CN103022451B - Nano silicon particles filled carbon nano tube compound as well as preparation method and application thereof - Google Patents

Abstract

The invention relates to the field of negative electrode materials for lithium-ion batteries, in particular to a carbon nanotube composite filled with nano-silicon particles and its preparation method and application. The filling amount and size are precisely controllable, and the filling compound is used for high-performance lithium-ion battery anode materials. Among them, the weight ratio of nano-silicon particles is accurately and controllable between 2-50wt%, the size of nano-silicon particles is precisely and controllable in the range of 1-25nm, and the size of carbon nanotubes filled with silicon particles is between 10-100nm Uniform and precisely controllable across the range. Silicon particles are controllably filled in the hollow cavity of carbon nanotubes for lithium battery negative electrodes, which solves the problems of low coulombic efficiency and poor cycle performance caused by the difficulty in controlling the particle size of silicon and large volume expansion when used in lithium battery negative electrodes. . When the composite is used as a negative electrode material for a lithium ion battery, it exhibits higher lithium storage capacity, higher Coulombic efficiency and longer cycle life.

Description

A kind of nano-silicon particle filled carbon nanotube composite and its preparation method and application

technical field

The invention relates to the field of negative electrode materials for lithium-ion batteries, in particular to a composite of nano-silicon particles filled in carbon nanotubes and its preparation method and application. The controllable filling of nano-silicon particles in the hollow lumen of carbon nanotubes, The filling amount and size of silicon particles are precisely controllable, and the filling composite can be used as anode material for high-performance lithium-ion batteries.

Background technique

Lithium-ion rechargeable batteries are commonly used as energy storage devices. Compared with lead-acid batteries and nickel-cadmium batteries, they have the characteristics of higher voltage, high energy density, long service life, environmental friendliness and no memory effect. Since Since its commercialization, it has played a pivotal role and has been widely used in mobile electronic devices, communication equipment and backup power supplies. With the rapid development of electric vehicles and hybrid vehicles, lithium-ion batteries are considered to be ideal candidates for the power system of electric vehicles due to their unique advantages. High power density, high energy density and long service life have become the most urgent problems to be solved in the research and development of lithium-ion batteries for electric vehicles at this stage. The performance of energy storage devices largely depends on the properties of the materials used. As far as anode materials are concerned, traditional graphite anodes are difficult to meet the ever-increasing application requirements due to their low theoretical specific capacity (372mAh/g), so the development of new high-capacity anode materials has become an important trend. Silicon has a theoretical specific capacity of 4200mAh/g when alloyed with lithium, and has become the most potential anode material for next-generation lithium-ion batteries. However, when silicon materials are used in the negative electrode of lithium-ion batteries, the volume of silicon will change drastically (300-400%) due to the intercalation and extraction of lithium, which will cause silicon to break, pulverize, and separate from the electrode collector, resulting in Rapid capacity decay. Therefore, effectively solving the volume expansion problem when silicon is used in the negative electrode of lithium-ion batteries has become one of the hot issues in the current lithium-ion battery negative electrode research. In recent years, with the rise and development of nanotechnology, nanomaterials have begun to play an important role in electrochemical energy storage, that is, through the nanostructure design of materials, the power density, energy density and cycle life of lithium-ion batteries can be improved.

Carbon nanotubes can be regarded as quasi-one-dimensional nanomaterials formed by curling graphene sheets, which have excellent properties such as good electrical conductivity, high chemical stability, high strength, and good flexibility. Recent studies have shown that the unique nano-confinement effect of the hollow cavity of carbon nanotubes can ensure that the lithium storage active material filled in the hollow cavity is at the nanometer scale, and can limit the volume expansion of the active material during lithium intercalation, preventing its Pulverization and exfoliation when deintercalating lithium, so that the electrode maintains high capacity and good cycle stability (Document 1, Yong Wang, Minghong Wu, ZhengJiao, Jim Yang Lee, Chem.Mater.21:3210-3215(2009 ) Document 2, Yu, Wan-Jing, Hou, Peng-Xiang, Li, Feng, Liu, Chang J. Mater. Chem.22:13756-13763 (2010) Document 3, Hongkun Zhang, Huaihe Song, Xiaohong Chen, Jisheng Zhou J. Phys. Chem. C 116:22774-22779 (2012)). However, it is difficult to selectively fill silicon into the hollow cavity of carbon nanotubes, and so far there are few reports on the selective filling of silicon into the hollow cavity of carbon nanotubes and its lithium storage performance. The only work (J.Am.Chem.Soc., 2010, 132(25), pp 8548-8549) is to deposit silicon in carbon nanotubes prepared by the anodized aluminum template method with a diameter of 300nm to prepare coaxial carbon /silicon tube, and found that the composite has excellent lithium storage performance. However, such ultra-large-diameter carbon nanotubes are no longer suitable for studying nanometer-sized spatial effects, and what is filled is coaxial silicon tubes. Therefore, selectively filling silicon particles in small-diameter (less than 100nm) carbon nanotubes, and realizing precise control of silicon filling amount and particle size, is of great importance for studying the influence of carbon nanotubes on the performance of lithium storage and storage of silicon nanoparticles and high-performance lithium-ion batteries. The research and development of anode materials is of great significance.

Contents of the invention

The object of the present invention is to provide a nano-silicon particle-filled carbon nanotube composite and its preparation method and application. The silicon particles can be controllably filled in the hollow cavity of the carbon nanotube for the negative electrode of lithium batteries, which solves the problem that it is currently difficult to control silicon The particle size and the large volume expansion when used in lithium battery negative electrodes cause problems such as low Coulombic efficiency and poor cycle performance.

Technical scheme of the present invention is:

A carbon nanotube composite filled with nano-silicon particles, wherein the nano-silicon particles are controllably filled in the hollow cavity of the carbon nanotube to form a composite; wherein the weight of the nano-silicon particles can be accurately controlled between 2-50wt%. The size of nano-silicon particles is precisely controllable in the range of 1-25nm, and the inner diameter of the hollow lumen of carbon nanotubes filled with silicon particles is uniform and precisely controllable in the range of 10-100nm.

In the carbon nanotube composite filled with nano-silicon particles, preferably, the weight of the nano-silicon particles is accurately controllable between 10-30wt%, and the size of the nano-silicon particles is accurately controllable within the range of 5-15nm. The size of carbon nanotubes with silicon particles is uniform and precisely controllable in the range of 30-60nm.

The preparation method of the nano-silicon particle-filled carbon nanotube composite uses an anodic aluminum oxide film with a regular pore structure as a template, and in a protective gas, through carbon chemical vapor deposition, the nanopores of the anodic aluminum oxide film are first Crack organic low-carbon hydrocarbons to deposit a carbon layer on the inner surface of the inner surface; then use silane as a silicon source, in a protective gas, chemical vapor deposition of silicon in the alumina/carbon nanochannel, so that in the anodized alumina channel after the carbon layer is deposited Silicon particles are uniformly formed; finally, the anodized aluminum template is removed to obtain a carbon nanotube composite filled with silicon particles in the hollow lumen.

In the preparation method of the carbon nanotube composite filled with nano-silicon particles, the anodic aluminum oxide film is prepared by electrolysis of sulfuric acid or oxalic acid, with a pore diameter of 10-100 nanometers, a length of 50 nanometers-200 microns, and openings at both ends.

The preparation method of the nano-silicon particle-filled carbon nanotube composite uses protective gas: nitrogen, argon or helium as the carrier gas, the carbon chemical vapor deposition temperature is 600-900°C, and the total gas flow rate is 100-500ml /min, wherein the volume concentration of organic low-carbon hydrocarbons is 1-20%, and the deposition time is 0.5-6 hours.

In the preparation method of the nano-silicon particle-filled carbon nanotube composite, the organic low-carbon hydrocarbon is ethylene, acetylene or propylene, and the thickness of the carbon layer formed by cracking the organic low-carbon hydrocarbon on the surface of the anodic aluminum oxide film and the inner surface of the channel is 5-20 nanometers.

The preparation method of the nano-silicon particle-filled carbon nanotube composite uses protective gas: nitrogen, argon, helium or hydrogen as the carrier gas, the silicon chemical vapor deposition temperature is 500-700 ° C, and the total gas flow rate is 50 -500ml/min, wherein the volume concentration of silane is 2-50%, the deposition time is 2-30min, and the deposition pressure is 1-760torr.

The application of the nano-silicon particle-filled carbon nanotube composite is to use the carbon nanotube composite filled with nano-silicon particles as a negative electrode and assemble it into a lithium-ion battery. When the composite is used as a lithium-ion battery negative electrode material, the performance High lithium storage capacity, high coulombic efficiency and long cycle life, among which the lithium storage capacity is 500-2000mAh/g, the coulombic efficiency is >95%, and the cycle life is 16-50 weeks.

The application of the nano-silicon particle-filled carbon nanotube composite, the high lithium storage capacity, high coulombic efficiency, and long cycle life of the lithium-ion battery are determined by the structure of the material, wherein the nano-silicon particles contribute high lithium storage capacity , carbon nanotube hollow lumen and elastic tube wall provide volume expansion and contraction space and lithium ion transport channel for silicon particles.

With the application of the carbon nanotube composite filled with nano-silicon particles, lithium ions can be transported through the carbon layer of the carbon nanotube wall, and the elastic tube wall diameter of the carbon nanotube can expand to 130%.

The advantages of the present invention are:

1. The present invention provides a controllable filling of nano-silicon particles in the hollow cavity of carbon nanotubes and a method for the negative electrode of a high-performance lithium-ion battery, which can realize completely controllable filling of silicon particles in small-diameter carbon nanotubes In the hollow lumen of silicon, it effectively solves the volume expansion, pulverization and detachment of silicon from the electrode current collector during lithium intercalation, which leads to rapid capacity fading and poor Coulombic efficiency.

2. The carbon nanotubes filled with silicon particles prepared by the present invention can accurately control the content and size of silicon by optimizing the reaction temperature, total gas flow, silane concentration and reaction time during chemical vapor deposition. The weight percentage of silicon particles is in It can be precisely controlled between 2-50wt%, and the size of silicon particles can be controlled within the range of 1-25nm.

3. The carbon nanotubes filled with silicon controllable prepared by the method of the present invention are pure and free of impurity components, and when used in the negative electrode of a lithium ion battery, show a lithium storage capacity much higher than that of the negative electrode of graphite.

4. The present invention explains that the hollow lumen and elastic tube wall of carbon nanotubes provide space for volume expansion and contraction and lithium ion transport channels for silicon particles, and lithium ions can be transported through the carbon layer of the carbon nanotube wall. The elastic walls of the tube can expand up to 130%.

5. In the present invention, the carbon nanotube composite filled with nano-silicon particles is used as the negative electrode and assembled into a lithium-ion battery. Its lithium storage capacity can be as high as 1920mAh/g, which is 5 times higher than that of the graphite negative electrode of 372mAh/g, and has High Coulombic efficiency and long cycle life. When carbon nanotubes filled with silicon particles are used as anode materials for lithium-ion batteries, they exhibit much higher lithium storage capacity than graphite anodes, higher Coulombic efficiency and longer cycle life.

Description of drawings

Fig. 1. The transmission picture of the controllable filling of nano-silicon particles in the hollow lumen of carbon nanotubes in Example 1.

Fig. 2. The transmission photograph of the controllable filling of nano-silicon particles in the hollow lumen of carbon nanotubes in Example 2.

Figure 3. The cycle performance curve of the carbon nanotubes filled with nano-silicon particles of Example 2 as the negative electrode material of lithium-ion batteries.

Figure 4. The cycle performance curve of the pure nano-silicon particles of Comparative Example 1 as the negative electrode material of lithium-ion batteries.

Detailed ways

The present invention is described in detail below by way of examples.

Example 1.

High-purity (purity above 99.8wt%) aluminum sheet uses 3wt% oxalic acid solution as the electrolyte, anodizes at 20°C and 40V for 4 hours to prepare holes at both ends, with a thickness of 40 microns and a pore size of 50 A nano-anodized aluminum oxide film was used as a template. After the anodized aluminum template was dried, the chemical vapor deposition of acetylene was carried out at 650°C for 2 hours, using nitrogen as the carrier gas, the total flow rate of the reaction gas was 200ml/min, the volume concentration of acetylene gas was 10%, and the thickness of the deposited carbon layer was 6 Nano. The carbon-deposited anodized aluminum template was subjected to chemical vapor deposition of silane at 500°C for 5 minutes, using argon as the carrier gas, the total flow rate of the reaction gas was 50ml/min, and the volume concentration of silane was 2%. Use 10wt% phosphoric acid solution to remove the aluminum oxide template after silicon deposition to obtain carbon nanotubes with silicon particles completely and uniformly filled in the hollow lumen. The inner diameter of the hollow lumen of the carbon nanotubes filled with silicon particles is 38 nanometers . As shown in Figure 1, the content of filled silicon is about 5wt%, and the size distribution of silicon particles is 3-8 nanometers, concentrated at 6 nanometers. When used in the negative electrode of lithium particle batteries, it has a lithium storage capacity of 600mAh/g and a coulombic efficiency. Above 95%, after 16 weeks of circulation, the reversible capacity retention rate is 99.7%.

In this embodiment, the high lithium storage capacity, high coulombic efficiency, and long cycle life of lithium-ion batteries are determined by the structure of the material, in which nano-silicon particles contribute to high lithium storage capacity, carbon nanotube hollow lumen and elastic tube The walls provide spaces for volume expansion and contraction and lithium ion transport channels for silicon particles. Lithium ions can be transported through the carbon layer of the carbon nanotube wall, and the diameter of the elastic wall of the carbon nanotube hardly changes.

Example 2.

The preparation method of the anodized aluminum template is the same as in Example 1. The difference is that the anodic oxidation voltage is 45V, and the pore size of the prepared anodized alumina template is: 65 nanometers. After the alumina template is dried, the chemical vapor deposition of ethylene is carried out at 700 ° C for 2 hours, nitrogen is used as the carrier gas, and the reaction gas is The total flow rate is 200ml/min, the volume concentration of ethylene gas is 5%, and the thickness of the deposited carbon layer is 6 nm. The carbon-deposited anodized aluminum template was subjected to chemical vapor deposition of silane at 600°C for 20 minutes, hydrogen was used as the carrier gas, the total flow rate of the reaction gas was 100ml/min, and the volume concentration of silane was 2%. A 10wt% phosphoric acid solution is used to remove the aluminum oxide template after silicon deposition to obtain carbon nanotubes in which silicon particles are completely and uniformly filled in hollow tube lumens. As shown in Figure 2, the inner diameter of the hollow lumen of carbon nanotubes filled with silicon particles is 53 nanometers, the content of silicon filling is about 40%, and the size distribution of silicon particles is 18-22 nanometers, concentrated at 20 nanometers. As shown in Figure 3, it has a lithium storage capacity of 1650mAh/g when used in the negative electrode of a lithium ion battery, and its coulombic efficiency is above 95%. After 16 weeks of cycling, its reversible capacity retention rate is 99.1%.

In this embodiment, the high lithium storage capacity, high coulombic efficiency, and long cycle life of lithium-ion batteries are determined by the structure of the material, in which nano-silicon particles contribute to high lithium storage capacity, carbon nanotube hollow lumen and elastic tube The walls provide spaces for volume expansion and contraction and lithium ion transport channels for silicon particles. Lithium ions can be transported through the carbon layer of the carbon nanotube wall, and the elastic wall diameter of the carbon nanotube can expand by up to 130%.

Example 3.

The preparation method of the anodized aluminum template is the same as in Example 1, except that the anodic oxidation voltage is 60V, and the pore size of the prepared anodized aluminum template is: 100nm. After the aluminum oxide template is dried, chemical vapor deposition of acetylene is carried out at 700°C. For 2 hours, argon is used as the carrier gas, the total flow rate of the reaction gas is 300ml/min, the volume concentration of acetylene gas is 10%, and the thickness of the deposited carbon layer is 15 nm. The carbon-deposited anodized aluminum template was subjected to chemical vapor deposition of silane at 550°C for 30 minutes, using hydrogen as the carrier gas, the total flow rate of the reaction gas was 50ml/min, and the volume concentration of silane was 5%. A 10wt% phosphoric acid solution was used to remove the silicon-deposited alumina template to obtain carbon nanotubes filled with silicon particles uniformly in the hollow lumen, and the inner diameter of the hollow lumen of the carbon nanotubes filled with silicon particles was 70nm. The content of filled silicon is about 50%, and the size distribution of silicon particles is 23-28 nanometers, concentrated at 25 nanometers. When used in the negative electrode of lithium particle batteries, it has a lithium storage capacity of 1920mAh/g, and the Coulombic efficiency is above 95%. After 16 weeks, the reversible capacity retention rate was 99%.

In this embodiment, the high lithium storage capacity, high coulombic efficiency, and long cycle life of lithium-ion batteries are determined by the structure of the material, in which nano-silicon particles contribute to high lithium storage capacity, carbon nanotube hollow lumen and elastic tube The walls provide spaces for volume expansion and contraction and lithium ion transport channels for silicon particles. Lithium ions can be transported through the carbon layer of the carbon nanotube wall, and the elastic wall diameter of the carbon nanotube can expand up to 120%.

Example 4.

High-purity (purity above 99.8wt%) aluminum sheet is prepared by anodizing 10wt% sulfuric acid solution for 2 hours at 10°C and 20V to obtain openings at both ends with a thickness of 30 microns and a pore size of 30 nm anodized aluminum film as a template. After the anodized aluminum template was dried, chemical vapor deposition of ethylene was carried out at 800°C for 1 hour, using nitrogen as the carrier gas, the total flow rate of the reaction gas was 300ml/min, the volume concentration of ethylene gas was 2%, and the thickness of the deposited carbon layer was 5 Nano. The carbon-deposited anodized aluminum template was subjected to chemical vapor deposition of silane at 700°C for 20 minutes, using argon as the carrier gas, the total flow rate of the reaction gas was 200ml/min, and the volume concentration of silane was 5%. Use 10wt% phosphoric acid solution to remove the aluminum oxide template after silicon deposition, to obtain carbon nanotubes with silicon particles completely uniformly filled in the hollow lumen, and the inner diameter of the hollow lumen of the carbon nanotubes filled with silicon particles is 20 nanometers . The content of filled silicon is about 18%, and the size distribution of silicon particles is 8-12 nanometers, concentrated in 10 nanometers. When used in the negative electrode of lithium particle batteries, it has a lithium storage capacity of 1090mAh/g, and the Coulombic efficiency is above 95%. After 16 weeks, the reversible capacity retention rate was 99.3%.

In this embodiment, the high lithium storage capacity, high coulombic efficiency, and long cycle life of lithium-ion batteries are determined by the structure of the material, in which nano-silicon particles contribute to high lithium storage capacity, carbon nanotube hollow lumen and elastic tube The walls provide spaces for volume expansion and contraction and lithium ion transport channels for silicon particles. Lithium ions can be transported through the carbon layer of the carbon nanotube wall, and the elastic wall diameter of the carbon nanotube can expand up to 109%.

Comparative example 1.

When commercial silicon powder with an average particle size of 20 nm is used as an anode material for lithium-ion batteries, it exhibits poor cycle life and coulombic efficiency, as shown in Figure 4. Although the reversible capacity of 2600mAh/g was presented for the first time, its cycle stability is very poor. After 20 cycles, the specific capacity decays sharply, which is lower than the theoretical capacity of 372mAh/g of graphite anode material.

In this comparative example, pure nano-silicon particles with similar particle sizes showed completely opposite lithium storage performance, which further verified the volume expansion and The confining effect of shrinking space.

The results of the examples show that the present invention can controllably fill silicon nanoparticles in the hollow lumen of carbon nanotubes by controlling the preparation conditions of the anodized aluminum oxide template, the conditions of chemical vapor deposition of carbon, and the conditions of chemical vapor deposition of silicon. Content and particle size are precisely controllable. When this material is used as an anode material for lithium-ion batteries, it shows a much higher lithium storage capacity than graphite anodes and a much higher coulombic efficiency and cycle life than pure silicon powder, which can be used as a potential next-generation high-performance lithium-ion battery anode Material.

Claims (9)

1. a silicon nanoparticle filling carbon nano-pipe compound, is characterized in that: silicon nanoparticle is controllably filled in CNT hollow tube chamber, forms compound; Wherein, the weight shared by silicon nanoparticle is controlled between 2-50 wt%, and the size of silicon nanoparticle is controlled within the scope of 1-25 nm, and the hollow tube chamber internal diameter size being filled with the CNT of silicon grain is even and controlled within the scope of 10-100 nm;

The preparation method of described silicon nanoparticle filling carbon nano-pipe compound, there is the anodic alumina films of regular pore structure as template, in protective gas, by carbon geochemistry vapour deposition, first at the organic lower carbon number hydrocarbons deposited carbon layer of the inner surface cracking of the nano pore of anodic alumina films; Again using silane as silicon source, in protective gas, chemical vapor deposited silicon in aluminium oxide/carbon nano pore, thus evenly form silicon grain in anodised aluminium duct after deposited carbon layer; Finally remove anodic oxidation aluminium formwork, thus obtain the carbon mano-tube composite being filled with silicon grain in hollow tube chamber.

2. according to silicon nanoparticle filling carbon nano-pipe compound according to claim 1, it is characterized in that: the weight shared by silicon nanoparticle is controlled between 10-30 wt%, the size of silicon nanoparticle is controlled within the scope of 5-15 nm, and the internal diameter size being filled with the CNT of silicon grain is even and controlled within the scope of 30-60 nm.

3. according to silicon nanoparticle filling carbon nano-pipe compound according to claim 1, it is characterized in that: anodic alumina films is prepared by sulfuric acid or oxalic acid electrolysis, and its aperture is 10-100 nanometer, and length is 50 nanometer-200 microns, both ends open.

4. according to silicon nanoparticle filling carbon nano-pipe compound according to claim 1; it is characterized in that: with protective gas: nitrogen, argon gas or helium are carrier gas; carbon geochemistry vapour deposition temperature is 600-900 oC; total gas couette is 100-500 ml/min; wherein the volumetric concentration of organic lower carbon number hydrocarbons is 1-20%, and sedimentation time is 0.5-6 hour.

5. according to silicon nanoparticle filling carbon nano-pipe compound according to claim 1, it is characterized in that: organic lower carbon number hydrocarbons is ethene, acetylene or propylene, the thickness forming carbon-coating at the organic lower carbon number hydrocarbons of the inner surface cracking in the surface of anodic alumina films and duct is 5-20 nanometers.

6. according to silicon nanoparticle filling carbon nano-pipe compound according to claim 1; it is characterized in that: with protective gas: nitrogen, argon gas, helium or hydrogen are carrier gas; chemistry of silicones vapour deposition temperature is 500-700 oC; total gas couette is 50-500 ml/min; wherein the volumetric concentration of silane is 2-50%; sedimentation time is 2-30 min, and deposition pressure is 1-760 torr.

7. according to the application of silicon nanoparticle filling carbon nano-pipe compound according to claim 1, it is characterized in that: will the carbon mano-tube composite of silicon nanoparticle be filled with as negative pole, be assembled into lithium ion battery, when this compound is used for lithium ion battery negative material, show higher lithium storage content, high coulombic efficiency and long circulation life, wherein lithium storage content is 500-2000 mAh/g, coulombic efficiency >95%, and cycle life is in 16-50 weeks.

8. according to the application of silicon nanoparticle filling carbon nano-pipe compound according to claim 7, it is characterized in that: the lithium storage content that lithium ion battery is high, high coulombic efficiency, long circulation life are by the structures shape of this material, wherein silicon nanoparticle contributes high lithium storage content, and CNT hollow tube chamber and elastic tube wall provide space and the lithium ion transport passage of volumetric expansion and contraction for silicon grain.

9. according to the application of silicon nanoparticle filling carbon nano-pipe compound according to claim 8, it is characterized in that: lithium ion can be transmitted by the carbon-coating of CNT wall, the elastic tube wall diameter expandable to 130% of CNT.