CN113410442A - Silicon-based negative electrode material and preparation method thereof, negative plate and secondary battery - Google Patents

Silicon-based negative electrode material and preparation method thereof, negative plate and secondary battery Download PDF

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CN113410442A
CN113410442A CN202110642153.6A CN202110642153A CN113410442A CN 113410442 A CN113410442 A CN 113410442A CN 202110642153 A CN202110642153 A CN 202110642153A CN 113410442 A CN113410442 A CN 113410442A
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silicon
conductor layer
conductor
negative electrode
mixing
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陈功锋
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Evergrande New Energy Technology Shenzhen 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a silicon-based negative electrode material and a preparation method thereof, a negative electrode plate and a secondary battery. The silicon-based cathode material comprises a silicon-based core, an ion conductor layer coated on the surface of the silicon-based core, and an electron conductor layer coated on the surface of the ion conductor layer deviated from the silicon-based core, wherein the electron conductor layer comprises a one-dimensional conductor material and/or a two-dimensional conductor material. In the silicon-based negative electrode material, the ion conductor layer coated on the surface of the silicon-based core has high ion transmission rate, so that the lithium ion plasma de-intercalation rate of the silicon-based core material can be obviously improved; the electronic conductor layer coated on the outer surface comprises one-dimensional and/or two-dimensional conductor materials, so that the electron transmission migration efficiency of the surface of the silicon-based cathode material can be improved, meanwhile, the silicon-based material is wound and coated, the volume expansion effect of the silicon-based material is inhibited, and the capacity density, the cycle performance and the safety performance of the silicon-based cathode material are improved.

Description

Silicon-based negative electrode material and preparation method thereof, negative plate and secondary battery
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a silicon-based negative electrode material and a preparation method thereof, a negative electrode plate and a secondary battery.
Background
In order to deal with the increasingly prominent problems of contradiction between fuel supply and demand and environmental pollution, the development of new energy automobiles is one of effective methods, and the development of new energy automobile industry is the key point of taking a power battery as the heart of the new energy automobiles. With the development of new energy vehicles, the requirements of consumers on new energy vehicles mainly include two aspects of endurance mileage and quick charging, which requires that the power battery has both energy density and quick charging performance. The traditional graphite is used as the negative electrode of the lithium battery, and the energy density of the battery is low due to the lower theoretical specific capacity (about 330 mAh/g); and the graphite cathode is easy to generate 'lithium precipitation', so that potential safety hazards are caused. At present, in order to improve the overall energy density of the battery, a negative electrode doped with a silicon-based material is generally adopted as the negative electrode. The silicon material has the advantages of high specific capacity (4200mA/h), rich earth crust, low de-intercalated lithium potential, no potential safety hazard caused by lithium precipitation and the like, and becomes a research hotspot of people.
The silicon negative electrode material can generate about 300% volume expansion effect in the lithium extraction process, so that silicon particles are broken under the stress action, and the electrochemical activity is lost; and because of the volume effect of the silicon-based material, a stable solid electrolyte interface film cannot be formed, so that the electrolyte is decomposed for many times, and the conductivity of the material is reduced. Meanwhile, the silicon-based material cathode loses electric contact with a current collector due to the volume effect of the silicon cathode material, so that the internal resistance of the battery is increased, and the capacity and the cycle performance are obviously reduced. In addition, the quick charge capacity of the battery cell is mainly developed from two aspects at present, so that the de-intercalation rate of lithium ions is improved on one hand; on the other hand, the conduction rate of electrons is improved. From the property of silicon-based materials, the material has poorer electron transport capability and lithium ion deintercalation rate than graphite. The traditional technical scheme for improving the silicon material mainly improves the electron transmission capability in a carbon coating mode, and has a method for improving the lithium ion transmission rate.
Disclosure of Invention
The invention aims to provide a silicon-based negative electrode material and a preparation method thereof, a negative electrode plate and a secondary battery, and aims to solve the problems of large volume expansion effect and poor electron transmission capability of the conventional silicon-based negative electrode material to a certain extent.
In order to achieve the purpose of the application, the technical scheme adopted by the invention is as follows:
in a first aspect, the present invention provides a silicon-based anode material, where the silicon-based anode material includes a silicon-based core, an ion conductor layer coated on the surface of the silicon-based core, and an electron conductor layer coated on the surface of the ion conductor layer away from the surface of the silicon-based core, and the electron conductor layer includes a one-dimensional conductor material and/or a two-dimensional conductor material.
In the silicon-based negative electrode material provided by the first aspect of the invention, the ion conductor layer is coated on the surface of the silicon-based core, so that the transmission rate of ions in the silicon-based negative electrode material is high, and the lithium ion plasma deintercalation rate of the silicon-based core material can be remarkably improved; the electronic conductor layer coated on the outer surface comprises one-dimensional and/or two-dimensional conductor materials, so that the electron transmission and migration efficiency of the surface of the silicon-based cathode material can be improved, meanwhile, the one-dimensional linear or two-dimensional sheet-shaped conductor materials have a winding and coating effect on the silicon-based material, the volume expansion effect of the silicon-based material in the charging and discharging process can be effectively inhibited, and the capacity density, the cycle performance and the safety performance of the silicon-based cathode material are improved.
Further, the ion conductor layer includes Li3Zr2Si2PO4、Li14Zn(GeO4)4、Li3xLa2/3-xTiO3Wherein x is 0.05 to 0.2; the ion conductor materials have excellent ion transmission and migration performance, and can remarkably improve the embedding and releasing transmission rate of lithium ion plasma in the silicon-based negative electrode material.
Further, the electronic conductor layer comprises at least one of carbon nanotubes, graphene, polypyrrole, polyaniline, polypyridine, polyphenyl, polyphenylene ethylene and polythiophene; the one-dimensional linear and two-dimensional flaky materials not only have excellent conductivity and high electron transfer transmission efficiency, but also can wind and coat the core silicon-based material, thereby relieving the volume expansion effect of the silicon-based material in the charging and discharging processes.
Furthermore, the silicon-based inner core comprises at least one of silicon, silicon carbide, silicon monoxide and silicon oxide, and the silicon-based materials have high specific capacity and low lithium extraction potential, so that the lithium extraction phenomenon can be reduced.
Further, in the silicon-based cathode material, the molar ratio of the ion conductor layer, the electron conductor layer and the silicon-based core is (0.01-0.2): (0.01-0.2): 1, the molar ratio of each functional layer in the silicon-based negative electrode material effectively ensures the ionic conductivity, the electronic conductivity and the specific capacity of the silicon-based negative electrode material.
Furthermore, the silicon-based core material with the granularity D50 of 1-10 nm, small and uniform particle size has better conductivity and better film-forming property, is beneficial to preparing a negative plate with uniform thickness, compact film layer and smooth surface, reduces interface impedance, and improves the stability and safety performance of the battery.
In a second aspect, the present invention provides a method for preparing a silicon-based negative electrode material, comprising the following steps:
preparing mixed precursor slurry of the ionic conductor material;
mixing the mixed precursor slurry with a silicon-based material, drying, and sintering to obtain a first silicon-based material coated with an ion conductor layer;
preparing electronic conductor slurry containing one-dimensional conductor material and/or two-dimensional conductor material, and mixing and drying the electronic conductor slurry and the first silicon-based material to obtain the silicon-based cathode material.
The preparation method of the silicon-based anode material provided by the second aspect of the invention has the advantages of simple process, simple and convenient operation and suitability for industrial large-scale production and application, and the prepared silicon-based anode material with the ion and electron double-layer coating has high specific capacity, high ion and electron conductivity, stability and safety.
Further, the ion conductor layer includes Li3Zr2Si2PO4、Li14Zn(GeO4)4、Li3xLa2/3-xTiO3Wherein x is 0.05 to 0.2; the ion conductor materials have excellent ion transmission and migration performance, and can remarkably improve the embedding and releasing transmission rate of lithium ion plasma in the silicon-based negative electrode material.
Further, the mixed precursor slurry includes Li3Zr2Si2PO4Precursor slurry and Li14Zn(GeO4)4Precursor slurry and Li3xLa2/3-xTiO3At least one of precursor slurries. The mixed precursor slurry can contain precursor slurry of one ion conductor material and also can contain precursor slurry of various ion conductor materials to form a composite ion conductor layer of various ion conductor materials, so that the ion transmission performance of the silicon-based cathode material is better improved.
Further, Li is prepared3Zr2Si2PO4The precursor slurry comprises the following steps: mixing a lithium source, a zirconium source and a first solvent according to the stoichiometric ratio, and then mixing the mixture with phosphoric acid and silicic acid to obtain Li3Zr2Si2PO4The precursor slurry has good dispersion stability and is beneficial to subsequent mixing with silicon-based materials.
Further, Li is prepared14Zn(GeO4)4The precursor slurry comprises the following steps: mixing a lithium source, a zinc source and a second solvent according to the stoichiometric ratio, and then mixing with germanic acid to obtain Li14Zn(GeO4)4The precursor slurry has good dispersion stability and is beneficial to subsequent mixing with silicon-based materials.
Further, Li is prepared3xLa2/3-xTiO3The precursor slurry comprises the following steps: mixing a lithium source, a lanthanum source and a third solvent according to the stoichiometric ratio, and then mixing the mixture with tetrabutyl titanate to obtain Li3xLa2/3-xTiO3The precursor slurry has good dispersion stability and is beneficial to subsequent mixing with silicon-based materials.
Further, the solid-liquid ratio is 1g: (8-20) mL, mixing the mixed precursor slurry with a silicon-based material, drying to remove the solvent, and coating the precursor of the ion conductor on the surface of the silicon-based material to form a coating layer of the precursor of the ion conductor, thereby obtaining the pre-sintered product.
Further, the conditions of the sintering treatment include: sintering for 1-10 hours in an oxygen atmosphere at 500-800 ℃; and sintering in an oxygen-containing atmosphere to oxidize the precursor of the ion conductor to generate an ion conductor material, and coating the ion conductor material on the surface of the silicon-based material in situ to form an ion conductor layer, so that the embedding and extracting efficiency of lithium ion plasma in the silicon-based negative electrode material is improved, and the electrochemical performance of the silicon-based negative electrode material is improved.
Further, the preparation of the electronic conductor paste comprises the steps of: and dispersing the one-dimensional conductor material and/or the two-dimensional conductor material in water to obtain the electronic conductor slurry. The adopted electronic conductor material is in a one-dimensional linear or two-dimensional sheet shape, and can be wound and coated on the surface of the first silicon-based material, so that a coating layer can be formed on the surface of the silicon-based material even if materials such as adhesives are not added into the electronic conductor paste.
Further, the step of mixing and drying treatment comprises the following steps: mixing the electronic conductor slurry with the first silicon-based material, carrying out mixing treatment for 8-15 hours at the temperature of 60-90 ℃, drying for 12-48 hours at the temperature of 90-120 ℃ under a vacuum condition, and forming an electronic conductor layer on the surface of the first silicon-based material to obtain the double-layer coated silicon-based cathode material. The method comprises the steps of mixing the electronic conductor slurry with a first silicon-based material, then mixing the mixture at a low temperature by a sol-gel method to remove most of the solvent in the electronic conductor slurry, and then completely removing the residual solvent by vacuum drying to form a stable electronic conductor coating layer.
Further, in the silicon-based negative electrode material, the molar ratio of the ionic conductor material, the electronic conductor material and the silicon-based material is (0.01-0.2): (0.01-0.2): 1; the molar ratio of each functional layer in the silicon-based negative electrode material effectively ensures the ionic conductivity, the electronic conductivity and the specific capacity of the silicon-based negative electrode material.
Further, in the sintering treatment atmosphere, the oxygen content is 70-80%; the conversion effect of the precursor of the ion conductor can be affected by the oxygen content, if the oxygen content is too low, the conversion of the precursor into the ion conductor is not facilitated, and if the oxygen content is too high, the stability of the silicon-based material can be affected.
Further, the lithium source includes at least one of lithium nitrate, lithium hydroxide, lithium carbonate, and lithium acetate. Further, the zirconium source includes at least one of zirconium nitrate, zirconium oxide, zirconium chloride, and zirconium carbonate. In one step, the zinc source comprises at least one of zinc nitrate, zinc carbonate and zinc acetate. Further, the lanthanum source comprises at least one of lanthanum nitrate and lanthanum chloride. The precursor material of the intermediate ionic conductor has good dissolving and dispersing effects in a solvent, and is beneficial to forming a corresponding ionic conductor material through subsequent sintering.
In a third aspect, the invention provides a negative plate, which contains the silicon-based negative electrode material or the silicon-based negative electrode material prepared by the method.
The negative plate provided by the third aspect of the invention contains the silicon-based negative electrode material with high specific capacity, high ionic and electronic conductivity, stability and safety, so that the negative plate also has high capacity, ionic and electronic conductivity, good cyclic charge and discharge stability and high safety.
In a fourth aspect, the present invention provides a secondary battery, which includes the above negative electrode sheet.
The secondary battery provided by the fourth aspect of the invention has the negative electrode sheet with high capacity, ion and electron conductivity, good cyclic charge and discharge stability and high safety, so that the energy density and the cycle life of the secondary battery are improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed for the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a schematic flow chart of a preparation method of a silicon-based anode material provided by an embodiment of the invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the present invention, the term "and/or" describes the association relationship of the associated objects, and means that there may be three relationships, for example, a and/or B, which may mean: a is present alone, A and B are present simultaneously, and B is present alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.
In the present invention, "at least one" means one or more, "a plurality" means two or more. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, "at least one (one) of a, b, or c," or "at least one (one) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, and c may be single or plural, respectively.
It should be understood that, in various embodiments of the present invention, the sequence numbers of the above-mentioned processes do not mean the execution sequence, some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The weight of the related components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present invention as long as it is in accordance with the description of the embodiments of the present invention. Specifically, the mass in the description of the embodiments of the present invention may be a mass unit known in the chemical industry field such as μ g, mg, g, kg, etc.
The terms "first" and "second" are used for descriptive purposes only and are used for distinguishing purposes such as substances from one another, and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the invention. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.
In a first aspect, an embodiment of the present invention provides a silicon-based anode material, where the silicon-based anode material includes a silicon-based core, an ion conductor layer coated on a surface of the silicon-based core, and an electron conductor layer coated on the ion conductor layer away from the surface of the silicon-based core, and the electron conductor layer includes a one-dimensional conductor material and/or a two-dimensional conductor material.
The silicon-based anode material provided by the first aspect of the embodiment of the invention comprises a silicon-based core, an ion conductor layer and an electronic conductor layer, wherein the ion conductor layer and the electronic conductor layer sequentially coat the surface of the silicon-based core, and the silicon-based anode material with double coatings of an ion conductor and an electronic conductor is formed. The ion conductor layer coated on the surface of the silicon-based core has a high transmission rate of ions in the ion conductor layer, so that the lithium ion plasma de-intercalation rate of the silicon-based core material can be remarkably improved; the electronic conductor layer coated on the outer surface comprises one-dimensional and/or two-dimensional conductor materials, so that the electron transmission and migration efficiency of the surface of the silicon-based cathode material can be improved, meanwhile, the one-dimensional linear or two-dimensional sheet-shaped conductor materials have a winding and coating effect on the silicon-based material, the volume expansion effect of the silicon-based material in the charging and discharging process can be effectively inhibited, and the capacity density, the cycle performance and the safety performance of the silicon-based cathode material are improved.
At one endIn some embodiments, the ion conductor layer includes Li3Zr2Si2PO4、Li14Zn(GeO4)4、Li3xLa2/3-xTiO3Wherein x is 0.05 to 0.2; the ion conductor materials have excellent ion transmission and migration performance, the transmission rate of ions, particularly lithium ions, in the ion conductor materials is extremely high, and the ion conductor layers made of the ion conductor materials coat the silicon-based negative electrode materials, so that the insertion and extraction transmission rate of the lithium ions and the like in the silicon-based negative electrode materials can be remarkably improved. In some embodiments, the ion conductor layer includes Li3Zr2Si2PO4、Li14Zn(GeO4)4、Li0.5La0.5TiO3、Li0.33La0.57TiO3At least one ion conductor material.
In some embodiments, the electron conductor layer includes at least one of carbon nanotubes, graphene, polypyrrole, polyaniline, polypyridine, polyphenyl, polyphenylene ethylene, and polythiophene, wherein the graphene is a two-dimensional sheet-shaped conductive material, and the carbon nanotubes (including multi-wall carbon nanotubes and single-wall carbon nanotubes), polypyrrole, polyaniline, polypyridine, polyphenyl, polyphenylene ethylene, and polythiophene are one-dimensional linear conductive materials. The one-dimensional linear and two-dimensional sheet materials contained in the electronic conductor layer in the embodiment of the application have excellent conductivity and high electron migration transmission efficiency, and the core silicon-based materials can be wound and coated, so that the volume expansion effect of the silicon-based materials in the charging and discharging process is relieved.
In some embodiments, the silicon-based core comprises at least one of silicon, silicon carbide, silica; the silicon-based materials have high specific capacity and low lithium-releasing and-inserting potential, and the phenomenon of lithium precipitation can be reduced.
In some embodiments, in the silicon-based anode material, the molar ratio of the ion conductor layer, the electron conductor layer and the silicon-based core is (0.01-0.2): (0.01-0.2): 1. if the molar ratio of the ion conductor layer is too low, namely the coating layer is too thin, the improvement effect on ion embedding and extraction in the silicon-based negative electrode material is not obvious; if the molar ratio of the ion conductor layer is too high, that is, the coating layer is too thick, the migration path of lithium ion plasma is increased, the internal resistance of the material is increased, the migration and transmission effects of ions are reduced, and the rapid transmission effect cannot be achieved. If the molar ratio of the electronic conductor layer is too low, namely the electronic conductor layer is coated too thin, the improvement on the electron transfer transmission performance of the surface of the silicon-based cathode material is not obvious, and the inhibition effect on the volume expansion effect of the silicon-based material in the charging and discharging processes is not good; if the molar ratio of the electron conductor layer is too high, i.e., the electron conductor layer is too thick, the internal resistance of the material increases, the ion transmission path increases, and the migration and transmission efficiency of lithium ions and other ions is hindered.
In some embodiments, the silicon-based core material with the particle size D50 of 1-10 nm, small and uniform particle size has better conductivity and better film-forming property, is beneficial to preparing a negative plate with uniform thickness, compact film layer and smooth surface, reduces interface impedance, and improves the stability and safety performance of a battery. If the particle size D50 of the silicon-based core is too large, the conductivity of the material is reduced, and the volume expansion effect during charging and discharging is increased correspondingly. In some embodiments, the silicon-based core has a particle size D50 of 1-3 nm, 3-5 nm, 5-8 nm, 8-10 nm, etc.
The silicon-based negative electrode material of the embodiment of the application can be prepared by the following method of the embodiment.
As shown in fig. 1, a second aspect of the embodiments of the present invention provides a method for preparing a silicon-based negative electrode material, including the following steps:
s10, preparing mixed precursor slurry of the ionic conductor material;
s20, mixing the mixed precursor slurry with a silicon-based material, drying, and sintering to obtain a first silicon-based material coated with an ion conductor layer;
s30, preparing electronic conductor slurry containing a one-dimensional conductor material and/or a two-dimensional conductor material, and mixing and drying the electronic conductor slurry and the first silicon-based material to obtain the silicon-based cathode material.
In the method for preparing a silicon-based negative electrode material according to the second aspect of the embodiments of the present invention, after preparing the mixed precursor slurry of the ion conductor material, the mixed precursor slurry is mixed with the silicon-based material, so that the silicon-based negative electrode material is uniformly dispersed in the mixed precursor slurry of the ion conductor, the mixed precursor is uniformly coated on the surface of the silicon-based material after drying, and then the precursor is converted into the ion conductor by sintering treatment, and an ion conductor coating layer is generated in situ on the surface of the silicon-based material, so as to obtain the first silicon-based material. And then, preparing slurry of the electronic conductor material, mixing the slurry with the first silicon-based material to uniformly disperse the first silicon-based material in the electronic conductor slurry, and then drying to volatilize and remove the solvent in the slurry, so that the one-dimensional linear and two-dimensional sheet conductor material is wound and coated on the surface of the first silicon-based material to form an electronic conductor layer, and the silicon-based cathode material with the ion and electron double-layer coating is obtained. The preparation method of the silicon-based anode material provided by the embodiment of the invention has the advantages of simple process and simplicity and convenience in operation, and is suitable for industrial large-scale production and application.
In some embodiments, in the step S10, the ion conductor material includes Li3Zr2Si2PO4、Li14Zn(GeO4)4、Li3xLa2/3-xTiO3Wherein x is 0.05-0.2; the ion conductor materials have excellent ion transmission and migration performance, the transmission rate of ions, particularly lithium ions, in the ion conductor materials is extremely high, and the ion conductor layers made of the ion conductor materials coat the silicon-based negative electrode materials, so that the insertion and extraction transmission rate of the lithium ions and the like in the silicon-based negative electrode materials can be remarkably improved. In some embodiments, the ion conductor layer includes Li3Zr2Si2PO4、Li14Zn(GeO4)4、Li0.5La0.5TiO3、Li0.33La0.57TiO3At least one ion conductor material.
In some embodiments, the mixed precursor slurry comprises Li3Zr2Si2PO4Precursor slurry and Li14Zn(GeO4)4Precursor slurry and Li3xLa2/3-xTiO3At least one of precursor slurries. The mixed precursor slurry of the embodiment of the invention can contain a precursor slurry of an ion conductor material to form a coating layer of a single ion conductor; the composite ion conductor layer can also contain precursor slurry of various ion conductor materials to form a composite ion conductor layer of various ion conductor materials, so that the ion transmission performance of the silicon-based cathode material is better improved.
In some embodiments, Li is prepared3Zr2Si2PO4The precursor slurry comprises the following steps: mixing a lithium source, a zirconium source and a first solvent according to the stoichiometric ratio, and then mixing the mixture with phosphoric acid and silicic acid to obtain Li3Zr2Si2PO4And (3) precursor slurry. In some embodiments, the first solvent may be an organic solvent such as absolute ethanol, which has a good dissolution effect on the lithium source and the zirconium source and a low boiling point. In some embodiments, after dispersing the lithium source and the zirconium source in absolute ethyl alcohol according to the stoichiometric ratio to form a mixed solution, slowly adding phosphoric acid and silicic acid, and fully and uniformly mixing to obtain Li3Zr2Si2PO4And (3) precursor slurry.
In some embodiments, Li is prepared14Zn(GeO4)4The precursor slurry comprises the following steps: mixing a lithium source, a zinc source and a second solvent according to the stoichiometric ratio, and then mixing with germanic acid to obtain Li14Zn(GeO4)4And (3) precursor slurry. In some embodiments, the second solvent may be an organic solvent such as absolute ethyl alcohol, which has a good dissolution effect on the lithium source and the zinc source and a low boiling point. In some embodiments, according to the stoichiometric ratio, after dispersing the lithium source and the zinc source in absolute ethyl alcohol to form a mixed solution, slowly adding germanic acid, and fully and uniformly mixing to obtain Li14Zn(GeO4)4And (3) precursor slurry.
In some embodiments, Li is prepared3xLa2/3-xTiO3The precursor slurry comprises the following steps: mixing a lithium source, a lanthanum source and a third solvent according to the stoichiometric ratio, and then mixing the mixture with tetrabutyl titanate to obtain Li3xLa2/3-xTiO3And (3) precursor slurry. In some embodiments, the third solvent may be an organic solvent having a good dissolution effect on the lithium source and the lanthanum source, and a low boiling point, such as absolute ethyl alcohol. In some embodiments, after dispersing the lithium source and the lanthanum source in absolute ethyl alcohol according to the stoichiometric ratio to form a mixed solution, slowly adding tetrabutyl titanate and fully and uniformly mixing to obtain Li3xLa2/3-xTiO3And (3) precursor slurry.
In some embodiments, the lithium source comprises at least one of lithium nitrate, lithium hydroxide, lithium carbonate, lithium acetate.
In some embodiments, the zirconium source comprises at least one of zirconium nitrate, zirconium oxide, zirconium chloride, zirconium carbonate.
In some embodiments, the zinc source comprises at least one of zinc nitrate, zinc carbonate, zinc acetate.
In some embodiments, the lanthanum source comprises at least one of lanthanum nitrate, lanthanum chloride.
The precursor material of the ion conductor in the embodiment of the invention has good dissolving and dispersing effects in the solvent, and is beneficial to forming the corresponding ion conductor material through subsequent sintering.
In some embodiments, in the step S20, the ratio of solid to liquid is 1g: (8-20) mL, mixing the mixed precursor slurry with a silicon-based material, drying to remove the solvent, and coating the precursor of the ion conductor on the surface of the silicon-based material to form a coating layer of the precursor of the ion conductor, thereby obtaining the pre-sintered product. In the embodiment of the invention, the solid-liquid ratio of the mixture of the mixed precursor slurry and the silicon-based material affects the evaporation rate of the solvent and the coating effect of the slurry, if the solid-liquid ratio is too small, namely the liquid content is too high, the subsequent drying time for removing the solvent is long, and the uniform coating of the mixed precursor slurry on the surface of the silicon-based material is not facilitated; if the solid-to-liquid ratio is too large, that is, the liquid content is too low, the silicon-based material is not favorably dispersed in the mixed precursor slurry, and the ion conductor precursor is also influenced to be uniformly coated on the surface of the silicon-based material. In some embodiments, in the slurry after mixing the mixed precursor slurry with the silicon-based material, the solid-to-liquid ratio may be 1g: (8-10) mL, 1g: (10-13) mL, 1g: (13-15) mL, 1g: (15-18) mL, 1g: (18-20) mL, etc.
In some embodiments, in the step S20, the sintering process conditions include: sintering for 1-10 hours in an oxygen atmosphere at 500-800 ℃. According to the embodiment of the invention, the pre-sintered material is sintered in an oxygen-containing atmosphere, so that the ion conductor precursor is oxidized to generate the ion conductor material, and the ion conductor layer is formed by in-situ coating on the surface of the silicon-based material, thereby improving the intercalation and deintercalation efficiency of lithium ion plasma in the silicon-based negative electrode material and improving the electrochemical performance of the silicon-based negative electrode material. In addition, if the sintering temperature is too high or the sintering time is too long, the instability of the ion conductor layer is affected; if the sintering temperature is too low or the sintering time is too short, the precursor of the ion conductor is not favorably converted into the ion conductor, and the formation of the ion conductor layer is influenced.
In some embodiments, the oxygen content in the sintering treatment atmosphere is 70-80%; the conversion effect of the precursor of the ion conductor can be affected by the oxygen content, if the oxygen content is too low, the conversion of the precursor into the ion conductor is not facilitated, and if the oxygen content is too high, the stability of the silicon-based material can be affected.
In some embodiments, the silicon-based core comprises at least one of silicon, silicon carbide, silica; the silicon-based materials have high specific capacity and low lithium-releasing and-inserting potential, and the phenomenon of lithium precipitation can be reduced.
In some embodiments, the silicon-based core material with the particle size D50 of 1-10 nm, small and uniform particle size has better conductivity and better film-forming property, is beneficial to preparing a negative plate with uniform thickness, compact film layer and smooth surface, reduces interface impedance, and improves the stability and safety performance of a battery. If the particle size D50 of the silicon-based core is too large, the conductivity of the material is reduced, and the volume expansion effect during charging and discharging is increased correspondingly. In some embodiments, the silicon-based core has a particle size D50 of 1-3 nm, 3-5 nm, 5-8 nm, 8-10 nm, etc.
In some embodiments, in step S30, the preparing of the electronic conductor paste includes the steps of: and dispersing the one-dimensional conductor material and/or the two-dimensional conductor material in water to obtain the electronic conductor slurry. In the embodiment of the invention, the adopted electronic conductor material is in a one-dimensional linear or two-dimensional sheet shape, and can be wound and coated on the surface of the first silicon-based material, so that a coating layer can be formed on the surface of the silicon-based material even if materials such as an adhesive and the like are not added into the electronic conductor paste.
In some embodiments, the electron conductor material comprises at least one of carbon nanotubes, graphene, polypyrrole, polyaniline, polypyridine, polyphenyl, polyphenylene vinylene, polythiophene; the one-dimensional linear and two-dimensional flaky materials not only have excellent conductivity and high electron transfer transmission efficiency, but also can wind and coat the core silicon-based material, thereby relieving the volume expansion effect of the silicon-based material in the charging and discharging processes.
In some embodiments, the step of hybrid drying process comprises: mixing the electronic conductor slurry with the first silicon-based material, carrying out mixing treatment for 8-15 hours at the temperature of 60-90 ℃, drying for 12-48 hours at the temperature of 90-120 ℃ under a vacuum condition, and forming an electronic conductor layer on the surface of the first silicon-based material to obtain the double-layer coated silicon-based cathode material. According to the embodiment of the invention, after the electronic conductor slurry and the first silicon-based material are mixed, the mixture is mixed at a low temperature through a sol-gel method, most of solvent in the electronic conductor slurry is removed, and then the residual solvent is completely removed through vacuum drying to form a stable electronic conductor coating layer, so that the silicon-based negative electrode material with the ion and electronic double-layer coating layer is obtained.
In some embodiments, the molar ratio of the ionic conductor material, the electronic conductor material and the silicon-based material in the silicon-based anode material is (0.01-0.2): (0.01-0.2): 1. if the molar ratio of the ion conductor layer is too low, namely the coating layer is too thin, the improvement effect on ion embedding and extraction in the silicon-based negative electrode material is not obvious; if the molar ratio of the ion conductor layer is too high, that is, the coating layer is too thick, the migration path of lithium ion plasma is increased, the internal resistance of the material is increased, the migration and transmission effects of ions are reduced, and the rapid transmission effect cannot be achieved. If the molar ratio of the electronic conductor layer is too low, namely the electronic conductor layer is coated too thin, the improvement on the electron transfer transmission performance of the surface of the silicon-based cathode material is not obvious, and the inhibition effect on the volume expansion effect of the silicon-based material in the charging and discharging processes is not good; if the molar ratio of the electron conductor layer is too high, i.e., the electron conductor layer is too thick, the internal resistance of the material increases, the ion transmission path increases, and the migration and transmission efficiency of lithium ions and other ions is hindered.
In a third aspect of the embodiments of the present invention, a negative electrode plate is provided, where the negative electrode plate includes the above silicon-based negative electrode material, or includes the silicon-based negative electrode material prepared by the above method.
The negative electrode plate provided by the third aspect of the embodiment of the invention contains the silicon-based negative electrode material with high specific capacity, high ionic and electronic conductivity, stability and safety, so that the negative electrode plate also has high capacity, ionic and electronic conductivity, good cyclic charge and discharge stability and high safety.
The negative plate in the embodiment of the invention can also contain materials such as a binder and a conductive agent, so that the conductivity of the negative plate is further improved, and the combination stability of the negative plate and a current collector is improved. In some embodiments, after a silicon-based negative electrode material, a binder, a conductive agent, a solvent and other materials are mixed to prepare a stable negative electrode slurry, the stable negative electrode slurry is deposited on a negative current collector by a coating or other methods to form a negative electrode sheet with a compact film layer, uniform thickness and a smooth surface. The embodiment of the invention does not specifically limit the materials such as the binder, the conductive agent, the solvent and the like in the negative plate, can select proper materials according to the actual application condition, is flexible in application and has wide adaptability.
A fourth aspect of the embodiments of the present invention provides a secondary battery including the above negative electrode sheet.
The secondary battery provided by the fourth aspect of the embodiment of the invention includes the negative electrode sheet having the above-mentioned high capacity, ionic and electronic conductivity, good cyclic charge and discharge stability and high safety, so that the energy density and cycle life of the secondary battery are improved.
The embodiment of the invention does not specifically limit the positive plate, the diaphragm, the electrode liquid and the like in the secondary battery, can select proper materials according to the actual application condition, has flexible application and wide adaptability.
In order to make the details and operations of the above embodiments of the present invention clearly understood by those skilled in the art, and to make the advanced performances of the silicon-based negative electrode material, the preparation method thereof, the negative electrode sheet and the secondary battery of the embodiments of the present invention obviously manifest, the above technical solutions are illustrated by a plurality of examples below.
Example 1
A silicon-based anode material is prepared by the following steps:
weighing 0.1mol of zirconium nitrate and 0.15mol of lithium nitrate according to a molar ratio, and uniformly dispersing in absolute ethyl alcohol to form a uniformly mixed solution A. Then slowly adding 0.05mol of phosphoric acid and 0.1mol of silicic acid, continuously dispersing uniformly, adding 1mol of SiO material in batches, adjusting the solid-liquid ratio to be 1g:10mL, stirring and evaporating at 75 ℃ for 5h, and vacuum drying at 100 ℃ for 24h to obtain a pre-sintered substance. Ball-milling the obtained pre-sintered substance for 2h to obtain pre-sintered powder, and sintering at 550 ℃ for 24h in 70% oxygen atmosphere to obtain the final product SiO.0.05 mol (coating amount) Li3Zr2Si2PO4I.e. the first silicon-based material coated with the ion conductor layer, wherein the molar ratio of the silicon-based material to the ion conductor material is 1: 0.05.
② adding the first silicon-based material into the water solution containing 0.05mol of linear conductive substance SWCNT, mixing uniformly, adopting sol-gel method, stirring the solution at 80 ℃ for 10h until the water is completely evaporated, then vacuum drying at 100 ℃ for 24h to form an electronic conductor layer, finally obtaining SiO.0.05 mol of Li3Zr2Si2PO40.05mol of SWCNT material, i.e., SiO negative electrode material with double coating of fast ion conductor/linear conductive material, wherein the molar ratio of silicon-based material to ion conductor material, electron conductor material is 1:0.05: 0.05.
Example 2
A silicon-based anode material is prepared by the following steps:
weighing 0.02mol of zirconium nitrate and 0.03mol of lithium nitrate according to a molar ratio, and uniformly dispersing in absolute ethyl alcohol to form a uniformly mixed solution A. Then slowly adding 0.01mol of phosphoric acid and 0.02mol of silicic acid, continuously dispersing uniformly, adding 1mol of SiO material in batches, adjusting the solid-liquid ratio to be 1g:10mL, stirring and evaporating at 75 ℃ for 5h, and vacuum drying at 100 ℃ for 24h to obtain a pre-sintered substance. Ball-milling the obtained pre-sintered substance for 2h to obtain pre-sintered powder, and sintering at 550 ℃ for 24h in 70% oxygen atmosphere to obtain the final product SiO.0.01 mol Li3Zr2Si2PO4I.e. the first silicon-based material coated with an ion conductor layer.
② adding the first silicon-based material into the water solution containing 0.01mol of linear conductive substance SWCNT, mixing uniformly, adopting sol-gel method, stirring the solution at 80 ℃ for 10h until the water is completely evaporated, then vacuum drying at 100 ℃ for 24h to form an electronic conductor layer, finally obtaining SiO.0.01 mol of Li3Zr2Si2PO40.01mol of SWCNT material, i.e. SiO negative electrode material with double coating of fast ion conductor/linear conductive substance; wherein, the molar ratio of the silicon-based material to the ionic conductor material to the electronic conductor material is 1:0.01: 0.01.
Example 3
A silicon-based anode material is prepared by the following steps:
weighing 0.1mol of zirconium nitrate and 0.15mol of lithium nitrate according to a molar ratio, and uniformly dispersing in absolute ethyl alcohol to form a uniformly mixed solution A. Then slowly adding 0.05mol of phosphoric acid and 0.1mol of silicic acid, continuously dispersing uniformly, adding 1mol of SiO material in batches, adjusting the solid-liquid ratio to be 1g:10mL, stirring and evaporating at 75 ℃ for 5h, and vacuum drying at 100 ℃ for 24h to obtain a pre-sintered substance. Ball-milling the obtained pre-sintered substance for 2h to obtain pre-sintered powder, and sintering at 550 ℃ for 24h in 70% oxygen atmosphere to obtain the final product SiO.0.05 mol Li3Zr2Si2PO4I.e. the first silicon-based material coated with an ion conductor layer.
② the first silicon baseAdding the materials into an aqueous solution containing 0.05mol of CNT (carbon nano tube) of a linear conductive substance, uniformly mixing, stirring the solution at 80 ℃ for 10h by adopting a sol-gel method until water is completely evaporated, and then carrying out vacuum drying at 100 ℃ for 24h to form an electronic conductor layer, thereby finally obtaining SiO & 0.05mol of Li3Zr2Si2PO40.05mol of CNT material, i.e. SiO negative electrode material with double coating of fast ion conductor/linear conductive substance; wherein the molar ratio of the silicon-based material to the ionic conductor material to the electronic conductor material is 1:0.05: 0.05.
Example 4
A silicon-based anode material is prepared by the following steps:
weighing 0.1mol of zirconium nitrate and 0.15mol of lithium nitrate according to a molar ratio, and uniformly dispersing in absolute ethyl alcohol to form a uniformly mixed solution A. Then slowly adding 0.05mol of phosphoric acid and 0.1mol of silicic acid, continuously dispersing uniformly, adding 1mol of SiO material in batches, adjusting the solid-liquid ratio to be 1g:10mL, stirring and evaporating at 75 ℃ for 5h, and vacuum drying at 100 ℃ for 24h to obtain a pre-sintered substance. Ball-milling the obtained pre-sintered substance for 2h to obtain pre-sintered powder, and sintering at 550 ℃ for 24h in 70% oxygen atmosphere to obtain the final product SiO.0.05 mol Li3Zr2Si2PO4I.e. the first silicon-based material coated with an ion conductor layer.
② adding the first silicon-based material into the aqueous solution containing 0.05mol of polypyrrole as a linear conductive substance, mixing uniformly, stirring the solution at 80 ℃ for 10h by adopting a sol-gel method until the water is completely evaporated, then drying in vacuum at 100 ℃ for 24h to form an electronic conductor layer, and finally obtaining 0.05mol of SiO Li3Zr2Si2PO40.05mol of polypyrrole material, i.e. SiO negative electrode material with double coating of fast ion conductor/linear conductive substance; wherein the molar ratio of the silicon-based material to the ionic conductor material to the electronic conductor material is 1:0.05: 0.05.
Example 5
A silicon-based anode material is prepared by the following steps:
weighing 0.05mol of zinc nitrate and 0.7mol of lithium nitrate according to the molar ratioUniformly dispersing in absolute ethyl alcohol to form a uniform mixed solution A, slowly adding 0.2mol of germanic acid, continuously dispersing uniformly, adding 1mol of SiO material in batches, adjusting the solid-to-liquid ratio to be 1g:10mL, stirring and evaporating at 75 ℃ for 5h, and vacuum drying at 100 ℃ for 24h to obtain a presintered substance. Ball-milling the obtained pre-sintered substance for 2h to obtain pre-sintered powder, and sintering at 550 ℃ for 24h in 70% oxygen atmosphere to obtain the final product SiO.0.05 mol Li14Zn(GeO4)4I.e. the first silicon-based material coated with an ion conductor layer.
② adding the first silicon-based material into the water solution containing 0.05mol of linear conductive substance SWCNT, mixing uniformly, adopting sol-gel method, stirring the solution at 80 ℃ for 10h until the water is completely evaporated, then vacuum drying at 100 ℃ for 24h to form an electronic conductor layer, finally obtaining SiO.0.05 mol of Li14Zn(GeO4)40.05mol of SWCNT material, i.e. SiO negative electrode material with double coating of fast ion conductor/linear conductive substance; wherein the molar ratio of the silicon-based material to the ionic conductor material to the electronic conductor material is 1:0.05: 0.05.
Example 6
A silicon-based anode material is prepared by the following steps:
weighing 0.0285mol of lanthanum nitrate and 0.0165mol of lithium nitrate according to a molar ratio, uniformly dispersing the lanthanum nitrate and the lithium nitrate in absolute ethyl alcohol to form a uniformly mixed solution A, slowly adding 0.05mol of tetrabutyl titanate, continuously dispersing the uniformly, adding 1mol of SiO material in batches, adjusting the solid-liquid ratio to be 1g:10mL, stirring and evaporating at 75 ℃ for 5 hours, and performing vacuum drying at 100 ℃ for 24 hours to obtain a presintered substance. Ball-milling the obtained pre-sintered substance for 2h to obtain pre-sintered powder, and sintering at 550 ℃ for 24h in 70% oxygen atmosphere to obtain the final product SiO.0.05 mol Li0.33La0.57TiO3I.e. the first silicon-based material coated with an ion conductor layer.
② adding the first silicon-based material into the water solution containing 0.05mol of linear conductive substance SWCNT, mixing uniformly, adopting sol-gel method, stirring the solution at 80 ℃ for 10h until the water is completely evaporated, then vacuum drying at 100 ℃ for 24h to form the electronic conductorA bulk layer, finally obtaining SiO 0.05mol Li0.33La0.57TiO30.05mol of SWCNT material, i.e. SiO negative electrode material with double coating of fast ion conductor/linear conductive substance; wherein the molar ratio of the silicon-based material to the ionic conductor material to the electronic conductor material is 1:0.05: 0.05.
Example 7
A silicon-based anode material, which differs from example 1 in that:
in the step I, the addition amount of the SiO material is 0.5mol, and the final product SiO.0.1 mol Li is obtained3Zr2Si2PO4I.e. the first silicon-based material coated with an ion conductor layer.
In the second step, the addition amount of SWCNT is 0.1mol to obtain SiO 0.1mol Li3Zr2Si2PO40.1mol of SWCNT material, i.e., SiO negative electrode material with double coating of fast ion conductor/linear conductive material, wherein the molar ratio of silicon-based material to ion conductor material, electron conductor material is 1:0.1: 0.1.
Example 8
A silicon-based anode material, which differs from example 1 in that:
in the step I, the addition amount of the SiO material is 0.25mol, and the final product SiO.0.2 mol Li is obtained3Zr2Si2PO4I.e. the first silicon-based material coated with an ion conductor layer.
In the second step, the addition amount of SWCNT is 0.2mol, and SiO 0.2mol Li is obtained3Zr2Si2PO40.2mol of SWCNT material, i.e., SiO negative electrode material with double coating of fast ion conductor/linear conductive material, wherein the molar ratio of silicon-based material to ion conductor material, electron conductor material is 1:0.2: 0.2.
Example 9
A silicon-based anode material, which differs from example 1 in that:
in the step I, the addition amount of the SiO material is 0.2mol, and the final product SiO.0.25 mol Li is obtained3Zr2Si2PO4I.e. the first coated with ion conductor layerA silicon-based material.
In the second step, the amount of SWCNT added is 0.25mol, and SiO.0.25 mol of Li is obtained3Zr2Si2PO40.25mol of SWCNT material, i.e., SiO negative electrode material with double coating of fast ion conductor/linear conductive material, wherein the molar ratio of silicon-based material to ion conductor material, electron conductor material is 1:0.25: 0.25.
Comparative example 1
A silicon-based negative electrode material without any treatment and without any coating of SiO material, the same as the raw material used in the above examples.
Comparative example 2
A silicon-based anode material is prepared by the following steps:
in terms of molar ratio, 0.1mol of zirconium nitrate and 0.15mol of lithium nitrate are weighed and uniformly dispersed in absolute ethyl alcohol to form a uniformly mixed solution A. Then slowly adding 0.05mol of phosphoric acid and 0.1mol of silicic acid, continuously dispersing uniformly, adding 1mol of SiO material in batches, adjusting the solid-liquid ratio to be 1g:10mL, stirring and evaporating at 75 ℃ for 5h, and vacuum drying at 100 ℃ for 24h to obtain a pre-sintered substance. Ball-milling the obtained pre-sintered substance for 2h to obtain pre-sintered powder, and sintering at 550 ℃ for 24h in an oxygen atmosphere to obtain the final product SiO.0.05 mol Li3Zr2Si2PO4Namely a silicon-based cathode material coated with an ion conductor layer.
Comparative example 3
A silicon-based anode material is prepared by the following steps:
adding SiO material into aqueous solution containing 0.05mol of SWCNT (single-walled carbon nanotube) linear conductive substance, uniformly mixing, stirring the solution at 80 ℃ for 10h by adopting a sol-gel method until water is completely evaporated, and then drying in vacuum at 100 ℃ for 24h to finally obtain SiO.0.05 mol of SWCNT material, namely the SiO negative electrode material coated with the linear conductive substance.
Further, in order to verify the advancement of the examples of the present invention, the following performance tests were performed on the silicon-based anode materials prepared in examples 1 to 8 and comparative examples 1 to 3 according to the present invention:
manufacturing negativePole piece: silicon-based negative electrode materials prepared in examples 1 to 8 and comparative examples 1 to 3 were used as negative electrode active materials, with PAA binder, SWCNT conductive agent and H2O, according to main materials: PAA: SWCNT: and mixing the water with the ratio of 95.9:4.0:0.1:100 to form slurry, and respectively coating the slurry on a negative current collector to prepare a negative plate.
Manufacturing a soft package battery: the negative plate prepared by the silicon-based negative electrode material of each example and comparative example, the positive plate made of Ni88 material, the 12+4 ceramic diaphragm and the high-nickel electrolyte are assembled into a soft package battery, the designed battery capacity is 9Ah, and the battery size is 80 × 60 × 8.55 mm.
The soft package batteries manufactured by the silicon-based negative electrode materials of the examples and the comparative examples are subjected to direct current impedance DCR, quick charge performance and cycle performance tests, and the test results are shown in the following table 1:
TABLE 1
Figure BDA0003107467650000191
It can be seen from the above test results that, compared with the pure SiO material of comparative example 1, the silicon-based negative electrode material of comparative example 2 only covering the ion conductor material layer, and the silicon-based negative electrode material of comparative example 3 only covering the electron conductor layer, the soft-package battery prepared by using the silicon-based negative electrode material with double covering in embodiments 1 to 9 of the present invention can increase the Li + de-intercalation rate and the electron transmission rate, reduce the DCR and temperature rise of the battery cell, and achieve higher fast charge performance and cycle performance, wherein the optimum examples include a reduction of 53.79% in the DCR of the battery cell, an increase of 15.14% in the constant current ratio of 2C fast charge, and an increase of 63% in the cycle performance of the battery cell.
As can be seen from the comparison between examples 1 to 8 and 9, when the coating amounts of the ion conductor layer and the electron conductor layer in the silicon-based negative electrode material are too high (example 9), the internal resistance of the battery is increased, which is not favorable for improving the quick charge performance and the cycle performance of the battery.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. The silicon-based anode material is characterized by comprising a silicon-based core, an ion conductor layer coated on the surface of the silicon-based core, and an electronic conductor layer coated on the surface of the ion conductor layer deviated from the silicon-based core, wherein the electronic conductor layer comprises a one-dimensional conductor material and/or a two-dimensional conductor material.
2. The silicon-based anode material of claim 1, wherein the ion conductor layer comprises Li3Zr2Si2PO4、Li14Zn(GeO4)4、Li3xLa2/3-xTiO3Wherein x is 0.05 to 0.2;
and/or the electronic conductor layer comprises at least one of carbon nano tubes, graphene, polypyrrole, polyaniline, polypyridine, polyphenyl, polyphenylene ethylene and polythiophene;
and/or the silicon-based inner core comprises at least one of silicon, silicon carbide, silicon monoxide and silicon oxide.
3. The silicon-based anode material according to claim 1 or 2, wherein the molar ratio of the ion conductor layer, the electron conductor layer and the silicon-based core in the silicon-based anode material is (0.01-0.2): (0.01-0.2): 1;
and/or the particle size D50 of the silicon-based inner core is 1-10 nm.
4. The preparation method of the silicon-based negative electrode material is characterized by comprising the following steps of:
preparing mixed precursor slurry of the ionic conductor material;
mixing the mixed precursor slurry with a silicon-based material, drying, and sintering to obtain a first silicon-based material coated with an ion conductor layer;
preparing electronic conductor paste containing one-dimensional conductor materials and/or two-dimensional conductor materials, and mixing and drying the electronic conductor paste and the first silicon-based material to obtain the silicon-based cathode material.
5. The method of claim 4, wherein the ion conductor material comprises Li3Zr2Si2PO4、Li14Zn(GeO4)4、Li3xLa2/3-xTiO3Wherein x is 0.05-0.2;
and/or the mixed precursor slurry comprises Li3Zr2Si2PO4Precursor slurry and Li14Zn(GeO4)4Precursor slurry and Li3xLa2/3-xTiO3At least one of precursor slurries.
6. The method of preparing a silicon-based anode material according to claim 5, wherein the Li is prepared3Zr2Si2PO4The precursor slurry comprises the following steps: mixing a lithium source, a zirconium source and a first solvent according to the stoichiometric ratio, and then mixing the mixture with phosphoric acid and silicic acid to obtain the Li3Zr2Si2PO4Precursor slurry;
and/or, preparation of said Li14Zn(GeO4)4The precursor slurry comprises the following steps: mixing a lithium source, a zinc source and a second solvent according to the stoichiometric ratio, and then mixing with germanic acid to obtain Li14Zn(GeO4)4Precursor slurry;
and/or, preparation of said Li3xLa2/3-xTiO3The precursor slurry comprises the following steps: mixing a lithium source, a lanthanum source and a third solvent according to the stoichiometric ratio, and then mixing the mixture with tetrabutyl titanate to obtain Li3xLa2/3-xTiO3And (3) precursor slurry.
7. The method for preparing a silicon-based anode material according to claim 6, wherein the ratio of solid to liquid is 1g: (8-20) mL, mixing the mixed precursor slurry with the silicon-based material, and drying to remove the solvent to obtain a pre-sintered object;
and/or the conditions of the sintering treatment comprise: sintering for 1-10 hours in an oxygen atmosphere at 500-800 ℃;
and/or the preparation of the electronic conductor paste comprises the following steps: dispersing the one-dimensional conductor material and/or the two-dimensional conductor material in water to obtain the electronic conductor slurry;
and/or the step of the hybrid drying treatment comprises the following steps: and mixing the electronic conductor slurry with the first silicon-based material, carrying out mixing treatment for 8-15 hours at the temperature of 60-90 ℃, drying for 12-48 hours at the temperature of 90-120 ℃ under a vacuum condition, and forming an electronic conductor layer on the surface of the first silicon-based material to obtain the double-layer coated silicon-based cathode material.
8. The method for preparing the silicon-based anode material according to claim 7, wherein the molar ratio of the ionic conductor material, the electronic conductor material and the silicon-based material in the silicon-based anode material is (0.01-0.2): (0.01-0.2): 1;
and/or in the sintering treatment atmosphere, the oxygen content is 70-80%;
and/or the lithium source comprises at least one of lithium nitrate, lithium hydroxide, lithium carbonate and lithium acetate;
and/or the zirconium source comprises at least one of zirconium nitrate, zirconium oxide, zirconium chloride and zirconium carbonate;
and/or the zinc source comprises at least one of zinc nitrate, zinc carbonate and zinc acetate;
and/or the lanthanum source comprises at least one of lanthanum nitrate and lanthanum chloride.
9. A negative plate, characterized in that the negative plate comprises the silicon-based negative electrode material according to any one of claims 1 to 3 or the silicon-based negative electrode material prepared by the method according to any one of claims 4 to 8.
10. A secondary battery comprising the negative electrode sheet according to claim 9.
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CN110931792A (en) * 2019-11-13 2020-03-27 天津巴莫科技有限责任公司 Coated silicon-based material and preparation method thereof
CN114142011A (en) * 2021-11-29 2022-03-04 蜂巢能源科技有限公司 Hard carbon composite material and preparation method and application thereof
CN114613960A (en) * 2022-03-15 2022-06-10 内蒙古杉杉新材料有限公司 Composite coated silicon-based material, preparation method and application thereof, and lithium ion battery
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