CN111106318A

CN111106318A - Nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material

Info

Publication number: CN111106318A
Application number: CN201811262164.6A
Authority: CN
Inventors: 郭金; 廖莎; 张会成; 王少军; 凌凤香
Original assignee: China Petroleum and Chemical Corp; Sinopec Dalian Research Institute of Petroleum and Petrochemicals
Current assignee: Sinopec Dalian Petrochemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2018-10-27
Filing date: 2018-10-27
Publication date: 2020-05-05
Anticipated expiration: 2038-10-27
Also published as: CN111106318B

Abstract

A nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material is prepared by using formaldehyde as a bridge, enabling the formaldehyde to be appropriately crosslinked with melamine to form a nitrogen-doped precursor, carrying out hydrothermal reaction to enable the nitrogen-doped precursor, an active component precursor and a carbon nanotube to be mutually and uniformly fused, and carrying out solvent-free microwave reaction to synthesize the high-nitrogen-content doped molybdenum disulfide/C/carbon nanotube composite material. The composite material avoids the loss caused by sublimation of the nitrogen-doped precursor in the heating process in the traditional nitrogen doping process, improves the nitrogen doping efficiency, and realizes the uniform fusion of the interaction of the nitrogen-doped precursor, the active component precursor and the carbon nano tube, wherein the reaction conditions are gradually increased from mild to strong. The prepared nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material has good stability, is not easy to denature in air, is easy to store, has a large specific surface area, is used as a lithium ion battery cathode material, provides a good channel for lithium ion transmission, and shows a large specific capacity and a good cycling stability performance.

Description

Nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material

Technical Field

The invention relates to a nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material, in particular to a high-nitrogen-content doped molybdenum disulfide/C/carbon nanotube lithium battery cathode material and a preparation method thereof, belonging to the technical field of a nano composite material and application thereof.

Background

The carbon nanotube is a hollow cylinder formed by rolling graphite layers, and the bonding mode of the carbon nanotube is mainly a deformed Sp2 orbit. When the graphite layer is rolled into the carbon nanotube, partial deformation of Sp2 hybridization occurs, so Sp2 tends to form re-hybridization of Sp3, and the re-hybridization structure and the two-orbital confinement characteristics can endow the carbon nanotube with excellent force, heat, electricity, light, magnetism and chemical properties. Therefore, the carbon nanotube has higher mechanical strength, better electric heat conduction performance and higher chemical and biological activity than graphene.

With the development of Carbon Nanotubes (CNTs) and carbon nanotubes doped with different elements, carbon tubes have attracted attention because of their unique structures and their excellent properties, and when doped with different elements, the structures of six rings of carbon nanotubes are changed to some extent so that their properties are changed or improved. Carbon nanotube materials have wide applications in electronic and optical devices, electrochemistry, thermal conduction, and the like. The high electron cloud density of the nitrogen atoms doped in the carbon nanotube crystal lattice also leads the carbon nanotube to have unique performance in the aspects of electrons, materials and electrochemistry, and creates good conditions for improving the electron transmission and the mass transmission of the CNT material. The nitrogen doping of the carbon nano tube plays a key role in promoting and expanding the application field of the carbon nano tube.However, most methods for preparing nitrogen-doped carbon nanotubes utilize chemical vapor deposition technology, and because the reaction time and the reaction degree are difficult to control, impurity elements exist in the obtained product. In addition, nitrogen-doped carbon nanotube materials with various advantages are rarely combined with amorphous carbon-modified MoS with good stability and high specific capacity by a simple and practical method₂The material is compounded and applied to the lithium ion battery cathode material.

CN 104176724B provides a preparation method of a nitrogen-doped carbon nanotube, which comprises the steps of firstly, uniformly mixing oxalic acid, water and metal salt to obtain a first mixed solution, then, mixing the obtained first mixed solution with melamine to obtain a second mixed solution, then, refluxing to obtain a suspension of a compound of melamine oxalate and metal oxalate, finally, carrying out suction filtration, washing and drying to obtain a precursor compound, then, carrying out calcination treatment at 600-900 ℃ under a nitrogen atmosphere to obtain a primary product, and finally, removing metal impurities introduced in the preparation process through acid treatment to obtain the nitrogen-doped carbon nanotube.

CN 106328387A provides a nitrogen-doped carbon nanotube/molybdenum disulfide nanoparticle composite material and a preparation method thereof. (1) Weighing Carbon Nanotubes (CNTs) and Sodium Dodecyl Benzene Sulfonate (SDBS), adding into deionized water, continuously performing magnetic stirring, performing ultrasonic treatment, adding urea, stirring with a magnetic stirrer, drying the prepared solution, and uniformly mixing the dried powder by grinding. Then calcining at 550 ℃ for 4 hours, and then heating to 900 ℃ for calcining for 2 hours to obtain the nitrogen-doped carbon nanotube. Then the obtained carbon nano tube reacts with potassium thiocyanate and molybdenum trioxide in a high-pressure hydrothermal kettle for 24 hours, and finally the nitrogen-doped MoS is obtained through cooling, washing and drying₂A carbon nanotube composite material.

However, these methods generally have many steps, long time consumption, difficult control of reaction time and degree, low nitrogen doping efficiency and easy introduction of impurity elements. Leading to difficulty in preparing high nitrogen content doped molybdenum disulfide/C/carbon nanotube materials, thereby limiting the wide application of such materials.

Disclosure of Invention

The invention provides a method for efficiently, quickly and massively synthesizing a high-nitrogen-content doped molybdenum disulfide/C/carbon nanotube composite material, which has the advantages of high nitrogen content of the obtained material, obviously improved raw material utilization rate, no need of washing, separating, drying and other processes of the product, direct application to a lithium battery cathode material and good application performance.

In order to achieve the technical purpose, the invention provides a preparation method of a nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material, which comprises the following steps:

(1) dispersing the acidified carbon nano tube in a formaldehyde aqueous solution to obtain a dispersion liquid A;

(2) mixing molybdenum salt and ammonia water, heating to 40-70 ℃, adding ammonium sulfide, reacting for 0.5-2h, sequentially adding quaternary ammonium salt and melamine into reaction liquid, and enabling the reaction liquid to become turbid to form melamine/alkylated thiomolybdate suspension, namely dispersion liquid B;

(3) mixing the dispersion liquid A and the dispersion liquid B, heating to 50-80 ℃ for reaction for 10-60min, adjusting the pH of the reaction liquid to 7-9, heating in a sealed environment to 100-200 ℃ for hydrothermal reaction for 12-24 h, and drying the product to obtain a solid material;

(4) and (4) placing the solid material obtained in the step (3) in a microwave reaction cavity, and heating for 10-60min at the microwave power of 300-1200W to obtain the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material.

In the above-mentioned production method, the concentration of the aqueous formaldehyde solution in the step (1) is not particularly limited, and in a preferred embodiment of the present invention, the concentration of formaldehyde is 37% to 40% by mass. Mixing the acidified carbon nano tube with formaldehyde aqueous solution according to the solid-to-liquid ratio of 1g (10-100) mL. The obtained solution is preferably mixed and dispersed uniformly in an ultrasonic mode, and the ultrasonic time is 5-30 min.

In the above preparation method, it should be understood by those skilled in the art that the acidified carbon nanotube is obtained by acidifying and modifying a carbon nanotube with a strong acid, and the acidifying and modifying of the carbon nanotube are well known to those skilled in the art, so long as the purpose of changing the kind and concentration of the functional group on the surface of the carbon nanotube to improve the water solubility thereof can be achieved, thereby satisfying the requirements of the present invention for the acidified carbon nanotube. For example, the carbon nanotubes are subjected to an acidification modification treatment with mixed acids (concentrated sulfuric acid and concentrated nitric acid, concentrated nitric acid and concentrated hydrochloric acid).

Among them, as a more specific embodiment, carbon nanotubes having the following properties are preferable in the selection of materials: diameter of 10-300nm, length of 2-30 μm, and specific surface area>100m²Per g, conductivity>100s/cm。

In the preparation method, the molybdenum salt is ammonium paramolybdate and/or sodium molybdate.

In the above preparation method, the quaternary ammonium salt is an ammonium halide having 4 to 30 carbons, preferably an ammonium halide having 4 to 25 carbons, and more specifically, the quaternary ammonium salt is at least one selected from the group consisting of tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride and octadecyltrimethylammonium bromide.

In the preparation method, the mixing mass ratio of the molybdenum salt, the ammonium sulfide, the quaternary ammonium salt and the melamine in the step (2) is 1:1-20:0.1-5: 0.5-5.

In the above production method, the dispersion liquid a and the dispersion liquid B are mixed in the step (3), and the dispersion liquid a is preferably poured into the dispersion liquid B. The dispersion liquid A and the dispersion liquid B are mixed according to the weight ratio of the acidified carbon nanotubes in the dispersion liquid A to the melamine in the dispersion liquid B of 1: 5-10. After mixing, the mixture is preferably mixed and dispersed uniformly in an ultrasonic mode, and the ultrasonic time is 5-30 min.

In the above preparation method, the pH of the reaction solution in the step (3) may be adjusted by using an organic base or an inorganic base, and as a more specific embodiment, the pH is selected from one or more of triethanolamine, methylamine, ethylamine, ethylenediamine, propylamine, isopropylamine, aniline, cyclohexylamine, o-aminophenol, 2-chlorophenol, potassium carbonate, sodium bicarbonate, potassium hydroxide, and sodium hydroxide.

In the preparation method, the hydrothermal reaction temperature in the step (3) is preferably 120-160 ℃, and the time is preferably 12-18 h.

In the preparation method, the power of the microwave reaction in the step (4) is preferably 600-1000W, and the time is preferably 10-30 min.

In the preparation method, the microwave reaction cavity is purged by nitrogen or inert gas before and during the microwave reaction, and preferably, argon is used for purging.

The technical purpose of the second aspect of the invention is to provide the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material prepared by the method. In the preparation process of the method, formaldehyde and melamine are mixed firstly to generate moderate crosslinking reaction to form water-soluble nitrogen-doped precursor, and then hydrothermal reaction is carried out to carry out nitrogen doping on the carbon nano tube, so that the nitrogen-doped precursor and the carbon nano tube are easy to interact, conditions are created for uniformly fusing the composite material, and the nitrogen-doped process and MoS are more favorably realized₂Compounding with carbon nanotube; the subsequent microwave reaction has high heating speed and uniform heating, the nitrogen-doped precursor is heated and decomposed, and the carbon nano tube, the nitrogen-doped precursor and the active component are uniformly fused together in the previous preparation process, so that the nitrogen doping of the carbon nano tube and the dispersion of the active component are more uniform, and the synthesis of the high-content nitrogen-doped molybdenum disulfide/C/carbon nano tube composite material is facilitated.

The technical purpose of the third aspect of the invention is to provide application of the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material, wherein the material can be used as a lithium ion battery cathode material and shows good cycle stability and rate capability.

Compared with the prior art, the invention has the following advantages:

(1) according to the invention, formaldehyde is used as a bridge in the preparation process of the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material, so that the formaldehyde and melamine are subjected to moderate crosslinking to form the nitrogen-doped precursor, and the problem of low nitrogen doping efficiency caused by large loss of the nitrogen-doped precursor due to strong sublimation of the nitrogen-doped precursor in the heating process in the traditional nitrogen fixation and fixation doping reaction is avoided.

(2) In the preparation process, the formaldehyde and the melamine are subjected to a cross-linking reaction to form a water-soluble nitrogen-doped precursor, and the nitrogen-doped precursor is uniformly coated on the carbon nanotube framework, so that the nitrogen-doped precursor, the active component precursor and the carbon nanotube are interacted and uniformly fused in the subsequent hydrothermal reaction, and the preparation of the high-nitrogen-content doped material is realized.

(3) In the microwave reaction stage in the preparation process, the heating speed is high, the heating is uniform, on one hand, the loss caused by sublimation of the nitrogen-doped precursor due to slow temperature rise in the traditional reaction can be avoided, on the other hand, the nitrogen-doped precursor is heated and decomposed under the microwave condition, and as the carbon nano tube, the nitrogen-doped precursor and the active component precursor are uniformly fused in the hydrothermal reaction stage, the nitrogen doping of the carbon nano tube is more uniform, and the synthesis of the high-nitrogen-content doped carbon nano tube is more facilitated.

(4) Microwave reaction heating speed is high, and synthetic MoS₂The combination of the nano-sheets and the nitrogen-doped carbon nano-tubes is firm, the accumulation of particles is not easy to cause, the time required by the synthetic material is greatly shortened, and the carbon nano-tubes and MoS are relieved₂The problem of agglomeration under the condition of long-time heating is more favorable for synthesizing the high-performance nitrogen-doped molybdenum disulfide/C/carbon nano tube composite material.

(5) The microwave reaction in the preparation process adopts a solvent-free treatment mode, so that the post-treatment processes of washing, separating, drying and the like of the product are omitted, and the production process is simplified.

(6) The nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material prepared by the method has good stability, is not easy to denature in air, is easy to store, has a large specific surface area, is used as a lithium ion battery cathode material, provides a good channel for lithium ion transmission, and shows a large specific capacity and a good cycling stability performance.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

FIG. 1 is an SEM image of acidified carbon nanotubes prepared according to the present invention;

FIG. 2 is an SEM image of the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite prepared in example 8;

FIG. 3 is a graph of the current density of 100mA g for the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material in example 8^-1Time charge and discharge cycle curve.

Detailed Description

The following non-limiting examples are presented to enable those of ordinary skill in the art to more fully understand the present invention and are not intended to limit the invention in any way.

The acidified carbon nanotubes used in the following examples were prepared by the following method:

the carbon nanotubes used had the following properties: the carbon nanotube has a diameter of 10-300nm, a length of 2-30 μm, and a specific surface area>100m²Per g, conductivity>100s/cm。

Preparing acidified carbon nanotubes: filling 1g of carbon nanotube and 200mL of concentrated sulfuric acid into a three-neck flask, ultrasonically dispersing uniformly, slowly dropwise adding 60mL of concentrated nitric acid with the concentration of 70%, refluxing and stirring for 1h at 60 ℃, naturally cooling to room temperature, adding a large amount of deionized water for dilution, standing for layering, removing supernatant, dialyzing black precipitate at the bottom by using deionized water, replacing small molecules in the black precipitate, balancing the surface of the black precipitate, and obtaining the carbon nanotube aqueous dispersion which can be stably and uniformly dispersed for a long time. Freeze-drying the carbon nanotube aqueous dispersion to obtain acidified carbon nanotube powder, and placing the acidified carbon nanotube powder in a dryer for later use. The SEM image is shown in figure 1, the one-dimensional carbon nanotube structure can be clearly seen, the carbon nanotube wall after acidification treatment is smoother, the length of the tube is more than 3 mu m, and the tube diameter is 50nm-300 nm.

The nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material of the invention is prepared in examples 1-8:

example 1

(1) 1.0g of acidified carbon nanotubes was weighed and dispersed in 20mL of 37% aqueous formaldehyde solution, and the mixture was placed in an ultrasonic apparatus and uniformly dispersed to obtain dispersion A.

(2) 0.5g of ammonium paramolybdate and20mL of concentrated aqueous ammonia (NH)₃·H₂O), heating, adding 3.0g ammonium sulfide ((NH) when the temperature is raised to 60 DEG C₄)₂S), reacting for 0.5h under the magnetic stirring state, then respectively adding 0.1g of tetramethylammonium bromide and 0.6g of melamine into the solution, and uniformly mixing by ultrasonic waves to obtain a dispersion liquid B.

(3) Mixing the dispersion A and the dispersion B, heating in water bath to 60 ℃, and stirring for 10 min. And adding triethanolamine into the reaction solution, adjusting the pH value of a reaction solution system to 8.0, ultrasonically mixing uniformly, pouring the reaction solution into a high-pressure reaction kettle, and heating to 120 ℃ for reaction for 12 hours. Filtered and dried in vacuum to give a black powder solid.

(4) And (4) placing the product obtained in the step (3) in a microwave reaction cavity, and purging for 1h by 100mL/min argon. Heating for 10min at 600W of microwave power to obtain the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material.

Example 2

(2) 0.5g of ammonium paramolybdate and 20mL of concentrated ammonia (NH) were taken₃·H₂O), heating, adding 9.0g ammonium sulfide ((NH) when the temperature is raised to 60 DEG C₄)₂S), reacting for 1h under the condition of magnetic stirring, then respectively adding 2.0g of tetramethylammonium bromide and 2.0g of melamine into the solution, and uniformly mixing by ultrasonic waves to obtain a dispersion liquid B.

Example 3

(1) 1.0g of acidified carbon nanotubes was weighed and dispersed in 30mL of 37% aqueous formaldehyde solution, and the mixture was placed in an ultrasonic apparatus and uniformly dispersed to obtain dispersion A.

(2) 0.9g of ammonium paramolybdate and 20mL of concentrated ammonia (NH) were taken₃·H₂O), heating, adding 10.0g ammonium sulfide ((NH) when the temperature is raised to 60 DEG C₄)₂S), reacting for 1h under the magnetic stirring state, then respectively adding 2.5g of tetraethylammonium bromide and 2.0g of melamine into the solution, and uniformly mixing by ultrasonic waves to obtain a dispersion liquid B.

(3) Mixing the dispersion A and the dispersion B, heating in water bath to 70 ℃, and stirring for 10 min. And adding triethanolamine into the reaction solution, adjusting the pH value of a reaction solution system to 8.0, ultrasonically mixing uniformly, pouring the reaction solution into a high-pressure reaction kettle, and heating to 120 ℃ for reaction for 12 hours. Filtered and dried in vacuum to give a black powder solid.

(4) And (4) placing the product obtained in the step (3) in a microwave reaction cavity, and purging for 1h by 100mL/min argon. And heating for 20min at 600W of microwave power to obtain the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material.

Example 4

(2) 1.0g of ammonium paramolybdate and 20mL of concentrated ammonia (NH)₃·H₂O), heating, adding 12.0g ammonium sulfide ((NH) when the temperature is raised to 60 DEG C₄)₂S), reacting for 2 hours under the magnetic stirring state, then respectively adding 1.5g of tetraethylammonium chloride and 2.5g of melamine into the solution, and uniformly mixing by ultrasonic waves to obtain a dispersion liquid B.

(3) Mixing the dispersion A and the dispersion B, heating in water bath to 70 ℃, and stirring for 20 min. And adding triethanolamine into the reaction solution, adjusting the pH value of a reaction solution system to 9.0, ultrasonically mixing uniformly, pouring the reaction solution into a high-pressure reaction kettle, and heating to 120 ℃ for reaction for 12 hours. Filtered and dried in vacuum to give a black powder solid.

(4) And (4) placing the product obtained in the step (3) in a microwave reaction cavity, and purging for 1h by 100mL/min argon. Heating for 30min at 600W of microwave power to obtain the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material.

Example 5

(2) 1.5g of ammonium paramolybdate and 30mL of concentrated ammonia (NH)₃·H₂O), heating, adding 12.0g ammonium sulfide ((NH) when the temperature is raised to 60 DEG C₄)₂S), reacting for 2 hours under the magnetic stirring state, then respectively adding 1.5g of tetrabutylammonium bromide and 2.0g of melamine into the solution, and uniformly mixing by ultrasonic waves to obtain a dispersion liquid B.

(3) Mixing the dispersion A and the dispersion B, heating in water bath to 70 ℃, and stirring for 20 min. And then adding potassium hydroxide into the reaction liquid, adjusting the pH value of a reaction liquid system to 9.0, carrying out ultrasonic mixing uniformly, then pouring the reaction liquid into a high-pressure reaction kettle, and heating to 120 ℃ for reaction for 12 hours. Filtered and dried in vacuum to give a black powder solid.

(4) And (4) placing the product obtained in the step (3) in a microwave reaction cavity, and purging for 1h by 100mL/min argon. Heating for 10min at the microwave power of 800W to obtain the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material.

Example 6

(2) 1.5g of ammonium paramolybdate and 30mL of concentrated ammonia (NH)₃·H₂O), heating, adding 12.0g ammonium sulfide ((NH) when the temperature is raised to 60 DEG C₄)₂S), reacting for 1h under the magnetic stirring state, then respectively adding 1.5g of hexadecyl trimethyl ammonium bromide and 2.5g of melamine into the solution, and uniformly mixing by ultrasonic waves to obtain a dispersion liquid B.

(3) Mixing the dispersion A and the dispersion B, heating in water bath to 80 ℃, and stirring for 30 min. And then adding potassium hydroxide into the reaction liquid, adjusting the pH value of a reaction liquid system to 9.0, carrying out ultrasonic mixing uniformly, then pouring the reaction liquid into a high-pressure reaction kettle, and heating to 140 ℃ for reaction for 15 hours. Filtered and dried in vacuum to give a black powder solid.

Example 7

(2) 0.5g of ammonium paramolybdate and 20mL of concentrated ammonia (NH) were taken₃·H₂O), heating, adding 10.0g ammonium sulfide ((NH) when the temperature is raised to 60 DEG C₄)₂S), reacting for 1h under the magnetic stirring state, then respectively adding 2.5g of hexadecyl trimethyl ammonium chloride and 2.5g of melamine into the solution, and uniformly mixing by ultrasonic waves to obtain a dispersion liquid B.

(3) Mixing the dispersion A and the dispersion B, heating in water bath to 80 ℃, and stirring for 30 min. And adding triethanolamine into the reaction solution, adjusting the pH value of a reaction solution system to 9.0, ultrasonically mixing uniformly, pouring the reaction solution into a high-pressure reaction kettle, and heating to 160 ℃ for reaction for 15 hours. Filtered and dried in vacuum to give a black powder solid.

Example 8

(2) 1.8g of ammonium paramolybdate and 20mL of concentrated ammonia (NH)₃·H₂O), heating, adding 18.0g ammonium sulfide ((NH) when the temperature is raised to 60 DEG C₄)₂S) inAnd (3) reacting for 1h under the condition of magnetic stirring, then respectively adding 3.5g of tetramethylammonium bromide and 3.0g of melamine into the solution, and uniformly mixing by ultrasonic waves to obtain a dispersion liquid B.

(3) Mixing the dispersion A and the dispersion B, heating in water bath to 80 ℃, and stirring for 30 min. And adding triethanolamine into the reaction solution, adjusting the pH value of a reaction solution system to 9.0, ultrasonically mixing uniformly, pouring the reaction solution into a high-pressure reaction kettle, and heating to 160 ℃ for reacting for 18 hours. Filtered and dried in vacuum to give a black powder solid.

(4) And (4) placing the product obtained in the step (3) in a microwave reaction cavity, and purging for 1h by 100mL/min argon. And heating for 30min at the microwave power of 1000W to obtain the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material.

An SEM image of the nitrogen-doped molybdenum disulfide/carbon nanotube composite material obtained in example 8 is shown in fig. 2, and it can be clearly seen that a molybdenum disulfide nanosheet uniformly grows on the surface of a one-dimensional carbon nanotube, and shows a compact one-dimensional structure, which is beneficial to good conductivity of the nitrogen-doped carbon nanotube and MoS₂The active components are combined to exert more excellent electrochemical performance.

Comparative example 1

In the step (1), formaldehyde solution is not used, and deionized water is used for replacing:

(1) 1.0g of acidified carbon nanotubes was weighed and dispersed in 30mL of deionized water, and placed in an ultrasonic instrument to be uniformly dispersed, and the dispersion A was recorded.

(2) 1.8g of ammonium paramolybdate and 20mL of concentrated ammonia (NH)₃·H₂O), heating, adding 18.0g ammonium sulfide ((NH) when the temperature is raised to 60 DEG C₄)₂S), reacting for 1h under the condition of magnetic stirring, then respectively adding 3.5g of tetramethylammonium bromide and 3.0g of melamine into the solution, and uniformly mixing by ultrasonic waves to obtain a dispersion liquid B.

(4) And (4) placing the product obtained in the step (3) in a microwave reaction cavity, and purging for 1h by using 100mL/min argon. Heating the mixture for 30min at the microwave power of 1000W to obtain a comparative composite material.

Comparative example 2

(2) 3.0g of melamine is weighed and added into 40mL of deionized water, and the mixture is placed in an ultrasonic instrument to be uniformly dispersed by ultrasonic, and the dispersion liquid B is marked.

(4) And (4) placing the product obtained in the step (3) in a microwave reaction cavity, and purging for 1h by 100mL/min argon. Heating for 30min with 1000W of microwave power to obtain the composite material.

Comparative example 3

In the step (3), the pH value of the solution is not adjusted, the water bath reaction of the two solutions is not carried out, and the hydrothermal reaction is directly carried out:

(3) And mixing the dispersion liquid A and the dispersion liquid B, uniformly mixing by ultrasonic waves, pouring the reaction liquid into a high-pressure reaction kettle, and heating to 160 ℃ for reacting for 18 hours. Filtered and dried in vacuum to give a black powder solid.

The materials of examples 1-8 and comparative examples 1-3 are used as the negative electrode material of the lithium ion battery. The synthesized composite material is used as an active component, a 2016 type battery shell, a metal lithium sheet (phi 16 mm multiplied by 1mm) and 1.0M LiPF are selected₆The mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1) is used as electrolyte, and Celgard2300 microporous polypropylene coal membrane is used as battery diaphragm. The materials are assembled into a button cell in a glove box filled with Ar gas, and the test is carried out after the working electrode is fully soaked by the electrolyte. The method comprises the following five steps:

(1) size mixing

The material used has a large specific surface and is easy to adsorb moisture in the air, so the material for preparing the electrode is firstly dried fully in a vacuum drying oven at 120 ℃ to remove the surface moisture. Then adding an active substance, a conductive additive (acetylene black) and a binder (PVDF) into the dispersant according to the mass percentage of 80:10:10N-methylpyrrolidone (NMP) mixed grinding, resulting in uniform mixing of the materials, making a viscous slurry.

(2) Coating film

The resulting viscous paste was uniformly coated on a copper foil (thickness of about 100 μm). The specific operation is as follows: 1) the copper foil of moderate size is cut and laid flat on a table top. 2) Removing stains on the surface of the copper foil. 3) The slurry was dispersed on a copper foil and uniformly spread on the copper foil using a die. 4) The copper foil coated with the slurry was dried in a vacuum drying oven at 120 ℃ for 12 hours.

(3) Roller compaction

After the completion of drying, the copper foil coated with the slurry was rolled with a small-sized rolling machine to prevent the electrode material from falling off from the surface of the copper foil.

(4) Tabletting

And cutting the rolled film into a plurality of circular electrode slices with the diameter of 12mm by using a manual slicer. In order to prevent the coating film from falling off during charge and discharge cycles, it was pressed into a sheet by an oil press. And taking out and weighing after drying, and waiting for battery loading.

(5) Assembled battery

The process of assembling the button cells was carried out in a glove box filled with Ar gas. The battery is assembled according to the sequence of negative battery shell/electrolyte/working electrode plate/electrolyte/diaphragm/lithium plate/positive battery shell. And standing for 24 hours, and carrying out electrochemical test after the electrolyte is fully soaked.

And carrying out charge and discharge tests on the assembled button type simulation battery. The material of example 8 was used at a voltage in the range of 0.01 to 3.0V and at a current of 100mA g^-1The results of the cycle stability test at the current density of (a) are shown in fig. 3. The first charge and discharge capacities and the discharge capacities after 100 charge and discharge tests of examples 1 to 8 and comparative examples 1 to 3 are shown in table 1. Wherein the content of nitrogen element is determined by element analysis.

The test data show that the nitrogen doping content in the composite material is improved, and the nitrogen content can reach 5.3 percent at most. Secondly, the specific capacity of the button cell for the first discharge is increased, and the first discharge capacity in the embodiment 8 reaches 1112.6 mAh g^-1Compared with comparative example 1, the product is improved by 14.1 percent, compared with comparative example 2, the product is improved by 211.5 percent, and compared with comparative example 3, the product is improved by 11.9 percent. And the composite material still keeps higher reversible capacity after being cycled for 100 times, the reversible capacity retention rate exceeds 80 percent and reaches 90.1 percent at most, which shows that the composite material prepared by the invention has higher reversible capacity and good cycle performance.

TABLE 1

Claims

1. A preparation method of a nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material comprises the following steps:

2. The preparation method according to claim 1, wherein the acidified carbon nanotubes are mixed with the formaldehyde solution in the step (1) at a solid-to-liquid ratio of 1g to 10-100 mL.

3. The method of claim 1, wherein the molybdenum salt is ammonium paramolybdate and/or sodium molybdate.

4. The method according to claim 1, wherein the quaternary ammonium salt is at least one selected from the group consisting of tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, octadecyltrimethylammonium chloride and octadecyltrimethylammonium bromide.

5. The production method according to claim 1, wherein the mixing mass ratio of the molybdenum salt, the ammonium sulfide, the quaternary ammonium salt and the melamine in the step (2) is 1:1-20:0.1-5: 0.5-5.

6. The method according to claim 1, wherein the dispersion A and the dispersion B are mixed in the step (3) by pouring the dispersion A into the dispersion B.

7. The method according to claim 1, wherein the dispersion liquid A and the dispersion liquid B are mixed in a weight ratio of the acidified carbon nanotubes in the dispersion liquid A to the melamine in the dispersion liquid B of 1:5 to 10.

8. The production method according to claim 1, wherein the base in the step (3) is an organic base or an inorganic base.

9. The method according to claim 1, wherein the base is one or more selected from triethanolamine, methylamine, ethylamine, ethylenediamine, propylamine, isopropylamine, aniline, cyclohexylamine, o-aminophenol, 2-chlorophenol, potassium carbonate, sodium bicarbonate, potassium hydroxide, and sodium hydroxide.

10. The preparation method according to claim 1, wherein the hydrothermal reaction in the step (3) is carried out at a temperature of 120 to 160 ℃ for 12 to 18 hours.

11. The preparation method according to claim 1, wherein the microwave reaction in the step (4) has a power of 600-1000W and a time of 10-30 min.

12. The nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material prepared by the method of any one of claims 1 to 11.

13. The use of the nitrogen-doped molybdenum disulfide/C/carbon nanotube composite material of claim 12 as a negative electrode material for a lithium ion battery.