WO2019161648A1 - Matériau composite et son procédé de préparation - Google Patents

Matériau composite et son procédé de préparation Download PDF

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Publication number
WO2019161648A1
WO2019161648A1 PCT/CN2018/102343 CN2018102343W WO2019161648A1 WO 2019161648 A1 WO2019161648 A1 WO 2019161648A1 CN 2018102343 W CN2018102343 W CN 2018102343W WO 2019161648 A1 WO2019161648 A1 WO 2019161648A1
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silicon
layer
graphene
based material
layered
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PCT/CN2018/102343
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English (en)
Chinese (zh)
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苏航
李阳兴
于哲勋
王平华
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华为技术有限公司
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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

Definitions

  • the present application relates to the field of material technology, and in particular, to a composite material and a preparation method thereof.
  • Lithium-ion batteries usually use graphite as the anode material.
  • the theoretical gram capacity of graphite is 372 mAh/g, and the current gram capacity of graphite has exceeded 360 mAh/g, which is close to the theoretical limit value. It is difficult to have any room for further increase. A further increase in the energy density of the battery.
  • the theoretical gram capacity of silicon is much larger than that of graphite, reaching 4200 mAh/g, and it is promising to be used as a battery anode material.
  • the silicon-based anode material is continuously converted in the state of full lithium insertion and de-lithium, and the volume of the silicon-based anode material is increased in the state of full lithium insertion relative to the delithiation state. From about 300% to 400%, frequent and severe volume changes cause the silicon-based negative electrode material to be susceptible to cracking and chalking, reducing battery life.
  • the present application provides a composite material and a preparation method thereof for solving the problem that the silicon negative electrode material in the battery existing in the prior art is easily broken and pulverized.
  • the present application provides a composite material comprising: a layered silicon core and a plurality of graphene layers, wherein the layered silicon core comprises at least two layers of silicon-based material, the layer of silicon-based material comprising silicon or An oxide of silicon, such as silicon monoxide.
  • the layered silicon core comprises at least two layers of silicon-based material, the layer of silicon-based material comprising silicon or An oxide of silicon, such as silicon monoxide.
  • the size of the interlayer voids may be different at different positions of two adjacent silicon-based material layers, and different adjacent two layers of interlayer voids The size can also be different.
  • a graphene layer is located in an interlayer gap of two adjacent ones of the silicon-based material layers, and one or two silicon-based material layers of each of the graphene layer and two adjacent ones of the silicon-based material layers There is a gap between them.
  • the interlayer of the two adjacent silicon-based materials of the composite material has interlayer voids, which can suppress the expansion pressure of the composite material during lithium insertion, and reduce the probability of the composite material being broken or pulverized due to large volume change. .
  • the interlayer voids of the adjacent two silicon-based material layers are also filled with a graphene layer, and the graphene layer can be longitudinally supported by the layered silicon core to improve the strength of the layered silicon core and prevent the layered silicon core from being repeated. Structural collapse occurs after expansion and contraction.
  • graphene also has excellent electrical conductivity, contributes to electron transport, and can improve the electrical conductivity of the composite.
  • a graphene coating layer covering the outer surface of the layered silicon core layer is further included, the graphene coating layer can further improve the electrical conductivity of the composite material, and the graphene coating layer can also have good flexibility.
  • the composite material has a good buffering effect on the expansion of the battery during charging and discharging, and inhibits the cracking and pulverization of the composite material.
  • the graphene layer is coupled to one or both of the two silicon-based material layers adjacent thereto to enhance the structural strength of the layered silicon core and the layer of the silicon-based material layer Conductive performance.
  • adjacent layers of two silicon-based materials are joined to enhance the structural strength of the layered silicon core and the interlayer conductivity of the layer of silicon-based material.
  • the composite material further includes a cladding layer covering the layered silicon core, the cladding layer coating the layered silicon core inside, the cladding layer may be a carbon coating layer An inorganic compound coating layer or an organic coating layer.
  • the coating layer can reduce the direct contact between the layered silicon core and the electrolyte, and slow down the battery capacity attenuation.
  • the cladding layer is a carbon coating layer, it can also provide a highly efficient conductive interface and improve the power performance of the battery.
  • the interlaminar gap between two adjacent silicon-based material layers 111 of the layered silicon core 110 is between 10 nanometers (nm) and 10 micrometers ( ⁇ m) in the delithiated state.
  • the interlayer gap between two adjacent silicon-based material layers 111 may be 10 nm, 40 nm, 120 nm, 660 nm, 1 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, or the like.
  • the inter-layer voids of the above size allow the layered silicon core 110 to have a small volume change when switching between the detached state and the lithium-intercalated state, reducing the probability of cracking and pulverization of the composite.
  • the present application provides a method for preparing a composite material, comprising: reacting a metal silicide with a metal remover to obtain a layered silicon core, which may be a finished product or a metal and a silicon base.
  • the material is prepared by reaction, and the metal removing agent may be ethanol, propanol, butanol, isopropanol, CuCl2, SnCl2, HCl, etc.
  • the layered silicon core obtained includes at least two layers of silicon-based materials, two adjacent There are inter-layer spaces between the silicon-based material layers, and the silicon-based material layer includes an oxide of silicon or silicon.
  • a plurality of graphene layers are prepared on the layered silicon core, the graphene layer is located in the interlayer gap of two adjacent silicon-based material layers, and the graphene layer is adjacent to the two There is a gap between one or two layers of silicon-based material in the layer of silicon-based material.
  • the graphene layer may be one or more layers of graphene, and different graphene layers may have different thicknesses.
  • the composite material prepared by the above method has interlayer voids between adjacent two silicon-based material layers, and the interlayer voids can suppress the expansion pressure of the composite material during lithium insertion, and reduce the composite material to be broken due to large volume change or The chance of chalking.
  • the interlayer voids of the adjacent two silicon-based material layers are also filled with a graphene layer, and the graphene layer can be longitudinally supported by the layered silicon core to improve the strength of the layered silicon core and prevent the layered silicon core from being repeated. Structural collapse occurs after expansion and contraction.
  • graphene also has excellent electrical conductivity, contributes to electron transport, and can improve the electrical conductivity of the composite.
  • a graphene cap layer is further prepared on the outer surface of the layered silicon core, the graphene cap layer can further improve the electrical conductivity of the composite material, and the graphene cover layer has good flexibility. It can well buffer the expansion of the composite during the charging and discharging process of the battery, and inhibit the cracking and pulverization of the composite.
  • the method further includes: preparing a cladding layer on an outer surface of the layered silicon core layer formed with the plurality of graphene layers, the cladding layer coating the layered silicon core in the Inside the coating.
  • the cladding layer encapsulates the layered silicon core within the cladding layer.
  • the coating layer may be an amorphous carbon coating layer, or may be an inorganic compound coating layer such as a lithium titanate coating layer, or may be an organic coating layer such as a polyaniline coating layer.
  • the preparation process of the coating layer may be evaporation, sputtering, electroplating, chemical vapor deposition (CVD) or the like.
  • the coating layer can reduce the direct contact between the layered silicon core and the electrolyte, and slow down the battery capacity attenuation. Moreover, when the cladding layer is a carbon coating layer, it can also provide a highly efficient conductive interface and improve the power performance of the battery.
  • the method further includes: preparing a cladding layer on an outer surface of the layered silicon core layer formed with the graphene coating layer, the cladding layer coating the layered silicon core in the package Inside the cladding.
  • the cladding layer encapsulates the layered silicon core within the cladding layer.
  • the coating layer may be an amorphous carbon coating layer, or may be an inorganic compound coating layer such as a lithium titanate coating layer, or may be an organic coating layer such as a polyaniline coating layer.
  • the preparation process of the cladding layer may be evaporation, sputtering, electroplating, CVD, or the like.
  • the coating layer can reduce the direct contact between the layered silicon core and the electrolyte, and slow down the battery capacity attenuation. Moreover, when the cladding layer is a carbon coating layer, it can also provide an efficient conductive interface and improve the power performance of the battery.
  • a graphene layer is grown in the inter-layer voids of the layered silicon core using a chemical vapor deposition CVD process.
  • the method of preparing a silicon-based material having pores is relatively low in cost and high in efficiency.
  • the prepared graphene or graphene finished product migrates to the interlaminar voids of the layered silicon core.
  • the method of preparing a silicon-based material having pores is relatively low in cost and high in efficiency.
  • the metal in the metal silicide includes an alkali metal or an alkaline earth metal.
  • the present application provides a battery comprising: a positive electrode, an electrolyte, and a negative electrode; and the electrode material of the positive electrode may be a lithium-containing compound, such as lithium manganate, lithium iron phosphate, lithium nickel cobalt manganese oxide, etc.
  • the electrolyte may be: Ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, phosphorus pentafluoride, hydrofluoric acid, and the like.
  • the present application provides a method for improving a negative electrode material of a lithium ion battery, the method comprising: using a layered silicon core as a main body of a silicon negative electrode material, wherein the layered silicon core comprises a plurality of silicon-based material layers, adjacent to two There is an interlayer gap between the layers of the silicon-based material, and the silicon-based material layer includes an oxide of silicon or silicon.
  • the interlayer gap between two adjacent layers of the layered silicon core can alleviate the expansion pressure of the silicon anode material in the lithium intercalation state, because the silicon-based material layer can expand to the interlayer gap after intercalating lithium, thereby reducing the entire
  • the volume change of the layered silicon core reduces the probability of cracking and chalking of the composite.
  • a plurality of graphene layers are further disposed inside the layered silicon core, each of the graphene layers being located in an interlayer gap of two adjacent ones of the silicon-based material layers, and each of the graphites
  • the olefin layer has a void between at least one of the two of the silicon-based material layers.
  • the graphene layer in the interlaminar voids of the layered silicon core has strong strength and can provide stable interlayer support to the composite.
  • the graphene layer in the interlaminar void of the layered silicon core can also enhance the interlayer electron conduction of the silicon-based material layer 111, enhance the electrical conductivity of the composite material, and thereby improve the performance of the battery.
  • FIG. 1 is a schematic structural view of a composite material provided by an embodiment of the present application.
  • FIGS. 2a-2d are schematic views of a graphene layer in an embodiment of the present application.
  • FIG. 3 is a schematic view of the composite material in a delithiated state and a lithium intercalation state
  • Figure 4 is a schematic view of a graphene cover layer
  • 5a-5b are schematic views of a cladding layer of a composite material
  • Figure 6 is a schematic view of interlayer voids between adjacent silicon-based material layers
  • FIG. 7 is a schematic flow chart of a method of preparing a composite material
  • Figure 8 is a schematic view showing a process of forming a layered silicon core
  • FIG. 9 is a schematic structural diagram of a battery provided by an embodiment of the present application.
  • the plurality referred to in the present application means two or more.
  • the term “and/or” in the present application is merely an association relationship describing an associated object, indicating that there may be three relationships, for example, A and/or B, which may indicate that A exists separately, and A and B exist simultaneously. There are three cases of B alone.
  • Graphene is a two-dimensional crystal with a thickness of one atom formed by a carbon (C) atom arranged neatly in a hexagonal lattice. Graphene not only has excellent mechanical properties, but also has strong strength and excellent electrical conductivity.
  • Chemical vapor deposition refers to introducing a vapor containing a gaseous reactant or a liquid reactant constituting an element of a target substance and other gases required for the reaction into a reaction chamber, and chemically reacting on the surface of the substrate to form a thin film. The process of particles.
  • Solid electrolyte interface (SEI) membrane During the first charge and discharge of a liquid lithium ion battery, the material of the electrode reacts with the electrolyte at the solid-liquid phase interface to form a passivation layer covering the surface of the electrode.
  • the passivation film can effectively prevent the passage of solvent molecules, but lithium ions can be freely embedded and removed through the passivation layer, and have the characteristics of a solid electrolyte. Therefore, this passivation film is called a solid electrolyte interface film.
  • the composite 100 includes a layered silicon core 110 and a plurality of graphene layers 120.
  • the left side of FIG. 1 is the structure of the layered silicon core 110, and the layered silicon core 110 includes a plurality of silicon-based material layers 111 with interlayer voids between adjacent two silicon-based material layers 111.
  • the silicon-based material layer 111 may be a silicon (Si) layer or an oxide layer of silicon, such as a silicon oxide (SiO) layer.
  • the silicon-based material layer 111 may further include silicon dioxide, but not all of silicon dioxide to improve lithium intercalation capability.
  • the thickness thereof may be the thickness of one or more atomic layers
  • the silicon-based material layer 111 is an oxide layer of silicon
  • the thickness may be the thickness of one or more molecular layers.
  • the thickness of the different silicon-based material layers 111 may be the same or different.
  • the graphene layer 120 is located in the interlayer gap of two adjacent silicon-based material layers of the layered silicon core.
  • the graphene layer may have a thickness of one layer or two or more layers.
  • the thickness of one graphene layer between adjacent two silicon-based material layers may be non-uniform.
  • the graphene layer 120 has a larger thickness at the A position, and the graphene at the A position. It may be connected to the upper and lower silicon-based material layers 111, and the thickness of the B-site of the graphene layer 120 is small, and the graphene at the B-position may be connected to only one silicon-based material layer 111.
  • the thickness of the graphene layer between different silicon-based material layers may be the same or different.
  • the graphene layer 120-a is located in the silicon-based material layers 111-a, 111-b.
  • the graphene layer 120-b is located between the silicon-based material layers 111-b, 111-c
  • the graphene layer 120-c is located between the silicon-based material layers 111-c, 111-d, and the graphene layer 120-a
  • the thickness is equal to the thickness of the graphene layer 120-c and greater than the thickness of the graphene layer 120-b.
  • the graphene layer 120 occupies a portion of the inter-layer voids of the layered silicon core 110, but does not fill the entire inter-layer voids, and there are still layers between the adjacent two silicon-based material layers of the layered silicon core 110.
  • the inter-space, that is, each of the graphene layer 120 has a gap between at least one of the two adjacent silicon-based material layers 111.
  • the layered silicon core 110 when the layered silicon core 110 is in the lithium intercalation state, lithium ions are intercalated into the silicon-based material layer 111, the volume of the silicon-based material layer 111 becomes large, and the interlayer gap between the silicon-based material layers 111 becomes small.
  • the reduced inter-layer voids of the layered silicon core 110 can reduce the overall outward extent of the layered silicon core 110. Therefore, the layered silicon core 110 structure can reduce the volume change of the composite material 100 during the delithiation state-lithium state transition, and reduce the probability of composite cracking and pulverization.
  • the graphene layer 120 in the interlaminar spaces of the layered silicon core 110 has a strong strength and can provide the composite material 100 with stable interlayer support.
  • the graphene layer 120 in the interlaminar spaces of the layered silicon core 110 can also enhance the interlayer electron conduction of the silicon-based material layer 111, enhance the electrical conductivity of the composite material 100, and thereby improve the performance of the battery.
  • the composite further includes a graphene cap layer 121 overlying the outer surface of the layered silicon core 110. It should be understood that the graphene cap layer 121 may cover a local portion of the outer surface of the layered silicon core 110 or may completely cover the outer surface of the layered silicon core 110.
  • the outer surface of the layered silicon core 110 is covered with the graphene cover layer 121, which can further improve the conductivity of the layered silicon core 110, and the good flexibility of the graphene cover layer 121 can also be applied to the layered silicon core.
  • the expansion of the battery during charging and discharging of the battery serves as a good buffering effect, inhibiting cracking and chalking of the composite material 100.
  • direct contact of the layered silicon core with the electrolyte results in a continuous generation of a new SEI film between the silicon and the electrolyte, resulting in exhaustion of the electrolyte, rapid decay of the battery capacity, and coverage of the graphene on the outer surface of the layered silicon core 110.
  • the cover layer 121 can reduce the direct contact of the layered silicon core with the electrolyte and slow down the battery capacity attenuation.
  • a portion of the adjacent two silicon-based material layers 111 may be connected to enhance the structural strength of the layered silicon core 110 and the interlayer conductivity of the silicon-based material layer 111. It should be noted that, in order to better embody the interlaminar voids of the layered silicon core 110, in the schematic views of FIGS. 1 to 4 and the following, the adjacent two silicon-based material layers 111 are simplified to phase separation.
  • the graphene layer 120 may be connected to one or two of the adjacent upper and lower silicon-based material layers to enhance the layered silicon core 110. Structural strength and interlayer conductivity of the silicon-based material layer 111.
  • the composite material 100 further includes a cladding layer 130 covering the layered silicon core 110, the cladding layer 130 encasing the layered silicon core 110.
  • the outer surface of the layered silicon core 110 is covered with a cladding layer 130 without covering the graphene cover layer 121; and in FIG. 5b, the outer surface of the layered silicon core 110 is first covered with a graphene cover layer 121, and then On the graphene cover layer 121, the cladding layer 130 is further coated.
  • the coating layer 130 may be an amorphous carbon coating layer, or may be an inorganic compound coating layer, such as a lithium titanate coating layer, or may be an organic coating layer, such as a polyaniline coating layer.
  • the cross-sectional shape of the cladding layer in FIGS. 5 a to 5 b is simplified to a circular shape.
  • the cross-sectional shape of the cladding layer may be other shapes such as an elliptical shape, or may be an irregular shape.
  • the coating layer 130 is prepared on the outer surface of the layered silicon core 110, which can reduce the direct contact between the layered silicon core and the electrolyte, and slow down the battery capacity attenuation. Moreover, when the cladding layer 130 is a carbon coating layer. It also provides an efficient conductive interface to enhance the power performance of the battery.
  • the interlaminar gap between adjacent two silicon-based material layers 111 of the layered silicon core 110 is in the range of 10 nanometers (nm) to 10 micrometers ( ⁇ m) in the delithiated state.
  • the interlayer gap between two adjacent silicon-based material layers 111 may be 10 nm, 40 nm, 120 nm, 660 nm, 1 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, or the like.
  • the inter-layer voids of the above size allow the layered silicon core 110 to have a small volume change when switching between the detached state and the lithium-intercalated state, reducing the probability of cracking and pulverization of the composite.
  • the size of the interlayer gap between two adjacent layers may be different at different positions, as shown in FIG. 6, the interlayer gap between the adjacent silicon-based material layer 111-e and the silicon-based material layer 111-f.
  • the size is not a fixed value, with a minimum inter-layer gap (Cmin) at position C and a maximum inter-layer gap (Cmax) at position D.
  • the embodiment of the present application provides a method for preparing a composite material. Referring to FIG. 7, the method includes:
  • Step 21 The metal silicide is reacted with a metal remover to obtain a layered silicon core.
  • the layered silicon core comprises at least two layers of silicon-based material with inter-layer voids between adjacent two layers of at least two layers of silicon-based material.
  • the silicon-based material includes at least one of silicon or silicon oxide.
  • the silicon-based material may be any one of silicon and silicon monoxide, or the silicon-based material includes silicon, silicon dioxide, and silicon oxide. Two of them, or both.
  • the above metal silicide may be a finished product or may be formed according to a reaction between a metal and silicon (or an oxide of silicon).
  • Methods of preparing metal silicides include, but are not limited to, sintering, evaporation, sputtering, electroplating, CVD, and the like.
  • the metal element in the metal silicide may be an alkali metal or an alkaline earth metal such as Li, Na, Ca, Mg or the like.
  • the metal silicide is prepared using only one metal, for example, by mixing silica with magnesium (Mg) to form Mg2Si.
  • metal silicides may be prepared using two or more metals, for example, Li3NaSi6 formed from lithium, sodium, and silicon.
  • the metal remover is used for demetallization reaction with the metal silicide, and the metal remover may be different depending on the type of the metal silicide.
  • the metal remover is a chemical delithiation reagent including, but not limited to, ethanol, propanol, butanol, isopropanol, and the like.
  • the metal silicide is calcium silicide (CaSi2)
  • the metal remover may be an oxidizing agent or an acid solution including, but not limited to, CuCl2, SnCl2, HCl, and the like.
  • the metal silicide and the metal remover react in different reaction media to obtain silicon-based materials in different oxidation states.
  • the reaction medium is an alcohol
  • the calcium silicide reacts with the metal remover to obtain silica.
  • the other oxide of the outer silicon is represented by SiOx; when the reaction medium is a molten salt, the calcium silicide is reacted with the metal remover to obtain pure Si.
  • Fig. 8 shows a unit cell structure of MgSi in which Si particles form a face-centered cubic structure, Mg particles form a simple cubic structure, and the unit cell of the entire MgSi may have a layer of a to e.
  • the MgSi is reacted with the metal removing agent, the Mg particles of the b layer and the d layer are removed, and the gap between the a layer and the c layer and between the c layer and the e layer is large, that is, an interlayer gap is formed.
  • the above mechanism theoretically explains the formation mechanism of the layered silicon core, and the metal silicide is removed due to various distortions (such as line defects, surface defects, and body defects) in the unit cell structure of the prepared metal silicide.
  • the thickness of the different silicon-based material layers of the layered silicon core formed after the metal may be different, and the size of the interlayer gaps between different adjacent silicon-based material layers may also be different.
  • a large number of interlayer voids of the layered silicon core can reduce the expansion pressure of the anode material in the state of lithium insertion (or other ions released from the positive electrode of the battery), and reduce the charge and discharge process.
  • the change of the volume of the battery anode material in the battery effectively avoids the powdering of the battery anode material and improves the service life of the battery anode material.
  • Step 22 preparing a plurality of graphene layers on the layered silicon core, the graphene layer being located in the interlayer gap of the adjacent two silicon-based material layers, and the graphene layer and the adjacent two silicon-based material layers There is a gap between the at least one layer of silicon-based material.
  • the graphene layer can be prepared in the inter-layer voids of the layered silicon core by various means, including but not limited to the following manners:
  • the graphene layer is grown in situ in the interlayer void of the layered silicon core.
  • the specific process may be: heating the layered silicon core, heating to a set temperature, continuously introducing hydrogen H 2 and a gaseous carbon source, and The graphene layer is formed in the interlayer voids of the layered silicon core by holding it for a while, then turning off the gaseous carbon source and cooling it with argon Ar gas.
  • the gaseous carbon source may be a gaseous hydrocarbon containing carbon, including but not limited to methane, ethane, propane, ethylene, propylene, acetylene, and the like.
  • the layered graphene which has been prepared is migrated into the interlayer gap of the layered silicon core to form a graphene layer in the interlayer gap of the layered silicon core.
  • a solution such as alcohol, isopropanolamine (IPA), etc.
  • IPA isopropanolamine
  • the graphene-rich substrate is etched away, and graphene is precipitated in the liquid phase. Migrating into the inter-layer voids of the layered silicon core.
  • a layered silicon core is prepared, and the interlayer void of the layered silicon core is used to effectively suppress the expansion pressure of the composite during lithium insertion, reduce the volume change of the composite during charge and discharge, and improve the battery anode material.
  • the service life is filled in the interlaminar spaces of the layered silicon core, and the layers of the silicon-based material are supported by graphene to increase the strength of the layered silicon core and prevent the layered silicon core from undergoing repeated expansion and contraction. The structure collapsed.
  • graphene has excellent electrical conductivity, contributes to electron transport, and can improve the electrical conductivity of the composite.
  • a graphene cap layer may be prepared on the outer surface of the layered silicon core.
  • graphene when graphene is grown by a CVD process, graphene can be grown on the interlaminar voids of the layered silicon core and the outer surface of the layered silicon core.
  • the graphene when the graphene is migrated to the interlayer gap of the layered silicon core by migration, a part of the graphene may be migrated to the outer surface of the layered silicon core.
  • a graphene coating layer is formed on the outer surface of the layered silicon core, which can further improve the conductivity of the layered silicon core, and the graphene coating layer on the outer surface of the layered silicon core has good flexibility and can It has a good buffering effect on the expansion of the layered silicon core.
  • the method further includes:
  • a cladding layer is prepared on the outer surface of the layered silicon core, which coats the layered silicon core.
  • the coating layer may be an amorphous carbon coating layer, or may be an inorganic compound coating layer such as a lithium titanate coating layer, or may be an organic coating layer such as a polyaniline coating layer.
  • the carbon coating layer can be prepared in various manners in the embodiments of the present application, including but not limited to: evaporation, sputtering, electroplating, CVD, and the like.
  • the layered silicon-graphene composite material formed in step 22 is mixed with a carbon source and cracked at a high temperature to form a carbon coating layer on the outer surface of the layered silicon-graphene composite material.
  • the carbon source is a gaseous carbon source, a liquid carbon source or a solid carbon source
  • the gaseous carbon source includes but is not limited to methane, ethane, ethylene, acetylene, propylene, carbon monoxide, etc.
  • the liquid carbon source includes but is not limited to Methanol, ethanol, n-hexane, cyclohexane, benzene, toluene, xylene, etc.
  • solid carbon sources include, but are not limited to, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, polystyrene, rings Oxygen resin, phenolic resin, glucose, fructose, sucrose, maltose, coal tar pitch, petroleum pitch, and the like.
  • step 23 can also be performed after the graphene cap layer is prepared on the outer surface of the layered silicon core.
  • a coating layer is prepared on the outer surface of the layered silicon core to solidify the layered silicon core, thereby avoiding direct contact between the layered silicon core and the electrolyte, reducing side reactions and preventing powdering of silicon during long-term circulation. Further improve cycle performance.
  • a layered silicon core is coated with a carbon coating, an efficient conductive interface can be provided to improve power performance.
  • Application Example 1 A composite material was prepared using a silicon lithium compound precursor.
  • Step 1 Preparation of a lithium-lithium compound precursor: a stoichiometric ratio of a silicon Si block to a lithium Li band (in consideration of evaporation loss of lithium Li, Li requires an excess of 7%) is reacted by arc melting in an Ar gas environment to generate Li 12 Si 7 compound. After cooling down, the resulting cake was ground into a powder in a mortar box filled with Ar argon.
  • Step 2 Preparation of amorphous layered silicon: 1.0 g of the above Li 12 Si 7 powder was placed in a three-necked flask equipped with magnetic stirring, and placed in a glove box filled with Ar gas. 120 mL of ethanol was added to the flask, stirring was continued for several hours, and the product was transferred into a Buchner funnel and filtered with a filter paper. The filter residue was washed three times with distilled water and 1 M HCl, and then washed with distilled water until neutral to obtain a black water-insoluble solution. product. The product was heated at 120 ° C for 3 h in a tube furnace under the protection of Ar gas to obtain an amorphous layered silicon material.
  • Step 3 preparing a layered silicon-graphene composite material: placing the obtained amorphous layered silicon material in a clean quartz boat, transferring it to a furnace, and introducing a shielding gas (such as a hydrogen-argon mixed gas) to 20 The rate of °C/min is raised to 1000 °C for 20 min; then the protective gas is stopped, and a carbon source gas (such as methane) is introduced, and the reaction is completed for 30-120 min. The reaction is completed; the mixture is cooled to room temperature under a protective atmosphere to obtain a layered layer. Silicon-graphene composite.
  • a shielding gas such as a hydrogen-argon mixed gas
  • Application Example 2 A composite material was prepared using a silicon calcium compound precursor.
  • Step one preparing a precursor of a calcium-calcium compound: mixing the pure calcium powder with the pure silicon powder uniformly, placing it in a hard-burning porcelain boat, rapidly placing the porcelain boat into the quartz reaction tube, and introducing the CO 2 , the porcelain boat has been When heated to 1000 ° C, it takes only a few seconds for the mixture to melt and the reaction proceeds intensely.
  • the porcelain boat was taken out, and the product CaSi was immediately condensed to obtain a metallic gray lead-colored porous mass CaSi, which was pulverized.
  • CaSi was mixed uniformly with a calculated amount of Si powder, placed in a nickel boat, and heated at 1000 ° C in a H 2 gas stream. The final stage of the reaction proceeds slowly and requires heating for 15 h to obtain CaSi 2 .
  • Step 2 preparing an amorphous layered silicon-based material, wherein the CaSi 2 prepared in the first step and the metal removing agent are reacted in different reaction media to obtain silicon-based materials of different oxidation states, including but not limited to the following manners:
  • Method b Preparation of amorphous layered SiO x : 0.2 g of CaSi 2 was mixed with 40 mL of 0.1 M SnCl 2 ethanol solution, and the reaction was stirred at 60 ° C for 10 h. The product obtained was filtered, washed with ethanol and dried under vacuum at 80 ° C for 24 h. Sn nanoparticles resulting solution was removed with HCl in ethanol to give the amorphous SiO x layer structure.
  • the reaction formula is as follows:
  • Method c preparing amorphous layered Si: 1 g of CaSi 2 /SnCl 2 (molar ratio 1:1.5) was mixed with 10 g of LiCl/KCl (molar ratio 59:41), and uniformly ground in a glove box filled with Ar gas to obtain The powder was placed in a ceramic crucible and sintered at 400 ° C for 5 h under Ar gas protection. The obtained product was washed with ethanol and then dried under vacuum at 80 ° C for 24 h. The resulting tin Sn nanoparticles were removed with a solution of HCl in ethanol to obtain a layered amorphous Si. The response is as follows:
  • layered silicon-graphene composite material the amorphous layered silicon material obtained in step 2 is placed in a clean quartz boat, and transferred to a furnace, and a protective gas (such as a mixture of hydrogen and argon) is introduced. Raise to 1000 ° C at a rate of 20 ° C / min, for 20 min; then stop the introduction of shielding gas, and pass a carbon source gas (such as methane), the reaction is 30 ⁇ 120min, the reaction is completed; cooled to room temperature under a protective atmosphere, Layered silicon-graphene composite.
  • a protective gas such as a mixture of hydrogen and argon
  • the above process for preparing the composite material is simple and the cost is low, and the prepared layered silicon-graphene composite material not only has strong strength and electrical conductivity when used as a battery negative electrode, but also has a volume change during charge and discharge of the battery. Small, stable structure and long service life.
  • FIG. 9 shows a battery provided by an embodiment of the present application, including a housing 301, a positive electrode 302, a negative electrode 303, and an electrolyte 304.
  • the positive electrode 302, the negative electrode 303, and the electrolyte 304 are housed in the casing 301.
  • the electrode material of the above positive electrode 302 may be a lithium-containing compound such as lithium manganate, lithium iron phosphate, lithium nickel cobalt manganese oxide or the like.
  • the electrode material of the negative electrode 303 is the composite material 100, or the electrode material of the negative electrode 303 is prepared by the above steps 21 to 22 or steps 21 to 23.
  • the positive electrode 302 When the battery is charged, the positive electrode 302 releases a cation such as lithium ion, and the lithium ion released from the positive electrode moves to the negative electrode 303 through the electrolyte to be embedded in the negative electrode material. On the contrary, when the battery is discharged, the anode 303 releases the cation, and the cation moves to the cathode 302 through the electrolyte to be embedded in the cathode material.
  • the electrolyte 304 may be ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, phosphorus pentafluoride, hydrofluoric acid or the like. It should be understood that the battery may also include a structure such as a diaphragm 305, an extraction electrode, and the like.
  • the composite material 100 for preparing the anode 303 is in the lithium intercalation state, lithium ions are intercalated into the silicon-based material layer 111, the volume of the silicon-based material layer 111 becomes large, and the inter-layer gap between the silicon-based material layers 111 becomes small, and the layer is The reduced inter-layer voids of the silicon core 110 can reduce the overall outward extent of the layered silicon core 110. Therefore, the layered silicon core 110 structure can reduce the volume change of the composite material 100 during the delithiation state-lithium state transition, and reduce the probability of composite cracking and pulverization.
  • the graphene layer 120 in the interlaminar spaces of the layered silicon core 110 has a strong strength and can provide the composite material 100 with stable interlayer support.
  • the graphene layer 120 in the interlaminar spaces of the layered silicon core 110 can also enhance the interlayer electron conduction of the silicon-based material layer 111, enhance the electrical conductivity of the composite material 100, and thereby improve the performance of the battery.
  • the embodiment of the present application provides a method for improving a silicon negative electrode material of a lithium ion battery to solve the problem that the silicon negative electrode material is easily broken and pulverized.
  • the method comprises: using a layered silicon core as a main body of a silicon anode material, wherein the layered silicon core comprises a plurality of silicon-based material layers, and between the two adjacent silicon-based material layers, an interlayer gap, the silicon base
  • the material layer includes an oxide of silicon or silicon.
  • the interlayer gap between two adjacent layers of the layered silicon core can alleviate the expansion pressure of the silicon anode material in the lithium intercalation state, because the silicon-based material layer can expand to the interlayer gap after intercalating lithium, thereby reducing the entire
  • the volume change of the layered silicon core reduces the probability of cracking and chalking of the composite.
  • a plurality of graphene layers are further disposed inside the layered silicon core, each of the graphene layers being located in an interlayer gap of two adjacent ones of the silicon-based material layers, and each of the graphites
  • the olefin layer has a void between at least one of the two adjacent silicon-based material layers.
  • the graphene layer in the interlaminar voids of the layered silicon core has strong strength and can provide stable interlayer support to the composite. Moreover, the graphene layer in the interlaminar void of the layered silicon core can also enhance the interlayer electron conduction of the silicon-based material layer 111, enhance the electrical conductivity of the composite material, and thereby improve the performance of the battery.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

Un matériau composite et son procédé de préparation sont utilisés pour résoudre le problème de l'état de la technique selon lequel un matériau d'électrode négative en silicium dans une batterie est facilement cassé et pulvérisé. Le matériau composite comprend un noyau interne en silicium lamellaire et une pluralité de couches de graphène, le noyau interne en silicium lamellaire comprenant une pluralité de couches de matériau à base de silicium ; il existe un espace intermédiaire entre deux couches de matériau à base de silicium adjacentes ; les couches de matériau à base de silicium comprennent du silicium ou de l'oxyde de silicium ; chaque couche de graphène est disposée dans l'espace intercalaire entre deux couches de matériau à base de silicium adjacentes ; il existe un espace entre chaque couche de graphène et au moins une couche de matériau à base de silicium dans deux matériaux à base de silicium adjacents.
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