METHOD FOR THE PRODUCTION OF SILICON-CONTAINING MATERIALS IN A MIXED TANK REACTOR

Description

[0001] A process for producing silicon-containing materials by thermal decomposition of silicon precursors in the presence of porous particles, wherein silicon is deposited in pores and on the surface of the porous particles in a gas-flowing reactor with a wall-penetrating stirrer. Lithium-ion batteries are currently the most practical electrochemical energy storage devices with the highest energy densities for storing electrical current. They are primarily used in portable electronics, power tools, and electrically powered vehicles such as bicycles, scooters, and automobiles. Graphitic carbon is currently widely used as the active material for the negative electrode ("anode") of such batteries.A disadvantage, however, is the relatively low electrochemical capacity of such graphitic carbons, which theoretically amounts to a maximum of 372 mAh per gram of graphite and thus corresponds to only about one-tenth of the electrochemical capacity theoretically achievable with lithium metal. Alternative active materials for the anode use the addition of silicon, as described, for example, in EP 1730800 B1, US 10,559,812 B2, US 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, VL Chevrier Chem. Rev. 2014, 114, 11444].

[0002] The insertion and removal of lithium ions into silicon has the disadvantage of causing a very large volume change, which can reach up to 300% in the case of complete insertion. Such volume changes subject the silicon-containing active material to severe mechanical stress, which can eventually cause it to break apart. This process, also known as electrochemical grinding, leads to a loss of electrical contact in the active material and the electrode structure, and thus to a permanent, irreversible loss of the electrode's capacitance.

[0003] Furthermore, the surface of the silicon-containing active material reacts with components of the electrolyte, continuously forming passivating protective layers (Solid Electrolyte Interphase; SEI). The components formed are no longer electrochemically active. The lithium bound within them is no longer available to the system, leading to a pronounced, continuous loss of battery capacity. Due to the extreme volume changes of the silicon during the charging and discharging process, the SEI regularly breaks down, exposing further, previously uncoated surfaces of the silicon-containing active material, which are then subject to further SEI formation. Since the amount of mobile lithium in the cell, which corresponds to the usable capacity, is limited by the cathode material, this material is increasingly consumed, and the cell's capacity drops to an application-unacceptable level after only a few cycles.

[0004] The decrease in capacity over several charge and discharge cycles is also known as fading or continuous capacity loss and is usually irreversible.

[0005] A number of silicon-carbon composite particles have been described as active materials for anodes of lithium-ion batteries, in which the silicon is incorporated into porous carbon particles starting from gaseous or liquid precursors.

[0006] It is generally known that in multiphase reaction systems good contact between the porous solid and the fluid precursor is necessary [F. Schüth Chem. Unserer Zeit 2006, 40, 92-103].

[0007] For example, US 10,147,950 B2 describes the deposition of silicon from monosilane SiH₄ in a porous carbon in a rotary kiln or similar furnace types at elevated temperatures of 300 to 900°C, preferably with particle agitation, by a CVD (chemical vapor deposition) or PE-CVD (plasma-enhanced chemical vapor deposition) process. A mixture of 2 mol% monosilane with nitrogen as an inert gas is used. The low concentration of the silicon precursor in the gas mixture leads to very long reaction times. Furthermore, the ratio of packing to reactor volume in a rotary kiln is usually very unfavorable, as otherwise significant particle carryover by the gas stream would occur.

[0008] Another method for carrying out gas-solid reactions, and thus also for the incorporation of silicon into porous starting materials, is gas fluidized beds. In a gas fluidized bed, a bed of solid particles is loosened and supported by an upward-flowing gas to such an extent that the solid layer as a whole exhibits liquid-like behavior [VDI Heat Atlas 11th edition, section L3.2 Flow modes and pressure drop in fluidized beds, pp. 1371–1382, Springer Verlag, Berlin Heidelberg, 2013].

[0009] Fluidized beds are also commonly referred to as fluidized beds or fluidized sheets. The process of creating a fluidized bed is also called fluidization.

[0010] In a fluidized bed of gas, the solid particles are very well dispersed. Consequently, a very large contact area between solid and gas is formed, which is ideal for energy and mass transfer processes. Fluidized beds of gas are generally characterized by very good mass and heat transfer processes and a uniform temperature distribution. The quality of the mass and heat transfer processes is particularly crucial for the homogeneity of products obtained through reactions in fluidized beds and can be correlated with the homogeneity of the fluidized state. Therefore, the formation of a homogeneous fluidized bed or a homogeneous fluidized state is essential for using the fluidized bed process to produce products with identical properties.

[0011] Depending on the particle size and solid density, the fluidization properties can be classified. For example, particles with a particle size d50 < 20 µm and a density difference between particle and gas > 1000 kg / m³ < fall into Geldart class C (cohesive) [D. Geldart, Types of gas fluidization, Powder Technology 7 (1973) 258]. Geldart class C particles are characterized by their difficulty in fluidizing. Due to their small particle size, the influence of interparticle attraction forces is of the same order of magnitude or greater than the forces exerted on the primary particles by the gas flow. Consequently, effects such as the lifting of the fluidized bed as a whole and / or channeling occur.During channel formation, instead of a fluidized bed, tubes form within the particle bed. The fluidizing gas preferentially flows through these tubes, while the majority of the bed remains unfluidized. This results in fluidization homogeneity. If the gas velocity is significantly increased above the minimum fluidization velocity of the primary particles in the bed, agglomerates consisting of individual particles form over time. These agglomerates can be completely or partially fluidized. A typical behavior is the formation of layers with agglomerates of varying sizes. The lowest layer, directly above the flow surface, contains very large agglomerates that exhibit little to no movement. The layer above contains smaller, fluidized agglomerates.The smallest agglomerates are found in the uppermost layer, some of which are carried along by the gas flow, which poses a problem for the process. The fluidization behavior of such particle beds is further characterized by the formation of large gas bubbles and low expansion of the fluidized bed. In 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, No.1, 16-50].

[0012] It is clear to experts that ABF fluidized beds are unsuitable for the production of materials with homogeneous properties due to the inhomogeneities within the fluidized bed and the associated inhomogeneous mass and heat transfer conditions.

[0013] For this reason, in GB 2580110 B2, for example, particles with a size (D 50 ) greater than 50 µm are fluidized in a fluidized bed with 1.25 vol% monosilane. However, after the reaction is complete, the particles obtained in this way must be milled to the required target size of < 20 µm. Fluidizing particles < 20 µm in this fluidized bed would lead to strong agglomerations and inhomogeneous infiltration of the porous carbon particles.

[0014] Fluidizing agents are known for converting particles < 20 µm in the form of agglomerates into a predominantly homogeneous fluidized bed. US 7,658,340 B2, for example, describes how the introduction of additional force components such as vibrational forces, magnetic forces, acoustic forces, rotational or centrifugal forces, or combinations thereof, alongside the force exerted by the fluidizing gas, influences the size of the agglomerates consisting of SiO₂ nanoparticles (Geldart class C) in the fluidized bed in such a way that a predominantly homogeneous fluidized bed is formed.

[0015] Cadoret et al. [Cadoret, L.; Reuge, N.; Pannala, S.; Syamlal, 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 SiH₄ onto non-porous sub-micrometer titanium oxide particles in a vibrated fluidized bed reactor. The vibration input limited the size of the agglomerates in the fluidized bed to the range of 300 to 600 µm.

[0016] Fluidized bed processes without fluidizing agents are unsuitable for the deposition / deposition of silicon in porous matrix particles because particles smaller than 20 µm cannot be homogeneously fluidized. The inhomogeneous fluidized bed prevents the production of homogeneous products.

[0017] Fluidized bed processes using fluidizing agents are disadvantageous for the deposition / deposition of silicon in porous matrix particles because fluidizing particles smaller than 20 µm requires significant technical effort. This additional effort is associated with high investment and maintenance costs.

[0018] Another disadvantage of silicon incorporation via fluidized bed processes with fluidizing agents is that the properties of the primary particles, such as particle density or surface finish, change during the process. These changes affect agglomerate formation in unknown ways, which in turn should be known for the process operation. Homogeneous process conditions over the entire process duration cannot be guaranteed.

[0019] Another disadvantage of fluidized bed technology is that, due to the fluidization of the agglomerates consisting of the primary porous particles, gas flows are required, which lead to a discharge of primary particles and / or smaller agglomerates.

[0020] A fundamental disadvantage of fluidized bed technology is that the fluidizing gas flow required to form a homogeneous fluidized bed depends on the size of the particles or agglomerates within the fluidized bed. Consequently, the amount of reactive gas added and the contact time of the reactive gas with the porous particles are dependent on the fluidization and mixing state of the particle bed. For example, in the fluidized bed process, increasing the contact time of the gaseous reactive component with the particle bed can only be achieved by reducing the gas velocity. However, the gas velocity is the crucial parameter for ensuring the fluidization and mixing state.

[0021] One way to solve the disadvantages of fluidized bed technology is to mix the particle bed with the gas phase in a flow-independent manner.

[0022] US patent application 2020 / 0240013 A1 describes the deposition of silicon from a silicon-containing gas onto particles with an average particle size in the lower millimeter range in a stirred bed reactor. Due to the particle size, the bulk material used is assumed to be highly fluid. The described apparatus facilitates the exchange between gas and solid by employing a central agitator screw, through which the reaction gas is simultaneously fed via openings in the stirred bed. The application specifically highlights the advantages of treating millimeter-sized particles, as large fluidizing gas flows are necessary to bring particles of this size into a fluidized state.

[0023] However, the stirrer used in US 2020 / 0240013 A1 is unsuitable for the circulation of cohesive particles < 20 µm.

[0024] It is known from the literature that a wide variety of agitators can be used for circulating particles in a stirred bed [M. Müller, Solid Mixing, Chemie Ingenieur Technik 2007, 79, 7]. For example, the use of a wall-penetrating helical agitator transports the particles laterally upwards in the reactor, resulting in a circulation flow with relative movement of the particles due to the material sliding down. This prevents the particles from adhering to the reactor wall.

[0025] A key parameter for describing the state of motion of the particle bed is the Froude number (Fr), which indicates the ratio of centrifugal force to weight force in the rotating system. Fr = r c ω 2 g

[0026] This is r c the characteristic radius relevant to the system. For systems with a rotating mixing tool, this corresponds to r c the outer radius of the agitator. In systems with a rotating drum, r c The inner radius of the container. The angular frequency. ω = 2 πn depends on the rotational speed n of the rotating system. The influence of gravity is taken into account via the acceleration due to gravity, g. At low Froude numbers, the contribution of gravity predominates, resulting in low radial material transport. The particle bed is only insufficiently circulated. At high Froude numbers, on the other hand, the contribution of centrifugal force dominates, causing the material to be pushed too strongly against the container wall. Here, too, the particle bed is only insufficiently circulated.

[0027] One parameter for describing the contact time between the gas phase and the stirred particle bed is the residence time of the gaseous reactive component in the reactor. The mean residence time t V can be calculated as the quotient of reactor volume and the volume flow rate of the metered gas phase V̇ F to be calculated: t V = V R V ˙ F

[0028] Another important measure for evaluating the homogeneous reaction conditions in the stirred bed reactor is the ratio do / TV from the turnover time of the particle bed do residence time of the silicon precursor TV The revolution period do The particle bed volume is calculated as the quotient of the reactor volume VR and the volume flow of recirculated particles V̇ P . t U = V R V ˙ P

[0029] The volume flow rate of the particles circulated by the stirring element V̇ Pis defined as the volume of particles displaced per unit time by the stirring element in a tangential direction and is generally described by the following formula: V ˙ P = n 2 π ∑ i ∫ r R , innen , i r R , au ß en , i r R , i h o , i r − h u , i r dr R , i

[0030] The volume flow rate of circulated particles is the product of rotational speed n and the sum of all tangentially displaced volumes by the individual stirring elements. i of the stirring element. The geometric dimensions of each individual stirring element are determined by the distance of the inner edge of the stirring element to the axis of rotation. r R,innen,i , by the distance of the outer edge of the stirring element to the axis of rotation r R,outside,i as well as through the upper contour hoi ( r ) and lower contour hu ( r ) of the respective stirring element is taken into account.

[0031] The ratio do / TVFor values ​​< 1, the particle circulation process is faster than the flow of gas through the bed, resulting in a uniform distribution of the gas and particles. For values ​​of the ratio do / TV > 1 The gas flows through the stirred bed faster than the bed itself is circulated. This creates zones with different deposition conditions in the stirred bed, leading to an inhomogeneous product distribution within the bed.

[0032] GB 2 580 110 B relates to a process for the production of electroactive materials for metal-ion batteries

[0033] EP 2 889 097 A1 relates to a process for the production of a porous electroactive material.

[0034] US 2020 / 240013 A1 relates to a device for producing particles or material-coated particles by decomposing a precursor gas in a stirred or mixed particle bed.

[0035] Against this background, the task was to provide a process for the production of silicon-containing materials, preferably with high storage capacity for lithium ions, which enable high cycle stability when used as active material in anodes of lithium-ion batteries, starting from porous particles and silicon precursors, which is technically easy to implement and does not have the disadvantages of the above-described prior art processes, in particular with regard to particle discharge, reaction times and the necessary infrastructure.

[0036] In particular, it is desirable to keep the dead space of the material not moved by the agitator as small as possible. This ensures that the material is kept in motion as efficiently as possible at the heated parts of the jacket and that energy is transferred from the wall into the material. Furthermore, this prevents particles from adhering to the wall.

[0037] The invention relates to a method for producing silicon-containing materials by thermal decomposition of silicon precursors in the presence of porous particles, wherein silicon is deposited in pores and on the surface of the porous particles, wherein the thermal decomposition of the silicon precursors takes place in the reaction zone of a gas-flowing reactor and the particles are circulated in the reaction zone during thermal decomposition by means of a wall-penetrating stirrer in the heated areas, wherein the stirrer is wall-penetrating if in equation 1 W h = u R h u B h for half of all values ​​of h wall penetration W ( h ) in the reaction zone W(h) > 0.9, where u R ( h ) = the outer circumference of the agitator in the cross-sectional area at the height coordinate h is and u B ( h ) = the inner circumference of the reactor.

[0038] Surprisingly, it was found that by using a wall-penetrating stirring tool according to the invention, very small particles, in particular particles < 20 µm, are circulated in a reactor and the gas flow of reactive component is metered in such a way that the contact time between gas phase and solid is long enough that the introduction process of silicon into the porous particles takes place homogeneously and with a high conversion of the silicon precursor, while at the same time the discharge of particles with the gas flow from the reactor is minimal.

[0039] In comparison to the fluidized bed reactor with fluidizing aids, the gas-flowing stirred reactor, stirred bed reactor (SBR) -The SBR process is structurally simpler because a smaller quantity of gas needs to be compressed and preheated, as the gas is not used for fluidization. This results in lower costs for the associated equipment. Complex control technology for operating the fluidizing agents is not necessary in the SBR. Compared to the FBR, the SBR is smaller because the stirred bed occupies a smaller volume for the same mass. The specific investment costs are therefore lower.

[0040] In comparison to GB 2580110 B2, no further process steps are necessary with the method according to the invention.

[0041] In contrast to a fluidized bed reactor, particle circulation is independent of the supply of a gas phase. Longer residence times are possible, leading to higher conversions of the reactive components.

[0042] In the process according to the invention, the particles are only circulated by the stirring. The particles are not agitated by the stirrer.

[0043] The gas flow is preferably dimensioned such that the suspension of particles by the gas flow in the process according to the invention is minimal, and thus the particle discharge from the reactor is also minimal. At the same time, the gas flow is preferably dimensioned such that the conversion of the reactive components used is maximized.

[0044] Homogeneous deposition conditions are possible by appropriate parameter selection of stirrer speed, expressed by the dimensionless Froude number, and by a suitable dosing rate.

[0045] Compared to US 2020 / 0240013 A1, the inventive method is improved by the use of a wall-penetrating stirrer.

[0046] The stirrer speed is preferably set so that the circulation times of the particle bed are shorter than the residence times of the fluid reactive component, especially the porous particles. This ensures sufficiently good macro-mixing of the fluid phase with the solid phase, resulting in homogeneous treatment of all particles in the solid phase.

[0047] A further economic advantage of the process, in contrast to non-inventive processes, lies in the higher silicon yield. Furthermore, silicon is deposited particularly uniformly on and, above all, within the porous particles, resulting in high stability of the silicon-containing material when used as an active material in anodes for lithium-ion batteries, while simultaneously exhibiting low volume change during cycling.

[0048] The wall penetration W(h)The perimeter of an agitator in a rotationally symmetric reactor is defined as the quotient of the perimeters of two planar cross-sectional surfaces perpendicular to the axis of rotation of two surfaces of revolution, where h The height coordinate is represented. The inner surface of revolution is formed by one complete revolution of the agitator and is defined by the distance. r R (h) Characterized from the axis of rotation to the outer contour of the agitator. The agitator includes all components attached to it. A planar section at any point. h The surface of revolution perpendicular to the axis of rotation forms a circular cross-section. The circumference of the inner cross-section is calculated using u R h = 2 πr R h

[0049] The outer surface of revolution is formed by rotating the inner contour of the reactor around the axis of rotation. It is determined by the distance r B (h)described. The inner contour of the reactor includes all components attached to it. The perimeter of any cross-sectional area of ​​the outer surface of revolution perpendicular to the axis of rotation is calculated using u B h = 2 πr B h

[0050] The wall penetration is defined as follows using the circumferences: W h = u R h u B h

[0051] In general, a reactor can contain one or more agitators. The contour of each individual agitator forms a surface of revolution as it completes its rotation. These surfaces of revolution can exist separately, but preferably they can be superimposed. If the individual surfaces of revolution, or the superimposed surface of revolution, are intersected at any point perpendicular to the axis(s) of rotation, figures or a single figure are obtained whose perimeter can be determined. If several figures are obtained, the total perimeter is determined by summing the individual perimeters.

[0052] In general, the reactor can consist of one or more reactor sections, which are preferably rotationally symmetrical and connected to each other. The entirety of all reactor walls encloses a figure. If this figure is cut at any point perpendicular to the axis of rotation of the agitators, the circumference of the resulting figure can be determined. The wall penetration W(h) is calculated in an analogous manner to that for the rotationally symmetric reactor.

[0053] Wall penetration can be achieved with h vary. The inventive design of the stirrer is achieved when at least half of all values ​​of h wall penetration W ( h ) in the reaction zone W(h) > 0.9; for this, W ( h 50% ). In a preferred embodiment, W ( h 50% ) > 0.95. In a particularly preferred embodiment, W ( h50% ) > 0.97. In a particularly preferred embodiment, W ( h 50% ) > 0.99. The reaction zone is the area in the reactor where the stirred particle bed comes into contact with the reactive component and the reactive component is decomposed. Values ​​for specific cases of the process are also possible. W ( h 50% ) > 1 possible.

[0054] Preferably, the process is carried out in a cascade reactor system comprising several reactors.

[0055] Conducting the process in a cascade reactor offers the advantage over conducting it in a single reactor that the long cooling and heating phases of a single reactor are reduced. This results in time and energy savings compared to a single reactor and leads to less stress on the reactor components. The cascade reactor system also offers the advantage that the individual reactors can be precisely designed for their specific purpose. Furthermore, the cascade reactor system is more scalable, as varying numbers of reactors can be combined for each phase.

[0056] In a preferred embodiment, the method comprises at least phases 1 to 3: Phase 1: Filling reactor A with porous particles and pretreating the particles, followed by transferring the pretreated particles into reactor B. or into a storage container, or the material remains in reactor A. Phase 2: Reactor B is percolated with a gas consisting of an inert gas and / or at least one reactive component containing a silicon precursor and / or at least one silicon-free precursor. The reactor is heated to a temperature at which the thermal decomposition of the reactive component occurs on the surface and in the pores of the porous particles. The particle bed in reactor B is circulated by a wall-penetrating stirrer such that the state of motion of the packed bed can be described by Froude numbers in the range between 1 and 10. The gas phase is fed into reactor B while the particle bed in reactor B is circulated by a wall-penetrating stirrer such that the ratio of circulation time to mean residence time of the reactive component is less than 1. The reaction can proceed under either reduced or increased pressure.After the silicon has been introduced into and onto the pores of the porous particles, the silicon-containing materials are transferred to reactor C or to a storage container for interim storage, or the material remains in reactor B. Phase 3: Post-treatment of the silicon-containing particles for functionalization and / or coating of the surface of the silicon-containing particles. Cooling of the particles to a defined temperature and removal of silicon-containing materials from reactor C, and preferably direct transfer to a storage container or direct filling into a suitable container.

[0057] In phase 1, porous particles are filled into a heated and / or vacuum-resistant and / or pressure-resistant reactor A. This filling can be done manually or automatically.

[0058] The filling of reactor A with porous particles can be carried out, for example, under an inert gas atmosphere or, preferably, ambient air. Suitable inert gases include, for example, hydrogen, helium, neon, argon, krypton, xenon, nitrogen, or carbon dioxide, or mixtures thereof, such as forming gas. Argon or, in particular, nitrogen are preferred.

[0059] Automatic filling can be carried out, for example, using a dosing screw, rotary valve, vibrating trough, disc dosing system, belt dosing system, vacuum dosing system, negative weighing or other dosing systems from, for example, a silo, a bag hopper or other container system.

[0060] The aim of pretreating the particles in reactor A during phase 1 is to remove air or oxygen, water, dispersants such as surfactants or alcohols, and impurities from the particles. This can be achieved by inerting with an inert gas, increasing the temperature to up to 1000 °C, reducing the pressure to down to 0.01 mbar, or a combination of these process steps. Suitable inert gases include, for example, hydrogen, helium, neon, argon, krypton, xenon, nitrogen, or carbon dioxide, or mixtures thereof, such as forming gas. Argon or, in particular, nitrogen are preferred.

[0061] The aim of pretreatment in Phase 1 can also be to modify the chemical surface properties of the porous particles with additional substances. These substances can be added before or after drying, and a further heating step can be performed before the material is transferred to reactor B. The substances can be added to the reactor in gaseous, solid, liquid, or solution form; mixtures, emulsions, suspensions, aerosols, or foams are also possible. Examples of such substances include carbon dioxide, water, sodium hydroxide, potassium hydroxide, hydrofluoric acid, phosphoric acid, nitric acid, hydrochloric acid, ammonia, ammonium dihydrogen phosphate, lithium nitrate, sodium nitrate, potassium nitrate, lithium chloride, sodium chloride, potassium chloride, lithium bromide, sodium bromide, potassium bromide, and alkanolates.

[0062] The transfer of the porous particles into another reactor or container can be achieved, for example, by a downpipe, continuous conveyor, flow conveyor / suction or pressure conveying system (e.g., vacuum conveyor, transport blower); mechanical conveyors (e.g., roller conveyor with drive, screw conveyor, circular conveyor, recirculating conveyor, bucket elevator, rotary valve, chain conveyor, scraper conveyor, belt conveyor, vibrating conveyor); gravity conveyors (e.g., chutes, roller conveyor, ball track, rail track), as well as by means of discontinuous conveyors: floor-mounted, rail-free (e.g., automated vehicle, hand pallet truck, electric pallet truck), automated guided vehicles (AGVs), air cushion vehicles, handcarts, electric carts, motorized vehicles (tractors, trolleys, forklifts), transfer cars, transfer pallet trucks, stacker cranes (with / without transfer units, curve-capable); floor-mounted, rail-mounted (e.g., industrial railway, railcar); floor-free (e.g., trolley conveyor), cranes (e.g.,Bridge crane, gantry crane, jib crane, tower crane), electric monorail (EMB), small container transport system; stationary (e.g. elevator, lifting platform and aerial work platform, step conveyor).

[0063] In phase 2, the pretreated material is preferably heated to a temperature of 100 to 1000 °C in reactor B, particularly preferably 250 to 600 °C and especially preferably 300 to 500 °C.

[0064] Reactor B is alternately or simultaneously perfused with a gas consisting of at least one inert gas and / or at least one reactive component consisting of at least one silicon precursor and / or at least one silicon-free precursor during temperature changes, at a set temperature, or while traversing a temperature profile. Different gas compositions are possible sequentially or are varied during Phase 2 within the specified composition range. The pore volume-related dosing rate of the gas phase containing the reactive component with at least one silicon precursor is defined as the mass of silicon [g] contained in the silicon precursor supplied per hour, relative to the absolute pore volume [cm³] of all porous particles introduced into Reactor B.Preferably, the silicon precursor is added at a rate of 0.1-2 g, particularly preferably 0.5 to 1.5 g Si per cm 3 < pore volume of the porous particles used per hour during the deposition process.

[0065] Alternatively, the area-related dosing rate of the gas phase containing the reactive component with at least one silicon precursor is defined as the mass of silicon [kg] contained in the silicon precursor supplied per hour, based on the largest flow cross-sectional area [m²] in the reaction zone. The cross-section is measured using the empty reactor. The reaction zone is the area in the reactor where the stirred particle bed is brought into contact with the reactive component and the precursor is decomposed.

[0066] The dosage rate of precursor is measured such that the ratio of the circulation time of the particle bed to the mean residence time of the reactive component in the reactor is always less than 1.

[0067] The gas phase can be added continuously or in bursts. The dosage rate can vary during the reaction time.

[0068] Preferably, in the rotationally symmetric reactor, the silicon precursor is added over the course of the deposition at a rate of 1 - 700 kg, particularly preferably 10 to 300 kg Si per m 2< of the outer surface of rotation per hour.

[0069] The reactor B is preferably supplied with such an amount of silicon-containing reactive component over the entire time of the thermal decomposition that, in relation to the weighed amount of porous particles, a sufficient amount of silicon is deposited for the target capacity of the silicon-containing material to be produced.

[0070] The heating of reactor B in phase 2 can be carried out, for example, with a constant heating rate or with several different heating rates. Heating rates can be adjusted by a person skilled in the art in each individual case, depending on the design of the process, for example, depending on the size of the reactor, the amount of porous particles in the reactor, the stirring technology, or the planned reaction time.

[0071] Preferably, reactor B is heated in phase 2 at heating rates of 1 to 100°C per minute, particularly preferably at heating rates of 2 to 50°C per minute.

[0072] The temperature at which the decomposition of the silicon precursor begins can depend, for example, on the porous particles used, the silicon precursor(s) used, and other boundary conditions of the decomposition, such as the partial pressure of the silicon precursor at the time of decomposition and the presence of other reactive components, such as catalysts, that influence the decomposition reaction.

[0073] During the decomposition of the silicon precursors in phase 2, the temperature can be kept constant or varied. The aim is the largely complete conversion of the silicon precursors during the contact time of the gas with the stirred bed, producing a silicon-containing material suitable for application.

[0074] The bed temperature during phases 2 and 3, and especially in the reaction zone of the reactor equipped with the wall-penetrating stirrer, is preferably in the range of 100 to 1000°C, particularly preferably from 250 to 600°C, and most preferably from 300 to 500°C. For example, the target temperatures for SiH₄ are preferably between 300 and 500°C, particularly preferably in the range of 320 to 450°C, and most preferably in the range of 320 to 430°C. The target temperatures for HSiCl₃ are preferably between 380 and 1000°C, particularly preferably in the range of 420 to 600°C. The target temperatures for H₂SiCl₂ are preferably between 350 and 800°C, particularly preferably in the range of 380 to 500°C.

[0075] In the case of the use of hydrocarbons in phase 3 and / or, in addition to silicon deposition during phase 2, as further reactive components that do not contain a silicon precursor, target temperatures are applied at which the decomposition of the hydrocarbons begins and carbon is deposited in pores and on the surface of the porous particles. Preferably, the target temperatures in this embodiment are selected in the range of 250 to 1000°C, particularly preferably from 350 to 850°C, and most preferably from 400 to 650°C.

[0076] In phase 2, the packed bed of porous particles is preferably continuously circulated. This circulation is achieved by one or more agitators or by a rotating motion of the reactor itself (e.g., an intensive mixer from Maschinenfabrik Gustav Eirich), or a combination thereof. The state of motion of the moving packed bed is characterized by Froude numbers between 1 and 10. Preferably, the Froude number is between 1 and 6, and particularly preferably between 1 and 4.

[0077] The thermal decomposition of the silicon precursors in the presence of porous particles preferably takes place at 0.05 MPa to 5 MPa, particularly preferably at 0.08 to 0.7 MPa.

[0078] The gas phase from phase 2 consists of an inert gas and / or at least one reactive component containing a silicon precursor and / or at least one silicon-free precursor, possibly with varying compositions. The one or more silicon precursors can generally be mixed or separated, or introduced into reactor B in a mixture with inert gas components or as pure substances. Preferably, the reactive component contains an inert gas component of 0 to 99%, particularly preferably at most 50%, more preferably at most 30%, and most preferably at most 5%, based on the partial pressure of the inert gas component relative to the total pressure of the reactive component under standard conditions (according to DIN 1343).

[0079] The silicon-containing reactive component contains at least one precursor which can react to form silicon under the chosen conditions, for example, thermal treatment.The precursor is preferably selected from the group containing silicon-hydrogen compounds such as monosilane SiH₄, disilane Si₂H₆, and higher linear, branched, or cyclic homologues; neo-pentasilane Si₅H₁₂, cyclo-hexasilane Si₆H₁₂; chlorine-containing silanes, such as trichlorosilane HSiCl₃, dichlorosilane H₂SiCl₂, chlorosilane H₃SiCl, tetrachlorosilane SiCl₄, hexachlorosilane Si₂Cl₆, and higher linear, branched, or cyclic homologues such as 1,1,2,2-tetrachlorodisilane Cl₂ HSi-SiHCl₂; chlorinated and partially chlorinated oligo- and polysilanes; and methylchlorosilanes, such as trichloromethylsilane MeSiCl₃ and dichlorodimethylsilane Me₂SiCl₂. 2 , Chlorotrimethylsilane Me 3 SiCl, Tetramethylsilane Me 4 Si, Dichloromethylsilane MeHSiCl 2 , 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 described silicon compounds.

[0080] In a specific embodiment of the process, the monosilane or mixtures of silanes, such as mixtures of monosilane SiH₄, trichlorosilane HSiCl₃, dichlorosilane H₂SiCl₂, monochlorosilane H₃SiCl₃, and tetrachlorosilane SiCl₄, where each component can be present in amounts from 0 to 99.9 wt%, are produced by a suitable process immediately before use in the reactor. These processes typically start with trichlorosilane HSiCl₃, which is rearranged over a suitable catalyst (e.g., AmberLyst™< A21DRY) to form the other components of the described mixture. The composition of the resulting mixture is primarily determined by work-up of the mixture obtained after one or more rearrangement steps at one or more different temperatures.Particularly preferred reactive components are selected from the group comprising monosilane SiH₄, oligomeric or polymeric silanes, in particular linear silanes of the general formula SiₙHₙ+2, where n can be an integer in the range of 2 to 10, as well as cyclic silanes of the general formula -[SiH₂]ₙ-, where n can be an integer in the range of 3 to 10, trichlorosilane HSiCl₃, dichlorosilane H₂SiCl₂ and chlorosilane H₃SiCl₂, wherein these can be used alone or as mixtures, with particular preference being SiH₄, HSiCl₃ and H₂SiCl₂ used alone or in mixtures.

[0081] During the dosing of the reactive components into the reactors, the components of the reactive component can be in gaseous, liquid or sublimable solid form, for example.

[0082] The reactive component is preferably gaseous, liquid, solid (e.g., sublimable), or a mixture of substances, optionally consisting of substances in different states of matter. In one variant of the process, the reactive component is added directly to the bed of porous particles in the reactor, for example, from below, from the side, or via a special stirrer.

[0083] Furthermore, the reactive components in phases 2 and / or 3 may also contain additional reactive elements, such as dopants based on compounds containing boron, nitrogen, phosphorus, arsenic, germanium, iron, or nickel. The dopants are preferably selected from the group comprising ammonia (NH₃), diborane (B₂H₆), phosphine (PH₃), germanium (GeH₄), arsenic (AsH₃), iron pentacarbonyl (Fe(CO)₄), and nickel tetracarbonyl (Ni(CO)₄).

[0084] Other reactive components that may be present in the gas phase include hydrogen or hydrocarbons selected from the group containing aliphatic hydrocarbons with 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, such as methane, ethane, propane, butane, pentane, isobutane, hexane, cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane; Unsaturated hydrocarbons with 1 to 10 carbon atoms, such as ethene, acetylene, propene, methylacetylene, butylene, butynes ​​(1-butyne, 2-butyne), isoprene, 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, cymene, nitrobenzene, chlorobenzene, pyridine, anthracene or phenanthrene, myrcene, geraniol, thioterpineol, norbornane, borneol, iso-borneol, bornane, camphor, limonene, terpinene, pinene, pinane, carene, phenol, aniline, anisole, furan, furfural, furfuryl alcohol, hydroxymethylfurfural, bishydroxymethylfuran, and mixed fractions containing a variety of such compounds, such as from natural gas condensates, petroleum distillates or coke oven condensates, mixed fractions from the product streams of a fluid catalytic cracker (FCC), steam cracker or a Fischer-Tropsch synthesis plant, or more generally, hydrocarbon-containing material streams from the wood, natural gas, petroleum and Coal processing.

[0085] In a particularly preferred embodiment, in a first reaction cycle in phase 2, a reactive component containing at least one silicon precursor is applied, and in a second reaction cycle in phase 2, a reactive component containing at least one hydrocarbon, which is preferably silicon-free, is applied. By repeating these two steps, for example, a silicon-containing material can be obtained which has no outwardly facing free silicon surface.

[0086] Optionally, in a preceding reaction cycle in phase 2, another hydrocarbon-containing, silicon-free reactive component is used. This yields, for example, a silicon-containing material that has a carbon layer between the porous particles and the deposited silicon, and which may also have an outer carbon layer, thus eliminating any outwardly facing free silicon surface.

[0087] In a preferred embodiment, the temperature, pressure, pressure changes or differential pressure measurements, and gas flow measurements in reactor B are determined using common measuring instruments and methods. After standard calibration, different measuring instruments yield the same measurement results.

[0088] The reaction in phase 2 is preferably monitored analytically to detect the end of the reaction and thus minimize reactor occupancy time. Methods for monitoring the reaction progress include, for example, temperature measurements to detect exothermic or endothermic reactions, to determine the reaction progress by observing changing ratios of solid to gaseous reactor components, and by other methods that allow observation of the changing composition of the gas phase during the reaction. In a preferred embodiment of the method, the composition of the gas phase is determined by a gas chromatograph and / or thermal conductivity detector and / or an infrared spectrometer and / or a Raman spectrometer and / or a mass spectrometer.In a preferred embodiment, the hydrogen content and / or any chlorosilanes present are determined using a thermal conductivity detector and a gas chromatograph or gas infrared spectroscope. In another preferred variant of the process, a technical component is used that enables the separation of hydrogen and silane. This separation can be achieved, for example, by filtration or membrane processes (solution-diffusion and hydrodynamic models), adsorption, chemisorption, absorption or chemisorption, or molecular sieves (e.g., zeolite). In the case of hydrogen as a gaseous reaction product, this component enables a closed-loop gas process. Here, the gas discharged in phase 2 is purified, or the proportion of silicon-containing reactive component is increased, and then returned to the reactor until the desired amount of silicon has been deposited.In another embodiment, the gas is separated into its components and disposed of in this way.

[0089] In a further preferred embodiment of the process, reactor B or the gas discharge point is equipped with a technical device for removing any condensable or resublimable byproducts that may occur. In a particularly preferred embodiment, silicon tetrachloride is condensed and removed separately from the silicon-containing material.

[0090] In a preferred embodiment of the method, the dosing processes in phase 2 are repeated multiple times, wherein the silicon precursor applied in phase 2 can be the same or different each time, and mixtures of several silicon precursors are also possible. Likewise, the silicon-free reactive component applied in phase 2 can be the same or different each time, or consist of mixtures of different reactive components. After the individual dosing processes in phase 2 have been repeated multiple times, the process in reactor B is terminated by transferring the silicon-containing particles to reactor C.

[0091] In phase 3 of the process, the silicon-containing particles in reactor C can be post-treated and / or deactivated and / or coated. Preferably, reactor C is purged with oxygen, in particular with a mixture of inert gas and oxygen. This allows, for example, the modification and / or functionalization and / or deactivation of the surface of the silicon-containing material. For example, a reaction of any reactive groups present on the surface of the silicon-containing material can be achieved. Preferably, a mixture of nitrogen, oxygen, and optionally alcohols and / or water is used, which preferably contains at most 20 vol%, more preferably at most 10 vol%, and more preferably at most 5 vol% oxygen, and preferably at most 100 vol%, more preferably at most 10 vol%, and more preferably at most 1 vol% water.This step is preferably carried out at temperatures of no more than 250°C, particularly preferably at no more than 100°C, and especially preferably at no more than 50°C. The deactivation of the particle surfaces can also be carried out with a gas mixture containing an inert gas and alcohols. Nitrogen and isopropanol are preferably used. However, methanol, ethanol, butanols, pentanols, or longer-chain and branched alcohols and diols can also be used.

[0092] The particles can also be deactivated by dispersion in a liquid solvent or solvent mixture. This can contain, for example, isopropanol or an aqueous solution.

[0093] Alternatively, the deactivation of the particles in phase 3 can also be carried out by coating with C-, Al-, B-containing precursors at temperatures of 200-800°C and optionally subsequent treatment with an oxygen-containing atmosphere.

[0094] Examples of aluminium-containing precursors include trimethylaluminium ((CH 3 ) 3 Al), aluminium 2,2,6,6-tetramethyl-3,5-heptanedionate (Al(OCC(CH 3 ) 3 CHCOC(CH 3 ) 3 ) 3 ), tris-(dimethylamido)-aluminium (Al(N(CH 3 ) 2 ) 3 ) and aluminium triisopropanolate (C 9 H 21 AlO 3 ).

[0095] Boron-containing precursors such as borane (BH3), triisopropyl borate ([(CH3)2CHO]3B), triphenylborane ((C6H5)3B), and tris-(pentafluorophenyl)borane (C6F5)3B) can be used. In phase 3, however, post-coating of the particles with solid electrolytes via thermal decomposition of, for example, tert-butyllithium and trimethyl phosphate can also be introduced.

[0096] In phase 3 of the process, the silicon-containing materials are removed from reactor C, if necessary while maintaining an inert gas atmosphere present in reactor C. This can be done, for example, using the following discharge methods: pneumatically (by means of positive or negative pressure); mechanically (rotary valve, disc discharge, discharge screw or agitator in the reactor, belt discharge); gravimetrically (double flap or ball valve, possibly supported by vibration).

[0097] One or more hydrocarbons are preferred as silicon-free reactive components. Through thermal decomposition of the hydrocarbons, carbon can generally be deposited in pores and on the surface of the porous particles. Examples of hydrocarbons are aliphatic hydrocarbons with 1 to 10 carbon atoms, in particular 1 to 6 carbon atoms, preferably methane, ethane, propane, butane, pentane, isobutane, hexane, cyclopropane, cyclobutane, cyclopentane, cyclohexane and cycloheptane; unsaturated hydrocarbons with 1 to 10 carbon atoms, such as ethene, acetylene, propene or butene, isoprene, butadiene, divinylbenzene, vinylacetylene, cyclohexadiene, cyclooctadiene; cyclic unsaturated hydrocarbons, such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, cyclohexadiene, cyclopentadiene, dicyclopentadiene and norbornadiene; aromatic hydrocarbons, such as benzene, toluene, p-, m-, o-xylene, styrene (vinylbenzene).Ethylbenzene, diphenylmethane and naphthalene, other aromatic hydrocarbons such as phenol, o-, m-, p-cresol, cymene, nitrobenzene, chlorobenzene, pyridine, anthracene and phenanthrene, myrcene, geraniol, thioterpineol, norbornane, borneol, iso-borneol, bornane, camphor, limonene, terpinene, pinene, pinane, carene, phenol, aniline, anisole, furan, furfural, furfuryl alcohol, hydroxymethylfurfural, bishydroxymethylfuran and mixed fractions containing a variety of such compounds, such as from natural gas condensates, petroleum distillates or coke oven condensates, mixed fractions from the product streams of a fluid catalytic cracker (FCC), steam cracker or a Fischer-Tropsch synthesis plant, or more generally hydrocarbon-containing material streams from the Processing of wood, natural gas, petroleum and coal.

[0098] The silicon-free reactive components, namely those containing one or more hydrocarbons but no silicon precursor, preferably contain no further component or one or more inert gases and / or one or more reactive components, such as hydrogen, and / or one or more dopants. Dopants are, for example, compounds containing boron, nitrogen, phosphorus, arsenic, germanium, iron, or nickel. The dopants are preferably selected from the group comprising ammonia (NH₃), diborane (B₂H₆), phosphine (PH₃), germanium (GeH₄), arsane (AsH₃), and nickel tetracarbonyl (Ni(CO)₄).

[0099] For the purposes of this application, reactor types preferably selected from the group comprising retort furnaces, tubular reactors, stirred bed reactors, stirred tank reactors, and autoclaves are used. Stirred reactors and autoclaves are particularly preferred, especially stirred reactors and most preferably stirred tank reactors.

[0100] In a specific variant of the process, reactors A, B, and C are the same vessel. It is not impossible that reactors A, B, and C are the same vessel. In two particular embodiments of the process, the cascade reactor consists of only two interdependent reactors. In the first embodiment, phases 1 and 2 are carried out in the same reactor. In the second embodiment, phases 2 and 3 are carried out in one reactor. In both cases, the reactors can have different temperature zones and can be operated at normal pressure, as well as at reduced or increased pressure.

[0101] A reactor can be temperature-controlled, pressure-resistant, and vacuum-resistant simultaneously; all combinations are possible. However, a reactor can also fulfill only one of the aforementioned characteristics.

[0102] Technical requirements for the reactors and optional features for special variants of the invention: Reactor A: The reactor is at least temperature-controlled. The reactor can be vacuum-resistant. System for preheating, drying, and inerting the porous particles. A system for the targeted addition / dosing of the porous particles (technical description see Phase 1) can be connected. A system for drying or removing impurities from the porous particles can be connected, allowing the removal of condensable or resublimable substances. A system can be connected to transfer the porous particles to reactor B (technical description see Phase 1). Reactor B: The reactor is at least temperature-controlled. Contains a stirrer according to the invention. System for dosing reaction gas. System for removing reaction gas. For process simplification, a hydrogen separator (technical description, see Phase 2) can be connected.To remove condensable or resublimable byproducts occurring in the gaseous reaction products, a container can be connected that allows the byproducts to be removed by condensation or resublimation. A system can be connected to transfer the material to reactor C or a storage container (see Phase 1 for technical description). Reactor C: The reactor is temperature-controlled. System for removing condensable or resublimable byproducts. A container can be connected that allows the byproducts to be removed by condensation or resublimation. System for adding reaction gas for functionalization. System for removing reaction gas. A system can be connected to transfer the material to a storage container (see Phase 3 for technical description).

[0103] A temperature-controlled reactor is generally a reactor that can be operated in such a way that the temperature inside the reactor can be set, for example, in the range between -40 and 1000 °C. Smaller temperature ranges are possible.

[0104] A cascade reactor system, as defined in the application, is a connection of at least two reactors. There is no upper limit to the number of reactors. The number of reactors A, B, and C relative to each other, as well as their sizes, shapes, materials, and configurations, can vary. A person skilled in the art can coordinate the number of reactors and their sizes to maximize the overall efficiency of the cascade reactor system's output. The reactors can be directly connected or physically separated, with feeding carried out via movable storage containers. It is also conceivable that several reactors B are interconnected, with each reaction step taking place in a separate reactor B.

[0105] The porous particles and the resulting silicon-containing material can generally be present as a stationary bed or in a moving, mixed state during the process. A moving mixture of the porous particles or the resulting silicon-containing material in reactors A, B, and C is preferred. However, the particles must be mixed during the thermal decomposition of the reactive components in phase 2. This ensures, for example, homogeneous contact of all porous particles with the reactive components or a homogeneous temperature distribution of the bed. The circulation of the particles can be achieved, for example, by agitators within the reactor or by moving the entire reactor around a stirrer.

[0106] Another preferred design of reactors A, B, and C are stationary reactors with moving agitators for circulation. The purpose of the circulation is to bring the porous solid into contact with the gaseous reactive component as uniformly as possible. Preferred geometries for this purpose are cylindrical reactors, conical reactors, spherical, polyhedral, rotationally symmetrical reactors, or combinations thereof. The movement of the agitator is preferably rotary. Other forms of movement are also suitable. The agitator is preferably driven by an agitator shaft, with one or more agitators being present per shaft. Several agitator shafts can be incorporated into reactors A, B, and C, each of which can have one or more agitators. The main reactor axis is preferably oriented horizontally or vertically.In a further preferred embodiment, the agitator shafts are installed horizontally or vertically in a reactor of any orientation. For vertically operated reactors A, B, and C, preferred designs include, for example, a main agitator shaft in which one or more agitators mix the bulk material by means of a rotational movement. Designs are also possible in which two or more agitator shafts operate in parallel. Designs are also possible in which two or more agitator shafts are not operated in parallel. Another design for a vertically operated reactor A, B, or C is characterized by the use of a screw conveyor. The screw conveyor preferably conveys the bulk material centrally. A further design according to the invention is the screw conveyor rotating along the edge of the reactor (Nauta® mixer, Hosokawa). A further preferred design is a planetary mixing system or a spiral agitator system.For horizontally operated reactors A, B, or C, preferred designs include, for example, one or more agitators driving a main agitator shaft to mix the bulk material by means of a rotational movement. Designs are also possible in which two or more agitator shafts run in parallel. Designs in which two or more agitator shafts are not operated in parallel are also preferred. For vertically operated reactors A, B, or C, preferred agitators are selected from the group consisting of helical agitators, spiral agitators, anchor agitators, or, more generally, agitators that convey the bulk material axially or radially, or both axially and radially, and that exhibit wall penetration according to the invention. Wexhibiting. In horizontally operated reactors A, B, or C, several agitators are preferably arranged on one shaft. Examples of agitator designs according to the invention for horizontally operated reactors are plowshares, paddles, blade agitators, spiral agitators, or, more generally, agitators that convey the bulk material both axially and radially and exhibit wall penetration according to the invention. W The wall penetration can be reduced by adding scrapers to the agitator. In addition to moving agitators, rigid internals, such as baffles, are also possible for reactor A, B, or C.

[0107] For the construction of reactor A, B, or C for carrying out the process according to the invention, any material is suitable that exhibits the necessary mechanical strength and chemical resistance under the respective process conditions. With regard to chemical resistance, reactor A, B, or C can consist of either suitable solid materials or chemically non-resistant materials (pressure-bearing) with special coatings or plating of the parts in contact with the medium.

[0108] The materials are selected according to the invention from the group containing: Metallic materials that (according to DIN CEN ISO / TR 15608) correspond to material groups 1 to 11 for steels, groups 31 to 38 for nickel and nickel alloys, groups 51 to 54 for titanium and titanium alloys, groups 61 and 62 for zirconium and zirconium alloys, and groups 71 to 76 for cast iron; ceramic materials made of oxide ceramics in single-component systems, such as aluminum oxide, magnesium oxide, zirconium oxide, titanium dioxide (capacitor material), as well as multi-component systems, such as aluminum titanate (mixture of aluminum and titanium oxide), mullite (mixture of aluminum and silicon oxide), lead zirconate titanate (piezoceramic), or dispersion ceramics such as zirconium oxide-reinforced aluminum oxide (ZTA - Zirconia Toughened Aluminum Oxide) - Al₂O₃ / ZrO₂). Non-oxide ceramics, such as carbides, for example silicon carbide and boron carbide, nitrides, for example silicon nitride, aluminum nitride, boron nitride and titanium nitride,Borides and silicides, as well as their mixtures and composite materials, belonging to the groups of particle composites, such as hard metal, ceramic composites, concrete and polymer concrete; fiber composites, such as glass fiber reinforced glass, metal matrix composites (MMC), fiber cement, carbon fiber reinforced silicon carbide, self-reinforced thermoplastics, reinforced concrete, fiber-reinforced concrete, fiber-reinforced plastics, such as carbon fiber reinforced plastic (CFRP), glass fiber reinforced plastic (GFRP) and aramid fiber reinforced plastic (AFRP), ceramic matrix composites (CMC), penetration composites, such as metal matrix composites (MMC), dispersion-strengthened aluminum alloys or dispersion-hardened nickel-chromium superalloys; and layered composites, such as bimetals, titanium graphite composites, and composite panels. and tubes, glass fiber reinforced aluminum and sandwich constructions,and structural composite materials.

[0109] The porous particles for the process according to the invention are preferably selected from the group consisting of 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 such as silicon dioxide, aluminum oxide, silicon-aluminum mixed oxides, magnesium oxide, lead oxides and zirconium oxide, carbides such as silicon carbides and boron carbides, nitrides such as 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.

[0110] 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 2 with z = 0.2 to 1, non-stoichiometric carbon nitrides CN 2 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, boron nitridooxides BN z O r with z = 0.1 to 1 and r = 0.1 to 1, where 3 ≥ r*2 + z*3, boron carbonitridooxides 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, silicon carbonoxides Si x CO z with x = 0.1 to 2 and z = 0.1 to 2, where x*4 + 4 ≥ z*2, silicon carbonitrides Si x CN z with x = 0.1 to 3 and z = 0.1 to 4, where x*4 + 4 ≥ z*3, 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 borocarbooxides 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, 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 ,

[0111] Aluminiumborosilicocarbonitridooxide 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.

[0112] Preferably, the porous particles have a density of 0.1 to 7 g / cm³ determined by helium pycnometry, and particularly preferably of 0.3 to 3 g / cm³. This is advantageous for increasing the volumetric capacity (mAh / cm³) of lithium-ion batteries.

[0113] Preferably, amorphous carbons, silicon dioxide, boron nitride, silicon carbide and silicon nitride or mixed materials based on these materials are used as porous particles; the use of amorphous carbons, boron nitride and silicon dioxide is particularly preferred.

[0114] The porous particles have a volume-weighted particle size distribution with diameter percentiles d50 of preferably ≥ 0.5 µm, particularly preferably ≥ 1.5 µm, and most preferably ≥ 2 µm. The diameter percentiles d50 are preferably ≤ 20 µm, particularly preferably ≤ 12 µm, and most preferably ≤ 8 µm.

[0115] The volume-weighted particle size distribution of the porous particles preferably lies 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.

[0116] The porous particles have a volume-weighted particle size distribution with diameter percentiles d10 of preferably ≤ 10 µm, particularly preferably ≤ 5 µm, particularly preferably ≤ 3 µm and most preferably ≤ 2 µm. The diameter percentiles d10 are preferably ≥ 0.2 µm, particularly preferably ≥ 0.5 µm and most preferably ≥ 1 µm.

[0117] The porous particles have a volume-weighted particle size distribution with diameter percentiles d90 of preferably ≥ 4 µm and particularly preferably ≥ 8 µm. The diameter percentiles d90 are preferably ≤ 18 µm, particularly preferably ≤ 15 µm, and most preferably ≤ 13 µm.

[0118] 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.

[0119] The volume-weighted particle size distribution of the silicon-containing materials producible according to the inventive method has a width d 90 - d 10 of preferably ≥ 0.6 µm, particularly preferably ≥ 0.8 µm and most preferably ≥ 1.0 µm.

[0120] 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.

[0121] The porous particles are preferably in the form of individual particles. The particles can be, for example, isolated or agglomerated. The porous particles are preferably not aggregated and preferably not agglomerated. Aggregated generally means that during the production of the porous particles, primary particles are initially formed and grow together, and / or primary particles are linked together, for example, via covalent bonds, thus forming aggregates. Primary particles are generally isolated particles. Aggregates or isolated particles can form agglomerates. Agglomerates are a loose clumping of aggregates or primary particles that are linked together, for example, via van der Waals interactions or hydrogen bonds. Agglomerated aggregates can be easily broken down back into aggregates using conventional kneading and dispersing processes.These methods cannot, or can only partially, break down aggregates into primary particles. The presence of porous particles in the form of aggregates, agglomerates, or isolated particles can be visualized, for example, using conventional scanning electron microscopy (SEM). In contrast, static light scattering methods for determining the particle size distributions or particle diameters of matrix particles cannot distinguish between aggregates and agglomerates.

[0122] The porous particles can have any morphology, for example, splintery, platy, spherical, or needle-shaped, with splintery or spherical particles being preferred. The morphology can be characterized, for example, by the sphericity ψ or the sphericity S. According to Wadell's definition, the sphericity ψ is the ratio of the surface area of ​​a sphere of the same 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 for the process according to the invention have a sphericity ψ of preferably 0.3 to 1.0, particularly preferably 0.5 to 1.0, and most preferably 0.65 to 1.0.

[0123] The sphericity S is the ratio of the circumference of an equivalent circle with the same area A as the projection of the particle projected onto a surface and the measured circumference U of this projection: S = 2 πA / U .In the case of an ideally circular particle, S the value 1. For the porous particles for the process according to the invention, the sphericity is S in the range of preferably 0.5 to 1.0 and particularly preferably from 0.65 to 1.0, based on the percentiles S 10 to S 90 of the sphericity number distribution. The measurement of sphericity S This is done, for example, by taking pictures of individual particles with an optical microscope or, for particles < 10 µm, preferably with a scanning electron microscope, by graphical evaluation using image analysis software, such as ImageJ.

[0124] The porous particles preferably have a gas-accessible pore volume of ≥ 0.2 cm³ / g, particularly preferably ≥ 0.6 cm³ / g, and most preferably ≥ 1.0 cm³ / g. This is advantageous for obtaining high-capacity lithium-ion batteries. The gas-accessible pore volume was determined by gas sorption measurements with nitrogen according to DIN 66134.

[0125] The porous particles are preferably open-pored. Open-pored generally means that pores are connected to the surface of the particles, for example via channels, and are preferably able to exchange substances with the environment, particularly gaseous compounds. This can be demonstrated by gas sorption measurements (evaluation according to Brunauer, Emmett and Teller, "BET"), i.e., by determining the specific surface area. The porous particles have specific surface areas of preferably ≥ 50 m² / g, particularly preferably ≥ 500 m² / g, and most preferably ≥ 1000 m² / g. The BET surface area is determined according to DIN 66131 (using nitrogen).

[0126] The pores of the porous particles can have any diameter, generally ranging from macropores (above 50 nm), mesopores (2–50 nm), and micropores (less than 2 nm). The porous particles can be used in any mixture of different pore types. Preferred are porous particles with less than 30% macropores, based on the total pore volume; particularly preferred are porous particles without macropores; and most preferred are porous particles with at least 50% pores with a mean pore diameter of less than 5 nm. The porous particles particularly preferentially exhibit pores with a pore diameter of less than 2 nm (determination method: pore size distribution according to BJH (gas adsorption) according to DIN 66134 in the mesopore range and according to Horvath-Kawazoe (gas adsorption) according to DIN 66135 in the micropore range; the evaluation of the pore size distribution in the macropore range is carried out by mercury porosimetry according to DIN ISO 15901-1).

[0127] Porous particles with a gas-inaccessible pore volume of less than 0.3 cm³ / g and particularly less than 0.15 cm³ / g are preferred. This also allows for an increase in the capacity of lithium-ion batteries. The gas-inaccessible pore volume can be determined using the following formula: Gas-inaccessible pore volume = 1 / pure material density - 1 / skeletal density.

[0128] The pure material density is a theoretical density of the porous particles, based on the phase composition or the density of the pure substance (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 dioxide is 2.203 g / cm³, that of boron nitride is 2.25 g / cm³, that of silicon nitride is 3.44 g / cm³, and that of silicon carbide is 3.21 g / cm³. The skeletal density is the actual density of the porous particles (gas-accessible) as determined by helium pycnometry.

[0129] For clarification, it should be noted that the porous particles are distinct from the silicon-containing material. The porous particles serve as the starting material for the production of the silicon-containing material. Preferably, there is no silicon in the pores of the porous particles, and generally no silicon on the surface of the porous particles, in particular no silicon obtained by depositing silicon precursors.

[0130] The silicon-containing material obtainable by deposition of silicon in pores and on the surface of the porous particles according to the inventive method has a volume-weighted particle size distribution with diameter percentiles d50 preferably in a range of 0.5 to 20 µm. Preferably, the d50 value is at least 1.5 µm, and particularly preferably at least 2 µm. The diameter percentiles d50 are preferably at most 13 µm and particularly preferably at most 8 µm.

[0131] The volume-weighted particle size distribution of the silicon-containing material preferably lies 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 and d 90 ≤ 12.0 µm.

[0132] The silicon-containing material has a volume-weighted particle size distribution with diameter percentiles d10 of preferably ≤ 10 µm, particularly preferably ≤ 5 µm, particularly preferably ≤ 3 µm and most preferably ≤ 1 µm. The diameter percentiles d10 are preferably ≥ 0.2 µm, particularly preferably ≥ 0.4 µm and most preferably ≥ 0.6 µm.

[0133] The silicon-containing material has a volume-weighted particle size distribution with diameter percentiles d90 of preferably ≥ 5 µm and particularly preferably ≥ 10 µm. The diameter percentiles d90 are preferably ≤ 20 µm, particularly preferably ≤ 15 µm and most preferably ≤ 12 µm.

[0134] The volume-weighted particle size distribution of the silicon-containing material has a width d90-d10 of preferably ≤ 15.0 µm, particularly 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 d90-d10 of preferably ≥ 0.6 µm, particularly preferably ≥ 0.8 µm, and most preferably ≥ 1.0 µm.

[0135] The silicon-containing material is preferably present in particle form. The particles can be isolated or agglomerated. The silicon-containing material is preferably not aggregated and preferably not agglomerated. The terms isolated, agglomerated, and not agglomerated have already been defined above with regard to the porous particles. The presence of silicon-containing materials in the form of aggregates or agglomerates can be visualized, for example, using conventional scanning electron microscopy (SEM).

[0136] The silicon-containing material can have any morphology, for example splintery, platy, spherical or needle-shaped, with splintery or spherical particles being preferred.

[0137] According to Wadell's definition, sphericity ψThe ratio of the surface area of ​​a sphere of the same volume to the actual surface area of ​​a body. In the case of a sphere, ψ the value 1. According to this definition, the silicon-containing materials accessible according to the inventive method have a sphericity ψ preferably from 0.3 to 1.0, particularly preferably from 0.5 to 1.0 and most preferably from 0.65 to 1.0.

[0138] The sphericity S is the ratio of the circumference of an equivalent circle with the same area A as the projection of the particle projected onto a surface and the measured circumference U of this projection: S = 2 πA / U . In the case of an ideally circular particle, S the value 1. For the silicon-containing materials accessible according to the inventive method, the sphericity is Sin the range of preferably 0.5 to 1.0 and particularly preferably from 0.65 to 1.0, based on the percentiles S 10 to S 90 of the sphericity number distribution. The measurement of sphericity S This is done, for example, by taking pictures of individual particles with an optical microscope or, for particles smaller than 10 µm, preferably with a scanning electron microscope, by graphical evaluation using image analysis software such as ImageJ.

[0139] The cycling stability of lithium-ion batteries can be further increased by modifying the morphology, material composition, and especially the specific surface area or internal porosity of the silicon-containing material.

[0140] The silicon-containing material preferably contains 10 to 90 wt.%, more preferably 20 to 80 wt.%, particularly preferably 30 to 60 wt.% and especially preferably 40 to 50 wt.% of porous particles, based on the total weight of the silicon-containing material.

[0141] The silicon-containing material preferably contains 10 to 90 wt.%, more preferably 20 to 80 wt.%, particularly preferably 30 to 60 wt.% and especially preferably 40 to 50 wt.% silicon obtained via deposition from the silicon precursor, based on the total weight of the silicon-containing material (determination preferably by elemental analysis, such as ICP-OES).

[0142] If the porous particles contain silicon compounds, for example in the form of silicon dioxide, the aforementioned wt% values ​​for the silicon obtained via deposition from the silicon precursor can be determined by subtracting the silicon mass of the porous particles, determined by elemental analysis, from the silicon mass of the silicon-containing material, determined by elemental analysis, and dividing the result by the mass of the silicon-containing material.

[0143] The volume of silicon deposited in porous particles is calculated by dividing the mass fraction of the silicon obtained via deposition from the silicon precursor in the total mass of the silicon-containing material by the density of silicon (2.336 g / cm³).

[0144] The pore volume P of silicon-containing materials is the sum of the 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 according to DIN 66134.

[0145] The gas-inaccessible pore volume of the silicon-containing material can be determined using the formula: Gas-inaccessible pore volume = 1 / skeletal density - 1 / pure material density.

[0146] The pure material density of a silicon-containing material is a theoretical density calculated by summing the theoretical pure material densities of the components within the silicon-containing material and multiplying each sum by its respective weight-related percentage of the total material. For example, for a silicon-containing material where silicon is deposited on a porous particle, the following formula applies: Pure material density = theoretical pure material density of silicon * percentage of silicon by weight + theoretical pure material density of the porous particles * percentage of porous particles by weight.

[0147] 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 dioxide is 2.203 g / cm³, that of boron nitride is 2.25 g / cm³, that of silicon nitride is 3.44 g / cm³, and that of silicon carbide is 3.21 g / cm³.

[0148] The pore volume P of the silicon-containing materials is preferably in the range of 0 to 400 vol.%, particularly preferably in the range of 100 to 350 vol.% and especially preferably in the range of 200 to 350 vol.%, based on the volume of the silicon contained in the silicon-containing material obtained from the deposition from the silicon precursor.

[0149] 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 in the silicon-containing material can generally range from 0 (no gas-accessible pores) to 1 (all pores are gas-accessible). Preferably, the ratio of the volume of gas-accessible to gas-inaccessible porosity in the silicon-containing material is in the range of 0 to 0.8, particularly preferably in the range of 0 to 0.3, and most preferably in the range of 0 to 0.1.

[0150] 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 mixture of different pore types. Preferably, the silicon-containing material contains at most 30% macropores, based on the total pore volume. Particularly preferred is a silicon-containing material without macropores, and most preferably is a silicon-containing material with at least 50% pores, based on the total pore volume, with a mean pore diameter of less than 5 nm. Particularly preferred is the silicon-containing material having exclusively pores with a diameter of at most 2 nm.

[0151] The silicon-containing material has silicon structures which in at least one dimension have structure sizes of preferably at most 1000 nm, more preferably less than 100 nm, particularly preferably less than 5 nm (determination method: scanning electron microscopy (SEM) and / or high-resolution transmission electron microscopy (HR-TEM)).

[0152] Preferably, the silicon-containing material comprises silicon layers with a thickness of less than 1000 nm, more preferably less than 100 nm, and 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 may also contain silicon in the form of particles. The silicon particles have a diameter of preferably not more than 1000 nm, more preferably less than 100 nm, and particularly preferably less than 5 nm (determination method: scanning electron microscopy (SEM) and / or high-resolution transmission electron microscopy (HR-TEM)). The specification for the silicon particles preferably refers to the diameter of the circumference of the particles as seen in the microscopic image.

[0153] The silicon-containing material preferably has a specific surface area of ​​at most 100 m² / g, particularly preferably less than 30 m² / g, and especially preferably less than 10 m² / g. The BET surface area is determined according to DIN 66131 (with nitrogen). Therefore, when the silicon-containing material is used as an active material in anodes for lithium-ion batteries, SEI formation can be reduced and the initial Couloumb efficiency increased.

[0154] Furthermore, the silicon deposited from the silicon precursor in the silicon-containing material can contain dopants, for example, selected from the group containing Li, Fe, Al, Cu, Ca, K, Na, S, Cl, 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 dopant content in the silicon-containing material is preferably at most 1 wt.% and particularly preferably at most 100 ppm, based on the total weight of the silicon-containing material, determinable by ICP-OES.

[0155] The silicon-containing material generally exhibits surprisingly high stability under compressive and / or shear stress. This compressive and shear stability is demonstrated, for example, by the fact that the silicon-containing material shows no or only minor changes in its porous structure under compressive (e.g., during electrode compaction) or shear stress (e.g., during electrode preparation) conditions as seen in SEM scans.

[0156] The silicon-containing material may optionally contain additional elements, such as carbon. Preferably, the carbon is present in the form of thin layers with a thickness of at most 1 µm, preferably less than 100 nm, particularly preferably less than 5 nm, and most preferably less than 1 nm (determinable by SEM or HR-TEM). The carbon layers can be present both within the pores and on the surface of the silicon-containing material. The sequence of different layers in the silicon-containing material, achieved by corresponding repetitions of the alternating dosage of different precursors, as well as their number, is arbitrary. Thus, a layer of another material, different from the porous particles, such as carbon, may first be present on the porous particles, followed by a silicon layer or a layer of silicon particles.Furthermore, on the silicon layer or on the layer of silicon particles, there may again be a layer of another material, which may be different from or the same as the material of the porous particles, regardless of whether there is another layer of a material different from the material of the porous particles between the porous particles and the silicon layer or the layer consisting of silicon particles.

[0157] The silicon-containing material preferably contains ≤ 50 wt.%, particularly preferably ≤ 40 wt.%, and especially preferably ≤ 20 wt.% of additional elements. The silicon-containing material preferably contains ≥ 1 wt.%, particularly preferably ≥ 3 wt.%, and especially preferably ≥ 2 wt.% of additional elements. The values ​​in wt.% refer to the total weight of the silicon-containing material. In an alternative embodiment, the silicon-containing material contains no additional elements.

[0158] Furthermore, the use of the silicon-containing material as an active material in anode materials for anodes of lithium-ion batteries and the use of such anodes for the manufacture of lithium-ion batteries is disclosed.

[0159] The anode material is preferably based on a mixture comprising the etched silicon-containing material accessible according to the inventive method, 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.

[0160] By incorporating additional electrically conductive components into the anode material, the contact resistances within the electrode and between the electrode and the current collector can be reduced, thus improving the current-carrying capacity of the lithium-ion battery according to the invention. Preferred additional electrically conductive components include, for example, conductive carbon black, carbon nanotubes, or metallic particles such as copper.

[0161] The anode material preferably contains 0 to 95 wt.%, particularly preferably 0 to 40 wt.% and most preferably 0 to 25 wt.% of one or more further electrically conductive components, based on the total weight of the anode material.

[0162] The etched silicon-containing material can be included in the anodes for lithium-ion batteries preferably 5 to 100 wt.%, particularly preferably 30 to 100 wt.% and most preferably 60 to 100 wt.%, based on the total active material contained in the anode material.

[0163] Preferred binders are polyacrylic acid or its alkali salts, particularly lithium or sodium salts, polyvinyl alcohols, cellulose or cellulose derivatives, polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, polyimides, particularly polyamide-imides, or thermoplastic elastomers, particularly ethylene-propylene-diene terpolymers. The alkali salts, particularly lithium or sodium salts, of the aforementioned binders are also particularly preferred. All or preferably a proportion of the acid groups of a binder may 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 may also be used.

[0164] Generally, natural or synthetic graphite can be used. The graphite particles preferably have a volume-weighted particle size distribution between the diameter percentiles d10 > 0.2 µm and d90 < 200 µm.

[0165] Examples of additives include pore-forming agents, dispersing agents, leveling agents or dopants, for example elemental lithium.

[0166] Preferred formulations for the anode material preferably contain 5 to 95 wt.% of the silicon-containing material, 0 to 90 wt.% of other electrically conductive components, 0 to 90 wt.% graphite, 0 to 25 wt.% binder and 0 to 80 wt.% additives, wherein the values ​​in wt.% refer to the total weight of the anode material and the proportions of all components of the anode material add up to 100 wt.%.

[0167] The processing of the components of the anode material into an anode ink or paste preferably takes place in a solvent, preferably selected from the group comprising water, hexane, toluene, tetrahydrofuran, N-methylpyrrolidone, N-ethylpyrrolidone, acetone, ethyl acetate, dimethyl sulfoxide, dimethylacetamide and ethanol as well as mixtures of these solvents, preferably using rotor-stator machines, high-energy mills, planetary kneaders, stirred ball mills, vibrating plates or ultrasonic devices.

[0168] The anode ink or paste has a pH value of preferably 2 to 8.5 (determined at 20°C, for example with the pH meter from WTW pH 340i with probe SenTix RJD).

[0169] The anode ink or paste can, for example, be applied by scraper to a copper foil or other current collector. Other coating methods, such as spin coating, roller coating, dip coating, slot coating, brushing, or spraying, can also be used according to the invention.

[0170] Before coating the copper foil with the anode material according to the invention, the copper foil can be treated with a commercially available primer, for example, based on polymer resins or silanes. Primers can improve adhesion to the copper, but generally possess practically no electrochemical activity themselves.

[0171] The anode material is generally dried until its weight is constant. The drying temperature depends on the components used and the solvent employed. It is preferably between 20 and 300°C. The layer thickness, i.e., the dry film thickness of the anode coating, is preferably 2 to 500 µm.

[0172] Finally, the electrode coatings can be calendered to achieve a defined porosity. The electrodes produced in this way preferably exhibit porosities of 15 to 85%, which can be determined by mercury porosimetry according to DIN ISO 15901-1. Preferably, 25 to 85% of the pore volume determined in this way is provided by pores with a pore diameter of 0.01 to 2 µm.

[0173] Furthermore, lithium-ion batteries are disclosed comprising a cathode, an anode containing the etched silicon-containing material, two electrically conductive terminals on the electrodes, a separator and an electrolyte with which the separator and the two electrodes are impregnated, as well as a housing to accommodate the said parts.

[0174] For the purposes of this invention, the term lithium-ion battery also includes cells. Cells generally comprise a cathode, an anode, a separator, and an electrolyte. In addition to one or more cells, lithium-ion batteries preferably also include a battery management system. Battery management systems generally serve to control batteries, for example, by means of electronic circuits, in particular for detecting the state of charge, for deep discharge protection, or for overcharge protection.

[0175] As preferred cathode materials, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide (doped or undoped), lithium manganese oxide (spinel), lithium nickel cobalt manganese oxides, lithium nickel manganese oxides, lithium iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium vanadium phosphate, or lithium vanadium oxides can be used according to the invention.

[0176] The separator is generally an electrically insulating, ion-permeable membrane, preferably made of polyolefins, for example polyethylene (PE) or polypropylene (PP), or polyester or corresponding laminates. As is common in battery manufacturing, the separator can alternatively be made of or coated with glass or ceramic materials. The separator, as is known, separates the first electrode from the second electrode and thus prevents electrically conductive connections between the electrodes (short circuit).

[0177] The electrolyte is preferably a solution containing one or more lithium salts (= conducting salt) in an aprotic solvent. Preferably, the conducting salts are selected from the group consisting of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium imides, lithium methides, lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonimide) (LiN(CF3SO2)2), and lithium borates. The concentration of the conducting salt, based on the solvent, is preferably between 0.5 mol / L and the solubility limit of the respective salt. Particularly preferably, it is between 0.8 and 1.2 mol / L.

[0178] Cyclic carbonates, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethoxyethane, diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, gamma-butyrolactone, dioxolane, acetonitrile, organic carbonic acid esters or nitriles, individually or as mixtures thereof, are preferably used as solvents.

[0179] Preferably, the electrolyte contains a film-forming agent, such as vinylene carbonate or fluoroethylene carbonate. This allows for a significant improvement in the cycle stability of the anodes containing the etched silicon-containing material obtained according to the inventive process. This is mainly attributed to the formation of a solid electrolyte intermediate phase on the surface of active particles. The proportion of the film-forming agent in the electrolyte is preferably between 0.1 and 20.0 wt.%.

[0180] To optimally match the actual capacitances of the electrodes in a lithium-ion cell, it is advantageous to balance the materials for the positive and negative electrodes with respect to their absolute capacitance. Of particular importance in this context is the fact that during the first or initial charge / discharge cycle of secondary lithium-ion cells (the so-called formation phase), a protective layer forms on the surface of the electrochemically active materials in the anode. This protective layer is called the "Solid Electrolyte Interphase" (SEI) and typically consists primarily of electrolyte decomposition products and a certain amount of lithium, which is then no longer available for further charge / discharge reactions. The thickness and composition of the SEI depend on the type and quality of the anode material and the electrolyte solution used.

[0181] The SEI is particularly thin in the case of graphite. On graphite, a loss of typically 5 to 35% of the mobile lithium occurs during the first charging step. Consequently, the reversible capacity of the battery also decreases.

[0182] In anodes with the etched silicon-containing active material obtained according to the inventive method, a loss of mobile lithium of preferably at most 30%, particularly preferably at most 20% and most preferably at most 10% occurs in the first charging step, which is significantly below the values ​​described in the prior art, such as in US 10,147,950 B1.

[0183] All substances and materials used for the manufacture of such lithium-ion batteries, as described above, are known. The production of the components of such batteries and their assembly into batteries is carried out according to methods known in the field of battery manufacturing.

[0184] The silicon-containing material obtained according to the inventive process is characterized by significantly improved electrochemical behavior and leads to lithium-ion batteries with high volumetric capacities and excellent application properties. The silicon-containing material obtained according to the inventive process is permeable to lithium ions and electrons, thus enabling charge transport. The SEI (silicon electrochemical reaction) in lithium-ion batteries can be significantly reduced with the silicon-containing material obtained according to the inventive process. In addition, due to the design of the silicon-containing material obtained according to the inventive process, the SEI no longer detaches from the surface of the active material, or at least to a much lesser extent.All of this leads to a high cycle stability of corresponding lithium-ion batteries, in whose anodes the silicon-containing material obtainable according to the inventive method is contained.

[0185] The following examples serve to further illustrate the invention described here.

[0186] The following analytical methods and instruments were used for characterization: Inorganic Analysis / Elemental Analysis: The carbon (C) contents given in the examples were determined using a Leco CS 230 analyzer. A Leco TCH-600 analyzer was used to determine the oxygen (O) and, where applicable, nitrogen (N) and hydrogen (H) contents. The qualitative and quantitative determination of other elements was carried out using inductively coupled plasma (ICP) emission spectrometry (Optima 7300 DV, Perkin Elmer). For this purpose, the samples were acidified in a microwave oven (Microwave 3000, Anton Paar) using HF / HNO₃. 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 the analysis of acidic aqueous solutions (e.g. acidified drinking water, wastewater and other water samples, aqua regia extracts from soils and sediments).Particle size determination: The particle size distribution was determined according to ISO 13320 within the scope of this invention using static laser scattering with a Horiba LA 950. Particular care must be taken during sample preparation to ensure the dispersion of the particles in the measuring solution, so that the size of agglomerates is measured instead of the size of individual particles. The particles were dispersed in ethanol for the measurement. If necessary, the dispersion was treated with ultrasound for 4 minutes in a Hielscher ultrasonic laboratory instrument, model UIS250v, with a sonotrode LS24d5 at 250 W prior to measurement. Surface area measurement according to BET: The specific surface area of ​​the materials was measured by gas adsorption with nitrogen using a Sorptomatic 199090 (Porotec) or SA-9603MP (Horiba) instrument according to the BET method (determination according to DIN ISO 9277:2003-05 with nitrogen). Skeletal density: The skeletal density, i.e.,The density of the porous solid, based exclusively on the volume of the externally gas-accessible pore spaces, was determined by helium pycnometry according to DIN 66137-2. Gas-accessible pore volume: The gas-accessible pore volume according to Gurwitsch was determined by gas sorption measurements with nitrogen according to DIN 66134. Conversion: The conversion is calculated as the quotient of the amount of substance (in moles) of the reactant, relative to the amount of substance (in moles) of the starting material (reactant). In these examples, it shows how many of the SiH₄ molecules used are converted to Si. Umsatz SiH 4 in % = Stoffmenge an gewonnenem Si Stoffmenge an eingesetztem SiH 4 ∗ 100 % Yield: The yield is the quotient of the mass of product actually obtained and the theoretically maximum possible mass of product. The yield is expressed as a mass ratio in percent: Ausbeute in % = Tats ä chliche Masse an Produkt Maximal m ö gliche Masse an Produkt ∗ 100 %

[0187] It is a measure of the losses of particles carried along by the gas flow. Examples

[0188] The SiH 4 used, of quality 4.0, was purchased from Linde GmbH.

[0189] In all examples, amorphous carbon was used as a porous starting material: Specific surface area = 1907 m² / g; Pore volume = 0.96 cm³ / g; Mean volume-weighted particle size D50 = 2.95 µm; Particle density = 0.7 g / cm³; Cohesive; Classification as money type class: C

[0190] The following reactors were used in carrying out the experimental examples: Reactor (according to the invention):

[0191] All examples according to the invention were carried out within the framework of the special variant of the method – reactors A, B and C are the same vessel. The reactor used consisted of a cylindrical lower part (cup) with an inner radius r B =121.5 mm in diameter, with a height h = 512 mm, a lid with multiple connections (e.g., for gas supply, gas exhaust, temperature and pressure measurement), and a flat bottom. There were no internal components on the wall. The reactor volume was VB = 24 l. The perimeter of any cross-sectional area of ​​the surface of revolution, obtained by rotating the inner reactor contour around the axis of rotation, is calculated to be 763.4 mm. The stirrer used was a multi-blade helical stirrer with a radius of r R = 119.5 mm. The complete rotation of the helical agitator results in a surface of revolution. The circumference of any cross-sectional area perpendicular to the axis of rotation of this surface of revolution is 750.8 mm. From these two circumferences, a wall penetration of W = 0.98. The height of the helix corresponded to approximately 75% of the clear height of the reactor interior. The reactor was filled to such an extent that the height of the stirred particle bed was less than the height of the helix. Thus, more than 50% of the reaction zone is located within the area of ​​the stirrer with wall penetration. W = 0.98. The beaker was electrically heated by a jacket heater. Temperature measurements were always taken between the heater and the reactor. Gas was supplied to the lower half (125 mm above the reactor bottom) of the packed bed via two immersion tubes with an outer diameter of d = 6 mm, which introduced the gas directly into the moving packed bed. Fluidized bed reactor (not according to the invention):

[0192] In comparative example 1, which is not according to the invention, a fluidized bed reactor was used, consisting of a cylindrical section with an outer diameter of 160 mm and a height of 1200 mm. The cylindrical section comprised a bottom chamber and the actual fluidized bed reactor. The two sections were separated by the gas-permeable bottom. Above the cylindrical reactor section was a reactor section with a cross-sectional area twice that of the cylindrical reactor section. At the top of the reactor was a lid with filter elements for gas discharge. The reaction temperature was set by heating the reactor wall, with the height of the heated area being 80% of the cylindrical length starting at the gas-permeable bottom. The temperature between the heating jacket and the reactor outer wall was used as a measure of the process temperature. Heating was electrically powered.The fluidizing gas was preheated with a gas heater before entering the fluidized bed reactor. Pulsation of the fluidizing gas flow was achieved using a directly controlled solenoid valve. The fluidization index was used as a measure of the fluidized bed quality.

[0193] In preliminary tests, the minimum fluidization velocity was determined by measuring the pressure loss of the fluidized bed.

[0194] Definition of fluidization index: The fluidization index FI is defined as the ratio of the measured pressure loss across the fluidized bed D p WS,measurement and the theoretically maximum achievable pressure loss Δ p WS,th and is calculated using the following equation 1: FI = Δ p WS , Messung Δ p WS , th

[0195] The theoretically maximum achievable pressure loss is calculated from the mass of the packed bed, neglecting the gas density. m S , the acceleration due to gravity g and the reactor cross-sectional area A WS to D p WS,th = m S · g / A WS .

[0196] In a fully fluidized fluidized bed, the fluidization index assumes values ​​of a maximum of 1.

[0197] Determination of the fluidization index:The fluidization index is the ratio of the measured pressure drop to the theoretically maximum possible pressure drop. To determine the fluidization index, it is necessary to measure the pressure drop of the fluidized bed. This measurement is performed as a differential pressure measurement between the lower and upper ends of the fluidized bed. The differential pressure gauge converts the pressures measured on diaphragms into digital values ​​and displays the pressure difference. The pressure measuring lines must be positioned directly above the gas-permeable base and directly above the fluidized bed. Accurate measurement of the weight of the introduced particle bed is also necessary for determining the fluidization index. See also [VDI Heat Atlas, 11th edition, Section L3.2 Flow modes and pressure drop in fluidized beds, pp. 1371–1382, Springer Verlag, Berlin Heidelberg, 2013].

[0198] Determination of the minimum fluidization velocity:The minimum fluidization velocity is the fluidizing gas velocity, relative to the empty reactor cross-sectional area, at which the particle bed transitions from a fixed bed to a fluidized bed. This minimum fluidization velocity can be determined by simultaneously measuring the controlled fluidizing gas flow rate using a mass flow meter and the pressure drop of the fluidized bed using a digital differential pressure gauge. Knowing the reactor's cross-sectional area, the fluidizing gas velocity can be calculated from the measured fluidizing gas flow rate. The recorded curve of the pressure drop versus the fluidizing gas velocity is called the fluidized bed characteristic curve. It is important to ensure that the fluidized bed characteristic curve is recorded starting from a high fluidizing gas velocity by gradually decreasing this velocity. With purely fixed bed flow, the pressure drop increases linearly.The associated fluidization index. FI is less than one. In a fully developed fluidized bed, the measured pressure loss is constant. The corresponding fluidization index FI is equal to one. The transition between the two regions is characterized by a state of minimum fluidization. The corresponding fluidizing gas velocity, referenced to the empty reactor cross-sectional area, is equal to the minimum fluidization velocity. If the transition from the fixed bed to the fluidized bed is characterized by a region, the intersection of the extrapolated fixed bed characteristic curve and the extrapolated fluidized bed characteristic curve is defined as the point of minimum fluidization. See also [VDI Heat Atlas 11th edition, section L3.2 Flow modes and pressure loss in fluidized beds, pp. 1371–1382, Springer Verlag, Berlin Heidelberg, 2013]. Rotary kiln reactor (not according to the invention):

[0199] In comparative example 2, which is not according to the invention, an indirectly heated rotary kiln was used. This rotary kiln had a rotating quartz glass tube with a diameter of 20 cm and a heatable volume of 30 L, which could be rotated about its longitudinal axis. The outer wall temperature of the quartz tube was used as a measure of the process temperature. Heating was electric and could be regulated by three zones. The rotary kiln had to be sealed gas-tight to carry out the silicon infiltration reactions. Comparative example 1 (fluidized bed not according to the invention):

[0200] Production of a silicon-containing material in a fluidized bed reactor with a pulsed fluidizing gas stream

[0201] 500 g of an amorphous carbon as a porous starting material (specific surface area = 1907 m² / g, pore volume = 0.96 cm³ / g, mean volume-weighted particle size D50 = 2.95 µm, particle density = 0.7 g / cm³, Geldart class C particles) were placed in the reactor.

[0202] The particle bed was fluidized with a nitrogen-based fluidizing gas, the gas flow rate being set to at least three times the minimum fluidization velocity determined in preliminary tests. Simultaneously, the gas flow was oscillated using a solenoid valve, with a frequency of 3 Hz between the open and closed positions. Subsequently, the reactor temperature was increased to the target temperature of 430 °C. Due to the temperature increase, the fluidizing gas flow rate was adjusted to achieve a fluidization index greater than 0.95.

[0203] After reaching the target temperature of 430°C, the fluidizing gas was replaced by a reactive gas containing 10 vol% SiH₄. The pulsation of the gas flow, with a frequency of 3 Hz between the open and closed positions of the valve, persisted during and after the change of fluidizing gases, and the values ​​for the fluidization index remained unchanged. FI The amount of fluidizing gas was adjusted to ensure that the fluidization index values ​​were always greater than 0.95, both due to the density change of the porous starting materials during the deposition of silicon (= 0.98).

[0204] After a reaction time of 2.6 hours, the fluidizing gas was switched back to a pulsed nitrogen stream. The heating power was reduced. Once a temperature of 50°C was reached, the fluidizing gas stream was switched to a fluidizing gas consisting of 5 vol% oxygen in nitrogen and held for 60 minutes to allow any reactive groups present on the surface of the resulting product to react in a controlled manner. The reactor was then cooled to room temperature.

[0205] After completion of the process, 990 g of a black solid were discharged from the reactor. The recovered silicon-containing material was transferred to a cylindrical vessel and homogenized in a rotary mixer. The agglomerates formed by the fluidized bed process were removed by sieving. The reaction conditions for the production and the material properties of the silicon-carbon composite particles are summarized in Table 2.

[0206] Comparative example 2 (rotary kiln not according to the invention): Production of a silicon-containing material according to a non-inventive method in a rotating tubular reactor

[0207] A rotating tubular reactor (bulk volume 30 L) was loaded with 0.9 kg of the same porous carbon as in comparison example 1 (specific surface area = 1907 m² / g, pore volume = 0.96 cm³ / g, mean volume-weighted particle size D₅₀ = 2.95 µm, particle density = 0.7 g / cm³, Geldart class C particles). After inerting with nitrogen, the reactor was heated to 430°C. Upon reaching the reaction temperature, the reactive gas (10% SiH₄ in N₂, dosage rate 0.4 g Si / (cm³*h)) was passed through the reactor for 8.5 h, during which time the reactor was rotated at approximately 7 revolutions per minute. The reactor was then purged with inert gas. Before being removed from the reactor, the product was cooled to room temperature under inert gas. The reaction conditions for its production and the material properties of the silicon-carbon composite particles are summarized in Table 2.

[0208] Examples 1-5 (according to the invention):Production of silicon-containing materials according to the inventive process using monosilane SiH 4 as a silicon precursor under normal pressure (0.1 MPa) (the respective values ​​for the parameters AD (The example numbers are summarized in Table 1)

[0209] In phase 1 of the process, 2.4 kg of the same porous carbon as in comparative examples 1 and 2 (specific surface area = 1907 m² / g, pore volume = 0.96 cm³ / g, mean volume-weighted particle size D50 = 2.95 µm, particle density = 0.7 g / cm³, Geldart class C particles) was placed into the reactor according to the invention with the agitator (volume 24 L, diameter 25 cm). The reactor was then heated to 350°C for 240 minutes and inerted with nitrogen.

[0210] In phase 2, the reactor was heated to 430°C. Upon reaching the reaction temperature, the reactive gas was... Concentration A mol% and pore volume-related Dosage rate B for C hours the gas phase was fed into the reactor, while the particle bed was circulated by a wall-penetrating agitator according to the invention, a helical agitator, such that the Ratio of turnover time to mean residence time of the reactive component D was and the state of motion of the fill could be described with Froude number 3.

[0211] In phase 3, the silicon-containing material was cooled to a temperature of 70°C within 120 minutes. The reactor was then purged for one hour with nitrogen, one hour with lean air containing 5% oxygen by volume, one hour with lean air containing 10% oxygen by volume, one hour with lean air containing 15% oxygen by volume, and finally one hour with air. The product was then removed from the reactor. Table 1 Experimental parameters for examples 1 to 5 according to the invention Test parameters Designation Example number Example 1 Example 2 Example 3 Example 4 Example 5 SiH 4 conc, mol% A 10 50 50 100 100 Dosage rate g Si / (cm 3< h) B 0,4 0,4 1,5 0,4 0,2 Reaction time Phase 2, h C 9,7 6,9 2,5 5,3 8,5 Ratio t (revolution time) / t (residence time) D 0,075 0,015 0,015 0,007 0,007

[0212] The reaction conditions for the production and the material properties of the silicon-carbon composite particles are summarized in the following Table 2. Table 2 Vbsp 1* Vbsp 2* Example 1 Example 2 Example 3 Example 4 Example 5 Reactor type Fluidized bed pulsates rotary kiln SBR SBR SBR SBR SBR Quantity of starting material, kg 0,5 0,9 2,4 2,4 2,4 2,4 2,4 SiH 4 conc, mol% 10 10 10 50 50 100 100 Jacket temperature Phase 2, °C 430 430 430 430 430 430 430 Reaction time Phase 2, h 2,6 9,9 9,7 6,9 2,5 5,3 8,5 Reactor volume, L 20 30 24 24 24 24 24 Reactor diameter, m 0,15 0,20 0,25 0,25 0,25 0,25 0,25 Fr number n / a 0,005 3 3 3 3 3 Ratio t (revolution time) / t (residence time) n / a n / a 0,075 0,015 0,015 0,007 0,007 Pore ​​volume-related dosing rate g Si / (cm 3< *h) 2,6 0,4 0,4 0,4 1,5 0,4 0,2 Area-related dosing rate kg Si / (m²< *h) 70,1 10,8 18,2 18,2 68,1 18,2 9,1 Sales SiH 4 ,% 20 40 41 60 40 75 98 Quantity of product, kg 0,99 1,84 5,67 5,74 5,51 5,66 5,80 Product yield, % 80 82 95 96 92 95 97 Particle discharge Yes Yes no no no no no Si, wt.% 56 56,5 56 57 55 56 57 0% wt 3,8 3,04 2,1 2,64 3,62 2,64 2,84 BET m 2< / g 11 10 23 26,6 43,6 26,8 23,8 *not according to the invention

[0213] Regardless of the reactors used, the same characteristic material properties can be obtained. However, SiH₄ conversion, product yield, and reaction time were improved in the reactor system according to the invention compared to fluidized bed and rotary kilns. Evaluation of silicon composite particles in electrochemical cells

[0214] Example 6: Anode containing, respectively, silicon-containing material obtained according to the inventive method from Examples 1 to 5 and silicon-containing material obtained according to the non-inventive methods from Comparative Examples 1 and 2, a silicon-containing material produced according to the inventive method, and electrochemical testing in a lithium-ion battery according to the inventive method.

[0215] 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 agitated using a shaker (290 rpm) for 2.5 h until the polyacrylic acid was completely dissolved. Lithium hydroxide monohydrate (Sigma-Aldrich) was added portionwise to the solution until the pH reached 7.0 (measured with a WTW pH 340i pH meter and a SenTix RJD probe). The solution was then mixed using a shaker for a further 4 h. 3.87 g of the neutralized polyacrylic acid solution and 0.96 g of graphite (Imerys, KS6L C) were placed in a 50 ml container and mixed in a planetary mixer (SpeedMixer, DAC 150 SP) at 2000 rpm. Subsequently, 3.35 g each of the silicon-containing material obtained according to the inventive method from Examples 1 to 5 and of the silicon-containing material obtained according to the non-inventive methods from Comparative Examples 1 and 2 were stirred in at 2000 rpm for 1 min.Subsequently, 1.21 g of an 8 percent conductive carbon black dispersion and 0.8 g of deionized water were added and incorporated at 2000 rpm on the planetary mixer.

[0216] The ink was then dispersed in a dissolver for 30 minutes at 3000 rpm under a constant temperature of 20°C. Degassing was then carried out in a planetary mixer at 2500 rpm for 5 minutes under vacuum.

[0217] The finished dispersion was then applied to a 0.03 mm thick copper foil (Schlenk Metallfolien, SE-Cu58) using a film drawing frame with a 0.1 mm gap height (Erichsen, model 360). The resulting anode coating was then dried for 60 minutes at 50°C and 1 bar atmospheric pressure. The mean basis weight of the dry anode coating was 3.0 mg / cm² and the coating density was 0.8 g / cm³.

[0218] The electrochemical investigations were carried out on a button cell (type CR2032, Hohsen Corp.) in a two-electrode configuration. The electrode coating was used as the 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 / cm² (sourced from SEI) was used as the working electrode or positive electrode (Dm = 15 mm). A glass fiber filter paper (Whatman, GD Type D) impregnated with 60 µl of electrolyte served as the 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 built in a glovebox (< 1 ppm H 2 O, O 2 ), the water content in the dry mass of all components used was below 20 ppm.

[0219] The electrochemical test was performed 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 subsequent cycles, and after reaching the voltage limit of 4.2 V, with a constant voltage until the current fell below 1.2 mA / g (corresponding to C / 100) or 15 mA / g (corresponding to C / 8). The cell was discharged using the constant current (cc) method 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 subsequent cycles until the voltage limit of 2.5 V was reached. The selected specific current was based on the weight of the coating on the positive electrode. The electrodes were chosen to achieve a cathode-to-anode capacitance ratio of 1:1.2.

[0220] The results of the electrochemical testing of the full cells of lithium-ion batteries containing silicon-containing materials from examples 1 to 5 and comparison examples 1 and 2 are listed in Table 3.

Claims

1. A process for producing silicon-containing materials by thermal decomposition of silicon precursors in the presence of porous particles, where silicon is deposited in pores and on the surface of the porous particles, where the thermal decomposition of the silicon precursors takes place in the reaction zone of a gas-traversed reactor and the particles are circulated in the reaction zone during the thermal decomposition by means of a stirrer which is close-clearance in the heated regions, where the stirring mechanism is close-clearance if in equation 1 W h = u R h u B h for half of all values of h the close clearance W(h) in the reaction zone is W(h) > 0.9, where uR(h) = the outer circumference of the stirring mechanism in the sectional face at the height coordinate h and uB(h) = the inner circumference of the reactor in the sectional face at the height coordinate h.

2. The process as claimed in claim 1, wherein the reaction zone of the reactor is rotationally symmetrical, where the stirring mechanism is close-clearance if in equation 1 W h = u R h u B h where W (h) = the close clearance of a stirring mechanism in a rotationally symmetrical reactor, defined as the quotient of the circumferences of two planar sectional faces perpendicular to the rotational axis of two rotational faces, where h represents the height coordinate, uR(h) = the circumference of the circular inner sectional face calculated according to equation 2 u R h = 2 πr R h at multiple arbitrary points h of the rotational face perpendicular to the rotational axis through a planar section, rR(h) = the distance from the rotational axis to the outer contour of the stirring mechanism, where the stirring mechanism includes all components attached thereto, uB(h) = the circumference of the circular outer rotational face calculated according to equation 3 u B h = 2 πr B h at each arbitrary point h of the rotational face perpendicular to the rotational axis through a planar section, said rotational face being formed by rotation of the inner contour of the reactor about the rotational axis, rB(h) = the distance of the inner contour of the reactor to the rotational axis, and for half of all values of h the close clearance W(h) in the reaction zone must be W(h) > 0.9.

3. The process as claimed in claim 1 or 2, wherein, over the course of the deposition of the silicon precursor, metered addition takes place at a rate of 0.1-2 g of Si per cm3 of pore volume of the porous particles used per hour.

4. The process as claimed in claim 1 or 2, wherein, over the course of the deposition, the silicon precursor is metered in at a rate of 1-700 kg of Si per m2 of the greatest flow cross-sectional area of the reactor in the reaction zone per hour.

5. The process as claimed in any of the preceding claims, wherein the thermal decomposition of the silicon precursors takes place at 0.08 to 5 MPa.

6. The process as claimed in any of the preceding claims, wherein the thermal decomposition of the silicon precursors is carried out at 280 to 900°C.

7. The process as claimed in any of the preceding claims, wherein the bed temperature in the reaction zone of the reactor equipped with the close-clearance stirrer is in the range from 100 to 1000°C.

8. The process as claimed in any of the preceding claims, wherein the process is carried out in a cascade reactor system comprising multiple reactors.

9. The process as claimed in claim 7, wherein the process comprises at least phases 1 to 3: Phase 1: Filling of a reactor A with porous particles and pretreatment of the particles with subsequent transfer of the pretreated particles to a reactor B or to a reservoir container, or the material remains in the reactor A, Phase 2: Passing of a flow of a gas consisting of an inert gas and / or at least one reactive component containing a silicon precursor and / or at least one silicon-free precursor through reactor B, conditioning of the reactor to a temperature at which the thermal decomposition of the reactive component takes place on the surface and in the pores of the porous particles. The particle bed in reactor B is circulated with a close-clearance stirrer such that the movement state of the particle bed can be described with Froude numbers in the range between 1 and 10. The gas phase is supplied to reactor B, while the particle bed in reactor B is circulated by a close-clearance stirring element such that the ratio of circulating time to mean residence time of the reactive component is less than 1. After the silicon has been introduced into and onto the pores of the porous particles, the silicon-containing materials are transferred to reactor C or to a reservoir container for interim storage, or the material remains in the reactor B. Phase 3: Aftertreatment of the silicon-containing particles for functionalization and / or coating of the surface of the silicon-containing particles. Cooling of the particles to a defined temperature and withdrawal of silicon-containing materials from reactor C.