GB2625474A

GB2625474A - N/O co-doped molybdenum sulfide@porous carbon composite electrode material and preparation method therefor, negative electrode material and preparation method

Info

Publication number: GB2625474A
Application number: GB2404167.5A
Authority: GB
Inventors: Li Ming; Jia Wenhan
Original assignee: Guilin University of Technology
Current assignee: Guilin University of Technology
Priority date: 2021-12-09
Filing date: 2022-12-08
Publication date: 2024-06-19
Also published as: CN114156093A; GB202404167D0; WO2023104141A1; CN114156093B

Abstract

The present invention relates to the technical field of electrode materials for supercapacitors, in particular to an N/O co-doped molybdenum sulfide@porous carbon composite electrode material, and a preparation method therefor and the use thereof. In the present invention, co-doping with nitrogen and oxygen atoms and compounding with molybdenum sulfide are used; the nitrogen atoms provide more electron active sites to improve the electron transport speed of porous carbon; the oxygen atoms are oxidized/reduced to improve the pseudo-capacity of an electrode; the porous carbon provides a cross-linked porous structure with a large specific surface area; molybdenum disulfide is attached to the porous carbon to improve the synergistic effect of the porous carbon and molybdenum disulfide so as to further improve the electric conductivity; and the porous carbon and heteroatoms are subjected to doping modification and compounded with a transition metal sulfide, such that the advantages of an efficient cycling stability and a high power density of the porous carbon itself are brought into play. In addition, the material prepared in the present invention is environmentally friendly and is simple and easy to obtain, and the operation is simple and effective.

Description

N/O CO-DOPED MOLYBDENUM SULFIDEria0ROUS CARBON COMPOSITE ELECTRODE MATERIAL AND PREPARATION METHOD THEREFOR, NEGATIVE ELECTRODE MATERIAL AND PREPARATION METHOD THEREFOR, AND USE

THEREOF

[0001] The present application claims priority to the Chinese Patent Application CN202111502666.3 filed with the China National Intellectual Property Administration (CNIPA) on December 09, 2021 and entitled "N/O-CODOPED MOLYBDENUM SULF1DE@POROUS CARBON COMPOSITE ELECTRODE MATERIAL, AND PREPARATION METHOD AND USE THEREOF", which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure belongs to the technical field of supercapacitor electrode materials, and specifically relates to an N/O-codoped molybdenum sulfide@porous carbon composite electrode material and a preparation method thereof, and an anode material and a preparation method and use thereof

BACKGROUND

[0003] In recent years, conducting polymer hydrogels (CPHs) have attracted widespread scientific interest in wearable electronics (such as motion sensors, artificial skin, energy storage devices, and soft robots) due to their excellent ionic and electronic conductivities and allowable transformation. For most wearable electronics, a mechanical behavior is an indispensable aspect of fabrication of a humanized interface with a touch-screen function. Therefore, it is very important to combine flexibility, stretchability, and compressibility in the material selection and functional design for flexible electronics [0004] Chlorinated paraffin is usually composed of a hydrophilic polymer matrix and an electrically-conductive filler A large number of hydrophilic polymers, such as polyacrylic acid (PAA), polyacrylamide (PAAM), polyvinyl alcohol (PVA), cellulose, chitosan, gelatin, agarose, and dextran, can be used as supports for chlorinated paraffin to provide adjustable mechanical properties. Natural polymer products have characteristics such as low cost, excellent processability, safety, renewability, and biodegradability, and have become promising candidate materials for preparation of chlorinated paraffin of eco-friendly and renewable electronics in the future. Among various natural polymer products, sodium alginate, as a natural water-soluble anionic polysaccharide, is widely used to synthesize high-strength hydrogels under very mild conditions. In addition, hydrogels prepared from salicylic acid allow a self-healing ability through dynamic covalent bonding without additional stimulation, such that a flexible device can self-heal when damaged, which extends a life span of the flexible device.

[0005] Electrochemical capacitors have attractive characteristics such as an ultra-high power density and a long life span, and are currently considered to be the most effective energy storage and conversion devices. According to storage mechanisms, electrochemical capacitors can be divided into electrical double-layer capacitors and pseudocapacitors. The electrical double-layer capacitors have strong competitiveness in energy storage due to their high power density and excellent electrochemical stability. The capacitance performance of an electrical double-layer capacitor mainly depends on properties of an electrode material, such as specific surface area, pore size distribution, and surface chemical properties. So far, a variety of carbon-based electrode materials, including graphene, carbon nanotubes, carbon fibers, and porous carbon, have been widely used to fabricate electric double-layer capacitors due to their unique properties such as high specific surface area, adjustable pore structure, easy functionalization, and low production cost.

[0006] Although a significant progress has been made in improving the capacitance of carbon materials, insufficient rate capacities and low energy densities of carbon materials still hinder the application of carbon materials in fabrication of advanced supercapacitors.

SUMMARY

[0007] In view of the deficiencies of the prior art, the present disclosure provides an N/O-codoped molybdenum sulfide@porous carbon composite electrode material, and a preparation method and use thereof In the present disclosure, nitrogen/oxygen atom co-doping and porous carbon/molybdenum sulfide compounding are used. Nitrogen atoms provide increased electron active sites to improve an electron transport speed of porous carbon. Oxygen atoms improve a pseudocapacity of an electrode through oxidation/reduction. Porous carbon provides a crosslinked porous structure with a large specific surface area. Molybdenum disulfide adheres to the porous carbon to improve a synergistic effect of the molybdenum disulfide and porous carbon, thereby further improving the conductivity. After being doped with heteroatoms for modification and compounded with a transition metal sulfide, porous carbon can give full play to its advantages such as efficient cycle stability and huge power density. In addition, the material prepared in the present disclosure is eco-friendly and easy to prepare, and the preparation method involves simple and effective operations.

[0008] In order to achieve the above object, the present disclosure provides the following technical solutions: [0009] The present disclosure provides a method for preparing an N/0-codoped molybdenum sulfide@porous carbon composite electrode material, including the following steps: [0010] (1) ultrasonically dispersing a molybdate and a sulfur source in deionized water to obtain a dispersed solution, subjecting the dispersed solution to solvothermal reaction to obtain a reacted product, and washing and drying the reacted product to obtain molybdenum disulfide, [0011] where a molar ratio of the molybdate to the sulfur source is in a range of 1:(2-4); [0012] (2) mixing a carbon source and a nitrogen source to be uniform, adding the molybdenum disulfide obtained in step (1), thoroughly mixing to obtain a homogeneous solution, and subjecting the homogeneous solution to residual bubble removal through an ultrasonic treatment to obtain a mixed solution, [0013] where a mass ratio of the carbon source to the nitrogen source is in a range of 1:(2-3) and a mass ratio of the carbon source to the molybdenum disulfide is 1:1; [0014] (3) completely evaporating a solvent of the mixed solution obtained in step (2) through freeze-drying to obtain a carbon source/MoS2 aerogel; and [0015] (4) in a nitrogen atmosphere, heating the carbon sourceaVIoS2 aerogel obtained in step (3) at a temperature of 500 °C to 600 °C for 2 h to 3 h with a heating rate of 3 °C/min to 5 °C/min to obtain a heated aerogel, further carbonizing the heated aerogel at a temperature of 800 °C for 1 h to obtain a carbonized product, cooling the carbonized product to room temperature to obtain a cooled product, and washing and vacuum-drying the cooled product to obtain the N/O-codoped molybdenum sulfidekbporous carbon composite electrode material.

[0016] In some embodiments, in step (1), the molybdate is one selected from the group consisting of sodium molybdate, potassium molybdate, and ammonium molybdate tetrahydrate.

[0017] In some embodiments, in step (1), the sulfur source is one selected from the group consisting of thiourea, L-cysteine, and thioacetamide.

[0018] In some embodiments, in step (1), the solvothermal reaction is conducted in a reactor; a volume of the deionized water is 60% of a volume of a polytetrafluoroethylene (PTFE) liner in the reactor; and the solvothermal reaction is conducted at a temperature of 190 °C to 220°C for 20 h to 36 h. [0019] In some embodiments, in step (2), the carbon source is one selected from the group consisting of sodium alginate, potassium alginate, and lignin.

[0020] In some embodiments, in step (2), the nitrogen source is one selected from the group consisting of urea, tripolycyanamide, and ammonia water.

[0021] The present disclosure also provides an N/O-codoped molybdenum sulfide@porous carbon composite electrode material prepared by the method described above.

[0022] The present disclosure also provides an anode material prepared with the N/O-codoped molybdenum sulfide@porous carbon composite electrode material described above.

[0023] The present disclosure also provides a method for preparing the anode material, including the following steps: [0024] mixing the N/O-codoped molybdenum sulfide@porous carbon composite electrode material, conductive acetylene black, and polyvinylidene fluoride, adding N-methylpyrrolidone, and grinding a resulting mixture to obtain a homogeneous black slurry; and evenly laying the homogeneous black slurry on a nickel foam to obtain a laid nickel foam, and drying and pressing the laid nickel foam to obtain the anode material, [0025] where a mass ratio of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material, the conductive acetylene black, and the polyvinylidene fluoride is in a range of (0.75-0.85):(0.1-0.15): (0.1-0.15).

[0026] The present disclosure also provides use of the anode material described above in preparation of a supercapacitor anode material.

[0027] Compared with the prior art, the present disclosure has the following beneficial effects: [0028] 1. The present disclosure provides a simple, eco-friendly, and effective method for preparing an N/O-codoped molybdenum sulfide@porous carbon composite electrode material. In the method of the present disclosure, a small-molecule nitrogen source is uniformly dispersed in a carbon source through freeze-drying, and the carbon source and molybdenum sulfide are thoroughly mixed under mechanical stirring. The nitrogen source serves as both a nitrogen source and a pore-forming agent during carbonization. The method of the present disclosure has the following advantages: The raw materials are abundant, and a price-quality ratio is high. A pyrolysis process does not require any other activating agents such as KOH and ZnC12, and only requires one-step carbonization to achieve pore reforming and nitrogen doping. In addition, a porous structure and a nitrogen content of the material can be adjusted by adjusting an amount of the nitrogen source and a temperature of the carbonization.

[0029] 2. In the present disclosure, nitrogen/oxygen atom co-doping and porous carbon/molybdenum sulfide compounding are used. Nitrogen atoms provide increased electron active sites to improve an electron transport speed of porous carbon. Oxygen atoms improve a pseudocapacity of an electrode through oxidation/reduction. Porous carbon provides a crosslinked porous structure with a large specific surface area. Molybdenum disulfide adheres to porous carbon to improve a synergistic effect of the molybdenum disulfide and porous carbon, thereby further improving the conductivity. After being doped with heteroatoms for modification and compounded with a transition metal sulfide, porous carbon can give full play to its advantages such as efficient cycle stability and huge power density.

[0030] 3. The doped elements of the present disclosure do not affect the performance of the material itself, and further have a significant improvement effect for the performance of the entire supercapacitor. In addition, the preparation method of the present disclosure is simple, has a low preparation cost, and results in a material that can be well degraded in the nature, which is eco-friendly.

[0031] 4. In the present disclosure, a heteroatom doping technique is used. On the one hand, a hierarchical porous structure has a unique property of rapid ion diffusion and transport, which is conducive to enhancing the rate capability and improving the cycling life. On the other hand, the heteroatom doping can adjust the electronic and chemical properties of porous carbon, which is conducive to increasing the capacity through a faradaic reaction. Therefore, heteroatom-doped hierarchical porous carbon will show excellent electrochemical performance. Nitrogen atoms are considered to be the most promising candidate due to their abundant nitrogen source and excellent functionality. Because nitrogen atoms introduced into a carbon framework can produce structural defects, acid/alkali properties are imparted, and available active sites are increased.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows a flow chart of preparation of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material (MoS2-SA/C) according to Example 1 of the present disclosure.

[0033] FIG. 2 shows scanning electron microscopy (SEM) images of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material (M0S2-SA/C) prepared according to Example 1 of the present disclosure.

[0034] FIG. 3 shows the comparison of X-ray d ffractometry (XRD) patterns of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material (M0S2-SA/C) prepared according to Example I and the N/O-codoped porous carbon composite electrode material (SA/C) prepared according to Comparative Example 1 of the present disclosure [0035] FIG. 4 shows the comparison of Raman spectra of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material (MoS2-SA/C) prepared according to Example 1 and the N/O-codoped porous carbon composite electrode material (SA/C) prepared according to Comparative Example I of the present disclosure.

[0036] FIG. 5 shows the comparison of cyclic voltammetry curves of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material (MoS2-SAJC) prepared according to Example 1, the N/O-codoped porous carbon composite electrode material (SAJC) prepared according to Comparative Example I, and the molybdenum disulfide (M0S2) prepared according to Comparative Example 2 of the present disclosure.

[0037] FIG. 6 shows the comparison of cyclic voltammetry curves of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material (MoS2-SA/C) prepared according to Example I of the present disclosure at different scanning speeds.

[0038] FIG. 7 shows charge-discharge curves of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material (MoS2-SA/C) prepared according to Example 1 of the present disclosure.

[0039] FIG. 8 shows an impedance curve of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material (MoS2-SA/C) prepared according to Example 1 of the present disclosure.

[0040] FIG. 9 shows the cycling efficiency of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material (M0S2-SAJC) prepared according to Example 1 of the present di sclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] Specific examples of the present disclosure are described in detail below, but it should be understood that the scope of the present disclosure is not limited by the specific examples. All other examples obtained by a person of ordinary skill in the art based on the examples of the present disclosure without creative efforts shall fall within the scope of the present disclosure. Unless otherwise specified, all experimental methods used in the examples of the present disclosure are conventional methods.

[0042] Unless otherwise specified, the following experimental methods and test methods are conventional methods. Unless otherwise specified, the following reagents and raw materials are commercially available.

[0043] Example I

[0044] Provided was a method for preparing an N/O-codoped molybdenum sulfide@porous carbon composite electrode material, which consisted of the following steps: [0045] (1) 0.242 g of sodium molybdate (1 mmol) and 0.228 g of thiourea (3 mmol) were taken and added into a PTFE inner sleeve with a volume of 100 mL, deionized water was added in a volume of 60% of a total volume of the PTFE inner sleeve, and a resulting mixture was mixed to be uniform by an ultrasonic treatment at 100 W for 10 min. The PTFE inner sleeve was placed in a stainless steel outer sleeve, and the stainless steel outer sleeve was sealed and kept at 200 °C for 24 h. A resulting product was repeatedly washed 3 times with ethanol and deionized water to obtain a black substance, and then the black substance was dried overnight in a vacuum-drying oven at 80 °C to obtain molybdenum disulfide.

[0046] (2) 3 g of sodium alginate and I g of urea were dispersed in water, and a resulting dispersion system was mechanically stirred at a high speed (300 rpm/12 h) to make the sodium alginate evenly dispersed to obtain a sodium alginate solution. Then the molybdenum disulfide obtained in step (1) was added into the sodium alginate solution and stirred for 1 h to obtain a homogeneous system, such that the molybdenum disulfide was fully mixed with the sodium alginate solution and a color of the homogeneous system turned from light-yellow to black. Then the homogeneous system was subjected to an ultrasonic treatment in an ultrasonic device for 30 min at a power of 100W to fully remove residual bubbles to obtain a mixed solution.

[0047] (3) The mixed solution obtained in step (2) was freeze-dried in a freeze dryer at -60 °C for 48 h to obtain an SA/MoS2 aerogel.

[0048] (4) In a nitrogen atmosphere, the SA/MoS2 aerogel obtained in step (3) was first heated at 550 °C for 2 h with a heating rate of 5 °C/min, then carbonized at 800 °C for 1 h, and cooled to room temperature to obtain a black powder. The black powder was washed multiple times with ethanol and deionized water and then vacuum-dried at 80 °C for 24 h, obtaining the N/O-codoped molybdenum sulfide@porous carbon composite electrode material (which was denoted as M0S2-SA/C).

[0049] Example 2

[0050] Provided was a method for preparing an N/0-codoped molybdenum sulfide@porous carbon composite electrode material, which consisted of the following steps: [0051] (1) 0.238 g of potassium molybdate (1 mmol) and 0.3 g of L-cysteine (2.5 mmol) were taken and added into a PTFE inner sleeve with a volume of 100 mL, deionized water was added in a volume of 60% of a total volume of the PTFE inner sleeve, and a resulting mixture was mixed to be uniform by an ultrasonic treatment at 100 W for 10 min. The PTFE inner sleeve was placed in a stainless steel outer sleeve, and the stainless steel outer sleeve was sealed and kept at 190 °C for 36 h. A resulting product was repeatedly washed 3 times with ethanol and deionized water to obtain a black substance, and then the black substance was dried overnight in a vacuum-drying oven at 80 °C to obtain molybdenum disulfide.

[0052] (2) 1 g of potassium alginate and 2.5 g of tripolycyanamide were dispersed in water, and a resulting dispersion system was mechanically stirred at a high speed (300 rpm/12 h) to make the potassium alginate evenly dispersed to obtain a potassium alginate solution. Then the molybdenum disulfide obtained in step (1) was added into the potassium alginate solution and stirred for 1 h to obtain a homogeneous system, such that the molybdenum disulfide was fully mixed with the potassium alginate solution and a color of the homogeneous system turned from light-yellow to black. Then the homogeneous system was subjected to an ultrasonic treatment in an ultrasonic device for 30 min at a power of 100W to fully remove residual bubbles to obtain a mixed solution. [0053] (3) The mixed solution obtained in step (2) was freeze-dried in a freeze dryer at -60 °C for 36 h to obtain a potassium alginate/MoS2 aerogel.

[0054] (4) In a nitrogen atmosphere, the potassium alginate/MoS2 aerogel obtained in step (3) was first heated at 500 °C for 3 h with a heating rate of 5 °C/min, then carbonized at 800 °C for 1 h, and cooled to room temperature to obtain a black powder. The black powder was washed multiple times with ethanol and deionized water and then vacuum-dried at 80 °C for 24 h, obtaining the N/O-codoped molybdenum sulfide@porous carbon composite electrode material.

[0055] Example 3

[0056] Provided was a method for preparing an N/O-codoped molybdenum sulfide@porous carbon composite electrode material, which consisted of the following steps: [0057] (1) 12368 of ammonium molybdate tetrahydrate (1 mmol) and 0.225 g of thioacetamide (3 mmol) were taken and added into a PTFE inner sleeve with a volume of 100 mL, deionized water was added in a volume of 60% of a total volume of the PTFE inner sleeve, and a resulting mixture was mixed to be uniform by an ultrasonic treatment at 100 W for 10 min. The PTFE inner sleeve was placed in a stainless steel outer sleeve, and the stainless steel outer sleeve was sealed and kept at 220 °C for 20 h. A resulting product was repeatedly washed 3 times with ethanol and deionized water to obtain a black substance, and then the black substance was dried overnight in a vacuum-drying oven at 80 °C to obtain molybdenum disulfide.

[0058] (2) 1 g of lignin and 2 g of tripolycyanamide were dispersed in water, and a resulting dispersion system was mechanically stirred at a high speed (300 rpm/12 h) to make the lignin evenly dispersed to obtain a lignin solution. Then the molybdenum disulfide obtained in step (1) was added to the lignin solution and stirred for 1 h to obtain a homogeneous system, such that the molybdenum disulfide was fully mixed with the lignin solution and a color of the homogeneous system turned from light-yellow to black to obtain a homogeneous system. Then the homogeneous system was subjected to an ultrasonic treatment in an ultrasonic device for 30 min at a power of 100 W to fully remove residual bubbles to obtain a mixed solution.

[0059] (3) The mixed solution obtained in step (2) was freeze-dried in a freeze dryer at -60 °C for 24 h to obtain a lignin/MoS2 aerogel.

[0060] (4) In a nitrogen atmosphere, the lignin/MoS2 aerogel obtained in step (3) was first heated at 600 °C for 2 h with a heating rate of 5 °C/min, then carbonized at 800 °C for 1 h, and cooled to room temperature to obtain a black powder. The black powder was washed multiple times with ethanol and deionized water and then vacuum-dried at 80 °C for 24 h, obtaining the N/O-codoped molybdenum sulfideZporous carbon composite electrode material.

[0061] Comparative Example 1 [0062] Provided was a method for preparing an N/O-codoped porous carbon composite electrode material, which consisted of the following steps: [0063] (1) 3 g of sodium alginate and 1 g of urea were dispersed in water, and a resulting dispersion system was mechanically stirred at a high speed (300 rpm/12 h) to make the sodium alginate evenly dispersed to obtain a sodium alginate solution. Then the sodium alginate solution was subjected to an ultrasonic treatment in an ultrasonic device for 30 min at a power of 100W to fully remove residual bubbles to obtain a mixed solution.

[0064] (3) The mixed solution obtained in step (2) was freeze-dried in a freeze dryer at -60 °C for 48 h to obtain an SA aerogel.

[0065] (4) In a nitrogen atmosphere, the SA aerogel obtained in step (3) was first heated at 550 °C for 2 h with a heating rate of 5 °C/min, then carbonized at 800 °C for 1 h, and cooled to room temperature to obtain a black powder. The black powder was washed multiple times with ethanol and deionized water and then vacuum-dried at 80 °C for 24 h, obtaining the N/O-codoped porous carbon composite electrode material (which was denoted as SA/C).

[0066] Comparative Example 2 [0067] Molybdenum disulfide (which was denoted as MoS2) was prepared according to step (1) of Example 1.

[0068] Results and discussion: [0069] The N/O-codoped molybdenum sulfide@porous carbon composite electrode materials prepared according to Examples 1 to 3 of the present disclosure each were subjected to performance evaluation. The N/O-codoped molybdenum sulfide@porous carbon composite electrode material prepared according to Example 1 was taken as an example to prepare an anode material, and then the anode material was used to construct a three-electrode system. This example was compared with the comparative examples.

[0070] Preparation of the anode material: The N/O-codoped molybdenum sulfide@porous carbon composite electrode material prepared according to Example I, conductive acetylene black, and polyvinylidene fluoride were mixed, N-methylpyrrolidone was added thereto, and a resulting mixture was ground to obtain a homogeneous black slurry. The homogeneous black slurry was evenly layed on a nickel foam, and a resulting laied nickel foam was dried and pressed to obtain the anode material, where a mass ratio of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material, the conductive acetylene black, and the polyvinylidene fluoride was 8:1:1.

[0071] The SA/C according to Comparative Example 1 and the MoS2 according to Comparative Example 2 were used to prepare anode materials by the same method as above.

[0072] A specific composition of a three-electrode system was as follows A CH1760E electrochemical workstation (CH1760E) was used to assemble the three-electrode system with a platinum (Pt) foil as a counter electrode, an Hg/Hg2C12 electrode as a reference electrode, and each of the electrode materials according to Example 1, Comparative Example 1, and Comparative Example 2 as a working electrode, and the electrochemical performance was tested with a 1 mol/L Na2SO4 solution as an electrolyte.

[0073] It can be seen from the electron microscopy images in FIG. 2 that the material as a whole presents a porous layered arrangement, and individual pore structures can be clearly seen under a 500 nm electron microscope, indicating that a layered porous carbon morphology with a 3D structure is successfully synthesized after carbonizing the material, which provides a large specific surface area and a broad electron transport channel.

[0074] It can be seen from the XRD patterns in FIG. 3 that the synthesized material not only retains crystal forms (002), (100), and (200) of molybdenum disulfide, but also has an XRD peak of C after carbonization, indicating that molybdenum disulfide is well retained under high-temperature carbonization. In addition, after the compounding of molybdenum disulfide, a crystal form of the material is smoothed, indicating that the compounding of molybdenum disulfide with sodium alginate can improve the crystallinity of the composite material obtained after the carbonization.

[0075] The results in FIG. 4 show that Aig and E2g energy levels can be observed at MoS2, which reflect out-plane and in-plane vibration moduli, respectively; and two distinct peaks appear at 1,336 cm-' and 1,588 cm-' in a Raman spectrum of porous carbon, which belong to D and G bands, respectively, where the former represents a structural defect, and the latter represents an in-phase vibration of sp2 hybridized carbon. An ID/Ici value can be used to describe a graphite disordering degree of the material. In addition, ID/I6 ratios of SA-C and MoS2-SA/C are 0.964 and 1.08, respectively. A high ID/IG value indicates a low graphitization degree and abundant disordered structures and defects of a sample, which are caused by N-0 codoping. These abundant defects can provide high pseudocapacitance to obtain excellent capacitance performance.

[0076] FIG. 5 shows cyclic voltammetry curves of the materials according to Example 1 and Comparative Examples 1 arid 2 at 10 mV.m-1. It can be seen that a capacity of molybdenum disulfide or SA/C alone is significantly different from a capacity of a composite of the two, indicating that the composite is not simply a sum of the two, but the two play an excellent synergistic effect.

[0077] The results in FIG. 6 show that the material can maintain the properties of the original double-layer capacitance under an increasing scanning rate, indicating that the material has excellent cycling performance.

[0078] The results in FIG. 7 show that the material has a high-area specific capacitance of 1.8 F/cm-2 at a current of 1 mA.cm-2, indicating that the material with N/O codoping and molybdenum disulfide has a very significant capacitance advantage.

[0079] The results in FIG. 8 show that an Rs value of the material is 2.6. The small resistance value of the material indicates that the material has small resistance and an excellent electron migration capacity in the case of electron transport, which also confirms the porous structure observed under an electron microscope and indicates that the structure can indeed optimize the electrochemical performance.

[0080] The cycling test results in FIG. 9 show that after 5,000 cycles at a current density of 10 mA*cm', a capacity retention rate of the material is 97%, indicating that the material has excellent crystallinity and excellent cycling stability as a flexible application material. The high current also indicates high-speed ion transport and excellent rate performance of the material. A shape of a cyclic galvanostatic charge-discharge (GCD) curve for each cycle among the first four cycles and the last four cycles of the material remains basically unchanged after 5,000 cycles, indicating excellent cycling performance of the electrode material.

[0081] Obviously, those skilled in the art can make various alterations and modifications to the present disclosure without departing from the spirit and scope of the present disclosure. Thus, provided that these alterations and modifications of the present disclosure fall within the scope of the claims of the present disclosure and their equivalents, the present disclosure is also intended to include these alterations and modifications.

Claims

WHAT IS CLAIMED IS: 1. A method for preparing an N/O-codoped molybdenum sulfideaporous carbon composite electrode material, wherein the method comprises the following steps: (1) ultrasonically dispersing a molybdate and a sulfur source in deionized water to obtain a dispersed solution, subjecting the dispersed solution to solvothennal reaction to obtain a reacted product, and washing and drying the reacted product to obtain molybdenum disulfide, wherein a molar ratio of the molybdate to the sulfur source is in a range of 1:(2-4) (2) mixing a carbon source and a nitrogen source to be uniform, adding the molybdenum disulfide obtained in step (1), thoroughly mixing to obtain a homogeneous solution, and subjecting the homogeneous solution to residual bubble removal to obtain a mixed solution, wherein a mass ratio of the carbon source to the nitrogen source is in a range of 1:(2-3), and a mass ratio of the carbon source to the molybdenum disulfide is 1:1; (3) completely evaporating a solvent of the mixed solution obtained in step (2) to obtain a carbon source/MoS2 aerogel; and (4) in a nitrogen atmosphere, heating the carbon source/MoS2 aerogel obtained in step (3) at a temperature of 500 °C to 600 °C for 2 h to 3 h with a heating rate of 3 °C/min to 5 °C/min to obtain a heated aerogel, further carbonizing the heated aerogel at a temperature of 800 °C for 1 h to obtain a carbonized product, cooling the carbonized product to room temperature to obtain a cooled product, and washing and vacuum-drying the cooled product to obtain the N/O-codoped molybdenum sulfideOporous carbon composite electrode material.
2. The method of claim 1, wherein in step (1), the molybdate is one selected from the group consisting of sodium molybdate, potassium molybdate, and ammonium molybdate tetrahydrate.
3 The method of claim 1, wherein in step (1), the sulfur source is one selected from the group consisting of thiourea, L-cysteine, and thioacetamide
4. The method of claim 1, wherein in step (1), the solvothermal reaction is conducted in a reactor, a volume of the deionized water is 60% of a volume of a polytetrafluoroethylene (PTFE) liner in the reactor; and the solvothermal reaction is conducted at a temperature of 190 °C to 220 °C for 20 h to 36 h.
5. The method of claim 1, wherein in step (1), the ultrasonically dispersing is conducted for 10 min at a power of 100 W.
6. The method of claim 1, wherein in step (2), the carbon source is one selected from the group consisting of sodium alginate, potassium alginate, and lignin.
7. The method of claim 1, wherein in step (2), the nitrogen source is one selected from the group consisting of urea, tripolycyanamide, and ammonia water.
8. The method of claim 1, wherein in step (2), the mixing the carbon source and the nitrogen source is conducted by dispersing the carbon source and the nitrogen source in water, and mechanically stirring a resulting dispersion system, wherein the mechanical stirring is conducted at a rotate speed of 300 rpm for 12 h
9. The method of claim 1 or 8, wherein the subjecting the homogeneous solution to residual bubble removal is conducted by subjecting the homogeneous solution to an ultrasonic treatment in an ultrasonic device for 30 min at a power of 100W.
10. The method of claim 1, wherein in step (3), the solvent Is completely evaporated through freeze-drying; and the freeze-drying is conducted at -60 °C for 24 h, 36 h, or 48 h.
11 An N/O-codoped molybdenum sulfide@porous carbon composite electrode material prepared by the method of any one of claims 1 to 10
12. An anode material prepared with the N/O-codoped molybdenum sulfide@porous carbon composite electrode material of claim 11
13 A method for preparing the anode material of claim 12, wherein the method comprises the following steps: mixing the N/O-codoped molybdenum sulfide@porous carbon composite electrode material, conductive acetylene black, and polyvinylidene fluoride, adding N-methylpyrrolidone, and grinding a resulting mixture to obtain a homogeneous black slurry; and evenly laying the homogeneous black slurry on a nickel foam to obtain a laid nickel foam, and drying and pressing the laid nickel foam to obtain the anode material, wherein a mass ratio of the N/O-codoped molybdenum sulfide@porous carbon composite electrode material, the conductive acetylene black, and the polyvinylidene fluoride is in a range of (0.75-0.85):(0.1-0.15):(0.1-0.15).
14. Use of the anode material of claim 12 or an anode material prepared by the method of claim 13 in preparation of a supercapacitor anode material.