CN110828811A - Silicon oxide-graphite composite negative electrode material for lithium ion battery and preparation method thereof - Google Patents

Silicon oxide-graphite composite negative electrode material for lithium ion battery and preparation method thereof Download PDF

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CN110828811A
CN110828811A CN201911169897.XA CN201911169897A CN110828811A CN 110828811 A CN110828811 A CN 110828811A CN 201911169897 A CN201911169897 A CN 201911169897A CN 110828811 A CN110828811 A CN 110828811A
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graphite
matrix
silicon oxide
silica
negative electrode
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马倩倩
徐宁
吕菲
宋英杰
伏萍萍
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Tianjin B&M Science and Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a spherical silicon oxide-graphite composite negative electrode material for a lithium ion battery and a preparation method thereof. The synthesis process is simple, the process conditions are easy to control, and industrialization is easy to realize; the prepared spherical silicon oxide-graphite composite negative electrode material has good circulation and small expansion coefficient, and can be used as a negative electrode material of a new generation lithium ion power battery.

Description

Silicon oxide-graphite composite negative electrode material for lithium ion battery and preparation method thereof
Technical Field
The invention relates to the field of lithium ion battery materials, in particular to a silicon oxide-graphite composite negative electrode material for a lithium ion battery and a preparation method thereof.
Background
The theoretical capacity of the graphite cathode material is 372mAh/g, and the requirement of a novel lithium ion battery on high energy density cannot be met. Therefore, the development of new high-capacity lithium ion battery cathode materials is of great importance.
At present, the main technical approach for improving the energy density of the battery at home and abroad is to replace the traditional graphite cathode material with a silicon-carbon cathode material. The silicon-based material has the highest theoretical specific capacity (4200mAh/g) in the lithium ion battery negative electrode material, and is the best choice for the current high-energy density lithium ion battery negative electrode material.
But the pure silicon material has the problem of overlarge volume expansion (more than or equal to 300 percent) in the lithium embedding process. The silicon oxide also has higher theoretical specific capacity, and compared with pure silicon, the silicon oxide has smaller volume effect in the lithium intercalation process, and Si-O bonds with higher bond energy exist in the material, so that the volume expansion of silicon can be effectively inhibited, and the cycle performance is more advantageous.
However, the silicon monoxide generates Li during the process of lithium intercalation2O and Li4SiO4These inactive phases can buffer the volume expansion of the material well, but the formation of these inactive phases also consumes a portion of the lithium, and thus the silica material also suffers from low initial efficiency. At present, the main methods for improving the electrochemical performance of the silicon oxide include particle nanocrystallization, compounding with various carbon materials, compounding with metals and metal oxides, prelithiation, coating modification and the like.
Coating modification is the most common modification method at present. Prior art CN103647056B discloses a SiOxThe invention relates to a composite cathode material, a preparation method and a battery, wherein the cathode material comprises a silicon oxide material, a carbon material and an amorphous carbon coating layer, the silicon oxide material is coated on the surface of carbon material particles, the amorphous carbon coating layer is the outermost coating layer, and the silicon oxide material is coated on the surface of the carbon material particles.
However, in the conventional coating modified material, the outermost coating layer has a very limited effect of inhibiting the expansion of the silica particles, and the coating layer is easily detached from the particle surface after several charge-discharge cycles, so that the cycle performance of the material is very poor, and the problem of the silica material is not essentially solved. Therefore, the development of a silicon oxide-based negative electrode material with good cycle performance and small volume expansion effect and a preparation method thereof are technical problems in the field.
Disclosure of Invention
In order to solve the technical problems, the invention provides a silicon oxide-graphite composite negative electrode material for a lithium ion battery and a preparation method thereof.
The technical scheme adopted by the invention is as follows:
the silicon oxide-graphite composite negative electrode material is an integrated fusion material and is formed by fusing a silicon oxide matrix, a graphite matrix and amorphous carbon together, and the D50 of the silicon oxide-graphite composite negative electrode material is 10-30 mu m.
Preferably, the silica matrix is nano or submicron silica particles with a chemical formula of SiOxWherein x is more than or equal to 0.8 and less than or equal to 1.2, and the particle size is 0.05-1 mu m; the particle size of the graphite matrix is 0.1-3 μm.
The size of the matrix has an important influence on the structure and electrochemical properties of the composite material: the size of the silica matrix particles is too large, and the particles are seriously pulverized in the charging and discharging processes; the cycle performance is influenced by the fact that the silica matrix particles are too small and have larger specific surface area and more side reactions of the electrolyte. The graphite matrix particles are too large in size, so that an integrated fusion material is difficult to form with the silicon monoxide in the spraying process, but a core-shell structure with large-particle graphite as a core and small-particle silicon monoxide as a shell is formed, and expansion, contraction and pulverization in the charging and discharging processes of the silicon monoxide can not be effectively inhibited; too small a graphite matrix also increases the occurrence of side reactions. Therefore, the selection of an appropriate particle size is the basis for good performance of the material. The particle sizes of the selected materials can be effectively fused to form the integrated silicon oxide-graphite composite negative electrode material.
Preferably, in the silicon oxide-graphite composite negative electrode material, the mass fraction of the silicon oxide matrix is 5-90%, the mass fraction of the graphite matrix is 10-95%, and the mass fraction of the amorphous carbon is 1-10%.
A preparation method of a silicon oxide-graphite composite negative electrode material comprises the following steps:
1) uniformly mixing a silica matrix and absolute ethyl alcohol, and performing ball milling treatment until the median particle size is 0.05-1 mu m to obtain silica slurry 1, wherein the silica matrix is nano or submicron SiOxParticles, wherein x is more than or equal to 0.8 and less than or equal to 1.2,
2) uniformly mixing a graphite matrix raw material and absolute ethyl alcohol, and performing ball milling treatment until the median particle size is 0.1-3 mu m to obtain graphite slurry 2;
3) carrying out ball milling and mixing on the silicon monoxide slurry 1, the graphite slurry 2, the asphalt, the aluminum isopropoxide and other organic carbon sources in a ball milling tank for 0.5-10 h to obtain a slurry 3;
4) spray drying the slurry 3 at an inlet temperature of 100-300 ℃ to obtain powder 1;
5) and (3) raising the temperature of the powder 1 to 700-1100 ℃ at a heating rate of 1-10 ℃/min in an inert atmosphere, and carrying out constant-temperature heat treatment for 1-24 h to obtain a product of the silicon oxide-graphite composite negative electrode material.
The formation of Li from the silicon monoxide and by-product silicon oxide during the intercalation of lithium2O and Li4SiO4These inactive phases can buffer the volume expansion of the material well, but the formation of these inactive phases also consumes a portion of the lithium, thereby causing a problem of low initial efficiency of the silica material.
The aluminum isopropoxide added in the invention can consume SiOxSiO produced as a by-product of the oxidation2To make SiO2The conversion into lithium-free silicate reduces irreversible capacity loss caused by silicon oxide and improves the first efficiency of the material.
Preferably, the mass of the aluminum isopropoxide in the step 3) is 0.1-2% of the mass of the silica matrix.
The content of aluminum isopropoxide is too small to be mixed with SiO2Completely reacting to remove the by-product; excessive aluminum isopropoxide content and in-processInert Al is introduced into the material2O3The amount of impurities, and therefore, aluminum isopropoxide, is one of the key factors for the present invention. Through experiments, the aluminum isopropoxide can be found to be just completely reacted to remove SiO when the mass of the aluminum isopropoxide is 0.1-2% of the mass of the silica matrixxSiO produced by oxidation2The effect of removing the by-products is better, thereby effectively improving the first efficiency of the silicon protoxide material.
Preferably, the asphalt in step 3) is one or both of coal asphalt and petroleum asphalt.
Preferably, the mass of the asphalt in the step 3) is 5-15% of the total mass of the silica matrix and the graphite matrix.
The asphalt plays a role in fusion bonding, so that a certain content is needed to bond the silica matrix and the graphite matrix together; however, if the content of the pitch is too high, carbon generated by high-temperature carbonization of the pitch is amorphous carbon, and the excessive amorphous carbon can consume lithium in the electrolyte, and the performance of the material can be adversely affected. The content of 5% to 15% is preferably.
Preferably, the other organic carbon source in step 3) is one or more of glucose, sucrose, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone and phenolic resin.
Preferably, the mass of the other organic carbon source in the step 3) is 1-10% of the total mass of the silica matrix and the graphite matrix.
The silicon oxide-graphite composite negative electrode material and the silicon oxide-graphite composite negative electrode material prepared by the preparation method can be better applied to lithium ion batteries.
The invention has the beneficial effects that:
1) the invention fundamentally overcomes the defect of low initial effect of the silicon monoxide, and the aluminum isopropoxide added in the melting process can consume SiOxSiO produced as a by-product of the oxidation2To make SiO2The silicate which does not consume lithium is converted, the irreversible capacity loss caused by silicon oxide is reduced, and the first efficiency of the material is essentially improved;
2) compared with the prior art, the spherical silicon monoxide-graphite composite material is prepared by a ball milling process, a spray drying process and a high-temperature carbonization process which are easy to realize industrialization: the material is prepared by ball-milling a raw material of the silicon oxide into submicron particles, so that the lithium ion content in SiO is greatly reducedxThe transmission distance in the particles has great advantage in circulation compared with micron-sized silicon oxide;
3) different from the traditional carbon layer coated on the outer layer, the invention firstly grinds graphite spheres into micron-sized small particles, utilizes the fusion bonding effect of asphalt and other organic carbon sources under the low-temperature heating condition, utilizes the instantaneous drying (the segregation phenomenon is limited within the micron scale range) and the sphere forming effect of spray drying to fuse the silicon monoxide particles and the flake graphite together, and finally obtains the sphere-like silicon monoxide-graphite composite material through high-temperature disproportionation reaction and carbonization treatment.
The spherical-like silicon oxide-graphite composite material has the advantages that the silicon oxide and the flake graphite are fused together instead of coating the silicon oxide on the surface of graphite particles, so that the volume expansion of the silicon oxide in the charging and discharging processes can be effectively inhibited, the particle pulverization is prevented, the integrity of an original structure is kept, and the cycle life of the material is prolonged.
Drawings
FIG. 1 is a scanning electron micrograph of a silica-graphite composite negative electrode material prepared in comparative example 1;
FIG. 2 is a scanning electron micrograph of a silica-graphite composite negative electrode material prepared in example 1;
FIG. 3 is a graph showing the first charge and discharge curves of a negative electrode material of a silica-graphite composite obtained in example 1;
fig. 4 is a graph showing cycle characteristics of the negative electrode material of the silica-graphite composite obtained in example 1.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings and examples.
Example 1
A preparation method of a silicon oxide-graphite composite negative electrode material comprises the following steps:
1) uniformly mixing 120g of a silica raw material and 1kg of absolute ethyl alcohol, and carrying out ball milling treatment until the median particle size is 0.5um to obtain silica slurry 1;
2) 1kg of natural graphite raw material and 2kg of absolute ethyl alcohol are uniformly mixed and subjected to ball milling treatment until the median particle size is 1.5um, so that graphite slurry 2 is obtained;
3) mixing silica slurry 1, graphite slurry 2, 100g of medium temperature coal pitch, 20g of polyvinylpyrrolidone and 1g of aluminum isopropoxide in a ball milling tank by ball milling for 4 hours;
4) spray drying the slurry at an inlet temperature of 150 ℃ to obtain powder 1;
5) and (3) heating the powder 1 to 980 ℃ at the heating rate of 2 ℃/min in the nitrogen atmosphere, and carrying out constant-temperature heat treatment for 2h to obtain the spherical silicon oxide-graphite composite negative electrode material.
Comparative example 1
A preparation method of a silicon oxide-graphite composite negative electrode material comprises the following steps:
1) uniformly mixing 120g of a silica raw material and 1kg of absolute ethyl alcohol, and carrying out ball milling treatment until the median particle size is 0.5um to obtain silica slurry 1;
2) carrying out ball milling and mixing on 1 part of silica slurry, 1kg of natural graphite raw material with the median particle size of 12um, 100g of medium temperature coal pitch, 20g of polyvinylpyrrolidone, 1g of aluminum isopropoxide and 2kg of absolute ethyl alcohol in a ball milling tank for 4 h;
3) spray drying the slurry at an inlet temperature of 150 ℃ to obtain powder 1;
4) and (3) heating the powder 1 to 980 ℃ at the heating rate of 2 ℃/min in the nitrogen atmosphere, and carrying out constant-temperature heat treatment for 2h to obtain the silicon monoxide-graphite composite negative electrode material.
Comparative example 2
Compared with the embodiment 1, the step 3) is changed into the following steps:
3) carrying out ball milling and mixing on the silicon oxide slurry 1, the graphite slurry 2, 100g of medium temperature coal tar pitch and 20g of polyvinylpyrrolidone in a ball milling tank for 4 h;
other step parameters remain unchanged.
Comparative example 3
Compared with the embodiment 1, the step 3) is changed into the following steps:
3) carrying out ball milling and mixing on the silicon oxide slurry 1, the graphite slurry 2, 100g of medium temperature coal pitch, 20g of polyvinylpyrrolidone and 0.08g of aluminum isopropoxide in a ball milling tank for 4 h;
other step parameters remain unchanged.
Comparative example 4
Compared with the embodiment 1, the step 3) is changed into the following steps:
3) mixing silica slurry 1, graphite slurry 2, 100g of medium temperature coal pitch, 20g of polyvinylpyrrolidone and 3g of aluminum isopropoxide in a ball milling tank by ball milling for 4 hours;
other step parameters remain unchanged.
Example 2
A preparation method of a spherical silicon monoxide-graphite composite negative electrode material comprises the following steps:
1) uniformly mixing 90g of a silica raw material and 1kg of absolute ethyl alcohol, and carrying out ball milling treatment until the median particle size is 0.5um to obtain silica slurry 1;
2) 1kg of natural graphite raw material and 2kg of absolute ethyl alcohol are uniformly mixed and subjected to ball milling treatment until the median particle size is 1.5um, so that graphite slurry 2 is obtained;
3) carrying out ball milling and mixing on the silicon oxide slurry 1, the graphite slurry 2, 95g of medium temperature coal pitch, 20g of polyvinylpyrrolidone and 0.9g of aluminum isopropoxide in a ball milling tank for 4 h;
4) spray drying the slurry at an inlet temperature of 150 ℃ to obtain powder 1;
5) putting the powder 1 into a proper amount of absolute ethyl alcohol solution for washing, pouring out the ethyl alcohol solution, replacing with a new absolute ethyl alcohol solution for washing again, repeating for three times, and filtering and drying to obtain powder 2;
6) and (3) raising the temperature of the powder 3 to 980 ℃ at the heating rate of 2 ℃/min in the nitrogen atmosphere, and carrying out constant-temperature heat treatment for 2h to obtain the spherical silicon monoxide-graphite composite negative electrode material.
Example 3
A preparation method of a spherical silicon monoxide-graphite composite negative electrode material comprises the following steps:
1) uniformly mixing 120g of a silica raw material and 1kg of absolute ethyl alcohol, and carrying out ball milling treatment until the median particle size is 0.5um to obtain silica slurry 1;
2) 1kg of natural graphite raw material and 2kg of absolute ethyl alcohol are uniformly mixed and subjected to ball milling treatment until the median particle size is 1.5um, so that graphite slurry 2 is obtained;
3) carrying out ball milling and mixing on the silicon oxide slurry 1, the graphite slurry 2, 100g of medium temperature coal pitch, 20g of polyethylene glycol 2000 and 1g of aluminum isopropoxide in a ball milling tank for 4 h;
4) spray drying the slurry at an inlet temperature of 150 ℃ to obtain powder 1;
5) putting the powder 1 into a proper amount of absolute ethyl alcohol solution for washing, pouring out the ethyl alcohol solution, replacing with a new absolute ethyl alcohol solution for washing again, repeating for three times, and filtering and drying to obtain powder 2;
6) and (3) heating the powder 2 to 980 ℃ at the heating rate of 2 ℃/min in the nitrogen atmosphere, and carrying out constant-temperature heat treatment for 2h to obtain the spherical silicon oxide-graphite composite negative electrode material.
Example 4
A preparation method of a spherical silicon monoxide-graphite composite negative electrode material comprises the following steps:
1) uniformly mixing 170g of a silica raw material and 1kg of absolute ethyl alcohol, and carrying out ball milling treatment until the median particle size is 0.5um to obtain silica slurry 1;
2) 1kg of natural graphite raw material and 2kg of absolute ethyl alcohol are uniformly mixed and subjected to ball milling treatment until the median particle size is 1.5um, so that graphite slurry 2 is obtained;
3) carrying out ball milling and mixing on the silicon oxide slurry 1, the graphite slurry 2, 105g of medium temperature coal pitch, 20g of polyvinylpyrrolidone and 1.2g of aluminum isopropoxide in a ball milling tank for 4 h;
4) spray drying the slurry at an inlet temperature of 180 ℃ to obtain powder 1;
5) putting the powder 1 into a proper amount of absolute ethyl alcohol solution for washing, pouring out the ethyl alcohol solution, replacing with a new absolute ethyl alcohol solution for washing again, repeating for three times, and filtering and drying to obtain powder 2;
6) and (3) heating the powder 2 to 1000 ℃ at the heating rate of 2 ℃/min in the nitrogen atmosphere, and carrying out constant-temperature heat treatment for 2h to obtain the spherical silicon oxide-graphite composite negative electrode material.
Example 5
A preparation method of a spherical silicon monoxide-graphite composite negative electrode material comprises the following steps:
1) uniformly mixing 120g of a silica raw material and 1kg of absolute ethyl alcohol, and carrying out ball milling treatment until the median particle size is 0.5um to obtain silica slurry 1;
2) 1kg of natural graphite raw material and 2kg of absolute ethyl alcohol are uniformly mixed and subjected to ball milling treatment until the median particle size is 1.5um, so that graphite slurry 2 is obtained;
3) carrying out ball milling and mixing on the silicon oxide slurry 1, the graphite slurry 2, 100g of medium temperature coal pitch, 20g of polyvinyl alcohol and 1g of aluminum isopropoxide in a ball milling tank for 4 h;
4) spray drying the slurry at an inlet temperature of 150 ℃ to obtain powder 1;
5) putting the powder 1 into a proper amount of absolute ethyl alcohol solution for washing, pouring out the ethyl alcohol solution, replacing with a new absolute ethyl alcohol solution for washing again, repeating for three times, and filtering and drying to obtain powder 2;
6) and (3) heating the powder 2 to 980 ℃ at the heating rate of 2 ℃/min in the nitrogen atmosphere, and carrying out constant-temperature heat treatment for 2h to obtain the spherical silicon oxide-graphite composite negative electrode material.
Experimental conditions:
the results of the electrochemical performance tests of the composite anode materials prepared in examples 1 to 5 and comparative examples 1 to 4 are shown in table 1. The test conditions of the button cell are as follows: 23 +/-2 ℃, LR2032, first charge and discharge I is 0.1C, cycle I is 0.2C, 0.005-2.0V vs. Li/Li+。
TABLE 1 electrochemical Performance test results for the products
Figure BDA0002289184260000091
Figure BDA0002289184260000101
As can be seen from the comparative data, the spherical silica-graphite composite negative electrode materials prepared in embodiments 1 to 5 of the present invention have electrochemical properties such as first coulombic efficiency and cycle stability superior to those of the negative electrode materials in the comparative examples, especially cycle performance, which is due to the excellent structure of the graphite-silica composite material: the amorphous carbon, the small-particle micron-sized graphite and the silicon oxide particles are effectively fused to play a role in limiting the range, so that the expansion and pulverization of the silicon oxide in the charging and discharging processes are effectively inhibited, and the problem that a coated carbon layer falls off in the traditional technology does not exist.
Fig. 3 and fig. 4 show a first charge-discharge curve diagram and a cycle performance diagram of the silicon oxide-graphite composite anode material prepared in example 1, and it can be seen that the first reversible specific capacity of the material prepared in example 1 can reach 469.7mAh/g, the capacity retention rate at 100 weeks can reach 98.2%, and excellent electrochemical performance is shown.
Comparative example 1 graphite was not previously ball-milled into small particles, and thus, silica particles were attached to the surfaces of large graphite particles in spray-dried spheres, and fig. 1 is an SEM electron micrograph of the material prepared in comparative example 1, and this structure was not effective in suppressing the expansion, contraction and pulverization of silica during charging and discharging, so the performance was significantly reduced compared to that of example 1, which was ball-milled.
Comparative example 2 aluminum isopropoxide was not added, and thus SiO, a by-product generated during the synthesis of the material, was not consumed2，SiO2The by-product also consumed the lithium source by inserting lithium during the first charge and discharge process, resulting in a decrease in the first efficiency, thereby affecting the first effect of comparative example 2.
The addition of aluminum isopropoxide has a greater effect on the product properties. In comparative example 3, aluminum isopropoxide was added in a small amount, resulting in incomplete reactionConsuming the by-product SiO2In comparative example 4, more aluminum isopropoxide was added, and more Al remained2O3Inert by-products, and therefore, the amount of aluminum isopropoxide added has a greater impact on the performance of the material.
Fig. 1 is an SEM photograph of a silica-graphite composite anode material prepared in comparative example 1; FIG. 2 is an SEM photograph of a silica-graphite composite anode material prepared in example 1; as can be seen from the figure, the graphite in comparative example 1 is not subjected to the previous step of ball milling into small particles, and therefore, a significant core-shell structure is formed by the spray drying process, which cannot embed the silica particles in the graphite spheres and cannot effectively inhibit the expansion, contraction and pulverization of the silica, whereas example 1 reduces the size of primary particles by ball milling the graphite and reduces the difference from the size of the silica particles, so that the core-shell structure is not formed during the spray drying process, but the silica particles are fused together into uniformly dispersed spheres, and the structure in which the silica particles are embedded in the graphite can effectively inhibit the expansion and contraction of the silica during the charging and discharging processes, thereby effectively improving the cycle performance.
In summary, the disclosure of the present invention is not limited to the above-mentioned embodiments, and persons skilled in the art can easily set forth other embodiments within the technical teaching of the present invention, but such embodiments are included in the scope of the present invention.

Claims (10)

1. A silicon oxide-graphite composite negative electrode material is characterized in that: the silicon oxide-graphite composite negative electrode material is an integrated fusion material and is formed by fusing a silicon oxide matrix, a graphite matrix and amorphous carbon together, and the D50 of the silicon oxide-graphite composite negative electrode material is 10-30 mu m.
2. The silica-graphite composite anode material according to claim 1, characterized in that: the silicon monoxide matrix is nano or submicron silicon monoxide particles with a chemical formula of SiOxWherein x is more than or equal to 0.8 and less than or equal to 1.2, and the particle size is 0.05-1 mu m; of the graphite matrixThe particle size of the particles is 0.1-3 μm.
3. The silica-graphite composite anode material according to claim 1, characterized in that: in the silicon oxide-graphite composite negative electrode material, the mass fraction of a silicon oxide matrix is 5-90%, the mass fraction of a graphite matrix is 10-95%, and the mass fraction of amorphous carbon is 1-10%.
4. A preparation method of a silicon oxide-graphite composite negative electrode material is characterized by comprising the following steps:
1) uniformly mixing a silica matrix and absolute ethyl alcohol, and performing ball milling treatment until the median particle size is 0.05-1 mu m to obtain silica slurry 1, wherein the silica matrix is nano or submicron SiOxParticles, wherein x is more than or equal to 0.8 and less than or equal to 1.2;
2) uniformly mixing a graphite matrix and absolute ethyl alcohol, and performing ball milling treatment until the median particle size is 0.1-3 mu m to obtain graphite slurry 2;
3) carrying out ball milling and mixing on the silicon monoxide slurry 1, the graphite slurry 2, the asphalt, the aluminum isopropoxide and other organic carbon sources in a ball milling tank for 0.5-10 h to obtain a slurry 3;
4) spray drying the slurry 3 at an inlet temperature of 100-300 ℃ to obtain powder 1;
5) and (3) raising the temperature of the powder 1 to 700-1100 ℃ at a heating rate of 1-10 ℃/min in an inert atmosphere, and carrying out constant-temperature heat treatment for 1-24 h to obtain a product of the silicon oxide-graphite composite negative electrode material.
5. The method of claim 4, wherein: in the step 3), the mass fraction of the silica matrix is 5-90% and the mass fraction of the graphite matrix is 10-95% based on the total mass of the silica matrix and the graphite matrix.
6. The method of claim 4, wherein: in the step 3), the mass of the aluminum isopropoxide is 0.1-2% of that of the silica matrix.
7. The method of claim 4, wherein: the asphalt in the step 3) is one or two of coal asphalt or petroleum asphalt.
8. The method of claim 4, wherein: the mass of the asphalt in the step 3) is 5-15% of the total mass of the silica matrix and the graphite matrix.
9. The method of claim 4, wherein: and in the step 3), other organic carbon sources are one or more of glucose, sucrose, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone and phenolic resin.
10. The method of claim 4, wherein: the mass of other organic carbon sources in the step 3) is 1-10% of the total mass of the silica matrix and the graphite matrix.
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Cited By (7)

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CN113772678A (en) * 2021-08-30 2021-12-10 上海纳米技术及应用国家工程研究中心有限公司 Method for preparing carbon-coated silicon monoxide negative electrode material and reducing charge transfer impedance of carbon-coated silicon monoxide negative electrode material
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CN111463424A (en) * 2020-04-09 2020-07-28 北京蒙京石墨新材料科技研究院有限公司 Preparation method of silica negative electrode slurry
CN111900362A (en) * 2020-08-21 2020-11-06 珠海冠宇电池股份有限公司 Quick-charging type high-specific-capacity negative plate and lithium ion battery comprising same
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