METHOD FOR THE PRODUCTION OF SILICON-CONTAINING MATERIALS IN A CASCADE REACTOR SYSTEM

Description

[0001] The invention relates to 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 as well as on the surface of the porous particles.

[0002] 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. However, a disadvantage is the relatively low electrochemical capacity of such graphitic carbons, which theoretically is at most 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, enabling very high electrochemically achievable lithium contents of up to 3579 mAh per gram of silicon [M. Obrovac, VL Chevrier Chem. Rev. 2014, 114, 11444].

[0003] 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.

[0004] 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 battery's 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.

[0005] The decrease in capacity over several charge and discharge cycles is also known as fading or continuous capacity loss and is usually irreversible.

[0006] 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.

[0007] For example, US 10,147,950 B2 describes the deposition of silicon from monosilane SiH 4 in a porous carbon in a tube furnace or similar furnace types at elevated temperatures of 300 to 900°C, preferably with movement of the particles, by a CVD ("chemical vapor deposition") or PE-CVD ("plasma-enhanced chemical vapor deposition") process.

[0008] This process uses a mixture of 2 mol% monosilane with nitrogen as an inert gas. The low concentration of the silicon precursor in the gas mixture results in very long reaction times. Furthermore, US 10,147,950 B2 discloses a variety of possible combinations of different temperature ranges from 300 to 900°C and different pressure ranges from 0.01 to 100 bar for carrying out the deposition of silicon on and in porous starting materials.

[0009] An analogous procedure is described in US 10,424,786 B1, in which the silicon precursors are introduced as a mixture with inert gas at a total pressure of 1.013 bar. WO2012 / 097969 A1 describes the deposition of ultrafine silicon particles in the range of 1 to 20 nm by heating silanes as silicon precursors on porous carbon supports at 200 to 950°C, whereby the silane is diluted with an inert gas to prevent agglomeration of the deposited silicon particles or the formation of thick layers, with deposition taking place in a pressure range of 0.1 to 5 bar.

[0010] Motevalian et al., Ind. Eng. Chem. Res. 2017, 56, 14995, describe the deposition of silicon layers under elevated pressure, but not in the presence of a porous matrix. Again, the silicon precursor used, in this case monosilane SiH₄, is present only in a low concentration of at most 5 mol% in the total gas volume.

[0011] US 10,508,335 B1 relates to a process for producing particulate materials with high electrochemical capacities suitable for use as active anode materials in rechargeable metal-ion batteries. In one aspect, US 10,508,335 B1 provides a process for producing a particulate material comprising a variety of composite particles.The process comprises providing particulate porous carbon frameworks comprising micropores and / or mesopores, wherein the porous carbon frameworks have a D50 particle diameter of at least 50 µm; depositing an electroactive material selected from silicon and its alloys into the micropores and / or mesopores of the porous carbon frameworks using a chemical vapor infiltration process in a fluidized bed reactor to provide intermediate particles; and comminuting the intermediate particles to provide the composite particles.

[0012] GB 2 587 326 A relates to a process for producing Si-containing composite particles in a fluidized bed, comprising (i) providing porous conductive particles with mesopores and / or micropores, a D50 particle diameter between 1-30 µm, a PD50 pore diameter ≤ 10 nm and a total pore volume of micropores and mesopores in the range of 0.4-2.2 cm³ / g, (ii) combining the porous conductive particles with a particulate additive having a D50 particle diameter between 40-300 µm, a particle density between 1.3-6 g / cm³ and a BET surface area ≤ 200 m² / g, wherein the mass ratio of the porous conductive particles to the particulate additive is 95:5 to 70:30, and (iii) conducting a Fluidizing gas, which includes a Si precursor gas, through the combined particles at a gas velocity that causes fluidization of the combined particles, and at a temperature that is effective,to effect the deposition of silicon in the pores of the porous conductive particles (chemical vapor infiltration; CVI). The properties of the particulate additive are selected to facilitate subsequent separation of the particles while simultaneously enabling effective fluidization of the combined particles during the CVI process. The porous conductive particles preferably consist of carbon, but can also consist of porous metal oxides (e.g., titanium oxide). The composite particles are preferably used as anode material in a rechargeable metal-ion battery.

[0013] GB 2 584 615 A ​​relates to a particulate material consisting of a plurality of composite particles, the composite particles comprising: (a) a porous carbon framework enclosing micropores and mesopores with a total pore volume of 0.4 to 0.75 (P1) cm³ / g, wherein the micropore volume fraction is in the range of 0.55 to 0.85, based on the total volume of the micropores and mesopores; and (b) a plurality of nanoscale silicon domains located within the pores of the porous carbon framework. The weight ratio of Si to the porous carbon framework in the composite particles is in the range of [0.9 x P1 to 1.8 x P1] : 1, i.e., the relative amount of Si filling the pores depends on the total pore volume.The composite particles are electroactive and can be provided as part of a composition that also includes at least one binder, a conductive additive, and an additional particle-shaped electroactive material, and can be used to form a negative electrode in a metal-ion battery, particularly a lithium-ion battery. The composite particles can be obtained by chemical vapor infiltration (CVI) of a silicon-containing precursor into the pore structure of a porous carbon skeleton.

[0014] The processes described above have a number of serious disadvantages. The silicon precursor is usually used at low absolute and partial pressures, and thus at low concentrations, which necessitates long reaction times to achieve high silicon content in the silicon-containing material. Furthermore, these processes are disadvantageous because only a small portion of the supplied reactive gas reacts, meaning that the reactor exhaust gas must be recycled or disposed of in a complex process, which further increases costs, especially when using silicon precursors with demanding safety requirements.

[0015] 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, especially with regard to reaction times.

[0016] Surprisingly, the problem was essentially solved by a process in which silicon is deposited in pores and on the surface of porous particles in a cascade reactor system by decomposing silicon precursors at a pressure of at least 7 bar. This is particularly surprising because it is known from processes for the production of polycrystalline silicon that the deposition of silicon at higher pressures leads to increased undesirable dust formation (JO Odden et al., Solar Energy Mat. & Solar Cells 2005, 86, 165), which is counterproductive for the deposition of silicon on the inner surface of the pores and the outer surface of the porous particles, as well as for the product yield. This adverse effect is surprisingly overcome by the process according to the invention.

[0017] The production of silicon-containing materials, for example as active materials for lithium-ion battery anodes, starting from porous particles and silicon precursors under pressure according to the invention is of particular economic interest, since it enables surprisingly higher amounts of silicon precursors in the porous particles and thus shorter reaction times. A further economic advantage of the process lies in the higher silicon yield relative to the silicon precursor used. In addition, 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 lithium-ion battery anodes, while simultaneously exhibiting low volume change during cycling.In contrast to producing the materials in question in only one reactor (not according to the invention), carrying out the process in a cascade reactor has the advantage that the long cooling and heating phases of a single reactor are reduced. This offers a time and energy advantage compared to a single reactor and results in lower material stress on the reactors.

[0018] The invention relates to a process for producing silicon-containing materials by thermal decomposition of one or more silicon precursors in the presence of one or more porous particles, wherein silicon is deposited in pores and on the surface of the porous particles, in a cascade reactor system comprising several reactors.

[0019] In a preferred embodiment, the method comprises at least phases 1 to 7: Phase 1: Filling reactor A with porous particles and pretreating the particles, Phase 2: Transfer of the pretreated particles into a reactor B and application of a reactive component containing at least one silicon precursor to the reactor, Phase 3: Heating reactor B to a target temperature at which the decomposition of the silicon precursor in the reactor begins, Phase 4: Decomposition of the silicon precursor with deposition of silicon in pores and on the surface of the porous particles, forming the silicon-containing materials and increasing the pressure to at least 7 bar. Phase 5: Cooling of reactor B, Phase 6: Removal of gaseous reaction products formed during the separation process from reactor B and transfer of the silicon-containing materials to reactor C, Phase 7: Removal of silicon-containing materials from reactor C.

[0020] In a preferred embodiment, phase 1 is designed as follows: Phase 1

[0021] Phase 1.1: Filling reactor A with the porous particles, Phase 1.2: Pretreatment of the particles in reactor A, Phase 1.3: Transfer of the pretreated particles to reactor B or intermediate storage in a storage container D and subsequent transfer to reactor B, or the material remains in reactor A.

[0022] In a preferred embodiment, phase 2 is designed as follows: Phase 2

[0023] Phase 2.1: Heating or cooling the particles in reactor B, possibly Phase 2.2: Adjusting the pressure in reactor B possibly Phase 2.3: Exposure of reactor B with at least one silicon-free reactive component, Phase 2.4: Applying at least one reactive component containing at least one silicon precursor to reactor B.

[0024] In a preferred embodiment, phase 3 is designed as follows: Phase 3

[0025] Phase 3.1: Heating reactor B to a target temperature at which the decomposition of the reactive component in reactor B begins.

[0026] If at least one silicon-free reactive component is present in reactor B, phase 3.2 preferably follows: Phase 3.2: Decomposition of the reactive component that does not contain a Si precursor.

[0027] In a preferred embodiment, phase 4 is designed as follows: Phase 4

[0028] Phase 4.1: Decomposition of the silicon precursor with deposition of silicon in pores and on the surface of the porous particles, whereby the pressure increases to at least 7 bar. Phase 4.2: Setting a minimum temperature or temperature profile for a defined period, during which a pressure of at least 7 bar is generated.

[0029] In a preferred embodiment, phase 5 is designed as follows: Phase 5

[0030] Phase 5.1: Adjusting the pressure in reactor B to a defined pressure. Phase 5.2: Setting reactor B to a defined temperature or a defined temperature profile.

[0031] In a preferred embodiment, phase 6 is designed as follows: Phase 6

[0032] Phase 6.1: Removal of gaseous reaction products formed during the separation process from reactor B, Phase 6.2: The particles are transferred to reactor C or temporarily stored in a storage container E and then transferred to reactor C, or the material remains in reactor B. Phase 6.3: Setting reactor C to a defined temperature or temperature profile and a defined pressure

[0033] In a preferred embodiment, phase 7 is designed as follows: Phase 7

[0034] Phase 7.1: Post-treatment of the particles in reactor C to deactivate the particle surfaces Phase 7.2: Cooling the particles to a defined temperature and removing silicon-containing materials from reactor C, and preferably directly transferring them to a storage container E or directly filling them into a suitable container.

[0035] In phase 1.1, porous particles are filled into a heatable and / or vacuum-resistant and / or pressure-resistant reactor A; this filling can be done manually or automatically.

[0036] 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.

[0037] 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.

[0038] The aim of pretreating the particles in reactor A in phase 1.2 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.

[0039] The aim of pretreatment in phase 1.2 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 phase 1.3. 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, ammonium dihydrogen phosphate, lithium nitrate, sodium nitrate, potassium nitrate, lithium chloride, sodium chloride, potassium chloride, lithium bromide, sodium bromide, potassium bromide, and alkanolates.

[0040] The transfer in phase 1.3 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 conveyor), as well as by means of discontinuous conveyors: floor-mounted, rail-free (e.g., automated vehicle, hand pallet truck, electric pallet truck, automated guided vehicle (AGV), hover vehicle, handcart, electric cart, motorized vehicle (tractor, cart, forklift), transfer car, transfer pallet truck, stacker crane (with / without transfer unit, curve-capable); floor-mounted, rail-mounted (e.g., industrial railway, railcar); floor-free (e.g., trolley conveyor, cranes).Bridge crane, gantry crane, jib crane, tower crane), electric monorail (EMC), small container transport system; stationary (e.g. elevator, lifting platform and mobile elevating work platform, walking conveyor).

[0041] The storage container D can be temperature-controlled, movable, insulated, or connected to reactor B via a pipe system.

[0042] In phase 2.1, the pretreated material is preferably heated to a temperature of 100 to 1000 °C in reactor B, particularly preferably 250 to 500 °C and especially preferably 300 to 400 °C.

[0043] In optional phase 2.2, reactor B is preferably adjusted to a pressure of 0.01 mbar to 100 bar, particularly preferably 0.01 mbar to 10 bar, and especially preferably 50 mbar to 3 bar. Inert and / or reactive gases can be used to adjust the pressure. Examples of inert gases include hydrogen, helium, neon, argon, krypton, xenon, nitrogen, carbon dioxide, or steam, or mixtures thereof, such as forming gas. Argon, nitrogen, or especially hydrogen are preferred.

[0044] The substances can be added to reactor B simultaneously, for example via a T-piece or an upstream mixing valve, or one after the other; alternatively, reactor B can be evacuated beforehand.

[0045] Preferably, reactor B in phase 2.2 is first exposed to inert gas or evacuated, in particular before reactor B is exposed to reactive component in phase 2.3 and / or 2.4.

[0046] In the optional phase 2.3, reactor B is supplied with a reactive component that does not contain a silicon precursor.

[0047] In phase 2.4, reactor B is supplied with a reactive component containing at least one silicon precursor.

[0048] 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 or via a special stirrer. This variant is particularly preferred when dosing into reactor B at a pressure below 1 bar before the start of the addition.

[0049] Reactor B is preferably charged with such an amount of reactive component that, relative to the weighted amount of porous particles, a sufficient quantity of silicon is deposited to achieve the target capacity of the silicon-containing material to be produced. This can be done in one step or in several iterations of phases 2.1 to 6.1.

[0050] Generally, "injection" refers to the introduction of the reactive component into the reactors. During this process, the components of the reactive component can be in gaseous, liquid, or sublimable solid form, for example.

[0051] The reactive component is preferably gaseous, liquid, solid, for example sublimable, or a mixture of substances, optionally consisting of substances in different states of matter.

[0052] The reactive component from phase 2.4 contains at least one silicon precursor and optionally an inert gas component. 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). In a particularly preferred embodiment, the reactive component contains no inert gas component.

[0053] The silicon precursor contains at least one reactive component which can react to form silicon under the chosen conditions, for example, thermal treatment.The reactive component 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, methylchlorosilanes such as trichloromethylsilane MeSiCl₃, 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.

[0054] 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.

[0055] 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.

[0056] Furthermore, the reactive components from phases 2.3 and / or 2.4 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).

[0057] Other reactive components that may be included in the reactive component 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 or butene, 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 Fischer-Tropsch synthesis plant, or more generally, hydrocarbon-containing streams from wood, natural gas, petroleum and coal processing.

[0058] Phases 2.1, 2.2, 2.3, and 2.4 can be performed in numerical order, but they do not have to be. They can also be performed multiple times in succession in any order.

[0059] In phase 3.1, that is, generally after reactor B is treated with the reactive component according to phase 2.4, reactor B is heated until the target temperature is reached. At the target temperature, the decomposition of the silicon precursor begins, with the deposition of silicon in the pores and on the surface of the porous particles. The onset of silicon precursor decomposition with silicon deposition can be experimentally detected by a pressure increase in reactor B, which is not caused by a temperature increase in reactor B. During the decomposition of silicon precursors, gaseous molecules are generally formed alongside silicon under reaction conditions, causing an increase in pressure in reactor B. The volume of reactor B generally remains constant during the process.

[0060] Preferably, in phase 3.1, the pressure change dp during the heating of the closed reactor B with volume V depends essentially on the temperature change dT, which can be described, for example, by the thermodynamic equation of state according to equation 1: d p Phase 3 = ∂ p ∂ T V , n d T

[0061] After reaching the target temperature for the decomposition of the silicon precursor in phase 3.2, the temperature in reactor B can be increased, kept constant or slightly reduced in phase 4.1 relative to the target temperature of phase 3.1.

[0062] Temperature, pressure, or differential pressure measurements in reactor B across all phases can be determined using standard reactor measuring instruments and methods. After standard calibration, different measuring instruments will yield the same results.

[0063] The target temperature is preferably in the range of 250 to 1000°C, particularly preferably 300 to 800°C, and most preferably 300 to 550°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 420°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.

[0064] In the case of the use of hydrocarbons in phase 2.3 as additional reactive components that do not contain a silicon precursor, target temperatures are applied in phase 3.2 and / or in addition to silicon deposition during phases 4.1 and 4.2 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.

[0065] In the process according to the invention, the pressure in reactor B rises to at least 7 bar during phases 4.1 and 4.2.

[0066] In a preferred embodiment, the reaction progress during the process is monitored by means of pressure changes. This allows, for example, the degree of infiltration or the end of infiltration to be determined. Infiltration refers to the deposition of silicon in pores and on the surface of the porous particles in phases 4.1 and 4.2. The end of infiltration can be determined, for example, by the cessation of a further pressure increase.

[0067] The pressure change dp in reactor B with volume V during phases 4.1 and 4.2 generally results essentially from the temperature change dT and / or the change in the amount of substance dn i during the deposition of silicon, which is represented, for example, by equation 2: d p Phase 4 = ∂ p ∂ T V , n i d T + ∑ i , i ≠ j ∂ p ∂ n i V , T , n j d n i

[0068] The pressure change in phases 4.1 and 4.2 preferably results primarily from the change in the amount of substance during the deposition of silicon. Advantageously, the end of the reaction of the silicon precursors can thus be recognized by the absence of a further pressure increase at the end of phases 4.1 and 4.2, so that the subsequent phases can be triggered efficiently without unnecessarily removing unreacted silicon precursors from the reactor and complete conversion is achieved.

[0069] In one variant of the process, the temperature in phases 4.1 and 4.2 is not increased or maintained by external heating. The temperature in phases 4.1 and 4.2 is preferably determined by the heat generated during the potentially exothermic decomposition of the silicon precursors. A slight temperature drop in phases 4.1 and 4.2 is also preferred, particularly preferably a drop of no more than 20°C during phases 4.1 and 4.2.

[0070] Preferably, the pressure rise dp in reactor B in phases 4.1 and 4.2 (decomposition of the silicon precursor) is higher than in phase 3.1 (heating of the pressure-resistant reactor), which is represented, for example, by equation 3a or 3b: d p Phase 4 > d p Phase 3 or ∂ p ∂ T V , n i d T + ∑ i , i ≠ j ∂ p ∂ n i V , T , n j d n i Phase 4 > ∂ p ∂ T V , n d T Phase 3

[0071] Preferably, the pressure in reactor B in phases 4.1 and 4.2 reaches at least 10 bar, more preferably at least 50 bar, and more preferably at least 100 bar. Preferably, the pressure in reactor B in phases 4.1 and 4.2 remains below 400 bar, more preferably below 300 bar, and more preferably below 200 bar.

[0072] In reactor B, the temperature in phases 4.1 and 4.2 is preferably in the range of 100 to 1000°C, particularly preferably in the range of 300 to 900°C and most preferably in the range of 320 to 750°C.

[0073] Temperature, pressure, pressure changes, or differential pressure measurements in reactor B during phases 4.1 and 4.2 can be determined using measuring instruments and methods commonly used for pressure-resistant reactors. After standard calibration, different measuring instruments will yield the same results. Amounts of substances or changes in amounts of substances can be determined, for example, by taking a sample of a defined volume from the pressure-resistant reactor and determining its composition using conventional gas chromatography.

[0074] The heating of reactor B in phase 3.1 and optionally in phase 4.1 can be carried out, for example, with a constant heating rate or with several different heating rates. Heating rates can be adjusted by those skilled in the art in individual cases depending on the specific design of the process, for example, depending on the size of the reactor, the quantity of porous particles in the reactor, the stirring technology, and the planned reaction time. Preferably, the entire reactor B is heated so rapidly in phase 3.1 that, despite the rapid heating, the maximum temperature gradient in reactor B at the temperature at which the decomposition of the silicon precursor begins remains below 1000°C / m, particularly preferably below 100°C / m, and most preferably below 10°C / m. This ensures, for example, that the majority of the silicon is deposited in the pores of the porous particles and not on their outer surfaces.

[0075] 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.

[0076] Preferably, reactor B is heated in phase 3.1 at heating rates of 1 to 100°C per minute, particularly preferably at heating rates of 2 to 50°C per minute, and most preferably at a heating rate of 3 to 10°C per minute.

[0077] During the decomposition of the silicon precursors in phases 4.1 and 4.2, the temperature can be kept constant or varied. The aim is the almost complete conversion of the silicon precursors in the shortest possible time, producing a silicon-containing material suitable for application.

[0078] To control the rate of pressure rise in the various phases of the process, different technical solutions can be employed. To increase or decrease the pressure rise, the heat input to the reactor contents is preferably increased or decreased, respectively. To reduce the rate of pressure rise, heat removal from reactors B and C is preferably also increased by cooling; for this purpose, one or more reactor walls are preferably cooled, or heat removal devices, such as cooling pipes or cooling fins, are installed in the reactor. To control the pressure in the reactor very quickly, the addition or removal of small quantities of gas from reactor B or C, or the addition of evaporating liquids, is preferred.In this process, the partial flow removed from reactor B or C is preferably returned, either completely or partially, to the reactor contents in a closed circuit after cooling and / or separation of a portion of the total flow.

[0079] The reaction process in phases 4.1 and 4.2 is preferably monitored analytically to determine 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, pressure measurements to determine the reaction progress by observing changes in the ratios of solid to gaseous reactor components, and other methods that allow observation of the changing composition of the gaseous head during the reaction.

[0080] Preferably, the change in pressure, in particular the pressure slope, in reactor B is monitored during the execution of the process. The slope is an indicator of the deposition rate and thus a reference to the remaining surface area in the porous particles or in the silicon-containing material being formed.

[0081] 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, via 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 allows phase 2.4 to be continued continuously until the desired amount of silicon has been deposited. Likewise, phase 6.1 is continued continuously in parallel.

[0082] In a further preferred embodiment of the process, reactor B is equipped with a technical feature 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.

[0083] In phase 5.1, the pressure in reactor B is adjusted by releasing the existing pressure, evacuating and / or supplying it with another gas, preferably inert gases such as hydrogen, helium, neon, argon, krypton, xenon, nitrogen, carbon dioxide or water vapor individually or as mixtures, hydrogen is particularly preferred.

[0084] In phase 5.2, reactor B is set to a defined temperature or undergoes a defined temperature profile. Preferably, after completion of the deposition, cooling to a target temperature is optionally performed, preferably to the temperature required for a subsequent phase 2.3 and / or 2.4.

[0085] The order of 5.1 and 5.2 is arbitrary. Phases 5.1 and 5.2 can overlap in their execution.

[0086] In phase 6.1, the gaseous reaction byproducts formed during the deposition process are preferably removed from the gas phase of reactor B at the deposition temperature or after reaching the temperature required for their removal, for example, by purging. A purge gas is preferably used. Preferably, reactor B is evacuated at least once before being supplied with the purge gas. Preferred purge gases are inert gases such as hydrogen, helium, neon, argon, krypton, xenon, nitrogen, carbon dioxide, or water vapor, used individually or as mixtures or mixtures thereof with oxygen, such as air or lean air. The water content of the gas mixture can be adjusted. In phase 6.2, the particles obtained from reactor B are then transferred either to reactor C or to a suitable storage container.Once the particles have been transferred to a storage container, they can be transferred directly from there to reactor C. The transfer to phase 6.2 can be accomplished, 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, vibratory conveyor); Gravity conveyors (e.g., chutes, roller conveyors, ball tracks, rail tracks), as well as discontinuous conveyors, floor-mounted and rail-free (e.g., automated vehicles, hand pallet trucks, electric pallet trucks, automated guided vehicles (AGVs), hoist vehicles, handcarts, electric carts, motorized vehicles (tractors, trolleys, forklifts), transfer cars, transfer pallet trucks, stacker cranes (with / without transfer units, curve-capable); floor-mounted and rail-mounted (e.g., industrial railways, track-mounted vehicles); floor-free (e.g.,...)B Trolley railway, cranes (e.g. bridge crane, gantry crane, jib crane, tower crane), electric monorail (EHB), small container transport system; stationary (e.g. elevator, lifting platform and mobile elevating work platform, walking conveyor, are carried out.

[0087] In phase 7.1 of the process, the silicon-containing particles in reactor C can be post-treated and / or deactivated. 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 deactivation of the surface of the silicon-containing material. For instance, 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, as well as 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 200°C, particularly preferably no more than 100°C, and especially preferably 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.

[0088] 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.

[0089] Alternatively, the deactivation of the particles in phase 7.1 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.

[0090] 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 ).

[0091] Boron-containing precursors can include, for example, borane (BH 3 ), triisopropyl borate ([(CH 3 ) 2 CHO] 3 B), triphenylborane ((C 6 H 5 ) 3 B) and tris-(pentafluorophenyl)borane (C 6 F 5 ) 3 B.

[0092] In phase 7.1, for example, post-coating of the particles with solid electrolytes via CVI deposition of, for example, tert-butyllithium and trimethyl phosphate can also be introduced.

[0093] In phase 7.2 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).

[0094] In another preferred embodiment of the method, phases 2.1 to 5.2 are repeated once or several times.

[0095] In a preferred embodiment of the process, phases 2.1 to 5.2 are repeated multiple times, wherein the silicon precursor applied in phase 2.4 can be the same or different in each instance, and mixtures of several silicon precursors are also possible. Likewise, the reactive component applied in 2.3 can be the same or different in each instance, or consist of mixtures of different reactive components. After the multiple repetitions of the individual phases 2.1 to 5.2, the process is completed in reactor B with phase 6. The sequence and execution of phases 2.1 to 6.1 can be varied by those skilled in the art. Individual phases can be omitted.

[0096] In another preferred embodiment of the method, phase 6.1 follows directly after phase 4.2; that is, phase 5 can be omitted; that is, after phase 4.2, phase 6.1 can be continued without cooling the reactor B.

[0097] In a further preferred embodiment, phases 2.1 to 6.1, optionally omitting phase 5, (reaction cycle) are repeated once or several times, wherein silicon-free reactive components as defined in phase 2.3 may also be used in one or more repetitions, and the silicon-free reactive components in the respective repetitions may be the same or different. Silicon-free reactive components preferably do not contain a silicon precursor. Silicon-free reactive components preferably contain one or more hydrocarbons. In this preferred embodiment, the use of the silicon-free reactive component in a repetition of phases 2.1 to 6.1 can, for example, occur before or after the deposition of silicon or between two silicon depositions. Preferred silicon-free reactive components are hydrocarbons.Preferably, when using silicon-free reactive components, carbon is deposited in pores and on the surface of the porous particles or silicon-containing materials.

[0098] In a particularly preferred embodiment, in a first reaction cycle in phase 2.4, a reactive component containing at least one silicon precursor is applied, and in the second reaction cycle in phase 2.3, a reactive component containing at least one hydrocarbon, which is preferably silicon-free, is applied, optionally omitting phase 5. This allows, for example, the obtaining of a silicon-containing material that has no outwardly facing free silicon surface. The order of 2.3 and 2.4 is variable.

[0099] Optionally, in a third reaction cycle in phase 2.3, another hydrocarbon-containing, silicon-free reactive component is used, potentially omitting phase 5. 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, resulting in no outwardly facing free silicon surface.

[0100] 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.

[0101] 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).

[0102] 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.

[0103] A vacuum-tight reactor is generally a reactor that can be operated in such a way that the pressure inside the reactor is less than or equal to the ambient pressure of the reactor.

[0104] A pressure-resistant reactor is generally a reactor that can be operated in such a way that the pressure inside the reactor is greater than or equal to the ambient pressure of the reactor.

[0105] 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.

[0106] The minimum requirements for the reactors used are: Reactor A: temperature-controlled and vacuum-resistant; Reactor B: temperature-controlled and pressure-resistant; Reactor C: temperature-controlled

[0107] Optional technical features for the individual reactors for special variants of the invention: Reactor A: System for preheating, drying, and inerting the porous particles. A system for the targeted addition / dosing of the porous particles (see Phase 1.1 for technical description) 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 (see Phase 1.3 for technical description). Reactor B: Air cooling system. To increase the volume, an additional pressure-resistant vessel can be connected, allowing for higher quantities of reactive components in each reaction cycle. This vessel can be heated or unheated. Pressure equalization between the vessel and Reactor B can occur passively (diffusion) or actively (mechanically assisted).To simplify the process, a hydrogen separator (technical description, see Phase 3.1) can be connected. A container can be connected to remove condensable or resublimable byproducts occurring in the gaseous reaction products, allowing the removal of these byproducts through condensation or resublimation. A system can be connected to transfer the material to reactor C or a storage container (technical description, see Phase 1.3). Reactor C: System for removing condensable or resublimable byproducts. A container can be connected to allow the removal of these byproducts through condensation or resublimation.

[0108] A cascade reactor system, as defined in the application, is a connection of at least two reactors. The number of reactors is unlimited. 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.

[0109] For the purposes of this application, reactor types preferably selected are those comprising tubular reactors, retort furnaces, fluidized bed reactors, fixed bed reactors, and autoclaves. Fluidized bed reactors and autoclaves, and especially autoclaves, are particularly preferred.

[0110] 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. This allows, for example, homogeneous contact of all porous particles with reactive components or a homogeneous temperature distribution of the bed to be achieved. The movement of the particles can be achieved, for example, by agitators within the reactor, by moving the entire reactor, or by fluidizing the solids in the reactor with a gas flow.

[0111] Reactor types for stationary, non-mixing packed beds can be of any geometry. Cylindrical, conical, spherical, polyhedral reactor designs, or combinations thereof, are preferred.

[0112] To mix a packed bed in reactors A, B, and C, all reactor designs in which the packed bed can be moved are preferred. These include, for example, moving reactors, reactors with moving agitators, gas-fed reactors, or combinations thereof.

[0113] The motion of moving reactors is preferably rotational. Other motions are also suitable. Preferred designs for rotating reactors include, for example, drum or tubular reactors, conical reactors, double-conical reactors, reactors with offset cones, spherical reactors, polyhedral reactors, V-shaped reactors, double-V-shaped reactors, or geometric combinations thereof. In symmetrical designs, the axis of rotation is preferably located along the reactor's axis of symmetry. In asymmetrical designs, the axis of rotation preferably passes through the reactor's center of gravity. In a further preferred embodiment, the axis of rotation is selected to produce a wobbling motion. The mixing processes within the moving reactor are preferably enhanced by internal components. Typical internal components are baffles, blades, paddles, and plowshares.According to the invention, the orientation of the axis of rotation is freely selectable. Axes of rotation are preferably oriented vertically, horizontally, or at a free angle relative to the horizontal orientation. Another preferred design for mixing packed materials comprises stationary reactors A, B, and C with moving agitators. Preferred geometries for this are cylindrical reactors, conical reactors, spherical reactors, polyhedral reactors, or combinations thereof. The movement of the agitator is preferably a rotational movement. 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 are preferably incorporated into reactors A, B, and C, each of which may 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 in which two or more agitator shafts run in parallel are also preferred. Designs in which two or more agitator shafts are not operated in parallel are also preferred. Another preferred 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 a screw conveyor rotating along the edge of the reactor.For horizontally operated reactors A, B, or C, designs are preferred in which, for example, one or more agitators mix the bulk material via a rotational movement driven by a main agitator shaft. Designs in which two or more agitator shafts run in parallel are also possible. Designs in which two or more agitator shafts are not operated in parallel are also preferred. For vertically operated reactors A, B, or C, agitators 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, are preferred. In horizontally operated reactors A, B, or C, several agitators are preferably located on one shaft.Inventive designs for the agitators of horizontally operated reactors include plowshares, paddles, blade agitators, spiral agitators, or, more generally, agitators that convey the bulk material both axially and radially. In addition to moving agitators, rigid internals, such as baffles, are also preferred for stationary reactors A, B, or C with moving agitators. Designs in which both the reactor and an agitator rotate are particularly preferred.

[0114] Another method for mixing bulk materials is preferably applied to gas streams. Fluidized bed reactor designs are particularly preferred here. Reactors A, B, or C, in which mixing zones are deliberately created within the reactor using pneumatics, are also preferred.

[0115] 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 wetted parts.

[0116] 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.

[0117] The inventive process for producing silicon-containing materials offers several decisive advantages over the prior art. In particular, the possibility of completely converting the silicon precursor in a short reaction time is advantageous, for example, supported by the pressure increase occurring during phase 4 that is not solely due to temperature. Another advantage is the possibility of reducing the amount of inert gas or even eliminating it entirely, which also leads to higher space / time yields and thus enables faster and more homogeneous deposition of the desired layers on the substrates. Furthermore, the continuous recirculation or processing of the reactor exhaust gas, as is typically generated in the operation of an open reactor, can be avoided.Furthermore, the described process in a sealable reactor enables the simple execution of multiple depositions from the same or different reactive components with a precisely adjustable amount of deposition product relative to the reactant of each deposition step. The silicon-containing materials obtained from the process according to the invention are thus also characterized by the advantageous homogeneity of the deposited layers. Due to the advantages of the process according to the invention, silicon-containing materials with outstanding properties are quickly and economically accessible, particularly for use as active materials for anodes of lithium-ion batteries. It is also particularly advantageous that the often-described dust formation can be avoided.This can be achieved, for example, through the large surface area of ​​the porous particles, which is available for the deposition of silicon from the silicon precursor, as well as the intensive penetration of the porous particles by the silicon precursors. This also results in a high yield of deposited silicon. In contrast to a variant in which all reaction steps are carried out in the same reactor (see counterexample 2), the cascade reactor offers the following advantages: Energy savings are achieved by reducing cooling and heating processes with large temperature differences. Investment costs are reduced through the precise design of each reactor to meet the requirements of the respective process step. A high degree of modularity offers broad adaptability to varying volume requirements and process parameters. The ability to combine different reactors A, B, and C in various dimensions and quantities reduces the risk of total system failure and allows for predictable maintenance downtime. The modular design enables minor maintenance work to be carried out on one reactor while the other reactors remain operational.

[0118] 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.

[0119] The ceramic materials can be, for example, binary, ternary, quaternary, quinary, senary, or septernary compounds. Ceramic materials with the following component formulas are preferred: Non-stoichiometric boron nitrides BN z with z = 0.2 to 1, non-stoichiometric carbon nitrides CN z with z = 0.1 to 4 / 3, boron carbonitrides B x CN z with x = 0.1 to 20 and z = 0.1 to 20, where x*3 + 4 ≥ z*3, 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 aluminium borosilicocarbonitridooxide Al u B y 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. ,

[0120] 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 gravimetric capacity (mAh / cm³) of lithium-ion batteries.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] The porous particles are preferably in particle form. 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, and thus form 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.

[0130] 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.

[0131] 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 to the measured circumference U of this projection: S = 2 πA / U .In the case of an ideally circular particle, S would have 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 sphericity S is measured, for example, by imaging 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.

[0132] 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.

[0133] 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).

[0134] 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).

[0135] 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 the capacity of lithium-ion batteries to be increased. The gas-inaccessible pore volume can be determined using the following formula:

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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).

[0144] The silicon-containing material can have any morphology, for example splintery, platy, spherical or needle-shaped, with splintery or spherical particles being preferred.

[0145] 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.

[0146] 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 would have the value 1. For the silicon-containing materials accessible according to the inventive method, 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 percentilesS 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.

[0147] 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.

[0148] 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.

[0149] 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).

[0150] 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.

[0151] The volume of silicon contained in the silicon-containing material, obtained via deposition from the silicon precursor, 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).

[0152] 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.

[0153] The gas-inaccessible pore volume of the silicon-containing material can be determined using the formula:

[0154] 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 by its respective weight-related percentage of the total material. For example, this results in the following for a silicon-containing material where silicon is deposited on a porous particle:

[0155] 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.

[0156] 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.

[0157] The porosity of the silicon-containing material can be either gas-accessible or gas-inaccessible. The ratio of the volume of gas-accessible to gas-inaccessible porosity of the silicon-containing material can generally range from 0 (no gas-accessible pores) to 1 (all pores are gas-accessible). Preferably, the ratio of the volume of gas-accessible to gas-inaccessible porosity of 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.

[0158] 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 preferred 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.

[0159] 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)).

[0160] 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. 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.

[0161] 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.

[0162] 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.

[0163] 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) as seen in SEM scans.

[0164] 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 located both within the pores and on the surface of the silicon-containing material. The sequence and number of layers in the silicon-containing material, as determined by corresponding repetitions of phases 2.1 to 6.1, are also arbitrary. For example, 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.

[0165] 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.

[0166] The use of the silicon-containing material as an active material in anode materials for anodes of lithium-ion batteries is also described, as is the use of such anodes for the production of lithium-ion batteries.

[0167] It is described that the anode material is preferably based on a mixture comprising the 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.

[0168] It is described that by using additional electrically conductive components in the anode material, the contact resistances within the electrode and between the electrode and the current collector can be reduced, which improves the current-carrying capacity of the lithium-ion battery according to the invention. Preferred additional electrically conductive components are, for example, conductive carbon black, carbon nanotubes, or metallic particles such as copper.

[0169] It is described that the primary conductive carbon black particles preferably have a volume-weighted particle size distribution between the diameter percentiles d10 = 5 nm and d90 = 200 nm. The primary conductive carbon black particles can also be chain-branched and form structures down to the micrometer scale. Carbon nanotubes preferably have diameters of 0.4 to 200 nm, particularly preferably 2 to 100 nm, and most preferably 5 to 30 nm. The metallic particles have a volume-weighted particle size distribution that preferably lies between the diameter percentiles d10 = 5 nm and d90 = 800 nm.

[0170] It is described that 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.

[0171] It is described that the silicon-containing material in the anodes for lithium-ion batteries can preferably comprise 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.

[0172] It is described that preferred binders are polyacrylic acid or its alkali salts, in particular lithium or sodium salts, polyvinyl alcohols, cellulose or cellulose derivatives, polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, polyimides, in particular polyamide-imides, or thermoplastic elastomers, in particular ethylene-propylene-diene terpolymers. Polyacrylic acid, polymethacrylic acid, or cellulose derivatives, in particular carboxymethylcellulose, are particularly preferred. The alkali salts, in particular lithium or sodium salts, of the aforementioned binders are also particularly preferred. The alkali salts, in particular lithium or sodium salts, of polyacrylic acid or polymethacrylic acid are most preferred. All or preferably a proportion of the acid groups of a binder can be present in the form of salts. The binders have a molar mass of preferably 100,000 to 1,000,000 g / mol.Mixtures of two or more binders can also be used.

[0173] It is described that either 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.

[0174] Examples of additives include pore-forming agents, dispersing agents, leveling agents or dopants, for example elemental lithium.

[0175] It is described that preferred formulations for the anode material preferably contain 5 to 95 wt.%, in particular 60 to 90 wt.% of the silicon-containing material, 0 to 90 wt.%, in particular 0 to 40 wt.% of other electrically conductive components, 0 to 90 wt.%, in particular 5 to 40 wt.% graphite, 0 to 25 wt.%, in particular 5 to 20 wt.% binder and 0 to 80 wt.%, in particular 0.1 to 5 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.%.

[0176] It is described that the processing of the components of the anode material to form 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.

[0177] The anode ink or paste has a pH value of preferably 2 to 7.5 (determined at 20°C, for example with the pH meter from WTW pH 340i with probe SenTix RJD).

[0178] It is described that the anode ink or paste can be applied, for example, by scraping onto a copper foil or other current collector. Other coating methods, such as spin coating, roller, dip or slot nozzle coating, brushing or spraying, can also be used.

[0179] It is described that, prior to 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.

[0180] It is described that 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, and particularly preferably between 50 and 150°C. The layer thickness, i.e., the dry film thickness of the anode coating, is preferably 2 to 500 µm, and particularly preferably 10 to 300 µm.

[0181] It is described that the electrode coatings can be calendered to achieve a defined porosity. The electrodes produced in this way preferably have porosities of 15 to 85%, which can be determined by mercury porosimetry according to DIN ISO 15901-1. 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.

[0182] Furthermore, a lithium-ion battery comprising a cathode, an anode, 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 accommodating the aforementioned parts, in which the anode contains silicon-containing material accessible according to the inventive method, is described.

[0183] 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 contain a battery management system. Battery management systems generally serve to control batteries, for example, by means of electronic circuits, in particular to detect the state of charge, for deep discharge protection, or overcharge protection.

[0184] It is described that lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide (doped or undoped), lithium manganese oxide (spinel), lithium nickel cobalt manganese oxides, lithium nickel manganese oxides, lithium iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium vanadium phosphate, or lithium vanadium oxides can be used as preferred cathode materials according to the invention.

[0185] It is described that 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 is known to separate the first electrode from the second electrode and thus prevent electrically conductive connections between the electrodes (short circuit).

[0186] It is described that the electrolyte is preferably a solution containing one or more lithium salts (= conducting salt) in an aprotic solvent. Preferably, 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.

[0187] It is described that 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.

[0188] It is described that the electrolyte preferably 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 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.%, particularly preferably between 0.2 and 15.0 wt.%, and most preferably between 0.5 and 10 wt.%.

[0189] To optimally match the actual capacitances of the electrodes in a lithium-ion cell, it is described that it is advantageous to balance the quantities of materials used for the positive and negative electrodes. 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), 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.

[0190] It is described that the SEI (State Electrical Index) 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.

[0191] It is described that in anodes with the 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.

[0192] It is described that a lithium-ion battery, the anode of which contains a silicon-containing material obtainable according to the inventive method, can be manufactured in all usual forms, for example in wound, folded or stacked form.

[0193] 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.

[0194] It is described that 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.

[0195] The following examples serve to further illustrate the invention described here.

[0196] The following analytical methods and instruments were used for characterization: Inorganic analysis / Elemental analysis:

[0197] 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 performed 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:

[0198] Within the scope of this invention, the particle size distribution was determined according to ISO 13320 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 for 4 minutes in a Hielscher ultrasonic laboratory instrument, model UIS250v, with a sonotrode LS24d5 at 250 W ultrasound prior to the measurement. Surface measurement according to BET:

[0199] The specific surface area of ​​the materials was measured by gas adsorption with nitrogen using a Sorptomatic 199090 (Porotec) or SA-9603MP (Horiba) device according to the BET method (determination according to DIN ISO 9277:2003-05 with nitrogen). Skeletal density:

[0200] The skeletal density, i.e. the density of the porous solid based on the volume excluding the externally accessible gas-filled pore spaces, was determined using He pycnometry according to DIN 66137-2. Gas-accessible pore volume:

[0201] The gas-accessible pore volume according to Gurwitsch was determined by gas sorption measurements with nitrogen according to DIN 66134.

[0202] The following materials and equipment were used in the experimental procedures: Reactors A, B, and C consisted of a cylindrical base (beaker) and a lid with several connections (e.g., for gas supply, gas discharge, temperature and pressure measurement). Each of the three reactors had a volume of 12 liters. The reactors were electrically heated. Temperature measurements were taken between the heater and the reactor. The stirrers used were nearly wall-penetrating helical stirrers. These had a height that corresponded to approximately 50% of the internal height of the reactor.

[0203] In the non-inventive counterexample 2, an identical reactor was used with the special feature that reactor A, B and C were the same vessel and no transfer of the material took place between the steps.

[0204] The SiH 4 used, of quality 4.0, was purchased from Linde GmbH.

[0205] The porous particles used in the example had the following properties: Density: 2.19 g / cm³ (He pycnometry) Surface area BET: 2255 m² / g Gurvich Volume: 1.16 cm³ / g Carbon content: 93.39 wt% (EA) Oxygen content: 5.45 wt% (EA) Hydrogen content: 0.70 wt% (EA) Micropore volume: 0.46 cm³ / g Particle size distribution: d 50 4.4 µm Example 1

[0206] Production of silicon-containing materials using monosilane SiH 4 as a silicon precursor in a cascade reactor system.

[0207] In phase 1.1, reactor A was filled with 842 g of porous material, the porous particles, and sealed. Subsequently, in phase 1.2, reactor A was heated to 350 °C and evacuated for 240 minutes to a final pressure of 1 x 10⁻³ bar. The material was then transferred in phase 1.3, under a nitrogen atmosphere, to reactor B, which had been heated to 350 °C.

[0208] In phase 2.1, the porous material in reactor B was heated to 350 °C. In phase 2.2, reactor B was first evacuated to 1 x 10⁻³ bar. Subsequently, in phase 2.4, 158 g of SiH₄ were pressurized to 15.0 bar. In phases 3.1 and 4.1, reactor B was heated to a temperature of 430 °C within 15 minutes, and this temperature was maintained for 70 minutes in phase 4.2. During phase 4.2, the pressure increased to 35.8 bar according to equation 2. The pressure in reactor B was then reduced to 1.5 bar in phase 5.1, and the reactor temperature was reduced to 350 °C in phase 5.2. Phases 2.4, 3.1, 4.1, 4.2, 5.1, and 5.2 were then repeated ten times in the specified sequence. In this process, the following steps were taken in the different phases, in the order given: 2.4 xg SiH₄ were dosed (x = 139, 133, 131, 128, 122, 119, 116, 114, 110, 77), resulting in an initial pressure of y bar (y = 15.0; 15.0; 15.0; 15.0; 15.0; 15.0; 15.0; 15.0; 14.9; 11.0). In all ten cases, reactor B was heated to a temperature of 430°C within 15 minutes in phases 3.1 and 4.1, and the temperature was maintained for 60 minutes in the iterations of phase 4.2. The pressure increased to z bar during phase 4.2 according to equation 2 (z = 35.6; 35.0; 34.2; 33.4; 33.1; 32.6; 32.0; 31.5; 31.8; 23.4). Following phase 4.2 of the first nine repetitions, the pressure was reduced to 1.5 bar in phase 5.1, and reactor B cooled to a temperature of 350 °C within 30 minutes in phase 5.2. After the tenth and final repetition of phase 4.2, and omitting phase 5 in phase 6.1, the pressure in reactor B was reduced to 1.0 bar. Subsequently, the hot material was transferred to reactor C via a pipe connection in phase 6.2. In phase 6.In step 3, a pressure of 4.5 bar was generated in reactor C using nitrogen, and the silicon-containing material cooled to a temperature of 70 °C within 90 minutes. Subsequently, in phase 7.1, reactor C was purged five times with nitrogen, ten times with lean air containing 5% oxygen, ten times with lean air containing 10% oxygen, ten times with lean air containing 15% oxygen, and then ten times with air. In phase 7.2, 1992 g of a silicon-containing material in the form of a fine, black solid were isolated. The silicon-containing material had the following properties. Surface area BET: 43 m² / g Carbon content: 40.2 wt.% (EA) Oxygen content: 2.77 wt.% (EA) Silicon content: 57.0 wt.% (EA)

[0209] The entire process took 36 hours. All three reactors were operating simultaneously; the time-determining step for the cascade reactor was the process in reactor B, which in this case lasted 18 hours. Counterexample 2 (not according to the invention)

[0210] Production of silicon-containing materials using monosilane SiH 4 as a silicon precursor in the reactor (reactor A, B and C from example 1 are the same pressure vessel for the counterexample).

[0211] In phase 1.1, the reactor was filled with 842 g of porous material and sealed. Subsequently, in phase 1.2, the reactor was heated to 350 °C and evacuated to a final pressure of 1 x 10⁻³ bar for 240 minutes. Then, in phase 2.4, 318 g of SiH₄ was introduced at a pressure of 15.0 bar. In phases 3.1 and 4.1, the reactor was heated to a temperature of 430 °C within 15 minutes, and this temperature was maintained for 70 minutes in phase 4.2. During phase 4.2, the pressure increased to 35.8 bar according to equation 2. Finally, in phase 5.1, the pressure in the reactor was reduced to 1.5 bar, and in phase 5.2, the reactor temperature was reduced to 350 °C. Subsequently, phases 2.4, 3.1, 4.1, 4.2, 5.1, and 5.2 were repeated ten times in the specified order. During these iterations, the following steps were performed in the specified order within the different phases:4 xg SiH₄ were dosed (x = 137, 130, 131, 130, 123, 120, 118, 116, 111, 75), resulting in an initial pressure of y bar (y = 15.0; 15.0; 15.0; 15.0; 15.0; 15.0; 14.9; 15.0; 15.0; 11.0). In all ten cases, the reactor was heated to a temperature of 430°C within 15 minutes in phases 3.1 and 4.1, and the temperature was maintained for 60 minutes in phase 4.2. The pressure increased to z bar during phase 4.2 according to equation 2 (z = 35.7; 35.2; 34.0; 33.3; 33.1; 32.8; 32.0; 31.3; 31.5; 23.74). Following phase 4.2 of the first nine repetitions, the pressure was reduced to 1.5 bar in phase 5.1, and the reactor cooled to a temperature of 350 °C within 30 minutes in phase 5.2. After the tenth and final repetition of phase 4.2, and omitting phase 5 in phase 6.1, the pressure in the reactor was reduced to 1.0 bar. In phase 6.In step 3, a pressure of 4.5 bar was generated in the reactor using nitrogen, and the silicon-containing material cooled to a temperature of 70 °C within 14 hours. Subsequently, in phase 7.1, the reactor was purged five times with nitrogen, ten times with lean air containing 5% oxygen, ten times with lean air containing 10% oxygen, ten times with lean air containing 15% oxygen, and then ten times with air. In phase 7.2, 1986 g of a silicon-containing material in the form of a fine, black solid were isolated. The silicon-containing material had the following properties. Surface area BET: 39 m² / g Carbon content: 39.6 wt.% (EA) Oxygen content: 2.87 wt.% (EA) Silicon content: 57.0 wt.% (EA)

[0212] The entire process lasted 47 hours. Example 3:

[0213] Electrochemical characterization of silicon-containing materials used as active materials in lithium-ion battery anodes: 29.71 g of polyacrylic acid (dried at 85°C to constant weight; Sigma-Aldrich, Mw ~450,000 g / mol) and 756.6 g of deionized water were shaken at 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 at a constant speed 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, 3.40 g each of the silicon-containing materials from Examples 1 and 2 were stirred in at 2000 rpm for 1 min.Subsequently, 1.21 g of an 8% conductive carbon black dispersion and 0.8 g of deionized water were added and incorporated at 2000 rpm in a planetary mixer. The mixture was then dispersed in a dissolver for 30 min at 3000 rpm under a constant temperature of 20°C. The ink was degassed again in the planetary mixer at 2500 rpm for 5 min under vacuum. 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 min at 50°C and 1 bar atmospheric pressure. The mean basis weight of the dry anode coating was 2.1 mg / cm² and the coating density was 0.9 g / cm³.

[0214] 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), while 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 (obtained 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.

[0215] The electrochemical testing was performed at 20°C. The cell was charged using a constant current / constant voltage (cc / cv) 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. After reaching the voltage limit of 4.2 V, charging continued at 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 a 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 ratio of the cell's charging to discharging capacity is called Coulomb efficiency.The electrodes were chosen so that a capacitance ratio of cathode to anode of 1:1.2 was achieved.

[0216] The results of the electrochemical testing of the full cell of lithium-ion batteries containing the active materials from Examples 1 and 2 are listed in Table 1.

[0217] In comparative example 2, 1986 g of material were produced in a reactor with a volume of 12 liters using a method not according to the invention within 48 hours, while in example 1, 1992 g of material were produced in three reactors with a volume of 12 liters each within 18 hours using the method according to the invention. Thus, in example 1, a material yield 2.5 times higher in terms of time was achieved than in example 2.

Claims

1. Process for producing silicon-containing materials by thermal decomposition of one or more silicon precursors in the presence of one or more porous particles, where silicon is deposited in pores and on the surface of the porous particles, in a cascade reactor system comprising a plurality of reactors.

2. Process according to Claim 1, which comprises at least the Phases 1 to 7: Phase 1:filling a reactor A with porous particles and pretreating the particles,Phase 2:transferring the pretreated particles into a reactor B and charging the reactor with a reactive component comprising at least one silicon precursor,Phase 3:heating the reactor B to a target temperature, at which the silicon precursor begins to decompose in the reactor,Phase 4:decomposing the silicon precursor, with deposition of silicon in pores and on the surface of the porous particles, with formation of the silicon-containing materials and with the pressure increasing to at least 7 bar,Phase 5:cooling the reactor B,Phase 6:removing gaseous reaction products, formed in the course of the deposition, from the reactor B and transferring the silicon-containing materials into a reactor C,Phase 7:withdrawing the silicon-containing materials from the reactor C.

3. Process according to Claim 2, wherein Phase 1 is configured as follows: Phase 1 Phase 1.1 :filling the reactor A with the porous particles,Phase 1.2 :pretreating the particles in reactor A,Phase 1.3 :transferring the pretreated particles into the reactor B, or interim storage into a reservoir vessel D and subsequent transfer into the reactor B, or the material remains in reactor A.

4. Process according to Claim 2 or 3, wherein Phase 2 is configured as follows: Phase 2 Phase 2.1:heating or cooling of the particles in reactor B,Phase 2.4:charging the reactor B with at least one reactive component comprising at least one silicon precursor.

5. Process according to Claim 2 to 4, wherein Phase 3 is configured as follows: Phase 3 Phase 3.1:heating the reactor B to a target temperature, at which the reactive component begins to decompose in reactor B.

6. Process according to Claim 2 to 5, wherein Phase 4 is configured as follows: Phase 4.1:decomposing the silicon precursor, with deposition of silicon in pores and on the surface of the porous particles, with the pressure increasing to at least 7 barPhase 4.2:establishing a minimum temperature or a temperature profile for a defined period in which a pressure of at least 7 bar comes about.

7. Process according to Claim 2 to 6, wherein Phase 5 is configured as follows: Phase 5 Phase 5.1:adjusting the pressure in reactor B to a defined pressure.Phase 5.2:cooling the reactor B to a defined temperature or a defined temperature profile.

8. Process according to Claim 2 to 7, wherein Phase 6 is configured as follows: Phase 6 Phase 6.1 :removing gaseous reaction products, formed in the course of the deposition, from the reactor B,Phase 6.2 :transferring the particles into reactor C, or interim storage into a reservoir vessel E and subsequent transfer into reactor C, or the material remains in reactor B,Phase 6.3 :adjusting reactor C to a defined temperature or a defined temperature profile and a defined pressure.

9. Process according to Claim 2 to 8, wherein Phase 7 is configured as follows: Phase 7 Phase 7.1:aftertreating the particles in reactor C to deactivate the particle surfaces,Phase 7.2:cooling the particles to a defined temperature and withdrawing silicon-containing materials from reactor C, and preferably direct transfer into a reservoir vessel E or direct filling into a suitable container.

10. Process according to Claim 2 to 9, wherein the cascade reactor consists of only two mutually dependent reactors, where Phases 1 to 6.1 are carried out in the same reactor and Phase 1.3 is omitted, or Phases 2 to 7 are carried out in a reactor and Phase 6.2 is omitted.

11. Process according to Claim 2 or 6 to 10, wherein the pressure in reactor B in Phase 4.1 and 4.2 reaches at least 10 bar.

12. Process according to Claim 2 or 6 to 11, wherein the temperature in reactor B in Phase 4.1 and 4.2 is in the range from 100 to 1000°C.

13. Process according to any of the preceding claims, wherein the silicon precursor comprises at least one reactive component which is selected from silicon-hydrogen compounds, chlorine-containing silanes, and also higher linear, branched or cyclic homologs of chlorine-containing silanes, chlorinated and part-chlorinated oligo- and polysilanes, methylchlorosilanes or mixtures thereof.

14. Process according to any of the preceding claims, wherein the porous particles are selected from amorphous carbons, silicon dioxide, boron nitride, silicon carbide and silicon nitride or else hybrid materials based on these materials.