditions and controlling the distance between the heating source and the film allows the electrode precursor material, graphene oxide, and the nitrogen source compound on the film to absorb sufficient heat in a short time for deoxidation and thermal decomposition reactions. This also significantly reduces the preparation time of the planar electrode, saves production time and costs, and improves 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. Furthermore, the thickness of the electrode precursor film can be a range of values ​​defined by any two of the above point values ​​as endpoints.

[0038] As an example, in non-contact heating, the temperature of the heating source can 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 can be a range defined by any two of the above values ​​as endpoints. 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, preventing rupture.

[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 of values ​​defined by any two of the above points as endpoints. 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 can be a heating module, and the heating block has a heating element, which is plate-shaped and has a planar heating surface. The heating module used in this 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 positioned opposite each other and spaced apart, with the electrode precursor film located within the projected outer contour of the heating surface on the electrode precursor film. The fact that the electrode precursor film is located within the projected outer contour of the heating surface on the electrode precursor film indicates that the area of ​​the heating surface is greater than or equal to the area of ​​the electrode precursor film. This allows for sufficient heating of the graphene oxide and nitrogen source compounds in the electrode precursor film to undergo deoxidation and pyrolysis reactions, and also results in a more uniform planar electrode.

[0042] In some embodiments, in step S30, the heating surface is positioned 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. Using a flexible substrate is advantageous for subsequent applications in wearable, bending, and other situations requiring mechanical deformation after the supercapacitor device is assembled.

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

[0045] Furthermore, the polymer-based membrane can be a polymer-based microporous filter membrane or a polymer-based nonporous membrane.

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

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

[0048] It is understandable that the specific method of solvent removal is related to the material of the flexible substrate. Specifically, when removing solvent by vacuum filtration, the flexible substrate is selected from fabric or polymer-based microporous membranes. When removing solvent by evaporation or freeze-drying, the flexible substrate is selected from fabric, polymer-based nonporous membranes, 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, step S20, the step of removing the solvent from the electrode precursor solution and depositing the electrode precursor mixture onto the substrate, includes: forming a patterned electrode precursor film on the substrate using a patterning mold. Forming a patterned electrode precursor film on the substrate using a patterning mold directly yields a patterned planar electrode, eliminating the need for further patterning and etching steps on the planar electrode.

[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 defined by any two of the above values ​​as endpoints.

[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, the mass ratio of graphene oxide to nitrogen source compound in the electrode precursor solution is (2~20):1. As an example, the mass ratio of graphene oxide to nitrogen source compound in the electrode precursor solution can 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 nitrogen source compound can also be other ratios within the above range. Preferably, the mass ratio of graphene oxide to nitrogen source compound is (4~10):1.

[0056] In some embodiments, the concentration of graphene oxide in the electrode precursor solution is 2 mg / mL to 10 mg / mL. As an example, the concentration of graphene oxide in the electrode precursor solution 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 defined by any two of the above values ​​as endpoints. By controlling the concentration of graphene oxide in the electrode precursor solution, the proportions of pyrrole nitrogen, pyridine nitrogen, and graphitic nitrogen after nitrogen doping can be changed, thereby controlling the electrochemical performance of the planar electrode.

[0057] One embodiment of this application provides a planar electrode, which is prepared by the above-described preparation method.

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

[0059] In some embodiments, the thickness of the planar electrode is 8 μm to 35 μm. After heat treatment, oxygen in the graphene oxide is released, causing the sheets to become fluffy, resulting in the planar electrode being thicker than the electrode precursor film. For example, the thickness of the planar electrode can be 8 μm, 9 μm, 10 μm, 11 μm, 15 μm, 16 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 34 μm, or 35 μm. The thickness of the planar electrode can be a range defined by any two of the above values ​​as endpoints. Preferably, the thickness of the planar electrode is 8 μm to 22 μm.

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

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

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

[0063] In some embodiments, the electrolyte comprises at least one of KOH and H3PO4 with polyvinyl alcohol (PVA).

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

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

[0066] To make the objectives, technical solutions, and advantages of this invention clearer and more concise, the invention is described using the following specific embodiments, but the invention is by no means limited to these embodiments. The embodiments described below are merely preferred embodiments of the invention and can be used to describe the invention, but should not be construed as limiting the scope of the invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the protection scope of this invention.

[0067] To better illustrate the present invention, the following embodiments are provided for further explanation. The specific embodiments are as follows.

[0068] Example 1

[0069] The specific steps for preparing reduced graphene oxide in Example 1 are as follows:

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

[0071] (2) Preparation of graphene oxide membrane: A 30×30 mm cotton cloth was laid flat on the sand core filtration device as filter paper; a 16 mm diameter PTFE cylindrical mold was clamped above the cotton cloth, and 1 mL of graphene oxide solution was injected from the top of the cylindrical mold using a syringe. After the liquid surface was uniform and flat, the filtration pump was turned on for filtration; after the solvent was completely filtered, the sample on the filter paper was removed and placed in a drying oven at 60℃ for 30 min to obtain a graphene oxide membrane with a thickness of 6.62 mm.

[0072] (3) Using a ceramic core heating copper block device, the graphene oxide film is heated and reduced in the atmosphere: The graphene oxide film is placed on a glass plate with a thickness of 6 mm. After the heating module heats up to 450°C, the heating module is moved above the graphene oxide film and the distance between the graphene oxide film and the heating module is adjusted to 0.5 cm. After holding for 6 s, the heating module is removed and the film is taken off to obtain reduced graphene oxide.

[0073] Figure 1 The images show the XRD patterns of graphene oxide (GO) used in Example 1 and the XRD patterns of reduced graphene oxide (rGO) prepared in Example 1. From... Figure 1 It can be seen that graphene oxide exhibits a strong diffraction characteristic peak near 2θ of approximately 12.3°. After non-contact heat treatment, the intensity of the graphene oxide characteristic peak decreases significantly and its 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 applies it to the assembly of a supercapacitor. The specific operation steps are as follows:

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

[0077] (2) Preparation of precursor solution: Chitosan powder was added to a 2 mg / mL graphene oxide solution and mixed and stirred evenly in a 50°C water bath to form an electrode material precursor solution with a mass ratio of graphene oxide to chitosan powder of 8:1.

[0078] (3) Preparation of graphene oxide / chitosan film: A 30×30 mm cotton cloth was laid flat on the sand core filtration device as filter paper; a 16 mm diameter PTFE cylindrical mold was clamped above the cotton cloth, and 1 mL of precursor solution was injected from the top of the cylindrical mold using a syringe. After the liquid surface was uniform and flat, the filtration pump was turned on for filtration; after the solvent was completely filtered, the sample on the filter paper was removed and placed in a drying oven at 60℃ for 30 min to obtain a graphene oxide / chitosan film with a thickness of 9.20 μm (i.e., electrode precursor film).

[0079] (4) The graphene oxide / chitosan film was heated and reduced using a ceramic core heating copper block device: The graphene oxide / chitosan film was placed on a glass plate with a thickness of 6 mm. 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 holding for 6 seconds, the heating module was removed and the film was taken off to obtain a nitrogen-doped planar graphene-based electrode.

[0080] (5) Preparation of H3PO4 / PVA gel electrolyte: PVA is dissolved in deionized water at 85℃. After complete dissolution, H3PO4 is added, stirred evenly, and then allowed to stand and cool to obtain H3PO4 / PVA gel electrolyte.

[0081] (6) Preparation of capacitor: The gel electrolyte obtained in step (5) is used as the middle layer, and 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 after encapsulation, a supercapacitor is obtained.

[0082] Example 3

[0083] This embodiment provides a nitrogen-doped graphene-based planar electrode and applies it to the assembly of a supercapacitor. The specific operation steps are as follows:

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

[0085] (2) Preparation of precursor solution: Add urea powder to 5 mg / mL graphene oxide solution and mix, and then stir magnetically to disperse evenly 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 substrate, clamp a PTFE mold with interdigitated pattern on top of the PI, use a syringe to draw 1 mL of precursor solution and inject it from the top of the mold, and put the whole thing into an 80℃ oven and evaporate for 2 h to obtain a graphene oxide-urea film with a thickness of 18.5 μm.

[0087] (4) The graphene oxide / urea film was heated and reduced by using a ceramic core heating copper block device: The graphene oxide / urea film was placed on a glass plate with a thickness of 6 mm. After the heating module was heated to 400°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 1 cm. After holding for 10 seconds, the heating module was removed and the film was taken off to obtain a nitrogen-doped planar graphene-based electrode.

[0088] (5) Preparation of H3PO4 / PVA gel electrolyte: PVA is dissolved in deionized water at 85℃. After complete dissolution, H3PO4 is added, stirred evenly, and then allowed to stand and cool to obtain H3PO4 / PVA gel electrolyte.

[0089] (6) Preparation of capacitor: The gel electrolyte obtained in step (5) is used as the middle layer, and 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 after encapsulation, a supercapacitor is obtained.

[0090] Example 4

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

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

[0093] Example 5

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

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

[0096] Example 6

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

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

[0099] Example 7

[0100] The preparation method in this embodiment is basically the same as that in Example 6, except that the nitrogen source material is different. In this embodiment, the nitrogen source used is urea.

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

[0102] Example 8

[0103] The preparation method in this embodiment is basically the same as that in Example 6, except that the nitrogen source material is different; ammonium bicarbonate is used in this embodiment.

[0104] Other preparation steps and process conditions are basically the same as 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 was added to the precursor solution of this comparative example, and it was only a 2 mg / mL graphene oxide solution.

[0107] Other preparation steps and process conditions are basically the same as 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 is different. In this example, the electrode precursor film is directly contacted with the heating module, and after heating for 10 seconds, the heating block is removed. When the heating block is separated from the film, the film is peeled off due to contact thermal stress and thus becomes 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 supercapacitor's areal capacitance, volume capacitance, and capacitance retention after 2000 cycles are all performance data at a scan rate of 25mV / s.

[0116] Figure 2 XPS full spectra of the planar nitrogen-doped graphene-based electrode (N-rGO) prepared in Example 2 and the reduced graphene oxide (rGO) prepared in Example 1. Figure 2 As can be seen, diffraction peaks of N element appeared in the planar nitrogen-doped graphene-based electrode (N-rGO), indicating that N element was successfully doped into the planar nitrogen-doped graphene-based electrode (N-rGO).

[0117] Figure 3 This 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 Cyclic voltammetry curves 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. From... Figure 4 As can be observed, at lower voltage scan rates (5 mV / s, 10 mV / s), the cyclic voltammetry curves show slight redox peaks, considering that the electrode used in this embodiment is a nitrogen-doped graphene-based electrode. Therefore, the capacitance of this supercapacitor originates from the double-layer capacitance of the reduced graphene oxide and the pseudocapacitance of the nitrogen doping. Calculations show that this supercapacitor has 28.75 mF / cm² at a scan rate of 5 mV / s. 2 Specific area capacity and 25.93F / cm² 3 Specific volume capacity.

[0119] Figure 5 The graph shows the capacitance retention rate of the supercapacitor prepared in Example 2 at different cycle numbers at a scan rate of 25 mV / s. As can be seen from the graph, the supercapacitor prepared in Example 2 retains approximately 85% of its capacitance after 20,000 cycles.

[0120] Figure 6 Cyclic voltammetry (CV) curves of the supercapacitor prepared in Example 2 at scan rates of 5 mV / s and 10 mV / s are shown. As can be seen from the figures, at lower voltage scan rates (5 mV / s and 10 mV / s) and under alkaline electrolyte conditions, the cyclic voltammetry curves exhibit obvious redox peaks.

[0121] Figure 7 The figures show a comparison of the areal capacitance and volumetric capacitance of the supercapacitors prepared in Examples 6, 7, and 8, obtained by cyclic voltammetry at different scan rates. As can be seen from the figures, at lower scan rates, the supercapacitors prepared in Examples 6-8 all exhibit higher areal capacitance and volumetric capacitance.

[0122] The planar electrode prepared in Comparative Example 1 was not doped with an organic nitrogen source. Figure 8 The figures show 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. The figures show a significant improvement in the thin-film electrode performance after nitrogen atom doping modification. Referring to Table 1, the areal capacitance of the supercapacitor prepared in Comparative Example 1 at a scan rate of 25 mV / s is 10.13 mF / cm². 2 The volume capacitance is 9.51 F / cm². 3 It is evident that the supercapacitor prepared using the planar electrode of Comparative Example 1, without nitrogen doping, exhibits inferior performance compared to the supercapacitor prepared in Example 2.

[0123] When preparing the planar electrode in Comparative Example 3, the thickness of the electrode precursor film formed on the substrate reached 30 μm. The excessive thickness would cause the layers far from the heating block to be unreduced, resulting in excessive resistance to electron transport in the longitudinal direction, which would increase the film impedance and affect the capacitance of the planar electrode.

[0124] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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 embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a planar electrode, characterized in that, Includes the following steps: Graphene oxide sheets and a nitrogen source compound are mixed in a solvent to obtain an electrode precursor solution; the graphene oxide sheets have a diameter of 5 μm to 15 μm. The solvent in the electrode precursor solution is removed and the electrode precursor mixture is deposited on the 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 heated in a non-contact manner; in the non-contact heating, the temperature of the heating source is 350℃~600℃, 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.

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 onto the substrate includes removing the solvent by means of evaporation, vacuum filtration or freeze drying.

3. 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 onto the substrate includes: forming a patterned electrode precursor film on the substrate using 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 10 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 and spaced apart from the electrode precursor film, and 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, It is prepared according to any one of claims 1 to 8.

10. A supercapacitor, characterized in that, It includes a first electrode and a second electrode disposed opposite to each other, and an electrolyte disposed between the first electrode and the second electrode, wherein at least one of the first electrode and the second electrode includes a planar electrode as described in claim 9.

Images