Classifications

• • 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
  • 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
  • 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
  • H01M4/04—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
  • H01M4/362—Composites
• • 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
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/027—Negative electrodes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the invention relates to redispersible particles based on silicon particles and polymers, to processes for their preparation and to their use for producing electrode materials for lithium-ion batteries, in particular for producing the negative electrodes of lithium-ion batteries.
• Rechargeable lithium ion batteries are today the most practical electrochemical energy storage devices with the highest gravimetric energy densities.
• a particularly high theoretical material capacity has silicon (4200 mAh / g) and is therefore particularly suitable as an active material for anodes of lithium-ion batteries.
• the production of anodes takes place via anode inks in which the individual components of the anode material are dispersed in a solvent. On an industrial scale, water is mostly used as the solvent for economic and ecological reasons.
• Touidjine Journal of The Electrochemical Society, 2015, 162, pages A1466 to A1475) first teaches the surface of the silicon particles by pretreatment
• Touidjine describes aggregated Silicon particles with average particle sizes of 150 nm and specific surface BET of 14 m 2 / g. After air oxidation, the silicon particles have a Si0 2 content of 11% by weight. The high oxygen content of the particles inevitably leads to a low proportion of elemental silicon. Such high levels of silica lead to high initial capacity losses.
• K. Zaghib, Hydro-Quebec presented in a lecture (DoE Annual Merit Review, June 6-10, 2016, Washington DC USA, Post es222) a number of alternative approaches to reducing the formation of hydrogen from aqueous Si. licium particulate dispersions for discussion, such as coating the surfaces of the silicon particles, or adding pH controlling additives, or oxidizing the surface of the silicon particles, or aging the silicon particles.
• Lithium ion batteries with silicon particles containing anode materials are also known from EP1313158.
• the silicon particles of EP1313158 have average particle sizes of 100 to 500 nm. Larger particle sizes are considered detrimental to the Coulomb efficiency of corresponding batteries.
• the preparation of the particles was carried out by grinding and subsequent oxidative treatment with oxygen-containing gases or subsequent coating with polymers.
• EP1313158 also recommends polymerizing ethylenically unsaturated monomers in the presence of silicon particles.
• DE102015215415.7 (application number) describes the use of silicon particles having a volume-weighted particle size distribution of dio ⁇ 0.2 ⁇ m and d 90 ⁇ 20.0 pm and a width c o-dio ⁇ 15 pm in anode materials for lithium-ion batteries.
• the object of the present invention was to provide silicon particles which, when used in aqueous ink formulations for producing anodes for lithium-ion batteries, are none or as small as possible Hydrogen formation lead, in particular no foaming of aqueous ink formulations or poor pumpability of the inks cause, and also allow the advantageous introduction of the highest possible silicon content in the anodes and should give as homogeneous anode coatings.
• the task should preferably also be solved for ink formulations with neutral pH values.
• an improvement in the electrochemical performance of corresponding lithium ion batteries with silicon particles containing anodes should be achieved.
• An object of the invention are processes for the preparation of redispersible particles based on silicon particles and polymers, characterized in that
• a thermal treatment is carried out at a temperature of 80 ° C to below the decomposition temperature of the polymers.
• Another object of the invention are redispersible
• Particles based on silicon particles and polymers obtainable by the abovementioned process according to the invention.
• the redispersible particles from step b) of the process according to the invention are generally polymer-coated silicon particles.
• the polymers are advantageously bonded to the silicon particles. This is manifested, for example, in the fact that the particles obtained in step b) are stable after redispersion in water at room temperature and pH 7 and essentially release no polymers.
• the products from step b) can therefore also be classified as being wash-off-stable.
• the drying products from step a) completely or at least partly into their starting components, namely silicon particles and polymers. Without being bound by theory, such attachment could be via covalent bonds between the polymers and the surface of the silicon particles, for example through silyl ester bonds or through crosslinking of the polymers.
• the polymers preferably contain one or more functional groups selected from the group comprising carboxyl and hydroxyl groups. Most preferred are carboxyl groups.
• Preferred polymers are cellulose, cellulose derivatives, polymers based on ethylenically unsaturated monomers, such as polyacrylic acid or polyvinyl esters, in particular homo- or copolymers of vinyl acetate, polyamides, polyimides, in particular polyamido-imides, and polyvinyl alcohols.
• Particularly preferred polymers are polyacrylic acid or its salts and in particular cellulose or cellulose derivatives, such as carboxymethylcellulose. Most preferred are cellulose or cellulose derivatives, especially carboxymethylcellulose.
• salts of carboxylic acid group-carrying polymers are alkali metal, in particular lithium, sodium or potassium salts.
• the polymers containing functional groups are preferably soluble in the solvents.
• the polymers are therein soluble under normal conditions (23/50) according to DIN50014, preferably to more than 5 wt .-%.
• the mixtures in step a) preferably contain ⁇ 95% by weight, more preferably 50% by weight, even more preferably 35% by weight, more preferably 20% by weight, most preferably 10% by weight and most preferably preferably ⁇ 5% by weight of polymers.
• the mixtures in step a) preferably comprise ⁇ 0.05% by weight, more preferably ⁇ 0.3% by weight and most preferably ⁇ 1% by weight of polymers.
• the above-mentioned data in% by weight relate in each case to the dry weight of the mixtures in step a).
• the volume-weighted particle size distribution of the silicon particles has diameter percentiles d 50 of preferably 650 nm to 15.0 ⁇ m, more preferably 700 nm to 10.0 ⁇ m, even more preferably 700 nm to 7.0 ⁇ m, particularly preferably 750 nm to 5 , 0 pm, and most preferably 800 nm to 2.0 pm.
• the volume-weighted particle size distribution of the silicon particles has diameter percentiles di 0 of preferably 0.5 ⁇ m to 10 ⁇ m, particularly preferably 0.5 ⁇ m to 3.0 ⁇ m and most preferably 0.5 ⁇ m to 1.5 ⁇ m.
• the volume-weighted particle size distribution of the silicon particles has diameter percentiles d 90 of preferably 2.0 ⁇ m to 20.0 ⁇ m, particularly preferably 3.0 to 15.0 ⁇ m and most preferably 5.0 ⁇ m to 10.0 ⁇ m.
• the volume-weighted particle size distribution of the silicon particles has a width d 90 -d 10 of preferably 20 20.0 ⁇ m, more preferably ⁇ 15.0 ⁇ m, even more preferably 12 12.0 ⁇ m, more preferably 10 10.0 ⁇ m and most preferably ⁇ 7.0 pm.
• the volume-weighted particle size distribution of the silicon particles can be determined by static laser scattering using the Mie model with the Horiba LA 950 measuring instrument with alcohols, for example ethanol or isopropanol, or preferably water as dispersing medium for the silicon particles.
• the silicon particles are preferably not agglomerated, more preferably not aggregated.
• Aggregated means that spherical or largely spherical primary particles, such as those initially formed in gas phase processes during the production of the silicon particles, have grown together into aggregates.
• the aggregation of primary particles may occur during the production of the silicon particles in gas phase processes.
• Such aggregates can form agglomerates in the further course of the reaction.
• Agglomerates are a loose aggregate of aggregates. Agglomerates can be easily split again into the aggregates using typically used kneading and dispersing processes. Aggregates can not be decomposed with these methods or only to a small extent into the primary particles. Due to their formation, aggregates and agglomerates inevitably have completely different sphericities and grain shapes than the preferred silicon particles.
• the presence of silicon particles in the form of aggregates or agglomerates can be made visible for example by means of conventional scanning electron microscopy (SEM). By contrast, static light scattering methods for determining the particle size distributions or particle diameters of silicon particles can not distinguish between aggregates or agglomerates.
• the BET surface areas of the silicon particles are preferably 0.2 to 30.0 m 2 / g, more preferably 0.5 to 20.0 m 2 / g, and most preferably 1.0 to 15.0 m 2 / g.
• the BET surface area is determined according to DIN 66131 (with nitrogen).
• the silicon particles are preferably in splintered grain forms.
• the silicon particles have a Sph riztician of preferably 0.3 ⁇ ⁇ ⁇ 0.9, more preferably 0.5 ⁇ ⁇ ⁇ 0.85 and most preferably 0.65 ⁇ ⁇ ⁇ 0.85. Silicon particles with such sphericity are accessible in particular by production by means of grinding processes. Sphericity ⁇ is the ratio of the surface of a sphere of equal volume to the actual surface of a body (Wadell's definition). Sphericities can be determined, for example, from conventional SEM images.
• the silicon particles are preferably based on elemental silicon. Under elemental silicon is high-purity, polycrystalline silicon, with a low proportion of foreign atoms (such as B, P, As), targeted doped with impurity silicon (such as B, P, As), but also silicon from metallurgical processing, elemental Contamination (such as Fe, Al, Ca, Cu, Zr, Sn, Co, Ni, Cr, Ti, C) may have to understand. If the silicon particles contain a silicon oxide, then the stoichiometry of the oxide SiO x is preferably in the range 0 ⁇ x ⁇ 1.3. If the silicon particles contain a silicon oxide with a higher stoichiometry, then its layer thickness on the surface is preferably less than 10 nm.
• the stoichiometry of the alloy M y Si is preferably in the range 0 ⁇ y ⁇ 5.
• the silicon particles may optionally be prelithiated.
• the stoichiometry of the alloy Li z Si is preferably in the range 0 ⁇ z ⁇ 2.2.
• silicon particles which contain 80 80 mol% silicon and / or 20 20 mol% foreign atoms, very particularly preferably 10 10 mol% foreign atoms.
• the surface of the silicon particles may optionally be covered by an oxide layer or by other inorganic and organic groups.
• Particularly preferred silicon particles carry on the surface Si-OH or Si-H groups or covalently attached organic groups, such as, for example, alcohols or alkanes.
• the surface tension of the silicon particles can be controlled by the organic groups. This can be adapted to the solvents or polymers used in the preparation of the redispersible particles or in the production of electrode coatings.
• Correspondingly coated surfaces of the silicon particles may be helpful in linking the polymers and the silicon particles to more stable, redispersible particles according to the invention.
• the silicon particles can be produced, for example, by gas phase separation or preferably by milling processes.
• milling processes for example, dry or preferably wet grinding processes come into consideration.
• jet mills such as counter-jet or impact mills, or stirred ball mills are used.
• the wet grinding is generally carried out in a suspension with organic or inorganic dispersing media.
• the dispersants which may also be used are the solvents mentioned for stage a).
• the mixtures in step a) preferably contain ⁇ 5 wt%, more preferably ⁇ 50 wt%, even more preferably ⁇ 65 wt%, more preferably ⁇ 80 wt%, most preferably ⁇ 90 wt%, and most preferably preferably ⁇ 95% by weight of silicon particles.
• the mixtures in step a) preferably contain 99.95% by weight, more preferably 99.7% by weight and most preferably 99% by weight of silicon particles.
• the above-mentioned data in% by weight relate in each case to the dry weight of the mixtures in step a).
• organic and / or inorganic solvents can be used. It can also be used Ge ⁇ mix of two or more solvents.
• An example of an inorganic solvent is water.
• Organic solvents are, for example, hydrocarbons, esters or, preferably, alcohols.
• the alcohols preferably contain 1 to 7 and more preferably 2 to 5 carbon atoms. Examples of alcohols are methanol, ethanol, propanol, butanol and benzyl alcohol. Preference is given to ethanol and 2-propanol.
• Hydrocarbons preferably contain 5 to 10 and more preferably 6 to 8 carbon atoms. Hydrocarbons may be, for example, aliphatic or aromatic. Examples of hydrocarbons are toluene and heptane.
• Esters are generally esters of carboxylic acids and alkyl alcohols, such as ethyl acetate.
• Preferred solvents are water or mixtures of water and one or more organic solvents, in particular all alcohols.
• Preferred solvent mixtures contain water to preferably 10 to 90% by weight, more preferably 30 to 80% by weight and most preferably 50 to 70% by weight.
• Preferred solvent mixtures contain preferably from 10 to 90% by weight, more preferably from 20 to 70% by weight, and most preferably from 30 to 50% by weight of organic solvents, in particular alcohols.
• the abovementioned data in% by weight relate in each case to the total weight of the solvents in the mixtures in step a).
• the mixtures in step a) preferably contain 10 10% by weight, more preferably 30 30% by weight, more preferably 50 50% by weight and most preferably 70 70% by weight of solvent.
• the mixtures in step a) preferably contain 99 99.8% by weight, more preferably ⁇ 95% by weight and most preferably 90 90% by weight of solvent.
• the above-mentioned data in% by weight relate in each case to the total weight of the mixtures in step a).
• one or more binders may optionally be used in addition.
• binders are polyalkylene oxides, such as polyethylene glycol, polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, or thermoplastic elastomers, in particular ethylene-propylene-diene terpolymers.
• polyalkylene oxides such as polyethylene glycol, polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, or thermoplastic elastomers, in particular ethylene-propylene-diene terpolymers.
• the proportion of such binders is preferably 30% by weight and more preferably 10% by weight, based on the total weight of polymers and binders in step a). Most preferably, no binders are used in addition.
• the mixtures in step a) may additionally contain one or more electrically conductive components and / or one or more additives.
• electrically conductive components are graphite particles, Leitruß, carbon nanotubes or metallic particles, such as copper particles.
• electrically conductive components are graphite particles, Leitruß, carbon nanotubes or metallic particles, such as copper particles.
• the mixtures in step a) no electrically conductive components, in particular no graphite.
• additives are pore formers, leveling agents, dopants or substances which improve the electrochemical stability of the electrode in the battery.
• the mixtures in step a) preferably contain 0 to 30% by weight, more preferably 0.01 to 15% by weight and most preferably 0.1 to 5% by weight of additives, based on the dry weight of the mixtures in step a ).
• the mixtures in step a) contain no additives.
• the preparation of the mixtures for step a) can be carried out by mixing their individual constituents and is not bound to any particular procedure.
• silicon particles, polymers and solvents as well as optional further components can be mixed in any order.
• the silicon particles and / or the polymers can be used for mixing in pure form or preferably in one or more solvents.
• the silicon particles are preferably used in the form of dispersions, in particular alcoholic dispersions.
• the polymers are preferably used in the form of solutions, in particular in the form of aqueous solutions.
• silicon particles in the form of dispersions and / or polymers in the form of solutions it is also possible to add further solvents or additional amounts of solvent.
• the polymers, if appropriate dissolved or dispersed in solvents, can also be added to a suspension containing silicon particles before, during or after the grinding, in particular the wet milling.
• the mixing can be carried out in common mixing devices, for example in rotor-stator machines, high-energy mills, planetary kneaders, stirred ball mills, vibrating plates, dissolvers, rolling benches or ultrasonic devices.
• the mixtures used for drying in step a) are in an advantageous embodiment of the invention in a flowable state.
• the mixtures to be dried have a pH of preferably ⁇ 7 (determined at 20 ° C, for example with the pH meter of WTW pH 340i with probe SenTix RJD).
• Drying in step a) can take place, for example, by means of fluidized-bed drying, freeze drying, thermal drying, drying in vacuo, contact drying, convection drying or by means of spray drying.
• the vacuum contact drying more preferably the spray drying. It can be used for this common facilities and conditions application.
• the drying can be carried out in ambient air, synthetic air, oxygen or preferably in an inert gas atmosphere, for example in a nitrogen or argon atmosphere. Generally, it is dried at atmospheric pressure or at reduced pressure.
• the drying is generally carried out at temperatures of ⁇ 400 ° C, preferably ⁇ 200 ° C and more preferably ⁇ 150 ° C. In a preferred embodiment, the drying takes place at temperatures of -60 ° C to 200 ° C.
• the freeze-drying is generally carried out at temperatures below the freezing point of the mixture to be dried, preferably at temperatures in the range of -120 ° C to 0 ° C and more preferably at -20 ° C to -60 ° C.
• the pressure is preferably between 0.005 and 0.1 mbar.
• the drying under vacuum is preferably carried out at temperatures from 40 ° C to 100 ° C and pressures of from 1 up to 10 "3 mbar, insbesonde ⁇ re 100 to 10 3 mbar.
• the spray drying can be effected, for example, in Sprühtrocknungsanla ⁇ gene in which the atomization means Single-fluid, two-fluid or multi-fluid nozzles or with a rotating disk, the inlet temperature of the mixture to be dried into the spray Trocknungsanläge is preferably greater than or equal to the boiling point of the mixture to be dried and more preferably by ⁇ 10 ° C higher than the boiling temperature of the mixture to be dried.
• the inlet temperature is preferably 80 ° C to 200 ° C, more preferably 100 ° C to 150 ° C.
• the exit temperature is preferably 30 ° C, more preferably ⁇ 40 ° C, and most preferably ⁇ 50 ° C. In general, the exit temperature is in the range of 30 ° C to 100 ° C, preferably 45 ° C to 90 ° C.
• the pressure in the spray drying plant is preferably the ambient pressure. In the spray-drying plant, the sprayed mixtures have primary droplet sizes of preferably 1 to 1000 ⁇ m, particularly preferably 2 to 600 ⁇ m and most preferably 5 to 300 ⁇ m.
• the settings of the inlet temperature, the gas flow, as well as the feed rate, the choice of the nozzle, the aspirator, the choice of solvent or the solids concentration of the spray suspension can be used to determine the size of the primary particles, residual moisture in the water Adjust the product and the yield of the product in a conventional manner. For example, at a higher solids concentration of the spray suspension, primary particles having larger particle sizes are obtained, whereas a higher spray gas flow leads to smaller particle sizes.
• ⁇ In the other drying methods is preferably at temperatures from 0 ° C to 200 ° C, more preferably dried at 10 ° C to 180 ° C and most preferably at 30 ° C to 150 ° C.
• the pressure in the other drying processes is preferably 0.5 to 1.5 bar.
• the drying can be carried out, for example, by contact with hot surfaces, convection or radiation heat. Preferred dryers for the others
• Drying processes include fluidized bed dryers, screw dryers, paddle dryers and extruders.
• the mixtures from step a) are generally substantially freed of solvent.
• the products obtained in step a) after drying have preferably contained 10% by weight, more preferably 5% by weight, even more preferably 3% by weight and most preferably 1% by weight of solvent solution. average, based on the total weight of the drying products from step a).
• the products from step a) are preferably redispersible particles, in particular water-redispersible particles.
• the drying products from step a) generally decompose again into their starting constituents, in particular into silicon particles and the polymers used according to the invention.
• the particles obtained in step a) are generally not coated with carbon.
• the silicon particles absorb oxygen (determined as indicated below under the heading "Determination of Oxygen Content.")
• the silicon particles contained in the drying product of step a) have substantially the same Oxygen content as the silicon particles used in step a) for drying.
• step b) The products from step a) are preferably used directly in step b).
• Step b) may also follow directly to step a).
• the particles from step a) are therefore preferably not treated further before introduction in step b).
• the thermal treatment in step b) takes place at a temperature below the decomposition temperature of the polymers.
• the decomposition temperature refers to the temperature above which a polymer changes as a result of thermal decomposition in its chemical structure, for example by cleavage of small molecules such as water or carbon dioxide.
• the decomposition can be indexed, for example, in a conventional manner by means of thermogravimetric analysis (TGA).
• the temperature for the thermal treatment is preferably 90 90 ° C, more preferably> 100 ° C, and most preferably 110 110 ° C.
• the aforesaid temperature is preferably 250 250 ° C, more preferably 220 220 ° C, more preferably 200 200 ° C, even more preferably 180 180 ° C, and most preferably 160 160 ° C.
• the thermal treatment in step b) can be carried out in ambient air, synthetic air, oxygen or in an inert gas atmosphere, for example in a nitrogen or argon atmosphere. Preference is given to air.
• Step b) can be carried out under any pressure. Preference is given to working at a pressure of 0.5 to 2 bar, in particular 0.8 to 1.5 bar. Particularly preferred is thermally treated at ambient pressure.
• the duration of the thermal treatment may be, for example, 1 minute to 48 hours, preferably 5 minutes to 30 hours, more preferably 10 minutes to 24 hours, and even more preferably 30 minutes to 16 hours.
• the thermal treatment can be operated continuously or discontinuously.
• the duration of the thermal treatment is preferably 1 minute to 6 hours and more preferably 5 minutes to 2 hours.
• the duration is preferably 1 to 48 hours, more preferably 6 to 30 hours, and most preferably 12 to 24 hours.
• the thermal treatment can be carried out in conventional reactors, for example in a calcination furnace, tube furnace, in particular a rotary kiln, fluidized bed reactor, fluidized bed reactor or a drying oven. Particularly preferred are calcination furnaces, fluidized bed reactors and rotary kilns.
• Step b) is preferably carried out in the absence of liquids, such as solvents, in particular in the absence of water or alcohols in liquid form.
• the redispersible particles from step b) are preferably redispersible in water.
• the redispersible particles from step b) are preferably not agglomerated, in particular preferably not aggregated.
• the redispersible particles obtained in step b) are generally not coated with carbon.
• the volume-weighted particle size distribution of the redispersible particles from step b) can be determined by static laser scattering using the Mie model with the Horiba LA 950 measuring instrument with alcohols, for example ethanol or isopropanol, or preferably water as dispersing medium for the redispersible silicon particles.
• the thus determined particle size distribution preferably take the following values for the diameter percentiles d 50 , d i0 , d 90 and d 90 - dio.
• the volume-weighted particle size distribution of the redispersible particles from step b) has diameter percentiles d 50 of preferably 650 nm to 15.0 ⁇ m, more preferably 700 nm to 10.0 ⁇ m, even more preferably 700 nm to 7 . 0 ⁇ , more preferably 750 nm to 5.0 ⁇ and most preferably 800 nm to
• the volume-weighted particle size distribution of the redispersible particles from step b) has diameter percentiles d 10 of preferably 0.5 ⁇ to 10 ⁇ , more preferably 0.5 ⁇ to 3.0 ⁇ and most preferably 0.5 ⁇ to 1.5 ⁇ on.
• the volume-weighted particle size distribution of the redispersible particles from step b) has diameter percentiles d 90 of preferably 2.0 ⁇ m to 20.0 ⁇ m, more preferably 3.0 to 15.0 ⁇ m and most preferably 5.0 ⁇ m to 10.0 ⁇ on.
• the volume-weighted particle size distribution of the redispersible particles from step b) has a width d 90 -di 0 of preferably 20 20.0 ⁇ m, more preferably 15,0 15.0 ⁇ m, even more preferably 12 12.0 ⁇ m, particularly preferably 10 10, 0 pm, and most preferably ⁇ 7.0 pm.
• the BET surface areas of the silicon particles are preferably 0.2 to 30.0 m 2 / g, more preferably 0.5 to 20.0 m 2 / g, and most preferably 1.0 to 15.0 m 2 / g.
• the BET surface area is determined according to DIN 66131 (with nitrogen).
• the redispersible particles from step b) are preferably in splintered grain forms.
• the redispersible particles from step b) have a sphericity of preferably 0.3-9.0.9, more preferably 0.5-8.8, and most preferably 0.65-0.85.
• Sphericity ⁇ is the ratio of the surface of a sphere of equal volume to the actual surface of a body (Wadell's definition). Sphericities can be determined, for example, from conventional SEM images.
• the redispersible particles from step b) preferably contain from 50 to 99.7% by weight, more preferably from 80 to 99.5% by weight, particularly preferably from 90 to 99% by weight and most preferably from 95 to 98.5% by weight of silicon particles ; and preferably 0.3 to 50% by weight, more preferably 0.5 to 20% by weight, particularly preferably 1 to 10% by weight, and most preferably 1.5 to 5% by weight of polymers; wherein the data in% by weight relate in each case to the total weight of the redispersible particles.
• the silicon particles of the redispersible particles of step b) preferably contain 0.2 to 6.0% by weight, particularly preferably 1.0 to 4.0% by weight of oxygen, based on the weight of the silicon particles of the redispersible particles of step b).
• the products of step b) have a preferably 0 to 1 wt .-%, particularly preferably 0.15 to 0.5 wt .-% and most preferably 0.2 to 0 compared to the products of step a, 4% by weight lower content of carbon, based on the total weight of the products (determined as indicated below under the heading "Determination of carbon content").
• Another object of the invention are aqueous ink formulations containing one or more binders, given if graphite, optionally one or more further electrically conductive components and optionally one or more additives, characterized in that redispersible particles from step b) of the inventive method are included.
• Another object of the invention are anode materials for lithium-ion batteries containing one or more binders, optionally graphite, optionally one or more further electrically conductive components and optionally one or more additives, characterized in that one or more redispersible particles from step b) of the method according to the invention are included.
• Preferred formulations for the anode material of the lithium-ion batteries preferably contain from 5 to 95% by weight, in particular from 60 to 85% by weight, of redispersible particles from step b) of the process according to the invention; 0 to 40 wt .-%, in particular 0 to 20 wt .-% further electrically conductive components; 0 to 80 wt .-%, in particular 5 to 30 wt .-% graphite; 0 to 25 wt .-%, preferably 1 to 20 wt .-%, particularly preferably 5 to 15 wt .-% binder; and optionally from 0 to 80% by weight, in particular from 0.1 to 5% by weight, of additives; wherein the data in wt .-% on the total weight of the anode material and the proportions of all components of the anode material add up to 100 wt .-%.
• the proportion of graphite particles and other electrically conductive components in total is at least 10 wt .-%, based on the total weight of the anode material.
• the anode ink has a pH of preferably 5.5 to 8.5 and particularly preferably 6.5 to 7.5 (determined at 20 ° C., for example with the pH meter of WTW pH 340i with probe Sen-Tix RJD ).
• Another object of the invention are lithium-ion batteries comprising a cathode, an anode, a separator and an electrolyte, characterized in that the anode is based on the aforementioned anode material according to the invention.
• the starting materials customary for this purpose can be used for producing the anode materials and lithium ion batteries according to the invention and the conventional methods for producing the anode materials and lithium ion batteries can be used, such as For example, in the patent application with the application number
• Another object of the invention are lithium-ion batteries comprising a cathode, an anode, a separator and an electrolyte, characterized in that
• the anode is based on the aforementioned anode material according to the invention.
• Another object of the present invention are methods for operating lithium-ion batteries comprising a cathode, an anode, a separator and an electrolyte, characterized in that
• ⁇ anode material is based
• the anode material is only partially lithiated when the lithium ion battery is fully charged.
• Another object of the invention is the use of the invention.
• Anode materials in lithium-ion batteries that are configured so that the anode materials are only partially lithiated in the fully charged state of the lithium-ion batteries. It is therefore preferred that the anode material, in particular the redispersible particles according to the invention from step b), is only partially lithiated in the fully charged lithium-ion battery.
• Fully charged indicates the condition of the battery in which the anode material of the battery has its highest lithium charge.
• Partial lithiation of the anode material means that the maximum lithium absorption capacity of the silicon particles in the anode material is not exhausted.
• the maximum lithium absorption capacity of the silicon particles generally corresponds to the formula Li 4 , 4 Si and is thus 4.4 lithium atoms per silicon atom. This corresponds to a maximum specific capacity of 4200 mAh per gram of silicon.
• the ratio of the lithium atoms to the silicon atoms in the anode of a lithium-ion battery can be adjusted, for example, via the electric charge flow.
• the degree of lithiation of the anode material or of the silicon particles contained in the anode material is proportional to the electric charge that has flowed.
• the capacity of the anode material for lithium is not fully utilized. This results in partial lithiation of the anode.
• the Li / Si ratio of a lithium-ion battery is set by the cell balancing.
• the lithium-ion batteries are designed so that the lithium absorption capacity of the anode is preferably greater than the lithium emitting capacity of the cathode.
• the lithium receptivity of the anode is not fully utilized, i. that the anode material is only partially lithiated.
• the Li / Si ratio in the anode material in the fully charged state of the lithium-ion battery is preferably ⁇ 2.2, more preferably 1.98 and most preferably 1.76.
• the Li / Si ratio in the anode material in the fully charged state The lithium ion battery is preferably 0,2 0.22, more preferably 0,4 0.44, and most preferably 0,6 0.66.
• the capacity of the silicon of the anode material of the lithium-ion battery is preferably used to ⁇ 50%, more preferably to 45%, and most preferably to 40%, based on a capacity of 4200 mAh per gram of silicon.
• the degree of lithiation of silicon or the utilization of the capacity of silicon for lithium can be determined, for example, as described in the patent application with the application number DE 102015215415.7 on page 11, line 4 to page 12, line 25, in particular with reference to the formula given there for the Si capacity utilization and the additional information under the headings "Determination of the delithiation capacity ß" and "Determination of the Si weight fraction ⁇ 3 ⁇ "("incorporated by reference").
• the redispersible particles according to the invention from step b) of the process according to the invention in water, in particular in aqueous ink formulations for anodes of lithium-ion batteries, are particularly stable and under these conditions have little or no tendency for hydrogen formation. This is especially true at neutral pH and at room temperature. This allows processing without foaming of the aqueous ink formulation and the production of particularly homogeneous or bubble-free anodes.
• the silicon used as educt in the process according to the invention and also the drying product from step a) generate large amounts of hydrogen in water.
• the prior art frequently teaches to reduce the formation of hydrogen in aqueous ink formulations by using silicon particles which are oxidized on the surface and thus passivated with respect to reactions with water.
• silicon particles with a higher degree of oxidation necessarily have a lower proportion of elemental silicon and thus also a lower storage capacity for lithium ions, resulting in lithium ion batteries with lower energy densities.
• an increasing silicon dioxide layer increases the initial losses.
• silicon dioxide also acts as an electrochemical insulator. In the inventive approach can be dispensed with a passivation of the silicon particles by oxidation, so that the energy densities of corresponding lithium-ion batteries and the electrochemical conductivity can be increased and the initial losses can be reduced.
• inventive anodes show better electrochemical performance. Further improvement of the cycle stability of the lithium ion batteries can be achieved when the batteries are operated under partial loading.
• the particle distribution measurement was performed by static laser scattering using the Mie model with a Horiba LA 950 in a highly diluted suspension in water. The indicated average particle sizes are volume weighted.
• the specific surface area of the particles was determined by nitrogen adsorption according to the BET method according to DIN 9277/66131 and 9277/66132.
• the determination of the oxygen content was carried out on the analyzer Leco TCH-600.
• the analysis was carried out by melting the samples in graphite crucibles under an inert gas atmosphere. Detection was via infrared detection (three measuring cells). Determination of carbon content:
• the determination of the carbon content (C content) of the samples was carried out on the Leco CS 230 analyzer.
• the analysis was carried out by high-frequency combustion of the sample in an oxygen stream. Detection was by means of non-dispersive infrared detectors.
• the dishwashing experiments were carried out in 50 ml Greiner tubes with a weight of 11 g of the silicon-containing powder and demineralized water.
• the washing water was first added to the powder so that the filled Greiner tube weighed 50 g.
• the suspension was mixed for 5 minutes and 90 rpm with a mixer (inti-dial).
• the mixture was then centrifuged for 20 min at 3500 rpm. fugles.
• the wash water was decanted and water was added again in a further washing step (total mass 50 g).
• total mass 50 g total mass 50 g.
• the described procedure was repeated twice. A change in the C and O contents is determined with a LECO analyzer.
• the polymer solution was initially charged and then diluted with distilled water with stirring.
• the total amount of water was chosen so that the polymer remained in solution even after adding the grinding Si suspension.
• the Si-containing suspension was added with stirring and mixed with the aid of a dissolver, a KPG stirrer or a roll bar. After homogenization, the suspension thus obtained was subjected to spray drying, as described below.
• the suspension was sprayed under inert conditions (nitrogen, ⁇ 6% oxygen) through a two-fluid nozzle (Model 150 nozzle) on a Buchi Model B-290 dryer with InertLoop.
• the atomizing component used was nitrogen in a closed circuit.
• the formed drops were dried at 120 ° C inlet temperature.
• the following parameters were selected for the settings on the dryer: Gas flow (flow): 601 L / h; Aspirator: 100%; Pumprate (Feed): 30%.
• the outlet temperature was between 50 and 60 ° C.
• the product was precipitated in a collecting vessel via a cyclone. Production of electrode coatings:
• the electrode ink was degassed (Speedmixer Hauschild) and applied to a copper foil with a thickness of 0.030 mm (Schlenk Metallfolien, SE-Cu58) by means of a film drawing frame with a 0.11 mm gap height (Erichsen, model 360).
• the anode coating thus produced was then dried for 60 minutes at 50 ° C. and 1 bar air pressure.
• the mean basis weight of the dry anode coating was 2.97 mg / cm 2 . Construction of Li ion cells and electrochemical characterization:
• the electrolyte used consisted of a 1.0 molar solution of lithium hexafluorophosphate in a 3: 7 (v / v) mixture of fluoroethylene carbonate and ethyl methyl carbonate, which was admixed with 2 wt% of vinylene carbonate.
• the construction of the cells was carried out in a glove box ( ⁇ 1 ppm H 2 0, 0 2 , MBraun), the water content in the dry matter of all components used was below 20 ppm.
• the electrochemical testing was carried out at 20 ° C.
• the cell was charged in constant current / constant voltage (cc / cv) mode with a constant current of 5 mA / g (C / 25) in the first cycle and 60 mA / g (C / 2) in the following Cycles and after reaching the voltage limit of 4.2 V with constant voltage to below a current of 1.2 mA / g (corresponds to C / 100) or 15 mA / g (corresponds to C / 8).
• cc / cv constant current / constant voltage
• the cell was discharged in the cc (constant current) method with a constant current of 5 mA / g (equivalent to C / 25) in the first cycle and 60 mA / g (equivalent to C / 2) in the subsequent cycles until reaching the voltage limit of 3.0 V.
• the selected specific current was based on the weight of the positive electrode coating.
• the cell balancing of the lithium-ion battery corresponded to partial lithiation of the anode.
• Example 4 The discharge capacity of a full cell based on the anode coating is shown in Example 4 as a function of the number of cycles.
• the full cell has a rever- sal in the second cycle.
• sible initial capacity 2.02 mAh / cm 2 and still has 80% of its original capacity after 82 charge / discharge cycles.
• Anode coatings which contain the active material according to the invention show a more stable cycle behavior with the same starting capacity.
• Example 1 Redispersible Si Particles with NaCMC as Polymer: Example 1a: Spray Drying Products:
• Example lb Thermal treatment of the spray-drying products: The powder obtained by spray drying in Example la was heat-treated in air for 24 hours in an air-circulating oven at an internal temperature of 130 ° C.
• EXAMPLE 2 Redispersible Si Particles with LiPAA as Polymer
• Example 2a Spray Drying Products
• Example la With the following differences: There were 35.3 g of a 4 wt .-% aqueous solution of lithium polyacrylate and 164.7 g of the ethanolic suspension of silicon and additional 142.9 g of distilled water used.
• Example 2b Thermal treatment of the spray-drying products: Identical as described for example 1b.
• the oxygen content of the particles increased only very slightly and the carbon content decreased only to a very small extent.
• the BET surface decreases to a small extent during a thermal aftertreatment.
• NaCMC sodium carboxymethylcellulose
• LiPAA lithium
• the decreasing carbon content represents the decreasing polymer content on the particles.
• Table 2 Composition of the Si particles before or after carrying out the dishwashing test:
• Example 4 showed no pressure change, while the ink of Comparative Example 3 showed a large increase in pressure.
• Silicon particles with a particle size d50 of 800 nm i.e., without polymer coating, without thermal treatment.
• the particles obtained had a C content of 0.64% and an O content of 23.5%.

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• 2017
  • 2017-02-09 KR KR1020197026403A patent/KR20190112805A/ko not_active Application Discontinuation
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