CN114361427A - Method for coating silicon anode material with carbon nanotubes - Google Patents

Abstract

A method for coating a silicon cathode material with a carbon nano tube comprises the following steps: a. taking the components in a weight ratio of 0.1-2: feeding 99.9-98 parts of carbon nano tube powder and silicon negative electrode material powder into coating equipment; b. starting coating equipment, and running for 1-20 minutes at a rotating speed of 3-40 m/s to enable the carbon nano tube to form a coating layer on the surface of the silicon cathode material, so as to obtain the silicon cathode material coated by the carbon nano tube; c. the obtained silicon cathode material coated by the nano tube is powder formed by micron-sized particles, and the particle size of the particles is 5-10 microns. The invention has the characteristics of uniform coating, good conductivity, small volume expansion, high capacity, no introduction of other metal impurities, low manufacturing cost, strong practicability and the like.

Description

Method for coating silicon anode material with carbon nanotubes

【Technical field】

The invention relates to the technical field of preparation of negative electrode materials for lithium batteries, in particular to a method for coating silicon negative electrode materials with carbon nanotubes.

【Background technique】

At present, commercial lithium-ion batteries generally use graphite carbon materials as the negative electrode, and the theoretical capacity of graphite is 372mAh/g, which limits the energy density of lithium-ion batteries. The theoretical capacity of silicon anode material is 4200mAh/g, and the theoretical capacity of silicon oxide is 2000mAh/g, which is the first choice for a new generation of battery anode materials. However, during the intercalation and deintercalation of lithium ions, the volume of silicon oxide will expand rapidly, which can easily lead to a decrease in the capacity of lithium ion batteries, or even a short circuit.

Much work has been done to improve the electrochemical stability of silicon and silicon oxide. Due to the large aspect ratio of carbon nanotubes, the electrical conductivity and mechanical properties of silicon materials can be increased, and the adverse effects of volume expansion of silicon materials can be alleviated. However, at present, most of the silicon material agglomerates and carbon nanotubes are mixed in the battery preparation, or the in-situ growth method is not only complicated, the cost is high, but also the process is cumbersome and the uniformity is poor.

In the prior art, one of the solutions is to make a catalyst solution with a catalyst and a solvent, add the silicon material to the catalyst solution so that the catalyst is supported on the surface of the silicon material, and then add it to the carbon source solution, so that the carbon source is supported on its surface. . In this method, the catalyst cannot be uniformly supported on the surface of the silicon material, the resulting battery has a low gram capacity, and needs to be cleaned with hydrochloric acid, nitric acid, and hydrofluoric acid in the later stage. In addition, the silicon material is prone to agglomeration during the drying process after cleaning, which affects the compound use with the graphite anode material. Another solution involves the method of in-situ coating of carbon nanotubes and amorphous carbon with silicon, but the obtained carbon nanotubes are thick and short. 8. The obtained lithium ion negative electrode has poor conductivity, so the performance of the obtained product is also limited, the specific capacity is about 1000-1360mAh/g, and the commercial value is also low. In other schemes, the method of in-situ growth of carbon tubes from silicon or its oxides is used, and the coated carbon nanotubes are prepared by attaching metal catalysts to the surface of silicon or its oxides and generating carbon nanotubes on its surface by chemical vapor deposition method. tube of silicon or its silicon oxide. However, this solution cannot remove the metal catalyst impurities, which will aggravate the self-discharge of the battery and affect the storage performance. Moreover, the output is limited, mass production is difficult, and the cost is high.

[Content of the invention]

The present invention aims to solve the above problems, and provides a carbon nanotube-coated silicon with uniform coating, good conductivity, small volume expansion, high capacity, no other metal impurities, low manufacturing cost and strong practicability. The method of negative electrode material.

In order to achieve the above object, the present invention provides a method for carbon nanotubes to coat a silicon negative electrode material, and the method comprises the following steps:

a. Take carbon nanotube powder and silicon anode material powder with a weight ratio of 0.1 to 2: 99.9 to 98 and put them into the coating equipment;

b. Start the coating equipment, and run it at a speed of 3 to 40 m/s for 1 to 20 minutes, so that the carbon nanotubes form a coating layer on the surface of the silicon negative electrode material to obtain a carbon nanotube-coated silicon negative electrode material;

c. The obtained nanotube-coated silicon negative electrode material is a powder composed of micron-sized particles, and the particle size of the particles is 2 microns to 10 microns.

The carbon nanotubes are single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture of any two.

The carbon nanotubes are fibrous agglomerates with a diameter of 2 to 100 nanometers, a length of 5 to 50 microns and a bulk density of 0.01 to 0.1 g/cubic centimeter.

The silicon anode material is silicon oxide.

The silicon oxide is a particle with a particle size of 2-10 microns and a density of 1.1 g/cm 3 .

The thickness of the coating layer is 2 nanometers to 500 nanometers.

In a specific embodiment, the method comprises the following steps:

a, take the carbon nanotube powder and silicon negative electrode material powder that the weight ratio is 2:98 and put into the coating equipment;

b. Start the coating equipment, run at a speed of 20 m/s for 10 minutes, so that the carbon nanotubes form a coating layer on the surface of the silicon negative electrode material, and obtain a silicon negative electrode material covered by carbon nanotubes;

c. The obtained nanotube-coated silicon negative electrode material is a powder composed of micron-sized particles, and the particle size of the particles is 2 microns to 10 microns.

The contribution of the present invention is that it effectively solves the problems existing in the prior art. The invention realizes the carbon nanotube coating of the silicon negative electrode material by physical methods, and the obtained product has the carbon nanotube coating uniformly, the conductivity is good, the volume expansion is small, and other metal impurities are not introduced. The method can significantly reduce the manufacturing cost and thus has high commercial value and practicability.

【Detailed ways】

The following examples are further explanations and illustrations of the present invention, and do not constitute any limitation to the present invention.

Example 1

Take 500 grams of silicon oxide powder and 4 grams of multi-wall carbon nanotube powder into the coating equipment, start the coating equipment, and run for 5 minutes at a linear speed of 15 m/s. In this embodiment, the particle size of the silicon oxide particles is 5-10 microns, and the density is 1.1 g/cm 3 . Multi-walled carbon nanotubes are fibrous aggregates with a diameter of 50 nanometers, a length of 25 micrometers, and a bulk density of 0.1 g/cm3. During the operation of the coating equipment, the multi-walled carbon nanotubes are dispersed into a network. Due to the large linear speed and shear force, and the surface of the silicon oxide is covered with a layer of carbon black, the carbon nanotubes are embedded in the surface of the silicon oxide. Carbon black layer. After the coating is completed, a carbon nanotube coating layer is formed on the surface of the silicon oxide, and the thickness of the coating layer is 100 nanometers to obtain a carbon nanotube-coated silicon negative electrode material. The coating equipment is commercially available. In this embodiment, the coating equipment is NOBILTA powder processing equipment, which can mix or precisely mix the above two different types of materials in a short time. The nanotube-coated silicon anode material obtained by the coating device is a powder composed of micron-sized particles, and the particle size of the particles is about 5-10 μm, which can be used as a lithium-ion battery anode material.

Example 2

Take 500 grams of silicon oxide powder and 4 grams of multi-wall carbon nanotube powder into the coating equipment, wherein the composition and form of silicon oxide and multi-wall carbon nanotubes are the same as those in Example 1. The cladding equipment was started and operated at a line speed of 10 m/s for 5 minutes. During the operation of the coating equipment, the multi-walled carbon nanotubes are dispersed into a network. Due to the large linear speed and shear force, and the surface of the silicon oxide is covered with a layer of carbon black, the carbon nanotubes are embedded in the surface of the silicon oxide. Carbon black layer. After the coating is completed, a carbon nanotube coating layer is formed on the surface of the silicon oxide, and the thickness of the coating layer is 100 nanometers to obtain a carbon nanotube-coated silicon negative electrode material. The coating equipment is the same as in Example 1. The nanotube-coated silicon anode material obtained by the coating device is a powder composed of micron-sized particles, and the particle size of the particles is about 5-10 μm, which can be used as a lithium-ion battery anode material.

Example 3

Take 500 grams of silicon oxide powder, 0.5 grams of 8012 single-walled carbon nanotubes, and 2 grams of multi-walled carbon nanotubes into the coating equipment, wherein the single-walled carbon nanotubes have a diameter of 2 nanometers and a length of 50 micrometers. Fibrous agglomerates with a bulk density of 0.01 g/cm3. The composition and morphology of the silicon oxide and multi-walled carbon nanotubes are the same as those in Example 1. The cladding equipment was started and operated at a line speed of 15 m/s for 5 minutes. During the operation of the coating equipment, the single-walled carbon nanotubes and multi-walled carbon nanotubes are dispersed into a network. Due to the large linear velocity and shear force, and the surface of the silicon oxide is coated with a layer of carbon black, the carbon nanotubes are A layer of carbon black embedded on the surface of the silicon oxide. After the coating is completed, a carbon nanotube coating layer is formed on the surface of the silicon oxide, and the thickness of the coating layer is 80 nanometers to obtain a carbon nanotube-coated silicon negative electrode material. The coating equipment is the same as in Example 1. The nanotube-coated silicon anode material obtained by the coating device is a powder composed of micron-sized particles, and the particle size of the particles is about 5-10 μm, which can be used as a lithium-ion battery anode material.

Example 4

Take 500 grams of silicon oxide powder, 0.5 grams of 8012 single-walled carbon nanotubes, and 2 grams of NTP3003 multi-walled carbon nanotubes and put them into the coating equipment. The structure and form are the same as those of Example 3. The cladding equipment was started and operated at a line speed of 15 m/s for 10 minutes. During the operation of the coating equipment, the single-walled carbon nanotubes and multi-walled carbon nanotubes are dispersed into a network. Due to the large linear velocity and shear force, and the surface of the silicon oxide is coated with a layer of carbon black, the carbon nanotubes are A layer of carbon black embedded on the surface of the silicon oxide. After the coating is completed, a carbon nanotube coating layer is formed on the surface of the silicon oxide, and the thickness of the coating layer is 80 nanometers to obtain a carbon nanotube-coated silicon negative electrode material. The coating equipment is commercially available. The nanotube-coated silicon anode material obtained by the coating device is a powder composed of micron-sized particles, and the particle size of the particles is about 5-10 μm, which can be used as a lithium-ion battery anode material.

Example 5

Take 500 grams of silicon oxide powder and 1 gram of 9012 double-walled carbon nanotubes into the coating equipment, wherein the double-walled carbon nanotubes have a diameter of 4 nanometers, a length of 50 micrometers, and a bulk density of 0.02 grams per cubic centimeter. fibrous aggregates. The composition and form of the silicon oxide are the same as those in Example 1. The cladding equipment was started and operated at a line speed of 25 m/s for 5 minutes. During the operation of the coating equipment, the double-walled carbon nanotubes are dispersed into a network. Due to the large linear velocity and shear force, and the surface of the silicon oxide is covered with a layer of carbon black, the carbon nanotubes are embedded in the surface of the silicon oxide. For the carbon black layer, a carbon nanotube coating layer is formed on the surface of the silicon oxide, and the thickness of the coating layer is 50 nanometers to obtain a carbon nanotube-coated silicon negative electrode material. The coating equipment is commercially available. The nanotube-coated silicon negative electrode material obtained by the coating device is a powder composed of micron-sized particles, and the particle size of the particles is about 5-10 microns, which can be used as a lithium-ion battery negative electrode material.

Example 6

Take 500 grams of silicon oxide powder and 10.2 grams of NTP3023 multi-walled carbon nanotubes and put them into the coating equipment. The cladding equipment was started and operated at a line speed of 25 m/s for 20 minutes. During the operation of the coating equipment, the multi-walled carbon nanotubes are dispersed into a network. Due to the large linear speed and shear force, and the surface of the silicon oxide is covered with a layer of carbon black, the carbon nanotubes are embedded in the surface of the silicon oxide. For the carbon black layer, a carbon nanotube coating layer is formed on the surface of the silicon oxide, and the thickness of the coating layer is 500 nanometers to obtain a carbon nanotube-coated silicon negative electrode material. The coating equipment is commercially available. The nanotube-coated silicon negative electrode material obtained by the coating device is a powder composed of micron-sized particles, and the particle size of the particles is about 2-10 microns, which can be used as a lithium-ion battery negative electrode material.

Although the present invention is disclosed through the above embodiments, the protection scope of the present invention is not limited to this, and the deformation and replacement of the above components will fall into the present invention without departing from the concept of the present invention. within the scope of the claims.

Claims (7)

1. A method for coating a silicon cathode material with a carbon nano tube is characterized by comprising the following steps:

a. taking the components in a weight ratio of 0.1-2: feeding 99.9-98 parts of carbon nano tube powder and silicon negative electrode material powder into coating equipment;

b. starting coating equipment, and running for 1-20 minutes at a rotating speed of 3-40 m/s to enable the carbon nano tube to form a coating layer on the surface of the silicon cathode material, so as to obtain the silicon cathode material coated by the carbon nano tube;

c. the obtained silicon cathode material coated by the nano tube is powder formed by micron-sized particles, and the particle size of the particles is 2-10 microns.

2. The method of claim 1, wherein the carbon nanotubes are single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture of any two.

3. The method of claim 2, wherein the carbon nanotubes are fibrous agglomerates having a tube diameter of 2 to 100 nm, a length of 5 to 50 μm, and a bulk density of 0.01 to 0.1 g/cc.

4. The method of claim 1, wherein the silicon negative electrode material is silica.

5. The method of claim 4, wherein the silica is in the form of particles having a particle size of 2 to 10 microns and a density of 1.1 g/cc.

6. The method of claim 1, wherein the coating has a thickness of 2 nm to 500 nm.

7. The method of claim 1, characterized in that it comprises the following steps:

a. putting carbon nanotube powder and silicon cathode material powder in a weight ratio of 2:98 into coating equipment;

b. starting coating equipment, and running at the rotating speed of 20m/s for 10 minutes to enable the carbon nano tube to form a coating layer on the surface of the silicon cathode material, so as to obtain the silicon cathode material coated by the carbon nano tube;

c. the obtained silicon cathode material coated by the nano tube is powder formed by micron-sized particles, and the particle size of the particles is 2-10 microns.