CN103441246A - Preparation method and application of three-dimensional nitrogen-doped graphene base tin dioxide composite material - Google Patents

Abstract

The invention discloses a preparation method and application of a nitrogen-doped graphene-based tin dioxide composite material with a three-dimensional structure. The preparation method of the present invention adopts two-dimensional graphene with a single-layer carbon atom structure as a carrier, uses polyethyleneimine as a nitrogen source and a crosslinking agent, and prepares a three-dimensional nitrogen-containing graphene-based metal oxide nanocomposite material. The metal oxide nanoparticles obtained by this method are uniformly loaded on the nitrogen-containing graphene framework. The electrochemical test proves that the nitrogen-doped graphene ^- based metal oxide composite material with three-dimensional structure obtained by the preparation method of the present invention has excellent cycle stability and rate performance. The discharge capacity of the tin oxide material can reach 1000mAh·g ^-1 .

Description

Preparation method and application of three-dimensional nitrogen-doped graphene-based tin dioxide composite material

technical field

The invention relates to a method and application of a three-dimensional nitrogen-doped graphene-based metal tin dioxide composite material, and belongs to the fields of material science and electrochemical technology. the

Background technique

With the increasingly prominent energy and environmental issues, the new energy industry has received more and more attention. The hybrid electric vehicle and electric vehicle industries are developing rapidly, and lithium-ion batteries are widely used as an important energy storage device. Lithium-ion batteries have some excellent properties such as high energy density and good cycle performance, and are considered to be one of the most effective energy storage methods at present. Therefore, further improving their energy density and cycle performance is also a difficult and hot topic of current research. the

The negative electrode of a lithium-ion battery is an important part of the battery, and its structure and performance directly affect the capacity and cycle performance of the lithium-ion battery. At present, graphite is the main anode material for commercial lithium-ion batteries. Graphite is low in cost and widely available in sources, and is suitable for commercialization; however, its capacity is relatively low, with a theoretical capacity of only 372mAh g ^-1 . restricted.

Metal oxides such as SnO ₂ have high specific capacity as negative electrode materials for lithium-ion batteries, and their specific capacity is as high _as 700-1000mAh g ^-1 ; The change is as high as 200-300%, and this volume change will cause pulverization of the electrode, resulting in disconnection of the active material and the current collector. Therefore, most metal oxides have the problem of rapid capacity decay when they are used as electrodes of lithium-ion batteries, which also limits the development and practical application of metal oxides as anode materials for lithium-ion batteries.

At present, in order to expand the application of metal oxides in lithium-ion battery anode materials, researchers have conducted in-depth research on these problems existing in metal oxides, such as modifying electrode materials, including doping, compounding and nanotechnology. The preparation of materials, through these methods to improve the performance of electrode materials, especially in the nanoscale composite of metal oxides and carbon materials, especially carbon materials doped with heteroatoms such as boron and nitrogen, to prepare new nanostructures become the current research hotspot. the

Heteroatom-doped carbon materials have more excellent electrical conductivity of pure carbon materials and have their unique excellent properties; it can be used as a good carrier of metal oxides by absorbing the metal oxides in the charging and discharging process of lithium-ion batteries. Volume change stress, thereby enhancing the cycle performance of metal oxides. Therefore, a new nanostructured composite material constructed by combining heteroatom-doped carbon materials and metal oxides is expected to significantly improve the performance of lithium-ion batteries, and has far-reaching implications for its expanded application. significance. the

Contents of the invention

In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a three-dimensional composite material capable of enhancing the cycle performance of metal oxides. the

To achieve the above object, the present invention provides a preparation method and application of a nitrogen-doped graphene-based metal oxide composite material with a three-dimensional structure. Specifically, a three-dimensional nitrogen-doped graphene-based metal oxide nanocomposite material is prepared by using two-dimensional graphene with a single-layer carbon atom structure as a carrier and polyethyleneimine as a nitrogen source precursor. the

The present invention solves the above technical problems through the following technical solutions:

In one aspect, the present invention provides a method for preparing a nitrogen-doped graphene-based metal oxide composite material with a three-dimensional structure. the

The preparation method of the invention adopts a two-step method to synthesize the nitrogen-doped graphene-based metal oxide composite material with a three-dimensional structure. First, metal chloride is hydrolyzed on the surface of graphene oxide, and graphene-based metal oxide nanosheets are obtained by in-situ growth method; secondly, under hydrothermal conditions, the crosslinking effect of polyethyleneimine is used to make the nanosheets self- Assemble into a three-dimensional structure, introduce a nitrogen source at the same time, and obtain a three-dimensional nitrogen-doped graphene tin dioxide composite material through calcination and carbonization. the

In the present invention, the specific method for preparing a three-dimensional nitrogen-doped graphene-based metal tin dioxide composite material comprises the following steps:

First, the graphene oxide (GO) dimethylformamide (DMF) solution with a concentration of 1 mg/mL was ultrasonically mixed;

Secondly, after adding the metal oxide precursor to the above dispersion liquid, mix it evenly and keep it warm at 60-90°C for 12 hours;

Finally, the solution after the above reaction is centrifuged, washed with deionized water, and the concentrated deionized water dispersion obtained is for use;

Step 2. Preparation of three-dimensional graphene-based tin dioxide airgel:

First, put the above-mentioned graphene-based metal oxide nanosheet dispersion in a 10mL vial, add a certain amount of cross-linking agent of known concentration, mix well, and place the vial in 80mL of water Direct hydrothermal treatment in hot kettle;

Secondly, freeze-dry and calcinate the block obtained after the above reaction, and finally obtain a three-dimensional nitrogen-doped graphene-based tin dioxide composite material;

Wherein, the metal oxide precursor is tin tetrachloride pentahydrate (SnCl ₄ ·5H ₂ O). The cross-linking agent is polyethyleneimine (PEI), which is also the nitrogen source precursor.

In a specific embodiment of the present invention, before adding the metal chloride to the dispersion, add hydrochloric acid to the dispersion to adjust the pH of the solution to 1-3; Incubate at ~90°C for 1-5 hours. the

When the present invention is concretely implemented, the mass ratio of tin tetrachloride pentahydrate added in step 1 and graphene oxide is preferably 2.27:1;

In the preparation method of the present invention, when the nanosheets are three-dimensionally assembled in step 2, a method of hydrothermal self-assembly is adopted. the

In a preferred embodiment of the present invention, the product obtained in step 2 is freeze-dried for 48 hours. the

In the present invention, the freeze-drying method is adopted, and those skilled in the art can take different times according to actual needs, and there is no special limitation on this. the

In the preparation method of the present invention, metal oxide particles are loaded on the surface of graphene, which inhibits the agglomeration of the particles to a certain extent, increases the specific surface area, and thereby improves the capacity of the material. At the same time, this three-dimensional structure material can not only alleviate the volume change of metal oxides such as tin dioxide particles during charging and discharging, but also inhibit the particle crushing and falling off, thereby greatly improving the cycle stability of the material. Nitrogen doping can effectively increase the ratio of carbon to oxygen in the material, thereby inhibiting the oxidation of the organic electrolyte and improving the cycle performance of the material to a certain extent. Moreover, the three-dimensional structure is conducive to the full contact between the electrolyte and the material, which can improve the conductivity of the entire electrode material and realize the rapid transfer of electrons, so that the material has high rate performance. the

On the other hand, the present invention also provides an application of a graphene-based metal tin dioxide composite material with a three-dimensional structure. the

The graphene-based metal tin dioxide composite material with a three-dimensional structure of the present invention is preferably applied in lithium-ion battery negative electrode materials. When the composite material with three-dimensional structure of the present invention is used as the negative electrode material of the lithium ion battery, the capacity of the negative electrode material can be increased and its cycle performance can also be enhanced. the

In a specific embodiment of the present invention, the lithium-ion button-type half-battery uses the graphene-based metal tin dioxide composite material with a three-dimensional structure as the negative electrode material, the positive electrode is lithium metal, and the electrolyte is ethyl carbonate of lithium hexafluorophosphate solution or dimethyl carbonate solution. the

The present invention adopts two-dimensional graphene with a single-layer carbon atom structure as a skeleton, tin tetrachloride pentahydrate as a tin source precursor, and polyethyleneimine as a crosslinking agent to prepare three-dimensional graphene through a simple two-step method Metal-based tin dioxide nanocomposites. The method has the advantages of simple process, mild conditions and low cost. The metal oxide nanoparticles obtained by the method of the invention are uniformly loaded on the graphene skeleton and have a micron-scale structure. The electrochemical test proves that the prepared composite material has excellent cycle stability and rate performance; the experiment proves that under the charge and discharge current of 0.2Ag ^-1 : the discharge capacity of the prepared tin dioxide material can reach 1010mAh g ^-1 . Therefore, the invention provides good experimental data and theoretical support for the research and application of metal oxides in the field of electrochemistry.

The idea, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of the present invention. the

Description of drawings

FIG. 1 is a topographical view of the three-dimensional nitrogen-doped graphene-based tin dioxide of Example 1-3 of the present invention; wherein, a and b are the SEM images of Example 1, respectively, and c is the TEM image of Example 1. the

Fig. 2 is the three-dimensional nitrogen-doped graphene-based tin dioxide composite material of the embodiment of the present invention 1 as the cycle performance figure of lithium-ion battery negative electrode material. the

Fig. 3 is a graph of the rate performance of the three-dimensional nitrogen-doped graphene-based tin dioxide composite material in Example 1 of the present invention as a lithium-ion battery negative electrode material. the

Detailed ways

Example 1

The first step, preparation of graphene-based tin dioxide nanosheets:

(1) Sonicate 1mg/mL graphene oxide dimethylformamide solution (50mL) to form a uniformly mixed dispersion;

(2) Add concentrated hydrochloric acid to the above dispersion to adjust the pH of the solution to 2; add tin tetrachloride pentahydrate (SnCl ₄ 5H ₂ O) under vigorous stirring, keep warm at 80°C for 12 hours after adding, and cool;

Wherein, the mass ratio of added SnCl ₄ ·2H ₂ O to graphene oxide is 2.27:1.

(3) Centrifuge the solution after the above reaction, wash it with deionized water, repeat the centrifugation and washing operations four times, and concentrate to obtain a viscous liquid, which is graphene-based tin dioxide nanosheets. the

The second step is to prepare a three-dimensional nitrogen-doped graphene-based tin dioxide composite material:

(1) Add 1 mL of PEI aqueous solution to the viscous solution of the above-mentioned concentrated 5 mg/mL graphene-based tin dioxide nanosheets prepared above, mix well, and place it under the condition of 180 ° C for 12-18 h;

Wherein, the mass ratio of graphene oxide to PVA is 1:0.044;

(2) Freeze-dry the block obtained after the above reaction for 48 hours, then calcinate and carbonize it at 300°C for 2 hours under the protection of N ₂ , and finally obtain a nitrogen-doped graphene-based tin dioxide composite material with a three-dimensional structure. SEM and TEM photos are shown in Fig. 1a-c.

The obtained composite material is used as the negative electrode material of lithium-ion battery to assemble a lithium-ion button-type half-cell (the counter electrode is lithium metal), and the lithium-ion button-type half-cell is electrochemically tested, and its cycle performance diagram and rate performance diagram are shown in Fig. 2, 3 shown. the

It can be seen from Figure 2 that the nitrogen-doped composite material with three-dimensional structure shows extremely high capacity (1010mAhg ^-1 ), and very superior cycle performance. The material still maintains a capacity of 1000mAhg ^-1 after 100 cycles at a charge-discharge current of 0.2mA g ^-1 . It can be seen from Figure 3 that the material still maintains a capacity of 200mAh ^{g -1} at a high current of 8Ag ^-1 , and when the current returns to 0.2mA g ^-1 , the capacity can also be restored to 1010mAh g ^-1 , which is beneficial to the For tin materials, it has very excellent rate performance.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims. the

Claims (8)

1. the preparation method of the nitrogen-doped graphene base tin ash composite material of a three-dimensional structure, is characterized in that, comprises the following steps;

Step 1, prepare graphene-based metal oxide nano-sheet:

At first, add a small amount of concentrated hydrochloric acid in the graphene oxide dimethyl formamide solution that is 1mg/mL to concentration, ultrasonic mixing;

Secondly, after adding metal oxide precursor in above-mentioned solution, 60-90 ℃ of insulation 12 hours;

Finally, above-mentioned reacted solution is carried out centrifugal, deionized water washing, the concentrated deionized water dispersion liquid obtained is stand-by;

Step 2, the three-dimensional graphene-based tin ash aeroge of preparation:

At first, be placed in the vial of 20mL to the dispersion liquid of above-mentioned graphene-based metal oxide nano-sheet, add the polymine of a certain amount of concentration known, after mixing, and the water heating kettle Direct Hydrothermal processing that vial is placed in to 150mL;

Secondly, by the block freeze drying calcination processing obtained after above-mentioned reaction, finally obtain the nitrogen-doped graphene base tin ash composite material of three-dimensional structure.

2. the preparation method of the nitrogen-doped graphene base tin ash composite material of a kind of three-dimensional structure as claimed in claim 1, is characterized in that, described metal oxide precursor is stannic chloride pentahydrate.

3. the preparation method of the nitrogen-doped graphene base tin ash composite material of a kind of three-dimensional structure as claimed in claim 1, is characterized in that, polymine is nitrogenous source.

4. the preparation method of the nitrogen-doped graphene base tin ash composite material of a kind of three-dimensional structure as claimed in claim 1, is characterized in that, polymine is crosslinking agent.

5. the preparation method of the nitrogen-doped graphene base tin ash composite material of a kind of three-dimensional structure as claimed in claim 1, is characterized in that, the mass ratio of graphene oxide and metal oxide precursor is 1:2.27.

6. the preparation method of the nitrogen-doped graphene base tin ash composite material of a kind of three-dimensional structure as claimed in claim 1, is characterized in that, the mass ratio of graphene oxide and polymine is 1:0.044.

7. the nitrogen-doped graphene base tin ash composite material of the three-dimensional structure that the preparation method of the nitrogen-doped graphene base tin ash composite material of a kind of three-dimensional structure as claimed in claim 1 obtains.

8. the application of nitrogen-doped graphene base tin ash composite material in lithium ion battery of three-dimensional structure as claimed in claim 1.

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