Electrode composite material of flexible supercapacitor as well as preparation method and application of electrode composite material

Abstract

The invention belongs to the technical field of electrode materials, and particularly relates to an electrode composite material of a flexible supercapacitor and a preparation method and application of the electrode composite material. According to the method, the nitrogen-doped graphene quantum dots are deposited on the 1T-phase molybdenum disulfide nanosheets growing on the carbon cloth through an electrophoretic deposition method, the method is carried out at normal temperature and normal pressure, N-GQDs aggregation can be avoided, the process is simple, the controllability is high, the applicable material range is wide, and batch production is easy. The prepared flexible composite electrode has excellent electrochemical performance, compared with an original electrode, the specific capacitance value is remarkably improved, the cycling stability is enhanced, the flexible composite electrode can serve as a supercapacitor electrode material, and an assembled flexible all-solid-state symmetrical supercapacitor has good flexibility and electrochemical performance and has wide application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and particularly relates to an electrode composite material for a flexible supercapacitor, a preparation method thereof, and applications thereof. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Supercapacitors can complete the charge and discharge process within a few seconds and have an extremely long cycle life. They can still maintain their energy storage performance after thousands of continuous charge and discharge cycles, showing great application potential in the field of energy storage. In recent years, with the rapid development of flexible electronics technology, flexible supercapacitors have shown irreplaceable application value in emerging fields such as flexible display devices, flexible energy storage systems, wearable flexible electronic products, and implantable medical devices, becoming a hot research direction in the current international research.

[0004] Existing flexible supercapacitors still have problems such as insufficient storage capacity and poor stability, which seriously restrict their application in high-end flexible electronic devices. As the core component of supercapacitors, the performance optimization of electrode materials is the key to solving the above problems. At present, most of the research mainly focuses on the composite of molybdenum disulfide with sulfides or oxides. Transition metal disulfide MoS2 is regarded as a promising electrode material due to its unique layered graphene-like structure (layer spacing ≈ 0.62 nm) and adjustable electronic properties. It is particularly noteworthy that 1T-phase MoS2 exhibits significantly better physical and chemical properties than semiconductor-phase MoS2 (2H and 3R phases). In 1T-phase MoS2, Mo atoms are octahedrally coordinated with adjacent 6 S atoms, and the S-Mo-S atomic stacking order is ABC, with metallic properties. Its conductivity and hydrophilicity are better than those of 2H-phase and 3R-phase molybdenum disulfide, showing great potential in the field of energy storage.

[0005] However, the practical application of 1T-phase MoS2 still faces some challenges, such as poor conductivity and poor phase structure stability. It is easily transformed into the 2H phase during the electrochemical cycling process; the van der Waals force between nanosheets leads to interlayer stacking, resulting in insufficient exposure of active sites, reduced electrochemical activity, and decreased performance. To address these problems, constructing carbon-based nanocomposites has been proven to be an effective solution. Carbon materials, such as carbon black, carbon fiber, carbon nanotubes, graphene, and graphene quantum dots, have excellent conductivity on their own and can significantly promote the performance of supercapacitors; moreover, they can be introduced as reinforcing agents into electrode materials to increase the mechanical properties, cycle stability, and power density of electrode materials. Among them, nitrogen-doped graphene quantum dots (N-GQDs), as a zero-dimensional carbon nanomaterial, have attracted people's attention due to their good conductivity, hydrophilicity, high specific surface area, and numerous active sites. Therefore, the combination of 1T-MoS2 and N-GQDs can improve its conductivity, electrochemical activity, and structural stability. The commonly used composite method is to hydrothermally react N-GQDs with the precursor solution for synthesizing 1T-MoS2. This method is simple to prepare, but there are obvious defects: the uncontrollable aggregation of N-GQDs caused by the high-temperature and high-pressure environment, the performance degradation of the electrode active material due to the transformation of the 1T phase to the 2H phase, and the poor controllability of the synthesis process, which further reduces the conductivity and energy storage performance of the electrode material. Therefore, there is an urgent need for a preparation method of electrode composite materials at room temperature and normal pressure, with controllability and no structural damage. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an electrode composite material for a flexible supercapacitor, its preparation method, and application. Through electrophoresis deposition technology, small-sized N-GQDs are controllably, uniformly, and completely deposited and combined onto 1T-MoS2 nanosheets, significantly enhancing the capacitance performance and structural stability of 1T-MoS2 under the synergistic effect.

[0007] To achieve the above purpose, the technical solution of the present invention is as follows: In the first aspect, the present invention provides a preparation method of an electrode composite material for a flexible supercapacitor, including the following steps: S1. Immerse carbon cloth (CC) in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid for 12 - 24 h. After immersion, wash with deionized water and dry for standby.

[0008] S2. Dissolve a set molar ratio of molybdenum source and sulfur source in deionized water, stir to obtain a uniform precursor solution, put the carbon cloth obtained in S1 into the precursor solution for hydrothermal reaction. After the reaction, ultrasonically clean the product with ethanol and deionized water, and vacuum dry to obtain a 1T-phase molybdenum disulfide flexible electrode (1T-MoS2 / CC).

[0009] S3. Dissolve citric acid and ethylenediamine with a set mass ratio in deionized water, stir and react. After the reaction, dialyze the product and freeze-dry it to obtain nitrogen-doped graphene quantum dots (N-GQDs).

[0010] S4. Dissolve the N-GQDs obtained in step S3 in deionized water as the electrolyte. Place the 1T-MoS2 / CC electrode obtained in step S2 in an electrolytic cell containing the N-GQDs electrolyte and deposit it under a set DC voltage. After the deposition, wash the product and dry it in vacuum to obtain a nitrogen-doped graphene quantum dot / 1T-phase molybdenum disulfide flexible composite electrode (1T-MoS2 / N-GQDs / CC).

[0011] In some embodiments, in step S1, the mass concentrations of concentrated sulfuric acid and concentrated nitric acid are 98% and 68% respectively, and the volume ratio is 1 - 3:1.

[0012] The reason for treating the carbon cloth with the mixed acid of concentrated sulfuric acid and concentrated nitric acid is that the synergistic effect of concentrated sulfuric acid and concentrated nitric acid makes the mixed acid have stronger oxidation ability. The mixed acid oxidizes the carbon cloth more thoroughly than a single acid, introduces richer oxygen-containing functional groups, the reaction is more uniform, and a consistent functional group coverage state can be formed on the entire surface of the carbon cloth fiber, enhancing the hydrophilicity of the carbon cloth and facilitating the more uniform growth of molybdenum disulfide on it. Adjusting the ratio of the mixed acid can balance oxidation and etching, moderately increase the surface roughness while introducing functional groups, and increase the specific surface area.

[0013] In some embodiments, in step S2, the molybdenum source is any one of ammonium molybdate tetrahydrate, sodium molybdate, and molybdenum trioxide, and the sulfur source is any one of thiourea, urea, and thioacetamide. The molybdenum-sulfur molar ratio of the two is 1:4 - 5.

[0014] In some embodiments, the addition amount of the molybdenum source in step S2 is 330 mg.

[0015] In some embodiments, in step S2, the reaction temperature is 160 - 200 °C and the reaction time is 12 - 24 h. If the reaction temperature is too low and the reaction time is too short, it is not easy to generate molybdenum disulfide; if the reaction temperature is too high and the reaction time is too long, the content of the 1T phase will be very low and the content of the 2H phase will be very high.

[0016] In some embodiments, in step S3, the mass ratio of citric acid to ethylenediamine is 3 - 4:1, and the addition amount of citric acid is 6 - 8 g.

[0017] In some embodiments, in step S3, the reaction temperature is 160 - 180 °C and the reaction time is 6 - 10 h. The above reaction temperature and reaction time are the optimal operating parameters for preparing N-GQDs. Uniform small-sized N-GQDs with a high yield can be prepared within this parameter range.

[0018] In some embodiments, in step S4, the concentration of the electrolyte is 0.5 - 0.8 mg / mL, and the volume of the electrolyte is 50 - 60 mL.

[0019] In some embodiments, in step S4, the 1T-MoS2 / CC electrode serves as the working electrode, and the DC voltage for electrophoretic deposition is 1 - 3 V, and the time is 0.5 - 2 h.

[0020] Too low voltage and too short time result in an unclear deposition effect; too high voltage and too long time will cause the molybdenum disulfide to fall off and the N-GQDs to aggregate. Selecting an appropriate voltage range and time range can achieve the controllable deposition of N-GQDs.

[0021] In a second aspect, the present invention provides an electrode composite material prepared by the preparation method described in the first aspect.

[0022] In a third aspect, the present invention provides an application of the electrode composite material described in the second aspect in a flexible supercapacitor.

[0023] Preferably, the electrode composite material 1T-MoS2 / N-GQDs / CC serves as the two electrodes of the flexible supercapacitor, and a flexible all-solid-state symmetric supercapacitor is assembled. The supercapacitor still maintains stable electrochemical performance under the condition of bending 180°.

[0024] The beneficial effects of the present invention are as follows: (1) The electrophoretic deposition method for preparing the electrode composite material provided by the present invention is carried out under normal temperature and pressure conditions compared with the hydrothermal method, which can effectively prevent the self-aggregation of N-GQDs due to the high-temperature and high-pressure environment, maintain the structural integrity and electrochemical activity, and at the same time can improve the controllability by controlling the electrolyte concentration, deposition voltage and deposition time. In the present invention, N-GQDs are used alone, and excellent performance can be achieved without the need to cooperate with other carbon materials.

[0025] (2) After the carbon cloth is treated by acid oxidation in the present invention, its hydrophilicity increases, which is beneficial to the growth of 1T-MoS2 on it. Compared with single acid oxidation treatment, the present invention uses a mixed acid oxidation treatment of concentrated sulfuric acid and concentrated nitric acid. N-GQDs contain rich nitrogen and oxygen functional groups, which endow N-GQDs with good water solubility, conductivity, chemical activity and stability. After being compounded with 1T-MoS2 / CC, it is beneficial to synergistically enhance the overall performance of the 1T-MoS2 flexible electrode, and improve its charge storage capacity and electrochemical stability.

[0026] (3) In the present invention, small-sized N-GQDs are deposited on the surface and between the layers of 1T-MoS2, which can reduce the layer stacking and enhance the chemical stability of 1T-MoS2. When it is applied as an electrode material for supercapacitors, during the testing process, it can effectively reduce the layer collapse of 1T-MoS2 and enhance the structural stability.

[0027] (4) The 1T-MoS2 / N-GQDs / CC electrode prepared in the present invention has excellent electrochemical performance and can be used as an electrode material for supercapacitors in energy storage materials. After compounding, the charge storage capacity and material stability are significantly improved.

[0028] (5) The flexible all-solid-state symmetric supercapacitor assembled with the 1T-MoS2 / N-GQDs / CC electrode prepared in the present invention has excellent flexibility and electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0030] Figure 1 It is the technical roadmap of Example 1 of the present invention.

[0031] Figure 2 It is the SEM diagram of the carbon cloth before and after acid treatment in Example 1 of the present invention. Among them, (a) is the SEM diagram of the carbon cloth before acid treatment, and (b) is the SEM diagram of the carbon cloth after acid treatment.

[0032] Figure 3 It is the SEM diagram of the 1T-MoS2 / CC electrode in Example 1 of the present invention. Among them, (a) is the SEM diagram of the 1T-MoS2 / CC electrode, and (b) is the partial enlarged view of (a).

[0033] Figure 4 It is the Raman spectrum diagram of the 1T-MoS2 / CC electrode in Example 1 of the present invention.

[0034] Figure 5 It is the TEM diagram and size distribution diagram of N-GQDs in Example 1 of the present invention. Among them, (a) is the TEM diagram of N-GQDs, and (b) is the size distribution diagram of N-GQDs.

[0035] Figure 6 It is the infrared spectrum diagram of N-GQDs in Example 1 of the present invention.

[0036] Figure 7 It is the TEM diagram of the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention.

[0037] Figure 8 It is the Mo 3d fine spectrum in the XPS spectra of the 1T-MoS2 / CC electrode and the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention. Among them, (a) is the Mo 3d fine spectrum in the XPS spectrum of the 1T-MoS2 / CC electrode, and (b) is the Mo 3d fine spectrum in the XPS spectrum of the 1T-MoS2 / N-GQDs / CC electrode.

[0038] Figure 9 It is the comparison chart of specific capacitance values of 1T-MoS2 / CC and 1T-MoS2 / N-GQDs / CC electrodes in Example 1 of the present invention at a current density of 1 A / g.

[0039] Figure 10 It is the cycling performance chart of the 1T-MoS2 / CC electrode and the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention. Among them, (a) is the cycling performance chart of the 1T-MoS2 / CC electrode, and (b) is the cycling performance chart of the 1T-MoS2 / N-GQDs / CC electrode.

[0040] Figure 11 It is the CV comparison chart before and after bending 180° at a scanning rate of 20 mV s of the flexible all-solid-state symmetric supercapacitor assembled with the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention. -1 The CV comparison chart before and after bending 180° at a scanning rate of 20 mV s of the flexible all-solid-state symmetric supercapacitor assembled with the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention.

[0041] Figure 12 It is the LED lighting diagram of the flexible all-solid-state symmetric supercapacitor assembled with the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention. Detailed implementation manners

[0042] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0043] The present invention will be further described below in conjunction with embodiments.

[0044] Example 1 S1. Acid treatment of carbon cloth Soak the clean carbon cloth in a mixed acid composed of concentrated sulfuric acid and concentrated nitric acid. The mass concentrations of the two acids are 98% and 68% respectively, and the volume ratio is 3:1. The soaking time is 24 h. After soaking, ultrasonically clean with deionized water and then vacuum dry for later use.

[0045] S2. Preparation of 1T-phase molybdenum disulfide flexible electrode Dissolve 0.33 g of ammonium molybdate tetrahydrate and 0.72 g of thiourea in 30 mL of deionized water, stir well to obtain a homogeneous precursor solution. Put the carbon cloth obtained in step S1 into the precursor solution, carry out a hydrothermal reaction in a reaction kettle, the reaction temperature is 180 °C, and the reaction time is 12 h. After the reaction, ultrasonically clean the product with ethanol and deionized water, and dry it under vacuum to obtain a 1T-MoS2 / CC electrode.

[0046] S3. Preparation of nitrogen-doped graphene quantum dots Dissolve 6 g of citric acid and 2 g of ethylenediamine in 60 mL of deionized water, stir well to obtain a homogeneous solution, carry out a reaction in a reaction kettle, the reaction temperature is 180 °C, and the reaction time is 6 h. After the reaction, dialyze the product and then freeze-dry it to obtain N-GQDs.

[0047] S4. Preparation of electrode composite materials Take 30 mg of the N-GQDs obtained in step S3 and dissolve it in 60 mL of deionized water as the electrolyte. Place the 1T-MoS2 / CC electrode obtained in step S2 in an electrolytic cell containing the N-GQDs electrolyte as the working electrode, and deposit it for 1 h at a DC voltage of 2 V using an electrochemical workstation. After cleaning the product, dry it under vacuum to obtain a 1T-MoS2 / N-GQDs / CC electrode.

[0048] Example 2 S1. Acid treatment of carbon cloth Soak the clean carbon cloth in a mixed acid composed of concentrated sulfuric acid and concentrated nitric acid. The mass concentrations of the two acids are 98% and 68% respectively, and the volume ratio is 2:1. The soaking time is 18 h. After soaking, ultrasonically clean it with deionized water and then dry it under vacuum for standby.

[0049] S2. Preparation of 1T-phase molybdenum disulfide flexible electrode Dissolve 0.33 g of ammonium molybdate tetrahydrate and 0.72 g of thiourea in 30 mL of deionized water, stir well to obtain a homogeneous precursor solution. Put the carbon cloth obtained in step S1 into the precursor solution, carry out a reaction in a reaction kettle, the reaction temperature is 200 °C, and the reaction time is 12 h. After the reaction, ultrasonically clean the product with ethanol and deionized water, and dry it under vacuum to obtain a 1T-MoS2 / CC electrode.

[0050] S3. Preparation of nitrogen-doped graphene quantum dots Dissolve 8 g of citric acid and 3 g of ethylenediamine in 80 mL of deionized water, stir well to obtain a homogeneous solution, carry out a reaction in a reaction kettle, the reaction temperature is 160 °C, and the reaction time is 10 h. After the reaction, dialyze the product and then freeze-dry it to obtain N-GQDs.

[0051] S4. Preparation of Electrode Composite Material Take 30 mg of the N-GQDs obtained in step S3 and dissolve it in 50 mL of deionized water as the electrolyte. Place the 1T-MoS2 / CC electrode obtained in step S2 in the electrolytic cell containing the N-GQDs electrolyte as the working electrode, and use an electrochemical workstation to deposit for 1 h at a DC voltage of 3 V. After washing the product, dry it in vacuum to obtain the 1T-MoS2 / N-GQDs / CC electrode.

[0052] Example 3 S1. Acid Treatment of Carbon Cloth Soak the clean carbon cloth in a mixed acid composed of concentrated sulfuric acid and concentrated nitric acid. The mass concentrations of the two acids are 98% and 68% respectively, and the volume ratio is 2:1. The soaking time is 12 h. After soaking, ultrasonically clean it with deionized water and then dry it in vacuum for standby.

[0053] S2. Preparation of 1T-Phase Molybdenum Disulfide Flexible Electrode Dissolve 0.33 g of ammonium molybdate tetrahydrate and 0.57 g of thiourea in 30 mL of deionized water, and stir well to obtain a uniform precursor solution. Put the carbon cloth obtained in step S1 into the precursor solution, and carry out the reaction in a reaction kettle. The reaction temperature is 160 °C and the reaction time is 24 h. After the reaction, ultrasonically clean the product with ethanol and deionized water, and dry it in vacuum to obtain the 1T-MoS2 / CC electrode.

[0054] S3. Preparation of Nitrogen-Doped Graphene Quantum Dots Dissolve 7 g of citric acid and 2 g of ethylenediamine in 60 mL of deionized water, stir well to obtain a uniform solution, and carry out the reaction in a reaction kettle. The reaction temperature is 180 °C and the reaction time is 6 h. After the reaction, dialyze the product and then freeze-dry it to obtain N-GQDs.

[0055] S4. Preparation of Electrode Composite Material Take 48 mg of the N-GQDs obtained in step S3 and dissolve it in 60 mL of deionized water as the electrolyte. Place the 1T-MoS2 / CC electrode obtained in step S2 in the electrolytic cell containing the N-GQDs electrolyte as the working electrode, and use an electrochemical workstation to deposit for 1 h at a DC voltage of 1 V. After washing the product, dry it in vacuum to obtain the 1T-MoS2 / N-GQDs / CC electrode.

[0056] Example 4 S1. Acid Treatment of Carbon Cloth Soak the clean carbon cloth in a mixed acid composed of concentrated sulfuric acid and concentrated nitric acid. The mass concentrations of the two acids are 98% and 68% respectively, and the volume ratio is 1:1. The soaking time is 24 h. After soaking, ultrasonically clean it with deionized water and then vacuum dry it for standby.

[0057] S2. Preparation of 1T-phase molybdenum disulfide flexible electrode Dissolve 0.33 g of ammonium molybdate tetrahydrate and 0.72 g of thiourea in 30 mL of deionized water, and stir well to obtain a homogeneous precursor solution. Put the carbon cloth obtained in step S1 into the precursor solution, and carry out the reaction in a reaction kettle. The reaction temperature is 180 °C and the reaction time is 16 h. After the reaction, ultrasonically clean the product with ethanol and deionized water, and vacuum dry it to obtain the 1T-MoS2 / CC electrode.

[0058] S3. Preparation of nitrogen-doped graphene quantum dots Dissolve 6 g of citric acid and 1.5 g of ethylenediamine in 60 mL of deionized water, stir well to obtain a homogeneous solution, and carry out the reaction in a reaction kettle. The reaction temperature is 180 °C and the reaction time is 10 h. After the reaction, dialyze the product and then freeze-dry it to obtain N-GQDs.

[0059] S4. Preparation of electrode composite material Take 40 mg of the N-GQDs obtained in step S3 and dissolve it in 60 mL of deionized water as the electrolyte. Place the 1T-MoS2 / CC electrode obtained in step S2 in an electrolytic cell containing the N-GQDs electrolyte as the working electrode, and use an electrochemical workstation to deposit at a DC voltage of 2 V for 2 h. After cleaning the product, vacuum dry it to obtain the 1T-MoS2 / N-GQDs / CC electrode.

[0060] Example 5 S1. Acid treatment of carbon cloth Soak the clean carbon cloth in a mixed acid composed of concentrated sulfuric acid and concentrated nitric acid. The mass concentrations of the two acids are 98% and 68% respectively, and the volume ratio is 2:1. The soaking time is 20 h. After soaking, ultrasonically clean it with deionized water and then vacuum dry it for standby.

[0061] S2. Preparation of 1T-phase molybdenum disulfide flexible electrode Dissolve 0.33 g of ammonium molybdate tetrahydrate and 0.72 g of thiourea in 30 mL of deionized water, and stir well to obtain a homogeneous precursor solution. Put the carbon cloth obtained in step S1 into the precursor solution, and carry out the reaction in a reaction kettle. The reaction temperature is 180 °C and the reaction time is 24 h. After the reaction, ultrasonically clean the product with ethanol and deionized water, and vacuum dry it to obtain the 1T-MoS2 / CC electrode.

[0062] S3. Preparation of Nitrogen-doped Graphene Quantum Dots Dissolve 6 g of citric acid and 2 g of ethylenediamine in 60 mL of deionized water, stir well to obtain a homogeneous solution, carry out the reaction in a reaction kettle, the reaction temperature is 180 °C, the reaction time is 8 h, after the reaction is completed, dialyze the product and then freeze-dry to obtain N-GQDs.

[0063] S4. Preparation of Electrode Composite Material Take 35 mg of the N-GQDs obtained in step S3 and dissolve it in 60 mL of deionized water as the electrolyte. Place the 1T-MoS2 / CC electrode obtained in step S2 in an electrolytic cell containing the N-GQDs electrolyte as the working electrode, and use an electrochemical workstation to deposit at a DC voltage of 2 V for 0.5 h. After washing the product, dry it under vacuum to obtain the 1T-MoS2 / N-GQDs / CC electrode.

[0064] Results and Analysis Figure 1 This is the technical roadmap of the present invention. This figure details the technical roadmap for the preparation of the 1T-MoS2 / N-GQDs / CC electrode.

[0065] Figure 2 This is the SEM image of the carbon cloth before and after acid treatment in Example 1 of the present invention. Among them, Figure 2 (a) in it is the SEM image of the carbon cloth before acid treatment, Figure 2 (b) in it is the SEM image of the carbon cloth after acid treatment. It can be seen from the figure that the surface of the carbon cloth without acid treatment is relatively smooth. After acid treatment, obvious changes have occurred on the surface of the carbon cloth, and grooves after acid etching appear on the fiber surface, and the fiber surface becomes rougher. Such a structure improves the contact between the surface and water molecules, thereby enhancing the hydrophilicity of the carbon cloth.

[0066] Figure 3 This is the SEM image of the 1T-MoS2 / CC electrode in Example 1 of the present invention. From Figure 3 (a) in it, it can be seen that MoS2 grows uniformly on the surface of the carbon cloth, Figure 3 (b) in it is Figure 3 the partial enlarged view of the image within the red frame in (a) of it. It can be seen from the figure that MoS2 grows uniformly on the surface of the carbon cloth in the form of nanosheets and nanospherical flowers, and the size of the MoS2 nanospherical flowers is 400 - 600 nm.

[0067] Figure 4 This is the Raman spectrum of the 1T-MoS2 / CC electrode in Example 1 of the present invention. In the figure, at 149 cm -1 、235 cm -1 、334 cm -1The characteristic peaks at this position respectively correspond to the characteristic peaks of J1, J2, and J3 of 1T-MoS2, 1345 cm -1 and 1592 cm -1 The peaks at this position respectively correspond to the D peak and G peak of the carbon cloth. Therefore, it can be proved that 1T-MoS2 has been successfully grown on the carbon cloth.

[0068] Figure 5 This is the TEM image and size distribution diagram of N-GQDs in Example 1 of the present invention. Among them, Figure 5 (a) in it is the TEM image of N-GQDs, Figure 5 (b) in it is the size distribution diagram of N-GQDs. It can be seen from the figure that the prepared N-GQDs are nanoscale in size, and the average size is 2.52 nm.

[0069] Figure 6 This is the infrared spectrum of N-GQDs in Example 1 of the present invention. In the figure, 3260 cm -1 and 1398 cm -1 The absorption peaks at this position respectively correspond to the stretching vibration of N-H and the bending vibration of C-N, indicating that the prepared N-GQDs are successfully prepared.

[0070] Figure 7 This is the TEM image of the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention. The small-sized N-GQDs are marked in cyan in the figure. After calculation, the lattice spacing is 0.24 nm, corresponding to the (110) crystal plane of graphene. The white-marked ones are 1T-MoS2, and the calculated lattice spacing is 0.66 nm, corresponding to the (110) crystal plane of 1T-MoS2, which is expanded relative to the (110) crystal plane of the 2H phase. It can be observed from the figure that N-GQDs with a size of 2 - 5 nm are successfully deposited on the 1T-MoS2 / CC electrode.

[0071] Figure 8 This is the Mo 3d fine spectrum in the XPS spectra of the 1T-MoS2 / CC electrode and the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention. Among them, Figure 8 (a) in it is the Mo 3d fine spectrum in the XPS spectrum of the 1T-MoS2 / CC electrode, Figure 8 (b) in it is the Mo 3d fine spectrum in the XPS spectrum of the 1T-MoS2 / N-GQDs / CC electrode. It can be seen from the figure that the content of the 1T phase in MoS2 is very high. Through the analysis of the peak fitting results, the content of the 1T phase is about 66%. At the same time, compared with the 1T-MoS2 / CC electrode, for the 1T-MoS2 / N-GQDs / CC electrode, the Mo 3d 5 / 2 、Mo 3d3 / 2 The atomic orbital has shifted 0.2 eV towards the direction of lower binding energy, indicating that the addition of N-GQDs is beneficial to improving the chemical stability of 1T-MoS2 / CC.

[0072] Figure 9 This is a comparison chart of the specific capacitance values of the 1T-MoS2 / CC and 1T-MoS2 / N-GQDs / CC electrodes in Example 1 of the present invention at a current density of 1 A / g. From the chart, it can be calculated that the mass specific capacitances of 1T-MoS2 / CC and 1T-MoS2 / N-GQDs / CC are 428 F g -1 and 917 F g -1 respectively, and the addition of N-GQDs increases the specific capacitance value by 114%.

[0073] Figure 10 This is the cyclic performance chart of the 1T-MoS2 / CC electrode and the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention. Among them, Figure 10 in (a) is the cyclic performance chart of 1T-MoS2 / CC at a current density of 20 A g -1 , Figure 10 in (b) is the cyclic performance chart of the 1T-MoS2 / N-GQDs / CC electrode at a current density of 30 A g -1 . It can be seen from the chart that after 5000 cycles of constant current charge and discharge, the capacitance retention rates of 1T-MoS2 / CC and 1T-MoS2 / N-GQDs / CC are 84.2% and 93.7% respectively, and the addition of N-GQDs improves the cyclic stability.

[0074] Figure 11 This is the CV comparison chart before and after bending 180° at a scanning rate of 20 mV s -1 for the flexible all-solid-state symmetric supercapacitor assembled with the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention. It can be seen from the chart that the CV curves before and after folding coincide highly, indicating that the device with carbon cloth as the current collector has good stability and flexibility.

[0075] Figure 12 This is the LED lighting diagram of the flexible all-solid-state symmetric supercapacitor assembled with the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention. Three devices connected in series can light up the LED for at least 7 minutes.

[0076] In summary, the present invention uses the method of electrophoretic deposition to deposit small-sized N-GQDs on the surface and between the layers of 1T-MoS2, which can reduce the stacking of 1T-MoS2 layers, and the N-GQDs are evenly distributed, which can enhance the chemical stability of 1T-MoS2, thereby improving its electrochemical storage performance and greatly improving the capacitance performance of the material. The flexible all-solid-state symmetric supercapacitor assembled with the 1T-MoS2 / N-GQDs / CC electrode has good application value.

[0077] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of an electrode composite material for a flexible supercapacitor, characterized in that, It includes the following steps: S1. Immerse the carbon cloth in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid for 12 - 24 h. After immersion, wash it and dry it for standby; S2. Dissolve the molybdenum source and sulfur source with a set molar ratio in deionized water, stir to obtain a uniform precursor solution. Put the carbon cloth obtained in S1 into the precursor solution and react at a set temperature. After the reaction, ultrasonically wash the product with ethanol and deionized water, and vacuum dry it to obtain a 1T-phase molybdenum disulfide flexible electrode, namely 1T-MoS2 / CC; S3. Dissolve citric acid and ethylenediamine with a set mass ratio in deionized water. After stirring, react at a set temperature. After the reaction, dialyze the product and then freeze-dry it to obtain nitrogen-doped graphene quantum dots, namely N-GQDs; S4. Dissolve the N-GQDs obtained in step S3 in deionized water as the electrolyte. Place the 1T-MoS2 / CC electrode obtained in step S2 in an electrolytic cell filled with the N-GQDs electrolyte, deposit it under a set DC voltage, wash the product and then vacuum dry it to obtain a nitrogen-doped graphene quantum dot / 1T-phase molybdenum disulfide flexible composite electrode, namely 1T-MoS2 / N-GQDs / CC.

2. The method according to claim 1, characterized in that, In step S1, the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 1 - 3:

1.

3. The method according to claim 1, wherein In step S2, the molybdenum source is any one of ammonium molybdate tetrahydrate, sodium molybdate and molybdenum trioxide, and the sulfur source is any one of thiourea, urea and thioacetamide.

4. The method according to claim 1, characterized in that In step S2, the reaction temperature is 160 - 200 °C, and the reaction time is 12 - 24 h.

5. The method according to claim 1, wherein In step S3, the mass ratio of citric acid to ethylenediamine is 3 - 4:1, and the addition amount of citric acid is 6 - 8 g.

6. The method according to claim 1, characterized in that, In step S3, the reaction temperature is 160 - 180 °C, and the reaction time is 6 - 10 h.

7. The method according to claim 1, characterized in that In step S4, the concentration of the electrolyte is 0.5 - 0.8 mg / mL, the volume of the electrolyte is 50 - 60 mL, the 1T-MoS2 / CC electrode is used as the working electrode, the DC voltage for electrophoretic deposition is 1 - 3 V, and the time is 0.5 - 2 h.

8. An electrode composite material prepared by the preparation method according to any one of claims 1 - 7.

9. Application of the electrode composite material according to claim 8 in a flexible supercapacitor.

10. The application according to claim 9, wherein The electrode composite material 1T-MoS2 / N-GQDs / CC is used as two electrodes of a flexible supercapacitor to assemble a flexible all-solid symmetric supercapacitor.

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