WO2013017101A2 - 用作锂离子电池负极材料的介孔硅复合物及其制备方法 - Google Patents

用作锂离子电池负极材料的介孔硅复合物及其制备方法 Download PDF

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WO2013017101A2
WO2013017101A2 PCT/CN2012/079649 CN2012079649W WO2013017101A2 WO 2013017101 A2 WO2013017101 A2 WO 2013017101A2 CN 2012079649 W CN2012079649 W CN 2012079649W WO 2013017101 A2 WO2013017101 A2 WO 2013017101A2
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mesoporous silicon
composite
phase
metal
carbon layer
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PCT/CN2012/079649
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English (en)
French (fr)
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杨军
高鹏飞
张敬君
周龙捷
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罗伯特·博世有限公司
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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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/06—Metal silicides
    • 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
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0421—Methods of deposition of the material involving vapour deposition
    • H01M4/0428—Chemical vapour deposition
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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 invention relates to the field of batteries, and in particular to a mesoporous silicon composite composed of a mesoporous silicon phase, a metal silicide phase and a carbon phase which can be used as a negative electrode material for a lithium ion battery, and a method for preparing the same.
  • a mesoporous silicon composite composed of a mesoporous silicon phase, a metal silicide phase and a carbon phase which can be used as a negative electrode material for a lithium ion battery, and a method for preparing the same.
  • graphite as a form of carbon is the most important negative electrode material for lithium ion batteries commonly used in mobile phones, notebook computers, digital cameras, power tools, and the like.
  • current lithium-ion battery systems and technologies face many new challenges, such as lower specific energy density, battery pack safety issues, and higher unit energy Wh.
  • the main reason for the lower specific energy density of current lithium ion batteries is related to the type of negative electrode used in batteries.
  • the graphite anode currently used has a low capacity for storing lithium ions (theoretically 372 mAh/g), which causes a problem that the overall storage capacity of the battery is low.
  • New materials, methods and techniques should be developed for lithium-ion batteries before they can be used in large quantities in pure electric vehicles and plug-in electric vehicles.
  • silicon has the highest theoretical specific capacity (4200 mAh/g) and low discharge potential, it is one of the most promising anode materials for lithium-ion batteries.
  • Si/C composites For many years, the use of Si/C composites has been studied to avoid the limitations of pure silicon powder.
  • Conventional composites are typically made by pyrolysis, mechanical mixing and grinding, or some combination of these two processing methods, which consist of silicon particles embedded in a dense carbon matrix.
  • silicon particles embedded in a dense carbon matrix.
  • the extent to which carbon can be accommodated is limited, so only limited stability and capacity improvements are obtained.
  • Porous structures are an effective way to accommodate volume changes.
  • Zheng, Y. et al., Electrochim. Acta, 2007. 52(19): p. 5863-5867 discloses the introduction of graphite and heat
  • the carbon-dissolved nanoporous silicon composite was prepared by a two-step ball milling followed by a template process using hydrochloric acid etching.
  • the first charge specific capacity is 649 mAh/g
  • the first discharge specific capacity is 1019 mAh/g
  • the efficiency is 64%.
  • the composite showed good cycle stability and the capacity was not attenuated after up to 120 cycles due to nano-sized pores in the silicon particles. However, the reversible capacity of the composite is relatively low.
  • CN 1761089 A discloses a silicon/carbon/graphite composite anode material for a lithium ion battery, wherein the composite anode material has an elemental silicon content of 10 to 80% by weight, a graphite particle content of 10 to 60% by weight, and a balance of amorphous. carbon.
  • the first charge has a specific capacity of 1115 mAh/g
  • the first discharge has a specific capacity of 1365 mAh/g
  • the efficiency is 82%.
  • the charge capacity of the 10th cycle was 784 mAh/g, while the discharge specific capacity was 838 mAh/g, and the capacity retention rate was 70%. Summary of the invention
  • the present invention provides a mesoporous silicon composite as a negative electrode material for a lithium ion battery, and the mesoporous silicon composite using the negative electrode material has higher reversible capacity and more stable cycle performance than the prior art, and is provided for use in a preparation
  • the method of mesoporous silicon composites is simpler and more environmentally friendly than the prior art.
  • a mesoporous silicon composite composed of a mesoporous silicon phase, a metal silicide phase, and a carbon phase
  • the metal silicide is embedded in mesoporous silicon particles, and the surface of the mesoporous silicon particles is covered with a carbon layer.
  • the weight ratio of silicon element to metal element is 2:3 to 900:1; the pores of mesoporous silicon particles have a size distribution of 2 to 80 nm, preferably 3 to 70 nm, more preferably 3 to 50 nm, particularly preferably 3 Size distribution to 5 nm and 20 to 50 nm.
  • the weight ratio of the silicon element to the metal element is preferably from 2:1 to 60:1, more preferably from 8:3 to 12:1, particularly preferably from 5:1 to 6: 1.
  • the metal silicide may be selected from the group consisting of nickel silicide, cobalt silicide such as CoSi 2 , and iron silicide.
  • a method of preparing a mesoporous silicon composite comprising a mesoporous silicon phase, a metal silicide phase, and a carbon phase, the method comprising the steps of:
  • a method of preparing a mesoporous silicon composite comprising a mesoporous silicon phase, a metal silicide phase, and a carbon phase is provided, the method comprising the steps of:
  • step 3 adding the washed product in step 2) to the metal chloride solution, removing the solvent, and performing thermal reduction in a reducing atmosphere containing hydrogen, and
  • step 3) The product of step 3) is coated with a carbon layer to obtain the mesoporous silicon composite.
  • the amount of each starting material used can be determined by the weight ratio of each element in the mesoporous silicon composite.
  • the carbon layer may be formed by chemical vapor deposition (CVD) or polymer pyrolysis, preferably polymer pyrolysis, including in-situ polymerization and pyrolysis, and polymer solution pyrolysis, with particular preference. It is a pyrolysis method for polymer solutions.
  • the polymer is, for example, polyvinyl chloride (PVC), asphalt and/or polyacrylonitrile (PAN), or a combination thereof.
  • the present invention relates to an electrode material and a battery comprising the above composite.
  • FIG. 1 is a schematic view showing the structure of a mesoporous silicon composite.
  • Figure 2 shows the X-ray diffraction spectrum of a mesoporous silicon composite (Si/CoSi 2 /C).
  • Figure 3 shows a transmission electron microscopy (TEM) photograph (a) of a mesoporous silicon composite (Si/CoSi 2 /C) and a TEM photograph (b) of a partially enlarged mesoporous silicon phase.
  • TEM transmission electron microscopy
  • Figure 4 is a graph showing the pore size distribution of the mesoporous silicon/metal silicide composite (Si/CoSi 2 ) obtained by the BJH method.
  • Figure 5 shows the charge and discharge curves of a mesoporous silicon composite (Si/CoSi 2 /C) electrode.
  • Figure 6 shows the cycle performance curves of mesoporous silicon composite (Si/CoSi 2 /C) electrodes.
  • Figure 7 shows the X-ray diffraction spectrum of a mesoporous silicon composite (Si/CoSi 2 /C) of one embodiment. detailed description
  • the present application describes the embedding of metal silicide, graphite or conductive carbon black and/or combinations thereof in mesoporous silicon particles, wherein the embedding can be any one of the following states or a combination of several states:
  • the mesoporous silicon particles completely or partially encapsulate the metal silicide particles; 2) the metal silicide completely or partially encapsulates the mesoporous silicon particles; 3) the mesoporous silicon particles are distributed in the interstices between the particles of the metal silicide; 4) the metal The silicide particles are distributed in the interstices between the mesoporous silicon particles; 5) any other equivalent embedding manner that achieves substantially the same or similar technical effects.
  • the surface of the mesoporous silicon particles is coated with a carbon layer, wherein the coating state may be any one of the following states or a combination of several states: 1) all or part of the surface of the mesoporous silicon particles is continuous The carbon layer is coated; 2) all or part of the surface of the mesoporous silicon particles is covered by a discontinuous carbon layer, or carbon particles; 3) any other equivalent coating method that can obtain substantially the same or similar technical effects.
  • One aspect of the invention relates to a mesoporous silicon composite composed of a mesoporous silicon phase, a metal silicide phase and a carbon phase, characterized in that the metal silicide is embedded in mesoporous silicon particles, mesoporous silicon particles
  • the surface is coated with a carbon layer; the weight ratio of silicon element to metal element is 2:3 to 900:1; the pore of mesoporous silicon particles has a size of 2 to 80 nm, preferably 3 to 70 nm, more preferably 3 to 50 nm.
  • the distribution particularly preferably having a size distribution of 3 to 5 nm and 20 to 50 nm.
  • the weight ratio of the silicon element to the metal element is preferably from 2:1 to 60:1, more preferably from 8:3 to 12:1, particularly preferably from 5:1 to 6:1.
  • the carbon content is preferably from 10 to 50% by weight, more preferably from 20 to 40% by weight, based on the total weight of the composite.
  • the metal silicide may be selected from the group consisting of nickel silicide, cobalt silicide, and iron silicide, preferably CoSi 2 .
  • the carbon layer may be formed by polymer pyrolysis or CVD.
  • the polymer may be any polymer capable of forming a carbon layer by pyrolysis, such as PVC, pitch and/or PAN, or a combination thereof.
  • a certain amount of graphite or conductive carbon black is additionally embedded in the mesoporous silicon particles as a dispersing agent while improving conductivity.
  • the amount of additionally introduced graphite or conductive carbon black is from 2 to 10% by weight, preferably from 6 to 8% by weight, based on the total weight of the composite.
  • the above mesoporous silicon composite (silicon/metal silicide/carbon) for the anode material of a lithium ion battery is composed of a mesoporous silicon phase, a metal silicide phase, and a carbon phase, and exhibits high reversible capacity and stable cycle performance. Mainly due to the combination of the mesoporous structure and the alloy phase.
  • the mesopores in the silicon provide space for volume expansion while the metal silicide alloy phase protects the composite from cracking and chalking.
  • Figure 1 shows the structure of a mesoporous silicon composite.
  • the mesoporous silicon composite is composed of a mesoporous silicon phase, a metal silicide phase, and a carbon phase, wherein the metal silicide is embedded in the mesoporous silicon particles, and the surface of the mesoporous silicon particles is covered with the carbon layer.
  • the surface of the silicon particles is coated with a carbon layer, preferably a partially graphitized carbon layer, which effectively buffers the volume effect of the silicon particles during charge and discharge, improves the structural stability and complexation of the silicon particles during lithium insertion and deintercalation.
  • the conductive property avoids the direct contact of the silicon surface with the electrolyte to reduce the irreversible capacity loss caused by the side reaction, and improves the electron conductivity between the silicon particles, thereby greatly improving the cycle stability of the entire electrode.
  • Yet another aspect of the present invention is also directed to a method (1) of preparing a mesoporous silicon composite composed of a mesoporous silicon phase, a metal silicide phase, and a carbon phase, the method comprising the steps of:
  • the washed product is coated with a carbon layer to obtain a mesoporous silicon composite.
  • the amount of each starting material used can be determined by the weight ratio of each element in the mesoporous silicon composite.
  • SiCl 4 , LiSi alloy powder, and metal powder are first ball-milled.
  • the conditions of the ball milling step are well known to those skilled in the art.
  • a Si/metal silicon compound/LiCl composite is obtained by a ball milling step in which a metal silicon compound is embedded in the silicon particles.
  • the LiSi alloy used herein is not particularly limited, and any common LiSi alloy such as Li 13 Si 4 may be used.
  • Suitable metal powders for use herein are selected from the group consisting of nickel powder, cobalt powder and iron powder, preferably cobalt powder.
  • the metal silicon compound is a nickel silicide (such as NiSi, Ni 2 Si), a cobalt silicide (such as CoSi 2 ), and an iron silicide (such as FeSi 2 ).
  • the ball milled product is optionally heat treated to allow the reaction between the above materials to proceed sufficiently and to obtain an alloy phase having a suitable grain size.
  • the conditions of the heat treatment process are well known to those skilled in the art, for example, heating at a rate of 5 ° Omin 4 to 500 to 1000 ° C, preferably 700 to 1000 ° C, particularly preferably to about 900 ° C, and The temperature is maintained for 1 to 6 hours, preferably 1 to 3 hours, particularly preferably about 2 hours, and then naturally cooled to room temperature.
  • the pores of the mesoporous silicon/metal silicide composite particles have a size distribution of 2 to 80 nm.
  • the mesoporous silicon/metal silicon compound composite prepared as above was coated with a carbon layer.
  • the carbon layer may be formed by chemical vapor deposition (CVD) or polymer pyrolysis, preferably polymer pyrolysis, including in-situ polymerization and pyrolysis, and polymer solution pyrolysis, particularly preferably polymer solution heat. solution.
  • the polymer is used in an amount of 11 to 66 parts by weight, preferably 33 to 50 parts by weight, per 100 parts by weight of the mesoporous silicon/metal silicide composite.
  • the solvent in the polymer solution may be a solvent which is soluble in a polymer and is a volatile solvent commonly used in the art, such as tetrahydrofuran (THF), acetone, dimethylformamide (DMF), ethanol or the like.
  • THF tetrahydrofuran
  • DMF dimethylformamide
  • concentration of the polymer solution is also well known to those skilled in the art.
  • the conditions of the CVD method employed are well known to those skilled in the art, for example, using toluene as a raw material, using argon as a carrier, and treating at 700 to 900 ° C, preferably at about 800 ° C for 1 to 2 hours, preferably about 1.5. In hours, a coated carbon layer is obtained.
  • the water-washed ball mill product is dispersed in a polymer solution to form a dispersion. Pyrolysis is then carried out to obtain a mesoporous silicon composite.
  • the polymer may be any polymer capable of forming a carbon layer by pyrolysis, such as PVC, asphalt, and/or PAN, or a combination thereof.
  • the conditions of the pyrolysis process are well known to those skilled in the art, for example, heating at a rate of 5 °O min- 1 to 700 to 1000 ° C, preferably 800 to 1000 ° C, particularly preferably to about 900 ° C, and It is maintained at this temperature for 1 to 6 hours, preferably 1 to 3 hours, particularly preferably about 2 hours.
  • Still another aspect of the invention relates to a method (2) for preparing a mesoporous silicon composite composed of a mesoporous silicon phase, a metal silicide phase, and a carbon phase, the method comprising the steps of:
  • step 3 adding the washed product in step 2) to the metal chloride solution, removing the solvent, and performing thermal reduction in a reducing atmosphere containing hydrogen, and
  • step 3) The product of step 3) is coated with a carbon layer to obtain the mesoporous silicon composite.
  • the amount of each starting material used can be determined by the weight ratio of each element in the mesoporous silicon composite.
  • the SiCl 4 and LiSi alloy powders are first ball-milled.
  • the conditions of the ball milling step are well known to those skilled in the art.
  • the Si/LiCl composite was obtained by a ball milling step.
  • the LiSi alloy to be used is not particularly limited, and any common LiSi alloy such as U 13 Si 4 can be used.
  • the ball milled product is optionally heat treated to allow the reaction between the above materials to proceed sufficiently and to obtain an alloy phase having a suitable grain size.
  • the conditions of the heat treatment process are well known to those skilled in the art, for example, heating at a rate of 5 ° Omin 4 to 500 to 1000 ° C, preferably 700 to 1000 ° C, particularly preferably to about 900 ° C, and The temperature is maintained for 1 to 6 hours, preferably 1 to 3 hours, particularly preferably about 2 hours, and then naturally cooled to room temperature.
  • the pores of the mesoporous silicon particles have a size distribution of 2 to 80 nm.
  • Suitable metal chlorides for use herein are selected from the group consisting of nickel chloride, cobalt chloride and ferric chloride or hydrates thereof, preferably cobalt chloride or a hydrate thereof.
  • the solvent in the metal chloride solution may use a solvent which is soluble in a metal chloride and is volatile, such as tetrahydrofuran (THF), acetone, dimethylformamide (DMF), ethanol, etc., which are commonly used in the art. .
  • the concentration of the metal chloride solution is also well known to those skilled in the art.
  • the reducing atmosphere may contain an inert gas such as argon.
  • the content of hydrogen in the reducing atmosphere is not particularly limited and is well known to those skilled in the art, for example, 5% by volume.
  • thermal reduction process conditions of the thermal reduction process are well known to those skilled in the art, for example by first performing a heat treatment at a lower temperature of 300 to 500 ° C, preferably about 400 ° C for 1 to 3 hours, preferably about 2 hours; The heat treatment is carried out at a higher temperature of 800 to 1000 ° C, preferably about 900 ° C, for 0.5 to 2 hours, preferably for about 1 hour, and then naturally cooled to room temperature.
  • the mesoporous silicon/metal silicon compound composite prepared as above was coated with a carbon layer in the same manner as in the method (1).
  • the mesoporous silicon composite prepared by the preparation method comprises a mesoporous silicon phase, a metal silicide phase and a carbon phase, wherein the metal silicide is embedded in the mesoporous silicon particles, and the surface of the mesoporous silicon particles is carbonized. Layer coating.
  • graphite or conductive carbon black may additionally be embedded in the mesoporous silicon composite to improve conductivity.
  • the graphite or conductive carbon black is used in an amount of 0.1 to 9 parts by weight, preferably 2 to 5 parts by weight, per 100 parts by weight of the mesoporous silicon composite.
  • porous silicon In order to form porous silicon, an expensive and environmentally unfriendly acid is used according to the templating method of the prior art, except that the method according to one aspect of the invention requires only water washing to form a mesoporous silicon phase.
  • An advantage of this method is therefore that the synthesis of the composite is new and simpler compared to the preparation of porous silicon composites according to the prior art.
  • the mesoporous silicon composite can be used as a negative electrode material for a lithium ion battery
  • the positive electrode material can be, for example, lithium iron dihydrochloride (LiFeP0 4 ), lithium manganese oxide (LiMn 2 0 4 ) or doped lithium manganese oxide, Lithium manganese cobalt nickel oxide (LiNi 1/3 Mn 1/3 Co 1/3 0 2 ) or a mixed positive electrode material thereof.
  • the newly compounded product (main component: Si/CoSi 2 /LiCl) was then placed in a quartz tube in an argon-filled glove box and heated at a rate of 5 °Omin- 1 in a constant stream of argon. It was kept at 900 ° C for 2 hours and then naturally cooled to room temperature. After heat treatment, wash the product with deionized water (main The composition: Si/CoSi 2 /LiCl) was centrifuged 4 times to completely remove LiCl, and then vacuum dried at 100 ° C for 4 hours to obtain a mesoporous silicon/metal silicide composite (Si/CoSi 2 ).
  • Fig. 2 The X-ray diffraction spectrum of the prepared mesoporous silicon composite (Si/CoSi 2 /C) is shown in Fig. 2 . It can be seen from Fig. 2 that the diffraction peaks of the Si and CoSi 2 crystal phases are strong and there are no obvious peaks, which indicates that the purity of the formed 0) 81 2 phase is high, and the formed LiCl is Completely removed, and essentially contains no by-products.
  • FIG. 3 (a) A TEM photograph of the prepared mesoporous silicon composite (Si/CoSi 2 /C) is shown in Fig. 3 (a), and a TEM photograph of the partially enlarged mesoporous silicon phase is shown in Fig. 3 (b). It can also be clearly seen from Fig. 3 (a) that the surface of the silicon particles is coated with a carbon layer.
  • the pore size distribution of mesoporous silica prepared by the ASAP 2010 M+C specific surface area porosity and chemisorption analyzer of Micromeritics, USA was used. The results are shown in Fig. 4.
  • the pore diameter of the mesoporous silicon particles is in the range of about 3 to 50 nm.
  • the prepared mesoporous silicon composite (Si/CoSi 2 /C) and 20% by weight of a binder (solid content of 2% by weight of styrene-butadiene rubber-carboxymethylcellulose sodium emulsion) and 20% by weight
  • the conductive carbon black (Super P) was mixed, uniformly stirred, coated on a copper foil, and placed in an oven at 70 ° C for drying. Then, a punch having a diameter of 12 mm was punched into a pole piece, dried in a vacuum oven at 70 ° C for 8 hours, and then transferred to an argon-filled glove box.
  • the lithium metal plate is used as the counter electrode, the ENTEK PE porous film is the separator, 1 molM 1 of hexafluorodifluoroethylene carbonate and dimethyl carbonate ( 1 : 1 )
  • the mixed solution is an electrolyte, assembled into a CR2016 button battery, and subjected to a constant current charge and discharge test on the LAND battery test system (Wuhan Jinnuo Electronics Co., Ltd.).
  • the charge and discharge cutoff voltage is relative to Li/Li + 0.01 to 1.2 V.
  • the resulting charge and discharge curves are shown in Fig. 5, and the cycle performance is shown in Fig. 6, and is summarized in Table 1.
  • Example 2 (CVD coating carbon layer)
  • the newly compounded product (main component: Si/CoSi 2 /LiCl) was then placed in a quartz tube in an argon-filled glove box and heated at a rate of 5°Omin- 1 in a constant argon flow, and It was kept at 900 ° C for 2 hours and then naturally cooled to room temperature. After the heat treatment, the product was washed with deionized water (main component: Si/CoSi 2 /LiCl), and centrifuged 4 times to completely remove LiCl, and then vacuum dried at 100 ° C for 4 hours to obtain mesoporous silicon/metal silicidation. Complex (Si/CoSi 2 ).
  • the obtained mesoporous silicon/metal silicide composite (Si/CoSi 2 ) was placed in a quartz tube, loaded with Ar gas and loaded with toluene, and heated to 800 ° C for 1.5 hours to obtain a mesoporous silicon composite (Si/ CoSi 2 /C).
  • the pore diameter of the mesoporous silicon particles is in the range of about 3 to 50 nm.
  • the battery was assembled and tested for performance in the same manner as in Example 1.
  • the prepared mesoporous silicon composite (Si/CoSi 2 /C) has an initial discharge capacity of 1313.0 mAh/g, and the first charge capacity is 812.3 mAh/g, the first Coulomb efficiency was 61.9%.
  • the discharge capacity after 100 charge and discharge cycles was 767.0 mAh/g, and the charge capacity was 759.4 mAh/g.
  • Example 3 (cobalt chloride as a cobalt source)
  • the newly compounded product (main component: Si/LiCl) was then placed in a quartz tube in an argon-filled glove box, heated at a rate of 5 ° C * min 4 in a constant stream of argon, and at 900 Hold at °C for 2 hours and then naturally cool to room temperature. After the heat treatment, the product was washed with deionized water and centrifuged 4 times to completely remove LiCl, followed by vacuum drying at 100 ° C for 4 hours to obtain porous silicon. 0.80 g of cobalt chloride (CoCl 2 -6H 2 0) was dissolved in 10 ml of ethanol, then 1.34 g of porous silicon was added, stirred uniformly, and dried under vacuum at 60 ° C for 4 hours.
  • cobalt chloride CoCl 2 -6H 2 0
  • the solvent was evaporated and transferred to a corundum boat. Under a H 2 /Ar mixed gas (11 2 volume content 5%), heat treatment at 400 ° C for 2 hours, then heat up to 900 ° C heat treatment for 1 hour, and naturally cool to room temperature to obtain mesoporous silicon / metal silicide composite (Si/CoSi x ).
  • the obtained mesoporous silicon/metal silicide composite (Si/CoSi x ) was placed in a quartz tube, filled with Ar gas and charged with toluene, and heated to 800 ° C for 1.5 hours to obtain a mesoporous silicon composite.
  • the pore diameter of the mesoporous silicon particles is in the range of about 3 to 70 nm.
  • Fig. 7 The X-ray diffraction spectrum of the prepared mesoporous silicon composite (Si/CoSi x /C) is shown in Fig. 7. It can be seen from Fig. 7 that the diffraction peaks of the Si and CoSi x crystal phases are strong, and there is no obvious peak, which indicates that the purity of the formed 0) 8 phase is high, and the formed LiCl is Completely removed, and essentially contains no by-products.
  • the battery was assembled and tested for performance in the same manner as in Example 1.
  • the prepared mesoporous silicon composite had an initial discharge capacity of 1595.4 mAh/g, a first charge capacity of 931.9 mAh/g, and a first coulombic efficiency of 58.4%.
  • the discharge capacity after 50 charge and discharge cycles was 1076.7 mAh/g, and the charge capacity was 1047.6 mAh/g. It can be seen that the reversible capacity of the mesoporous silicon composite obtained by the present invention is significantly higher than that in the

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Abstract

本发明涉及由介孔硅相、金属硅化物相和碳相组成的介孔硅复合物，其特征在于，金属硅化物嵌入介孔硅颗粒中，介孔硅颗粒表面被碳层包覆；硅元素与金属元素的重量比为2:3至900:1；介孔硅颗粒的孔具有2至80nm的尺寸分布。本发明还涉及所述介孔硅复合物的制备方法。

Description

用作锂离子电池负极材料的介孔硅复合物及其制备方法
技术领域
本发明涉及电池领域， 具体而言， 涉及可用作锂离子电池负极材料 的由介孔硅相、金属硅化物相和碳相组成的介孔硅复合物及其制备方法。 背景技术
目前石墨作为一种碳的形式是通常用于手机、 笔记本电脑、 数码相 机、 电动工具等的锂离子电池的最重要的负极材料。 由于汽车工业在向 电动车转变， 目前的锂离子电池系统和技术面临着许多新的挑战， 例如 比能量密度低、 电池组安全性问题、 单位能量 Wh的价格高等。 目前的 锂离子电池的比能量密度比较低的主要原因与电池使用的负极类型有 关。 目前使用的石墨负极储存锂离子的容量低 （理论上为 372 mAh/g)， 这导致电池的整体储存容量低的问题。 在可以大量用于纯电动车和插电 式电动车之前， 应当为锂离子电池开发新型的材料、 方法和技术。
因为硅的理论比容量最高 （4200 mAh/g ) 且放电电位低， 所以是锂 离子电池最有希望的待选负极材料之一。 研究人员目前认识到， 若用硅 复合物代替石墨， 则可以将负极容量提高许多倍。 该方法的问题在于， 到目前为止， 由于在充电和放电循环中硅用锂离子加载所以容易破裂和 粉化。 因此电池的循环能力将会非常差。
许多年来有人已经研究了使用 Si/C复合物来避免纯硅粉的局限性。 传统复合物通常通过热解、 机械混合及研磨， 或者这两种加工方式的某 种组合而制得， 这些传统复合物由嵌入致密的碳基质中的硅颗粒组成。 然而， 对于在嵌锂时硅体积的较大变化， 碳对其可容纳的程度有限， 因 此仅可获得有限的稳定性和容量改善。
多孔结构是容纳体积变化的一种有效的途径。 Zheng, Y.等人， Electrochim. Acta, 2007. 52(19): p. 5863-5867公开了一种引入了石墨和热 解碳的纳米多孔硅复合物， 这是通过两步球磨接着用盐酸进行蚀刻的模 板法而制备的。 首次充电比容量为 649 mAh/g , 首次放电比容量为 1019 mAh/g， 效率为 64%。 该复合物显示出良好的循环稳定性， 经多达 120次循环后容量仍未衰减， 这归因于硅颗粒中的纳米尺寸的孔。 但是， 该复合物的可逆容量比较低。
CN 1761089 A公开了一种锂离子电池用硅 /碳 /石墨复合负极材料， 该复合负极材料中单质硅含量为 10至 80重量％，石墨颗粒含量为 10至 60重量％， 余量是无定形碳。 首次充电比容量为 1115 mAh/g， 首次放电 比容量为 1365 mAh/g， 效率为 82 %。 第 10 次循环的充电比容量为 784 mAh/g, 而放电比容量为 838 mAh/g， 容量保持率为 70%。 发明内容
本发明提供了作为锂离子电池负极材料的介孔硅复合物， 采用该负 极材料的介孔硅复合物与现有技术相比可逆容量更高且循环性能更稳 定， 以及提供了用于制备所述介孔硅复合物的方法， 其与现有技术相比 更加简单且更有益于环境。
根据一个方面， 提供了由介孔硅相、 金属硅化物相和碳相组成的介 孔硅复合物， 其特征在于， 金属硅化物嵌入介孔硅颗粒中， 介孔硅颗粒 表面被碳层包覆； 硅元素与金属元素的重量比为 2 : 3至 900 : 1 ; 介孔硅 颗粒的孔具有 2至 80 nm、优选 3至 70 nm、更优选 3至 50 nm的尺寸分 布、 特别优选具有 3至 5 nm及 20至 50 nm的尺寸分布。
在介孔硅复合物的一个实施方案中， 硅元素与金属元素的重量比优 选为 2 : 1至 60 : 1， 更优选为 8 : 3至 12 : 1， 特别优选为 5： 1至 6： 1。
在上述复合物中， 所述金属硅化物可选自镍硅化物、 钴硅化物如 CoSi2、 以及铁硅化物。
根据另一个方面， 提供了制备由介孔硅相、 金属硅化物相和碳相组 成的介孔硅复合物的方法， 该方法包括以下步骤：
1 )将 SiCl4、 LiSi合金粉和金属粉如镍粉、钴粉和 /或铁粉进行球磨； 2) 用水洗涤球磨的产品； 以及
3 ) 将经洗涤的产品包覆碳层， 从而获得所述介孔硅复合物。 根据另一个方面， 提供了制备由介孔硅相、 金属硅化物相和碳相组 成的介孔硅复合物的方法， 该方法包括以下步骤：
1 ) 将 SiCl4和 LiSi合金粉进行球磨；
2) 用水洗涤球磨的产品；
3 ) 将步骤 2) 中经洗涤的产品加入金属氯化物的溶液中， 去除溶剂 后， 在含有氢气的还原性气氛中进行热还原， 以及
4) 将步骤 3 ) 的产品包覆碳层， 从而获得所述介孔硅复合物。 各初始原料的使用量可以由介孔硅复合物中各元素的重量比加以确 定。
在该方法中， 所述碳层可以通过化学气相沉积 （CVD) 或聚合物热 解法形成， 优选为聚合物热解法， 包括原位聚合与热解以及聚合物溶液 热解法， 特别优选为聚合物溶液热解法。 所述聚合物例如是聚氯乙烯 (PVC)、 沥青和 /或聚丙烯腈 （PAN) , 或者它们的组合。
根据再一个方面， 本发明涉及含有上述复合物的电极材料和电池。 附图说明
以下将结合附图对本发明的各个方面进行更为详细的说明， 其中： 图 1所示为介孔硅复合物的结构示意图。
图 2所示为介孔硅复合物 （Si/CoSi2/C) 的 X射线衍射谱。
图 3所示为介孔硅复合物（Si/CoSi2/C) 的透射电子显微（TEM)照 片 （a) 以及局部放大的介孔硅相的 TEM照片 （b)。
图 4所示为根据 BJH法求得的介孔硅 /金属硅化物复合物（Si/CoSi2) 的孔径分布图。
图 5所示为介孔硅复合物 （Si/CoSi2/C) 电极的充放电曲线。
图 6所示为介孔硅复合物 （Si/CoSi2/C) 电极的循环性能曲线。 图 7所示为一个实施方案的介孔硅复合物（Si/CoSi2/C )的 X射线衍 射谱。 具体实施方式
除非另外说明， 本申请提到的所有的出版物、 专利申请、 专利和其 它参考文献都以引用的方式全文结合入本文中，相当于全文呈现于本文。
除非另外定义， 本文中使用的所有技术和科学术语具有本发明所属 领域普通技术人员通常所理解的同样含义。 在抵触的情况下， 以本说明 书包括定义为准。
当以范围、 优选范围、 或者优选的数值上限以及优选的数值下限的 形式表述某个量、 浓度或其它值或参数的时候， 应当理解相当于具体揭 示了通过将任意一对范围上限或优选数值与任意范围下限或优选数值结 合起来的任何范围， 而不考虑该范围是否具体揭示。 除非另外指出， 本 文所列出的数值范围旨在包括范围的端点， 和该范围之内的所有整数和 分数。
本申请中描述了在介孔硅颗粒中嵌入金属硅化物、 石墨或导电炭黑 和 /或上述的组合， 其中所述的嵌入可以是如下的任何一种状态或者几种 的状态的组合： 1 ) 介孔硅颗粒完全或部分包裹金属硅化物颗粒； 2 ) 金 属硅化物完全或部分包裹介孔硅颗粒； 3 )介孔硅颗粒分布在金属硅化物 的颗粒之间的空隙中； 4)金属硅化物颗粒分布在介孔硅颗粒之间的空隙 中； 5 )任何其他等同的、 可以获得实质上相同或相近技术效果的嵌入方 式。
本申请中描述了介孔硅颗粒表面被碳层包覆， 其中所述的包覆状态 可以是如下任何一种状态或者几种状态的组合： 1 )介孔硅颗粒全部或部 分表面被连续的碳层包覆； 2)介孔硅颗粒全部或部分表面被不连续的碳 层， 或者碳颗粒包覆； 3 )任何其他等同的、 可以获得实质上相同或相近 技术效果的包覆方式。 本发明的一个方面涉及由介孔硅相、 金属硅化物相和碳相组成的介 孔硅复合物， 其特征在于， 金属硅化物嵌入介孔硅颗粒中， 介孔硅颗粒 表面被碳层包覆； 硅元素与金属元素的重量比为 2 : 3至 900 : 1 ; 介孔硅 颗粒的孔具有 2至 80 nm、优选 3至 70 nm、更优选 3至 50 nm的尺寸分 布、 特别优选具有 3至 5 nm及 20至 50 nm的尺寸分布。
硅元素与金属元素的重量比优选为 2： 1至 60： 1， 更优选为 8： 3至 12 : 1 , 特别优选为 5： 1至 6： 1。基于所述复合物的总重量， 碳含量优选 为 10至 50重量％， 更优选为 20至 40重量％。
在介孔硅复合物中， 所述金属硅化物可选自镍硅化物、 钴硅化物和 铁硅化物， 优选为 CoSi2。
所述碳层可以是通过聚合物热解或 CVD法形成的。所述聚合物可以 是任意能够通过热解形成碳层的聚合物， 例如为 PVC、 沥青和 /或 PAN, 或者上述的组合。
所述介孔硅颗粒中优选还额外地嵌入有一定量的石墨或导电炭黑作 为分散剂， 同时能够改善传导性。 基于所述复合物的总重量， 额外引入 的石墨或导电炭黑的量为 2至 10重量％、 优选 6至 8重量％。
上述用于锂离子电池负极材料的介孔硅复合物 （硅 /金属硅化物 /碳） 由介孔硅相、 金属硅化物相和碳相组成， 显示出高的可逆容量和稳定的 循环性能， 这主要是可以归因于介孔结构与合金相的结合。 硅中的介孔 为体积膨胀提供了空间， 同时金属硅化物合金相保护所述复合物不发生 破裂和粉化。
图 1所示为介孔硅复合物的结构示意图。 该介孔硅复合物由介孔硅 相、 金属硅化物相和碳相组成， 其中金属硅化物嵌入介孔硅颗粒中， 介 孔硅颗粒表面被碳层包覆。
硅颗粒的表面被碳层包覆， 优选为部分石墨化的碳层， 这有效地缓 冲了在充放电过程中硅颗粒的体积效应， 改善了硅颗粒嵌脱锂时的结构 稳定性以及复合物的导电性能， 避免了硅表面与电解液直接接触而减少 副反应带来的不可逆容量损失， 并改善了硅颗粒之间的电子传导性， 从 而可以大幅改善整个电极的循环稳定性。 本发明的又一方面还涉及制备由介孔硅相、 金属硅化物相和碳相组 成的介孔硅复合物的方法 （1 )， 该方法包括以下步骤：
1 ) 将 SiCl4、 LiSi合金粉和金属粉进行球磨；
2) 用水洗涤球磨的产品； 以及
3 ) 将经洗涤的产品包覆碳层， 从而获得介孔硅复合物。 各初始原料的使用量可以由介孔硅复合物中各元素的重量比加以确 定。
具体而言， 首先对 SiCl4、 LiSi合金粉、 以及金属粉进行球磨。 所述 球磨步骤的条件是本领域技术人员所公知的。 由球磨步骤得到 Si/金属硅 化合物 /LiCl 复合物， 其中金属硅化合物嵌入在硅颗粒中。 在此使用的 LiSi合金没有特别的限制，可以使用任何常见的 LiSi合金，例如 Li13Si4。 在此所用的合适的金属粉选自镍粉、 钴粉和铁粉， 优选为钴粉。 相应地， 所述金属硅化合物为镍硅化物 （如 NiSi、 Ni2Si)、 钴硅化物 （如 CoSi2) 和铁硅化物 （如 FeSi2)。
任选地对球磨的产品进行热处理以使上述原料之间的反应充分进行 并获得具有合适晶粒尺寸的合金相。 所述热处理过程的条件是本领域技 术人员所公知的， 例如以 5°Omin4的速率加热到 500至 1000°C， 优选 700至 1000°C， 特别优选加热至约 900 °C， 并在该温度下保持 1至 6小 时， 优选 1至 3小时， 特别优选约 2小时， 然后自然冷却至室温。
接着， 用水、 优选去离子水洗涤， 除去 LiCl, 由此形成介孔硅 /金属 硅化物复合物。 此时， 该介孔硅 /金属硅化物复合物颗粒的孔具有 2 至 80 nm的尺寸分布。
最后， 将如上制得的介孔硅 /金属硅化合物复合物包覆碳层。 所述碳 层可以通过化学气相沉积 （CVD) 或聚合物热解法形成， 优选为聚合物 热解法， 包括原位聚合与热解以及聚合物溶液热解法， 特别优选为聚合 物溶液热解法。 相对于 100重量份的介孔硅 /金属硅化物复合物， 所述聚合物的使用 量为 11至 66重量份， 优选为 33至 50重量份。
所述聚合物溶液中的溶剂可以使用所属技术领域中常用的可溶解聚 合物且易挥发的溶剂，如四氢呋喃（THF)、丙酮、二甲基甲酰胺（DMF)、 乙醇等。 所述聚合物溶液的浓度也是本领域技术人员所公知的。
所采用的 CVD法的条件是本领域技术人员所公知的，例如使用甲苯 作为原料， 使用氩气作为载体， 在 700至 900°C、 优选约 800°C下处理 1 至 2小时， 优选约 1.5小时， 从而得到包覆的碳层。
具体而言， 将经水洗涤的球磨产品分散在聚合物溶液中， 形成分散 体。 然后进行热解， 从而获得介孔硅复合物。 所述聚合物可以是任意能 够通过热解形成碳层的聚合物， 例如为 PVC、沥青和 /或 PAN, 或者上述 的组合。 所述热解过程的条件是本领域技术人员所公知的， 例如以 5 °Omin— 1的速率加热到 700至 1000 °C，优选 800至 1000°C，特别优选加 热至约 900°C， 并在该温度下保持 1至 6小时， 优选 1至 3小时， 特别 优选约 2小时。
本发明的又一方面还涉及制备由介孔硅相、 金属硅化物相和碳相组 成的介孔硅复合物的方法 （2)， 该方法包括以下步骤：
1 ) 将 SiCl4和 LiSi合金粉进行球磨；
2) 用水洗涤球磨的产品；
3 ) 将步骤 2) 中经洗涤的产品加入金属氯化物的溶液中， 去除溶剂 后， 在含有氢气的还原性气氛中进行热还原， 以及
4) 将步骤 3 ) 的产品包覆碳层， 从而获得所述介孔硅复合物。 各初始原料的使用量可以由介孔硅复合物中各元素的重量比加以确 定。
具体而言， 首先对 SiCl4及 LiSi合金粉进行球磨。 所述球磨步骤的 条件是本领域技术人员所公知的。 由球磨步骤得到 Si/LiCl复合物。在此 使用的 LiSi合金没有特别的限制， 可以使用任何常见的 LiSi合金， 例如 U13Si4。
任选地对球磨的产品进行热处理以使上述原料之间的反应充分进行 并获得具有合适晶粒尺寸的合金相。 所述热处理过程的条件是本领域技 术人员所公知的， 例如以 5°Omin4的速率加热到 500至 1000°C， 优选 700至 1000°C， 特别优选加热至约 900 °C， 并在该温度下保持 1至 6小 时， 优选 1至 3小时， 特别优选约 2小时， 然后自然冷却至室温。
接着， 用水、 优选去离子水洗涤， 除去 LiCl, 由此形成介孔硅。 此 时， 该介孔硅颗粒的孔具有 2至 80 nm的尺寸分布。
然后， 将如上制得的介孔硅颗粒加入金属氯化物的溶液中， 在均匀 搅拌之后通过真空干去除溶剂。 在此所用的合适的金属氯化物选自氯化 镍、 氯化钴和氯化铁或其水合物， 优选为氯化钴或其水合物。 在此， 所 述金属氯化物溶液中的溶剂可以使用所属技术领域中常用的可溶解金属 氯化物且易挥发的溶剂，如四氢呋喃（THF)、丙酮、二甲基甲酰胺 (DMF)、 乙醇等。 所述金属氯化物溶液的浓度也是本领域技术人员所公知的。
然后， 在含有氢气的还原性气氛中进行热还原， 从而获得介孔硅 /金 属硅化物复合物 （Si/MSix)。 在此， 所述还原性气氛可以包含惰性气体， 例如氩气。 所述还原性气氛中氢气的含量没有特别的限制， 是本领域技 术人员所公知的， 例如为 5体积％。 所述热还原过程的其他条件是本领 域技术人员所公知的， 例如首先在 300至 500 °C、优选约 400°C的较低温 度下实施热处理 1至 3小时、 优选约 2小时； 接着在 800至 1000°C、 优 选约 900 °C的较高温度下实施热处理 0.5至 2小时、优选约 1小时， 然后 自然冷却至室温。
最后， 以与方法 （1 ) 相同的方式将如上制得的介孔硅 /金属硅化合 物复合物包覆碳层。 如图 1所示， 所述制备方法制得的介孔硅复合物由介孔硅相、 金属 硅化物相和碳相组成， 其中金属硅化物嵌入介孔硅颗粒中， 介孔硅颗粒 表面被碳层包覆。
根据本发明的一个实施方案， 在介孔硅复合物中还可额外地嵌入石 墨或导电炭黑以改善传导性。 在此情况下， 需要在第 1 ) 步中将 SiCl4、 LiSi合金粉、 金属粉连同石墨或导电炭黑一起进行球磨。 相对于 100重 量份的介孔硅复合物， 石墨或导电炭黑的使用量为 0.1至 9重量份， 优 选为 2至 5重量份。
为了形成多孔硅， 根据现有技术的模板法使用昂贵且对环境不利的 酸， 不同的是根据本发明一个方面的方法仅需进行水洗即可形成介孔硅 相。 所以该方法的一个优点在于， 与根据现有技术的多孔硅复合物的制 备方法相比， 复合物的该合成方法是新的并且更加简单。
介孔硅复合物可用作锂离子电池负极材料， 而正极材料例如可以使 用锂铁憐酸盐（LiFeP04)、 锂锰氧化物（LiMn204)或经掺杂的锂锰氧化 物、 锂锰钴镍氧化物 （LiNi1/3Mn1/3Co1/302) 或者它们的混合正极材料。
以下将参考实施例更为详细地说明本发明的具体实施方式， 但应理 解的是， 这些实施例仅是用于说明本发明， 而绝不是对本发明保护范围 的限制。 实施例 1
将 2 ml的 SiCl4 (Aladdin-reagent公司， 中国， 纯度 99.9% )、 0.84 克 Li13Si4粉（SIMIT, CAS,中国）、 0.15克钴粉（200目， Sinopharm Chemical Reagent有限公司）和 0.10克 Super P炭黑 (40 匪， Timical)连同 15个 直径 10 mm的玛瑙球装入充有氩气的 80 ml玛瑙瓶中。在 Planetary Mono Mill P-6 (Fritsch, 德国）上以 450 rpm的转速实施球磨 20小时。 然后在 充有氩气的手套箱中将新混炼的产品（主要成分： Si/CoSi2/LiCl)装入石 英管中， 在恒定的氩气流中以 5 °Omin- 1的速率加热， 并在 900°C下保持 2小时， 然后自然冷却至室温。在热处理之后， 用去离子水洗涤产品（主 要成分： Si/CoSi2/LiCl)，并离心分离 4次以完全去除 LiCl,然后在 100°C 下真空干燥 4小时， 得到介孔硅 /金属硅化物复合物 （Si/CoSi2)。 将 1.1 克所得的介孔硅 /金属硅化物复合物 (Si/CoSi2)加入 2.1克聚氯乙烯 (PVC, 平均 Mw~233,000， Aldrich)溶液（以 0.2 g/ml的浓度溶解在 10 ml四氢 呋喃中）， 并在超声波作用下均匀混合。在搅拌 1小时之后， 将所得的浆 料涂覆在平坦的表面上，在 80°C下干燥， 并在氩气氛中以 5°Omin4的速 率加热至 900 °C并保持 2 小时。 最终制得粉末状的介孔硅复合物 (Si/CoSi2/C
所制得的介孔硅复合物 （Si/CoSi2/C) 的 X射线衍射谱如图 2所示。 由图 2可以看出， Si和 CoSi2晶相的衍射峰强度很强， 不存在明显的杂 峰， 这尤其是表明所形成的 0)812相的纯度很高， 而所形成的 LiCl被完 全去除， 并且基本上不包含副产物。
所制得的介孔硅复合物（Si/CoSi2/C)的 TEM照片如图 3 (a)所示， 而局部放大的介孔硅相的 TEM照片如图 3 (b) 所示。 从图 3 (a) 还可 以清楚地看出在硅颗粒表面上包覆有碳层。
利用美国 Micromeritics公司的 ASAP 2010 M+C型比表面积孔隙度 及化学吸附分析仪测试所制得的介孔硅的孔径分布， 结果如图 4所示。 介孔硅颗粒的孔径在约 3至 50 nm的范围内。
下面依照现有技术中常用的方法测试所制得的介孔硅复合物 (Si/CoSi2/C) 的充放电曲线和循环性能。 电池组装过程及性能测试
将所制得的介孔硅复合物 （Si/CoSi2/C) 与 20重量％的粘结剂 （固 体含量为 2重量％的丁苯橡胶-羧甲基纤维素钠乳液） 和 20重量％的导 电碳黑 （Super P)混合， 搅拌均匀后涂覆在铜箔上， 放入烘箱中在 70°C 烘干。再用直径 12 mm的冲头冲成极片，放入真空烘箱中在 70°C下干燥 8小时，然后转移到充满氩气的手套箱中。以金属锂片为对电极， ENTEK PE 多孔膜为隔膜， 1 moM 1的六氟憐酸锂的碳酸乙烯酯与碳酸二甲酯 ( 1 ： 1 ) 混合溶液为电解液， 组装成 CR2016扣式电池， 在 LAND电池 测试系统 （武汉金诺电子有限公司） 上进行恒流充放电测试， 充放电截 止电压相对于 Li/Li+为 0.01至 1.2 V。所得的充放电曲线如图 5所示， 而 循环性能如图 6所示， 并汇总于表 1中。
Figure imgf000012_0001
Figure imgf000012_0002
实施例 2 (CVD法包覆碳层）
将 2 ml的 SiCl4 (Aladdin-reagent公司， 中国， 纯度 99.9% )、 0.84 克 Li13Si4粉（SIMIT, CAS,中国）、 0.15克钴粉（200目， Sinopharm Chemical Reagent有限公司）和 0.10克 Super P炭黑 (40匪， Timical)连同 15个 直径 10 mm的玛瑙球装入充有氩气的 80 ml玛瑙瓶中。在 Planetary Mono Mill P-6 (Fritsch, 德国）上以 450 rpm的转速实施球磨 20小时。 然后在 充有氩气的手套箱中将新混炼的产品（主要成分： Si/CoSi2/LiCl)装入石 英管中， 在恒定的氩气流中以 5°Omin- 1的速率加热， 并在 900°C下保持 2小时， 然后自然冷却至室温。在热处理之后， 用去离子水洗涤产品（主 要成分： Si/CoSi2/LiCl)，并离心分离 4次以完全去除 LiCl,然后在 100°C 下真空干燥 4小时， 得到介孔硅 /金属硅化物复合物 （Si/CoSi2)。 将所得 的介孔硅 /金属硅化物复合物 （Si/CoSi2) 置于石英管中， 通入 Ar气载入 甲苯， 升温至 800°C热处理 1.5小时， 得到介孔硅复合物 （Si/CoSi2/C)。 介孔硅颗粒的孔径在约 3至 50 nm的范围内。
以与实施例 1相同的方法组装电池并测试性能。 所制得的介孔硅复 合物 （Si/CoSi2/C) 的首次放电容量为 1313.0 mAh/g, 首次充电容量为 812.3 mAh/g, 首次库仑效率为 61.9%。 100次充放电循环后的放电容量 为 767.0 mAh/g， 充电容量为 759.4 mAh/g。 实施例 3 (氯化钴作为钴源）
将 2 ml的 SiCl4 (Aladdin-reagent公司， 中国， 纯度 99.9% )、 0.84 克 Li13Si4粉（SIMIT, CAS,中国）和 0.10克 Super P炭黑（40 nm， Timical) 连同 15个直径 10 mm的玛瑙球装入充有氩气的 80 ml玛瑙瓶中。 在 Planetary Mono Mill P-6 (Fritsch, 德国） 上以 450 rpm的转速实施球磨 20小时。然后在充有氩气的手套箱中将新混炼的产品（主要成分： Si/LiCl ) 装入石英管中， 在恒定的氩气流中以 5°C*min4的速率加热， 并在 900°C 下保持 2小时， 然后自然冷却至室温。 在热处理之后， 用去离子水洗涤 产品， 并离心分离 4次以完全去除 LiCl, 然后在 100°C下真空干燥 4小 时， 得到多孔硅。 将 0.80克氯化钴 (CoCl2-6H20) 溶于 10 ml乙醇中， 然后加入 1.34克多孔硅， 搅拌均匀， 在 60°C真空干燥 4小时， 将溶剂挥 发干净后转移至刚玉舟中在 H2/Ar混合气体下 （112体积含量 5% ) 先在 400°C热处理 2小时，然后升温到 900°C热处理 1小时， 自然冷却至室温， 得到介孔硅 /金属硅化物复合物（Si/CoSix)。将所得的介孔硅 /金属硅化物 复合物 （Si/CoSix) 置于石英管中， 通入 Ar气载入甲苯， 升温至 800°C 热处理 1.5小时， 得到介孔硅复合物。介孔硅颗粒的孔径在约 3至 70 nm 的范围内。
所制得的介孔硅复合物 （Si/CoSix/C) 的 X射线衍射谱如图 7所示。 由图 7可以看出， Si和 CoSix晶相的衍射峰强度很强， 不存在明显的杂 峰， 这尤其是表明所形成的 0)8^相的纯度很高， 而所形成的 LiCl被完 全去除， 并且基本上不包含副产物。
以与实施例 1相同的方法组装电池并测试性能。 所制得的介孔硅复 合物的首次放电容量为 1595.4 mAh/g， 首次充电容量为 931.9 mAh/g， 首 次库仑效率为 58.4%。 50次充放电循环后的放电容量为 1076.7 mAh/g, 充电容量为 1047.6 mAh/g。 由此可以看出， 本发明得到的介孔硅复合物的可逆容量明显高于在
Zheng, Y.等人， Electrochim. Acta, 2007. 52(19): p. 5863-5867中获得的 649 mAh/g o此外，根据 CN 1761089 A的复合负极材料在第 10次循环的 容量保持率仅为 70 % , 因此该介孔硅复合物具有更稳定的循环性能。
以上描述的具体实施方案只是用于阐释本申请的构思， 不应理解为 以任何方式限制本发明的范围。 相反， 应清楚地理解在阅读本文的说明 书之后， 本领域普通技术人员可以在不背离本发明精神之下实施其他的 技术方案、 修改等。

Claims

权 利 要 求 书
1、 由介孔硅相、 金属硅化物相和碳相组成的介孔硅复合物， 其特征 在于， 金属硅化物嵌入介孔硅颗粒中， 介孔硅颗粒表面被碳层包覆； 硅 元素与金属元素的重量比为 2： 3至 900： 1 ; 介孔硅颗粒的孔具有 2至 80 nm的尺寸分布。
2、 根据权利要求 1的复合物， 其特征在于， 硅元素与金属元素的重 量比为 2 : 1至 60 : 1。
3、 根据权利要求 1或 2的复合物， 其特征在于， 硅元素与金属元素 的重量比为 8 : 3至 12 : 1。
4、 根据权利要求 1至 3之一的复合物， 其特征在于， 所述金属硅化 物是 CoSi2。
5、 根据权利要求 1至 4之一的复合物， 其特征在于， 介孔硅颗粒内 部的孔具有 2至 50 nm的尺寸分布。
6、 根据权利要求 1至 5之一的复合物， 其特征在于， 所述碳层是通 过聚合物热解形成的。
7、 根据权利要求 6的复合物， 其特征在于， 所述聚合物选自 PVC、 沥青和 PAN, 或者上述的组合。
8、 根据权利要求 1至 5之一的复合物， 其特征在于， 所述碳层是通 过 CVD法形成的。
9、 根据权利要求 1至 8之一的复合物， 其特征在于， 所述介孔硅颗 粒中还嵌入有石墨或导电炭黑。
10、 根据权利要求 1的由介孔硅相、 金属硅化物相和碳相组成的介 孔硅复合物的制备方法， 该方法包括以下步骤：
1 ) 将 SiCl4、 LiSi合金粉和金属粉进行球磨；
2) 用水洗涤球磨的产品； 以及
3 ) 将步骤 2) 中经洗涤的产品包覆碳层， 从而获得所述介孔硅复合
11、 根据权利要求 10的方法， 其特征在于， 所述金属粉是钴粉。
12、 根据权利要求 1 的由介孔硅相、 金属硅化物相和碳相组成的介 孔硅复合物的制备方法， 该方法包括以下步骤：
1 ) 将 SiCl4和 LiSi合金粉进行球磨；
2) 用水洗涤球磨的产品；
3 ) 将步骤 2) 中经洗涤的产品加入金属氯化物的溶液中， 去除溶剂 后， 在含有氢气的还原性气氛中进行热还原， 以及
4) 将步骤 3 ) 的产品包覆碳层， 从而获得所述介孔硅复合物。
13、 根据权利要求 12的方法， 其特征在于， 所述金属氯化物是氯化 钴或其水合物。
14、 根据权利要求 10至 13之一的方法， 其特征在于， 基于初始原 料的总重量， 在步骤 1 ) 中还额外加入石墨或导电炭黑一起进行球磨。
15、 根据权利要求 10至 14之一的方法， 其特征在于， 在步骤 1 ) 中球磨之后对球磨的产品进行热处理。
16、 根据权利要求 10至 15之一的方法， 其特征在于， 所述包覆碳 层是通过将经洗涤的球磨产品加入聚合物溶液中， 然后进行热解而实现
17、 根据权利要求 16的方法， 其特征在于， 所述聚合物选自 PVC、 沥青和 PAN, 或者上述的组合。
18、 根据权利要求 10至 15之一的方法， 其特征在于， 所述包覆碳 层是通过 CVD法实现的。
19、 一种电极材料， 其特征在于， 所述电极材料中含有权利要求 1 至 9之一所述的或者根据权利要求 10至 18之一的方法制得的介孔硅复
20、 一种电池， 其特征在于， 所述电池中含有权利要求 1至 9之一 所述的或者根据权利要求 10至 18之一的方法制得的介孔硅复合物。
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