Disclosure of Invention
In view of the above, the present invention provides a method for preparing a silicon-carbon negative electrode material, which can make the finally obtained silicon-carbon negative electrode material have the advantages of good dynamic performance of small-particle-size particles and small expansion stress, and also have the advantages of large compacted density of large-particle-size particles, easy processing and forming, and easy dispersion, and the silicon-carbon negative electrode material particles have good isotropy, so that the silicon-carbon negative electrode material has small volume expansion during lithium intercalation, and the cycle performance is improved.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a method of making a silicon carbon anode material, the method comprising: mixing SiOxMixing a carbon source and a dispersant to obtain a first mixed solution, wherein x is 0.5-1.0; performing first dispersion treatment on the first mixed solution, and filtering and drying to obtain a second mixed solutionA dispersion material; carrying out first carbonization treatment on the first dispersion material, and crushing to obtain primary particles, wherein the particle size of the primary particles is 0.5-1 mu m; mixing the primary particles with the carbon source and the dispersing agent to obtain a second mixed solution; carrying out second dispersion treatment on the second mixed solution, and filtering and drying to obtain a second dispersion material; and carrying out second carbonization treatment on the second dispersion material, and crushing to obtain secondary particles, wherein the particle size of the secondary particles is 10-15 mu m, so as to obtain the silicon-carbon negative electrode material.
Further, the SiOxThe particle size of the (B) is 80-200 nm; optionally, the carbon source comprises at least one of pitch, polyvinyl chloride, polyethylene, and phenolic resin; optionally, the dispersant comprises at least one of water, ethanol, methanol, acetone, alkanes, esters, aromatics, tetrahydrofuran, dimethyl sulfoxide, N-methylpyrrolidone, and N, N-dimethylformamide.
Further, the SiOxThe mass ratio of the carbon source to the dispersant is 1:20-1:1, and the mass of the dispersant to the SiOxAnd the total mass ratio of the carbon source is 1:1-10: 1.
Further, the rotation speed of the first dispersion treatment is 500-700 r/min, and the time is 1-20 h.
Further, the temperature of the first carbonization treatment is raised from room temperature to 500-800 ℃ at the speed of 2-10 ℃/min, and the temperature is kept for 10-20 h.
Further, the mass ratio of the primary particles to the carbon source is 1:1-1:5, and the mass ratio of the dispersant to the total mass of the primary particles and the carbon source is 20:1-5: 1.
Further, the rotation speed of the second dispersion treatment is 700-900 rpm, and the time is 2-10 h.
Further, the second carbonization treatment is carried out at the temperature of 1-10 ℃/min from the room temperature to 500-1100 ℃, and the temperature is kept for 2-20 h.
Compared with the prior art, the method for preparing the silicon-carbon anode material has the following advantages:
according to the method, the primary particles with the small particle size are formed firstly, and then the primary particles are dispersed and carbonized continuously to obtain the secondary particles with the large particle size, so that the silicon-carbon negative electrode material is obtained, and the silicon-carbon negative electrode material has the advantages of small particle size and small expansion stress, and also has the advantages of large particle size, high compaction density, easiness in processing and forming and easiness in dispersion.
Another object of the present invention is to provide a silicon-carbon negative electrode material, which is prepared by the above-described method, and therefore, the silicon-carbon negative electrode material has all the features and advantages of the silicon-carbon negative electrode material prepared by the above-described method, and will not be described herein again. In general, the silicon-carbon negative electrode material has the advantages of good dynamic performance and small expansion stress of small-particle-size particles, and also has the advantages of large compacted density, easiness in processing and forming and easiness in dispersion of large-particle-size particles, and the silicon-carbon negative electrode material particles are good in isotropy, so that the silicon-carbon negative electrode material is small in volume expansion during lithium intercalation, and the cycle performance is improved.
Another object of the present invention is to provide a lithium ion battery, which includes a negative electrode sheet, wherein the negative electrode sheet includes the aforesaid silicon-carbon negative electrode material, and therefore, the lithium ion battery has all the features and advantages of the aforesaid silicon-carbon negative electrode material, and will not be described herein again. In general, the lithium ion battery has good cycle performance and long service life.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
In one aspect of the invention, a method of making a silicon carbon anode material is presented. As described above, the conventional silicon-carbon negative electrode material is a primary molded particle, and a lithium ion transmission path is lengthened and lithium intercalation expansion stress is increased due to a large particle size of the particle, so that the negative electrode material is easily broken and loses activity. The particle size of the particles is small, the compaction density of the negative plate is low, the particles are difficult to disperse in slurry and easy to aggregate, and the lithium intercalation expansion stress is increased, so that the negative material is easy to break and lose activity. In addition, the one-step molded particles have poor isotropy, which results in large volume expansion of the negative electrode material during lithium intercalation, and thus poor cycle performance.
According to an embodiment of the invention, with reference to fig. 1, the method comprises:
s100: mixing SiOxMixing a carbon source and a dispersing agent to obtain a first mixed solution
According to an embodiment of the invention, in this step SiO is addedxAnd mixing the carbon source and the dispersing agent to obtain a first mixed solution. According to an embodiment of the invention, SiOxWherein x is 0.5-1.0. Thus, the silicon oxide is compounded with carbon, the volume expansion of the material during lithium intercalation can be reduced by the silicon oxide, and the capacity of the material can be improved by coating the silicon oxide with the carbon.
According to an embodiment of the invention, SiOxThe particle size of (a) may be 80-200 nm. Therefore, the silicon monoxide can effectively reduce the volume expansion of the material when lithium is embedded.
According to an embodiment of the present invention, the carbon source may include at least one of asphalt, polyvinyl chloride, polyethylene, and phenol resin. Therefore, the carbon-coated silicon monoxide obtained by the carbon source cracking can be utilized to improve the capacity of the material.
According to an embodiment of the present invention, the dispersant may include at least one of water, ethanol, methanol, acetone, alkane, ester, aromatic, tetrahydrofuran, dimethyl sulfoxide, N-methylpyrrolidone, and N, N-dimethylformamide. Thus, the silica and the carbon source can be dispersed by the dispersant to obtain the first mixed solution.
According to an embodiment of the invention, SiOxThe mass ratio of the carbon source to the dispersant can be 1:20-1:1, and the mass of the dispersant to SiOxThe ratio of the total mass of the carbon source may be 1:1 to 10: 1. Therefore, enough carbon can be ensured to coat the silicon monoxide after the subsequent first carbonization treatment, and enough dispersing agent can be ensured to disperse the silicon monoxide and the carbon source, so that a uniform first mixed solution can be obtained. Specifically, SiOxThe mass ratio of the carbon source to the dispersant can be 1:10, and the mass of the dispersant to SiOxThe ratio of the total mass of the carbon source may be 1.5: 1.
S200: carrying out first dispersion treatment on the first mixed solution, filtering and drying to obtain a first dispersion material
According to an embodiment of the present invention, in this step, the first mixed solution is subjected to a first dispersion treatment, and is filtered and dried to obtain a first dispersed material. According to the embodiment of the invention, the first dispersion treatment may be performed on the first mixed solution by using a dispersion machine, the rotation speed of the first dispersion treatment may be 500-700 rpm, and the time may be 1-20 h. Thus, a uniformly dispersed solution can be obtained, and a uniformly dispersed first dispersion material can be obtained after filtration and drying. Specifically, the rotation speed of the first dispersion treatment may be 600 rpm, and the time may be 3 hours.
S300: subjecting the first dispersed material to a first carbonization treatment and pulverizing to obtain primary particles
According to an embodiment of the present invention, in this step, the first dispersed material is subjected to the first carbonization treatment and pulverized to obtain primary particles. According to the embodiment of the invention, the first carbonization treatment can be performed on the first dispersion material by placing the first dispersion material into a tube furnace or an atmosphere box furnace, introducing high-purity nitrogen as a protective gas, raising the temperature from room temperature to 800 ℃ at a temperature-raising speed of 2-10 ℃/min, and keeping the temperature for 10-20 h. Thus, the material of carbon-coated silicon oxide can be obtained after carbonization. Specifically, the first carbonization treatment may be performed by raising the temperature from room temperature to 700 ℃ at a rate of 5 ℃/min and holding the temperature for 15 hours.
According to an embodiment of the present invention, after a material of carbon-coated silica is obtained, the above material is pulverized to obtain primary particles, which may have a particle size of 0.5 to 1 μm and a particle size classification of D50. Thus, primary particles having a small particle size, which have the advantages of good dynamic properties and a small expansion stress, can be obtained. Specifically, the primary particles may have a particle size of 0.8. mu.m.
S400: mixing the primary particles with a carbon source and a dispersant to obtain a second mixed solution
According to an embodiment of the present invention, in this step, the primary particles are mixed with a carbon source and a dispersant to obtain a second mixed solution. That is, after the primary particles are obtained, the subsequent steps are based on the primary particles, and the primary particles are continuously dispersed and carbonized to obtain secondary particles with larger particle size, the secondary particles retain the structure of the primary particles, and the secondary particles are carbon-coated on the primary particles, so that the finally obtained silicon-carbon anode material can have the advantages of both the primary particles and the secondary particles.
According to an embodiment of the present invention, the mass ratio of the primary particles to the carbon source may be 1:1 to 1:5, and the ratio of the mass of the dispersant to the total mass of the primary particles and the carbon source may be 20:1 to 5: 1. Therefore, enough carbon can be ensured to coat the primary particles after the subsequent second carbonization treatment, and enough dispersing agent can be ensured to disperse the primary particles and the carbon source, so that a uniform second mixed solution can be obtained. Specifically, the mass ratio of the primary particles to the carbon source may be 1:2, and the mass ratio of the dispersant to the total mass of the primary particles and the carbon source may be 10: 1.
S500: performing second dispersion treatment on the second mixed solution, filtering and drying to obtain a second dispersion material
According to an embodiment of the present invention, in this step, the second mixed solution is subjected to the second dispersion treatment, and is filtered and dried to obtain a second dispersed material. According to the embodiment of the invention, the second dispersion treatment may be performed on the second mixed solution by using a dispersion machine, the rotation speed of the second dispersion treatment may be 700-900 rpm, and the time may be 2-10 h. Thus, a uniformly dispersed solution can be obtained, and a second uniformly dispersed material can be obtained after filtration and drying. Specifically, the rotation speed of the second dispersion treatment may be 800 rpm, and the time may be 5 hours.
S600: performing second carbonization treatment on the second dispersion material, and crushing to obtain secondary particles so as to obtain the silicon-carbon negative electrode material
According to an embodiment of the present invention, in this step, the second dispersion material is subjected to the second carbonization treatment and pulverized to obtain secondary particles, so as to obtain a silicon carbon anode material. According to the embodiment of the invention, the second carbonization treatment can be performed on the second dispersion material by placing the second dispersion material into a tube furnace or an atmosphere box furnace, introducing high-purity nitrogen as a protective gas, raising the temperature from room temperature to 1100 ℃ at a temperature-raising speed of 1-10 ℃/min, and keeping the temperature for 2-20 h. Thus, a material of carbon-coated primary particles can be obtained after carbonization. Specifically, the second carbonization treatment may be performed by raising the temperature from room temperature to 1100 ℃ at a temperature raising rate of 1 ℃/min and holding the temperature for 15 hours.
According to an embodiment of the present invention, after a material of carbon-coated primary particles is obtained, the above material is pulverized to obtain secondary particles, which may have a particle size of 10 to 15 μm and a particle size classification of D50. Thus, secondary particles having a large particle diameter, which have the advantages of a large compacted density, easy processing and molding, and easy dispersion, and which retain the structure of the primary particles and are carbon-coated on the primary particles, can be obtained, and thus, have the advantages of good dynamic performance of the primary particles and small expansion stress. Specifically, the secondary particles may have a particle size of 12 μm.
According to the embodiment of the invention, the secondary particles are obtained, namely, the silicon-carbon negative electrode material is obtained, and the silicon-carbon negative electrode material has good isotropic performance compared with the primary particles due to twice dispersion and carbonization, so that the volume expansion of the negative electrode material during lithium intercalation can be further reduced, and the cycle performance of the negative electrode material can be improved.
In conclusion, the method comprises the steps of firstly forming primary particles with small particle size, and then continuously dispersing and carbonizing the primary particles to obtain secondary particles with large particle size, namely obtaining the silicon-carbon negative electrode material, wherein the secondary particles retain the structure of the primary particles, and the secondary particles are used for coating the primary particles with carbon, so that the silicon-carbon negative electrode material can simultaneously have the advantages of the primary particles and the advantages of the secondary particles, namely the silicon-carbon negative electrode material has the advantages of good dynamic performance and small expansion stress of small-particle-size particles, and also has the advantages of large compacted density, easiness in processing and forming and easiness in dispersion of large-particle-size particles, and the silicon-carbon negative electrode material particles are good in isotropy, so that the silicon-carbon negative electrode material is small in volume expansion during lithium intercalation, and the cycle performance is improved.
In another aspect of the invention, a silicon carbon anode material is provided. According to the embodiment of the invention, the silicon-carbon anode material is prepared by the method described above, so that the silicon-carbon anode material has all the characteristics and advantages of the silicon-carbon anode material prepared by the method described above, and further description is omitted. In general, the silicon-carbon negative electrode material has the advantages of good dynamic performance and small expansion stress of small-particle-size particles, and also has the advantages of large compacted density, easiness in processing and forming and easiness in dispersion of large-particle-size particles, and the silicon-carbon negative electrode material particles are good in isotropy, so that the silicon-carbon negative electrode material is small in volume expansion during lithium intercalation, and the cycle performance is improved.
In another aspect of the present invention, a lithium ion battery is provided. According to an embodiment of the present invention, the lithium ion battery includes a negative electrode sheet, and the negative electrode sheet includes the aforesaid silicon-carbon negative electrode material, so that the lithium ion battery has all the features and advantages of the aforesaid silicon-carbon negative electrode material, and will not be described herein again. In general, the lithium ion battery has good cycle performance and long service life.
The invention will now be illustrated by means of specific examples, which are provided for illustration only and should not be construed as limiting the scope of the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications.
Example 1
(1) A first mixed solution is prepared. Selecting SiO with the particle size of 100nm, mixing the SiO and the asphalt according to the mass ratio of 1:10, and then adding ethanol to obtain a first mixed solution, wherein the mass ratio of the ethanol to the total mass of the SiO and the asphalt is 1.5: 1.
(2) A first dispersion material is prepared. And (3) carrying out first dispersion treatment on the first mixed solution by using a dispersion machine, wherein the rotation speed of the first dispersion treatment is 600 revolutions per minute, and the time is 3 hours, and filtering and drying after dispersion to obtain a first dispersion material.
(3) Primary particles were prepared. And (3) putting the first dispersion material into a tube furnace, introducing high-purity nitrogen as protective gas, heating to 700 ℃ from room temperature at a heating rate of 5 ℃/min, and keeping the temperature for 15h to obtain the carbon-coated SiO material. Subsequently, the above material was pulverized to obtain primary particles having a particle diameter D50 ═ 0.8 μm.
(4) A second mixed solution is prepared. The primary particles and the asphalt were mixed in a mass ratio of 1:2, followed by addition of ethanol to obtain a second mixed solution, the mass ratio of ethanol to the total mass of the primary particles and the asphalt being 10: 1.
(5) A second dispersion material is prepared. And (3) carrying out second dispersion treatment on the second mixed solution by using a dispersion machine, wherein the rotation speed of the second dispersion treatment is 800 r/min, the time is 5h, and filtering and drying after dispersion to obtain a second dispersion material.
(6) Secondary particles are prepared. And (3) putting the second dispersed material into a tube furnace, introducing high-purity nitrogen as protective gas, heating to 1100 ℃ from room temperature at the heating rate of 1 ℃/min, and keeping the temperature for 15h to obtain the material of the carbon-coated primary particles. Subsequently, the above material was pulverized to obtain secondary particles having a particle size of D50 ═ 12 μm, that is, a silicon carbon negative electrode material.
SEM (scanning electron microscope) detection is carried out on the silicon-carbon negative electrode material obtained in the example 1, and an electron micrograph is shown in figure 2, so that the silicon-carbon negative electrode material has a uniform secondary particle appearance.
Comparative example 1
The preparation process of this comparative example is the same as that of example 1, except that the primary particles obtained in steps (1) to (3) are the final silicon carbon negative electrode material.
The silicon-carbon anode materials obtained in example 1 and comparative example 1 were respectively subjected to cycle performance tests, and as shown in fig. 3, compared with the primary particle silicon-carbon anode material obtained in comparative example 1, the secondary particle silicon-carbon anode material obtained in example 1 has no obvious decrease in gram specific capacity and is stable with the increase of cycle number, and has better cycle performance.
By comparison, the silicon carbon negative electrode material obtained in example 1 has both the advantages of the small particle size particles and the advantages of the large particle size particles, and thus has better cycle performance and longer service life.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.