Electrode composite material for flexible supercapacitor, preparation method and application thereof

Abstract

The present invention belongs to the field of electrode material technology, and specifically relates to a flexible supercapacitor electrode composite material, its preparation method and application. The present invention deposits nitrogen-doped graphene quantum dots onto 1T-phase molybdenum disulfide nanosheets grown on carbon cloth by an electrophoretic deposition method. The method is carried out at room temperature and pressure, which can avoid the aggregation of N‑GQDs. The process is simple, highly controllable, applicable to a wide range of materials and easy to mass produce. The prepared flexible composite electrode has excellent electrochemical properties, significantly improved capacitance value compared to the original electrode, and enhanced cycle stability. It can be used as a supercapacitor electrode material. The assembled flexible all-solid-state symmetrical supercapacitor has good flexibility and electrochemical properties, and has broad application prospects.

Description

Technical Field

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

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Supercapacitors can charge and discharge in seconds and have an extremely long cycle life, maintaining their energy storage performance after thousands of consecutive charge and discharge cycles. They demonstrate enormous potential for application in energy storage. In recent years, with the rapid development of flexible electronics, flexible supercapacitors have demonstrated irreplaceable application value in emerging fields such as flexible displays, flexible energy storage systems, wearable flexible electronics, and implantable medical devices, becoming a hot topic of international research.

[0004] Existing flexible supercapacitors still suffer from limited storage capacity and poor stability, severely hindering their application in high-end flexible electronic devices. As a core component of supercapacitors, optimizing the performance of electrode materials is key to addressing these issues. Currently, much research has focused on combining molybdenum disulfide with sulfides or oxides. Transition metal disulfides (MoS2) are considered promising electrode materials due to their unique layered graphene-like structure (interlayer spacing ≈0.62 nm) and tunable electronic properties. Particularly noteworthy, 1T phase MoS2 exhibits significantly superior physicochemical properties to those of the semiconducting phases (2H and 3R phases). In 1T phase MoS2, Mo atoms are octahedrally coordinated with six adjacent S atoms, resulting in an ABC stacking order of S-Mo-S atoms, exhibiting metallic properties. Its conductivity and hydrophilicity are superior to those of 2H and 3R phases, demonstrating its enormous potential in the field of energy storage.

[0005] However, the practical application of 1T-phase MoS2 still faces several challenges, such as poor conductivity and structural stability. It easily transforms into the 2H phase during electrochemical cycling. Van der Waals forces between nanosheets lead to interlayer stacking, resulting in insufficient exposure of active sites, reduced electrochemical activity, and decreased performance. To address these issues, the construction of carbon-based nanocomposites has proven to be an effective solution. Carbon materials, such as carbon black, carbon fibers, carbon nanotubes, graphene, and graphene quantum dots, possess excellent electrical conductivity and significantly enhance the performance of supercapacitors. They can also be incorporated into electrode materials as reinforcing agents to improve their mechanical properties, cycling stability, and power density. Among them, nitrogen-doped graphene quantum dots (N-GQDs), a zero-dimensional carbon nanomaterial, have attracted attention due to their excellent electrical conductivity and hydrophilicity, high specific surface area, and numerous active sites. Therefore, combining 1T-MoS2 with N-GQDs can improve its conductivity, electrochemical activity, and structural stability. The commonly used composite method currently involves hydrothermal reaction of N-GQDs with a precursor solution for synthesizing 1T-MoS2. This method is simple to prepare, but has significant drawbacks: the high temperature and high pressure environment causes uncontrolled aggregation of N-GQDs, the transformation of the 1T phase to the 2H phase leads to a decrease in the performance of the electrode active material, and the poor controllability of the synthesis process, which in turn reduces the conductivity and energy storage performance of the electrode material. Therefore, a controllable and structurally damage-free preparation method for electrode composite materials at room temperature and pressure is urgently needed. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention provides a flexible supercapacitor electrode composite material, its preparation method, and its application. By using electrophoretic deposition technology, small-sized N-GQDs are controllably, uniformly, and completely deposited onto 1T-MoS2 nanosheets, significantly enhancing the capacitance performance and structural stability of the 1T-MoS2 through synergistic effects.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] In a first aspect, the present invention provides a method for preparing an electrode composite material for a flexible supercapacitor, comprising the following steps:

[0009] S1. Soak the carbon cloth (CC) in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid for 12-24 hours. After soaking, rinse with deionized water and dry for later use.

[0010] S2. Dissolve the molybdenum source and sulfur source in a set molar ratio in deionized water and stir to obtain a uniform precursor solution. Place 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 it to obtain a 1T phase molybdenum disulfide flexible electrode (1T-MoS2 / CC).

[0011] S3. Dissolve citric acid and ethylenediamine in a set mass ratio in deionized water, stir and react. After the reaction is completed, dialyze the product and freeze-dry it to obtain nitrogen-doped graphene quantum dots (N-GQDs).

[0012] S4. Dissolve the N-GQDs obtained in step S3 in deionized water as an electrolyte, place the 1T-MoS2 / CC electrode obtained in step S2 in an electrolytic cell filled with the N-GQDs electrolyte, and deposit it under a set DC voltage. After the deposition is completed, the product is cleaned and vacuum-dried to obtain a nitrogen-doped graphene quantum dot / 1T phase molybdenum disulfide flexible composite electrode (1T-MoS2 / N-GQDs / CC).

[0013] 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.

[0014] The carbon cloth is treated with a mixture of concentrated sulfuric acid and nitric acid because the synergistic effect of the two acids gives the mixed acid a stronger oxidizing ability. This mixture oxidizes the carbon cloth more thoroughly than a single acid, introducing a richer variety of oxygen-containing functional groups and a more uniform reaction. This creates a consistent functional group coverage across the entire carbon cloth fiber surface, enhancing its hydrophilicity and facilitating more uniform growth of molybdenum disulfide. Adjusting the ratio of the mixed acid balances oxidation and etching, introducing functional groups while also moderately increasing surface roughness and improving specific surface area.

[0015] 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, and the molar ratio of molybdenum to sulfur between the two is 1:4~5.

[0016] In some embodiments, the amount of the molybdenum source added in step S2 is 330 mg.

[0017] In some embodiments, in step S2, the reaction temperature is 160-200°C and the reaction time is 12-24 hours. If the reaction temperature is too low or the reaction time is too short, molybdenum disulfide is not easily formed. If the reaction temperature is too high or the reaction time is too long, the 1T phase content is very low and the 2H phase content is very high.

[0018] In some embodiments, in step S3, the mass ratio of citric acid to ethylenediamine is 3-4:1, and the amount of citric acid added is 6-8 g.

[0019] In some embodiments, in step S3, the reaction temperature is 160-180°C and the reaction time is 6-10 hours. The above reaction temperature and reaction time are the optimal operating parameters for preparing N-GQDs. Within this parameter range, small-sized N-GQDs with uniform particle size can be prepared with high yield.

[0020] 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.

[0021] In some embodiments, in step S4, the 1T-MoS2 / CC electrode is used as the working electrode, the DC voltage of the electrophoretic deposition is 1-3 V, and the time is 0.5-2 h.

[0022] If the voltage is too low and the time is too short, the deposition effect will be unclear; if the voltage is too high and the time is too long, the MoS2 will fall off and the N-GQDs will aggregate. Selecting the appropriate voltage range and time range can achieve controllable deposition of N-GQDs.

[0023] In a second aspect, the present invention provides an electrode composite material prepared by the preparation method described in the first aspect.

[0024] In a third aspect, the present invention provides an application of the electrode composite material described in the second aspect in a flexible supercapacitor.

[0025] Preferably, the electrode composite material 1T-MoS2 / N-GQDs / CC is used as two electrodes of a flexible supercapacitor to assemble a flexible all-solid-state symmetrical supercapacitor, and the supercapacitor maintains stable electrochemical performance when bent 180°.

[0026] The beneficial effects of the present invention are:

[0027] (1) Compared with the hydrothermal method, the electrophoretic deposition electrode composite material composite method provided by the present invention is carried out under normal temperature and pressure conditions, which can effectively prevent the self-aggregation of N-GQDs caused by high temperature and high pressure environment, maintain structural integrity and electrochemical activity, and improve controllability by controlling the electrolyte concentration, deposition voltage and deposition time. In the present invention, N-GQDs are used alone and do not need to be used in conjunction with other carbon materials to achieve excellent performance.

[0028] (2) After acid oxidation treatment, the carbon cloth in the present invention has increased hydrophilicity, which is conducive 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 give N-GQDs good water solubility, conductivity, chemical activity and stability. After being composited 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.

[0029] (3) The small-sized N-GQDs in the present invention are deposited on the surface and between the layers of 1T-MoS2, which can reduce the stacking of the layers and enhance the chemical stability of 1T-MoS2. When used as supercapacitor electrode materials, they can effectively reduce the collapse of the 1T-MoS2 layers during testing and enhance the structural stability.

[0030] (4) The 1T-MoS2 / N-GQDs / CC electrode prepared in the present invention has excellent electrochemical properties and can be used as an electrode material for supercapacitors among energy storage materials. After composite, the charge storage capacity and material stability are significantly improved.

[0031] (5) The flexible all-solid-state symmetrical supercapacitor assembled with 1T-MoS2 / N-GQDs / CC electrodes prepared in the present invention has excellent flexibility and electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0033] Figure 1 This is the technical roadmap of Example 1 of the present invention.

[0034] Figure 2 These are SEM images of the carbon cloth before and after acid treatment in Example 1 of the present invention, wherein (a) is the SEM image before carbon cloth treatment and (b) is the SEM image after carbon cloth treatment.

[0035] Figure 3 These are SEM images of the 1T-MoS2 / CC electrode in Example 1 of the present invention, wherein (a) is the SEM image of the 1T-MoS2 / CC electrode and (b) is a local enlarged image of (a).

[0036] Figure 4 This is the Raman spectrum of the 1T-MoS2 / CC electrode in Example 1 of the present invention.

[0037] Figure 5 TEM images of N-GQDs and size distribution diagrams of N-GQDs in Example 1 of the present invention, wherein (a) is the TEM image of N-GQDs, and (b) is the size distribution diagram of N-GQDs.

[0038] Figure 6 This is the infrared spectrum of N-GQDs in Example 1 of the present invention.

[0039] Figure 7 This is the TEM image of the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention.

[0040] Figure 8 These are the Mo 3d fine spectra in the XPS energy spectra of the 1T-MoS2 / CC electrode and the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention, wherein (a) is the Mo 3d fine spectrum in the XPS energy spectra of the 1T-MoS2 / CC electrode, and (b) is the Mo 3d fine spectrum in the XPS energy spectra of the 1T-MoS2 / N-GQDs / CC electrode.

[0041] Figure 9 This is a comparison chart of the 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.

[0042] Figure 10 These are the cycle performance diagrams of the 1T-MoS2 / CC electrode and the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention, where (a) is the cycle performance diagram of the 1T-MoS2 / CC electrode and (b) is the cycle performance diagram of the 1T-MoS2 / N-GQDs / CC electrode.

[0043] Figure 11 The flexible all-solid-state symmetrical supercapacitor assembled with 1T-MoS2 / N-GQDs / CC electrodes in Example 1 of the present invention has a capacitance of 20 mV s -1 CV comparison diagram before and after bending 180° at scanning rate.

[0044] Figure 12 This is a picture of a flexible all-solid-state symmetrical supercapacitor assembled with 1T-MoS2 / N-GQDs / CC electrodes in Example 1 of the present invention lighting up an LED. DETAILED DESCRIPTION

[0045] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0046] The present invention will be further described below with reference to the embodiments.

[0047] Example 1

[0048] S1. Acid treatment of carbon cloth

[0049] The clean carbon cloth was soaked in a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid. The mass concentrations of the two acids were 98% and 68%, respectively, and the volume ratio was 3:1. The soaking time was 24 h. After the soaking was completed, the carbon cloth was ultrasonically cleaned with deionized water and vacuum dried for later use.

[0050] Preparation of S2 and 1T phase MoS2 flexible electrodes

[0051] 0.33 g of ammonium molybdate tetrahydrate and 0.72 g of thiourea were dissolved in 30 mL of deionized water and stirred thoroughly to obtain a uniform precursor solution. The carbon cloth obtained in step S1 was placed in the precursor solution and a hydrothermal reaction was carried out in a reactor at a reaction temperature of 180°C for 12 h. After the reaction, the product was ultrasonically cleaned with ethanol and deionized water and dried in vacuum to obtain a 1T-MoS2 / CC electrode.

[0052] S3. Preparation of nitrogen-doped graphene quantum dots

[0053] 6 g of citric acid and 2 g of ethylenediamine were dissolved in 60 mL of deionized water and stirred thoroughly to obtain a uniform solution. The solution was reacted in a reactor at a temperature of 180°C for 6 h. After the reaction, the product was dialyzed and freeze-dried to obtain N-GQDs.

[0054] S4. Preparation of electrode composite materials

[0055] Take 30 mg of the N-GQDs obtained in step S3 and dissolve them in 60 mL of deionized water as the electrolyte. The 1T-MoS2 / CC electrode obtained in step S2 is placed in an electrolytic cell filled with the N-GQDs electrolyte as the working electrode. Use an electrochemical workstation to deposit at a DC voltage of 2 V for 1 h. After washing, the product is vacuum-dried to obtain a 1T-MoS2 / N-GQDs / CC electrode.

[0056] Example 2

[0057] S1. Acid treatment of carbon cloth

[0058] The clean carbon cloth was soaked in a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid. The mass concentrations of the two acids were 98% and 68%, respectively, and the volume ratio was 2:1. The soaking time was 18 h. After the soaking was completed, the carbon cloth was ultrasonically cleaned with deionized water and vacuum dried for later use.

[0059] Preparation of S2 and 1T phase MoS2 flexible electrodes

[0060] 0.33 g of ammonium molybdate tetrahydrate and 0.72 g of thiourea were dissolved in 30 mL of deionized water and stirred thoroughly to obtain a uniform precursor solution. The carbon cloth obtained in step S1 was placed in the precursor solution and reacted in a reactor at a temperature of 200°C for 12 h. After the reaction, the product was ultrasonically cleaned with ethanol and deionized water and dried in vacuum to obtain a 1T-MoS2 / CC electrode.

[0061] S3. Preparation of nitrogen-doped graphene quantum dots

[0062] 8 g of citric acid and 3 g of ethylenediamine were dissolved in 80 mL of deionized water and stirred thoroughly to obtain a uniform solution. The solution was reacted in a reactor at a temperature of 160°C for 10 h. After the reaction, the product was dialyzed and freeze-dried to obtain N-GQDs.

[0063] S4. Preparation of electrode composite materials

[0064] Take 30 mg of the N-GQDs obtained in step S3 and dissolve them in 50 mL of deionized water as the electrolyte. The 1T-MoS2 / CC electrode obtained in step S2 is placed in an electrolytic cell filled with the N-GQDs electrolyte as the working electrode. Use an electrochemical workstation to deposit at a DC voltage of 3 V for 1 h. After washing, the product is vacuum-dried to obtain a 1T-MoS2 / N-GQDs / CC electrode.

[0065] Example 3

[0066] S1. Acid treatment of carbon cloth

[0067] The clean carbon cloth was soaked in a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid. The mass concentrations of the two acids were 98% and 68%, respectively, and the volume ratio was 2:1. The soaking time was 12 h. After the soaking was completed, the carbon cloth was ultrasonically cleaned with deionized water and vacuum dried for later use.

[0068] Preparation of S2 and 1T phase MoS2 flexible electrodes

[0069] 0.33 g of ammonium molybdate tetrahydrate and 0.57 g of thiourea were dissolved in 30 mL of deionized water and stirred thoroughly to obtain a uniform precursor solution. The carbon cloth obtained in step S1 was placed in the precursor solution and reacted in a reactor at a temperature of 160°C for 24 h. After the reaction, the product was ultrasonically cleaned with ethanol and deionized water and dried in vacuum to obtain a 1T-MoS2 / CC electrode.

[0070] S3. Preparation of nitrogen-doped graphene quantum dots

[0071] 7 g of citric acid and 2 g of ethylenediamine were dissolved in 60 mL of deionized water and stirred thoroughly to obtain a uniform solution. The solution was reacted in a reactor at a temperature of 180°C for 6 h. After the reaction, the product was dialyzed and freeze-dried to obtain N-GQDs.

[0072] S4. Preparation of electrode composite materials

[0073] Take 48 mg of the N-GQDs obtained in step S3 and dissolve it in 60 mL of deionized water as the electrolyte. The 1T-MoS2 / CC electrode obtained in step S2 is placed in an electrolytic cell filled with the N-GQDs electrolyte as the working electrode. Use an electrochemical workstation to deposit at a DC voltage of 1 V for 1 h. After washing, the product is vacuum-dried to obtain a 1T-MoS2 / N-GQDs / CC electrode.

[0074] Example 4

[0075] S1. Acid treatment of carbon cloth

[0076] The clean carbon cloth was soaked in a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid. The mass concentrations of the two acids were 98% and 68%, respectively, and the volume ratio was 1:1. The soaking time was 24 h. After the soaking, it was ultrasonically cleaned with deionized water and vacuum dried for later use.

[0077] Preparation of S2 and 1T phase MoS2 flexible electrodes

[0078] 0.33 g of ammonium molybdate tetrahydrate and 0.72 g of thiourea were dissolved in 30 mL of deionized water and stirred thoroughly to obtain a uniform precursor solution. The carbon cloth obtained in step S1 was placed in the precursor solution and reacted in a reactor at a temperature of 180°C for 16 h. After the reaction, the product was ultrasonically cleaned with ethanol and deionized water and vacuum dried to obtain a 1T-MoS2 / CC electrode.

[0079] S3. Preparation of nitrogen-doped graphene quantum dots

[0080] 6 g of citric acid and 1.5 g of ethylenediamine were dissolved in 60 mL of deionized water and stirred thoroughly to obtain a uniform solution. The solution was reacted in a reactor at a temperature of 180°C for 10 h. After the reaction, the product was dialyzed and freeze-dried to obtain N-GQDs.

[0081] S4. Preparation of electrode composite materials

[0082] Take 40 mg of the N-GQDs obtained in step S3 and dissolve it in 60 mL of deionized water as the electrolyte. The 1T-MoS2 / CC electrode obtained in step S2 is placed in an electrolytic cell filled with the N-GQDs electrolyte as the working electrode. Use an electrochemical workstation to deposit at a DC voltage of 2 V for 2 h. After washing, the product is vacuum-dried to obtain a 1T-MoS2 / N-GQDs / CC electrode.

[0083] Example 5

[0084] S1. Acid treatment of carbon cloth

[0085] The clean carbon cloth was soaked in a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid. The mass concentrations of the two acids were 98% and 68%, respectively, and the volume ratio was 2:1. The soaking time was 20 h. After the soaking, it was ultrasonically cleaned with deionized water and vacuum dried for later use.

[0086] Preparation of S2 and 1T phase MoS2 flexible electrodes

[0087] Dissolve 0.33 g of ammonium molybdate tetrahydrate and 0.72 g of thiourea in 30 mL of deionized water and stir thoroughly to obtain a uniform precursor solution. Add the carbon cloth obtained in step S1 to the precursor solution and react in a reactor at 180°C for 24 hours. After the reaction, ultrasonically clean the product with ethanol and deionized water and dry it in a vacuum oven to obtain a 1T-MoS2 / CC electrode.

[0088] S3. Preparation of nitrogen-doped graphene quantum dots

[0089] 6 g of citric acid and 2 g of ethylenediamine were dissolved in 60 mL of deionized water and stirred thoroughly to obtain a uniform solution. The solution was reacted in a reactor at a temperature of 180°C for 8 h. After the reaction, the product was dialyzed and freeze-dried to obtain N-GQDs.

[0090] S4. Preparation of electrode composite materials

[0091] Take 35 mg of the N-GQDs obtained in step S3 and dissolve them in 60 mL of deionized water as the electrolyte. The 1T-MoS2 / CC electrode obtained in step S2 is placed in an electrolytic cell filled with the N-GQDs electrolyte as the working electrode. Use an electrochemical workstation to deposit at a DC voltage of 2 V for 0.5 h. After washing, the product is vacuum-dried to obtain a 1T-MoS2 / N-GQDs / CC electrode.

[0092] Results and Analysis

[0093] Figure 1 This is the technical roadmap of the present invention. This figure details the technical route for preparing 1T-MoS2 / N-GQDs / CC electrodes.

[0094] Figure 2 The SEM images of the carbon cloth before and after acid treatment in Example 1 of the present invention are shown. Figure 2 (a) is the SEM image of carbon cloth before acid treatment. Figure 2(b) shows an SEM image of the carbon cloth after acid treatment. The image shows the smooth surface of the untreated carbon cloth. However, the acid-treated carbon cloth undergoes significant surface changes, with acid-etched grooves appearing on the surface and the surface becoming rougher. This structure improves contact between the surface and water molecules, thereby enhancing the carbon cloth's hydrophilicity.

[0095] Figure 3 This is the SEM image of the 1T-MoS2 / CC electrode in Example 1 of the present invention. Figure 3 As can be seen from (a), MoS2 grows evenly on the surface of the carbon cloth. Figure 3 (b) in the Figure 3 (a) A partial magnification of the image in the red frame. As can be seen from the image, MoS2 grows uniformly on the carbon cloth surface in the form of nanosheets and nanoflower balls, with the size of the MoS2 nanoflower balls ranging from 400 to 600 nm.

[0096] Figure 4 This is the Raman spectrum of the 1T-MoS2 / CC electrode in Example 1 of the present invention. -1 , 235cm -1 、334 cm -1 The characteristic peaks at 1345 cm correspond to the characteristic peaks of J1, J2, and J3 of 1T-MoS2. -1 and 1592 cm -1 The peaks at correspond to the D peak and G peak of the carbon cloth, respectively. Therefore, it can be proved that 1T-MoS2 is successfully grown on the carbon cloth.

[0097] Figure 5 TEM image of N-GQDs and size distribution diagram of N-GQDs in Example 1 of the present invention. Figure 5 (a) is the TEM image of N-GQDs. Figure 5 (b) is the size distribution diagram of N-GQDs. It can be seen from the figure that the prepared N-GQDs are of nanometer size with an average size of 2.52 nm.

[0098] Figure 6 This is the infrared spectrum of N-GQDs in Example 1 of the present invention. -1 and 1398 cm -1 The absorption peaks at correspond to the stretching vibration of NH and the bending vibration of CN, respectively, indicating that the prepared N-GQDs were successfully prepared.

[0099] Figure 7This is a TEM image of the 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention. The cyan mark in the figure is the small-sized N-GQDs. The calculated lattice spacing is 0.24 nm, corresponding to the (110) crystal plane of graphene. The white mark is 1T-MoS2. The calculated lattice spacing is 0.66 nm, corresponding to the (110) crystal plane of 1T-MoS2, which is extended relative to the (110) crystal plane of the 2H phase. It can be observed in the figure that N-GQDs with a size of 2~5 nm are successfully deposited on the 1T-MoS2 / CC electrode.

[0100] Figure 8 The Mo 3d fine spectra 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 are shown in FIG. Figure 8 (a) is the Mo 3d fine spectrum in the XPS spectrum of 1T-MoS2 / CC electrode. Figure 8 (b) 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 1T phase content in MoS2 is very high. According to the peak analysis, the 1T phase content is about 66%. At the same time, compared with the 1T-MoS2 / CC electrode, the Mo 3d of the 1T phase and the 2H phase of the 1T-MoS2 / N-GQDs / CC electrode is 5 / 2 、Mo 3d 3 / 2 The atomic orbitals of N-GQDs shifted towards the direction of low binding energy by 0.2 eV, which indicates that the addition of N-GQDs is beneficial to improving the chemical stability of 1T-MoS2 / CC.

[0101] Figure 9 This is a comparison chart of the 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. From the figure, it can be calculated that the mass specific capacitance of 1T-MoS2 / CC and 1T-MoS2 / N-GQDs / CC is 428 F g -1 and 917 F g -1 , the addition of N-GQDs increases the specific capacitance by 114%.

[0102] Figure 10 1T-MoS2 / CC electrode and 1T-MoS2 / N-GQDs / CC electrode in Example 1 of the present invention, wherein: Figure 10 (a) is 1T-MoS2 / CC at 20 A g -1 Cycling performance diagram under current density, Figure 10 (b) is the 1T-MoS2 / N-GQDs / CC electrode at 30 A g-1 The cycling performance diagram under current density shows 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. The addition of N-GQDs improves the cycling stability.

[0103] Figure 11 The flexible all-solid-state symmetrical supercapacitor assembled with 1T-MoS2 / N-GQDs / CC electrodes in Example 1 of the present invention has a capacitance of 20 mV s -1 Comparison of CV curves before and after bending 180° at a scan rate. The figure shows that the CV curves before and after folding are highly consistent, indicating that the device with carbon cloth as the current collector has good stability and flexibility.

[0104] Figure 12 This is a diagram of a flexible all-solid-state symmetrical supercapacitor assembled with 1T-MoS2 / N-GQDs / CC electrodes lighting up an LED in Example 1 of the present invention. Three devices connected in series can light up an LED for at least 7 minutes.

[0105] In summary, the present invention uses electrophoretic deposition to deposit small-sized N-GQDs onto the surface and between the layers of 1T-MoS2, which can reduce the accumulation of 1T-MoS2 layers and uniformly distribute the N-GQDs. This can enhance the chemical stability of 1T-MoS2, thereby improving its electrochemical storage performance and significantly enhancing the material's capacitance performance. The flexible all-solid-state symmetrical supercapacitor assembled with 1T-MoS2 / N-GQDs / CC electrodes has good application value.

[0106] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing an electrode composite material for a flexible supercapacitor, characterized in that: The following steps are involved: S1. Soak the carbon cloth in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid for 12-24 hours, wash it after soaking, and dry it for later use; S2, dissolving a molybdenum source and a sulfur source in a set molar ratio in deionized water, stirring to obtain a uniform precursor solution, placing the carbon cloth obtained in S1 into the precursor solution to react at a set temperature, and after the reaction, ultrasonically cleaning the product with ethanol and deionized water, and vacuum drying to obtain a 1T phase molybdenum disulfide flexible electrode, i.e., 1T-MoS2 / CC; S3, dissolving citric acid and ethylenediamine in a set mass ratio in deionized water, stirring, and reacting at a set temperature. After the reaction, dialyzing the product and freeze-drying it to obtain nitrogen-doped graphene quantum dots, i.e., N-GQDs; S4. Dissolve the N-GQDs obtained in step S3 in deionized water as an electrolyte, place the 1T-MoS2 / CC electrode obtained in step S2 in an electrolytic cell filled with the N-GQDs electrolyte, and deposit it under a set DC voltage. After cleaning the product, vacuum dry it to obtain a nitrogen-doped graphene quantum dot / 1T phase molybdenum disulfide flexible composite electrode, i.e., 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, characterized in that 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, wherein 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, characterized in that In step S3, the mass ratio of citric acid to ethylenediamine is 3-4:1, and the amount of citric acid added 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 of the 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 to 7.

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

10. The use according to claim 9, characterized in that The electrode composite material 1T-MoS2 / N-GQDs / CC is used as the two electrodes of the flexible supercapacitor to assemble a flexible all-solid-state symmetrical supercapacitor.

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