EP4146594A1 - Particules composites de silicium-carbone - Google Patents

Particules composites de silicium-carbone

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Publication number
EP4146594A1
EP4146594A1 EP21719617.9A EP21719617A EP4146594A1 EP 4146594 A1 EP4146594 A1 EP 4146594A1 EP 21719617 A EP21719617 A EP 21719617A EP 4146594 A1 EP4146594 A1 EP 4146594A1
Authority
EP
European Patent Office
Prior art keywords
silicon
carbon composite
composite particles
particles
lithium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21719617.9A
Other languages
German (de)
English (en)
Inventor
Alena KALYAKINA
Christoph DRÄGER
Claudia KLEINLEIN
Jürgen Pfeiffer
Jan TILLMANN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wacker Chemie AG
Original Assignee
Wacker Chemie AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wacker Chemie AG filed Critical Wacker Chemie AG
Publication of EP4146594A1 publication Critical patent/EP4146594A1/fr
Pending legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/30—Active carbon
    • C01B32/354—After-treatment
    • C01B32/372—Coating; Grafting; Microencapsulation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • 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
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
    • 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
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
    • C01B33/029—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by decomposition of monosilane
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/04—Coating on selected surface areas, e.g. using masks
    • C23C16/045—Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/24—Deposition of silicon only
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—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
    • H01M4/362—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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/14—Pore volume
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/002—Inorganic electrolyte
    • 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 silicon-carbon composite particles based on porous particles and silicon, methods for producing the silicon-carbon composite particles and their use as active materials in anodes for lithium-ion batteries.
  • lithium-ion batteries are currently the practical electrochemical energy storage devices with the highest energy densities.
  • Lithium-ion batteries are mainly used in the field of portable electronics, for tools and also for electrically powered means of transport such as bicycles, scooters or automobiles.
  • graphitic carbon is widely used as the active material for the negative electrode ("anode") of such batteries.
  • a disadvantage is the relatively low electrochemical capacity of such graphitic carbons, which is theoretically at most 372 mAh per gram of graphite and thus corresponds to only about a tenth of the electrochemical capacity that can theoretically be achieved with lithium metal.
  • Alternative active materials for the anode use an addition of silicon, as described in EP 3335262 B1, for example. Silicon forms binary electrochemically active alloys with lithium, which enable very high electrochemically achievable lithium contents of up to 4200 mAh per gram of silicon.
  • the lithium bound in it is no longer available to the system, which leads to a pronounced continuous loss of battery capacity.
  • the decrease in capacity over the course of several charging and discharging cycles is also referred to as fading or continuous loss of capacity and is usually irreversible.
  • silicon-carbon composite particles have been described as silicon-containing active materials for anodes of lithium-ion batteries.
  • silicon-carbon composite particles are obtained, for example, starting from gaseous or liquid silicon precursors by thermal decomposition thereof, with silicon being deposited in porous carbon particles.
  • US Pat. No. 10,147,950 B2 describes the deposition of silicon from monosilane SiH 4 in porous carbon particles in a tube furnace or comparable types of furnace at elevated temperatures of 300 to 900° C., preferably with movement of the particles by a CVD (chemical vapor deposition ") or PE-CVD process ("plasma-enhanced chemical vapor deposition").
  • the composites that can be obtained in this way also have cycle strengths that are not sufficient for use in demanding applications.
  • the task was to provide silicon-carbon composite particles which, when used as active material in anodes of lithium-ion batteries, have a very low initial and continuous loss of the lithium available in the cell and thus high Coulomb Enable efficiencies and high cycle stability through stable electrochemical behavior.
  • the fading should preferably be as small as possible.
  • silicon-carbon composite particles which have an alkali metal or alkaline earth metal concentration of 0.05-10% by weight and a pH>7.5.
  • silicon-carbon composite particles When used as active materials for lithium-ion batteries, such silicon-carbon composite particles have significantly increased cycle stability, and therefore lead to less fading.
  • silicon-carbon composite particles are produced by separating the silicon into porous carbon particles starting from gaseous or liquid silicon precursors analogously to the CVD process described above, a significantly increased reaction rate can be observed if the porous carbon already has a Alkaline or alkaline earth metal concentration of >0.1 to 20% by weight and a pH of >7.5.
  • the invention relates to silicon-carbon composite particles which a) an alkali metal or alkaline earth metal concentration of 0.05 to 10% by weight and b) a pH>7.5.
  • the porous carbon particles preferably have an alkali or alkaline earth metal concentration of 0.1 to 20% by weight, more preferably 0.2 to 10% by weight and most preferably 0.3 to 5% by weight .
  • the alkali or alkaline earth metal concentration of the porous carbon particles can be determined quantitatively by ICP emission spectroscopy, e.g. with the Optima 7300 DV measuring device from Perkin Elmer.
  • any method can be used to produce the silicon-carbon composite particles according to the invention.
  • the production by deposition of silicon from gaseous or liquid silicon precursors by infiltration into porous carbon particles analogous to the process described in US Pat. No. 10,147,950 B2 is a suitable access route to the silicon-carbon composite particles according to the invention.
  • the invention also relates to a method for producing the silicon-carbon composite particles according to the invention by silicon infiltration from silicon precursors which are selected from silicon precursors which are gaseous or liquid at 20° C. and 1013 mbar in the presence of porous carbon particles which have an alkali metal or alkaline earth metal concentration of 0.1 to 20% by weight and a pH of >7.5.
  • silicon is deposited in the pores and on the surface of the porous carbon particles.
  • silicon infiltration The deposition of silicon by thermal decomposition from gaseous or liquid silicon precursors in pores and on the surface of the porous carbon particles.
  • Porous carbon particles with an alkali metal or alkaline earth metal concentration of 0.1 to 20% and a pH of >7.5 can be obtained in any way known to those skilled in the art.
  • the porous carbon particles with an alkali or alkaline earth metal concentration of 0.1 to 20% and a pH of >7.5 are preferably obtained by treating porous carbon particles with basic alkali or alkaline earth metal compounds.
  • Preferred basic alkali or alkaline earth metal compounds are hydroxides, carbonates, hydrogen carbonates, percarbonates, amides, alcoholates, phenolates, alkylates, hydrides, alcides, silicates, disulfites, fluorides, cyanides, nitrites, peroxides, hyperoxides.
  • Hydroxides, carbonates, bicarbonates, percarbonates, hydrides, fluorides, amides are preferred, hydroxides, carbonates, bicarbonates, amides, hydrides, complex hydrides (tetrahydrometalates, for example BH 4 -, AIH 4 -, with eg Li, Na, K, Mg, Ca as counterion, eg LiBH 4 , NaBH 4 , Li 2 Zn (BH 4 ) 4 .), Most preferred are hydroxides, carbonates, bicarbonates.
  • the preferred basic alkali or alkaline earth metal compounds can be used alone or else as mixtures of different basic alkali and/or alkaline earth metal compounds.
  • the production of the porous carbon particles with an alkali or alkaline earth metal concentration of 0.1 to 20% and a pH of >7.5 can be obtained by treating the porous carbon particles with a solution of the basic alkali or alkaline earth metal compounds.
  • Preferred solvents include water and alcohols such as ethanol, Methanol, propanol or butanol, particular preference is given to water and ethanol, most
  • the porous carbon particles and the basic alkali metal or alkaline earth metal compounds can be used in any desired molar ratios, based on the carbon contained in the porous carbon particles.
  • the porous carbon particles and the basic alkali or alkaline earth metal compounds are preferably used in a molar ratio of 100:1 to 5:1, particularly preferably in a molar ratio of 50:1 to 5:1 and most preferably in a molar ratio of 20: 1 to 5:1, based on the carbon contained in the porous carbon particles, is used.
  • the treatment of the porous carbon particles with the basic alkali metal or alkaline earth metal compound can take place at temperatures below 20° C., above 20° C. or at 20° C., the treatment preferably takes place at elevated temperature.
  • the temperature during the treatment of the porous carbon particles with the basic alkali metal or alkaline earth metal compound is preferably between 30 and 200.degree. C., particularly preferably 50 to 160.degree. C. and very particularly preferably 70 to 120.degree.
  • the treatment of the porous carbon particles with the basic alkali metal or alkaline earth metal compound can be carried out under reduced pressure, normal pressure or elevated pressure.
  • the treatment preferably takes place at atmospheric pressure or elevated pressure of up to 5 bar, particularly preferably at atmospheric pressure.
  • the treatment of the porous carbon particles with the solution of the basic alkali metal or alkaline earth metal compound can take place in any reactor suitable for the treatment.
  • the treatment is carried out while stirring the suspension of the porous carbon particles in the solution of the basic alkali or alkaline earth metal compound or by spraying the porous carbon particles with a solution of the basic alkali or alkaline earth metal compounds.
  • the porous carbon particles are preferably freed from the solution of the basic alkali metal or alkaline earth metal compounds.
  • the treated porous carbon particles are cleaned of excess basic alkali metal or alkaline earth metal compound by washing with water.
  • the treated porous carbon particles can be obtained by evaporating the solvent for the basic alkali or alkaline earth compound.
  • the porous carbon particles are preferably dried.
  • the drying of the porous carbon particles can take place at an elevated temperature of 50 to 400° C. under an inert gas atmosphere in any reactor suitable for drying. Nitrogen or argon, for example, can be used as inert gases. Alternatively, drying can take place at an elevated temperature of 50 to 400° C. and a reduced pressure of 0.001 to 900 mbar. The drying time is preferably 0.1 second to 12 hours.
  • the porous carbon particles can be dried in the same reactor as the reaction with the gaseous or liquid silicon precursor or in a separate reactor suitable for drying.
  • the porous carbon particles preferably have a density, determined by helium pycnometry, of 0.1 to 4 g/cm 3 and particularly preferably of 0.3 to 3 g/cm 3 .
  • the porous carbon particles have a volume-weighted particle size distribution with diameter percentiles d 50 of preferably ⁇ 0.5 ⁇ m, more preferably ⁇ 1.5 ⁇ m and most preferably ⁇ 2 ⁇ m.
  • the diameter percentiles d 50 are preferably ⁇ 20 ⁇ m, more preferably ⁇ 12 ⁇ m and most preferably ⁇ 8 ⁇ m.
  • the volume-weighted particle size distribution of the porous carbon particles is preferably between the diameter Percentiles d 10 ⁇ 0.2 ⁇ m and d 90 ⁇ 20.0 ⁇ m, more preferably between d 10 ⁇ 0.4 ⁇ m and d 90 ⁇ 15.0 ⁇ m and most preferably between d 10 ⁇ 0.6 ⁇ m to d 90 ⁇ 12.0 ⁇ m.
  • the porous carbon particles have a volume-weighted particle size distribution with diameter percentiles d 10 of preferably ⁇ 10 ⁇ m, particularly preferably ⁇ 5 ⁇ m, particularly preferably ⁇ 3 ⁇ m and most preferably ⁇ 2 ⁇ m.
  • the diameter percentiles d 10 are preferably ⁇ 0.2 ⁇ m, more preferably ⁇ 0.4 and most preferably ⁇ 0.6 ⁇ m.
  • the porous carbon particles have a volume-weighted particle size distribution with diameter percentiles d 90 of preferably ⁇ 4 ⁇ m and particularly preferably ⁇ 8 ⁇ m.
  • the diameter percentiles d 90 are preferably ⁇ 20 ⁇ m, more preferably ⁇ 15 and most preferably ⁇ 12 ⁇ m.
  • the volume-weighted particle size distribution of the porous carbon particles has a width d 90 -d 10 of preferably ⁇ 15.0 ⁇ m, more preferably ⁇ 12.0 ⁇ m, particularly preferably ⁇ 10.0 ⁇ m, particularly preferably ⁇ 8.0 ⁇ m and most preferably ⁇ 4.0 ⁇ m.
  • the volume-weighted particle size distribution of the porous carbon particles has a width d 90 -d 10 of preferably ⁇ 0.6 ⁇ m, more preferably ⁇ 0.7 ⁇ m and most preferably ⁇ 1.0 ⁇ m.
  • the volume-weighted particle size distribution can be determined according to ISO 13320 by means of static laser scattering using the Mie model with the Horiba LA 950 measuring device with ethanol as the dispersing medium for the porous particles.
  • the porous carbon particles can be isolated or agglomerated, for example.
  • the porous carbon particles are preferably non-aggregated and preferably non-agglomerated.
  • Aggregated generally means that in the course of the production of the porous carbon particles, primary particles are first formed and grow together and/or primary particles are linked to one another, for example via covalent bonds and in this way form aggregates.
  • Primary particles are generally isolated particles.
  • Aggregates or isolated particles can form agglomerates.
  • Agglomerates are a loose aggregation of aggregates or primary particles that are linked to one another, for example, via van der Waals interactions or hydrogen bonds. Agglomerated aggregates can easily be split back into aggregates using common kneading and dispersing processes.
  • Aggregates cannot be broken down into the primary particles, or only partially, with these methods.
  • the presence of the porous particles in the form of aggregates, agglomerates or isolated particles can be made visible, for example, using conventional scanning electron microscopy (SEM).
  • SEM scanning electron microscopy
  • Static light scattering methods for determining particle size distributions or particle diameters of particles on the other hand, cannot differentiate between aggregates or agglomerates.
  • the porous carbon particles can have any morphology, that is, for example, be splintery, platy, spherical or needle-shaped, with splintery or spherical porous carbon particles being preferred.
  • the morphology can be characterized by the sphericity ⁇ or the sphericity S, for example.
  • the sphericity ⁇ is the ratio of the surface area of a sphere of equal volume to the actual surface area of a body. In the case of a sphere, ⁇ has the value 1.
  • the porous particles have a sphericity ⁇ of preferably from 0.3 to 1.0, more preferably from 0.5 to 1.0 and most preferably from 0.65 to 1, 0
  • the sphericity S is the ratio of the circumference of an equivalent circle with the same area A as the projection of the particle projected onto a surface and the measured circumference U of this projection: .
  • S would have the value 1.
  • the sphericity S is preferably in the range from 0.5 to 1.0 and particularly preferably from 0.65 to 1.0, based on the percentile S 10 to S 90 of the sphericity number distribution.
  • the sphericity S is measured, for example, using images of individual particles with an optical microscope or, in the case of particles ⁇ 10 ⁇ m, preferably with a scanning electron microscope by graphical evaluation using image analysis software such as ImageJ.
  • the porous carbon particles preferably have a gas-accessible pore volume of ⁇ 0.2 cm 3 /g, particularly preferably ⁇ 0.6 cm 3 /g and most preferably ⁇ 1.0 cm 3 /g. This is conducive to obtaining high-capacity lithium-ion batteries.
  • the gas-accessible pore volume is determined by gas adsorption measurements with nitrogen in accordance with DIN 66134.
  • the porous carbon particles are preferably open-pored.
  • Open-pore generally means that pores are connected to the surface of particles, for example via channels, and can preferably exchange material with the environment, in particular exchange gaseous compounds. This can be demonstrated using gas sorption measurements (analysis according to Brunauer, Emmett and Teller, "BET"), i.e. the specific surface area.
  • BET Brunauer, Emmett and Teller
  • the porous carbon particles have specific surface areas of preferably ⁇ 50 m 2 /g, more preferably ⁇ 500 m 2 /g and most preferably ⁇ 1000 m 2 /g.
  • the BET surface area is determined according to DIN 66131 (with nitrogen).
  • the pores of the porous carbon particles can have any diameter, ie generally in the range of macropores (>50 nm), mesopores (2 to 50 nm) and micropores ( ⁇ 2 nm).
  • the porous carbon particles can be used in any mixture of different pore types. Porous carbon particles with at most 30% macropores, based on the total pore volume, are preferably used, particularly preferably porous carbon particles without macropores and very particularly preferably porous carbon particles with at least 50% pores with an average pore diameter of less than 5 nm.
  • the porous carbon particles only have pores with a pore diameter of less than 2 nm (determination method: pore size distribution according to BJH (gas adsorption) according to DIN 66134 in the mesopore range and according to Horvath-Kawazoe (gas adsorption) according to DIN 66135 in the micropore range; the evaluation of the pore size distribution in the Macropore area is determined by mercury porosimetry according to DIN ISO 15901-1).
  • the porous carbon particles have a pH of preferably >7.5, preferably >8.5 and particularly preferably >9.
  • the pH of the porous carbon particles can be determined using ASTM Standard Number D1512, Method A.
  • the porous carbon particles have alkali metal or alkaline earth metal concentrations of 0.05 to 10% by weight, preferably 0.1 to 5% by weight and particularly preferably 0.15 to 2.5% by weight.
  • the silicon-carbon composite particles according to the invention have alkali metal or alkaline earth metal concentrations of from 0.05 to 10% by weight, preferably from 0.1 to 5% by weight and particularly preferably from 0.15 to 2.5% by weight. on.
  • the alkali or alkaline earth metal concentrations of the silicon-carbon composite particles according to the invention can be determined by means of ICP emission spectroscopy, e.g. with the Optima 7300 DV measuring device from Perkin Elmer.
  • the silicon-carbon composite particles according to the invention have pH values of >7.5, preferably >8.5 and most preferably >9.
  • the pH of the silicon-carbon composite particles of the present invention can be determined using ASTM Standard Number D1512, Method A.
  • the silicon-carbon composite particles according to the invention have a volume-weighted particle size distribution with diameter percentiles d 50 preferably in a range from 0.5 to 20 ⁇ m.
  • the d 50 value is preferably ⁇ 1.5 ⁇ m, and particularly preferably ⁇ 2 ⁇ m.
  • the diameter percentiles d 50 are preferably ⁇ 13 ⁇ m and particularly preferably ⁇ 8 ⁇ m.
  • the volume-weighted particle size distribution of the silicon-carbon composite particles according to the invention is preferably between the diameter percentiles d 10 ⁇ 0.2 ⁇ m and d 90 ⁇ 20.0 ⁇ m, particularly preferably between d 10 ⁇ 0.4 ⁇ m and d 90 ⁇ 15 .0 ⁇ m and most preferably between d 10 ⁇ 0.6 ⁇ m to d 90 ⁇ 12.0 ⁇ m.
  • the silicon-carbon composite particles according to the invention have a volume-weighted particle size distribution with diameter percentiles d 10 of preferably ⁇ 10 ⁇ m, particularly preferably ⁇ 5 ⁇ m, particularly preferably ⁇ 3 ⁇ m and most preferably ⁇ 1 ⁇ m.
  • the diameter percentiles d 10 are preferably ⁇ 0.2 ⁇ m, more preferably ⁇ 0.4 ⁇ m and most preferably ⁇ 0.6 ⁇ m.
  • the silicon-carbon composite particles according to the invention have a volume-weighted particle size distribution with diameter percentiles d 90 of preferably ⁇ 5 ⁇ m and particularly preferably ⁇ 10 ⁇ m.
  • the diameter percentiles d 90 are preferably ⁇ 20.0 ⁇ m, more preferably ⁇ 15.0 ⁇ m and most preferably ⁇ 12.0 ⁇ m.
  • the volume-weighted particle size distribution of the inventive silicon-carbon composite particles has a width d9o- d10 of preferably ⁇ 15.0 ⁇ m, particularly preferably ⁇ 12.0 ⁇ m, more preferably ⁇ 10.0 ⁇ m, particularly preferably ⁇ 8.0 ⁇ m and most preferably ⁇ 4.0 ⁇ m.
  • the volume-weighted particle size distribution of the silicon-carbon composite particles according to the invention has a width d 90 -d 10 of preferably ⁇ 0.6 ⁇ m, particularly preferably ⁇ 0.7 ⁇ m and most preferably ⁇ 1.0 ⁇ m.
  • the silicon-carbon composite particles according to the invention are preferably present in the form of particles.
  • the particles can be isolated or agglomerated.
  • the silicon-carbon composite particles according to the invention are preferably not aggregated and preferably not agglomerated.
  • isolated, agglomerated and non-aggregated are discussed above in Already defined in relation to the porous carbon particles.
  • the presence of silicon-carbon composite particles according to the invention in the form of aggregates or agglomerates can be made visible, for example, by means of conventional scanning electron microscopy (SEM).
  • the silicon-carbon composite particles according to the invention can have any morphology, ie for example splintery, plate-like, spherical or needle-like, with splintery or spherical particles being preferred.
  • the sphericity ⁇ is the ratio of the surface area of a sphere of equal volume to the actual surface area of a body. In the case of a sphere, ⁇ has the value 1.
  • the silicon-carbon composite particles according to the invention have a sphericity ⁇ of preferably 0.3 to 1.0, particularly preferably 0.5 to 1.0 and most preferably 0. 65 to 1.0.
  • the sphericity S is the ratio of the circumference of an equivalent circle with the same area A as the projection of the particle projected onto a surface and the measured circumference U of this projection: . In the case of an ideally circular particle, S would have the value 1.
  • the sphericity S is preferably in the range from 0.5 to 1.0 and particularly preferably from 0.65 to 1.0, based on the Percentiles S 10 to S 90 of the sphericity number distribution.
  • the sphericity S is measured, for example, using images of individual particles with an optical microscope or, in the case of particles ⁇ 10 ⁇ m, preferably with a scanning electron microscope, by graphical evaluation using image analysis software such as ImageJ.
  • the cycling stability of lithium-ion batteries can be further increased via the morphology, the material composition, in particular the specific surface area or the internal porosity of the silicon-carbon composite particles according to the invention.
  • the silicon-carbon composite particles according to the invention preferably contain 10 to 90% by weight, more preferably 20 to 80% by weight, particularly preferably 30 to 60% by weight and particularly preferably 40 to 50% by weight silicon obtained via the silicon infiltration, based on the total weight of the silicon-carbon composite particles according to the invention (determination preferably by means of elemental analysis, such as ICP-OES).
  • the volume of the silicon contained in the silicon-carbon composite particles according to the invention and obtained via the infiltration results from the mass fraction of the silicon obtained via the infiltration from the silicon precursor divided by the total mass of the silicon-carbon composite particles according to the invention by the density of silicon (2.336 g/cm 3 ).
  • the pore volume P of the silicon-carbon composite particles according to the invention results from the sum of gas-accessible and gas-inaccessible pore volumes.
  • the gas-accessible pore volume according to Gurvich of the silicon-carbon composite particles according to the invention can be determined by gas sorption measurements with nitrogen in accordance with DIN 66134.
  • the skeletal density is the density of the silicon-carbon composites determined by helium pycnometry according to DIN 66137-2
  • the pure material density of the silicon-carbon composite particles according to the invention is a theoretical density which is the sum of the theoretical pure material densities in the according to the invention Components contained in silicon-carbon composite particles, multiplied by their respective weight-related percentage of the total material, can be calculated.
  • This results for a silicon-carbon composite particle: Pure material density theoretical pure material density of silicon (2.336 g/cm 3 )*proportion of silicon in % by weight+density of the porous carbon particles (determined by helium pycnometry)*proportion of porous carbon particles in % by weight.
  • the pore volume P of the silicon-carbon composite particles according to the invention is preferably in the range from 0 to 400% by volume, more preferably in the range from 100 to 350% by volume and particularly preferably in the range from 200 to 350% by volume the volume of the silicon contained in the silicon-carbon composite particles according to the invention and obtained from the silicon infiltration.
  • the porosity contained in the silicon-carbon composite particles according to the invention can be both gas-accessible and gas-inaccessible.
  • the ratio of the volume of gas-accessible to gas-inaccessible porosity of the silicon-carbon composite particles according to the invention can generally be in the range from 0 (no gas-accessible pores) to 1 (all pores are gas-accessible).
  • the ratio of the volume of gas-accessible to gas-inaccessible porosity of the silicon-carbon composite particles according to the invention is preferably in the range from 0 to 0.8, particularly preferably in the range from 0 to 0.3 and particularly preferably from 0 to 0.1.
  • the pores of the silicon-carbon composite particles according to the invention can have any diameter, for example in the range of macropores (>50 nm), mesopores (2 to 50 nm) and micropores ( ⁇ 2 nm).
  • the silicon-carbon composite particles according to the invention can also contain any mixtures of different pore types.
  • the inventive silicon-carbon composite particles preferably contain at most 30% macropores, based on the total pore volume; inventive silicon-carbon composite particles without macropores are particularly preferred, and inventive silicon-carbon composite particles with them are very particularly preferred at least 50% pores with an average pore diameter of less than 5 nm. Carbon composite particles only have pores with a diameter of at most 2 nm.
  • the silicon-carbon composite particles according to the invention preferably have silicon structures which, in at least one dimension, have structure sizes of preferably at most 1000 nm, more preferably less than 100 nm, particularly preferably less than 5 nm (determination method: scanning electron microscopy (SEM) and/or High Resolution Transmission Electron Microscopy (HR-TEM)).
  • the silicon-carbon composite particles according to the invention preferably contain silicon layers in pores and on the outer surface with a layer thickness of at most 1000 nm, more preferably less than 100 nm, particularly preferably less than 5 nm (determination method: scanning electron microscopy (SEM ) and/or high-resolution transmission electron microscopy (HR-TEM)).
  • the silicon-carbon composite particles according to the invention can also contain silicon in the form of layers formed from silicon particles. Silicon particles have a diameter of preferably at most 1000 nm, more preferably less than 100 nm, particularly preferably less than 5 nm (determination method: scanning electron microscopy (SEM) and/or high-resolution transmission electron microscopy (HR -TEM)).
  • the information about the silicon particles here preferably relates to the diameter of the circumference of the particles in the microscope image.
  • the silicon-carbon composite particles according to the invention have a specific surface area of at most 100 m 2 /g, preferably less than 60 m 2 /g, and particularly preferably less than 20 m 2 /g.
  • the BET surface area is determined according to DIN 66131 (with nitrogen).
  • the silicon deposited from the silicon precursor may contain dopants in the silicon-containing material, for example selected from the group containing Fe, Al, Cu, S, Cl, Zr, Ti, Pt, Ni, Cr, Sn, Ag, Co, Zn, B, P, Sb, Pb, Ge, Bi, rare earths or combinations from it. Li and/or Sn are preferred.
  • the content of dopants in the material containing silicon-carbon composite particles is preferably at most 1% by weight and particularly preferably at most 100 ppm, based on the total weight of the silicon-carbon composite particles, determinable by ICP-OES.
  • the silicon-carbon composite particles according to the invention generally have a surprisingly high stability under pressure and/or shearing stress.
  • the pressure stability and the shear stability of the silicon-carbon composite particles according to the invention are shown, for example, by the fact that the silicon-carbon composite particles according to the invention under pressure (e.g. during electrode compaction) or stress (e.g. during electrode preparation). ) show little or no change in their porous structure in the SEM.
  • the silicon-carbon composite particles according to the invention can be produced in any reactors customary for silicon infiltration. Preference is given to reactors selected from fluidized-bed reactors, rotary kilns, which can be arranged in any arrangement, from horizontal to vertical, and fixed-bed reactors, which can be operated as open or closed systems, for example as pressure reactors. Particular preference is given to reactors which enable the porous particles and the silicon-containing material formed during the infiltration to be mixed homogeneously with the silicon precursors. This is advantageous for the most homogeneous possible deposition of silicon in pores and on the surface of the porous particles. Most preferred reactors are fluidized bed reactors, rotary kilns or pressure reactors, especially fluidized bed reactors or pressure reactors.
  • Silicon is generally deposited from the silicon precursors with thermal decomposition. It can for the silicon Infiltration, a silicon precursor or several silicon precursors can be used in a mixture or alternately.
  • Preferred silicon precursors are selected from silicon-hydrogen compounds such as monosilane SiH 4 , disilane Si 2 H 6 and higher linear, branched or cyclic homologues, neo-pentasilane Si 5 H 12 , cyclo-hexasilane Si 6 H 12 ; Chlorine-containing silanes, such as trichlorosilane HSiCl 3 , dichlorosilane H 2 SiCl 2 , chlorosilane H 3 SiCl, tetrachlorosilane SiCl 4 , hexachlorodilane Si 2 Cl 6 , and higher linear, branched or cyclic homologues such as 1,1, 2,2-tetrachlorodisilane Cl 2 HSi-SiHCl 2 ; chlorinated
  • silicon precursors are selected from monosilane SiH 4 , disilane Si 2 H 6 , chlorine-containing silanes, in particular trichlorosilane HSiCl 3 , dichlorosilane H 2 SiCl 2 , chlorosilane H 3 SiCl, tetrachlorosilane SiCl 4 , hexachlorodilane Si 2 Cl 6 and mixtures containing these silanes.
  • Monosilane is particularly preferred.
  • one or more reactive components can be introduced into the reactor.
  • these are dopants based on boron, nitrogen, phosphorus, arsenic, germanium, iron or compounds containing nickel.
  • the dopants are preferably selected from ammonia NH 3 , diborane B 2 H 6 , phosphine PH 3 , German GeH 4 , arsane AsH 3 and nickel tetracarbonyl Ni(CO) 4 .
  • reactive components are hydrogen or hydrocarbons, in particular selected from the group comprising aliphatic hydrocarbons having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, such as methane, ethane, propane, butane, pentane, isobutane, hexane, cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane; unsaturated hydrocarbons having 1 to 10 carbon atoms such as ethylene, acetylene, propylene or butylene; isoprene, butadiene, divinylbenzene, vinylacetylene, cyclohexadiene, cyclooctadiene; cyclic unsaturated hydrocarbons such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, cyclohexadiene, cyclopentadiene, dicyclopentad
  • the process is preferably carried out in an inert gas atmosphere, for example in a nitrogen or argon atmosphere.
  • the silicon infiltration is preferably carried out at 280 to 900.degree. C., particularly preferably at 320 to 600.degree. C., in particular at 350 to 450.degree.
  • the silicon infiltration can take place under reduced pressure, normal pressure or elevated pressure.
  • the treatment is preferably carried out at normal pressure or at elevated pressure of up to 50 bar.
  • the method can be carried out in a conventional manner, as is customary for the infiltration of silicon from silicon precursors, if necessary with routine adjustments customary to those skilled in the art.
  • Another object of the invention is an anode material for a lithium-ion battery, which contains the silicon-carbon composite particles according to the invention.
  • the anode material is preferably based on a mixture comprising the silicon-carbon composite particles according to the invention, one or more binders, optionally graphite as an additional active material, optionally one or more additional electrically conductive components and optionally one or more additives.
  • the anode material contains the silicon-carbon composite particles according to the invention, preferably one or more binders, optionally graphite as an additional active material, optionally one or more additional electrically conductive components and optionally one or more additives.
  • the contact resistances within the electrode and between the electrode and current collector can be reduced, which improves the current carrying capacity of the lithium-ion battery.
  • Preferred further electrically conductive components are conductive carbon black, carbon nanotubes or metallic particles, for example copper.
  • the primary particles of conductive carbon black can also be branched like chains and form structures up to ⁇ m in size.
  • Carbon nanotubes preferably have a diameter of 0.4 to 200 nm, more preferably 2 to 100 nm and most preferably 5 to 30 nm.
  • the anode material preferably contains 0 to 95% by weight, more preferably 0 to 40% by weight and most preferably 0 to 25% by weight of one or more other electrically conductive components, based on the total weight of the anode material.
  • the silicon-carbon composite particles according to the invention can be used in the anodes for lithium-ion batteries at preferably 5 to 100% by weight, particularly preferably 30 to 100% by weight and most preferably 60 to 100% by weight, based on the total active material contained in the anode material.
  • Preferred binders are polyacrylic acid or its alkali, especially lithium or sodium salts, polyvinyl alcohols, cellulose or cellulose derivatives, polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, polyimides, especially polyamide imide, or thermoplastic elastomers, especially ethylene-propylene-diene terpolymers .
  • Polyacrylic acid, polymethacrylic acid or cellulose derivatives, in particular carboxymethylcellulose are particularly preferred.
  • the alkali metal, in particular lithium or sodium, salts of the aforementioned binders are also particularly preferred.
  • the alkali metal salts, in particular lithium or sodium salts, of polyacrylic acid or polymethacrylic acid are most preferred. All or preferably a proportion of the acid groups of a binder can be present in the form of salts.
  • the binders have a molar mass of preferably 100,000 to 1,000,000 g/mol. Mixtures of two or more binders can also
  • Natural or synthetic graphite can generally be used as the graphite.
  • the graphite particles preferably have a volume-weighted particle size distribution between the diameter percentiles d 10 >0.2 ⁇ m and d 90 ⁇ 200 ⁇ m.
  • additives are pore formers, dispersants, leveling agents or dopants, for example elemental lithium.
  • Preferred formulations for the anode material contain preferably 5 to 95% by weight, in particular 60 to 90% by weight, of the silicon-carbon composite particles according to the invention; 0 to 90% by weight, in particular 0 to 40% by weight, of further electrically conductive components; 0 to 90% by weight, in particular 5 to 40% by weight, graphite; 0 to 25% by weight, in particular 5 to 20% by weight, of binder; and optionally 0 to 80 wt Add up wt%.
  • a further object of the invention is an anode which comprises a current conductor which is coated with the anode material according to the invention.
  • the anode is preferably used in lithium-ion batteries.
  • the components of the anode material can be processed into an anode ink or paste, for example, in a solvent, preferably selected from the group consisting of water, hexane, toluene, tetrahydrofuran, N-methylpyrrolidone, N-ethylpyrrolidone, acetone, ethyl acetate, dimethyl sulfoxide , dimethylacetamide and ethanol and mixtures of these solvents, preferably using rotor-stator machines, high-energy mills, planetary kneaders, agitator ball mills, vibrating plates or ultrasonic devices.
  • a solvent preferably selected from the group consisting of water, hexane, toluene, tetrahydrofuran, N-methylpyrrolidone, N-ethylpyrrolidone, acetone, ethyl acetate, dimethyl sulfoxide , dimethylacetamide and ethanol and mixture
  • the anode ink or paste has a pH value of preferably 2 to 10 (determined at 20° C., for example with the WTW pH 340i pH meter with SenTix RJD probe).
  • the anode ink or paste can be squeegeed onto a copper foil or other current collector, for example.
  • Other coating methods such as spin coating, roller, dip or slot coating, brushing or spraying can also be used in accordance with the invention.
  • the copper foil Before the copper foil is coated with the anode material according to the invention, the copper foil can be treated with a commercially available primer, for example based on polymer resins or silanes. Primers can lead to improved adhesion to the copper, but they generally have practically no electrochemical activity themselves.
  • the anode material is preferably dried to constant weight. The drying temperature depends on the components used and the solvent used. It is preferably between 20.degree. C. and 300.degree. C., particularly preferably between 50.degree. C. and 150.degree.
  • the layer thickness ie the dry layer thickness of the anode coating, is preferably from 2 ⁇ m to 500 ⁇ m, particularly preferably from 10 ⁇ m to 300 ⁇ m.
  • the electrode coatings can be calendered to set a defined porosity.
  • the electrodes produced in this way preferably have porosities of 15 to 85%, which can be determined by mercury porosimetry according to DIN ISO 15901-1. In this case, preferably 25 to 85% of the pore volume that can be determined in this way is provided by pores which have a pore diameter of 0.01 to 2 ⁇ m.
  • a further object of the invention is a lithium-ion battery comprising at least one anode which contains the silicon-carbon composite particles according to the invention.
  • the lithium-ion battery can also contain a cathode, two electrically conductive connections on the electrodes, a separator and an electrolyte with which the separator and the two electrodes are impregnated, and a housing that accommodates the parts mentioned.
  • lithium-ion battery also includes cells.
  • Cells generally include a cathode, an anode, a separator, and an electrolyte.
  • lithium-ion batteries preferably also contain a battery management system. Battery management systems are generally used to control batteries, for example by means of electronic circuits, in particular to identify the state of charge, for deep discharge protection or overcharging protection.
  • Lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide (doped or undoped), lithium manganese oxide (spinel), lithium nickel cobalt manganese oxides, lithium nickel manganese oxides, lithium iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium vanadium phosphate or lithium vanadium oxides can be used as preferred cathode materials.
  • the separator is preferably an electrically insulating membrane that is permeable to ions, preferably made of polyolefins, for example polyethylene (PE) or polypropylene (PP), or polyester or corresponding laminates.
  • the separator can alternatively consist of glass or ceramic materials or be coated therewith.
  • the separator separates the first electrode from the second electrode and thus prevents electronically conductive connections between the electrodes (short circuit).
  • Conductive salts are preferably selected from the group consisting of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium imides, lithium methides, LiCF 3 SO 3 , LiN(CF 3 SO 2 ) and lithium borates.
  • the concentration of the conductive salt, based on the solvent is preferably between 0.5 mol/l and the solubility limit of the salt in question. It is particularly preferably from 0.8 to 1.2 mol/l.
  • solvents examples include cyclic carbonates, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethoxyethane, diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, gamma-butyrolactone, dioxolane, acetonitrile, organic carbonic acid esters or nitriles, individually or as mixtures from it.
  • the electrolyte preferably contains a film former such as, for example, vinylene carbonate or fluoroethylene carbonate.
  • a film former such as, for example, vinylene carbonate or fluoroethylene carbonate.
  • SEI Solid Electrolyte Interphase
  • the SEI is particularly thin.
  • the lithium-ion battery according to the invention can be produced in all the usual forms, for example in a wound, folded or stacked form.
  • the silicon-carbon composite particles according to the invention are distinguished by significantly improved electrochemical behavior and lead to lithium-ion batteries with high volumetric capacities and outstanding application properties.
  • the silicon-carbon composite particles according to the invention are permeable to lithium ions and electrons and thus enable charge transport.
  • the amount of SEI in lithium ion batteries can be greatly reduced with the silicon-carbon composite particles of the present invention.
  • the SEI no longer detaches from the surface of the silicon-carbon composite particles according to the invention, or at least to a far lesser extent. All this leads to a high cycle stability of corresponding lithium ion batteries. Fading and trapping can be minimized.
  • lithium-ion batteries according to the invention show a low initial and continuous loss of lithium available in the cell and thus high Coulomb efficiencies.
  • pH values are determined according to ASTM standard number D1512, method A.
  • the microscopic investigations were carried out using a Zeiss Ultra 55 scanning electron microscope and an Oxford X-Max 80N energy-dispersive X-ray spectrometer.
  • the samples were coated with carbon before the investigation to prevent charging phenomena with a Safematic Compact Coating Unit 010/HV.
  • Cross-sections of the silicon-containing materials were generated with a Leica TIC 3X ion cutter at 6 kV.
  • the C contents were determined with a Leco CS 230 analyzer, for the determination of oxygen and nitrogen contents a Leco TCH-600 analyzer was used.
  • ICP inductively coupled plasma
  • Optima 7300 DV from Perkin Elmer
  • the samples were acidically digested (HF/HNO 3 ) in a microwave (Microwave 3000, Anton Paar).
  • the ICP-OES determination is based on ISO 11885 "Water quality - Determination of selected elements by inductively coupled plasma atomic emission spectrometry (ICP-OES) (ISO 11885:2007); German version EN ISO 11885:2009", which is used to analyze acidic, aqueous solutions (e.g. acidified drinking water, waste water and other water samples, aqua regia extracts from soil and sediments).
  • ISO 11885 Water quality - Determination of selected elements by inductively coupled plasma atomic emission spectrometry (ICP-OES) (ISO 11885:2007); German version EN ISO 11885:2009”, which is used to analyze acidic, aqueous solutions (e.g. acidified drinking water, waste water and other water samples, aqua regia extracts from soil and sediments).
  • the particle size distribution was determined according to ISO 13320 using static laser scattering with a Horiba LA 950.
  • special care must be taken to disperse the particles in the measurement solution so that the size of agglomerates is not measured instead of individual particles.
  • these were dispersed in ethanol. To do this, the dispersion before the measurement If necessary, treated for 4 minutes in a Hielscher ultrasonic laboratory device model UIS250v with sonotrode LS24d5 with 250 W ultrasound.
  • the specific surface area of the materials was measured by gas adsorption with nitrogen using a Sorptomatic 199090 (Porotec) or SA-9603MP (Horiba) device according to the BET method (determination according to DIN ISO 9277:2003-05 with nitrogen).
  • the skeletal density ie the density of the porous solid based on the volume excluding the pore spaces accessible to gas from the outside, was determined using helium pycnometry in accordance with DIN 66137-2.
  • the gas-accessible pore volume according to Gurvich was determined by gas sorption measurements with nitrogen in accordance with DIN 66134.
  • Comparative Example 1 Porous carbon particles with an alkali metal/alkaline earth metal concentration ⁇ 0.1% by weight and a pH ⁇ 7.5.
  • Porous carbon particles with the following properties were used:
  • Example 1 Treatment of porous carbon particles with 1 molar NaOH solution. 20 g of carbon from Comparative Example 1 were placed in a 250 ml flask, and 160 ml of 1M NaOH (aqueous solution) were added at room temperature. The suspension was then heated to 100°C and refluxed for 3 hours. After cooling to ambient temperature, the suspension was drained and washed with distilled water until the wash water had a pH of 7. The powder obtained in this way was finally dried at 80° C. overnight in a vacuum drying cabinet at 10 -2 bar. 19.6 g of a black solid were obtained.
  • Example 2 Treatment of porous carbon particles with 1 molar NaOH solution and an additional washing step.
  • Example 2 After treating the porous carbon particles as in Example 1, the sample was additionally washed with 2 L of distilled water. The powder obtained in this way was finally dried at 80° C. overnight in a vacuum drying cabinet at 10 -2 bar. 19.4 g of a black solid were obtained.
  • Example 3 Treatment of porous carbon particles with 1 molar NaOH solution at room temperature.
  • Example 4 Treatment of porous carbon particles with NaOH at room temperature without washing.
  • Example 5 Treatment of porous carbon particles with 1M LiOH at room temperature.
  • the suspension was suction filtered and washed with distilled water until the washing water had a pH of 7.
  • the powder obtained in this way was finally dried at 80° C. overnight in a vacuum drying cabinet at 10 -2 bar. 19.6 g of a black solid were obtained.
  • Example 6 Treatment of porous carbon particles with 1M KOH at room temperature.
  • Comparative Example 1A Silicon-carbon composite particles made from porous carbon particles from Comparative Example 1.
  • the reactive gas (10% SiH 4 in N 2 , 10 l (STP)/h
  • Comparative Example 1B Silicon-carbon composite particles made from porous carbon particles from Comparative Example 1 at reduced temperature.
  • Example 1A Silicon-carbon composite particles made from porous carbon particles from Example 1.
  • the reactive gas (10% SiH 4 in N 2 , 10 l (STP)/h
  • Example 2A Silicon-carbon composite particles made from porous carbon particles from Example 2.
  • the reactive gas (10% SiH 4 in N 2 , 10 l (STP)/h
  • Example 3A Silicon-carbon composite particles made from porous carbon particles from Example 3.
  • Example 4A Silicon-carbon composite particles made from porous carbon particles from Example 4.
  • the reactive gas (10% SiH 4 in N 2 , 10 l (STP)/h
  • Example 5A Silicon-carbon composite particles made from porous carbon particles from Example 5.
  • the reactive gas (10% SiH 4 in N 2 , 10 l (STP)/h
  • Example 6A Silicon-carbon composite particles made from porous carbon particles from Example 6.
  • the reactive gas (10% SiH 4 in N 2 , 10 l (STP)/h
  • Example 7A Silicon-carbon composite particles made from porous carbon particles from example 1 by reaction in a pressure reactor.
  • An electrically heated autoclave consisting of a cylindrical base (beaker) and a lid was used for the implementation with several connections (e.g. for gas supply, gas discharge, temperature and pressure measurement) with a volume of 594 ml.
  • the stirrer used was a helical stirrer that went almost all the way around the wall. This had a height that corresponded to about 50% of the clear height of the reactor interior.
  • the helical stirrer was designed in such a way that it allowed the temperature to be measured directly in the bed.
  • the autoclave was first evacuated. Then SiH 4 (15.6 g) was pressurized to 15.1 bar. The autoclave was then heated to a temperature of 425° C. within 90 minutes, and the temperature was maintained for 240 minutes. The pressure rose to 76 bar in the course of the reaction. The autoclave cooled down to room temperature (21 °C) within 12 hours. After cooling, a pressure of 35 bar remained on the autoclave. The pressure in the autoclave was reduced to 1 bar and then flushed five times with nitrogen, five times with lean air with an oxygen content of 5%, five times with lean air with an oxygen content of 10% and then five times with air. A 21.3 g quantity of silicon-carbon composite particles was isolated in the form of a black, fine solid. The reaction conditions for production and the material properties of the silicon-carbon composite particles are summarized in Table 2 below.
  • Example 8 Anode containing silicon-carbon composite particles according to the invention from example 1A and electrochemical testing in a lithium-ion battery.
  • the finished dispersion was then applied to a copper foil with a thickness of 0.03 mm (Schlenk metal foils, SE-Cu58) using a film drawing frame with a gap height of 0.1 mm (Erichsen, model 360).
  • the anode coating produced in this way was then dried for 60 minutes at 60° C. and 1 bar air pressure.
  • the middle The basis weight of the dry anode coating was 2.2 mg/cm 2 and the coating density was 0.8 g/cm 3 .
  • the electrochemical investigations were carried out on a button cell (type CR2032, Hohsen Corp.) in a 2-electrode arrangement.
  • a glass fiber filter paper (Whatman, GD Type D) saturated with 60 ⁇ l of electrolyte served as a separator (Dm 16 mm).
  • the electrolyte used consisted of a 1.0 molar solution of lithium hexafluorophosphate in a 1:4 (v/v) mixture of fluoroethylene carbonate and diethyl carbonate.
  • the cell was constructed in a glove box ( ⁇ 1 ppm H 2 O, O 2 ), the water content in the dry matter of all components used was below 20 ppm.
  • Electrochemical testing was performed at 22°C.
  • the cell was charged using the cc/cv method (constant current/constant voltage) with a constant current of 15 mA/g (corresponding to C/10) in the first cycle and 75 mA/g (corresponding to C/2) in the following cycles Cycles and after reaching the voltage limit of 4.2 V with constant voltage until the current falls below 1.5 mA/g (corresponds to C/100) or 3 mA/g (corresponds to C/50).
  • the cell was discharged using the cc method (constant current) with a constant current of 15 mA/g (corresponding to C/10) in the first cycle and 75 mA/g (corresponding to C/2) in the subsequent cycles until the voltage limit was reached of 2.5 V.
  • the specific current chosen was based on the weight of the positive electrode coating.
  • Example 9 Anode containing silicon-carbon composite particles according to the invention from example 5A and electrochemical testing in a lithium-ion battery.
  • An anode as described in example 8 was produced using the silicon-containing material according to the invention from example 5A.
  • the anode was built into a lithium-ion battery as described in Example 8 and subjected to testing using the same procedure.
  • Example 10 Anode Containing Silicon-Carbon Composite Particles According to the Invention from Example 6A and Electrochemical Testing in a Lithium-Ion Battery.
  • An anode as described in example 8 was produced using silicon-carbon composite particles according to the invention from example 6A.
  • the anode was built into a lithium-ion battery as described in Example 8 and subjected to testing using the same procedure.
  • Comparative Example 11 Anode Containing Silicon-Carbon Composite Particles Comparative Example 1A and Electrochemical Testing in a Lithium-Ion Battery.
  • Example 8 An anode as described in Example 8 was produced using the silicon-containing material from Comparative Example 1A that was not according to the invention. The anode was built into a lithium-ion battery as described in Example 8 and tested using the same procedure. The results from the electrochemical evaluations are summarized in Table 3 below.

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Abstract

L'invention concerne des particules composites de silicium-carbone ayant a) une concentration en métal alcalin ou alcalino-terreux de 0,05 à 10 % en poids et b) un pH > 7,5 ; un procédé pour leur préparation par infiltration de silicium à partir de précurseurs de silicium en présence de particules de carbone poreuses ; un matériau d'anode pour une batterie au lithium-ion contenant lesdites particules composites de silicium-carbone ; une anode comprenant un conducteur de courant revêtu dudit matériau d'anode ; et une batterie au lithium-ion comprenant au moins une anode qui contient lesdites particules composites de silicium-carbone.
EP21719617.9A 2021-04-16 2021-04-16 Particules composites de silicium-carbone Pending EP4146594A1 (fr)

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