CN110571415B - Silicon-carbon negative electrode material and preparation method thereof - Google Patents

Silicon-carbon negative electrode material and preparation method thereof Download PDF

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CN110571415B
CN110571415B CN201910753678.XA CN201910753678A CN110571415B CN 110571415 B CN110571415 B CN 110571415B CN 201910753678 A CN201910753678 A CN 201910753678A CN 110571415 B CN110571415 B CN 110571415B
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silicon
carbon
expanded graphite
graphite
negative electrode
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CN110571415A (en
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尹周澜
马兴月
丁治英
童汇
张东材
喻帅
李由
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Central South University
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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
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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 embodiment of the invention provides a silicon-carbon cathode material and a preparation method thereof, the silicon-carbon cathode material comprises a catalytic graphite layer and three-dimensional expanded graphite coated in the catalytic graphite layer, nano-silicon is embedded in the three-dimensional expanded graphite, and the three-dimensional expanded graphite and the silicon are coated by the catalytic graphite, so that a three-dimensional structure taking the expanded graphite as a structural matrix is constructed, a buffer space is provided for the volume expansion of the silicon, the problem of volume change of the silicon-based material in the lithium ion de-intercalation process in the prior art is solved, and the silicon-carbon cathode material is good in material stability and strong in oxidation resistance. The preparation method of the silicon-carbon cathode material has the advantages of low equipment requirement, low energy consumption, simple steps, high controllability and easy industrial production.

Description

Silicon-carbon negative electrode material and preparation method thereof
Technical Field
The invention belongs to the technical field of lithium battery preparation, and particularly relates to a silicon-carbon negative electrode material and a preparation method thereof.
Background
The lithium ion battery has the advantages of high performance, high safety, environmental friendliness and the like, and is the secondary battery with the greatest development prospect and application prospect at present. The energy density of the battery mainly depends on electrode materials, and graphite is used as a negative electrode material of a commercial lithium ion battery, and due to the safety problem caused by low theoretical specific capacity (372mAh/g) and very low working voltage (close to Li/Li +), the traditional graphite negative electrode cannot meet the energy density requirement of the next generation lithium ion battery.
The silicon-based material has the advantages of high theoretical specific capacity (3579mAh/g), low lithium removal potential (0.02-0.6V vs. Li +/Li), environmental friendliness, abundant reserves and the like, and is considered to be the next generation high energy density lithium ion battery cathode material with the highest potential for replacing graphite.
The volume change of the silicon-based material in the lithium ion deintercalation process is as high as 300-400%, so that electrode materials are easily pulverized and shed, electrolyte and lithium ions are consumed, and the cycling stability is poor, so that the commercial application of the silicon-based material as a lithium battery negative electrode is limited. In order to solve the above problems, there are two main approaches in the prior art: firstly, directly carry out structural design to the silicon material, include: solid structure designs such as thin films, nanowires and nanorods and hollow structure designs such as nanotubes, hollow spheres and porous silicon; and secondly, introducing other functional materials to be compounded with the silicon-based materials, and comprehensively optimizing the structural design, such as metal material modification, conductive carbon material modification, complex structural design optimization and the like. However, none of the prior art adequately addresses the problem of volume change of silicon-based materials during the process of lithium ion deintercalation.
Disclosure of Invention
In order to solve the problem that the volume change of a silicon-based material is large in the lithium ion deintercalation process in the prior art, an object of an embodiment of the present invention is to provide a silicon-carbon negative electrode material, where the silicon-carbon material includes a catalytic graphite layer and three-dimensional expanded graphite coated inside the catalytic graphite layer, and nano-silicon is embedded in the three-dimensional expanded graphite, so as to provide a buffer space for the volume expansion of silicon, and solve the problem of the volume change of the silicon-based material in the lithium ion deintercalation process in the prior art. The second purpose of the embodiments of the present invention is to provide a method for preparing the silicon-carbon negative electrode material.
In order to achieve the purpose, the embodiment of the invention adopts the following technical scheme:
the silicon-carbon negative electrode material comprises a catalytic graphite layer and three-dimensional expanded graphite coated in the catalytic graphite layer, wherein nano silicon is embedded in the three-dimensional expanded graphite.
Wherein, the catalytic graphite layer refers to a graphite layer formed after metal catalysis.
The preparation method of the silicon-carbon negative electrode material comprises the following steps:
s1: uniformly mixing expanded graphite, nano-silicon, a carbon source and a catalyst precursor, and heating and evaporating to dryness to obtain a precursor;
s2: and (5) sintering the precursor in the step S1 in an inert atmosphere, and then washing and drying to obtain the silicon-carbon negative electrode material.
Expanded Graphite (EG) is a loose, porous, vermicular and novel functional carbon material obtained by intercalating, washing, drying and high-temperature bulking natural Graphite flakes. EG has excellent properties such as cold and heat resistance, corrosion resistance, self-lubrication and the like of natural graphite, and also has softness, compression resilience, adsorptivity, ecological environment compatibility, biocompatibility and radiation resistance which are not possessed by natural graphite. The expanded graphite can instantaneously expand 150-300 times in volume when meeting high temperature, and is changed into a worm shape from a sheet shape, so that the expanded graphite has a loose structure, is porous and bent, has enlarged surface area, improved surface energy and enhanced adsorption flake graphite force, and can be automatically embedded between the worm-shaped graphite, thereby having good softness, rebound resilience and plasticity.
In step S1, in the process of mixing the nano-silicon and the expanded graphite, the nano-silicon enters the three-dimensional layered structure of the expanded graphite.
In step S2, the carbon source is sintered to generate catalytic graphite under the action of the catalyst reduced to metal, and the catalytic graphite is uniformly coated on the surface of the three-dimensional expanded graphite.
The preparation method of the expanded graphite comprises the following steps:
preparing graphite oxide from the intermediate phase carbon microspheres of commercial materials by a classical Hummer's method, and sintering the graphite oxide for 10-30 min at 950 ℃ by using a tubular furnace to obtain the expanded graphite.
The preparation method of the graphite oxide comprises the following steps:
(1) placing mesocarbon microbeads and 2.5g of sodium nitrate in a 1000mL three-necked flask, adding sulfuric acid, and stirring for 15 min;
(2) the reaction temperature was lowered to 4 ℃ and KMnO was slowly added4Stirring for 3 hours at low temperature;
(3) raising the reaction temperature to 35 ℃, stirring at a medium temperature for 3 hours, and adding 200mL of deionized water;
(4) the reaction temperature was raised to 98 ℃ and 15mL of 30% H were added2O2Stirring at high temperature for 5 h;
(5) cooling to room temperature, and centrifugally washing and separating a reaction product to obtain the graphite oxide.
The average particle size D50 of the nano silicon is less than 100 nm.
Preferably, the average particle size D50 of the nano-silicon is less than 80 nm.
Preferably, the carbon source comprises glucose, sucrose, starch, citric acid, ascorbic acid.
Preferably, the mass ratio of the expanded graphite to the nano silicon to the carbon source is (0.2-0.6): (0.6-1.0): (3-9).
Preferably, the catalyst precursor comprises iron chloride, cobalt chloride, nickel chloride, iron nitrate, iron sulfate, iron acetate, cobalt sulfate, cobalt acetate, cobalt nitrate, nickel sulfate, and nickel acetate.
When the carbon source is glucose and the catalyst precursor is cobalt acetate, the cobalt acetate is reduced into metal cobalt under a high-temperature condition and is used as a catalyst for generating catalytic graphite, and the carbon source can generate catalytic graphite under the catalysis of the metal cobalt and uniformly coats the surface of the three-dimensional expanded graphite.
Preferably, the addition amount of the catalyst precursor is 1/4-1/2 of the mass of the carbon source.
Preferably, in step S1, the mass ratio of the expanded graphite to the nano-silicon is 1: (1-3).
Preferably, the inert atmosphere in step S2 refers to one of argon and nitrogen.
Preferably, the sintering temperature in the step S2 is 800-1000 ℃.
The sintering can further carbonize the material and improve the conductivity of the material.
Preferably, the preparation method comprises, before the washing and drying of step S2, soaking the sintered product with hydrochloric acid.
The purpose of the hydrochloric acid washing is to remove metallic cobalt from the material, preferably 10% hydrochloric acid is used.
When the silicon-carbon negative electrode material provided by the embodiment of the invention is prepared into an electrode, the specific method comprises the following steps:
uniformly mixing the silicon-carbon negative electrode material, the conductive carbon black and the binder in a ratio of 7:2:1, adding a solvent to prepare slurry, coating the slurry on a copper foil, and drying at 60 ℃ to obtain the electrode material of catalytic graphite coated with expanded graphite and silicon.
Wherein the binder is any one of sodium alginate and sodium carboxymethyl cellulose.
The solvent comprises at least one of water and ethanol.
According to the silicon-carbon negative electrode material disclosed by the embodiment of the invention, the outer catalytic graphite layer coats the material, so that the volume expansion can be relieved, and the three-dimensional expanded graphite can also relieve the volume expansion of the nano-silicon embedded in the material. The three-dimensional structure of the expanded graphite can relieve the volume expansion of the nano silicon and is a good three-dimensional conductive network.
The embodiment of the invention has the beneficial effects
1. The embodiment of the invention provides a silicon-carbon negative electrode material, which comprises a catalytic graphite layer formed by metal catalysis and three-dimensional expanded graphite coated in the catalytic graphite layer, wherein nano silicon is embedded in the three-dimensional expanded graphite, and the three-dimensional expanded graphite and the silicon are coated by the metal catalytic graphite, so that a three-dimensional structure taking the expanded graphite as a structural matrix is constructed, a buffer space is provided for the volume expansion of the silicon, the problem of volume change of the silicon-based material in the lithium ion de-intercalation process in the prior art is solved, and the material has good stability and strong oxidation resistance;
2. according to the silicon-carbon negative electrode material provided by the embodiment of the invention, the expanded mesocarbon microbeads (namely the expanded graphite) can be used as a conductive matrix and play a role in enhancing the conductivity of the material, the coating of the catalytic graphite layer further increases the conductivity of the material, and silicon particles can be prevented from falling from gaps of the expanded graphite;
3. according to the silicon-carbon negative electrode material provided by the embodiment of the invention, the initial raw material is the commercialized mesocarbon microbeads, silicon is industrial waste silicon, both the mesocarbon microbeads and the silicon are easy to prepare in large quantities, and the silicon-carbon negative electrode material is prepared while the waste silicon is fully utilized;
4. the preparation method of the silicon-carbon cathode material provided by the embodiment of the invention has the advantages of low equipment requirement, low energy consumption, simple steps, high controllability and easiness in industrial production.
Drawings
FIG. 1 is a scanning electron micrograph of the expanded graphite prepared in example 5.
Fig. 2 is a scanning electron microscope image of the silicon carbon negative electrode material prepared in example 5.
Fig. 3 is a graph of the first charge-discharge specific capacity of the battery pole piece prepared in example 6.
Fig. 4 is a cycle performance test chart of the battery pole piece prepared in example 6.
Detailed Description
The embodiment of the invention provides a silicon-carbon negative electrode material, which comprises a catalytic graphite layer formed by metal catalysis and three-dimensional expanded graphite coated in the catalytic graphite layer, wherein nano silicon is embedded in the three-dimensional expanded graphite to provide a buffer space for the volume expansion of silicon, and the problem of volume change of a silicon-based material in the lithium ion de-intercalation process in the prior art is solved. The embodiment of the invention also provides a preparation method of the silicon-carbon negative electrode material.
In order to better understand the above technical solutions, the above technical solutions will be described in detail with reference to specific embodiments.
Example 1
The embodiment provides a silicon-carbon cathode material which comprises a catalytic graphite layer and three-dimensional expanded graphite coated inside the catalytic graphite layer, wherein nano silicon is embedded in the three-dimensional expanded graphite.
Wherein, the catalytic graphite layer refers to a catalytic graphite layer formed after metal catalysis.
Example 2
The embodiment provides a preparation method of expanded graphite, which comprises the following steps:
preparing graphite oxide from the intermediate phase carbon microspheres of commercial materials by a classical Hummer's method, and sintering the graphite oxide by using a tubular furnace at 950 ℃ for 10-30 min to obtain the expanded graphite.
The preparation method of the graphite oxide comprises the following steps:
(1) placing mesocarbon microbeads and 2.5g of sodium nitrate in a 1000mL three-necked flask, adding sulfuric acid, and stirring for 15 min;
(2) the reaction temperature was lowered to 4 ℃ and 16g of KMnO was slowly added4Stirring for 3 hours at low temperature;
(3) raising the reaction temperature to 35 ℃, stirring at a medium temperature for 3 hours, and adding 200mL of deionized water;
(4) the reaction temperature was raised to 98 ℃ and 15mL of 30% H were added2O2Stirring at high temperature for 5 h;
(5) cooling to room temperature, and centrifugally washing and separating a reaction product to obtain the graphite oxide.
Example 3
The embodiment provides a preparation method of a silicon-carbon negative electrode material, which comprises the following steps:
s1: uniformly mixing expanded graphite, nano-silicon, a carbon source and a catalyst precursor, and heating and evaporating to dryness to obtain a precursor;
s2: and (5) sintering the precursor in the step S1 in an inert atmosphere, and then washing and drying to obtain the silicon-carbon cathode material.
In step S1, in the process of mixing the nano-silicon and the expanded graphite, the nano-silicon enters the three-dimensional layered structure of the expanded graphite.
In step S2, the carbon source is sintered to generate catalytic graphite under the action of the metal catalyst, and the catalytic graphite is uniformly coated on the surface of the three-dimensional expanded graphite.
Wherein the average particle size D50 of the nano silicon is less than 100 nm.
Carbon sources include glucose, sucrose, starch, citric acid and ascorbic acid.
The mass ratio of the expanded graphite to the nano silicon to the carbon source is (0.2-0.6): (0.6-1.0): (3-9).
The catalyst precursor includes iron chloride, cobalt chloride, nickel chloride, iron nitrate, iron sulfate, iron acetate, cobalt sulfate, cobalt acetate, cobalt nitrate, nickel sulfate, and nickel acetate.
When the carbon source is glucose and the catalyst precursor is cobalt acetate, the cobalt acetate is reduced into metal cobalt under a high-temperature condition and is used as a catalyst for generating catalytic graphite, and the carbon source can generate catalytic graphite under the catalysis of the metal cobalt and uniformly coats the surface of the three-dimensional expanded graphite.
The addition amount of the catalyst precursor is 1/4-1/2 of the mass of the carbon source.
In step S1, the mass ratio of the expanded graphite to the nano silicon is 1: (1-3).
The inert atmosphere of step S2 refers to one of argon and nitrogen.
The sintering temperature in the step S2 is 800-1000 ℃. The sintering can further carbonize the material and improve the conductivity of the material.
The preparation method also comprises the step of soaking the sintered product by hydrochloric acid before washing and drying in the step S2. The purpose of the hydrochloric acid washing is to remove metallic cobalt from the material, preferably 10% hydrochloric acid is used.
Example 4
The embodiment provides a method for preparing an electrode by using a silicon-carbon negative electrode material, which comprises the following specific steps:
uniformly mixing the silicon-carbon negative electrode material, the conductive carbon black and the binder in a ratio of 7:2:1, adding a solvent to prepare slurry, coating the slurry on a copper foil, and drying at 60 ℃ to obtain the electrode material of catalytic graphite coated with expanded graphite and silicon.
Wherein the binder is any one of sodium alginate and sodium carboxymethyl cellulose.
The solvent comprises at least one of water and ethanol.
According to the silicon-carbon negative electrode material disclosed by the embodiment of the invention, the outer catalytic graphite layer coats the material, so that the volume expansion can be relieved, and the three-dimensional expanded graphite can also relieve the volume expansion of the nano-silicon embedded in the material. The three-dimensional structure of the expanded graphite can relieve the volume expansion of the nano silicon and is a good three-dimensional conductive network.
Example 5
According to the methods of the embodiments 2 to 4, the example actually prepares a silicon-carbon anode material, which specifically comprises the following steps:
firstly, preparing expanded graphite:
(1) taking 8g of mesocarbon microbeads and 2.5g of sodium nitrate in a 1000mL three-necked flask, adding 200mL of concentrated sulfuric acid, and stirring at room temperature for 15 min;
(2) when the reaction temperature is reduced to about 4 ℃, 16g of KMnO is slowly added4Stirring for 3 hours at low temperature;
(3) raising the reaction temperature to 38 ℃, stirring at a medium temperature for 3 hours, and adding 400mL of deionized water;
(4) when the reaction temperature rises to 98 ℃, adding 40mL of 30% hydrogen peroxide, and stirring at high temperature for 5 hours;
(5) and (3) washing, filtering and drying the product, and putting the product into a preheated tubular furnace, wherein the temperature is 950 ℃, and the sintering time is 10-30 min, so that the expanded graphite can be obtained.
Preparing a silicon-carbon negative electrode material:
s1: mixing expanded graphite with silicon according to a ratio of 1:1, and adding glucose and cobalt acetate according to a ratio of 3: 1;
s2: and (3) sintering the mixed sample in an inert atmosphere at 900 ℃, and washing and drying the obtained product to obtain the silicon-carbon cathode material.
Preparing a battery pole piece:
taking 70mg of silicon-carbon negative electrode material, a conductive agent and a binder, mixing the materials in a ratio of 7:2:1, mixing, grinding and smearing.
And after the pole piece is dried, stamping the pole piece into a battery pole piece for electrochemical performance test.
The microstructure of the expanded graphite prepared in this example was observed by a scanning electron microscope, and as shown in FIG. 1, it can be seen from FIG. 1 that the structure of the prepared expanded graphite was a three-dimensional structure having a large number of voids.
The microstructure of the silicon-carbon negative electrode material prepared in the present example is observed by a scanning electron microscope, as shown in fig. 2, it can be seen from fig. 2 that nano-silicon enters the three-dimensional structural matrix of the expanded graphite.
Example 6
According to the methods of the embodiments 2 to 4, the example actually prepares a silicon-carbon anode material, which specifically comprises the following steps:
firstly, preparing expanded graphite:
(1) taking 8g of mesocarbon microbeads and 2.5g of sodium nitrate in a 1000mL three-necked flask, adding 200mL of concentrated sulfuric acid, and stirring at room temperature for 15 min;
(2) reducing the reaction temperature to about 4 ℃, slowly adding 18g of potassium permanganate, and stirring at low temperature for 3 hours;
(3) raising the reaction temperature to 38 ℃, stirring at a medium temperature for 3 hours, and adding 400mL of deionized water;
(4) when the reaction temperature rises to 98 ℃, adding 40mL of 30% hydrogen peroxide, and stirring at high temperature for 5 hours;
(5) and (3) washing, filtering and drying the product, and putting the product into a preheated tubular furnace, wherein the temperature is 950 ℃, and the sintering time is 10-30 min, so that the expanded graphite can be obtained.
Preparing a silicon-carbon negative electrode material:
s1: mixing expanded graphite and nano silicon according to a certain proportion, and adding glucose and cobalt acetate according to a certain proportion;
s2: and (3) sintering the mixed sample in an inert atmosphere at 900 ℃, and washing and drying the obtained product to obtain the silicon-carbon cathode material.
Preparing a battery pole piece:
taking 70mg of silicon-carbon negative electrode material, a conductive agent and a binder, mixing the materials in a ratio of 7:2:1, mixing, grinding and smearing. And after the pole piece is dried, stamping the pole piece into a battery pole piece for electrochemical performance test.
The lithium ion battery composite negative electrode material of the embodiment is prepared into a lithium ion battery, and the cycle performance of the lithium ion battery composite negative electrode material is tested, wherein the cycle performance is shown in fig. 3, and as seen from fig. 3, the first discharge specific capacity of the material is 1386.5mAh/g, the first charge specific capacity is 825.6mAh/g, and the first coulombic efficiency is 59.54%. As can be seen from FIG. 4, after 40 cycles, the charging specific capacity is still 896.3mAh/g, the capacity retention rate is 108.5%, and the material is activated in the process of cyclic charge and discharge. Therefore, the lithium ion battery composite negative electrode prepared by using the silicon-carbon negative electrode material disclosed by the embodiment of the invention has high cycle stability.
The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. The silicon-carbon negative electrode material is characterized by comprising a catalytic graphite layer and three-dimensional expanded graphite coated in the catalytic graphite layer, wherein nano silicon is embedded in the three-dimensional expanded graphite;
the preparation method of the silicon-carbon negative electrode material comprises the following steps:
s1: uniformly mixing expanded graphite, nano-silicon, a carbon source and a catalyst precursor, and heating and evaporating to dryness to obtain a precursor;
s2: and (5) sintering the precursor in the step S1 in an inert atmosphere, and then washing and drying to obtain the silicon-carbon negative electrode material.
2. The silicon-carbon anode material of claim 1, wherein the nano-silicon has an average particle size D50 of less than 100 nm.
3. The silicon-carbon anode material of claim 1, wherein the carbon source is selected from glucose, sucrose, starch, citric acid, and ascorbic acid.
4. The silicon-carbon anode material as claimed in claim 1, wherein in step S1, the mass ratio of the expanded graphite, the nano-silicon and the carbon source is (0.2-0.6): (0.6-1.0): (3-9).
5. The silicon-carbon anode material of claim 1, wherein the catalyst precursor is selected from the group consisting of iron chloride, cobalt chloride, nickel chloride, iron nitrate, iron sulfate, iron acetate, cobalt sulfate, cobalt acetate, cobalt nitrate, nickel sulfate, and nickel acetate.
6. The silicon-carbon anode material as claimed in claim 1, wherein the catalyst precursor is added in an amount of 1/4-1/2 mass% based on the mass of the carbon source.
7. The silicon-carbon anode material as claimed in claim 1, wherein in step S1, the mass ratio of the expanded graphite to the nano-silicon is 1: (1-3).
8. The silicon-carbon negative electrode material as claimed in claim 1, wherein the sintering temperature in step S2 is 800-1000 ℃.
9. The silicon-carbon anode material as claimed in claim 1, wherein the preparation method comprises soaking the sintered product with hydrochloric acid before washing and drying in step S2.
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CN109713265B (en) * 2018-12-21 2021-01-12 桑德新能源技术开发有限公司 Silicon-carbon negative electrode material and preparation method thereof
CN109638269A (en) * 2018-12-29 2019-04-16 湖南中科星城石墨有限公司 A kind of silicon/expanded graphite/agraphitic carbon composite material and preparation method

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