CN107658457B - SiO for fused salt electrolysis2-Gc/C composite electrode and preparation method thereof - Google Patents

SiO for fused salt electrolysis2-Gc/C composite electrode and preparation method thereof Download PDF

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CN107658457B
CN107658457B CN201710935830.7A CN201710935830A CN107658457B CN 107658457 B CN107658457 B CN 107658457B CN 201710935830 A CN201710935830 A CN 201710935830A CN 107658457 B CN107658457 B CN 107658457B
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graphite
carbon
silicon dioxide
composite electrode
amorphous carbon
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CN107658457A (en
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赵春荣
杨娟玉
于冰
李进
卢世刚
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China Automotive Battery Research Institute 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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

SiO for fused salt electrolysis2The composite electrode is formed by compounding raw materials including silicon dioxide, a graphite additive and amorphous carbon, wherein the graphite additive is graphite with the surface coated with pyrolysis carbon, and the amorphous carbon is dispersed between the silicon dioxide and the graphite additive. The amorphous carbon and the cracked carbon coated on the surface of the graphite introduced into the composite electrode not only increase the electrode reaction active points, but also react with the Si generated by electrolysis to generate SiC to prevent the connection and growth of Si particles, thereby playing a role in reducing the granularity of the Si particles; the amount of SiC in the electrolytic product after the simultaneous introduction of the amorphous carbon and the cracked carbon is controllable, i.e., the amount of SiC in the electrolytic product is adjusted by controlling the amounts of the amorphous carbon and the cracked carbon. The carbon coating of the in-situ cracking on the graphite surface also plays a role in increasing the roughness of the graphite surface and enhancing the combination of the graphite and the silicon dioxide.

Description

SiO for fused salt electrolysis2-Gc/C composite electrode and preparation method thereof
Technical Field
The invention relates to SiO for molten salt electrolysis2a-Gc/C composite electrode and a preparation method thereof, belonging to the technical field of molten salt electrolysis.
Background
The development of a high-energy-density power battery, the improvement of the driving range of the pure electric vehicle and the expansion of the application range of the electric vehicle are key points for breaking through the bottleneck of the development of the electric vehicle industry. The electrode material with high specific capacity is the simplest and most effective method for improving the energy density of the battery. The current commercially used negative electrode materials are mainly carbon materials, but the theoretical specific capacity of the carbon negative electrode materials is very close to the theoretical capacity (372mAh/g), and the improvement of the battery performance by improving the battery preparation process is difficult to make breakthrough progress, so that the research and development of a new generation of negative electrode materials with high specific capacity are particularly urgent.
Metals such as Si, Sn, Al and Sb are high-capacity negative electrode materials which are researched more, wherein silicon has more than 10 times of theoretical electrochemical capacity (the theoretical capacity is 4200mAh/g) higher than that of carbon materials widely used at present, and is considered to be a high-specific-energy lithium ion battery negative electrode material with a very promising prospect. The main problem of the method is that the volume is obviously changed (volume change rate: 280-360%) in the processes of lithium removal and lithium insertion, so that the material structure is damaged and mechanically pulverized, the electrode materials and the electrode materials are separated from a current collector, and further the electrical contact is lost, so that the capacity is rapidly attenuated. Therefore, how to improve the cycling stability of the silicon negative electrode and make the silicon negative electrode practical becomes the research focus of the materials. There are two main solutions to this problem: firstly, the silicon is nanocrystallized; and the other is to adopt a silicon composite material.
For example, CN106784698A discloses the electrolysis of SiO2The amorphous carbon/C electrode directly obtains the Si/SiC/C composite material. The nano Si and SiC materials generated in situ by the method are compounded with graphite in situ, wherein the nano SiC and the nano Si materials are generated in dependence and are fully contacted and uniformly dispersed among graphite sheets or particles. The SiC nanowire has higher mechanical strength, so that the damage of internal stress generated by volume expansion of the Si negative electrode in the lithium intercalation and deintercalation process to an electrode structure can be relieved, and the mechanical property of the Si negative electrode is improved; the graphite can improve the conductivity of the Si negative electrode and buffer the internal stress generated by volume expansion in the process of lithium intercalation and deintercalation of the Si negative electrode, thereby improving the cycle performance of the Si electrode. The amorphous carbon in this invention provides only the raw material for SiC formation, but does not significantly enhance the bonding of silica to graphite.
CN105280879A discloses a silicon dioxide/carbon composite porous electrode and a preparation method thereof, wherein the microstructure of the porous electrode can be controlled by adjusting the content of silicon dioxide, and the method is simple and easy to implement. However, the invention does not mention the addition of amorphous carbon and the role that amorphous carbon plays in it.
Disclosure of Invention
Accordingly, an object of the present invention is to provide SiO for molten salt electrolysis having excellent properties2The amorphous carbon and the cracked carbon coated on the surface of the graphite are introduced into the composite electrode, so that electrode reaction active points are increased, and SiC is generated by reaction with Si generated by electrolysis to prevent connection and growth of Si particles, thereby playing a role in reducing the granularity of the Si particles.
The invention also has the function that the amount of SiC in the electrolysis product after the amorphous carbon and the cracked carbon are introduced is controllable, namely the amount of SiC in the electrolysis product is adjusted by controlling the amounts of the amorphous carbon and the cracked carbon; the carbon coating of the in-situ cracking on the graphite surface also plays a role in increasing the roughness of the graphite surface and enhancing the combination of the graphite and the silicon dioxide.
In order to realize the purpose, the invention adopts the following technical scheme:
SiO for fused salt electrolysis2A Gc/C (silica-graphite additive/amorphous carbon) composite electrode, which is formed by compounding raw materials including silica, a graphite additive and amorphous carbon, wherein the graphite additive is graphite with a surface coated with cracked carbon, and the amorphous carbon is dispersed between the silica and the graphite additive.
SiO in the invention2The cracked carbon in the Gc/C composite electrode is coated on the surface of graphite, the surface of the graphite is rough, the combination of the graphite and silicon dioxide is enhanced, meanwhile, a certain amount of amorphous carbon is added, so that the electrode reaction active points are increased, and SiC generated by the reaction of the amorphous carbon and the Si generated by electrolysis is prevented from connecting and growing up between Si particles, so that the function of reducing the granularity of the Si particles is achieved. It is also an effect of the present invention that the amount of SiC in the electrolysis product after the amorphous carbon is introduced is controllable, i.e. the amount of SiC in the electrolysis product is adjusted by controlling the amount of amorphous carbon.
Preferably, in the composite electrode, the mass% of silica is 30 to 70%, for example, 33%, 36%, 40%, 45%, 50%, 55%, 60%, 64%, 69%, etc., the mass% of graphite is 30 to 70%, for example, 33%, 36%, 40%, 45%, 50%, 55%, 60%, 64%, 69%, etc., the mass% of amorphous carbon is 0 to 5%, for example, 0.5%, 1, 1.5%, 2.6%, 3%, 3.5%, 4%, 4.5%, etc., and the mass% of amorphous carbon is 0, the cracked carbon coated on the surface of graphite reacts with Si to form SiC.
Preferably, in the composite electrode, the sum of the mole numbers of the cracked carbon and the amorphous carbon and SiO2R is 0<r<1 is, for example, 0.05, 0.1, 0.15, 0.2, 0.3, 0.45, 0.6, 0.8, 0.9, etc.
Preferably, the purity of the silicon dioxide is more than or equal to 99%. The particle size of the silica is preferably 30. + -.10 nm, more preferably 30. + -.5 nm.
Preferably, the silica is at least one of a silica produced by a vapor phase process or a coprecipitation process.
Preferably, the graphite is at least one of natural graphite, artificial graphite, or conductive graphite.
Preferably, the precursor of the cracking carbon is at least one of polyvinyl alcohol, furfuryl alcohol, xylose, styrene-butadiene rubber latex, carboxymethyl cellulose, polymethacrylate, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, phenolic resin, phenol resin, epoxy resin, glucose, sucrose, fructose, cellulose, starch and asphalt.
Preferably, the amorphous carbon is at least one of organic pyrolysis carbon, charcoal, coke, bone char, sugar char, and carbon black.
It is another object of the present invention to provide a SiO for molten salt electrolysis2The preparation method of the-Gc/C composite electrode at least comprises the following steps:
(1) dissolving a cracking carbon precursor in a solvent, adding graphite, uniformly mixing, drying to obtain graphite with the surface coated with the cracking carbon precursor, and carbonizing to obtain graphite with the surface coated with the cracking carbon;
(2) adding the graphite coated with the cracked carbon on the surface obtained in the step (1) into silicon dioxide, a solvent and amorphous carbon to be mixed to prepare uniform silicon dioxide dispersion liquid to prepare mixed slurry;
(3) drying and crushing the mixed slurry obtained in the step (2) into powder to prepare a formed blank, and treating to obtain SiO2-Gc/C composite porous electrode.
The SiO provided by the invention2The preparation method of the-Gc/C composite electrode is simple in process and easy for industrial production.
Preferably, the solvent for the cracked carbon precursor in step (1) is at least one of water, gasoline, alcohols, ketones, and esters.
Preferably, the mass ratio of the cracking carbon precursor to the solvent is 0.01-0.30: 1.
Preferably, the mass ratio of the graphite to the cracked carbon precursor is 1: 0.01-0.1.
Preferably, the carbonization is performed under an inert atmosphere. The inert atmosphere may be provided by at least one of the common inert gases helium, neon, argon, krypton, xenon, and the like. The temperature and time for carbonization can be set according to the precursor used.
Preferably, in the step (2), the solvent is at least one of water, gasoline, alcohols, ketones or esters.
The preparation of the silica dispersion is carried out under stirring, preferably under stirring at 30 to 100rmp, more preferably at 50rpm, in order to obtain a dispersion which is more effective. Meanwhile, when the dispersion liquid is prepared, a proper dispersing agent can be selectively added according to specific situations so as to facilitate dispersion.
Preferably, the powder forming method in step (3) is die pressing or die filling forming, isostatic pressing forming or hot pressing forming.
Preferably, the pressure of the mould pressing or mould filling forming is 0.5-100 MPa, and the pressure maintaining time is 1-20 min.
Preferably, the pressure of the isostatic pressing is 100-200 MPa, and the pressure maintaining time is 1-20 min.
Performing high-temperature treatment after mould pressing or mould filling forming and isostatic pressing forming, such as treatment at 800-1300 ℃ to obtain the final SiO2-Gc/C composite porous electrode.
Preferably, the hot-press forming temperature is 800-1300 ℃, the pressure is 5-100 MPa, and the pressure maintaining time is 15-300 min. The hot-press forming integrates blank forming and high-temperature treatment.
The slurry may be dried at a temperature of 100 ℃ and 150 ℃, more preferably 120 ℃ for 6 hours or more, preferably 12 to 48 hours, most preferably 24 hours.
The particle size of the crushed powder is less than or equal to 1 mm.
Preferably, the preparation method of the invention comprises the following steps:
(1) dissolving a cracking carbon precursor in a solvent, wherein the mass ratio of the cracking carbon precursor to the solvent is 0.01-0.30: 1, adding graphite into a solution in which the carbon precursor is dissolved, preparing a uniform graphite dispersion liquid, and drying to obtain graphite with the surface coated with the cracking carbon precursor;
(2) placing graphite with the surface coated with the cracking carbon precursor in a crucible and carbonizing;
(3) mixing silicon dioxide and a dispersing agent in a mass ratio of 0.10-0.40: 1 to prepare uniform silicon dioxide dispersion liquid, and then adding a certain amount of amorphous carbon to continue stirring uniformly;
(4) weighing a certain amount of the graphite coated with the cracked carbon and prepared in the step (2) according to the mass percent of the graphite additive in the electrode being 30% < G < 70%, adding the graphite into the silicon dioxide and amorphous carbon dispersion liquid, and uniformly mixing to prepare mixed slurry;
(5) drying the mixed slurry at 80-120 ℃ for 12-48 hours, then crushing the mixed slurry into powder with the granularity of less than or equal to 1mm, and preparing the powder into a formed blank.
One of the objects of the present invention is to provide a novel Si/SiC/G (graphite) composite material obtained by electrolysis of the composite electrode of the present invention, which can be used for preparing a battery positive electrode material and has excellent charge and discharge capacity and cycle performance.
The electrolysis can be carried out by the electrolysis method in the prior art. The present invention may use the following electrolysis method: compounding the composite electrode and a conductive cathode current collector to serve as a cathode, using a graphite rod as an anode, and melting CaCl2Is an electrolyte, and is electrolyzed in an inert environment. And cleaning the product after electrolysis, and drying in vacuum.
Electrolysis is preferably carried out in an argon atmosphere. The temperature of the electrolyte is 800-1000 ℃, preferably 900 ℃, and the electrolysis time is more than 4 hours, preferably 6 hours.
The invention has the advantages that:
the surface of the carbon-coated graphite by cracking in the silicon dioxide-graphite additive/amorphous carbon composite electrode, especially the surface of the carbon-coated graphite by in-situ cracking can increase the roughness of the graphite surface and enhance the combination of the graphite and the silicon dioxide; meanwhile, carbon generated by in-situ cracking is uniformly dispersed on the surface of graphite, so that the size of silicon particles is more favorably limited. The battery anode material prepared by the composite electrode material has excellent charge-discharge capacity and cycle performance.
The preparation method of the silicon dioxide-graphite additive/amorphous carbon composite porous electrode adopts conventional industrial equipment, has a wide selection range, and is simple and easy to implement; the used raw materials are large-scale industrial products, so that the cost is low; in the method, the carbon precursor and graphite are mixed by a wet method and are uniformly mixed, and the cracked carbon is generated in situ on the surface of the graphite to enhance the combination of the graphite and the silicon dioxide.
Drawings
FIG. 1 is SiO for example 12SEM image of Gc/C composite electrode magnified 10000 times;
FIG. 2 is an SEM photograph of an electrolytic product Si-SiC-G composite material of example 1 at magnification of 20000 times;
FIG. 3 is a graph showing the cycle profile of the electrolytic product in example 1;
FIG. 4 is SiO for example 22-SEM image of Gc/C composite electrode magnified 20000 times;
FIG. 5 is SiO for example 32-SEM image of Gc/C composite electrode magnified 20000 times;
FIG. 6 is SiO for example 62SEM image of Gc/C composite electrode magnified 10000 times;
FIG. 7 is an SEM photograph at 10000 times magnification of the Si-G composite material which is the electrolytic product in comparative example 1;
FIG. 8 is a graph showing the cycle of the electrolytic product in comparative example 1.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the purpose of facilitating understanding of the present invention and should not be construed as specifically limiting the present invention.
Example 1 SiO for molten salt electrolysis2The preparation method of the-Gc/C composite electrode comprises the following steps:
(1) dissolving a cracking carbon precursor phenolic resin with a mass ratio of 0.05:1 in a solvent, adding graphite into a solution in which a cracking carbon precursor is dissolved, placing the solution in a planetary mixer, mixing to prepare a uniform graphite dispersion liquid, and drying to obtain graphite with the surface coated with the cracking carbon precursor;
(2) placing the graphite coated with the cracking carbon precursor in a crucible, and carbonizing at 700 ℃ to obtain graphite coated with cracking carbon;
(3) mixing the components in a mass ratio of 0.40:1 (nanometer silicon dioxide prepared by a gas phase method, the grain diameter is 30 +/-5 nm, the purity is more than or equal to 99.5 percent) and deionized water are placed in a planetary mixer to be mixed to prepare uniform silicon dioxide dispersion liquid, the rotating speed of a rotation stirring paddle and a revolution stirring paddle of the planetary mixer is 50rpm, and then the molar ratio of the nanometer silicon dioxide to the amorphous carbon is 3: 1 adding amorphous carbon and continuously stirring uniformly;
(4) according to the proportion that the silicon dioxide and graphite additive is 50: weighing a certain mass of graphite with the surface coated with the pyrolytic carbon according to a mass ratio of 50, and placing the graphite in a planetary mixer to mix to prepare uniform mixed slurry;
(5) drying the mixed slurry at 120 ℃ for 24 hours, then crushing the mixed slurry into powder with the granularity less than or equal to 1mm, and carrying out hot press molding on the obtained powder to form SiO2and-Gc/C composite electrode, wherein the forming pressure is 100MPa, the hot pressing temperature is 1200 ℃, and the pressure maintaining time is 75 min.
FIG. 1 shows SiO produced in this example2SEM image of Gc/C composite electrode magnified 10000 times. As can be seen from the figure, the resulting SiO2KS6 particles in the microstructure of the-Gc/C composite electrode form a continuous conductive phase, silicon dioxide is sintered to form a network structure, and the silicon dioxide is dispersed on the surface of KS6 coated with the cracked carbon and among the particles.
The electrode prepared in example 1 was electrolyzed to obtain a novel nano Si/SiC/G composite material, as shown in SEM picture 2, which was mixed with 80%: 10%: 10%, (by weight) conductive agent (S-p) and binder (PVDF), NMP was added, the mixture was placed in a positive slurry, and then coated on a copper foil current collector, the thickness of the obtained coating was 90 μm, the sheet was rolled to 65 μm, the sheet was used as a cathode, Li was used as an anode, Celgard 2400 membrane was selected as a membrane, and LiPF was used as an electrolyte6Base electrolyte (1mol/L LiPF6-EC/DMC/EMC, 1:1:1 (vol%)). The cells were assembled in a glove box and an open circuit voltage of 2.88V was measured.
The prepared battery is tested for charge and discharge performance at room temperature, the limiting voltage is 0.005V-2.0V, the current density is 80mA/g (0.1C), the first discharge capacity of the battery is 712.3mAh/g, the first efficiency is 83.36%, the capacity retention rate after 15 cycles is 87% (the cycle curve chart is shown in figure 3), and the charge and discharge capacity and the cycle performance are both obviously superior to those of the comparative example 1.
Example 2
SiO for fused salt electrolysis2The preparation method of the-Gc/C composite electrode comprises the following steps:
(1) dissolving a cracking carbon precursor phenolic resin with a mass ratio of 0.05:1 in a solvent, adding graphite into a solution in which a cracking carbon precursor is dissolved, placing the solution in a planetary mixer, mixing to prepare a uniform graphite dispersion liquid, and drying to obtain graphite with the surface coated with the cracking carbon precursor;
(2) placing the graphite coated with the cracking carbon precursor in a crucible, and carbonizing at 700 ℃ to obtain graphite coated with cracking carbon;
(3) mixing the components in a mass ratio of 0.40:1 (the particle size of nano silicon dioxide prepared by a vapor phase method is 30 +/-5 nm, the purity is more than or equal to 99.5 percent) and deionized water are placed in a planetary mixer to be mixed to prepare uniform silicon dioxide dispersion liquid, and the rotating speed of a rotation stirring paddle and a revolution stirring paddle of the planetary mixer is 50 rpm; then, according to the mole ratio of the nano silicon dioxide to the amorphous carbon of 3: 1 adding amorphous carbon and continuously stirring uniformly;
(4) according to the mass ratio of silicon dioxide to graphite of 55: 45 weighing a certain mass of graphite with the surface coated with the cracking carbon, and placing the graphite in a planetary mixer to be mixed to prepare uniform mixed slurry;
(5) drying the mixed slurry at 120 ℃ for 24 hours, and then crushing the mixed slurry into powder with the granularity less than or equal to 1 mm; hot-pressing the obtained powder to form SiO2and-Gc/C composite electrode, wherein the forming pressure is 100MPa, the hot pressing temperature is 1200 ℃, and the pressure maintaining time is 75 min.
FIG. 4 shows SiO produced in this example2SEM image of-Gc/C composite electrode magnified 20000 times. As can be seen from the figure, the resulting SiO2KS6 particles in the microstructure of the-Gc/C composite electrode form a continuous conductive phase, silicon dioxide is sintered to be porous, and the silicon dioxide is dispersed on the surface of KS6 coated with the cracked carbon and among the particles.
Example 3
SiO for fused salt electrolysis2The preparation method of the-Gc/C composite electrode comprises the following steps:
(1) dissolving a cracking carbon precursor phenolic resin with a mass ratio of 0.05:1 in a solvent, adding graphite into a solution in which a cracking carbon precursor is dissolved, placing the solution in a planetary mixer, mixing to prepare a uniform graphite dispersion liquid, and drying to obtain graphite with the surface coated with the cracking carbon precursor;
(2) placing the graphite with the surface coated with the carbon precursor in a crucible, and carbonizing at 700 ℃ to obtain graphite with the surface coated with the cracking carbon;
(3) mixing the components in a mass ratio of 0.40:1 (the particle diameter of the nano-silicon dioxide prepared by a gas phase method is 30 +/-5 nm, the purity is more than or equal to 99.5 percent) and deionized water are put into a planetary mixer to be mixed to prepare uniform silicon dioxide dispersion liquid, and the rotating speed of a rotation stirring paddle and a revolution stirring paddle of the planetary mixer is 50 rpm. Then, according to the molar ratio of the nano silicon dioxide to the amorphous carbon of 5:1 adding amorphous carbon and continuously stirring uniformly;
(4) according to the mass ratio of silicon dioxide to graphite of 50: 50 weighing a certain mass of graphite with the surface coated with the cracking carbon, placing the graphite in a planetary mixer, and mixing to prepare uniform mixed slurry;
(5) drying the mixed slurry at 120 deg.C for 24 hr, and pulverizing into powder with particle size of 1mm or lessA body; hot-pressing the obtained powder to form SiO2and-Gc/C composite electrode, wherein the forming pressure is 100MPa, the hot pressing temperature is 1200 ℃, and the pressure maintaining time is 75 min.
FIG. 5 shows SiO produced in this example2SEM image of-Gc/C composite electrode magnified 20000 times. As can be seen from the figure, the resulting SiO2KS6 particles in the microstructure of the-Gc/C composite electrode form a continuous conductive phase, silicon dioxide is completely sintered, and the silicon dioxide is dispersed on the surface of the surface-coated cracked carbon KS6 and among the particles.
Example 4
SiO for fused salt electrolysis2The preparation method of the-Gc/C composite electrode comprises the following steps:
(1) dissolving a cracking carbon precursor sucrose with a mass ratio of 0.05:1 in a solvent, adding graphite into a solution in which the cracking carbon precursor is dissolved, placing the solution in a planetary mixer, mixing to prepare a uniform graphite dispersion liquid, and drying to obtain graphite with the surface coated with the cracking carbon precursor;
(2) placing the graphite with the surface coated with the carbon precursor in a crucible, and carbonizing at 700 ℃ to obtain graphite with the surface coated with the cracking carbon;
(3) mixing the components in a mass ratio of 0.40:1 (the particle size of nano silicon dioxide prepared by a vapor phase method is 30 +/-5 nm, the purity is more than or equal to 99.5 percent) and deionized water are placed in a planetary mixer to be mixed to prepare uniform silicon dioxide dispersion liquid, and the rotating speed of a rotation stirring paddle and a revolution stirring paddle of the planetary mixer is 50 rpm; then, according to the mole ratio of the nano silicon dioxide to the amorphous carbon of 3: 1 adding amorphous carbon and continuously stirring uniformly;
(4) according to the mass ratio of silicon dioxide to graphite of 50: 50 weighing a certain mass of graphite coated with amorphous carbon pyrolytic carbon on the surface, placing the graphite in a planetary mixer, and mixing to prepare uniform mixed slurry;
(5) and drying the mixed slurry at 120 ℃ for 24 hours, and then crushing the mixed slurry into powder with the granularity less than or equal to 1 mm. Hot-pressing the obtained powder to form SiO2and-Gc/C composite electrode, wherein the forming pressure is 100MPa, the hot pressing temperature is 1200 ℃, and the pressure maintaining time is 75 min.
SEM picture showsTo obtain SiO2SFG-6 particles in the microstructure of the G/C composite electrode form a continuous conductive phase, silicon dioxide is sintered to form a net structure, and the silicon dioxide is dispersed on the surface of the SFG-6 coated with the pyrolysis carbon and among the particles.
Example 5
SiO for fused salt electrolysis2The preparation method of the-Gc/C composite electrode comprises the following steps:
(1) dissolving a cracking carbon precursor sucrose with a mass ratio of 0.05:1 in a solvent, adding graphite into a solution in which the cracking carbon precursor is dissolved, placing the solution in a planetary mixer, mixing to prepare a uniform graphite dispersion liquid, and drying to obtain graphite with the surface coated with the cracking carbon precursor;
(2) placing the graphite coated with the cracking carbon precursor in a crucible, and carbonizing at 700 ℃ to obtain graphite coated with cracking carbon;
(3) mixing the components in a mass ratio of 0.40:1 (the particle size of nano silicon dioxide prepared by a vapor phase method is 30 +/-5 nm, the purity is more than or equal to 99.5 percent) and deionized water are placed in a planetary mixer to be mixed to prepare uniform silicon dioxide dispersion liquid, and the rotating speed of a rotation stirring paddle and a revolution stirring paddle of the planetary mixer is 50 rpm; then, according to the mole ratio of the nano silicon dioxide to the amorphous carbon of 6: 1 adding amorphous carbon and continuously stirring uniformly;
(4) according to the mass ratio of silicon dioxide to graphite of 50: 50 weighing a certain mass of graphite with the surface coated with the cracking carbon, placing the graphite in a planetary mixer, and mixing to prepare uniform mixed slurry;
(5) drying the mixed slurry at 120 ℃ for 24 hours, and then crushing the mixed slurry into powder with the granularity less than or equal to 1 mm; hot-pressing the obtained powder to form SiO2and-Gc/C composite electrode, wherein the forming pressure is 100MPa, the hot pressing temperature is 1200 ℃, and the pressure maintaining time is 75 min.
SEM image shows the SiO obtained2SFG-6 particles in the microstructure of the-Gc/C composite electrode form a continuous conductive phase, silicon dioxide is sintered to be porous, and the silicon dioxide is dispersed on the surface of the SFG-6 coated with the pyrolysis carbon and among the particles.
Example 6
Fused salt electrolysisBy SiO2The preparation method of the-Gc/C composite electrode comprises the following steps:
(1) dissolving a cracking carbon precursor phenolic resin with a mass ratio of 0.05:1 in a solvent, adding graphite into a solution in which a cracking carbon precursor is dissolved, placing the solution in a planetary mixer, mixing to prepare a uniform graphite dispersion liquid, and drying to obtain graphite with the surface coated with the cracking carbon precursor;
(2) placing the graphite coated with the cracking carbon precursor in a crucible, and carbonizing at 700 ℃ to obtain graphite coated with cracking carbon;
(3) mixing the components in a mass ratio of 0.40:1 (the particle size of nano silicon dioxide prepared by a vapor phase method is 30 +/-5 nm, the purity is more than or equal to 99.5 percent) and deionized water are placed in a planetary mixer to be mixed to prepare uniform silicon dioxide dispersion liquid, and the rotating speed of a rotation stirring paddle and a revolution stirring paddle of the planetary mixer is 50 rpm; then, according to the mole ratio of the nano silicon dioxide to the amorphous carbon of 3: 1 adding amorphous carbon and continuously stirring uniformly;
(4) according to the mass ratio of silicon dioxide to graphite of 50: 50 weighing a certain mass of graphite with the surface coated with the cracking carbon, placing the graphite in a planetary mixer, and mixing to prepare uniform mixed slurry;
(5) drying the mixed slurry at 120 ℃ for 24 hours, and then crushing the mixed slurry into powder with the granularity less than or equal to 1 mm; carbonizing the obtained powder at 700 deg.C under argon atmosphere for 2h to obtain SiO2-Gc-C powder, and compression molding under 100MPa to obtain SiO2And (3) carrying out high-temperature treatment on the-Gc/C composite electrode, wherein the treatment temperature is 1300 ℃, and the pressure maintaining time is 2 hours.
SEM figure 6 shows the SiO obtained2And (3) sintering silicon dioxide in the microstructure of the Gc/C composite electrode, wherein the silicon dioxide is dispersed on the surface of the SFG-6 coated with the cracked carbon and among particles.
Comparative example 1
A preparation method of a composite electrode comprises the following steps:
(1) mixing the components in a mass ratio of 0.40:1 (the particle size of nano silicon dioxide prepared by a vapor phase method is 30 +/-5 nm, the purity is more than or equal to 99.5 percent) and deionized water are placed in a planetary mixer to be mixed to prepare uniform silicon dioxide dispersion liquid, and the rotating speed of a rotation stirring paddle and a revolution stirring paddle of the planetary mixer is 50 rpm;
(2) mixing the components in a mass ratio of 1:1, mixing the silicon dioxide and the graphite conductive agent KS6 in a planetary mixer to prepare uniform mixed slurry;
(3) drying the mixed slurry at 120 ℃ for 24 hours, and then crushing the mixed slurry into powder with the granularity less than or equal to 1 mm; hot-pressing the obtained powder to form SiO2Forming the KS-6 composite electrode at 100MPa, 1200 ℃ and 75min of pressure maintaining time to obtain SiO2-KS-6 composite electrode.
As shown in the SEM photograph, the microstructure of the product of comparative example 1 in which KS6 particles formed a continuous conductive phase, silica was sintered to have a network structure, silica was dispersed among KS6 particles, and SiO was dispersed2Compounding a KS-6 composite electrode and a conductive cathode current collector to serve as a cathode, using a graphite rod as an anode, and using molten CaCl2The electrolyte is electrolyzed for 6h at 900 ℃ in an argon atmosphere, washed and dried in vacuum to obtain an electrolysis product, and an SEM image is shown in FIG. 7.
The electrode prepared by the comparative example is electrolyzed to obtain a novel nano Si/SiC/G composite material, the novel nano Si/SiC/G composite material, a conductive agent (S-p) and a bonding agent (PVDF) are mixed according to the weight ratio of 80 percent to 10 percent, NMP is added, the mixture is placed to prepare anode slurry, the anode slurry is coated on a copper foil current collector, the thickness of the prepared pole piece coating is 90 micrometers, the pole piece is rolled to 65 micrometers, the pole piece is used as a cathode, Li is used as an anode, a Celgard 2400 membrane is selected as a membrane, and an electrolyte is LiPF6Base electrolyte (1mol/L LiPF6-EC/DMC/EMC, 1:1:1 (vol%)). The cells were assembled in a glove box and an open circuit voltage of 2.80V was measured.
The prepared battery is subjected to charge and discharge performance test at room temperature, the limiting voltage is 0.005V-2.0V, the current density is 80mA/g (0.1C), the first discharge capacity of the battery is 700mAh/g, the discharge capacity after 15 cycles is 491mAh/g, the capacity retention rate after 15 cycles is 70%, and the cycle performance curve chart is shown in figure 8.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (10)

1. SiO for fused salt electrolysis2The preparation method of the-Gc/C composite electrode at least comprises the following steps:
(1) dissolving a cracking carbon precursor in a solvent, adding graphite, mixing, drying to obtain graphite with the surface coated with the cracking carbon precursor, and carbonizing to obtain graphite with the surface coated with the cracking carbon;
(2) adding the graphite coated with the cracked carbon in the step (1) into silicon dioxide dispersion liquid prepared by mixing silicon dioxide, a solvent and amorphous carbon to prepare mixed slurry;
(3) drying and crushing the mixed slurry obtained in the step (2) into powder to prepare a formed blank, and treating to obtain SiO2-a Gc/C composite porous electrode; the composite electrode is formed by compounding raw materials including silicon dioxide, a graphite additive and amorphous carbon, wherein the graphite additive is graphite with the surface coated with pyrolysis carbon, and the amorphous carbon is dispersed between the silicon dioxide and the graphite additive.
2. The preparation method according to claim 1, wherein the solvent of the cracked carbon precursor in step (1) is at least one of water, gasoline, alcohols, ketones or esters;
the mass ratio of the cracking carbon precursor to the solvent is 0.01-0.30: 1;
the mass ratio of the graphite to the cracking carbon precursor is 1: 0.01-0.1;
the carbonization is carried out under an inert atmosphere.
3. The method according to claim 1 or 2, wherein the solvent in step (2) is at least one of water, gasoline, alcohols, ketones, or esters.
4. The preparation method according to claim 1, wherein the powder molding method in the step (3) is mold pressing or mold filling molding, isostatic pressing molding or hot press molding;
the pressure of the mould pressing or mould filling forming is 0.5-100 MPa, and the pressure maintaining time is 1-20 min;
the pressure of the isostatic pressing is 100-200 MPa, and the pressure maintaining time is 1-20 min;
the hot-press forming temperature is 800-1300 ℃, the pressure is 5-100 MPa, and the pressure maintaining time is 15-300 min.
5. The production method according to claim 1, wherein in the composite electrode, the mass percentage of silica is 30 to 70%, the mass percentage of graphite additive is 30 to 70%, and the mass percentage of amorphous carbon is 0 to 5%.
6. The production method according to claim 1, wherein in the composite electrode, a ratio r of the sum of the moles of the cracked carbon and amorphous carbon to the moles of SiO2 is 0< r < 1.
7. The preparation method according to claim 1, wherein the purity of the silicon dioxide is more than or equal to 99%;
the silicon dioxide is at least one of silicon dioxide produced by a gas phase method or a coprecipitation method.
8. The production method according to claim 1, wherein the graphite is at least one of natural graphite, artificial graphite, or conductive graphite;
the precursor of the cracking carbon is at least one of polyvinyl alcohol, furfuryl alcohol, xylose, styrene-butadiene rubber latex, carboxymethyl cellulose, polymethacrylate, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, phenolic resin, phenol resin, epoxy resin, glucose, sucrose, fructose, cellulose, starch and asphalt;
the amorphous carbon is at least one of organic matter cracking carbon, charcoal, coke, bone charcoal, sugar charcoal and carbon black.
9. SiO for molten salt electrolysis produced by the production method according to any one of claims 1 to 82-Gc/C composite electrode.
10. A Si/SiC/G composite material obtained by electrolysis of the composite electrode produced by the production method according to any one of claims 1 to 8.
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