CN112744860B - Nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material - Google Patents

Nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material Download PDF

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CN112744860B
CN112744860B CN201911049011.8A CN201911049011A CN112744860B CN 112744860 B CN112744860 B CN 112744860B CN 201911049011 A CN201911049011 A CN 201911049011A CN 112744860 B CN112744860 B CN 112744860B
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titanium dioxide
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郭金
廖莎
张会成
王少军
凌凤香
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Sinopec Dalian Petrochemical Research Institute Co ltd
China Petroleum and Chemical Corp
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Sinopec Dalian Research Institute of Petroleum and Petrochemicals
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Abstract

The invention provides a nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material with high specific capacity and high stability, and the rapid preparation of the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material with high nitrogen content in one step is realized through an electrostatic spinning method and subsequent microwave-assisted treatment. According to the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material, the loss caused by sublimation of a nitrogen-doped precursor in a heating process in the traditional nitrogen doping process is avoided in the preparation process, the nitrogen doping efficiency is improved, and rapid and high-nitrogen-content doping is realized. The prepared nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material is not easy to denature in air, is easy to store, has a large specific surface area, and shows high specific capacity and excellent cycling stability when being used as a lithium ion battery cathode material and a lithium ion battery cathode material.

Description

Nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material
Technical Field
The invention relates to a doped material, in particular to a nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material, and belongs to the technical field of electrode materials.
Background
Lithium ion batteries are widely used in modern electrical energy storage systems such as mobile phones and electric vehicles due to their high energy density, high operating voltage and long service life. The electrochemical properties of the negative electrode material directly affect the overall performance of the lithium ion battery. Graphite has the advantages of high coulombic efficiency, good cycle stability, abundant natural reserves and the like, and is widely applied to lithium ion battery cathode materials. However, its lower specific capacity (372 mAh g) -1 ) And is poorThe rate capability of the lithium battery can not meet the requirements of future portable equipment and electric automobiles, so that the development of a novel high-performance lithium battery cathode material is urgently needed.
Transition metal oxide and transition metal sulfide material TiO 2 ,MoS 2 ,SnO X CoO, etc. have a relatively large theoretical specific capacity. However, during the alloying/dealloying process of the negative electrode material with lithium, the metal matrix can be changed greatly in structure or volume, and the mechanical pressure related to the volume change can cause the mechanical stability of the negative electrode to be rapidly attenuated, so that the electrode is cracked and brittle, the electric contact between ions is lost, and finally, the cycle performance of the negative electrode is rapidly reduced. Therefore, it is still difficult to put lithium alloys and metal oxide negative electrode materials having high capacities into practical use. Compared with the oxide negative electrode material, the graphene material has the advantages of unique structure, excellent conductivity, light weight and the like, and can be used as a good carrier, so that the large-volume expansion of the metal oxide negative electrode in the lithium storage process is relieved, and the cyclic reversible lithium storage capacity of the metal oxide negative electrode is enhanced.
The nitrogen doping can overcome the defects of the composite material, open the energy band gap, adjust the conductivity type, change the electronic structure, improve the free carrier density and contribute to improving the conductivity and stability of the material. Therefore, the graphene carbene material with good cycle performance and the transition metal material with large specific capacity are prepared into the nano composite material with good dispersion, and nitrogen doping modification treatment is carried out, so that the lithium storage performance of the material is expected to be remarkably improved, and the method has profound significance for expanding the application of the material.
At present, few researches provide a preparation method of a graphene and transition metal active component composite material, but the method is complex in process, the graphene and the active metal are difficult to disperse uniformly, aggregation and agglomeration of the graphene material can be caused in the synthesis process, and the electrochemical performance of the composite material is further influenced. CN 104056609A provides a preparation method of titanium dioxide/graphene oxide compound, tiO is added 2 The powder is dispersed in water and the dispersion is,but due to TiO 2 The water-insoluble precursor liquid is not uniformly dispersed, so that the prepared nano composite material has poor uniformity in the subsequent electrostatic spinning process, and GO cannot be well dispersed, thereby forming agglomeration to influence the performance of the composite material.
Some reports have been made on nitrogen doping research, including high-temperature solid-phase reaction, chemical vapor deposition, arc discharge, hydrothermal method, high-temperature thermal decomposition, and the like. CN104860308B adopts a solid-phase combustion synthesis method to prepare the nitrogen-doped graphene material, and mainly mixes solid metal powder, a solid carbon source and a solid nitrogen source, and carries out combustion synthesis reaction on the mixed powder, and the reaction product is washed and purified to obtain the nitrogen-doped graphene material. However, the method generally has the problems of multiple steps, long time consumption and difficult control of nitrogen doping content, and the problem of low nitrogen doping efficiency caused by the loss of a large amount of nitrogen doping precursor due to the intensive sublimation of the nitrogen doping precursor in the heating process in the solid-phase reaction causes difficulty in preparing the high-nitrogen-content doped nano composite material, thereby limiting the wide application of the related material in the electrochemical field.
Disclosure of Invention
In order to solve the problems of complex preparation process, easy agglomeration and the like of a nitrogen-doped graphene-based composite material in the prior art, the invention provides a nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material with high specific capacity and high stability, which is used for in-situ synthesis of TiO on graphene 2 Doping is formed, graphene is uniformly dispersed in the synthesis process, is not easy to agglomerate, and has good controllability, and graphene and TiO in the composite material 2 The doping is uniform.
The invention adopts the following technical scheme to realize the technical purpose:
the technical purpose of the first aspect of the invention is to provide a preparation method of a nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material, which comprises the following steps:
(1) Placing at least one selected from PVP (polyvinylpyrrolidone) and PVA (polyvinyl alcohol) in at least one solvent selected from deionized water, acetic acid, ethanol and DMF (dimethylformamide) to obtain a solution a;
(2) Placing at least one selected from tetrabutyl titanate and isobutyl titanate in at least one solvent selected from acetic acid, ethylene glycol, methyl ether and citric acid, uniformly mixing, and adding melamine into the mixed solution to obtain a solution B;
(3) Dispersing graphene oxide in DMF or ethanol; dropwise adding an ammonium tetrathiomolybdate aqueous solution into the graphene dispersion liquid, and stirring for 1h to obtain a dispersion liquid C;
(4) Adding the solution B into the solution A for mixing, and then dropwise adding the dispersion liquid C into the mixed solution to obtain a dispersion liquid D;
(5) Performing ultrasonic treatment on the dispersion liquid D, performing electrostatic spinning to obtain a precursor fiber material, placing the precursor fiber material in a microwave reactor, and performing N 2 /O 2 And carrying out microwave reaction under the atmosphere to obtain the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material.
Further, in the step (1), the solution A is obtained by mixing according to the solid-liquid mass ratio of 1 to 10-30, preferably 1.
Further, in the step (2), the mass ratio of the tetrabutyl titanate and/or isobutyl titanate to the solvent is 1-10, and the tetrabutyl titanate and/or isobutyl titanate is uniformly dispersed by stirring or ultrasonic mixing.
Further, the graphene oxide in the step (3) is mixed with ethanol or DMF according to the proportion of 1g (10-100) mL, preferably 1g (50-80) mL; the mass ratio of ammonium tetrathiomolybdate to graphene oxide to melamine is 1.05-0.2, and the mass ratio is as follows.
Further, the mass ratio of PVP and/or PVA, tetrabutyl titanate and/or isobutyl titanate and graphene oxide in the dispersion liquid D obtained in the step (4) is 1-20.
Further, in the step (4), the temperature is 50 to 80 ℃ when the dispersion C is added dropwise to the mixture of the solution A and the solution B. Stirring and mixing the obtained dispersion liquid D for 0.5-2h.
Further, in the step (5), the distance between the two electrodes during the electrospinning is 12-16cm, and the liquid jet rate is controlled by a syringe pump to be 0.2-2mL/h, preferably 0.5-1mL/h.
Further, the power of the microwave reaction in the step (5) is 600 to 1000W, and the time is 10 to 30min. In the above preparation method, the microwave reaction chamber is purged with nitrogen or inert gas, preferably argon, before the microwave reaction. Reaction atmosphere N 2 /O 2 Middle O 2 Is 3-20%, preferably 5-10%.
Further, said graphene oxide is in particular selected from graphene oxides having the following properties: the area of the sheet layer is 100 mu m 2 The conductivity is 3500S/m or more.
Further, the graphene oxide is obtained by oxidizing graphite, and the graphene oxide is synthesized by a Hummers method, and as a more specific embodiment, the invention discloses a specific preparation method of the graphite oxide as follows: adding natural crystalline flake graphite into ice-bath concentrated sulfuric acid under the condition of stirring, cooling to 0-10 ℃, adding sodium nitrate and potassium permanganate, stirring for reaction, adding deionized water, heating to 50-100 ℃, reacting at constant temperature until the reaction solution turns bright yellow, adding hydrogen peroxide, stirring for reaction, cooling, washing and drying to obtain the graphene oxide.
The specification of the natural crystalline flake graphite is 100-500 meshes. After the reaction is finished, the post-treatment is carried out by repeatedly settling with deionized water to remove unreacted graphite particles, then centrifuging with hydrochloric acid, cleaning, removing Cl ions in the reaction solution, washing with deionized water until the pH value is close to neutral, drying and grinding.
The stripping efficiency of the Hummers method is more than 93%, the yield is more than 90%, the structural integrity of the obtained graphene oxide sheet layer is high, and the crystal lattice is complete after thermal reduction.
The technical purpose of the second aspect of the invention is to provide the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material prepared by the method, the material prepared by the method is fibrous, and graphene and TiO are 2 The doping is uniform, the material has a porous structure and the porosity is large.
It is a technical object of the third aspect of the present invention to provideThe nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material is applied as an electrode material. Because the graphene and TiO in the material 2 The doped material is uniform, has a porous structure and a high specific surface area, overcomes the defects of composite materials by uniform nitrogen doping, improves the density of free carriers, is very favorable for lithium ion measurement, transmission and storage, is suitable for serving as an electrode material, and shows larger specific capacity and better cycling stability.
Compared with the prior art, the invention has the following advantages:
(1) The preparation method prepares a proper precursor reaction solution, can form a uniform dispersion solution, and synthesizes MoS on graphene in situ 2 And TiO 2 Composite material of MoS 2 、TiO 2 The graphene is uniformly fused through interaction, high-content uniform nitrogen doping is realized, the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material is prepared, the preparation process is simplified, the problems that the nitrogen doping efficiency is low, the components are not uniformly dispersed, and the graphene is agglomerated and stacked in the high-temperature heating process, so that the performance of the composite material is influenced, are effectively solved;
(2) The material disclosed by the invention adopts microwave reaction after electrostatic spinning is finished, the heating speed is high, the heating is uniform, graphene agglomeration caused by long-time slow temperature rise in the traditional reaction can be avoided, on the other hand, graphene oxide is rapidly thermally reduced into graphene under the microwave condition, meanwhile, residual amorphous carbon is rapidly removed to finish a nitrogen doping process, more pore structures are manufactured, the porosity of the composite material is improved, the aggregation accumulation of nano particles in the long-time heat treatment process is effectively relieved, and the synthesis of an electrode material with high specific capacity is facilitated.
(3) The microwave reaction in the preparation process accelerates the reaction speed, realizes the rapid reduction of the graphene oxide, omits the post-treatment processes of washing, separation, drying and the like of the product, and simplifies the production process.
(4) The 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 circulation stability performance.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
Fig. 1 is an XRD pattern of graphene nanomaterial prepared according to the present invention;
FIG. 2 is an SEM image of the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite nanomaterial prepared in example 1;
FIG. 3 shows the current density of the nanomaterials prepared in example 1 and comparative example 1 at 100mA g -1 Time charge and discharge cycle curve.
Detailed Description
The following non-limiting examples will allow one of ordinary skill in the art to more fully understand the present invention, but will not limit the invention in any way.
The graphene oxide used in the following examples was prepared by the following method:
100mL of 98% concentrated sulfuric acid was slowly added to 500mL of a dry three-necked flask, and the three-necked flask was placed on a magnetic stirrer with ice-bath cooling. 2.0g of natural crystalline flake graphite (180 mesh) was added with rapid stirring, and when the temperature of the reaction solution was reduced to about 0 ℃, 4.0g of sodium nitrate was slowly added, and stirring was continued for 2 hours. Then slowly adding 10g of potassium permanganate in batches within 1h, continuously stirring for 2h, and controlling the reaction temperature below 10 ℃. The three-necked flask is transferred into a water bath at 40 ℃, and the reaction is continuously stirred for 2 hours. Subsequently, 200mL of warm deionized water was slowly added and the reaction solution was kept at a temperature within 100 ℃. The reaction was carried out at a constant temperature of 98 ℃ until the reaction solution became bright yellow. To the reaction solution was added 20mL of 30% hydrogen peroxide solution, and the mixture was stirred continuously to allow the mixture to react sufficiently. And after cooling, replacing deionized water with the obtained solution for repeated sedimentation, removing unreacted graphite particles, centrifugally cleaning with hydrochloric acid to remove Cl ions in the reaction solution, and then washing with deionized water until the pH value is close to neutral. And finally, vacuum drying for 12h at 80 ℃ to obtain graphene oxide, and grinding the graphene oxide into powder for later use. Its XRD pattern is shown in FIG. 1 and is located at 11 o On the left and right are the typical 001 diffraction peak of graphene oxide, which is mainly caused by intercalation of a large number of oxygen-containing functional groups between graphene sheets. The distance between graphite oxide sheets can be calculated to be 0.7nm through the Sherle formula, and is obviously larger than the interlayer spacing of graphite by 0.3254nm. The increased interlayer spacing is primarily due to oxygen-containing functional groups intercalated between graphene sheets.
Example 1
(1) 1.5g of PVP was weighed out and added to 20mL of absolute ethanol, and dissolved with stirring at 40 ℃ to obtain solution A.
(2) Weighing 1g of tetrabutyl titanate, adding the tetrabutyl titanate into 10mL of acetic acid, stirring and mixing uniformly at 40 ℃, adding 0.2g of melamine into the mixed solution, and performing ultrasonic dispersion to obtain a solution B.
(3) 0.2g of graphene oxide is weighed and dispersed in 5mL of absolute ethyl alcohol, the mixture is uniformly dispersed by ultrasonic, and then 5mL of 0.2g/mL ammonium tetrathiomolybdate solution is dropwise added and is marked as dispersion C.
(4) Adding the solution B into the solution A, stirring and mixing uniformly at 80 ℃, slowly dripping the dispersion liquid C into the mixed solution, and continuously stirring for 1h to obtain dispersion liquid D.
(5) The dispersion D was ultrasonically treated for 5min, transferred to an injector, and spun by using an electrostatic spinning device with a distance between both electrodes set to 15cm and by spraying the solution at a rate of 0.5mL/h with a syringe pump. Placing the obtained precursor fiber material in a microwave reactor at N 2 :O 2 And (2) carrying out microwave reaction for 10min under the atmosphere of =19 and the power of 600W to prepare the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material. The microstructure is shown in figure 2, the prepared nano material is uniformly dispersed, and obviously aggregated graphene material and TiO can not be seen 2 The dispersion with graphene is good, no obvious agglomeration exists, and molybdenum disulfide grows on the surface of titanium dioxide/graphene. The diameter of the prepared nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material is about 100-200 nm.
Example 2
(1) 1.5g of PVA was weighed out and added to 20mL of absolute ethanol, and dissolved with stirring at 40 ℃ to obtain solution A.
(2) Weighing 1g of tetrabutyl titanate, adding the tetrabutyl titanate into 10mL of acetic acid, stirring and mixing uniformly at 40 ℃, adding 0.2g of melamine into the mixed solution, and performing ultrasonic dispersion to obtain a solution B.
(3) 0.2g of graphene oxide is weighed and dispersed in 5mL of absolute ethyl alcohol, the mixture is dispersed uniformly by ultrasonic, and then 5mL of 0.2g/mL ammonium tetrathiomolybdate solution is dripped and recorded as dispersion C.
(4) Adding the solution B into the solution A, stirring and mixing uniformly at 80 ℃, slowly dripping the dispersion liquid C into the mixed solution, and continuously stirring for 1h to obtain dispersion liquid D.
(5) The dispersion D was sonicated for 5min, transferred to a syringe, and spun using an electrospinning device with the distance between the two electrodes set to 15cm and the solution sprayed at a rate of 0.5mL/h using a syringe pump. Placing the obtained precursor fiber material in a microwave reactor at N 2 :O 2 And (2) carrying out microwave reaction for 10min under the atmosphere of =19 and the power of 600W to prepare the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material.
Example 3
(1) 1.5g of PVP was weighed out and added to 20mL of absolute ethanol, and dissolved with stirring at 40 ℃ to obtain solution A.
(2) Weighing 1g of tetrabutyl titanate, adding the tetrabutyl titanate into 10mL of acetic acid, stirring and mixing uniformly at 40 ℃, adding 0.3g of melamine into the mixed solution, and performing ultrasonic dispersion to obtain a solution B.
(3) 0.2g of graphene oxide is weighed and dispersed in 5mL of absolute ethyl alcohol, the mixture is uniformly dispersed by ultrasonic, and then 5mL of 0.2g/mL ammonium tetrathiomolybdate solution is dropwise added and is marked as dispersion C.
(4) Adding the solution B into the solution A, stirring and mixing uniformly at 80 ℃, slowly dripping the dispersion liquid C into the mixed solution, and continuously stirring for 1h to obtain dispersion liquid D.
(5) The dispersion D was sonicated for 5min, transferred to a syringe, and spun using an electrospinning device with the distance between the two electrodes set to 15cm and the solution sprayed at a rate of 0.5mL/h using a syringe pump. Placing the obtained precursor fiber material in a microwave reactor at N 2 :O 2 And (2) carrying out microwave reaction for 10min under the atmosphere of =19 and the power of 600W to prepare the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material.
Example 4
(1) 1.0g of PVP was weighed out and added to 20mL of absolute ethanol, and dissolved with stirring at 40 ℃ to obtain solution A.
(2) Weighing 1g of tetrabutyl titanate, adding the tetrabutyl titanate into 10mL of acetic acid, stirring and mixing the tetrabutyl titanate and the acetic acid uniformly at 40 ℃, adding 0.2g of melamine into the mixed solution, and performing ultrasonic dispersion to obtain a solution B.
(3) 0.2g of graphene oxide is weighed and dispersed in 5mL of absolute ethyl alcohol, the mixture is dispersed uniformly by ultrasonic, and then 5mL of 0.2g/mL ammonium tetrathiomolybdate solution is dripped and recorded as dispersion C.
(4) Adding the solution B into the solution A, stirring and mixing uniformly at 80 ℃, slowly dripping the dispersion liquid C into the mixed solution, and continuously stirring for 1h to obtain dispersion liquid D.
(5) The dispersion D was sonicated for 5min, transferred to a syringe, and spun using an electrospinning device with the distance between the two electrodes set to 15cm and the solution sprayed at a rate of 0.5mL/h using a syringe pump. Placing the obtained precursor fiber material in a microwave reactor at N 2 :O 2 And (2) carrying out microwave reaction for 10min under the atmosphere of =19 and the power of 600W to prepare the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material.
Example 5
(1) 1.0g PVP was weighed into 20mL of absolute ethanol and dissolved at 40 deg.C with stirring to obtain solution A.
(2) Weighing 1g of tetrabutyl titanate, adding the tetrabutyl titanate into 10mL of acetic acid, stirring and mixing the tetrabutyl titanate and the acetic acid uniformly at 40 ℃, adding 0.2g of melamine into the mixed solution, and performing ultrasonic dispersion to obtain a solution B.
(3) 0.2g of graphene oxide is weighed and dispersed in 5mL of absolute ethyl alcohol, the mixture is dispersed uniformly by ultrasonic, and then 5mL of 0.2g/mL ammonium tetrathiomolybdate solution is dripped and recorded as dispersion C.
(4) Adding the solution B into the solution A, stirring and mixing uniformly at 80 ℃, slowly dripping the dispersion liquid C into the mixed solution, and continuously stirring for 1h to obtain dispersion liquid D.
(5) The dispersion D was sonicated for 5min, transferred to a syringe, and spun by using an electrospinning device with the distance between the two electrodes set to 15cm and the solution sprayed at a rate of 1.0mL/h with a syringe pump.Placing the obtained precursor fiber material in a microwave reactor at N 2 :O 2 And (2) carrying out microwave reaction for 10min under the atmosphere of =19 and the power of 600W to prepare the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material.
Example 6
(1) 1.0g of PVP was weighed out and added to 20mL of absolute ethanol, and dissolved with stirring at 40 ℃ to obtain solution A.
(2) Weighing 1g of tetrabutyl titanate, adding the tetrabutyl titanate into 10mL of acetic acid, stirring and mixing the tetrabutyl titanate and the acetic acid uniformly at 40 ℃, adding 0.2g of melamine into the mixed solution, and performing ultrasonic dispersion to obtain a solution B.
(3) 0.2g of graphene oxide is weighed and dispersed in 5mL of absolute ethyl alcohol, the mixture is dispersed uniformly by ultrasonic, and then 5mL of 0.2g/mL ammonium tetrathiomolybdate solution is dripped and recorded as dispersion C.
(4) Adding the solution B into the solution A, stirring and mixing uniformly at 80 ℃, slowly dripping the dispersion liquid C into the mixed solution, and continuously stirring for 1h to obtain dispersion liquid D.
(5) The dispersion D was sonicated for 5min, transferred to a syringe, and spun using an electrospinning device with the distance between the two electrodes set to 15cm and the solution sprayed at a rate of 0.5mL/h using a syringe pump. Placing the obtained precursor fiber material in a microwave reactor at N 2 :O 2 And (2) carrying out microwave reaction for 20min under the atmosphere of =19 and the power of 800W to prepare the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material.
Comparative example 1
(1) 1.5g PVP was weighed into 20mL of absolute ethanol and dissolved at 40 ℃ with stirring to obtain solution A.
(2) 1g of tetrabutyl titanate is weighed and added into 10mL of acetic acid, and the solution B is marked as the mixture after being stirred and mixed evenly at 40 ℃.
(3) 0.2g of graphene oxide is weighed and dispersed in 5mL of absolute ethyl alcohol, and the dispersion liquid C is marked after uniform ultrasonic dispersion.
(4) Adding the solution B into the solution A, stirring and mixing uniformly at 80 ℃, slowly dripping the dispersion liquid C into the mixed solution, and continuously stirring for 1h to obtain dispersion liquid D.
(5)The dispersion D was ultrasonically treated for 5min, transferred to an injector, and spun by using an electrostatic spinning device with a distance between both electrodes set to 15cm and by spraying the solution at a rate of 0.5mL/h with a syringe pump. The precursor fiber material obtained was admixed with 0.2g of melamine, ground to homogeneity, placed in a microwave reactor and subjected to a reaction under N 2 :O 2 And (2) carrying out microwave reaction for 10min under the atmosphere of =19 and the power of 600W to prepare the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material.
The materials of examples 1 to 6 and comparative example 1 were used as negative electrode materials for lithium ion batteries. The synthesized nitrogen-doped graphene is used as an active component, a 2016 type battery shell, a metal lithium sheet (phi 16 mm multiplied by 1 mm) and 1.0M LiPF are selected 6 The Ethylene Carbonate (EC)/diethyl carbonate (DEC) mixed solution (volume ratio 1. 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 fully dried in a vacuum drying oven at 120 ℃ to remove the moisture on the surface. Then adding an active substance, a conductive additive (acetylene black) and a binder (PVDF) into the dispersant according to the mixture ratio of 80 mass percentN-methylpyrrolidone (NMP) to mix and grind the materials to mix uniformly and make 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) Rolling compaction
After the completion of drying, the copper foil coated with the slurry was rolled by a small-sized rolling machine to prevent the electrode material from falling off from the surface of the copper foil.
(4) Tablet press
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 the charge-discharge cycle, 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 electrode battery shell/electrolyte/working electrode plate/electrolyte/diaphragm/lithium plate/positive electrode battery shell. And standing for 24 hours, and performing 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 1 was applied at a voltage in the range of 0.01 to 3.0V and at 100mA g -1 The results of the cycle stability test at the current density of (a) are shown in fig. 3. The first charge/discharge capacity and the discharge capacity after 100 charge/discharge tests of examples 1 to 6 and comparative example 1 are shown in table 1.
TABLE 1
Figure DEST_PATH_IMAGE002
The test data show that the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material prepared by the invention has higher specific capacity. Wherein the first maximum discharge capacity can reach 1206.9 mAh.g -1 Compared with the high-temperature solid-phase nitrogen-doped composite material in the comparative example 1, the high-temperature solid-phase nitrogen-doped composite material has excellent performance, and can still maintain high reversible capacity of 869.1 mAh.g after being circulated for 100 times -1 And the reversible capacity retention rate exceeds 72.0%, which shows that the material prepared by the invention has higher reversible capacity and good cycle performance.

Claims (15)

1. A preparation method of a nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material comprises the following steps:
(1) Placing at least one selected from PVP and PVA in at least one solvent selected from deionized water, acetic acid, ethanol and DMF to obtain solution A;
(2) Placing at least one selected from tetrabutyl titanate and isobutyl titanate in at least one solvent selected from acetic acid, ethylene glycol, methyl ether and citric acid, uniformly mixing, and adding melamine into the mixed solution to obtain a solution B;
(3) Dispersing graphene oxide in DMF or ethanol; dropwise adding an ammonium tetrathiomolybdate aqueous solution into the graphene dispersion liquid, and stirring for 1h to obtain a dispersion liquid C;
(4) Adding the solution B into the solution A for mixing, and then dropwise adding the dispersion liquid C into the mixed solution to obtain a dispersion liquid D;
(5) Performing ultrasonic treatment on the dispersion liquid D, performing electrostatic spinning to obtain a precursor fiber material, placing the precursor fiber material in a microwave reactor, and performing N 2 /O 2 And carrying out microwave reaction in the atmosphere to obtain the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material.
2. The preparation method according to claim 1, wherein the solution A is obtained by mixing in step (1) at a solid-liquid mass ratio of 1.
3. The production method according to claim 1, wherein the mass ratio of the tetrabutyl titanate and/or the isobutyl titanate mixed with the solvent in the step (2) is 1.
4. The method according to claim 1, wherein the graphene oxide is mixed with ethanol or DMF in a ratio of 1 g.
5. The preparation method according to claim 4, wherein the graphene oxide is mixed with ethanol or DMF in the proportion of 1g.
6. The preparation method according to claim 1, wherein the mass ratio of ammonium tetrathiomolybdate to graphene oxide to melamine in step (3) is 1.
7. The preparation method according to claim 1, wherein the mass ratio of PVP and/or PVA, tetrabutyl titanate and/or isobutyl titanate, graphene oxide in the dispersion liquid D obtained in step (4) is 1-20.
8. The process according to claim 1, wherein the temperature of the mixture of the solution A and the solution B to which the dispersion C is added dropwise in the step (4) is 50 to 80 ℃.
9. The method according to claim 1, wherein the dispersion D obtained in the step (4) is mixed and reacted for 0.5 to 2 hours.
10. The method of claim 1, wherein the distance between the two electrodes during the electrospinning is 12 to 16cm, and the liquid injection rate is controlled by a syringe pump to be 0.2 to 2mL/h.
11. The preparation method according to claim 1, wherein the microwave reaction in the step (5) has a power of 600 to 1000W and a time of 10 to 30min.
12. The method according to claim 1, wherein the microwave reaction atmosphere is N 2 /O 2 Middle O 2 The volume ratio of (A) is 3-20%.
13. The method according to claim 1, wherein the graphene oxide has a sheet area of 100 μm 2 The conductivity is 3500S/m or more.
14. The nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material prepared by the method of any one of claims 1 to 13.
15. Use of the nitrogen-doped molybdenum disulfide/titanium dioxide/graphene composite material of claim 14 as an electrode material.
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