EP4222292A1

EP4222292A1 - Process for manufacturing silicon-containing materials

Info

Publication number: EP4222292A1
Application number: EP20820066.7A
Authority: EP
Inventors: Michael Fricke; Moritz Becker; Claudia KLEINLEIN; Jürgen Pfeiffer; Sebastian SUCKOW
Original assignee: Wacker Chemie AG
Current assignee: Wacker Chemie AG
Priority date: 2020-11-30
Filing date: 2020-11-30
Publication date: 2023-08-09
Also published as: CN116745459A; US20230416907A1; WO2022111830A1; JP2023552743A; KR20230113783A

Abstract

The invention relates to a process for manufacturing silicon-containing materials in a fluidized-bed reactor by depositing silicon from at least one silicon precursor in pores and on the surface of porous particles, characterized in that a pulsating fluidizing gas stream travels in waves in the fluidized-bed reactor and acts on the fluidized bed in such a way that a homogeneously fluidized bed is created which is characterized by a minimum fluidization index FI of 0.95. The invention also relates to the use of the silicon-containing materials obtained according to the disclosed process as active materials for anodes of lithium-ion batteries and corresponding lithium-ion batteries which contain, in the anode, a silicon-containing material obtained according to the disclosed process.

Description

Process for the production of silicon-containing materials

The invention relates to a method for producing silicon-containing materials in a fluidized-bed reactor by depositing silicon in pores and on the surface of porous particles, and the use of the silicon-containing materials obtained in this way as active materials for anodes of lithium-ion batteries .

As a storage medium for electrical power, 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. At present, graphitic carbon is widely used as an active material for the negative electrode ("anode") of corresponding batteries. A disadvantage, however, 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, for example, in EP 1730800 B1, US Pat. No. 10,559,812 B2, US Pat. No. 10,819,400 B2, or EP 3335262 B1. Silicon forms binary electrochemically active alloys with lithium, which enable very high electrochemically achievable lithium contents of up to 3579 mAh per gram of silicon [M. Obrovac, V.L. Chevrier Chem. Rev. 2014, 114, 11444].

The incorporation and deintercalation of lithium ions in silicon has the disadvantage that a very large change in volume occurs, which can reach up to 300% if the incorporation is complete. Such changes in volume expose the silicon-containing active material to severe mechanical stress, as a result of which the active material can finally break apart. This process, which is also known as electrochemical grinding, results in the active material and in the Electrode structure leads to a loss of electrical contact and thus to a sustained, irreversible loss of the capacity of the electrode.

Furthermore, the surface of the silicon-containing active material reacts with components of the electrolyte with the continuous formation of passivating protective layers (Solid Electrolyte Interphase; SEI). The components formed are no longer electrochemically active. The lithium bound in it is no longer available to the system, which leads to a pronounced continuous loss of battery capacity. Due to the extreme change in volume of the silicon during the charging and discharging process of the battery, the SEI regularly breaks up, which exposes further uncovered surfaces of the silicon-containing active material, which are then exposed to further SEI formation. Since the amount of mobile lithium in the full cell, which corresponds to the usable capacity, is limited by the cathode material, this is increasingly consumed and the capacity of the cell drops after just a few cycles to an extent that is unacceptable from an application point of view.

The decrease in capacity over the course of several charging and discharging cycles is also referred to as fading or a continuous loss of capacity and is usually irreversible.

A number of silicon-carbon composite particles have been described as active materials for anodes of lithium-ion batteries, in which the silicon, starting from gaseous or liquid silicon precursors, is embedded in porous carbon particles. The storage process is also referred to as deposition or infiltration and can take place in a gas fluidized bed, for example as described in US Pat. No. 10,508,335 B1.

It is generally known that gas fluidized beds are excellently suited for gas-solid reactions and thus also for the incorporation process of silicon in porous particles. In a gas fluidized bed, a bed of solid particles is loosened and carried by a gas flowing upwards to such an extent that the solid layer as a whole shows liquid-like behavior [VDI Heat Atlas 11th Edition, Section L3.2 Flow patterns and pressure loss in vortices - layers, pp. 1371 - 1382, Springer Verlag, Berlin Heidelberg, 2013].

Gas fluidized beds are generally also referred to as fluidized beds or as fluidized beds. The process of creating a fluidized bed is also referred to as fluidization or fluidizing.

The solid particles are very well dispersed in a gas fluidized bed. As a result, a very large contact area is formed between the solid and the gas, which can be ideally used for energy and mass transfer processes. Gas fluidized beds are generally characterized by very good material and heat transfer processes and by an even temperature distribution. The quality of the mass and heat transfer processes is particularly decisive for the homogeneity of products obtained by reactions in fluidized beds and can be correlated with the homogeneity of the fluidization state. A homogeneous fluidized bed or the homogeneity of the fluidization state is compared to an inhomogeneous we - Fluid bed or an inhomogeneous fluidization state due to a higher local heat transfer, due to a lower temperature difference in the fluidized bed, due to short mixing times of two different particle collectives with a similar particle size and particle density, due to a larger proportion of particles in suspension and due to a lower proportion of denoted by non-flow domains in the fluidized bed.

Several methods are known for evaluating the homogeneity of the fluidization state of a gas fluidized bed. For example, the fluidization state can be defined by the dimensionless Fluidization index FI, which compares the measured pressure loss across the entire fluidized bed with the theoretically maximum achievable pressure loss when the fluidized bed is fully developed, with a maximum value for the fluidization index of 1 being obtained for a completely fluidized fluidized bed [Bizhaem, Hamed K.; Tabrizi, Hassan B.: Experimental study on hydrodynamic characteristics of gas-solid pulsed fluidized bed. In: Powder Technology 237 (2013), pp. 14-23.]. In practice, measurement inaccuracies can lead to calculated values for FI being slightly above 1. Another way of assessing the fluidization state is to measure the local heat transfer between any surface of a built-in part in the fluidized bed and the fluidized bed itself. The level of the heat transfer coefficient correlates with the homogeneity of the fluidization state of the fluidized bed [Baerns , M.: Effect of interparticle adhesive forces on fluidization of fine particles. In: Industrial & Engineering Chemistry Fundamentals 5 (1966), No. 4, pp. 508-516].

The fluidization properties can be classified depending on the particle size and the solid density of the particles. Particles with a particle size d ₅₀ < 20 μm and with a density difference between particle and gas > 100 kg/m ³ fall into Geldart class C (cohesive) [Geldart, D.; Types of Gas Fluidization, Powder Technol., 7, 1973, 285-292]. Geldart class C particles are characterized by the fact that they are difficult to convert to a fluidized state. Due to their small particle size, the influence of the interparticle attractive forces is of the same order of magnitude or greater than the forces acting on the primary particles due to the gas flow. Correspondingly, effects such as the lifting of the fluidized bed as a whole and/or channel formation occur. When channels are formed, instead of a fluidized bed, tubes are formed in the particle bed, through which the fluidizing gas preferentially flows, while most of the bed does not flow through at all. As a result, no homogeneity of the fluidization is achieved. Will the gas speed significantly above the minimum fluidization speed of the primary particles of the bed, over time agglomerates consisting of individual particles are formed, which can be completely or partially fluidized. A typical behavior is the formation of layers with agglomerates of different sizes. In the bottom layer directly above the inflow plate there are very large agglomerates that show very little or no movement. In the layer above there are smaller agglomerates that are fluidized. The smallest agglomerates are present in the uppermost layer, some of which are entrained by the gas flow, which is problematic in terms of process technology. The fluidization behavior of such particle beds is also characterized by the formation of large gas bubbles and a low expansion of the fluidized bed. In the English-language literature, this behavior is referred to as "agglomerate bubbling fluidization" (ABF). [Shabanian, J.; Jafari, R.; Chaouki, J., Fluidization of Ultrafine Powders, IRECHE., Vol.4, Nl, 16-50].

It is clear to the person skilled in the art that ABF fluidized beds are unsuitable for the production of materials with homogeneous properties because of the inhomogeneities within the fluidized bed and the associated inhomogeneous material and heat transfer conditions.

Fluidizing aids are known for converting Geldart class C particles in the form of agglomerates into a predominantly homogeneous fluidized bed. For example, US Pat. No. 7,658,340 B2 describes how the size of the agglomerates can be reduced by the input of other force components such as vibrational forces, magnetic forces, acoustic forces, rotational or centrifugal forces or combinations thereof in addition to the force exerted by the fluidizing gas consisting of SiO ₂ nanoparticles (Geldart class C) in the fluidized bed are influenced in such a way that a predominantly homogeneous fluidized bed is formed. The homogeneity of the fluidized bed is evaluated visually by mixing colored and non-colored particles and using the fluidization index. The homogeneous fluidized bed is through a fluidization index close to 1, characterized by a clear bed expansion, by a homogeneous appearance, by low particle discharge and by short mixing times of 2 minutes.

Another way to fluidize Geldart class C particles is to introduce a pulsating flow of fluidizing gas. Akhavan et al. [Akhavan, A.; Rahman, F.; Wang, S.; Rhodes, M.; Enhanced fluidization of nanoparticles with gas phase pulsation assistance, Powder Technol., 284, 2015, 521-529] describe the effect of a pulsating fluidizing gas stream on the fluidizing properties of SiO ₂ and TiO ₂ particles (Geldart class C and ABF behavior ) in fluidized beds. The homogeneity of the fluidization was evaluated visually and by measuring the pressure loss. Through the use of gas pulsation, the gas channels could be destroyed and the fluidized bed went into a visually homogeneous state with significantly greater bed expansion than without pulsation. With the help of the pressure loss measurement, it could be shown that the entire particle bed was transferred to the fluidized bed. Furthermore, it was found that the fluidization with pulsation starts at lower minimum fluidization velocities than without pulsation.

Cadoret et al. [Cadoret, L.; Reuge, N.; Pannala, S.; Syamal,

M.; Rossignol, C.; Dexpert-Ghys, J.; Coufort, C.; Caussat, B.; Silicon Chemical Vapor Deposition on macro and submicron powders in a fluidized bed, Powder Technol., 190, 185-191, 2009] describe the deposition of silicon from monosilane SiH ₄ on non-porous sub-micron titanium oxide particles (Geldart- Class C) in a vibrated fluidized bed reactor. The aim of the investigation was to coat the TiO ₂ particles evenly without changing the particle size of the primary particles. The agglomerates could be limited to the size range of 300 to 600 μm in the fluidized bed by the vibration input. Pressure loss measurements have shown that the entire particle bed was fluidized during the coating reaction. Homogeneous reaction conditions throughout Fluidized bed reactors could be detected by electron micrographs using uniformly coated particles that were removed from different points in the fluidized bed reactor. Vibrating systems are disadvantageous in terms of the economics of the process, since vibrations have an adverse effect on the strength of the reactor materials, which leads to a shortened service life of the apparatus. Another disadvantage is the increasing complexity of the design of a vibrating fluidized bed reactor when scaling up and ensuring the tightness of such a fluidized bed reactor, which is important from a safety point of view, when using highly reactive gases, as is the case for the deposition of silicon from gaseous silicon precursors in porous particles is required.

US Pat. No. 10,668,499 B2 describes a method for applying a surface coating of Geldart class C particles, which can also be porous, in a fluidized bed reactor, the oscillating fluidizing gas flow being modulated in such a way that a standing wave of the gas flow forms - de. Due to the standing wave, the particles can be evenly distributed in the fluidized bed reactor. At the same time, the use of the standing wave makes it possible to deposit thin layers evenly distributed over all particles on the surface. In order to generate a standing wave, a reflector must be installed in the fluidized bed reactor, which must be partially permeable to the reaction gas. Under the reactive conditions of a deposition process, such reactor internals are a great disadvantage, since the material to be deposited can also accumulate on the reflector, as a result of which the gas permeability decreases with increasing process time up to a complete clogging of the fluidized bed reactor.

US Pat. No. 10,508,335 B1 describes a fluidized bed process for depositing silicon from SiH ₄ in porous carbon matrices. Here, however, particles with a particle size of d ₅₀ > 50 μm are used in the fluidized bed process in order to prevent the formation of large agglomerates consisting of primary particles avoided, since the formation of agglomerates creates an inhomogeneous fluidized bed, which leads to inhomogeneous reaction conditions at the reactor level and, at the same time, inhomogeneous reaction conditions at the agglomerate level also result from the slow mass transport within the agglomerate. A disadvantage of the method described is that the materials obtained for use in anode materials for lithium-ion batteries have to be brought to the required size of <20 μm by grinding in a complex further step. Material is also lost in this additional step, which severely limits the economic attractiveness of the process.

Against this background, the task was to find a technically easy-to-implement process for the production of silicon-containing materials by depositing silicon in pores and on the surface of porous particles by means of thermal decomposition of at least one silicon precursor in one To provide a fluidized bed reactor with sufficient homogeneous fluidization, with which silicon-containing materials with a high storage capacity for lithium ions become accessible, which enable high cycle stability when used as active material in anodes of lithium ion batteries , which avoids the disadvantages of the methods described in the prior art, in particular with regard to the lack of homogeneity of the products.

Surprisingly, it was found that the above-described problems of the methods according to the prior art for the deposition of silicon from a silicon precursor in or on porous particles can be effectively solved by conducting the deposition in a fluidized bed reactor is carried out with a fluidizing gas flow which acts on the fluidized bed in a pulsating manner in the form of a wave, so that a homogeneously fluidized fluidized bed is formed, which is characterized by a fluidization index of FI ≥ 0.95. In a preferred embodiment, the homogeneously fluidized bed is characterized by a heat transfer coefficient a between any Surface of a component located in the fluidized bed and the fluidized bed itself in relation to the maximum heat transfer coefficient α _max between any surface of a component located in the fluidized bed and the fluidized bed itself characterized by α/α _max ≥ 0.95.

Surprisingly, it was also found that in the inventive deposition of silicon from a gaseous silicon precursor, even with agglomerate formation in the fluidized bed, based on the internal porosity, homogeneously infiltrated products both within the agglomerates and within the entire fluidized bed reactor can be produced.

The subject matter of the invention is a process for the production of silicon-containing materials in a fluidized-bed reactor by depositing silicon from at least one silicon precursor in pores and on the surface of porous particles, characterized in that a fluidizing gas flow propagates in waves in the fluidized-bed reactor by pulsation and onto the Fluidized bed acts in such a way that a homogeneously fluidized fluidized bed is formed, which is characterized by a fluidization index FI of at least 0.95. The fluidization index FI is therefore generally selected from the range from 0.95 to 1.

In a preferred embodiment, the fluidized bed is characterized by a heat transfer coefficient α between any surface of a component located in the fluidized bed and the fluidized bed itself in relation to the maximum heat transfer coefficient α _max between any surface of a component located in the fluidized bed and the fluidized bed itself of α /α _max ≥ 0.95.

As fine particles, the primary particles of the porous particles can generally not be fluidized or can only be fluidized with the formation of agglomerates. It is therefore all the more surprising that in the method according to the invention a uniform deposition of silicon in and on the porous particles results. The silicon-containing materials obtained in this way can advantageously be used as active material for anodes in lithium-ion batteries and, due to the silicon deposited homogeneously in the pores and on the surface of the porous particles, make it possible to provide lithium-ion batteries with very high high cycle stability.

The following phases are preferably run through in the method according to the invention:

Phase 1: Filling the fluidized bed reactor with porous particles,

Phase 2: fluidization of the porous particles with at least one inert gas as fluidizing gas and temperature control of the fluidized bed reactor to the temperature for the reaction in phase 3,

Phase 3: fluidization with at least one inert gas as fluidizing gas with addition of reactive gas containing one or more silicon precursors and conversion of the silicon precursors with deposition of silicon in pores and on the surface of the porous particles,

Phase 4: Cooling of the fluidized bed reactor and fluidization with at least one inert gas as fluidizing gas,

Phase 5: Removal of the reaction products from the fluidized bed reactor.

In phase 1, porous particles are loaded into a fluidized bed reactor.

In phase 2, the porous particles, generally also called particle bed, are fluidized by supplying at least one inert gas and generally flushed at the same time. Gases or gas mixtures are preferably selected as the inert gas from the group consisting of hydrogen, helium, neon, argon, nitrogen and forming gas, the use of nitrogen or argon being particularly preferred. The inert gas component of the fluidizing gas is preferably at least 50%, particularly preferably at least 90% and most preferably at least 99%, based on the partial pressure of the inert gas components Total pressure of the fluidizing gas under standard conditions (according to DIN 1343).

The method is characterized in particular in that the fluidizing gas flow propagates in waves through pulsation in the fluidized bed reactor, or, to put it another way, it is excited to produce a pulse-like oscillation. Advantageously, the disadvantageous fluidization behavior of Geldart class C particles can be avoided by transferring the gas vibration to the fluidized bed. The fluidizing gas stream can, for example, be completely or partially pulsated. The ratio of the pulsated fluidizing gas stream to the entire fluidizing gas stream, with the entire fluidizing gas stream being composed of a pulsated and a non-pulsated fluidizing gas stream, is in a range of preferably 0.1 to 1, more preferably between 0.3 and 1 and particularly preferably between 0. 5 and 1. The vibration excitation can take place, for example, in the form of rectangular, triangular, sawtooth profiles, sinusoidal profiles or any combination thereof. The frequency of the oscillation, which indicates the reciprocal value of the period, is preferably in a range from 0.1 to 20 Hz, preferably between 0.5 and 10 Hz and particularly preferably between 0.5 and 6 Hz. which describes the ratio of the pulse duration to the period duration, is preferably in the range from 0.1 to 0.9, preferably from 0.2 to 0.8. The vibration excitation preferably takes place periodically with a constant frequency, pulse shape and duty cycle. In a further preferred embodiment, the fluidizing gas stream is excited to oscillate with a frequency and/or pulse shape and/or duty cycle that varies over time. The pulsated fluidizing gas flow preferably reaches the fluidized bed reactor via a gas-permeable floor. Undesirable effects such as channel formation or uncontrolled agglomerate growth can be prevented, for example, by adjusting the fluidizing gas flow to values in the preferred working range, preferably instantaneously. The method is preferably carried out with fluidizing gas streams with superficial velocities above the measured minimum fluidizing rate of the pulsated gas stream. The preferred working range is between 1 and 10 times the measured minimum fluidization rate, preferably between 2 and 8 times the measured minimum fluidization rate and particularly preferably between 2 and 5 times the measured minimum fluidization rate.

The fluidized bed is also referred to below as a fluidized bed, as is customary in the present technical field.

The method is also characterized in that the fluidization state of the fluidized bed is characterized by the dimensionless fluidization index FI > 0.95. The fluidization index FI is defined as the ratio of the measured pressure drop across the fluidized bed Δp _{WS,measurement} and the theoretically maximum achievable pressure drop Ap _wsth and is calculated using the following equation:

The theoretically maximum achievable pressure drop is calculated neglecting the gas density from the mass of the bed m _s , the acceleration due to gravity g and the reactor cross-sectional area A _WS to Δp _WS,th = m _s •g/A _WS . The other information for determining the fluidization index can be found below at the beginning of the description of the examples.

The method is preferably characterized in that the heat transfer coefficient a between any surface of a component located in the fluidized bed and the fluidized bed itself, based on the maximum heat transfer coefficient α _max between any surface of a component located in the fluidized bed and the fluidized bed layer itself is characterized by α/α _max ≥ 0.95. In addition to the fluidization, the temperature of the fluidized bed reactor is controlled in phase 2 with the continued pulsating supply of at least one inert fluidizing gas to the temperature for the reaction in phase 3.

The reaction in phase 3 generally refers to the decomposition of the silicon precursors with deposition of silicon in pores and on the surface of the porous particles.

In phase 3, in particular after the temperature for the deposition of silicon has been reached, the fluidization of the fluidized bed is generally continued by the pulsating supply of at least one inert gas and a reactive gas is supplied to the fluidized bed. The reactive gas is preferably fed in as a partial to complete addition to the inert gas stream or, to put it another way, as a component of the fluidizing gas or at another point in the reaction chamber independently of the fluidizing gas.

The inert gas component of the fluidizing gas preferably makes up at least 50% of the total pressure of the fluidizing gas under standard conditions (according to DIN 1343), based on the partial pressure of the inert gas components.

The reaction temperature or temperature for the deposition of silicon is preferably in the range of 100 to 1000°C, more preferably in the range of 300 to 900°C, and particularly preferably in the range of 380 to 750°C.

Silicon is deposited in the pressure range between preferably 0.1 and 5 bar, more preferably at atmospheric pressure.

The fluidization state preferably does not change substantially as a result of the supply of reactive gas. The fluidized bed is further characterized by a fluidization index FI > 0.95. In a further embodiment, the fluidized bed is preferably one in the fluidized bed due to the heat transfer coefficient a between any surface component located in the fluidized bed and the fluidized bed itself in relation to the maximum heat transfer coefficient αmax between any surface of a component located in the fluidized bed and the fluidized bed itself with optimal fluidization of the fluidized bed at a given fluidizing gas temperature and composition of α/αmax ≥ 0, 95 characterized.

The reactive gases used in phase 3 contain at least one or more silicon precursors. In addition to the silicon precursors, the reactive gases can contain inert gases. The reactive gases preferably contain >50%, particularly preferably >80% and particularly preferably >90% of inert gas, based on the partial pressure of the inert gas, of the total pressure of the reactive gas under standard conditions (DIN 1343).

The silicon precursor generally contains at least one reactive component which can generally react to form silicon upon thermal treatment. The reactive component is preferably selected from the group containing silicon-hydrogen compounds such as monosilane SiH ₄ , disilane Si ₂ H ₆ and higher linear, branched or cyclic homologues, neopentasilane 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 , hexachlorodisilane Si2Cl ₆ , and higher linear, branched or cyclic homologues, such as 1,1,2,2-tetrachlorodisilane Cl ₂ HSi-SiHCl ₂ , chlorinated and partially chlorinated oligo- and polysilanes, methylchlorosilanes, such as trichloromethylsilane MeSiCl ₃ , dichlorodimethylsilane Me2SiCl ₂ , chlorotrimethylsilane Me ₃ SiCl, tetramethylsilane Me ₄ Si, dichloromethylsilane

MeHSiCl ₂ r chloromethylsilane MeH ₂ SiCl, methylsilane MeH ₃ Si, chlorodimethylsilane Me ₂ HSiCl, dimethylsilane Me ₂ H ₂ Si, trimethylsilane Me ₃ SiH or mixtures of the silicon compounds described.

Particularly preferred reactive components are selected from the group comprising monosilane SiH ₄ , oligomeric or polymeric silanes, in particular linear silanes of the general formula Si _n H _n+2 , where n can be an integer in the range 2 to 10, and cyclic silanes of the general formula —[SiH ₂ ] _n — _, where n can be an integer in the range 3 to 10, trichlorosilane HSiCl ₃ , Dichlorosilane H ₂ SiCl ₂ and chlorosilane H ₃ SiCl, these being able to be used alone or also as mixtures, with SiH ₄ , HSiCl ₃ and H ₂ SiCl ₂ being used very particularly preferably alone or in a mixture.

In addition, the reactive gases can contain further components, for example dopants based on boron, nitrogen, phosphorus, arsenic, germanium, iron or compounds containing nickel. The dopants are preferably selected from the group comprising ammonia NH ₃ , diborane B ₂ H ₆ , phosphine PH ₃ , German GeH ₄ , arsane AsH ₃ and nickel tetracarbonyl Ni(CO) ₄ .

During phase 3, the temperature can be kept generally constant or varied by heating or cooling. The largely spatially uniform implementation of the silicon precursor in pores and on the surface of the porous particles is preferred, in particular in order to obtain material with homogeneous properties.

Different technical solutions can be used to control the reaction speed of the conversion of the silicon precursors in phase 3. The supply of heat in the fluidized bed reactor is preferably increased or reduced. This can, for example, increase or reduce sales. The heat removal from the fluidized bed reactor is preferably increased by cooling, for example one or more reactor walls being cooled or devices for heat removal, such as coolable plates, tubes or tube bundles, being introduced into the fluidized bed reactor. This can, for example, reduce the reaction speed. The reactive gas composition is particularly preferably changed in order to control the reaction rate very quickly. The course of the conversion of reactive gas in phase 3 is preferably followed analytically. As a result, it is possible, for example, to recognize when the desired amount of deposited silicon has been reached and thus keep the reactor occupancy time as short as possible. Such methods preferably include temperature measurement, for example to determine an exo- or endothermy, pressure measurements, for example to determine the course of the reaction due to changing ratios of solid to gaseous reactor content components, and other methods which, for example, involve observing the allow changing composition of the gas space during the conversion of reactive gas.

In a further preferred embodiment, in phase 3, in particular after the desired residence time, a portion of the silicon-containing material formed is removed from the fluidized bed reactor, while porous particles are replenished, an amount corresponding to the removed portion of silicon-containing material being particularly preferred porous particles are replenished. With the desired dwell time, adequate conversion of the silicon precursors or adequate deposition of silicon in or on the porous particles is achieved. This point in time can be determined, for example, by means of a gas chromatographic analysis of the gas stream leaving the fluidized bed reactor.

In phase 4, preferably after the reaction of reactive gas has ended, the fluidizing gas for pulsed fluidizing of the fluidized bed reactor is switched over to a gas stream comprising inert gas, preferably pure inert gas. In this way, for example, reactive components can be removed from the fluidized bed reactor. Inert gases selected from the group comprising hydrogen, helium, neon, argon or nitrogen or forming gas, optionally with the addition of air, are preferably used as components of the inert gas stream. Nitrogen, argon or air or mixtures thereof are particularly preferred. At the same time, the temperature of the fluidized bed reactor is preferably reduced to a desired level temperature, more preferably 20 to 50°C, particularly preferably 20 to 30°C.

In a specific embodiment, the fluidized bed reactor is flushed. Flushing is preferably carried out with a mixture containing inert gas and oxygen. This mixture preferably contains at most 20% by volume, more preferably at most 10% by volume and particularly preferably at most 5% by volume of oxygen. The temperature here is preferably at most 200°C, particularly preferably at most 100°C and particularly preferably at most 50°C. As a result, for example, the surface of the silicon-containing material can be modified, for example deactivated. For example, a reaction of any reactive groups present on the surface of the silicon-containing material can be achieved.

In phase 5, reaction products, in particular the material containing silicon, are removed from the fluidized bed reactor, if appropriate while maintaining an inert gas atmosphere present in the fluidized bed reactor.

The temperature, the pressure or differential pressure measurements in the fluidized bed reactor can be determined using measuring devices and measuring methods customary for fluidized bed reactors. After the usual calibration, different measuring devices produce the same measurement results.

In a preferred embodiment, the sequence of phases 2 to 4 is carried out multiple times. It is particularly preferred that no particles forming the fluidized bed are removed from the fluidized bed reactor. The silicon precursors used in the respective phase 3 can be the same or different. Phase 4 can be omitted in one or more sequences. Phase 4 is preferably also carried out in the last sequence carried out.

In a further preferred embodiment, the sequence of phases 2, 3 and optionally 4, ie optionally under Omission of phase 4, carried out several times, with silicon precursor-free reactive gases also being able to be used in one or more of the sequences in phase 3, with the silicon precursor-free reactive gases in the respective sequences generally being able to be the same or different , with the proviso that a reactive gas containing a silicon precursor is used in at least one sequence. Silicon precursor-free reactive gases generally contain no silicon precursor. The silicon precursor-free reactive gases preferably contain one or more hydrocarbons. In these specific embodiments, silicon precursor-free reactive gas can occur in a sequence before or after the deposition of silicon, or even between two depositions of silicon.

In a preferred specific embodiment, a reactive gas containing a silicon precursor is used in phase 3 of the first sequence and a hydrocarbon in a second sequence in phase 3 when the sequence of phases 2, 3 and optionally 4 is carried out several times -containing, silicon precursor-free reactive gas used. In this case, phase 4 can preferably be dispensed with in the first sequence. With these embodiments, a silicon-containing material is obtained which does not have an outwardly facing silicon surface.

In a further preferred specific embodiment, if the sequence of phases 2, 3 and optionally 4 is carried out multiple times, a hydrocarbon-containing, silicon precursor-free reactive gas is used in phase 3 in the first sequence and a silicon precursor-containing gas is used in the second sequence Reactive gas used. Optionally, in a third sequence in phase 3, a further hydrocarbon-containing, silicon precursor-free reactive gas can be used. Here, in the first sequence following phase 3 and/or in the second sequence following phase 3, phase 4 can be dispensed with. In this way, for example, a silicon-containing material can be obtained which has a gap between the porous particles and the deposited silicon Has a carbon layer and which optionally also carries an outer carbon layer, as a result of which no outward-facing silicon surface is present.

Any gases or mixtures of gases which can be converted to solid substances by increasing the temperature can be used as silicon precursor-free reactive gases. Examples include hydrocarbons selected from the group comprising aliphatic hydrocarbons having 1 to 10 carbon atoms, in particular 1 to 6 carbon atoms, preferably methane, ethane, propane, butane, pentane, isobutane, hexane, cyclopropane, cyclobutane, cyclopentane, and cyclohexane Cycloheptane, unsaturated hydrocarbons with 1 to 10 carbon atoms such as ethene, acetylene, propene or butene, isoprene or butadiene, divinylbenzene, vinylacetylene, cyclohexadiene, cyclooctadiene, cyclic unsaturated hydrocarbons such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, cyclohexadiene, cyclopentadiene, Dicyclopentadiene or norbornadiene, aromatic hydrocarbons such as benzene, toluene, p-, m-, o-xylene, styrene (vinylbenzene), ethylbenzene, diphenylmethane or naphthalene, other aromatic hydrocarbons such as phenol, o-, m-, p- Cresol, cμmol, nitrobenzene, chlorobenzene, pyridine, anthracene, phenanthrene, myrcene, geraniol, thioterpineol, norbornane, borneol, isoborneol, bornane, camphor, limonene, terpinene, pinene, pinane, carene, phenol, aniline, anisole, furan, furfural, furfuryl alcohol, hydroxymethylfurfural or bishydroxymethylfuran and mixed fractions containing a large number of such compounds, for example from natural gas condensates , petroleum distillates, coke oven condensates, mixed fractions from the product streams of a fluid catalytic cracker (FCC), steam cracker or a Fischer-Tropsch synthesis plant, or quite generally hydrocarbonaceous material streams from wood and natural gas -, petroleum and coal processing.

The hydrocarbon-containing, silicon precursor-free reactive gases can contain a hydrocarbon or mixtures of several hydrocarbons. The hydrocarbon-containing, silicon precursor-free reactive gases can without other components or as a mixture with inert gases or other reactive gases such as hydrogen. In addition, the hydrocarbon-containing, silicon precursor-free reactive gases can also contain other reactive components, such as dopants based on boron, nitrogen, phosphorus, arsenic, germanium, iron or compounds containing nickel. The dopants are preferably selected from the group comprising ammonia NH ₃ , diborane B ₂ H ₆ , phosphine PH ₃ , German GeH ₄ , arsane AsH ₃ and nickel tetracarbonyl Ni(CO) ₄ .

Any type of construction known to those skilled in the art can be used as fluidized bed reactors. As usual, starting from a gas-permeable floor, the region of the fluidized bed reactor follows, in which the bulk material, for example comprising porous particles, is fluidized and the fluidized bed is thus formed.

The gas-permeable tray is also referred to as a gas distributor tray or inflow tray. Examples of this are porous plates, perforated plates, nozzle trays, bubble trays, manufacturer-specific or proprietary designs or combinations thereof. For example, the inert portion of the fluidizing gas can be introduced into the fluidized bed reactor via one type of tray and the reactive gas as an additive or portion of the fluidizing gas can be introduced via another type of tray. In a preferred embodiment, the reactive gas is admixed with the fluidizing gas and, as its component, generates the fluidized bed with it. In a further embodiment, the reactive gas is fed to the reaction space at certain nozzles of the base plate parallel to the fluidizing gas. In a further preferred embodiment, the reactive gas is fed to the fluidized bed reactor at a different point away from the base plate, for example in countercurrent.

If the reactive gas is supplied at least in part via a bottom plate of the fluidized bed reactor, it is preferred that the gas-permeable bottom at temperatures below the Reaction temperature is cooled. As a result, reactions of the reactive gas with the surface of the gas-permeable base can be avoided.

Circular, elliptical, square, rectangular or generally convex polygonal embodiments are preferred for the cross-sectional area of the fluidized bed reactor. The shape of the fluidized bed reactor, in which the bed is fluidized, is preferably a circular cylinder, an elliptical cylinder or a prism with any base area. Above the area in which the fluidized bed is formed, the cross-sectional area preferably widens significantly. Designs of this so-called calming zone are preferably designed in a similar way to the area where the fluidized bed is formed. Furthermore, designs are preferred in which the cross-sectional area already changes in the region of the fluidized bed, it being possible for the cross-sectional area to be of any shape. In principle, the fluidized bed reactor can also be designed as a circulating fluidized bed.

The exit of the fluidizing gas from the fluidized bed reactor is preferably designed in such a way that particles entrained with the flow are separated from the fluidizing gas stream. Particles are separated off preferably by mechanical filtration, in particular using filter candles, filter bags, filter bags or filter bags or by means of electric filters. Another preferred way of separating solid particles from gas flows is by using centrifugal separators such as cyclones or centrifugal separators. Combinations such as installing a centrifugal separator upstream of a mechanical filter are other preferred designs.

The filtration unit is preferably cooled to temperatures below the temperature of the silicon deposition. Undesirable reactions between the reactive gas and the surface of the filtration material can also be avoided in this way. In order to generate a pulsation of the fluidizing gas flow, different options for exciting the vibration of the fluidizing gas flow are preferred. The oscillation of the fluidizing gas stream is preferably generated via pressure changes, particularly preferably via pneumatic and/or mechanical devices. The vibration of the fluidizing gas is preferably generated by rapid pressure changes of the fluidizing gas in the supply line in front of the gas-permeable floor, in the fluidized bed chamber itself and/or at the gas outlet before or after the filter, with the pressure change preferably taking place via fans and/or or shut-off devices is generated. A valve is preferably periodically opened and closed in the gas supply line. The pulsation frequency, for example, is adjusted via the time periods of the open or closed position. Another preferred embodiment is the use of a rotating flap in the gas supply line. The pulsation frequency is varied, for example, by specifying the speed of the rotating flap.

A preferred embodiment for generating partially pulsed fluidizing gas streams is achieved by the regulated division of the gas stream in the gas feed line to the fluidized bed reactor, with one of the gas streams being excited to oscillate. Both gas streams can be introduced into the fluidized bed reactor independently of one another via the gas-permeable tray or mixed upstream of the gas-permeable tray and introduced into the fluidized bed reactor as a mixture. The ratio of the pulsed fluidizing gas flow to the entire fluidizing gas flow can be determined by regulating the two gas flows.

For example, heating or cooling devices can be used to control the temperature of the process. A preferred procedure is to preheat the fluidizing gas in the feed line to the fluidized bed reactor. The heat transfer takes place preferably by radiation and convection. This preheating is preferably carried out by electric flow heaters, gas-fired flow heaters, steam-based flow heaters or combinations thereof. In order to set the desired reaction temperature in the fluidized bed reactor, preference is given to heating and cooling the fluidized bed. The fluidized bed is preferably heated and cooled by the heat transfer mechanisms of radiation, particle convection and gas convection. Preferred designs for heating heat transfer surfaces are radiant ovens with heating elements, gas firing, steam heating, heating using heat transfer oil (e.g. WACKER Helisol® with a heating medium temperature of up to 425°C), inductive heating or resistance heating. The thermal energy is exchanged preferentially between the heat transfer surface and the fluidized bed by radiation, particle convection and gas convection. The fluidized bed is also preferably heated by direct radiation, such as infrared heaters or microwaves. Another preferred embodiment for heating the fluidized bed is the direct inductive heating of the fluidized bed.

The reactor cooling is preferably implemented by heat transfer to flowing cooling media, the cooling media being able to be in liquid form or both liquid and gaseous as a result of boiling. The heat transfer surfaces for heating and cooling are preferably implemented by the reactor walls and by fittings of any shape and size in the fluidized bed, such as tubes, tube bundles or plates through which flow occurs.

Another preferred embodiment is the combination of pulsation of the fluidizing gas with other fluidizing aids. For example, the fluidized bed generated by pulsation of the fluidizing gas can also be moved mechanically by a stirring element. Furthermore, the superposition of the pulsation of the fluidizing gas with a mechanical vibration of the fluidized bed reactor is preferred. Also preferred is the combination of pulsation of the fluidizing gas with the introduction of additional gas jets, which are blown into the fluidized bed at a significantly higher gas velocity. In principle, any material that has the necessary mechanical strength for the respective process conditions is usually suitable for the construction of the fluidized bed reactor. With regard to chemical resistance, the fluidized bed reactor can consist, for example, of appropriate solid materials or of chemically non-resistant materials (pressure-bearing) with special coatings or plating of parts that come into contact with the media.

The materials for the fluidized bed reactors are preferably selected from the group containing metallic materials (according to DIN CEN ISO/TR 15608) for steels in material groups 1 to 11, for nickel and nickel alloys in groups 31 to 38, for titanium and titanium alloys Correspond to groups 51 to 54, for zirconium and zirconium alloys to groups 61 and 62 and for cast iron to groups 71 to 76, ceramic materials from oxide ceramics in the one-component system such as aluminum oxide, magnesium oxide, zirconium oxide, silicon dioxide, titanium dioxide (capacitor material ) and multi-component systems such as aluminum titanate (mixed form of aluminum and titanium oxide), mullite (mixed form of aluminum and silicon oxide), lead zirconate titanate (piezoceramic), and dispersion ceramics such as aluminum oxide reinforced with zirconium oxide ( ZTA - Zirconia Toughened Aluminum Oxide - Al ₂ O ₃ /ZrO ₂ ) and non-oxide ceramics (carbides, for example Silic ium carbide, boron carbide; nitrides, for example silicon nitride; aluminum nitride, boron nitride, titanium nitride; borides; silicides) and their mixtures, as well as composite materials belonging to the groups of particle composite materials (such as hard metal, ceramic composites, concrete, polymer concrete), fiber composite materials (such as glass fiber reinforced glass, metal matrix composites (MMC), Fiber cement, carbon fiber reinforced silicon carbide, self-reinforced thermoplastics, reinforced concrete, fiber concrete, fiber-plastic composites (such as carbon-fiber-reinforced plastic (CFRP), glass-fiber-reinforced plastic (GRP), aramid-fiber reinforced plastic (AFRP)), fiber-ceramic composites (Ceramic Matrix Composites (CMC)), penetrating composites or metal-matrix composites (MMC) (such as dispersion-strengthened aluminum alloys or dispersion-hardened NiCr superalloys), layered composite materials (such as bimetals, TiGr composite, composite plates and pipes, glass fiber-reinforced aluminum, sandwich constructions).

The inventive method for producing silicon-containing materials offers several advantages over the prior art. The production of products with homogeneous properties in a single, easily scalable reaction step is particularly advantageous. The improved material and heat transfer due to the pulsation of the fluidizing gas flow is also advantageous. Furthermore, the control of the process by targeted adjustment of the reaction temperature and reactive gas composition, which can be varied during the process, is to be rated as advantageous. In addition, the process management enables periodic multiple depositions from the same or also from different silicon precursors or silicon precursor-free reactive gases. As a result of these advantages, silicon-containing materials are accessible quickly and economically in an advantageous manner, in particular for use as active material for anodes of lithium-ion batteries with outstanding properties.

The porous particles are preferably selected from the group containing amorphous carbon in the form of hard carbon, soft carbon, mesocarbon microbeads, natural graphite or synthetic graphite, single- and multi-walled carbon nanotubes and graphene, oxides selected from the group containing silicon dioxide, aluminum oxide, Silicon-aluminum mixed oxides, magnesium oxide, lead oxides and zirconium oxide, carbides selected from the group containing silicon carbides and boron carbides, nitrides selected from the group containing silicon nitrides and boron nitrides, and other ceramic materials as can be described by the following component formula : Al _a B _b C _c Mg _d N _e O _f Si _g with 0 ≤ a, b, c, d, e, f, g ≤ 1; with at least two coefficients a to g > 0 and a*3 + b*3 + c*4 + d*2 + g*4 ≥ e*3 + f*2.

The ceramic materials can be, for example, binary, ternary, quaternary, quinary, senary or septernary compounds. Ceramic materials with the following component formulas are preferred:

Non-stoichiometric boron nitrides BN _Z with z = 0.2 to 1,

Non-stoichiometric carbon nitrides CN _Z with z = 0.1 to 4/3,

Boron carbonitrides B _X CN _Z with x = 0.1 to 20 and z = 0.1 to 20, where x*3 + 4 ≥ z*3 applies,

Boron nitride oxides BN _z O _r with z = 0.1 to 1 and r = 0.1 to 1, where 3 ≥ r*2 + z*3 applies,

Borocarbonitridooxide B _x CN _z O _r with x = 0.1 to 2, z = 0.1 to 1 and r = 0.1 to 1, where x*3 + 4 ≥ r*2 + z*3 applies,

Silicon carbon oxides Si _x CO _z with x = 0.1 to 2 and z = 0.1 to 2, where x*4 + 4 ≥ z*2 applies,

Silicon carbonitrides Si _x CN _z with x = 0.1 to 3 and z = 0.1 to 4, where x*4 + 4 ≥ z*3 applies,

Silicon borocarbonitrides Si _w B _x CN _z with w = 0.1 to 3, x = 0.1 to 2 and z = 0.1 to 4, where w*4 + x*3 + 4 ≥ z*3,

Silicon borocarbonoxides Si _w B _x CO _z with w= 0.10 to 3, x = 0.1 to 2 and z = 0.1 to 4, where w*4 + x*3 + 4 ≥ z*2 applies,

Silicon borocarbonitridooxides Si _v B _w CN _x O _z with v = 0.1 to 3, w = 0.1 to 2, x = 0.1 to 4 and z = 0.1 to 3, where v*4 + w* 3 + 4 ≥ x*3 + z*2 and Aluminum borosilicocarbonitridooxides Al _u B _v Si _x CN _w O _z with u = 0.1 to 2, v = 0.1 to 2, w = 0.1 to 4, x = 0.1 to 2 and z = 0.1 to 3, where u*3 + v*3 + x*4 + 4 ≥ w*3 + z*2.

The porous particles preferably have a density, determined by helium pycnometry, of 0.1 to 7 g/cm ³ and particularly preferably of 0.3 to 3 g/cm ³ . This is advantageous for increasing the gravimetric capacity (mAh/cm ³ ) of lithium-ion batteries.

Amorphous carbons, silicon dioxide, boron nitride, silicon carbide and silicon nitride or also mixed materials based on these materials are preferably used as porous particles, the use of amorphous carbons, boron nitride and silicon dioxide being particularly preferred.

The porous particles have a volume-weighted particle size distribution with diameter percentiles d ₅₀ of preferably ≧0.5 μm, more preferably ≧1.5 μm and most preferably ≧2 μm. The diameter percentiles d ₅₀ are preferably ≦20 μm, more preferably ≦12 μm and most preferably ≦8 μm.

The volume-weighted particle size distribution of the porous particles is preferably between the diameter percentiles d ₁₀ ≧0.2 μm and d ₉₀ d 20.0 μm, particularly preferably between d ₁₀ ≧0.4 μm and d ₉₀ d 15.0 μm and most preferably between d ₁₀ ≥ 0.6 µm to d ₉₀ d 12.0 µm.

The porous particles have a volume-weighted particle size distribution with diameter percentiles d ₁₀ of preferably ≦10 μm, particularly preferably ≦5 μm, particularly preferably ≦3 μm and most preferably ≦2 μm. The diameter percentiles d ₁₀ are preferably ≧0.2 μm, more preferably ≧0.5 and most preferably ≧1 μm. The porous particles have a volume-weighted particle size distribution with diameter percentiles d ₉₀ of preferably ≧4 μm and particularly preferably ≧10 μm. The diameter percentiles d ₉₀ are preferably ≦18 μm, more preferably ≦15 and most preferably ≦13 μm.

The volume-weighted particle size distribution of the porous particles has a width d ₉₀ -d ₁₀ of preferably ≦15.0 μm, more preferably ≦12.0 μm, particularly preferably ≦10.0 μm, particularly preferably ≦8.0 μm and most preferably ≤ 4.0 µm. The volume-weighted particle size distribution of the porous particles has a width d ₉₀ -d ₁₀ of preferably ≧0.6 μm, particularly preferably ≧0.8 μm and most preferably ≧1.0 μm.

The volume-weighted particle size distribution of the porous particles 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 particles are preferably in the form of particles. The particles can, for example, be isolated or agglomerated. The porous particles are preferably non-aggregated and preferably non-agglomerated. Aggregated generally means that in the course of the production of the porous 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 standard 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). Static light scattering methods for determining particle size distributions or particle diameters of matrix particles, on the other hand, cannot differentiate between aggregates or agglomerates.

The porous particles can have any morphology, that is, for example, they can be splintered, platy, spherical or needle-shaped, with splintered and spherical particles being preferred.

The morphology can be characterized by the sphericity y or the sphericity S, for example. According to Wadell's definition, the sphericity ψ 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, ψ has the value 1. According to this definition, the porous particles have a sphericity γ of preferably from 0.3 to 1.0, particularly 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: . In the case of an ideally circular particle, S would have the value 1. For the porous particles, the sphericity S is in the range of preferably 0.5 to 1.0 and more preferably 0.65 to 1.0, based on the percentiles Sio 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 μm, preferably with a scanning electron microscope through graphic evaluation using image analysis software such as ImageJ.

The porous 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 Obtain high capacity lithium-ion batteries. The gas-accessible pore volume was determined by gas sorption measurements with nitrogen in accordance with DIN 66134.

The porous 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”), ie the specific surface area. The porous particles have specific surface areas of preferably ≧50 m ² /g, particularly 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 particles can have any diameter, ie generally in the range of macropores (above 50 nm), mesopores (2-50 nm) and micropores (less than 2 nm). The porous particles can be used in any mixtures of different pore types. Preference is given to using porous particles with less than 30% macropores, based on the total pore volume, particularly preferably porous particles without macropores and very particularly preferably porous particles having at least 50% pores with an average pore diameter of less than 5 nm. Very particularly preferably, the porous particles exclusively 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 the pore size distribution in the macropore range is determined by mercury porosimetry according to DIN ISO 15901-1).

Preference is given to porous particles having a gas-inaccessible pore volume of less than 0.3 cm ³ /g and particularly preferably less than 0.15 cm ³ /g. This can also be used to increase the capacity of the lithium-ion batteries are increased. The gas-inaccessible pore volume can be determined using the following formula:

Gas-inaccessible pore volume = 1/pure material density - 1/skeletal density.

The pure material density is a theoretical density of the porous particles based on the phase composition or the density of the pure material (density of the material as if it had no closed porosity). Data on pure material densities can be obtained by a person skilled in the art, for example, from the Ceramic Data Portal of the National Institute of Standards (NIST, https://srdata.nist.gov/CeramicDataPortal/scd). For example, the pure material density of silicon oxide is 2.203 g/cm ³ , that of boron nitride is 2.25 g/cm ³ , that of silicon nitride is 3.44 g/cm ³ and that of silicon carbide is 3.21 g/cm ³ . The skeletal density is the actual density of the porous particle (gas accessible) determined by helium pycnometry.

For the sake of clarity, it should be noted that the porous particles are different from the silicon-containing material. The porous particles function as a starting material for the production of the silicon-containing material. There is preferably no silicon in the pores of the porous particles and on the surface of the porous particles, in particular no silicon that is obtained by depositing silicon precursors.

With the method according to the invention, it is surprisingly possible to fluidize the porous particles, which belong to Geldart class C, in a fluidized bed by means of the pulsating stream of fluidizing gas.

The silicon-containing material that can be obtained by depositing silicon in the pores and on the surface of the porous particles has a volume-weighted particle size distribution with diameter percentiles d ₅₀ , preferably in a range from 0.5 to 20 μm. The d ₅₀ value is preferably at least 1.5 µm, and more preferably at least 2 µm. The diameter percentiles d ₅₀ are preferably at most 13 μm and particularly preferably at most 8 μm.

The volume-weighted particle size distribution of the silicon-containing material is preferably between the diameter percentiles d ₁₀ ≧0.2 μm and d ₉₀ ≦20.0 μm, particularly preferably between d ₁₀ ≧0.4 μm and d ₉₀ ≦15. 0 µm and most preferably between d ₁₀ ≥ 0.6 µm to d ₉₀ ≤ 12.0 µm.

The silicon-containing material has a volume-weighted particle size distribution with diameter percentiles d ₁₀ of preferably ≦10 μm, more preferably ≦5 μm, particularly preferably ≦3 μm and most preferably ≦1 μm. The diameter percentiles d ₁₀ are preferably ≧0.2 μm, more preferably ≧0.4 μm and most preferably ≧0.6 μm.

The silicon-containing material has a volume-weighted particle size distribution with diameter percentiles d ₉₀ of preferably ≧5 μm and particularly preferably ≧10 μm. The diameter percentiles d ₉₀ are preferably ≦20 μm, more preferably ≦15 μm and most preferably ≦12 μm.

The volume-weighted particle size distribution of the silicon-containing material has a width d9o~ _d10 of preferably ≦15.0 μm, more preferably ≦12.0 μm, more preferably ≦10.0 μm, particularly preferably ≦8.0 μm and most preferably ≦ 4.0 µm. The volume-weighted particle size distribution of the silicon-containing material has a width d ₉₀ -d ₁₀ of preferably ≧0.6 μm, more preferably ≧0.8 μm and most preferably ≧1.0 μm.

The silicon-containing material is preferably in the form of particles. The particles can be isolated or agglomerated. The silicon-containing material is preferably non-aggregated and preferably non-agglomerated. The terms isolated, agglomerated and non-aggregated have already been defined above in relation to the porous particles. That The presence of silicon-containing materials in the form of aggregates or agglomerates can be made visible, for example, using conventional scanning electron microscopy (SEM).

The silicon-containing material can have any morphology, that is, for example, it can be splintered, flaky, spherical or needle-shaped, with splintered or spherical particles being preferred.

According to Wadell's definition, the sphericity ψ 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, ψ has the value 1. According to this definition, the silicon-containing materials have a sphericity ψ of preferably 0.3 to 1.0, more 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 ideal circular particle, S would have the value 1. For the silicon-containing materials, the sphericity S is in the range of preferably from 0.5 to 1.0 and more 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 μm, 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 or the internal porosity of the silicon-containing material. The silicon-containing material preferably contains 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 of porous particles, based on the Total weight of siliceous material.

The silicon-containing material contains preferably 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 via the deposition from the silicon Silicon obtained as a precursor, based on the total weight of the silicon-containing material (preferably determined by means of elemental analysis, such as ICP-OES).

If the porous particles contain silicon compounds, for example in the form of silicon dioxide, the above-mentioned wt Silicon mass of the porous particles is subtracted from the silicon mass of the silicon-containing material determined by means of elemental analysis and the result is divided by the mass of the silicon-containing material.

The volume of the silicon contained in the silicon-containing material obtained via the deposition from the silicon precursor results from the mass fraction of the silicon obtained via the deposition from the silicon precursor in the total mass of the silicon-containing material divided by the density of silicon (2.336 g/cm ³ ).

The pore volume P of the silicon-containing materials results from the sum of gas-accessible and gas-inaccessible pore volumes. The gas-accessible pore volume according to Gurwitsch of the silicon-containing material can be determined by gas sorption measurements with nitrogen in accordance with DIN 66134. The gas-inaccessible pore volume of the silicon-containing material can be determined according to the equation:

Gas-inaccessible pore volume = 1/pure material density - 1/skeletal density.

The pure material density of a silicon-containing material is a theoretical density that can be calculated from the sum of the theoretical pure material densities of the components contained in the silicon-containing material, multiplied by their respective weight-related percentage of the total material. For example, for a material containing silicon, where silicon is deposited on a porous particle, this results in:

Pure material density=theoretical pure material density of the silicon*proportion of the silicon in % by weight+theoretical pure material density of the porous particles*proportion of the porous particles in % by weight.

Data on pure material densities can be found by a person skilled in the art, for example, in the Ceramic Data Portal of the National Institute of Standards (NIST, https://srdata.nist.gov/CeramicDataPortal/scd). For example, the pure material density of silicon oxide is 2.203 g/cm ³ , that of boron nitride is 2.25 g cm ³ , that of silicon nitride is 3.44 g/cm ³ and that of silicon carbide is 3.21 g/cm ³ .

The pore volume P of the silicon-containing materials is in the range from 0 to 400% by volume, preferably in the range from 100 to 350% by volume and particularly preferably in the range from 200 to 350% by volume, based on the volume of the silicon containing material contained silicon obtained from the deposition of the silicon precursor.

The porosity contained in the silicon-containing material can be either gas-accessible or gas-inaccessible. The ratio of the volume of gas accessible to gas inaccessible Porosity of the silicon-containing material can generally 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-containing material 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-containing material can have any diameter, for example in the range of macropores (>50 nm), mesopores (2-50 nm) and micropores (<2 nm). The silicon-containing material can also contain any mixtures of different pore types. The silicon-containing material preferably contains at most 30% macropores based on the total pore volume, a silicon-containing material without macropores is particularly preferred and a silicon-containing material with at least 50% pores based on the total pore volume with an average pore diameter is very particularly preferred below 5 nm. The silicon-containing material particularly preferably has exclusively pores with a diameter of at most 2 nm.

The silicon-containing material has silicon structures which, in at least one dimension, have structure sizes of preferably no more than 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-containing material preferably contains silicon layers with a layer thickness of less than 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-containing material can also contain silicon in the form of 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 (REM) and/or high-resolution transmission electron microscopy (HR-TEM)). The information about the silicon particles preferably relates to the diameter of the circumference of the particles in the microscope image.

The silicon-containing material has a specific surface area of preferably at most 50 m ² /g, more preferably less than 30 m ² /g, and particularly preferably less than 10 m ² /g. The BET surface area is determined according to DIN 66131 (with nitrogen). When using the silicon-containing material as an active material in anodes for lithium-ion batteries, the SEI formation can be reduced and the initial Couloumb efficiency increased.

Furthermore, the silicon deposited from the silicon precursor can contain dopants in the silicon-containing material, for example selected from the group consisting of Li, Fe, Al, Cu, Ca, K, Na, S, Ci, Zr, Ti, Pt, Ni , Cr, Sn, Mg, Ag, Co, Zn,

B, P, Sb, Pb, Ge, Bi, rare earths or combinations thereof. Lithium and/or tin are preferred. The content of dopants in the silicon-containing material is preferably at most 1% by weight and particularly preferably at most 100 ppm, based on the total weight of the silicon-containing material, which can be determined using ICP-OES.

The silicon-containing material generally has a surprisingly high stability under pressure and/or shear stress. The pressure stability and the shear stability of the silicon-containing material is shown, for example, by the fact that the silicon-containing material shows no or only minor changes in its porous structure under pressure (e.g. during electrode compaction) or shearing stress (e.g. during electrode preparation). exhibits REM.

The silicon-containing material can optionally contain additional elements such as carbon. Carbon is preferred in the form of thin layers with a Layer thickness of at most 1 μm, preferably less than 100 nm, more preferably less than 5 nm and most preferably less than 1 nm (determinable via SEM or HR-TEM). The carbon layers can be present on the inner surface of pores and/or on the outer surface of the silicon-containing material. The sequence of different layers in the silicon-containing material through the use of different reactive gases in several phases 3 and the number of these layers is also arbitrary. For example, a layer of another material that is different from the porous particles, such as carbon, for example, can be present on the porous particles and a silicon layer or a layer of silicon particles can be present thereon. A layer of another material can also be present on the silicon layer or on the layer of silicon particles, which can be different or the same as the material of the porous particles, regardless of whether it is between the porous particles and the silicon layer or the layer consisting of silicon particles there is a further layer of a material different from the material of the porous particles. The process according to the invention is particularly advantageous here, since multiple coatings can be carried out without interruption by opening the fluidized bed reactor.

The silicon-containing material preferably contains <50% by weight, particularly preferably ≦40% by weight and particularly preferably 20% by weight of additional elements. The silicon-containing material preferably contains ≧1% by weight, particularly preferably ≧3% by weight and particularly preferably ≧2% by weight of additional elements. The percentages by weight are based on the total weight of the silicon-containing material. In an alternative embodiment, the silicon-containing material does not contain any additional elements.

Another object of the invention is the use of the silicon-containing material produced by the process according to the invention as an active material in anode materials for anodes of lithium-ion batteries and the use of the anodes according to the invention for the production of lithium-ion batteries.

The anode material is preferably based on a mixture comprising the silicon-containing material obtainable by the process according to the invention, one or more binders, optionally graphite as a further active material, optionally one or more further electrically conductive components and optionally one or more additives.

By using other electrically conductive components in the anode material, 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, for example, conductive carbon black, carbon nanotubes or metallic particles such as copper.

The primary particles of conductive carbon black preferably have a volume-weighted particle size distribution between the diameter percentiles d ₁₀ =5 nm and d ₉₀ =200 nm. The primary particles of conductive carbon black can also be branched like chains and form structures up to μm in size. Carbon nanotubes preferably have diameters of 0.4 to 200 nm, more preferably 2 to 100 nm and most preferably 5 to 30 nm. The metallic particles have a volume weighted particle size distribution preferably between the diameter percentiles d ₁₀ is 5 nm and d ₉₀ is 800 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-containing material in the anodes for lithium-ion batteries can preferably be 5 to 100% by weight, more preferably 30 to 100% by weight and most preferably 60 up to 100% by weight, based on the total active material contained in the anode material.

Preferred binders are polyacrylic acid or its alkali metal salts, especially lithium or sodium salts, polyvinyl alcohols, cellulose or cellulose derivatives, polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, polyimides, especially polyamideimides, or thermoplastic elastomers, especially ethylene-propylene-diene -terpolumers . Polyacrylic acid, polymethacrylic acid or cellulose derivatives, in particular carboxymethyl cellulose, are particularly preferred. The alkali metal salts, 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 be used.

In general, natural or synthetic graphite can be used as the graphite. The graphite particles preferably have a volume-weighted particle size distribution between the diameter percentiles d ₁₀ >0.2 μm and d ₉₀ <200 μm.

Examples of additives are pore formers, dispersants, leveling agents or dopants, for example elemental lithium.

Preferred formulations for the anode material preferably contain 5 to 95% by weight, in particular 60 to 90% by weight, of the silicon-containing material, 0 to 90% by weight, in particular 0 to 40% by weight, of other electrical components 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 binder and 0 to 80% by weight, in particular 0, 1 to 5% by weight of additives, the percentages by weight relating to the total weight of the anode material and the proportions of all components of the anode material add up to 100% by weight.

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.

The anode ink or paste has a pH value of preferably 2 to 7.5 (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 according to the invention.

Before the copper foil is coated with the anode material according to the invention, the copper foil is preferably treated with a primer, for example based on polymer resins or silanes. Primers can lead to improved adhesion to the copper, but generally have practically no electrochemical activity themselves.

The anode material is generally dried to constant weight. The drying temperature depends on the components used and the solvent used. It is preferably between 20 and 300.degree. C., particularly preferably between 50 and 150.degree. The layer thickness, ie the dry layer thickness, of the anode coating is preferably from 2 to 500 μm, particularly preferably from 10 to 300 μm.

Finally, the electrode coatings are preferably calendered in order 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 μm.

Another subject of the invention are lithium-ion batteries comprising a cathode, an anode, two electrically conductive connections to the electrodes, a separator and an electrolyte with which the separator and the two electrodes are impregnated, and a die Housing accommodating said parts, characterized in that the anode contains material containing silicon obtained by the method according to the invention.

For the purposes of this invention, the term lithium-ion battery also includes cells. Cells generally include a cathode, an anode, a separator, and an electrolyte. In addition to one or more cells, 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 for detecting 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 are used according to the invention.

The separator is generally an electrically insulating membrane permeable to ions, preferably made of polyolefins, for example polyethylene (PE) or polypropylene (PP), or polyester or corresponding laminates. As is customary in battery production, the separator can alternatively consist of glass or ceramic materials or be coated with them.

As is known, the separator separates the first electrode from the second electrode and thus prevents electronically conductive connections between the electrodes (short circuit).

The electrolyte is preferably a solution containing one or more lithium salts (=conductive salt) in an aprotic solvent. Conductive salts are preferably selected from the group consisting of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium imides, lithium methides, lithium trifluoromethanesulfonate LiCF ₃ SO ₃ , lithium bis(trifluoromethanesulfonimide) 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 corresponding salt. It is particularly preferably 0.8 to 1.2 mol/l.

Preferred solvents are 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 ester or nitriles, individually or as mixtures thereof, are used according to the invention.

The electrolyte preferably contains a film former such as, for example, vinylene carbonate or fluoroethylene carbonate. As a result, a significant improvement in the cycle stability of the anodes containing the silicon-containing active material obtained by the process according to the invention can be achieved. This is mainly attributed to the formation of a solid electrolyte interphase on the surface of active particles. The proportion of the film former in the electrolyte is preferably between 0.1 and 20.0% by weight, particularly preferably between 0.2 and 15.0% by weight and most preferably between 0.5 and 10% by weight.

In order to coordinate the actual capacities of the electrodes in a lithium-ion cell as optimally as possible, it is advantageous to balance the materials for the positive and negative electrodes in terms of quantity. Of particular importance in this connection is that during the first or initial charging/discharging cycle of secondary lithium-ion cells (the so-called formation) a covering layer forms on the surface of the electrochemically active materials in the anode . This top layer is referred to as "Solid Electrolyte Interphase" (SEI) and usually consists primarily of electrolyte decomposition products and a certain amount of lithium, which is _no longer available for further charging/discharging reactions. The thickness and The composition of the SEI depends on the type and quality of the anode material used and the electrolyte solution used. The SEI is particularly thin in the case of graphite. On graphite, there is a loss of typically 5 to 35 in the first charging step % of mobile lithium Correspondingly, the reversible capacity of the battery also decreases.

In anodes with the silicon-containing material obtained by the process according to the invention, there is a loss of mobile lithium in the first charging step of preferably at most 30%, more preferably at most 20% and most preferably at most 10%, which is well below the values described in the prior art, such as in US Pat. No. 10,147,950 B1.

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. All the substances and materials used to produce the lithium-ion battery according to the invention, as described above, are known. The production of the parts of the battery according to the invention and their assembly to form the battery according to the invention takes place according to the methods known in the field of battery production.

The silicon-containing material obtained by the process according to the invention is distinguished by significantly improved electrochemical behavior and leads to lithium-ion batteries with high volumetric capacities and outstanding application properties. The silicon-containing material obtained by the process according to the invention is permeable to lithium ions and electrons and thus enables charge transport. The SEI in lithium ion batteries can be reduced to a large extent with the silicon-containing material obtained by the process of the present invention. In addition, due to the design of the silicon-containing material obtained by the method according to the invention, the SEI no longer detaches from the surface of the active material, or at least detaches to a far lesser extent. All of this leads to a high cycle stability of corresponding lithium-ion batteries, the anodes of which contain the silicon-containing material obtainable by the process according to the invention.

The following examples serve to further explain the invention described here.

The following analytical methods and devices were used for characterization:

Scanning Electron Microscopy (SEM/EDX):

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. Before testing, the samples were treated with a Safematic Compact Coating Unit 010/HV to prevent charging phenomena carbon vaporized. The cross-sections of the silicon-containing materials shown in the figures were generated with a Leica TIC 3X ion cutter at 6 kV.

Inorganic analytics / elemental analysis:

The C contents given in the examples were determined using a Leco CS 230 analyzer, and a Leco TCH-600 analyzer was used to determine O and, where appropriate, N or H contents. The qualitative and quantitative determination of other specified elements in the silicon-containing materials obtained was carried out by means of ICP (inductively coupled plasma) emission spectrometry (Optima 7300 DV, from Perkin Elmer). For this purpose, 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 for examining acidic, aqueous solutions (e.g. acidified drinking water, waste water and other water samples, aqua regia extracts from soil and sediments).

Particle size determination :

In the context of this invention, the particle size distribution was determined according to ISO 13320 by means of static laser scattering with a Horiba LA 950. When preparing the samples, special care must be taken to disperse the particles in the measurement solution so that instead of individual particles not to measure the size of agglomerates. For the porous starting materials and silicon-containing materials investigated here, the particles were dispersed in ethanol. For this purpose, before the measurement, the dispersion was treated with 250 W ultrasound for 4 minutes in a Hielscher ultrasonic laboratory device model UIS250v with sonotrode LS24d5.

Surface measurement according to BET:

The specific surface area of the materials was determined by gas adsorption with nitrogen using a Sorptomatic 199090 device (Porotec) or device SA-9603MP (Horiba) according to the BET method (determination according to DIN ISO 9277:2003-05 with nitrogen).

Skeleton Density :

The skeletal density, i.e. the density of the porous solid based on the volume excluding the pore spaces accessible to gas from the outside, was determined using He pycnometry in accordance with DIN 66137-2.

Gas accessible pore volume:

The gas-accessible pore volume according to Gurwitsch was determined by gas sorption measurements with nitrogen in accordance with DIN 66134.

Determination of the fluidization index:

The fluidization index is the ratio of the measured pressure loss and the theoretically maximum possible pressure loss. In order to determine the fluidization index, it is necessary to measure the pressure drop in the fluidized bed. The pressure loss is measured as a differential pressure measurement between the lower and upper end of the fluidized bed. The differential pressure gauge converts the pressures recorded on the membranes into digital values and displays the pressure difference.

The pressure measuring lines are to be designed in such a way that they are arranged directly above the gas-permeable tray and directly above the fluidized bed. In order to determine the fluidization index, it is also necessary to precisely record the weight of the particle bed introduced. See also [VDI Heat Atlas 11th edition, Section L3.2 Flow patterns and pressure loss in fluidized beds, pp. 1371 - 1382, Springer Verlag, Berlin Heidelberg, 2013].

Determination of the minimum fluidization speed:

The minimum fluidization rate is the fluidization gas rate related to the empty reactor cross-sectional area, at which the bulk particles change from the flow-through fixed bed to a fluidized bed. Through simultaneous measurement of the fluidizing gas flow using a regulated mass flow meter and the pressure drop using a digital differential pressure meter the fluidized bed, the minimum fluidization speed can be determined. Knowing the cross-sectional area of the reactor, the fluidizing gas velocity can be calculated from the measured fluidizing gas flow. The recorded course of the pressure loss over the fluidizing gas velocity is referred to as the fluidized bed characteristic. It must be ensured that the fluidized bed characteristic curve is recorded starting from a high fluidizing gas velocity by gradually reducing this velocity. With pure fixed-bed flow, the pressure loss increases linearly. The associated fluidization index FI is less than one. In a fully developed fluidized bed, the measured pressure loss is constant. The associated fluidization index FI is equal to one. The state of minimal fluidization is present at the transition between the two areas. The associated fluidizing gas velocity related to the empty reactor cross-sectional area is equal to the minimum fluidizing velocity. If the transition from the fixed bed to the fluidized bed is characterized by an area, the point of intersection of the extrapolated fixed bed characteristic and the extrapolated fluidized bed characteristic is defined as the point of minimum fluidization. See also [VDI Heat Atlas 11th edition, Section L3.2 Flow patterns and pressure loss in fluidized beds, pp. 1371 - 1382, Springer Verlag, Berlin Heidelberg, 2013].

Measurement of heat transfer:

A heat flow probe is used to determine the heat transfer between any surface and the fluidized bed. The probe is constructed in such a way that a defined heat flow is generated in the probe by resistance heating is generated, which is released to the fluidized bed via a defined heat transfer area A. At the same time, the temperature of the heat transfer surface T _A and the fluidized bed T _WS is determined by using jacket resistance thermometers. The heat transfer coefficient can be calculated by the following equation.

Determination of the agglomerate size:

Samples are taken from the fluidized bed reactor to determine the size of the agglomerates formed during the fluidization of the porous particles and Geldart class C siliceous materials. Sampling is carried out by shutting off the fluidizing gas and opening the reactor. It must be ensured that the size of the agglomerates is not changed by taking the sample. To determine the agglomerate size, the agglomerates are examined using high-resolution optical digital microscopy. As a result, a size range for the agglomerates can be specified.

The fluidized bed reactor used to carry out the experimental examples consisted of a cylindrical part with an external diameter of 160 mm and a height of 1200 mm. The cylindrical part consisted of a bottom chamber and the actual fluidized bed reactor. The two parts were separated from each other by the gas-permeable floor. Above the cylindrical part of the reactor was a part of the reactor with a cross-sectional area that was twice as large as that of the cylindrical part of the reactor. At the upper end of the reactor there was a cover with filter elements for the gas outlet and connections for the introduction of a temperature sensor and a heat flow probe.

The reaction temperature was set by heating the reactor wall, the height of the heated area being 80% of the cylindrical length, beginning at the gas-permeable base. The heating was electric. Depending on the process phase, the fluidizing gas was preheated with a gas heater before it flowed into the fluidized bed reactor. The pulsation of the fluidizing gas flow was realized through the use of a directly controlled solenoid valve. The heat flow probe was installed 7 cm above the gas-permeable soil. The reaction temperature was increased by several Temperature sensors were determined in the fluidized bed, which were axially distributed at a constant distance from the reactor wall.

In preliminary tests, the minimum fluidization velocities and the maximum heat transfer coefficients for the porous particles and the fluidization gases used in the following examples were determined by measuring the pressure drop in the fluidized bed and by examining heat transfer using the heat flow probe for different gas compositions and temperatures.

Example 1:

Production of a silicon-containing material in a fluidized-bed reactor with a pulsating flow of fluidizing gas:

In phase 1 of the process, 1000 g of an amorphous carbon as porous particles (specific surface area = 1907 m ² /g, pore volume = 0.96 cm ³ /g, mean volume-weighted particle size D ₅₀ = 2.95 μm, particle density=0.7 g/cm ³ , Geldart class C particles) into the reactor.

In phase 2, the particle bed was fluidized with a fluidizing gas consisting of nitrogen, with the amount of gas being determined in such a way that at least three times the minimum fluidizing speed determined in the preliminary tests was present. At the same time, the gas flow was excited to oscillate with the help of the solenoid valve, the frequency between the open and closed position of the valve being 3 Hz. The pressure loss measurement and the heat transfer measurement resulted in a fluidization index of FI = 0.99 and a heat transfer coefficient based on the maximum heat transfer coefficient determined with optimal fluidization at the same temperature and gas composition of α/α _max = 0.98. After a stable fluidized bed had formed, the fluidizing gas was shut off and the reactor was opened in order to take samples from different points of the particle bed in the fluidized bed reactor to determine the agglomerate size. The size of the agglomerates was 237 +/- 50 μm. The reactor was then closed again and the fluidization was restarted. After a stable fluidized bed had again formed (FI=0.99 and α/α _max =0.99), the temperature in the reactor was increased to between 400 and 450.degree. During the temperature increase, the fluidization index was FI = 0.99 and the relative heat transfer coefficient α/α _max = 0.98. Due to the increase in temperature, the flow of fluidizing gas had to be adjusted.

After the reaction temperature of 400 to 450° C. had been reached, the fluidizing gas consisting of pure nitrogen was replaced in phase 3 of the process by a fluidizing gas consisting of 5% by volume of monosilane SiH ₄ as a silicon precursor in nitrogen.

The pulsation of the gas flow with the frequency between the open and closed position of the valve of 3 Hz persisted during and after the change of the fluidizing gases and values for the fluidization index of FI = 0.98 and the relative heat transfer coefficient of α/α were obtained _max = 0.98 determined. Due to the change in density of the porous particles during the deposition of the silicon, the amount of gas in the fluidizing gas was adjusted in such a way that the values of the fluidizing index and the relative heat transfer coefficient were always greater than 0.95.

After a reaction time of 220 minutes, the fluidizing gas was switched back to a pulsed stream of nitrogen in phase 4, values for the fluidizing index FI = 0.99 and the relative heat transfer coefficient of α/α _max = 0.99 being obtained again. The heating power has been reduced. After a temperature of 50° C. had been reached, the fluidizing gas stream was switched to a fluidizing gas consisting of 5% by volume oxygen in nitrogen and held for 60 minutes in order to react in a controlled manner any reactive groups present on the surface of the product obtained to let. The reactor was then cooled to room temperature.

After the reactor had been opened, in phase 5 samples were taken from the bed at different points in the reactor. On the size of the agglomerates was determined from these samples. Average agglomerate sizes of 289 +/- 70 μm could be determined here.

After sampling, 2248 g of a black solid were discharged from the reactor. The silicon-containing material obtained was filled into a cylindrical vessel and homogenized in a drum mixer. The agglomerates formed by the fluidized bed process can be easily removed by sieving. Samples were taken from the homogenized and sieved product for physico-chemical analysis, for electrochemical analysis and for electron microscopic investigations.

The analytical data of the solid obtained are listed in Table 1.

For the electron microscopic investigations, the product particles were isolated and embedded in epoxy resin. In order to evaluate the silicon distribution inside the particles, the particles embedded in epoxy resin were cut.

Figure 1 shows the SEM section through the particles for a representative sample. It can be seen here that porous particles (A) infiltrated with silicon appear lighter than the porous particles themselves (B). It can be seen that the vast majority of the product particles have a light color and thus a homogeneous, even deposition of silicon in the pores has taken place.

Example 2:

Production of a silicon-containing material with a carbon coating in a fluidized-bed reactor with a pulsed flow of fluidizing gas:

The same porous particles (specific surface area = 1907 m ² /g, pore volume = 0.96 cm ³ /g, mean volume-weighted particle size D ₅₀ = 2.95 μm, Particle density=0.7 g/cm ³ , Geldart class C particles) as used in example 1. The same amount of 1000 g was also charged into the reactor.

Phases 2 and 3 were also carried out analogously to example 1 with the same fluidizing gas flows and the same pulsation frequency. After completion of the silicon deposition in phase 3, the fluidizing gas was switched to a pure pulsed stream of nitrogen in a second phase 2, skipping phase 4. The reactor temperature was then adjusted to a temperature of 700-750°C. Due to the increase in temperature, the flow of fluidizing gas had to be adjusted again.

After the reaction temperature of 700 to 750°C was reached, phase 3 of the process was run through again, for which the fluidizing gas consisting of pure nitrogen was replaced by a fluidizing gas consisting of 5% by volume of ethyne C ₂ H ₂ as a carbon precursor nitrogen was replaced. The pulsation of the gas flow with the frequency between the open and closed position of the valve of 3 Hz persisted during and after the change of fluidizing gases and values for the fluidizing index of FI = 0.99 and the relative heat transfer coefficient of α were obtained /α _max = 0.98 determined. Due to the only insignificant increase in weight due to the carbon coating, it was not necessary to adjust the fluidizing gas flow.

After a reaction time of 80 minutes, phase 4 was carried out: the fluidizing gas was switched to a pulsed stream of nitrogen, whereby by adjusting the gas flow during cooling, values for the fluidizing index FI = 0.98 and the relative heat transfer coefficient of α/α _max = 0.97 were obtained. The heating was switched off and the reactor was cooled to room temperature.

After the reactor had been opened, in phase 5 samples were taken from the bed at different points in the reactor. The size of the agglomerates was determined on these samples. here larger agglomerates with an average diameter of 358 +/- 90 μm were determined compared to example 1.

After sampling, 2360 g of a black solid were discharged from the reactor. The silicon-containing material obtained was filled into a cylindrical vessel and homogenized in a drum mixer. The agglomerates formed by the fluidized bed process can be easily removed by sieving. Samples for physico-chemical analysis and for electrochemical analysis were taken from the homogenized, sieved product. The analytical data of the solid obtained are listed in Table 1.

Comparative example 3:

Production of a material containing silicon in a fluidized bed reactor without pulsation of the fluidizing gas:

Comparative example 3 was carried out analogously to example 1. The same porous particles (specific surface area=1907 m ² /g, pore volume=0.96 cm ³ /g, mean volume-weighted particle size D ₅₀ =2.95 μm, particle density=0.7 g/cm ³ , Geldart class C particles) as in example 1 and 2 used. In phase 1, the same amount of 1000 g was again introduced into the reactor

In phase 2, exactly the same fluidizing gas streams were set as in example 1, but without pulsation of the fluidizing gas stream. Determining the homogeneity of the fluidized bed results in a fluidization index of FI = 0.78 and a heat transfer coefficient based on the maximum heat transfer coefficient determined with optimal fluidization with pulsation at the same temperature and gas composition of α/α _max = 0.63. Based on these values, it could be deduced that the particle bed was not completely fluidized. This circumstance was also evident from the agglomerate diameters determined here. In the upper area of the bed, agglomerate diameters of 650 +/- 300 μm were measured. Agglomerates with a size of 3000 +/- 1000 μm were removed from the lower area of the bed above the gas-permeable floor. This large range of differently sized agglomerates in combination with the partial fluidization is typical for the formation of an ABF fluidized bed.

In phase 3 of the process, analogously to example 1, after the reaction temperature of 400 to 450° C. had been reached, the fluidizing gas consisting of pure nitrogen was replaced by a fluidizing gas consisting of 5% by volume of monosilane SiH ₄ as a silicon precursor in nitrogen . Values of FI = 0.75 and α/α _max = 0.58 were determined for the fluidization index and the relative heat transfer coefficient. As in phase 2, the data indicated an inhomogeneous fluidized bed during the separation process. Due to the change in density of the porous particles during the deposition of the silicon, the gas quantity of the fluidizing gas was changed analogously to the gas quantities set in Example 1.

Analogously to example 1, after a reaction time of 220 minutes in phase 4, the fluidizing gas was switched back to a stream of nitrogen. Values of FI = 0.76 and α/α _maxx = 0.62 were determined for the fluidization index and the relative heat transfer coefficient. The heating power has been reduced. After a temperature of 50° C. had been reached, the fluidizing gas stream was switched to a fluidizing gas consisting of 5% by volume oxygen in nitrogen and held for 60 minutes in order to react in a controlled manner any reactive groups present on the surface of the product obtained to let. The reactor was then cooled to room temperature.

After the reactor had been opened, in phase 5 samples were taken from the bed at different points in the reactor. Here, agglomerates with a size of 700 +/- 300 μm could be measured in the upper area of the bed. Agglomerates with a size of 3500 +/- 1000 μm had formed directly above the gas-permeable floor. After sampling, 2150 g of a black solid were discharged from the reactor. The silicon-containing material obtained was filled into a cylindrical vessel and homogenized in a drum mixer. The agglomerates formed by the fluidized bed process can be easily removed by sieving. Samples were taken from the homogenised, sieved product for physico-chemical analysis, for electrochemical analysis and for electron microscopic investigations. The analytical data of the solid obtained are listed in Table 1.

For the electron microscopic investigations, the product particles were isolated and embedded in epoxy resin. In order to evaluate the silicon distribution inside the particles, the particles embedded in epoxy resin were cut. Figure 2 shows the SEM section through the particles for a representative sample. It can be seen here that porous particles (A) infiltrated with silicon appear lighter than the porous particles themselves (B). It can be seen that there is great inhomogeneity in the silicon distribution, although the process conditions are the same apart from the pulsation. From this it can be concluded that homogeneous products are only produced with the method according to the invention as described in Example 1 be able.

With an increase in the fluidizing gas flow in comparison to example 1 in order to possibly increase the homogeneity of the fluidized bed even without pulsation, comparable values for the relative heat transfer coefficient as in example 1 according to the invention could not be achieved. In addition, an increased particle discharge is to be expected with a higher fluidizing gas flow. Another disadvantage would be that the contact time between the solid surface and the gas decreases with an increased flow of fluidizing gas, which leads to a lower conversion of the reactive components used in the flow of fluidizing gas.

Comparative Example 4 Production of a Material Containing Silicon in a Tubular Reactor:

A tubular reactor was filled with 3.0 g of the same porous carbon as in Examples 1 to 3 (specific surface area=1907 m ² /g, pore volume=0.96 cm ³ /g, mean volume-weighted

Particle size D ₅₀ = 2.95 microns, particle density = 0.7 g / cm ³ , Geldart class C particles) loaded in a quartz glass boat. After inertization with nitrogen, the reactor was heated to 410.degree. When the reaction temperature was reached, a reactive gas (10% SiH ₄ in N 2 , 10 l (STP)/h) was passed through the reactor for 5.2 h. The reactor was then purged with inert gas before the product was annealed at 500°C for 1 hour. Before removal from the reactor, the product was cooled to room temperature under inert gas. The analytical data of the solid obtained are listed in Table 1. Example 5:

Anode containing a silicon-containing material and electrochemical testing in a lithium-ion battery according to the invention:

29.71 g of polyacrylic acid (dried at 85° C. to constant weight; Sigma-Aldrich, Mw -450,000 g/mol) and 756.60 g of deionized water were mixed using a shaker (290 l/min) for 2.5 h moved until complete dissolution of the polyacrylic acid. Lithium hydroxide monohydrate (Sigma-Aldrich) was added in portions to the solution until the pH was 7.0 (measured with a WTW pH 340i pH meter and SenTix RJD probe). The solution was then mixed for a further 4 hours using a shaker. 3.87 g of the neutralized polyacrylic acid solution and 0.96 g of graphite (Imerys, KS6L C) were placed in a 50 ml vessel and mixed in a planetary mixer (SpeedMixer, DAC 150 SP) at 2000 rpm. Then 3.35 g of the silicon-containing material from Example 1 obtained by the process according to the invention were stirred in at 2000 rpm for 1 minute. Then 1.21 g of an 8 percent carbon black dispersion and 0.8 g deionized water were added and incorporated at 2000 rpm on a planetary mixer. This was followed by dispersion in a dissolver for 30 minutes at 3000 rpm at a constant 20°C. The ink was again degassed in a planetary mixer at 2500 rpm for 5 min under vacuum.

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 50° C. and 1 bar air pressure. The average basis weight of the dry anode coating was 3.0 mg/cm ² and the coating density was 0.7 g/cm ³ .

The electrochemical investigations were carried out on a button cell (type CR2032, Hohsen Corp.) in a 2-electrode arrangement. The electrode coating was used as a counter electrode or negative electrode (Dm=15 mm). A coating based on lithium-nickel-manganese-cobalt oxide 6:2:2 with a content of 94.0% and an average basis weight of 15.9 mg/cm ² (obtained from SEI) was used as the working electrode or positive electrode (Dm = 15 mm) used. A glass fiber filter paper (Whatman, GD Type D) saturated with 60 mΐ 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 H2O, O2), 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 using the cc/cv method (constant current/constant voltage) with a constant current of 5 mA/g (corresponding to C/25) in the first cycle and 60 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 1.2 mA/g (corresponding to C/100) or 15 mA/g (corresponding to C/8). The cell was discharged using the cc method (constant current) with a constant current of 5 mA/g (corresponding to C/25) in the first cycle and 60 mA/g (corresponding to C/2) in the subsequent cycles until it was reached the voltage limit of 2.5 V. The specific current chosen was based on the weight of the positive electrode coating. The electrodes were selected in such a way that a capacity ratio of cathode to anode of 1:1.2 was set.

The following test results were obtained with the full lithium-ion battery cell of example 5:

- reversible specific capacity of the negative electrode in the second cycle:

1280mAh/g (4.2 - 2.5V)

- Number of cycles with ≥ 80% capacity retention:

350 charge/discharge cycles. Example 6:

Anode with silicon-containing material from Example 2 and electrochemical testing in a lithium-ion battery according to the invention:

An anode was produced as described in example 5 using the silicon-containing material from example 2 obtained by the process according to the invention. The anode was built into a lithium-ion battery as described in Example 5 and subjected to testing using the same procedure.

The following test results were obtained with the full lithium-ion battery cell of example 6:

- reversible specific capacity of the negative electrode in the second cycle:

1210mAh/g (4.2 - 2.5V)

- Number of cycles with ≥ 80% capacity retention:

410 charge/discharge cycles.

Comparative example 7:

Anode with silicon-containing material from Comparative Example 3 and electrochemical testing in a lithium-ion battery:

An anode was produced as described in Example 5 using the silicon-containing material from Comparative Example 3 which was not obtained by the process according to the invention. The anode was built into a lithium-ion battery as described in Example 5 and tested using the same procedure.

The following test results were obtained with the full lithium-ion battery cell of Comparative Example 7:

- reversible specific capacity of the negative electrode in the second cycle:

1150mAh/g (4.2-2.5V)

- Number of cycles with ≥ 80% capacity retention:

208 charge/discharge cycles. Comparative example 8:

Anode with silicon-containing material from comparative example 4 and electrochemical testing in a lithium-ion battery An anode was produced as described in example 5 using the silicon-containing material from comparative example 4 not obtained by the process according to the invention. The anode was built into a lithium-ion battery as described in Example 5 and tested using the same procedure.

The following test results were obtained with the full lithium-ion battery cell of Comparative Example 8:

- reversible specific capacity of the negative electrode in the second cycle:

1240mAh/g (4.2 - 2.5V)

- Number of cycles with ≥ 80% capacity retention:

282 charge/discharge cycles. Table 2: Results of the electrochemical testing:

Claims

patent claims

1. Process for the production of silicon-containing materials in a fluidized bed reactor by depositing silicon from at least one silicon precursor in pores and on the surface of porous particles, characterized in that a fluidizing gas flow propagates in waves in the fluidized bed reactor by pulsation and acts on the fluidized bed in such a way that a homogeneously fluidized fluidized bed is formed, which is characterized by a fluidization index FI of at least 0.95.

2. The method according to claim 1, characterized in that the

Proceed at least the phases:

Phase 1: Filling the fluidized bed reactor with porous particles,

Phase 3: fluidization with at least one inert gas as

Fluidizing gas with addition of reactive gas containing one or more silicon precursors and conversion of the silicon precursors with deposition of silicon in pores and on the surface of the porous particles,

Phase 5: removal of the reaction products from the fluidized bed reactor.

3. The method according to claim 2, characterized in that during phases 2 to 4 the fluidized bed of the fluidized bed reactor by a heat transfer coefficient a between any surface of a built-in part located in the fluidized bed and the fluidized bed itself is characterized by α/α _max ≥ 0.95 in relation to the maximum heat transfer coefficient α _max between any surface of a component located in the fluidized bed and the fluidized bed itself.

4. Process according to any one of claims 2 to 3, characterized in that the temperature in phase 3 is in the range from 100 to 1000°C.

5. The method according to any one of claims 1 to 4, characterized in that the fluidizing gases contain at least 50% inert components selected from the group containing hydrogen, helium, nitrogen, neon, argon, krypton, xenon and carbon dioxide on the partial pressure of the inert components contained in the total pressure of the fluidizing gas.

6. The method according to any one of claims 2 to 5, characterized in that phase 3 is carried out with fluidizing gas streams with superficial velocities above the measured minimum fluidizing rate of the pulsated gas stream.

7. The method according to any one of claims 2 to 6, characterized in that the fluidizing gas flow in the fluidized bed reactor during phases 2 to 4 has a pulsation frequency in the range from 0.1 to 20 Hz.

8. The method according to any one of claims 2 to 7, characterized in that the fluidizing gas stream in the fluidized bed reactor during phases 2 to 4 has a duty cycle of the pulsation in the range from 0.1 to 0.9.

9. The method according to any one of claims 1 to 8, characterized in that the fluidized bed reactor is operated as a further fluidizing aid by the combination of pulsation of the fluidizing gas with mechanical stirring or mechanical vibration of the fluidized bed reactor or additional injection of gas jets becomes.

10. The method according to any one of claims 2 to 9, characterized in that the ratio of pulsed fluidizing gas flow to total fluidizing gas flow in the fluidized bed reactor during phases 2 to 4 is in the range from 0.1 to 1.

11. The method according to any one of claims 2 to 10, characterized in that during phase 3 some of the particles forming the fluidized bed are discharged and replaced by porous particles.

12. The method according to any one of claims 1 to 11, characterized in that the porous particles belong to Geldart class C.

13. The method as claimed in any of claims 2 to 12, characterized in that the sequence of phases 2, 3 and optionally 4 is repeated at least once, with phase 4 optionally being omitted one or more times.

14. The method according to claim 13, characterized in that at least one repetition of phase 3 uses a fluidizing gas which contains at least one hydrocarbon and no silicon precursor.

15. Use of the silicon-containing material obtainable by a method according to any one of claims 1 to 14 as an active material in anode materials for lithium-ion batteries for producing the negative electrodes of lithium-ion batteries.

16. Lithium-ion batteries comprising a cathode, an anode, 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 accommodating the parts mentioned , characterized, that the anode contains silicon-containing material obtainable by a method according to any one of claims 1 to 14.