CN104934583B - A kind of preparation method of elemental silicon-graphene nanobelt composite material - Google Patents

Abstract

A preparation method of elemental silicon-graphene nanobelt composite material, which is to uniformly mix elemental silicon and a binder to form an elemental silicon suspension. Then, graphene nanobelts are prepared by chemical cutting and ultrasonic stripping of carbon nanotubes, and elemental silicon-graphene nanobelt colloids are prepared by ultrasonic mixing. After drying and heat treatment, composite negative electrode material products are prepared. The invention has the characteristics of simple process, convenient operation, favorable for realizing large-scale production, convenient popularization and application, low energy consumption, low production cost, good production safety and the like, and the elemental silicon-graphene nanobelt prepared by the method of the invention The composite material has the characteristics of strong binding force, excellent electrical conductivity, fast ion diffusion speed, long cycle life, etc. The present invention can be widely used in the preparation of metal element composite materials, and the products prepared by the method of the present invention can be widely used as negative electrode materials. for high-performance lithium-ion batteries.

Description

A kind of preparation method of elemental silicon-graphene nanobelt composite material

technical field

The invention belongs to the technical field of nano-composite material preparation, in particular to a preparation method of elemental silicon-graphene nano-belt composite material in the field of nano-composite material.

Background technique

In recent years, lithium-ion batteries have become a research hotspot due to their high energy density, fast charging and discharging speed, no memory effect, and long service life. At present, lithium-ion batteries generally use graphite as their negative electrode material. However, the low specific capacity of graphite (theoretical capacity of 372 mAh/g) severely limits the performance of lithium-ion batteries. Because of its large specific capacity (theoretical capacity reaches 4200mAh/g), silicon is considered to be the most promising material to replace graphite as the negative electrode of next-generation new lithium-ion batteries. However, silicon has a serious volume effect in the process of charging and discharging. With the progress of lithium ion intercalation and intercalation, the silicon electrode material will be seriously pulverized. At the same time, the conductivity of silicon is low. These two factors greatly limit the Application of silicon as anode material in the field of lithium-ion batteries. Therefore, it is of great practical significance to design a method that can solve these two problems. Graphene nanoribbon is a one-dimensional ribbon graphene. By designing a composite structure of elemental silicon-graphene nanoribbons in which graphene nanoribbons are bundled and wound, the powdering phenomenon of elemental silicon can be well relieved. At the same time, graphite The alkene nanoribbons have good electrical conductivity, which is more conducive to the transport and storage of electrons or ions.

The existing silicon and graphene composite material preparation method is usually to obtain graphene oxide by chemical oxidation of graphite, then to obtain graphene by high temperature exfoliation, and then to obtain modified graphene by plasma treatment, and then to obtain silicon by vapor deposition method. Deposition, that is, a composite material of silicon and graphene is obtained. The main disadvantages of this method are: 1. The method adopts vapor deposition method, which has low yield and high production cost, which is not convenient for popularization and application. ② This method uses silane silicon source, which is expensive and toxic, which is not conducive to mass production. ③ The temperature in this method is high and the energy consumption is large, which is not conducive to energy saving and consumption reduction, and the practical application is limited. ④ The product graphene obtained by this method is not tightly combined with elemental silicon, so that elemental silicon is still relatively easy to powder and fall off during the electrochemical reaction process, which affects the cycle stability and service life.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a preparation method of elemental silicon-graphene nanobelt composite material in view of the deficiency of the existing silicon and graphene composite material preparation method, which has the advantages of convenient operation, low production cost, green and non-toxic and the like; the present invention The elemental silicon-graphene nanobelt composite material prepared by the method has a stable structure, and there is electrostatic adhesion between the two. The electrostatic adhesion of the graphene nanobelt on the surface of elemental silicon can significantly improve the transmission rate of electrons and lithium ions. Thus, the lithium intercalation activity and service life of lithium ions are enhanced, and the material can be used as a negative electrode material for high-power lithium ion batteries.

The technical scheme for realizing the object of the present invention is: a preparation method of elemental silicon-graphene nanobelt composite material, using elemental silicon and carbon nanotubes as raw materials, firstly, elemental silicon is mixed with a binder to obtain a silicon suspension secondly, the graphene nanobelts are prepared by chemical cutting and ultrasonic exfoliation; then, elemental silicon-graphene nanobelt colloids are prepared by ultrasonic mixing; finally, elemental silicon-graphene nanobelt composites are prepared by heat treatment. The specific steps of the method are as follows:

1) Preparation of elemental silicon suspension

Add the elemental silicon material into deionized water and stir for 0.5 to 12 hours to obtain a suspension of elemental silicon. The concentration of elemental silicon in the deionized water is 0.001-0.01 g/mL; then add a binder to the suspension and ultrasonically for 10- 300min to obtain a uniform elemental silicon suspension. The mass ratio of the binder to the elemental silicon is 1:0.1-50.

2) Preparation of graphene nanoribbons

2.1) The graphitized carbon nanotubes are added to the oxidizing acid and stirred for 1-24 h to prepare mixture I.

2.2) Then add transition metal oxidation assistant to mixture I, stir at room temperature for 0.1 to 5 h, then transfer to a water bath, and then stir at a constant temperature of 50 to 90 ° C for 1 to 10 h to obtain mixture II; step 2.1) The concentration of the carbon nanotubes in the strong oxidizing acid described in step 2.1) is 0.0005-0.02 g/mL, and the transition metal oxidation assistant described in step 2.2) is in the strong oxidizing acid described in step 2.1). The concentration in 0.0005-0.2g/mL;

2.3) Add hydrogen peroxide and deionized water with a mass fraction of 30% to mixture II, and mix and react for 0.5-3 h to obtain mixture III; the volume of the hydrogen peroxide, the volume of the deionized water, and the volume of the oxidizing acid The ratio is 1:5-20:0.5-5.

2.4) ultrasonically clean mixture III with hydrochloric acid with a mass fraction of 2 to 5%; the frequency of ultrasonics is 20-1000 Hz, the time is 10 to 300 min, and the number of cleanings is 2 to 5 times, and then repeated centrifugal cleaning with deionized water After being neutralized, the graphene nanoribbons are prepared by drying at 60-150° C. for 6-24 hours.

3) Preparation of elemental silicon-graphene nanoribbon composites

Adding the graphene nanoribbons in step 2.4) to the elemental silicon suspension in step 1), the mass ratio of the graphene nanoribbons to the elemental silicon in step 1) is 1:0.1-20, and then at 50- After ultrasonic vibration at a frequency of 1000Hz for 30-240min, an elemental silicon-graphene nanobelt adhesive was prepared, and the colloid was dried at 60-150°C for 6-24h, and the heating rate was 2-5°C/min. , heating up to a sintering temperature of 200-600° C., and sintering for 1-10 hours under the protection of an inert atmosphere to obtain an elemental silicon-graphene nanobelt composite material.

After the present invention adopts the above-mentioned technical scheme, it mainly has the following effects:

1. The method of the present invention has few steps in the production process, low temperature, and does not involve the use of toxic raw materials, so the energy consumption is low, the production safety is good, the production cost is low, and it is environmentally friendly.

2. The method of the present invention adopts processes such as chemical oxidation, mechanical stirring, ultrasonic dispersing and mixing, the process is simple, the operation is convenient, it is beneficial to realize large-scale production, and it is convenient for popularization and application;

3. The method of the present invention can directly adopt commercialized elemental silicon material, which is beneficial to be directly put into large-scale production;

4. The elemental silicon-graphene nanobelt composite material prepared by the method of the present invention, due to the unique band-like structure of the graphene nanobelt, can not only be closely combined with elemental silicon, but also form tiny gaps and defects in the nanobelt itself. , so that the prepared composite has the excellent properties of high conductivity and good ion transport performance at the same time, so that it has the characteristics of excellent rate performance and so on;

5. The elemental silicon-graphene nanobelt composite material prepared by the present invention, because the graphene nanobelt can be flexibly adhered to the elemental silicon in a winding manner, and there is electrostatic adhesion between the two, which can effectively prevent the silicon The pulverization phenomenon improves the electrochemical performance of the electrode material.

The invention is widely used for preparing graphene nanobelt composite materials, and the elemental silicon-graphene nanobelt composite materials prepared by the method of the invention can be widely used in high-power lithium ion batteries.

Description of drawings

1 is a SEM image of the elemental silicon-graphene nanoribbon composite material prepared in Example 1.

FIG. 2 is an enlarged view of FIG. 1 .

In the figure, 1 is elemental silicon, and 2 is graphene nanoribbons.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

Example 1

The concrete steps of a kind of preparation method of elemental silicon-graphene nanobelt composite material are as follows:

1) Preparation of elemental silicon suspension

The elemental silicon material was added to deionized water and stirred for 3 hours to obtain a suspension of elemental silicon. The concentration of elemental silicon in deionized water was 0.002 g/mL, and then glucose was added to the suspension for 90min to obtain a uniform elemental silicon. suspension. The mass ratio of the glucose to the elemental silicon is 1:10.

2) Preparation of graphene nanoribbons

2.1) The graphitized carbon nanotubes were added to the concentrated sulfuric acid and stirred for 12h to obtain mixture I,

2.2) Then potassium permanganate was added to mixture I, stirred at room temperature for 1 hour, then transferred to a water bath, and stirred at a constant temperature of 80°C for 4 hours to prepare mixture II; the carbon nanotubes described in step 2.1) were in The concentration in the strong oxidizing acid described in step 2.1) is 0.0025g/mL, and the concentration of the transition metal oxidation assistant described in step 2.2) in the strong oxidizing acid described in step 2.1) is 0.0125g/mL;

2.3) Add hydrogen peroxide and deionized water with a mass fraction of 30% to mixture II, and mix and react for 3h to obtain mixture III; the volume ratio of the hydrogen peroxide, the deionized water, and the oxidizing acid is 1: 10:2.

2.4) Perform ultrasonic cleaning on mixture III with hydrochloric acid with a mass fraction of 3%. The frequency of ultrasonic is 100 Hz, the time is 30 to 300 min, and the number of cleanings is 3 times. After drying at 80 °C for 12 h, graphene nanoribbons were obtained.

3) Preparation of elemental silicon-graphene nanoribbon composites

The graphene nanoribbon described in step 2.4) is added to the obtained elemental silicon suspension in step 1), and the mass ratio of the graphene nanoribbon to the elemental silicon in step 1) is 1:2, and then at a frequency of 100Hz After ultrasonic vibration for 120 min, the elemental silicon-graphene nanobelt adhesive was prepared. The colloidal substance was dried at 120 °C for 12 h, and heated to a sintering temperature of 400 °C at a heating rate of 3 °C/min, protected by an inert atmosphere. Elemental silicon-graphene nanobelt composites were prepared by sintering for 3 h under the same conditions.

Example 2

A preparation method of elemental silicon-graphene nanobelt composite material, with embodiment 1, wherein:

In step 1), the stirring time is 0.5h, the concentration of elemental silicon in deionized water is 0.01g/mL, and the binder is added for ultrasonic 10min, and the mass ratio of the binder to the elemental silicon is 1:0.1.

In the second step, the transition metal oxidation assistant is osmium tetroxide, and the concentrated sulfuric acid is an oxidizing acid. The graphitized carbon nanotubes are added to the strong oxidizing acid and the stirring time is 1h, and the stirring time is 0.1h at room temperature. The temperature is 50°C, and the stirring time of the water bath is 1h; the concentration of the mass of the carbon nanotubes in the strong oxidizing acid is 0.02 g/mL, and the transition metal oxidation assistant is in the strong oxidizing acid. The concentration in 0.02g/mL;. Add hydrogen peroxide and deionized water to mixture II, and the mixing reaction time is 0.5h; the volume ratio of the volume of hydrogen peroxide, the volume of deionized water, and the oxidizing acid is 1:5:0.5. The mass fraction of hydrochloric acid used is 2%, and the mixture III is sonicated at a frequency of 20 Hz, a time of 10 min, a cleaning frequency of 2 times, a drying temperature of 60° C., and a drying time of 6 h.

In step 3), the ultrasonic frequency is 50Hz, the ultrasonic time is 30min, the drying temperature is 60°C, the drying time is 6h, the heating rate is 2°C/min, the sintering temperature is 200°C, the sintering time is 1h, and the graphene nanoribbons The mass ratio of elemental silicon in step 1) is 1:0.1.

Example 3

A preparation method of elemental silicon-graphene nanobelt composite material, with embodiment 1, wherein:

In step 1), the stirring time was 12h, the concentration of elemental silicon in deionized water was 0.001 g/mL, and the binder was added for ultrasonic 300min, and the mass ratio of the binder to elemental silicon was 1:50.

2) The transition metal oxidation assistant is potassium ferrate, and perchloric acid is an oxidizing acid. The graphitized carbon nanotubes are added to the strong oxidizing acid for a stirring time of 24 hours, and the stirring time at room temperature is 5 hours. The water bath temperature is 90° C., the stirring time of the water bath is 1-10 h; the mass concentration of the carbon nanotubes in the strong oxidizing acid is 0.1 g/mL, and the transition metal oxidation assistant is in the strong oxidizing acid. The concentration in 0.005g/mL;. Add hydrogen peroxide and deionized water to mixture II, and the mixing reaction time is 0.5h; the volume ratio of the volume of hydrogen peroxide, the volume of deionized water, and the oxidizing acid is 1:20:5. The mass fraction of hydrochloric acid used was 5%, and the mixture III was sonicated at a frequency of 1000 Hz, a time of 300 min, a cleaning frequency of 5 times, a drying temperature of 150° C., and a drying time of 24 h.

In step 3), the ultrasonic frequency is 1000Hz, the ultrasonic time is 240min, the drying temperature is 150°C, the drying time is 24h, the heating rate is 5°C/min, the sintering temperature is 600°C, and the sintering time is 10h. The mass ratio of the mass to the elemental silicon in step 1) is 1:20.

test results

The positive electrode composite material prepared in Example 1 is used for scanning electron microscope observation, and its electron microscope images are shown in FIG. 1 and FIG. 2 , wherein FIG. 2 is an enlarged view of FIG. 1 . It can be seen from the analysis of the test results that the elemental silicon particles of the elemental silicon-graphene nanobelt composite product obtained in Example 1 are evenly bound and wound by the nanobelts to form a three-dimensional network structure, and the graphene nanobelts are not only closely combined with the elemental silicon particles, thereby This structure is not only beneficial to prevent the pulverization of elemental silicon during charging and discharging, but also improves the conductivity of elemental silicon and facilitates the transport of lithium ions, thereby improving the electrochemical performance of elemental silicon.

Claims (2)

1. The preparation method of the elemental silicon-graphene nanoribbon composite material is characterized by comprising the following steps of:

1) preparation of elemental silicon suspensions

Adding the simple substance silicon material with the particle size of less than 300nm into deionized water, and stirring for 0.5-12 h to obtain a suspension of the simple substance silicon, wherein the concentration of the simple substance silicon in the deionized water is 0.001-0.01 g/mL; then adding a binder into the suspension, and carrying out ultrasonic treatment for 10-300 min at the frequency of 20-1000Hz to prepare a uniform simple substance silicon suspension; the mass ratio of the binder to the simple substance silicon is 1: 0.1-50;

2) preparation of graphene nanoribbons

2.1) adding the graphitized carbon nano tube into strong oxidizing acid and stirring for 1-24 hours to prepare a mixture I;

2.2) adding a transition metal oxidation auxiliary agent into the mixture I, stirring at room temperature for 0.1-5 h, transferring into a water bath kettle, and stirring at a constant temperature of 50-90 ℃ for 1-10 h to obtain a mixture II; the concentration of the carbon nano tube in the step 2.1) in the strong oxidizing acid in the step 2.1) is 0.0005-0.02g/mL, and the concentration of the transition metal oxidation auxiliary agent in the step 2.2) in the strong oxidizing acid in the step 2.1) is 0.0005-0.2 g/mL;

2.3) adding 30 percent by mass of hydrogen peroxide and deionized water into the mixture II, and mixing and reacting for 0.5-3h to obtain a mixture III; the volume ratio of the hydrogen peroxide to the deionized water to the strong oxidizing acid is 1: 5-20: 0.5-5;

2.4) carrying out ultrasonic cleaning on the mixture III by using hydrochloric acid with the mass fraction of 2-5%; the ultrasonic frequency is 20-1000Hz, the time is 10-300 min, the cleaning frequency is 2-5 times, then deionized water is used for repeatedly centrifugally cleaning the mixture to be neutral under the condition that the rotating speed is 1000-15000 r/s, and then the mixture is dried for 6-24 hours at the temperature of 60-150 ℃ to prepare the graphene nanoribbon;

3) preparation of elemental silicon-graphene nanoribbon composite

Adding the graphene nanoribbons obtained in the step 2.4) into the elemental silicon suspension obtained in the step 1), wherein the mass ratio of the graphene nanoribbons to the elemental silicon in the step 1) is 1: 0.1-20; performing ultrasonic oscillation at the frequency of 50-1000 Hz for 30-240 min to obtain simple substance silicon-graphene nanoribbon jelly; drying the jelly at 60-150 ℃ for 6-24 h, heating to a sintering temperature of 200-600 ℃ at a heating rate of 2-5 ℃/min, and sintering in an inert atmosphere for 1-10 h to obtain the elemental silicon-graphene nanoribbon composite material.

2. The method for preparing the elemental silicon-graphene nanoribbon composite material according to claim 1, wherein the method comprises the following steps:

the transition metal oxidation auxiliary agent in the step 2.2) is selected from one or more of potassium permanganate, sodium permanganate, potassium ferrate, sodium ferrate and osmium tetroxide;

the strong oxidizing acid in the step 2.1) is selected from one of concentrated sulfuric acid, concentrated nitric acid, oxyacid of chlorine, oxyacid of bromine or oxyacid of iodine;

the binder in the step 1) is selected from one or more of polyethylene, polypropylene, polyvinyl acetate, polyvinyl chloride, polyacrylonitrile, polybutadiene, polyvinyl formal, polytetrafluoroethylene, polymethyl methacrylate, glucose, sucrose, polymethyl cellulose or polyethyl cellulose.

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