CN106654280A - A W2C@onion-like carbon/amorphous carbon nanocomposite and its preparation method and application - Google Patents

Abstract

The invention provides a W2C@onion-shaped carbon/amorphous carbon nanometer composite and a preparing method and application thereof, and belongs to the technical field of nanometer material preparing. According to the microstructure of the nanometer composite material, a W2C@onion-shaped carbon core-shell structure nanocapsule is embedded into an amorphous carbon nanometer sheet. The preparing method includes the steps that tungsten powder and coal powder are pressed into a block in a certain atomic percent with the plasma arc discharging method to serve as an anode target material, graphite is used as a cathode material, argon and hydrogen are led and serve as working gas, a certain distance is kept between the cathode graphite electrode and the anode target material tungsten-coal powder block, arc discharging is carried out between the anode and the cathode, and the W2C@onion-shaped carbon/amorphous carbon nanometer composite is obtained. When the nanometer composite serves as a cathode of a lithium ion battery, the good cycle performance is shown, and the W2C@onion-shaped carbon/amorphous carbon nanometer composite is a lithium ion battery cathode material with quite-good prospects. The preparing process is simple, the cost is low, and industrial production is easy to achieve.

Description

A W2C@onion-like carbon/amorphous carbon nanocomposite and its preparation method and application

technical field

The invention belongs to the technical field of material preparation, and specifically relates to a W ₂ C@onion-like carbon/amorphous carbon nanocomposite and its preparation method and application.

Background technique

With the increasing demand for energy, the reduction of fossil fuel reserves and the aggravation of environmental pollution, the development of clean and efficient new energy has become a focus of attention. As an energy storage device, lithium-ion batteries are widely used in small portable devices due to their environmental protection, light weight, high capacity, and long life. The positive and negative electrode materials of lithium-ion batteries are the core factors that determine their performance. At present, the commercial negative electrode material is mainly graphite material, and its theoretical specific capacity is only 372mAh/g, which can no longer meet people's demand for battery performance. Therefore, it is of great significance to research and develop new lithium-ion battery anode materials.

Although transition metal carbides have the advantages of non-toxicity, abundant reserves, low cost, and excellent catalytic performance, due to their theoretically small specific capacity, transition metal carbides cannot be used as negative electrode materials for lithium-ion batteries for a long time. In 2012, Su et al first reported that the core-shell structure Fe@Fe ₃ C/C nanocomposite has a stable discharge capacity of ~500mAh/g, proving its potential as an anode material for lithium-ion batteries. Although, Fe and Fe ₃ C are almost inactive for Li ⁺ intercalation, the authors point out that Fe ₃ C can act as a catalyst to promote the reversible formation/decomposition process of solid electrolyte interface (SEI) film, thereby enhancing the electrochemical performance of carbon-based anodes. performance. (L. Su, Z. Zhou, P. Shen. Core-shell Fe@Fe ₃ C/Cnanocomposites as anode materials for Li ion batteries. Electrochimica Acta 87(2013) 180-185). It is well known that there are two obstacles hindering carbides as anode materials for Li-ion batteries: (1) volume expansion/contraction during repeated cycling; (2) low electrical conductivity of carbides. At present, the research on the above two problems is mainly divided into three ways to solve: (1) nanometerization of materials; (2) compounding of active materials; (3) nanocomposite materials. Among them, the third approach is the most widely used in the research. Among them, in the selection of the substrate, due to the stable structure of the carbon material, the volume change during the charging and discharging process is relatively small, and the conductivity, thermal and chemical stability are good, and it has a certain specific capacity, so it has received extensive attention. Typically, the carbon component in the nanocomposite has dual functions: as a conductive additive to facilitate electron transport in carbides and as an elastic buffer layer to enhance electrode structural stability.

Many scholars at home and abroad are committed to the research on the preparation method of transition metal carbide/carbon composite materials. The brief introduction is as follows:

Chinese invention patent "Carbon-coated metal, carbon-coated metal carbide nano-powder synthesis method" (Patent No.: CN99120144.2) adopts the AC arc method, using carbon and metal in a vacuum consumable electrode arc furnace through plasma discharge at the same time Evaporate, and generate carbon-coated metal or metal carbide nanopowder through chemical reaction.

The Chinese invention patent "Carbon Composite Material Containing Metal Carbide Particles Dispersed Therein and Its Preparation Method" (patent number: 200580012680.8) relates to carbon composite material comprising carbon, carbon fiber or carbon/carbon fiber matrix dispersed in The metal carbide particles and do not contain free metal particles, wherein the metal carbide particles are metal carbides on at least the particle surface or the entire particle, and are formed from a metal source (i.e. selected from metal particles, metal oxide particles or composite metal oxide particles) at least one of) and a carbon source (ie, a thermosetting resin) are synthesized in situ.

Chinese invention patent "a preparation method of carbon-based metal nitride and carbide supercapacitor materials" (Patent No.: 200710022253.9) The raw materials are reacted to obtain hydrogel precursors, and the obtained hydrogels are exposed to nitrogen gas or hydrogen Under normal pressure drying and carbonization, carbon-based transition metal nitride and carbide supercapacitor materials are prepared.

Chinese invention patent "A C/Fe ₃ C lithium-ion battery negative electrode material and its preparation method" (Patent No.: 201010532415.5) uses organic solvents for thermal polymerization of raw materials to obtain precursors, and then conducts heat treatment under the protection of argon atmosphere , a C/Fe ₃ C composite consisting of amorphous carbon and Fe ₃ C was obtained.

Chinese invention patent "Preparation method of onion carbon-supported transition metal carbide nanocomposites" (Patent No.: 201010600970.7) The raw materials are filled in a closed reactor in proportion, and the reactor is heated by an initiator-assisted chemical vapor deposition method One-step reaction yields nanocomposites of onion carbon-supported transition metal carbides.

Chinese invention patent "A method for preparing metal carbide or carbon-coated metal carbide" (Patent No.: 201210562395.5) The metal salt powder is roasted at high temperature to form a metal oxide precursor, and the liquid carbon-containing compound is used as the liquid carbon source and Metal oxide precursors undergo reduction and carbonization reactions to prepare metal carbides or carbon-coated metal carbides.

Chinese invention patent "macroscopic film and fiber absorbing material composed of nanocapsules and nanotubes and its preparation method" (patent number: 201310065805.X) uses plasma arc discharge technology to prepare Fe@C, Fe ₃ C@ A macroscopic film composed of C nanocapsules and carbon nanotubes interwoven and connected.

Chinese invention patent "a carbon-coated cobalt-tungsten double metal carbide, preparation method and application" (patent number: 201410723029.2) can be obtained by one-step calcination of a mixture of cobalt and tungsten metal compounds and nitrogen-rich organic compounds. coated cobalt-tungsten bimetallic carbide.

Chinese invention patent "a tubular core-shell structure graphitie@Fe ₃ C composite material and its preparation method and application" (Patent No.: 201410827354.3) uses graphite worms, ferrocene, and 30% hydrogen peroxide as raw materials, through a simple liquid phase method and sintering under the protection of inert gas to prepare graphite@Fe ₃ C nanocomposites.

Because of the high temperature required, the use of toxic and expensive chemical precursors, advanced equipment, and tedious procedures, the above preparation methods of transition metal carbides/C complexes are usually difficult to industrialize. According to application requirements, it is generally desired to obtain transition metal carbide/C nanocomposites with simple process and low cost. However, the W ₂ C@onion-like carbon/amorphous carbon nanocomposite material and the method for preparing the nanocomposite material in one step have not been reported.

Contents of the invention

The purpose of the present invention is to provide a W ₂ C@onion-like carbon/amorphous carbon nanocomposite and a preparation method thereof, in order to expect the obtained nanocomposite to have good cycle performance when used as a negative electrode of a lithium-ion battery, while the preparation process is simple and the cost is low.

In order to achieve the above object, the present invention is achieved through the following technical solutions.

The invention prepares a W ₂ C@onion-like carbon/amorphous carbon nanocomposite, and the microscopic structure of the nanocomposite is W ₂ C@onion-like carbon core-shell nanocapsules embedded with amorphous carbon nanosheets. Wherein, the particle size of W ₂ C@onion-like carbon nanocapsules is 2-15 nm, the core is W ₂ C nanoparticles, and the outer shell is onion-like carbon.

The present invention also provides a preparation method of the above-mentioned W ₂ C@onion-like carbon/amorphous carbon nanocomposite, which is prepared in situ under working gas by using plasma arc discharge technology; wherein:

The graphite electrode is used as the cathode, and the tungsten-coal powder block is used as the anode target, and the distance between the cathode graphite electrode and the anode target tungsten-coal powder block is kept at a distance of 2-30mm; the voltage of the arc discharge is 10-40V; the working gas For argon and hydrogen gas.

The anode target is a tungsten-coal powder block, and the tungsten powder and coal powder are pressed into a block under a pressure of 1 MPa to 1 GPa as an anode target material for a plasma arc furnace. The anode target material accounts for tungsten The mass percentage is 30-50%.

The partial pressure of the working gas argon is 0.01-0.5 MPa, and the partial pressure of the hydrogen gas is 0.01-0.3 MPa.

The invention also provides the application of the W ₂ C@onion-like carbon/amorphous carbon nanocomposite as the negative electrode material of the lithium ion battery.

The application method is: (1) Weigh W ₂ C@ onion-like carbon/amorphous carbon nanocomposite, acetylene black, and vinylidene fluoride according to the mass ratio of 7:2:1, and put them into a crucible for grinding , then add N-methylpyrrolidone and continue to grind to make the mixture into a paste, then apply it evenly on the copper foil, dry it at about 100°C for 12-20h, then roll the copper foil and cut it into a diameter (2) In a glove box filled with argon gas, the electrode sheet, diaphragm, lithium sheet and nickel foam are assembled into a button cell by conventional methods.

A constant current charge-discharge cycle test was carried out at room temperature in an experimental manner to measure the cycle stability of the button cell.

Compared with the prior art, the outstanding advantage of the present invention is that

1) The present invention prepared W ₂ C@onion-like carbon/amorphous carbon nanocomposite for the first time;

2) The preparation process of the present invention has simple conditions, low cost, easy control, and one-time production of products, which provides conditions for the practical application of W ₂ C@onion-like carbon/amorphous carbon nanocomposites;

3) The W ₂ C@onion-like carbon/amorphous carbon nanocomposite prepared in the present invention is embedded in amorphous carbon nanosheets with W ₂ C@onion-like carbon core-shell structure nanocapsules, which is conducive to the diffusion of lithium ions , buffer volume change and increase in conductivity, and W ₂ C nanoparticles have the effect of catalytically modifying SEI film, making the partial reduction products of SEI film reversible, so it is beneficial to the electrochemical performance of nanocomposites, especially its cycle stability.

Description of drawings

Figure 1 is a schematic diagram of the device for preparing W ₂ C@onion-like carbon/amorphous carbon nanocomposite of the present invention;

Numbers in the figure: 1, upper cover; 2, cathode; 3, valve; 4, anode target; 5, observation window; 6, baffle; 7, copper anode; 8, chuck; 9, graphite crucible; 10, DC pulse power supply; a, cooling water; b, argon; c, hydrogen.

Fig. 2 is the X-ray diffraction (XRD) spectrum of the W ₂ C@onion-like carbon/amorphous carbon nanocomposite prepared in Example 1 of the present invention;

According to the JCPDS PDF card, it can be retrieved that the main phase of the nanocomposite is composed of W ₂ C crystal phase. The broad peak at 2θ≈20° is the characteristic peak of amorphous carbon. Since the onion-like carbon is in the shell, XRD cannot detect the onion-like carbon phase.

3 is a transmission electron microscope (TEM) image of W ₂ C@onion-like carbon/amorphous carbon nanocomposite prepared in Example 1 of the present invention;

It can be seen from the figure that W ₂ C@onion-like carbon nanocapsules are distributed in the amorphous carbon nanosheets, and the particle size of the nanocapsules is 2-15nm.

Fig. 4 is a high-resolution transmission electron microscope image of W ₂ C@onion-like carbon/amorphous carbon nanocomposite prepared in Example 1 of the present invention;

It can be seen from the figure that the obtained W ₂ C@onion-like carbon/amorphous carbon nanocomposite is W ₂ C@onion-like carbon nanocapsules embedded in amorphous carbon nanosheets, wherein, W ₂ C@onion-like carbon nanocapsules The inner core is W ₂ C nanoparticles, and the outer shell is onion-like carbon.

Fig. 5 is a cycle discharge curve diagram of the W ₂ C@onion-like carbon/amorphous carbon nanocomposite prepared in Example 1 of the present invention as the negative electrode material;

It can be seen from the figure that the charge-discharge cycle test is carried out at a current of 100mA/g, and the discharge capacity after 100 cycles is 835.8mAh/g.

Fig. 6 is a cycle discharge curve diagram of the W ₂ C@onion-like carbon/amorphous carbon nanocomposite prepared in Example 2 of the present invention as the negative electrode material;

It can be seen from the figure that the charge-discharge cycle test is carried out at a current of 100mA/g, and the discharge capacity after 100 cycles is 842mAh/g.

detailed description

The present invention will be further described below in conjunction with the examples, but the present invention is not limited to the following examples.

Example 1

Open the upper cover 1 of the device shown in Figure 1, use graphite as the cathode 2 and fix it on the chuck 8, the composition of the anode target 4 consumed is a block made of pure tungsten powder and coal powder (mass ratio 50:50) The body is placed on the copper anode 7 passing through the cooling water, and the graphite crucible 9 is between the copper anode passing through the cooling water and the target. A distance of 30 mm is maintained between the cathode graphite electrode and the 4 anode target tungsten-coal powder blocks. Cover the upper cover 1 of the device, pass cooling water a, and after the whole working chamber is evacuated through the valve 3, argon gas b and hydrogen gas c are introduced. The partial pressure of argon gas is 0.5MPa, and the partial pressure of hydrogen gas is 0.3MPa. Through the DC pulse power supply 10, the voltage is 40V. During the arc discharge process, adjust the working current and voltage to keep relatively stable. The W ₂ C@onion-like carbon/amorphous carbon nanocomposite was prepared, and the microstructure of the nanocomposite was W ₂ C@onion-like carbon core-shell structure nanocapsules embedded in amorphous carbon nanosheets, wherein W ₂ C@onion The particle size of the carbon nanocapsules is 2-15nm, the inner core is W ₂ C nanoparticles, and the outer shell is onion-like carbon, as shown in Fig. 3 and Fig. 4 .

Weigh W ₂ C@ onion-like carbon/amorphous carbon nanocomposite, acetylene black, and vinylidene fluoride in a mass ratio of 7:2:1, put them into a crucible for grinding, then add N-methylpyrrolidone and continue Grind the mixture to make a paste, then apply it evenly on the copper foil, dry it at about 100°C for 12 hours, then roll the copper foil, cut it into discs with a certain diameter, and make electrode sheets; In an argon glove box, the electrode sheet, separator, lithium sheet, and nickel foam were assembled into a button cell by a conventional method. At room temperature, a constant current charge-discharge cycle test was performed at 100mA/g, and after 100 cycles, its capacitance was 835.8mAh/g, as shown in Figure 5. This shows that W ₂ C@onion-like carbon/amorphous carbon nanocomposite It has good cycle performance as the anode material of lithium ion battery.

Example 2

Open the upper cover 1 of the device shown in Figure 1, use graphite as the cathode 2 and fix it on the chuck 8, and the composition of the consumed anode target 4 is a block made of pure tungsten powder and coal powder (mass ratio 30:70) The body is placed on the copper anode 7 passing through the cooling water, and the graphite crucible 9 is between the copper anode passing through the cooling water and the target. A distance of 20 mm is maintained between the cathode graphite electrode and the 4 anode target tungsten-coal powder blocks. Cover the upper cover 1 of the device, pass cooling water a, and after the whole working chamber is evacuated through the valve 3, argon gas b and hydrogen gas c are introduced. The partial pressure of argon gas is 0.5MPa, and the partial pressure of hydrogen gas is 0.3MPa. Through the DC pulsating power supply 10, the voltage is 10V. During the arc discharge process, adjust the working current and voltage to keep relatively stable. The W ₂ C@onion-like carbon/amorphous carbon nanocomposite is prepared, and the microstructure of the nanocomposite is that W ₂ C@onion-like carbon core-shell nanocapsules are embedded in amorphous carbon nanosheets. The W ₂ C@onion-like carbon nanocapsules have a particle diameter of 2-15 nm, the inner core is W ₂ C nano-particles, and the outer shell is onion-like carbon.

Weigh W ₂ C@ onion-like carbon/amorphous carbon nanocomposite, acetylene black, and vinylidene fluoride in a mass ratio of 7:2:1, put them into a crucible for grinding, then add N-methylpyrrolidone and continue Grind the mixture to make a paste, then apply it evenly on the copper foil, dry it at about 100°C for 20 hours, then roll the copper foil, cut it into a circle with a certain diameter, and make an electrode sheet; In an argon glove box, the electrode sheet, separator, lithium sheet, and nickel foam were assembled into a button cell by a conventional method. At room temperature, a constant current charge-discharge cycle test was performed at 100mA/g, and after 100 cycles, its capacitance was 842mAh/g, as shown in Figure 6. This shows that W ₂ C@onion-like carbon/amorphous carbon nanocomposite As a negative electrode material for lithium-ion batteries, it has good cycle performance.

Example 3

Open the upper cover 1 of the device shown in Figure 1, use graphite as the cathode 2 and fix it on the chuck 8, the composition of the anode target 4 consumed is a block made of pure tungsten powder and coal powder (mass ratio 50:50) The body is placed on the copper anode 7 passing through the cooling water, and the graphite crucible 9 is between the copper anode passing through the cooling water and the target. A distance of 30 mm is maintained between the cathode graphite electrode and the 4 anode target tungsten-coal powder blocks. Cover the upper cover 1 of the device, pass cooling water a, and after the whole working chamber is evacuated through the valve 3, argon gas b and hydrogen gas c are introduced. The partial pressure of argon gas is 0.5MPa, and the partial pressure of hydrogen gas is 0.3MPa. Through the DC pulse power supply 10, the voltage is 20V. During the arc discharge process, adjust the working current and voltage to keep relatively stable. The W ₂ C@onion-like carbon/amorphous carbon nanocomposite is prepared, and the microstructure of the nanocomposite is that W ₂ C@onion-like carbon core-shell nanocapsules are embedded in amorphous carbon nanosheets. The W ₂ C@onion-like carbon nanocapsules have a particle diameter of 2-15 nm, the inner core is W ₂ C nano-particles, and the outer shell is onion-like carbon.

Example 4

Open the upper cover 1 of the device shown in Figure 1, use graphite as the cathode 2 and fix it on the chuck 8, the composition of the anode target 4 consumed is a block made of pure tungsten powder and coal powder (mass ratio 40:60) The body is placed on the copper anode 7 passing through the cooling water, and the graphite crucible 9 is between the copper anode passing through the cooling water and the target. A distance of 20 mm is maintained between the cathode graphite electrode and the 4 anode target tungsten-coal powder blocks. Cover the upper cover 1 of the device, pass cooling water a, and after the whole working chamber is evacuated through the valve 3, argon gas b and hydrogen gas c are introduced, the partial pressure of argon gas is 0.2MPa, and the partial pressure of hydrogen gas is 0.2MPa, then connect Through the DC pulse power supply 10, the voltage is 30V. During the arc discharge process, adjust the working current and voltage to keep relatively stable. The W ₂ C@onion-like carbon/amorphous carbon nanocomposite is prepared, and the microstructure of the nanocomposite is that W ₂ C@onion-like carbon core-shell nanocapsules are embedded in amorphous carbon nanosheets. The particle size of W ₂ C@onion-like carbon nanocapsules is 2-15 nm, the core is W ₂ C nanoparticles, and the outer shell is onion-like carbon.

Example 5

Open the upper cover 1 of the device shown in Figure 1, use graphite as the cathode 2 and fix it on the chuck 8, and the composition of the anode target 4 consumed is a block made of pure tungsten powder and coal powder (mass ratio 45:55) The body is placed on the copper anode 7 passing through the cooling water, and the graphite crucible 9 is between the copper anode passing through the cooling water and the target. A distance of 10 mm is maintained between the cathode graphite electrode and the 4 anode target tungsten-coal powder blocks. Cover the upper cover 1 of the device, pass cooling water a, and after the whole working chamber is evacuated through the valve 3, argon gas b and hydrogen gas c are passed in, the partial pressure of argon gas is 0.01MPa, and the partial pressure of hydrogen gas is 0.01MPa, then connect Through the DC pulse power supply 10, the voltage is 40V. During the arc discharge process, adjust the working current and voltage to keep relatively stable. The W ₂ C@onion-like carbon/amorphous carbon nanocomposite is prepared, and the microstructure of the nanocomposite is that W ₂ C@onion-like carbon core-shell nanocapsules are embedded in amorphous carbon nanosheets. The particle size of W ₂ C@onion-like carbon nanocapsules is 2-15 nm, the core is W ₂ C nanoparticles, and the outer shell is onion-like carbon.

Claims (3)

1. A W ₂ C@onion-like carbon/amorphous carbon nanocomposite, characterized in that the microstructure of the nanocomposite is W ₂ C@onion-like carbon core-shell structure nanocapsules embedded in amorphous carbon nanosheets; wherein : The particle size of W ₂ C@onion-like carbon nanocapsule is 2-15nm, the inner core is W ₂ C nano-particles, and the outer shell is onion-like carbon. 2. The preparation method of W ₂ C@onion-like carbon/amorphous carbon nanocomposite as claimed in claim 1, characterized in that: the material is prepared in situ under working gas by using plasma arc discharge technology; wherein : The graphite electrode is used as the cathode, and the tungsten-coal powder block is used as the anode target, and the distance between the cathode graphite electrode and the anode target tungsten-coal powder block is kept at a distance of 2-30mm; the voltage of the arc discharge is 10-40V; the working gas It is argon gas and hydrogen gas; the mass percentage of tungsten in the anode material is 30-50%; the partial pressure of the argon gas is 0.01-0.5MPa, and the partial pressure of the hydrogen gas is 0.01-0.3MPa. 3. The application of the W ₂ C@onion-like carbon/amorphous carbon nanocomposite obtained by the preparation method according to claim 2 as a lithium-ion battery negative electrode material.