CN110970611A - Hierarchical silicon-carbon composite material and preparation method and application thereof - Google Patents

Hierarchical silicon-carbon composite material and preparation method and application thereof Download PDF

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CN110970611A
CN110970611A CN201911333064.2A CN201911333064A CN110970611A CN 110970611 A CN110970611 A CN 110970611A CN 201911333064 A CN201911333064 A CN 201911333064A CN 110970611 A CN110970611 A CN 110970611A
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silicon
composite material
carbon
carbon source
carbon composite
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王敬
包乌日古木拉
苏岳锋
陈实
吴锋
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Beijing Institute of Technology BIT
Chongqing Innovation Center of Beijing University of Technology
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Beijing Institute of Technology BIT
Chongqing Innovation Center of Beijing University of Technology
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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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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 silicon-carbon composite material with a hierarchical structure and a preparation method and application thereof. The silicon-carbon composite material comprises a silicon-based material and a carbon material, wherein the silicon-based composite material has a sphere-like shape, and the sphere-like shape is formed by mutually inserting the silicon-based material and the carbon material in a sheet form and then secondarily assembling the silicon-based material and the carbon material. During preparation, mixing and ball-milling the silicon-based material and the inorganic carbon source to obtain a composite material of the silicon-based material and the inorganic carbon source; and mixing and stirring the composite material and an organic carbon source solution, centrifugally separating, drying and calcining to obtain the silicon-carbon composite material. The method mainly utilizes a physical method and has the characteristics of low cost, easy operation and the like. The silicon-carbon composite material prepared by the method has higher conductivity, effectively improves the first-week coulombic efficiency and improves the electrochemical cycling stability compared with the performance of a pure silicon-based material.

Description

Hierarchical silicon-carbon composite material and preparation method and application thereof
Technical Field
The invention belongs to the field of composite materials, relates to a lithium ion battery cathode material, and particularly relates to a hierarchical silicon-carbon composite material and a preparation method and application thereof.
Background
Silicon is considered as an important negative electrode material for achieving high specific energy batteries in lithium ion batteries. Its theoretical specific capacity (Li)22Si5When the ratio is 4200mAh g-1，Li15Si4The time is 3580mAh g-1) Is 10 times higher than the traditional graphite (the graphite is 350-365mAh g)-1). In addition, the silicon has no pollution to the environment and is abundant in reserves. However, after 20 years of development, it was recognized that the application of high capacity silicon negative electrode materials in lithium ion batteries was still very difficult.
Si undergoes a 300% volume change during charge and discharge, and a large volume change causes active material to be exfoliated from the current collector, electrical contact between particles to be lost, and an unstable Solid Electrolyte Interface (SEI) to occur. These all cause capacity fading and rate performance deterioration. Compared with a Si negative electrode, the SiO negative electrode has lower theoretical specific capacity, but has higher cycling stability and low price, and is a negative electrode material with the most commercial prospect in silicon-based materials. However, SiO still has the defects of 150% volume expansion, poor conductivity and the like, and the application of the SiO in lithium ion batteries is also greatly limited. In order to improve these disadvantages, a large amount of work has been done to improve the performance by compounding a nanomaterial with excellent conductivity with SiO, or by surface coating with a material with good conductivity and mechanical properties. Among them, the SiO-C composite material has become a main research direction due to its low cost and excellent conductivity. In the traditional SiO-C composite mode, a carbon source and SiO are mixed in a solvent by a physical method, and the solvent is calcined and carbonized after being evaporated to dryness. This method is difficult to attach carbon to the surface of SiO particles and to play a role in alleviating volume expansion.
Disclosure of Invention
The invention aims to provide a silicon-carbon composite material with a hierarchical structure, and a preparation method and application thereof.
The invention also provides a lithium ion battery cathode material which comprises the silicon-carbon composite material with the hierarchical structure.
The invention also provides a lithium ion battery cathode, which comprises the lithium ion battery cathode material.
The invention provides a silicon-carbon composite material which comprises a silicon-based material and a carbon material, wherein the silicon-based composite material has a sphere-like shape, and the sphere-like shape is formed by mutually inserting the silicon-based material and the carbon material in a sheet form and then secondarily assembling the silicon-based material and the carbon material.
According to the silicon-carbon composite material of the present invention, the silicon-based material may be selected from at least one of silicon monoxide, silicon dioxide, and the like; for example, the silicon-based material may be selected from silicon monoxide.
According to the silicon-carbon composite material of the present invention, the carbon material may be derived from an inorganic carbon source and an organic carbon source. Wherein the inorganic carbon source may be selected from at least one of graphite, graphene, hard carbon, soft carbon, and the like, for example, the inorganic carbon source is selected from graphite. Wherein, the organic carbon source can be at least one selected from polyurethane, melamine, polyethyleneimine and the like; for example, the organic carbon source is selected from polyurethanes.
According to the silicon-carbon composite material of the present invention, the mass ratio of the silicon-based material and the carbon material may be 2:3 to 4:1, such as 1:1 to 3.5:1, illustratively 2:1, 3:1, 4: 1.
According to the silicon-carbon composite material of the present invention, the average particle size of the silicon-carbon composite material may be 15 to 70 μm, for example 20 to 60 μm, 30 to 50 μm, and exemplarily 40 μm.
The invention further provides a preparation method of the silicon-carbon composite material, which comprises the following steps:
(1) mixing and ball-milling a silicon-based material and an inorganic carbon source to obtain a composite material of the silicon-based material and the inorganic carbon source;
(2) and (2) mixing and stirring the composite material of the silicon-based material and the inorganic carbon source in the step (1) with an organic carbon source solution, performing centrifugal separation, drying and calcining to obtain the silicon-carbon composite material.
According to the production method of the present invention, in the step (1), the silicon-based material and the inorganic carbon source have the meanings as described above. The mass ratio of the silicon-based material to the inorganic carbon source can be 100 (1-80); for example, the ratio is 100 (5-60), 100 (25-35), for example, 100:50, 100:35, 100:30 or 100: 25.
According to the preparation method of the present invention, in the step (1), the silicon-based material and the inorganic carbon source may be separately subjected to sand grinding before being mixed, and the conditions for sand grinding may be the same or different, preferably the same. For example, the sanding temperature may be 20-30 ℃. The sanding rate is 1000 and 2800rpm, preferably 1800 and 2500rpm, and by way of example, the rate is 2000 rpm. Wherein the sanding time is 10-120min, preferably 30-60min, and as an example, 60 min.
According to the preparation method of the invention, in the step (1), the speed of the ball milling is 100-600rpm, preferably 200-400rpm, and as an example, the speed is 350 rpm. Wherein the ball milling time is 1-20h, preferably 5-15h, and as an example, the ball milling time is 10 h.
According to the preparation process of the present invention, in step (2), the organic carbon source has the meaning as described above.
According to the preparation method, in the step (2), the mass ratio of the used amount of the organic carbon source to the composite material obtained in the step (1) can be 100 (10-400); for example, 100 (50-350), 100 (80-320), for example, 100:80, 100:160, or 100: 320.
According to the preparation method of the present invention, the preparation process of the organic carbon source in step (2) comprises: and dissolving the organic carbon source into a solvent at the temperature of 20-30 ℃, and stirring to obtain the organic carbon source solution. Wherein, the solvent can be water and/or ethanol, and is preferably water. Wherein the stirring time can be 10-60min, such as 20-40min, and as an example, the stirring time is 30 min; the stirring rate is 100-600rpm, such as 200-500rpm, for example, 400 rpm. Further, the organic carbon source solution is a uniform viscous solution.
According to the preparation method of the invention, in the step (2), the stirring time is 1-8h, preferably 3-6h, and as an example, the stirring time is 3 h.
According to the preparation method of the invention, in the step (2), the stirring speed is 200-600rpm, preferably 300-400rpm, and as an example, the stirring speed is 400 rpm.
According to the preparation method of the present invention, in the step (2), the temperature of the drying is 70 to 100 ℃, preferably 80 to 100 ℃, and as an example, the temperature is 80 ℃.
According to the preparation method of the invention, in the step (2), the temperature of the calcination is 600-1200 ℃, preferably 800-1000 ℃, and as an example, the temperature is 800 ℃. Wherein the calcining time is 1-6h, preferably 2-4h, and as an example, the calcining time is 3 h. Further, the calcination is performed in an inert atmosphere, for example, an inert atmosphere such as argon or nitrogen.
According to an exemplary embodiment of the preparation method of the present invention, the method comprises the steps of:
(1) respectively carrying out sand milling treatment on the silicon-based material and an inorganic carbon source, mixing and ball milling to obtain a composite material of the silicon-based material and the inorganic carbon source;
(2) adding an organic carbon source into a solvent to prepare an organic carbon source solution;
(3) and (3) mixing and stirring the composite material of the silicon-based material and the inorganic carbon source in the step (1) and the organic carbon source solution in the step (2), centrifugally separating, drying and calcining to obtain the silicon-carbon composite material.
The invention also provides the application of the silicon-carbon composite material in a lithium ion battery cathode material or a lithium ion battery.
The invention further provides a lithium ion battery cathode which comprises the silicon-carbon composite material. Preferably, the negative electrode further includes a binder and a conductive agent. Preferably, the mass ratio of the conductive agent to the binder is (5-8): 1-3): 1; for example 8:1:1 or 7:2: 1. Wherein the binder may be selected from binders known in the art, such as sodium carboxymethylcellulose (CMC). The conductive agent may be selected from those known in the art, such as acetylene black.
The invention further provides a lithium ion battery, which comprises the silicon-carbon composite material or the lithium ion battery cathode.
The inventors have found that the organic carbon source binds the silicon-based material and the inorganic carbon source together orderly and tightly to assemble large particles having a diameter of about 50 μm. By changing experimental conditions, a composite material with excellent cycle stability and a composite material with excellent rate capability can be obtained. The recombination arrangement of the organic carbon source enables more dominant crystal faces to be exposed in the electrolyte, so that the transmission of lithium ions is promoted, and the electrochemical performance is improved.
The invention has the beneficial effects that:
1. in the silicon-carbon composite material prepared by the invention, an organic carbon source is added in the preparation process, so that the composite material has a sphere-like structure: is formed by secondary assembly of flaky particles and has the advantage of uniform particle size distribution.
2. The invention provides a preparation method of the material, and the preparation method has the characteristics of low cost, easiness in operation, short time consumption and the like.
3. Compared with pure silicon performance, the silicon-carbon composite material with the hierarchical structure is beneficial to improving the cycle stability of the silicon-based cathode for the lithium ion battery.
Drawings
FIG. 1 is a scanning electron microscope (scale: 50 μm) of a silicon carbon composite material of a hierarchical structure according to example 1 of the present invention.
FIG. 2 is a scanning electron microscope image (scale: 10 μm) of a silicon carbon composite material of a hierarchical structure of example 1 of the present invention.
Fig. 3 is a graph showing electrochemical properties of the silicon-carbon composite material having a hierarchical structure according to example 1 of the present invention.
FIG. 4 is a scanning electron micrograph (scale: 50 μm) of a silicon carbon composite material of a hierarchical structure of example 2 of the present invention.
FIG. 5 is a graph showing the electrochemical performance of the silicon-carbon composite material having a hierarchical structure according to example 2 of the present invention.
FIG. 6 is a scanning electron micrograph (scale: 20 μm) of a silicon carbon composite material having a hierarchical structure according to example 4 of the present invention.
Fig. 7 is a graph showing the electrochemical performance of the silicon-carbon composite material having a hierarchical structure according to example 4 of the present invention.
FIG. 8 is a scanning electron micrograph (scale: 1 μm) of a silicon monoxide graphite composite material of comparative example 1 of the present invention.
FIG. 9 is a graph of the electrochemical performance of comparative example 1 of a silicon monoxide graphite composite material of the present invention.
FIG. 10 is a scanning electron micrograph (scale: 50 μm) of comparative example 2 of SiO according to the present invention.
FIG. 11 is a graph showing the electrochemical properties of SiO in comparative example 2 according to the invention.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to specific embodiments. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
Unless otherwise indicated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.
Example 1
(1) And (3) putting the silicon monoxide into a sand mill, and sanding for 1h at the rotating speed of 2000rpm to prepare for standby. And (4) placing the graphite in a sand mill, and sanding for 1h at the rotating speed of 2000rpm to prepare for standby. Putting the silicon monoxide and the graphite into a ball mill according to the mass ratio of 2:1, and carrying out ball milling at 350rpm for 10 hours to obtain a silicon monoxide graphite composite material;
(2) dissolving 0.8g of polyurethane in water, stirring for 30min at 25 ℃, wherein the stirring speed is 400rpm, pouring the silicon monoxide graphite composite material obtained in the step (1) into the polyurethane solution, and stirring for 3h at 25 ℃, wherein the stirring speed is 400 rpm;
(3) and (3) centrifugally separating the suspension in the step (2), drying the suspension in vacuum at 80 ℃ for 12h, and calcining the material in a tubular furnace at 800 ℃ in an inert atmosphere for 3h to obtain the hierarchical silicon-carbon composite material.
Fig. 1 and 2 are scanning electron micrographs of the silicon-carbon composite material with a hierarchical structure prepared in example 1. As can be seen from FIGS. 1 and 2, the silicon-carbon composite material with the hierarchical structure has a sphere-like shape, is formed by interpenetration and reassembly of flaky silicon monoxide and graphite, and has uniform particle size and average particle size of 40 μm.
The silicon-carbon composite material with the hierarchical structure obtained in the embodiment comprises: the silicon monoxide and the carbon material are mixed according to the mass ratio of 2: 1; the silicon-carbon composite material has a sphere-like shape, and the sphere-like shape is formed by mutually inserting silicon monoxide and graphite in a sheet form and then carrying out secondary assembly.
The silicon-carbon composite material with the hierarchical structure obtained in the embodiment, acetylene black and an aqueous solution containing 2 wt% of sodium carboxymethylcellulose are mixed into slurry according to the mass ratio of 7:2:1, and the slurry is coated on a copper foil to obtain a pole piece for electrochemical test. Fig. 3 shows the electrochemical properties of the silicon-carbon composite material with a hierarchical structure prepared in example 1. As can be seen from FIG. 3, the first charge/discharge performance is excellent, the cycle stability and the cycle reversibility are high, and the first cycle specific discharge capacity reaches 1106.2mAh g-1At 400mA · g-1After the battery is circulated for 400 weeks under current, the discharge specific capacity can still reach 501.8 mAh.g-1。
Example 2
(1) And (3) putting the silicon monoxide into a sand mill, and sanding for 1h at the rotating speed of 2000rpm to prepare for standby. And (4) placing the graphite in a sand mill, and sanding for 1h at the rotating speed of 2000rpm to prepare for standby. Putting the silicon monoxide and the graphite into a ball mill according to the mass ratio of 4:1, and carrying out ball milling at 350rpm for 10 hours to obtain a silicon monoxide graphite composite material;
(2) dissolving 0.8g of polyurethane in water, stirring for 30min at 25 ℃, wherein the stirring speed is 400rpm, pouring the silicon monoxide graphite composite material obtained in the step (1) into the polyurethane solution, and stirring for 3h at 25 ℃, wherein the stirring speed is 400 rpm;
(3) and (3) centrifugally separating the suspension in the step (2), drying the suspension in vacuum at 80 ℃ for 12h, and calcining the material in a tubular furnace at 800 ℃ in an argon atmosphere for 3h to obtain the hierarchical silicon-carbon composite material.
FIG. 4 is a scanning electron micrograph of the silicon-carbon composite material with a hierarchical structure prepared in example 2. As can be seen from FIG. 4, the silicon-carbon composite material with the hierarchical structure has a sphere-like shape and is formed by inserting and then assembling flaky silicon monoxide and graphite.
The silicon-carbon composite material with the hierarchical structure obtained in the embodiment comprises: the silicon monoxide and the carbon material are mixed according to the mass ratio of 4: 1; the silicon-carbon composite material has a sphere-like shape, and the sphere-like shape is formed by mutually inserting silicon monoxide and graphite in a sheet form and then carrying out secondary assembly.
Fig. 5 shows the electrochemical performance of the silicon-carbon composite material with hierarchical structure prepared in example 2. As can be seen from FIG. 5, the cycle stability was inferior to that of example 1, and the specific first discharge capacity was 1210mAh g-1When the battery is cycled for 400 weeks, the specific discharge capacity can reach 470.2mAh g-1。
Example 3
(1) And (3) putting the silicon monoxide into a sand mill, and sanding for 1h at the rotating speed of 2000rpm to prepare for standby. And (4) placing the graphite in a sand mill, and sanding for 1h at the rotating speed of 2000rpm to prepare for standby. Putting the silicon monoxide and the graphite into a ball mill according to the mass ratio of 3:1, and carrying out ball milling at 350rpm for 10 hours to obtain a silicon monoxide graphite composite material;
(2) dissolving 0.8g of polyurethane in water, stirring for 30min at 25 ℃, wherein the stirring speed is 400rpm, pouring the silicon monoxide graphite composite material obtained in the step (1) into the polyurethane solution, and stirring for 3h at 25 ℃, wherein the stirring speed is 400 rpm;
(3) and (3) centrifugally separating the suspension in the step (2), drying the suspension in vacuum at 80 ℃ for 12h, and calcining the material in a tubular furnace at 800 ℃ in an argon atmosphere for 3h to obtain the hierarchical silicon-carbon composite material.
Example 4
(1) Putting the silicon monoxide into a sand mill, and sanding for 1h at the rotating speed of 2000rpm to prepare for standby; placing graphite in a sand mill, sanding for 1h at the rotating speed of 2000rpm, and preparing for later use; putting the silicon monoxide and the graphite into a ball mill according to the mass ratio of 2:3, and carrying out ball milling at 400rpm for 12 hours to obtain a silicon monoxide graphite composite material;
(2) dissolving 0.8g of polyurethane in water, stirring for 30min at 25 ℃, wherein the stirring speed is 400rpm, pouring the silicon monoxide composite material obtained in the step (1) into the polyurethane solution, and stirring for 3h at 25 ℃, wherein the stirring speed is 400 rpm;
(3) and (3) centrifugally separating the suspension in the step (2), drying the suspension in vacuum at 80 ℃ for 12h, and calcining the material in a tubular furnace at 800 ℃ in an argon atmosphere for 3h to obtain the hierarchical silicon-carbon composite material.
FIG. 6 is a scanning electron micrograph of a silicon carbon composite material with a hierarchical structure prepared in example 4. As can be seen from FIG. 6, the silicon-carbon composite material with a hierarchical structure has a sphere-like morphology and is formed by inserting and then assembling flaky silicon monoxide.
Fig. 7 shows the electrochemical performance of the silicon-carbon composite material with hierarchical structure prepared in example 4. As can be seen from FIG. 7, the cycle stability was inferior to that of example 1, and the specific first discharge capacity was 1825.6mAh g-1When the battery is cycled for 100 weeks, the specific discharge capacity can reach 455.6 mAh.g-1。
Comparative example 1
And (3) putting the silicon monoxide into a sand mill, and sanding for 1h at the rotating speed of 2000rpm to prepare for standby. And (4) placing the graphite in a sand mill, and sanding for 1h at the rotating speed of 2000rpm to prepare for standby. And putting the silicon monoxide and the graphite into a ball mill according to the mass ratio of 2:1, and carrying out ball milling at 350rpm for 10 hours to obtain the silicon monoxide ink composite material.
FIG. 8 shows a scanning electron micrograph of the SiO graphite composite prepared in comparative example 1. As can be seen from fig. 8: the composite material which is not stirred and mixed with the organic carbon source (such as polyurethane) only has a layered structure and is not assembled into spherical particles.
Mixing the silicon monoxide graphite composite material with acetylene black and aqueous solution containing 2 wt% of sodium carboxymethylcellulose in a mass ratio of 7:2:1 to form slurry, coating the slurry on a copper foil to obtain a pole piece, and carrying out electrochemical test. Fig. 9 shows the results of the electrochemical performance test of the electrode made of the composite material prepared in comparative example 1. As can be seen from FIG. 9, the cycle stability and cycle reversibility were general.
Comparative example 2
And (3) putting the silicon monoxide into a sand mill, and sanding for 1h at the rotating speed of 2000rpm to obtain the silicon monoxide material.
FIG. 10 shows a scanning electron microscope image of the SiO material prepared in comparative example 2. As can be seen from fig. 10: the silicon monoxide after sanding treatment is flaky and has uniform size.
And mixing the sanded silicon monoxide, acetylene black and an aqueous solution containing 2% of sodium carboxymethylcellulose into slurry according to the mass ratio of 7:2:1, coating the slurry on a copper foil to obtain a pole piece, and performing electrochemical test. Fig. 11 shows the results of electrochemical performance tests on electrodes made of the silicon monoxide material prepared in comparative example 2. As can be seen from fig. 11, the cycle stability and cycle reversibility were poor.
As can be seen from the comparison of fig. 2, 4, 8 and 10, the silicon-carbon composite material with a hierarchical structure is a sphere-like silicon-carbon composite material formed by the secondary assembly of layered graphite and silicon monoxide under the action of organic carbon source-polyurethane, and the particle size is uniform.
As can be seen from fig. 3, 5, 9 and 11, electrochemical test results of the silicon carbon composite having a hierarchical structure compared to the pure silicon monoxide and silicon monoxide graphite composite illustrate that: the hierarchical structure design not only improves the first-week coulomb efficiency, but also greatly improves the circulation stability and the circulation reversibility.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The silicon-carbon composite material is characterized by comprising a silicon-based material and a carbon material, wherein the silicon-based composite material has a sphere-like shape, and the sphere-like shape is formed by mutually inserting the silicon-based material and the carbon material in a sheet form and then secondarily assembling the silicon-based material and the carbon material.
2. The silicon-carbon composite according to claim 1, wherein the silicon-based material is selected from at least one of silicon monoxide, silicon and silicon dioxide;
the carbon material is selected from an inorganic carbon source and an organic carbon source, and the inorganic carbon source is selected from at least one of graphite, graphene, hard carbon and soft carbon; the organic carbon source is selected from at least one of polyurethane, melamine and polyethyleneimine.
3. The silicon-carbon composite material according to claim 1 or 2, wherein the mass ratio of the silicon-based material to the carbon material is 2:3 to 4: 1;
preferably, the average particle size of the silicon-carbon composite material is 15-70 μm.
4. A method of preparing a silicon-carbon composite material according to any one of claims 1 to 3, characterized in that the method comprises the steps of:
(1) mixing and ball-milling a silicon-based material and an inorganic carbon source to obtain a composite material of the silicon-based material and the inorganic carbon source;
(2) and (2) mixing and stirring the composite material of the silicon-based material and the inorganic carbon source in the step (1) with an organic carbon source solution, performing centrifugal separation, drying and calcining to obtain the silicon-carbon composite material.
5. The method for preparing the silicon-carbon composite material according to claim 4, wherein in the step (1), the mass ratio of the silicon-based material to the inorganic carbon source is 100 (1-80);
preferably, in the step (1), the silicon-based material and the inorganic carbon source are respectively subjected to sand milling before being mixed;
preferably, in the step (1), the ball milling speed is 100 and 600rpm, and the ball milling time is 1-20 h.
6. The method for preparing the silicon-carbon composite material according to claim 5, wherein in the step (2), the mass ratio of the amount of the organic carbon source to the composite material obtained in the step (1) is 100 (10-400);
preferably, the organic carbon source preparation process in step (2) comprises: dissolving the organic carbon source into a solvent at the temperature of 20-30 ℃, and stirring to obtain an organic carbon source solution; wherein, the solvent can be water and/or ethanol;
preferably, in the step (2), the stirring time is 1-8h, and the stirring speed is 200-600 rpm.
7. The method for preparing the silicon-carbon composite material according to claim 4 or 5, wherein in the step (2), the drying temperature is 70-100 ℃; the calcining temperature is 600-1200 ℃, and the calcining time is 1-6 h;
preferably, the calcination is carried out in an inert atmosphere.
8. Use of the silicon-carbon composite material according to any one of claims 1 to 3 in a negative electrode material for a lithium ion battery or in a lithium ion battery.
9. A lithium ion battery negative electrode, characterized in that it comprises a silicon-carbon composite material according to any one of claims 1 to 3.
10. A lithium ion battery comprising the silicon-carbon composite material according to any one of claims 1 to 3 or comprising the lithium ion battery negative electrode according to claim 9.
CN201911333064.2A 2019-12-23 2019-12-23 Hierarchical silicon-carbon composite material and preparation method and application thereof Pending CN110970611A (en)

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