CN117133907B - Carbon-coated silicon composite material and preparation method and application thereof - Google Patents

Carbon-coated silicon composite material and preparation method and application thereof Download PDF

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CN117133907B
CN117133907B CN202311393999.6A CN202311393999A CN117133907B CN 117133907 B CN117133907 B CN 117133907B CN 202311393999 A CN202311393999 A CN 202311393999A CN 117133907 B CN117133907 B CN 117133907B
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silicon
carbon
silicon powder
composite material
carbon source
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CN117133907A (en
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李源林
龚本利
苏豪祺
胡祥云
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Husong Intelligent Equipment Taicang 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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • 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
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention provides a carbon-coated silicon composite material and a preparation method and application thereof, wherein the preparation method comprises the following steps: dispersing an electrolyte dispersing agent and a carbon source in water to obtain a first dispersion, wherein the concentration of the electrolyte dispersing agent is 0.25-0.5mol/L, and the concentration of the carbon source is 0.5-1mol/L; mixing the first dispersion liquid with silicon powder, and performing a primary hydrothermal reaction to obtain a first solid; dispersing an electrolyte dispersing agent and a carbon source in water to obtain a second dispersion, wherein the concentration of the electrolyte dispersing agent is 0.05-0.2mol/L, and the concentration of the carbon source is 0.1-0.4mol/L; mixing the first solid with the second dispersion liquid, performing a secondary hydrothermal reaction to obtain a second solid, and carbonizing the second solid. The preparation method can obtain the carbon-coated silicon composite material with good coating effect and good conductivity, and the composite material is used for the battery and is beneficial to improving the stability and the conductivity of the battery.

Description

Carbon-coated silicon composite material and preparation method and application thereof
Technical Field
The invention relates to the field of silicon-carbon negative electrode materials, in particular to a carbon-coated silicon composite material, and a preparation method and application thereof.
Background
Among many negative electrode materials for lithium ion batteries, silicon-based materials are the most promising because they have high theoretical capacity, low operating voltage, and are resource-rich and environmentally friendly. At present, many researches on silicon-based anode materials are carried out, and the researches are mainly focused on defects of practical application.
In order to further improve the performance of silicon-based materials, it is necessary to start with the drawbacks of the material application. In recent years, efforts have been made to solve these drawbacks, such as synthesis of nano-silicon materials, development of porous or hollow structures, bonding of silicon to conductive materials, modification of nano-silicon materials, and research on surfaces of silicon-based materials and novel binders. At present, the carbon-coated silicon composite material can be used for relieving the problems of volume change and the like of silicon, but the carbon-coated silicon composite material still has a plurality of problems in the coating process, so that the conductivity of the obtained carbon-coated silicon composite material is influenced, and the exertion of the electrochemical performance of the carbon-coated silicon composite material is influenced.
Disclosure of Invention
The invention provides a preparation method of a carbon-coated silicon composite material, which can improve the carbon-coated silicon interface structure, so as to obtain the carbon-coated silicon composite material with good coating effect and good electric conductivity.
The invention also provides the carbon-coated silicon composite material prepared by the preparation method, and the carbon-coated silicon composite material has excellent structure and good conductivity, so that the carbon-coated silicon composite material is used for a battery, and the stability and the electrochemical performance of the battery can be improved.
The invention also provides a negative plate, which is used for a battery and can improve the stability and the conductivity of the battery because the negative plate comprises the carbon-coated silicon composite material.
The invention also provides a battery, which comprises the negative plate, so that the battery has excellent cycle performance and electrochemical performance.
In a first aspect, the invention provides a method for preparing a carbon-coated silicon composite material, comprising the following steps:
s1: dispersing an electrolyte dispersing agent and a carbon source in water to obtain a first dispersion, wherein the concentration of the electrolyte dispersing agent is 0.25-0.5mol/L, and the concentration of the carbon source is 0.5-1mol/L;
s2: the first dispersion liquid is mixed with silicon powder to obtain a first reaction liquid;
s3: the first reaction liquid is subjected to a primary hydrothermal reaction at 150-220 ℃ to obtain a first solid product;
s4: dispersing an electrolyte dispersing agent and a carbon source in water to obtain a second dispersion, wherein the concentration of the electrolyte dispersing agent is 0.05-0.2mol/L, and the concentration of the carbon source is 0.1-0.4mol/L;
s5: mixing the first solid product with the second dispersion liquid to obtain a second reaction liquid;
s6: the second reaction liquid is subjected to secondary hydrothermal reaction at the temperature of 100-145 ℃ to obtain a second solid product;
s7: carbonizing the second solid product in a protective atmosphere to obtain the silicon-on-carbon composite material;
in step S1 or step S4, the electrolyte dispersant is selected from one or more of lignin sulfonate, sulfate salt and naphthalene sulfonate.
Further, the silicon powder is one or more of granular silicon powder, flaky silicon powder and rod-shaped silicon powder.
Further, the silicon powder is mixed powder of granular silicon powder and flaky silicon powder with the mass ratio of 4-7:1.
Further, the particle size of the granular silicon powder is 30nm-1000nm; the particle size of the flaky silicon powder is 50nm-1000nm, and the thickness is 10nm-100nm; the length of the rod-shaped silicon powder is 80nm-1000nm, and the diameter is 50nm-400nm.
Further, in step S1 or step S4, the carbon source includes one or more of glucose, sucrose, and chitosan.
Further, the carbonization treatment is carried out at 650-1100 ℃ for 1-24 hours.
Further, in the first reaction liquid, the mass ratio of the carbon source to the silicon powder is 2-5:10; in the second reaction solution, the mass ratio of the carbon source to the first solid product is 0.1-3:10.
In a second aspect, the present invention provides a silicon-on-carbon composite material, which is prepared by the above preparation method.
In a third aspect, the invention provides a negative electrode sheet comprising the carbon-coated silicon composite material.
In a fourth aspect, the present invention provides a battery comprising the above-described negative electrode sheet.
The preparation method can improve the carbon-coated silicon interface structure, further obtain the carbon-coated silicon composite material with good coating effect and good conductivity, and the carbon-coated silicon composite material is used for the battery and can improve the stability and the conductivity of the battery.
Drawings
Fig. 1 is an SEM image of the carbon-coated silicon composite material of example 2.
Detailed Description
The present invention will be described in further detail below for the purpose of better understanding of the aspects of the present invention by those skilled in the art. The following detailed description is merely illustrative of the principles and features of the present invention, and examples are set forth for the purpose of illustration only and are not intended to limit the scope of the invention. All other embodiments, which can be made by those skilled in the art based on the examples of the invention without making any inventive effort, are intended to be within the scope of the invention.
In a first aspect, the invention provides a method for preparing a carbon-coated silicon composite material, comprising the following steps:
s1: dispersing an electrolyte dispersing agent and a carbon source in water to obtain a first dispersion, wherein the concentration of the electrolyte dispersing agent is 0.25-0.5mol/L, and the concentration of the carbon source is 0.5-1mol/L;
s2: the first dispersion liquid is mixed with silicon powder to obtain a first reaction liquid;
s3: the first reaction liquid is subjected to a primary hydrothermal reaction at 150-220 ℃ to obtain a first solid product;
s4: dispersing an electrolyte dispersing agent and a carbon source in water to obtain a second dispersion, wherein the concentration of the electrolyte dispersing agent is 0.05-0.2mol/L, and the concentration of the carbon source is 0.1-0.4mol/L;
s5: mixing the first solid product with the second dispersion liquid to obtain a second reaction liquid;
s6: the second reaction liquid is subjected to secondary hydrothermal reaction at the temperature of 100-145 ℃ to obtain a second solid product;
s7: carbonizing the second solid product in a protective atmosphere to obtain the silicon-on-carbon composite material;
in step S1 or step S4, the electrolyte dispersant is selected from one or more of lignin sulfonate, sulfate salt and naphthalene sulfonate.
The problem of poor controllability and the like in the coating process of the carbon-coated silicon in the traditional technology leads to poor carbon coating effect and influences the use of the carbon-coated silicon composite material. The preparation method provided by the invention realizes a coating effect superior to the prior art by controlling the means of raw materials, the process, parameters and the like of the hydrothermal reaction, and particularly can realize good coating aiming at silicon powder with specific size and shape. The reason for this is that: firstly, preparing a first dispersion liquid containing electrolyte dispersing agent with higher concentration, adsorbing and dispersing the dispersing agent on the surface of silicon powder, carrying out surface modification treatment on silicon particles, wherein more anions are adsorbed on the silicon particles, so that the silicon particles are negatively charged, repulsive force between the negative charges enables the silicon particles to be uniformly dispersed in a solution, the dispersing effect of the silicon particles in the solution is improved, and in the primary hydrothermal reaction process, a carbon source is polymerized at a proper rate to generate a polymer layer, so that the polymer layer is uniformly coated on the surfaces of the silicon particles; secondly, preparing a second dispersion liquid containing electrolyte dispersing agent and carbon source with lower concentration, carrying out surface modification on the first solid product, improving the dispersing effect of the first solid product in the solution, and carrying out secondary hydrothermal reaction, wherein the carbon source is polymerized at a milder rate in the process to generate a polymer layer, so that the carbon layer uniformly and tightly wraps the surface of the silicon particles; finally, the polymer layer wrapped on the surface of the silicon is dehydrogenated and deoxidized by carbonization treatment, so that the carbonization is realized to form a carbon layer, and the carbon-coated silicon composite material with good conductivity is obtained.
In step S1 and step S4, the electrolyte dispersants may be the same or different, and in order to better control the reaction process, the same electrolyte dispersant is preferable; the silicon powder of the invention is nano silicon powder, including but not limited to silicon powder with the grain diameter of 1-500nm, silicon powder with the grain diameter of 1-400nm, silicon powder with the grain diameter of 1-300nm, silicon powder with the grain diameter of 1-200nm, silicon powder with the grain diameter of 1-100nm, silicon powder with the grain diameter of 1-50nm and the like.
Illustratively, the lignosulfonate is sodium lignosulfonate, magnesium lignosulfonate, calcium lignosulfonate, or the like; the sulfate salt is isooctyl alcohol sodium sulfate, laureth sodium sulfate and the like; the naphthalene sulfonate is sodium naphthalene sulfonate formaldehyde polycondensate, potassium naphthalene sulfonate formaldehyde polycondensate and the like.
In a preferred embodiment, the silicon powder is one or more of granular silicon powder, flake silicon powder, and rod silicon powder.
The inventor finds that compared with granular silicon powder, flaky silicon powder and rod-shaped silicon powder are harder to uniformly and tightly coat the carbon layer, and the method can realize uniform and compact coating of the silicon powder in various forms by carrying out hydrothermal reaction of different condition parameters twice, so that the carbon-coated silicon composite material meets the use requirements of different scenes.
In a preferred embodiment, the silicon powder is a mixed powder of granular silicon powder and flaky silicon powder with the mass ratio of 4-7:1.
In a preferred embodiment, the particle size of the granular silicon powder is 30nm to 1000nm; the particle size of the flaky silicon powder is 50nm-1000nm, and the thickness is 10nm-100nm; the length of the rod-shaped silicon powder is 80nm-1000nm, and the diameter is 50nm-400nm.
It will be appreciated that the particle size (transverse dimension) of the sheet silicon powder should be greater than the size of the thickness (longitudinal dimension), for example, when the particle size of the sheet silicon powder is 800nm to 1000nm, the thickness is 10nm to 100nm; when the particle size of the flaky silicon powder is 50-100nm and the thickness is 10-40nm; the length of the rod-shaped silicon powder should be greater than the size of the diameter, for example, when the length of the rod-shaped silicon powder is 80nm to 100nm, the diameter is 50nm to 60nm.
In a preferred embodiment, the carbon source comprises one or more of glucose, sucrose and chitosan. In step S1 and step S4, the carbon sources may be the same or different, but the same carbon source is preferred for better control of the reaction process.
In a preferred embodiment, the time of the primary hydrothermal reaction is 1 to 24 hours; the time of the secondary hydrothermal reaction is 1-18h.
In a preferred embodiment, the carbonization treatment is carried out at a temperature of 650-1100 ℃ for a time of 1-24 hours.
As for the heating rate before the carbonization treatment, the present invention is not particularly limited, and the skilled person can adjust as required, for example, to heat up at a heating rate of 5 to 20℃per minute.
In a preferred embodiment, in the first reaction solution, the mass ratio of the carbon source to the silicon powder is 2-5:10; in the second reaction solution, the mass ratio of the carbon source to the first solid product is 0.1-3:10. In the embodiment, the tight cladding of the carbon layer on the silicon surface can be better ensured, and the electrical performance of the carbon-coated silicon composite material is further ensured.
In a preferred embodiment, in the first reaction solution, the mass ratio of the carbon source to the silicon powder is 2-5:10; in the second reaction solution, the mass ratio of the carbon source to the first solid product is 0.5-2:10.
In a second aspect, the present invention provides a silicon-on-carbon composite material, which is prepared by the above preparation method.
In a preferred embodiment, the silicon-on-carbon composite comprises a silicon core and a carbon layer at least partially surrounding the silicon core, the silicon core comprising at least two of particulate silicon, sheet silicon and rod silicon; the silicon core of each morphology is at least partially coated with the carbon layer, respectively.
In a specific embodiment, at least 90% of the surface area of the silicon core is coated with the carbon layer.
In another preferred embodiment, the carbon-coated silicon composite material comprises a silicon core and a carbon layer at least partially coating the silicon core, wherein the silicon core consists of granular silicon and sheet silicon; the silicon core of each form at least partially coats the carbon layer, and the inventor discovers that the silicon composite materials of the two combined forms can better play a synergistic effect, so that the subsequent battery can obtain better conductivity.
In one embodiment of the invention, the particle size of the carbon-coated silicon composite material is 500-1000nm.
In a third aspect, the present invention provides a negative electrode sheet, including the carbon-silicon composite material provided in the second aspect.
Illustratively, the negative electrode sheet includes a current collector and a negative electrode slurry coated on the current collector, the negative electrode slurry including: the carbon-coated silicon composite material, a conductive agent, an adhesive and a solvent; the binder may include any one or a combination of at least two of polyvinylidene fluoride, polyvinylpyrrolidone, sodium carboxymethylcellulose, sodium alginate and styrene-butadiene rubber; the solvent may include deionized water,Any one or a combination of at least two of methyl pyrrolidone and absolute ethyl alcohol; the conductive agent may include any one or a combination of at least two of conductive graphite, carbon nanotube conductive carbon black, acetylene black, ketjen black, vapor grown carbon fiber, and expanded graphite.
In a fourth aspect, the present invention provides a battery, including the negative electrode sheet provided in the third aspect.
The invention is further illustrated by the following examples:
the CAS numbers of the sodium lignin sulfonates used in the following examples or comparative examples were 8061-51-6; the CAS number of sodium alginate is 9005-38-3.
Example 1
The example provides a carbon-coated silicon composite material, the preparation method of which comprises the following steps:
s1: dissolving 10g of sucrose in 60mL of deionized water, ultrasonically dissolving for 30min, adding 10g of sodium lignin sulfonate into the solution, and ultrasonically dispersing for 1h to obtain a first dispersion liquid (wherein the concentration of the sodium lignin sulfonate is about 0.3mol/L and the concentration of the sucrose is about 0.5 mol/L);
s2: adding 50g of silicon particle powder (with the particle size of 150 nm) into the first dispersion liquid, and performing ultrasonic dispersion for 30min to obtain a first reaction liquid;
s3: pouring the first reaction liquid into a polytetrafluoroethylene reaction container, placing the polytetrafluoroethylene reaction container into a high-pressure reaction kettle, carrying out hydrothermal reaction at 150 ℃ for 24 hours, placing the product into a vacuum drying oven, and drying at 150 ℃ for 4 hours to obtain a first solid product;
s4: dissolving 10g of sucrose in 300mL of deionized water, ultrasonically dissolving for 30min, adding 20g of sodium lignin sulfonate into the solution, and ultrasonically dispersing for 1h to obtain a second dispersion liquid (wherein the concentration of the sodium lignin sulfonate is about 0.13mol/L and the concentration of the sucrose is about 0.1 mol/L);
s5: adding 100g of the first solid product into the second dispersion liquid, and performing ultrasonic dispersion for 30min to obtain a second reaction liquid;
s6: pouring the second reaction solution into a polytetrafluoroethylene reaction container, placing the polytetrafluoroethylene reaction container into a high-pressure reaction kettle, and performing hydrothermal reaction for 18 hours at the temperature of 100 ℃; placing the product in a vacuum drying oven, and drying at 150 ℃ for 4 hours to obtain a second solid product;
s7: and (3) placing the second solid product in a vacuum furnace, quickly heating to 650 ℃ under the flowing nitrogen atmosphere and normal pressure, keeping the temperature for 2 hours at a heating speed of 20 ℃/min, naturally cooling to room temperature, and grinding to obtain the nano particles of the carbon-coated silicon composite material.
Example 2
The example provides a carbon-coated silicon composite material, the preparation method of which comprises the following steps:
s1: dissolving 50g of sucrose in 150mL of deionized water, ultrasonically dissolving for 30min, adding 20g of sodium lignin sulfonate solution into the mixed solution, and ultrasonically dispersing for 1h to obtain a first dispersion liquid (wherein the concentration of sodium lignin sulfonate is about 0.25mol/L and the concentration of sucrose is about 1 mol/L);
s2: adding 100g of silicon particle powder (with the particle size of 200 nm) into the first dispersion liquid, and performing ultrasonic dispersion for 30min to obtain a first reaction liquid;
s3: pouring the first reaction liquid into a polytetrafluoroethylene reaction container, placing the polytetrafluoroethylene reaction container into a high-pressure reaction kettle, performing hydrothermal reaction at 220 ℃ for 18 hours, placing the product into a vacuum drying oven, and drying at 150 ℃ for 4 hours to obtain a first solid product;
s4: dissolving 20g of sucrose in 200mL of deionized water, ultrasonically dissolving for 30min, adding 20g of sodium lignin sulfonate into the mixed solution, and ultrasonically dispersing for 1h to obtain a second dispersion liquid (wherein the concentration of the sodium lignin sulfonate is about 0.2mol/L and the concentration of the sucrose is about 0.3 mol/L);
s5: adding 100g of the first solid product into the second dispersion liquid, and performing ultrasonic dispersion for 30min to obtain a second reaction liquid;
s6: pouring the second reaction solution into a polytetrafluoroethylene reaction container, placing the polytetrafluoroethylene reaction container into a high-pressure reaction kettle, and performing hydrothermal reaction for 12 hours at 140 ℃; placing the product in a vacuum drying oven, and drying at 150 ℃ for 4 hours to obtain a second solid product;
s7: and (3) placing the second solid product in a vacuum furnace, quickly heating to 650 ℃ under the flowing nitrogen atmosphere and normal pressure, keeping the temperature for 2 hours at a heating speed of 20 ℃/min, naturally cooling to room temperature, and grinding to obtain the nano particles of the carbon-coated silicon composite material.
Example 3
This example provides a silicon-on-carbon composite material, which is prepared by the same method as in example 2, except that the silicon particle powder is replaced with a flake silicon powder having a particle diameter of 200nm and a thickness of 50nm.
Example 4
The present example provides a silicon-on-carbon composite material, which is produced by the same method as in example 2, except that the silicon particle powder is replaced with a mixed powder of silicon particle powder and flake silicon powder in a mass ratio of 5:1, and the flake silicon has a particle diameter of 200nm and a thickness of 50nm.
Comparative example 1
The present example provides a silicon-on-carbon composite material, the preparation method of which is the same as that of example 2, except that the sodium lignin sulfonate concentration in the first dispersion is about 0.2mol/L and the sucrose concentration is about 0.3mol/L by changing the input amounts of sucrose and sodium lignin sulfonate; in the second dispersion, the concentration of sodium lignin sulfonate is about 0.25mol/L, and the concentration of sucrose is about 1mol/L.
Comparative example 2
The present example provides a silicon-on-carbon composite material, which is different from example 2 in that in step S3, the first reaction solution is poured into a polytetrafluoroethylene reaction vessel, placed in a high-pressure reaction vessel, subjected to hydrothermal reaction at 140 ℃ for 12 hours, then dried, and in step S6, the first reaction solution is poured into a polytetrafluoroethylene reaction vessel, placed in a high-pressure reaction vessel, subjected to hydrothermal reaction at 220 ℃ for 18 hours, and then dried.
Comparative example 3
The example provides a carbon-coated silicon composite material, the preparation method of which comprises the following steps:
s1: dissolving 50g of sucrose in 150mL of deionized water, ultrasonically dissolving for 30min, adding 20g of sodium lignin sulfonate solution into the mixed solution, and ultrasonically dispersing for 1h to obtain a first dispersion liquid (wherein the concentration of sodium lignin sulfonate is about 0.25mol/L and the concentration of sucrose is about 1 mol/L);
s2: adding 100g of silicon particle powder (with the particle size of 200 nm) into the first dispersion liquid, and performing ultrasonic dispersion for 30min to obtain a first reaction liquid;
s3: pouring the first reaction liquid into a polytetrafluoroethylene reaction vessel, placing the polytetrafluoroethylene reaction vessel into a high-pressure reaction kettle, performing hydrothermal reaction at 220 ℃ for 18 hours, placing the product into a vacuum drying oven, and drying at 150 ℃ for 4 hours to obtain the carbon-coated silicon composite material.
Application example 1
The example provides a series of negative plates, the preparation method of which comprises the following steps:
the carbon-coated silicon composite materials of each example and the comparative example are respectively mixed with conductive carbon black SP and sodium alginate in a mass ratio of 1:8:1, 50mL of water is added, stirring is carried out for 8 hours, mixed slurry is obtained, the mixed slurry is coated on copper foil, the thickness of the obtained coating film is 100 mu m, and vacuum drying is carried out for 6 hours at 100 ℃ to obtain a series of lithium ion battery cathodes.
Application example 2
This example provides a series of cells, the preparation method of which comprises the steps of:
a series of negative electrode sheets of application example 1 were assembled into a battery, respectively: in a glove box filled with argon, a button-type half cell with the specification CR 2032 (electrolyte: a mixed solution of ethylene carbonate, dimethyl carbonate and diethyl carbonate with the volume ratio of 1:1:1 was added with 2.0wt% of vinylene carbonate, a counter electrode: a metal lithium sheet, and a separator: celgard 2500), and the mixture was left to stand for 24 hours to obtain a series of button-type half cells with the specification CR 2032.
Characterization and testing
1) SEM test was performed on the silicon-on-carbon prepared in example 2, and the results are shown in fig. 1. As can be seen from fig. 1, the carbon source encapsulates the silicon and forms spherical carbon-encapsulated silicon particles.
2) The silicon-in-carbon composite material prepared in example 2 was dispersed in water for the ZETA potential test, and the test results showed that: the dispersion effect of the carbon-coated silicon composite material in the solution is good.
3) Electrochemical tests were carried out on a series of button-type half cells provided in application example 2, and constant current charge and discharge tests were carried out under conditions of a test voltage range of 0.01V-2.0V and a current density of 4200 mAh/g. The constant current charge and discharge test results are shown in table 1.
Table 1:
the above test results show that the electrical and cycle performance of the assembled battery can be further improved compared to the comparative example, since the carbon-coated silicon composite of the example achieves a better coating effect.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (9)

1. The preparation method of the carbon-coated silicon composite material is characterized by comprising the following steps of:
s1: dispersing an electrolyte dispersing agent and a carbon source in water to obtain a first dispersion, wherein the concentration of the electrolyte dispersing agent is 0.25-0.5mol/L, and the concentration of the carbon source is 0.5-1mol/L;
s2: the first dispersion liquid is mixed with silicon powder to obtain a first reaction liquid;
s3: the first reaction liquid is subjected to a primary hydrothermal reaction at 150-220 ℃ to obtain a first solid product;
s4: dispersing an electrolyte dispersing agent and a carbon source in water to obtain a second dispersion, wherein the concentration of the electrolyte dispersing agent is 0.05-0.2mol/L, and the concentration of the carbon source is 0.1-0.4mol/L;
s5: mixing the first solid product with the second dispersion liquid to obtain a second reaction liquid;
s6: the second reaction liquid is subjected to secondary hydrothermal reaction at the temperature of 100-145 ℃ to obtain a second solid product;
s7: carbonizing the second solid product in a protective atmosphere to obtain the silicon-on-carbon composite material;
in step S1 or step S4, the electrolyte dispersant is selected from one or more of lignin sulfonate, sulfate salt and naphthalene sulfonate;
in step S1 or step S4, the carbon source includes one or more of glucose, sucrose, and chitosan.
2. The method of manufacturing as defined in claim 1, wherein the silicon powder is one or more of granular silicon powder, flake silicon powder, and rod silicon powder.
3. The production method according to claim 2, wherein the silicon powder is a mixed powder of granular silicon powder and flake silicon powder in a mass ratio of 4-7:1.
4. A process according to claim 2 or 3, wherein the particulate silicon powder has a particle size of 30nm to 1000nm; the particle size of the flaky silicon powder is 50nm-1000nm, and the thickness is 10nm-100nm; the length of the rod-shaped silicon powder is 80nm-1000nm, and the diameter is 50nm-400nm.
5. The method according to claim 1, wherein the carbonization treatment is carried out at a temperature of 650-1100 ℃ for a time of 1-24 hours.
6. The preparation method according to claim 1, wherein the mass ratio of the carbon source to the silicon powder in the first reaction liquid is 2-5:10; in the second reaction solution, the mass ratio of the carbon source to the first solid product is 0.1-3:10.
7. A silicon-on-carbon composite material produced by the production method according to any one of claims 1 to 6.
8. A negative electrode sheet comprising the silicon-on-carbon composite material of claim 7.
9. A battery comprising the negative electrode sheet of claim 8.
CN202311393999.6A 2023-10-26 2023-10-26 Carbon-coated silicon composite material and preparation method and application thereof Active CN117133907B (en)

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CN105489855A (en) * 2015-11-25 2016-04-13 天津师范大学 Core-shell silicon carbon composite negative electrode material for high-capacity type lithium ion battery and preparation method therefor
CN109244425A (en) * 2018-10-31 2019-01-18 四川创能新能源材料有限公司 A kind of preparation method of nano-silicone wire/carbon material and its application in lithium battery
CN110797512A (en) * 2018-08-02 2020-02-14 多氟多化工股份有限公司 Silicon-carbon negative electrode material, lithium ion battery negative electrode and lithium ion battery

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CN105489855A (en) * 2015-11-25 2016-04-13 天津师范大学 Core-shell silicon carbon composite negative electrode material for high-capacity type lithium ion battery and preparation method therefor
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