Method for producing silicon-containing materials

Abstract

The present invention relates to a method for producing silicon-containing materials in a fluidized bed reactor by depositing silicon from at least one silicon precursor into the pores and on the surface of porous particles, characterized in that a pulsed fluidizing gas flow moves in a wave-like manner through the fluidized bed reactor and acts on the fluidized bed to produce a homogeneous fluidized bed characterized by a minimum fluidization index FI of 0.95. The present invention also relates to the use of the silicon-containing materials obtained according to the disclosed method as active material for the anode of a lithium ion battery, and to corresponding lithium ion batteries comprising in their anodes the silicon-containing materials obtained according to the disclosed method.

Description

[Technical Field]

[0001] The present invention relates to a method for producing silicon-containing materials in a fluidized bed reactor by depositing silicon in the pores and on the surface of porous particles, and to the use of the silicon-containing materials thus obtained as active materials for the anodes of lithium-ion batteries. [Background technology]

[0002] As a storage medium for electrical power, lithium-ion batteries are currently the most energy-dense electrochemical energy storage medium available. Lithium-ion batteries are particularly used in the field of portable electronics, tools, and electric modes of transportation such as motorcycles, mopeds, and automobiles. The currently widespread active material for the negative electrode ("anode") of such batteries is graphite-based carbon. However, a drawback is the relatively low electrochemical capacity of such graphite-based carbon, which theoretically provides only a maximum of 372 mAh per gram of graphite, thus corresponding to only about one-tenth of the electrochemical capacity theoretically achievable with lithium metal. Alternative active materials for the anode use silicon additives, as described, for example, in EP 1730800 B1, US 10,559,812 B2, US 10,819,400 B2, or EP 3335262 B1. Silicon forms a binary electrochemically reactive alloy with lithium, which allows 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 intercalation and deintercalation of lithium ions into silicon is associated with the drawback of very large volume changes, which can reach up to 300% in the case of complete intercalation. This volume change subjects the silicon-containing active material to significant mechanical stresses that can ultimately lead to its destruction. This process, also known as discharge grinding, leads to the loss of electrical contact between the active material and the electrode structure, and thus to a sustained and irreversible loss of electrode capacity.

[0004] Furthermore, the surface of the silicon-containing active material reacts with the electrolyte components, continuously forming a passivating protective layer (solid electrolyte interface, SEI). The formed component phase is no longer electrochemically active. The lithium bound therein is no longer available to the system, resulting in a significant and continuous loss of battery capacity. Due to the extreme volume change of silicon during the battery's charge / discharge procedures, the SEI regularly breaks down, thereby exposing further uncovered surfaces of the silicon-containing active material, which then form further SEI. Since the amount of mobile lithium ions corresponding to the usable capacity is limited by the cathode material in a full cell, they are increasingly consumed, and the cell capacity decreases to a level that is unacceptable for the intended application even after several cycles.

[0005] The decline in capacity over multiple charge-discharge cycles, also known as fading or the continuous loss of capacity, is generally irreversible.

[0006] The active material described for the anode of a lithium-ion battery is a mass of silicon-carbon composite particles in which silicon is intercalated into porous carbon particles proceeding from a gaseous or liquid silicon precursor. The intercalation process, also called sedimentation or filtration, can be carried out, for example, in a gas fluidized bed in US 10,508,335 B1.

[0007] It is common knowledge that gas fluidized beds are well suited for gas-solid reactions and therefore also for the intercalation process of silicon into porous particles.

[0008] In gas fluidized beds, a bed of solid particles is loosened and transported by an upwardly flowing gas to such an extent that the solid layer as a whole exhibits liquid-like characteristics [VDI-Waermeatlas [VDI Heat Atlas], 11th edition, Section L3.2, Stroemungsformen and Druckverlust in Wirbelschichten [Types of fluidization and pressure drop in fluidized beds], pp. 1371-1382, Springer Verlag, Berlin Heidelberg, 2013].

[0009] Gas fluidized beds are also commonly called fluidized beds, and the process of creating a fluidized bed is also called fluidization or fluidizing.

[0010] In gas fluidized beds, solid particles are very well dispersed. As a result, a very high contact area between the solids and the gas is formed, which can be ideally utilized for energy and mass transfer processes. Gas fluidized beds are generally characterized by very good mass and heat transfer operation and uniform temperature distribution. The quality of the mass and heat transfer processes is particularly important for the homogeneity of the products obtained by reactions in fluidized beds and can be correlated with the homogeneity of the fluidized state. Homogeneity of a homogeneous fluidized bed or fluidized state compared to a heterogeneous fluidized bed or heterogeneous fluidized state is characterized by high local heat transfer, small temperature differences within the fluidized bed, short mixing times of two particle populations with similar particle size and density, a small proportion of suspended particles, and a small proportion of stagnant domains within the fluidized bed.

[0011] Several methods are known for assessing the homogeneity of the fluidization state of a gas-fluidized bed. For example, the fluidization state can be described by the dimensionless fluidization index (FI), which represents the pressure drop measured across the bed as a ratio of the maximum pressure drop theoretically achievable in a fully formed fluidized bed. For a fully formed fluidized bed, a maximum value of 1 is obtained [Bizhaem, Hamed K., Tabrizi, Hassan B., Experimental study on hydrodynamic characteristics of gas-solid pulsed fluidized bed. In: Power Technology 237 (2013), pp. 14-23]. In practical implementation, the calculated value for FI may be slightly above 1 due to measurement accuracy. Another means of assessing the fluidization state is to measure the local heat transfer between any surface of the components in the fluidized bed and the bed itself. The magnitude of the heat transfer coefficient correlates with the homogeneity of the fluidized state of the fluidized bed [Baerns, M.: Effect of interparticle adhesive forces on fluidization of fine particles. In: Industrial & Engineering Chemistry Fundamentals 5(1966), no.4, pp.508-516].

[0012] Fluidization characteristics can be classified depending on particle size and solid density. 50 is less than 20 μm and the density difference between the particle and the gas is 100 kg / m 3Particles exceeding this size are included in Gerdart's Class C (cohesive) [Gerdart, D., Types of Gas Fluidization, Power Technol., 7, 1973, 285-292]. Gerdart C particles are characterized by their difficulty in converting to a fluidized state. Due to their small particle size, the effects of interparticle attraction are comparable to or greater than the forces acting on the primary particles due to the gas flow. Corresponding effects include overall bed defluidization and / or channelization. In the case of channelization, rather than fluidization, tubes form within the particle bed through which the fluidizing gas flows preferentially, while there is no flow through the bulk of the bed. As a result, fluidization homogeneity is not achieved. If the gas velocity is increased significantly above the minimum fluidization velocity of the primary particles in the bed, agglomerates of individual particles form over time, which can be fully or partially fluidized. Typical behavior is the formation of layers with agglomerates of different sizes. The bottom layer, directly above the inflow base, contains very large agglomerates, which move very little, if at all. In the layers above, there are smaller, fluidized agglomerates. The top layer contains the smallest agglomerates, which are partially entrained by the gas flow and are problematic from an engineering point of view. The fluidization characteristics of such particle beds are characterized by the formation of larger gas bubbles and a small expansion of the fluidized bed. In the English literature, this behavior is called "agglomerate bubbling fluidization" (ABF). [Shabanian, J., Jafari, R., Chaouki, J., Fluidization of Ultrafine Powders, IRECHE., Vol. 4, No. 1, 16-50].

[0013] It will be apparent to those skilled in the art that ABF fluidized beds are unsuitable for producing materials with homogeneous properties due to the heterogeneity within the fluidized bed and the associated non-homogeneous mass and heat transfer conditions.

[0014] Known fluidization to convert Geldart Class C particles into a predominantly homogeneous fluidized bed in the form of weak agglomerates. auxiliaryUS 7,658,340 B2 describes that the introduction of additional force components, such as vibration, magnetic, acoustic, rotational, or centrifugal forces, or a combination thereof, as well as the force exerted by a fluidizing gas, influence the size of weak agglomerates consisting of SiO2 nanoparticles (Geldart Classification C) in the fluidized bed so as to form a primarily homogeneous fluidized bed. The homogeneity of the fluidized bed is visually evaluated by the mixing and fluidization index of colored and non-colored particles. A homogeneous fluidized bed is characterized by a fluidization index close to 1, a clearly distinguishable bed expansion, a homogeneous appearance, a low particle shedding rate, and a short mixing time of 2 minutes.

[0015] Another method for fluidizing Geldart C particles is the introduction of a pulsed fluidization gas flow. Akhavan et al. [Akhavan, A., Rahman, F., Wang, S., Rhodes, M., Enhanced fluidization of nanoparticles with gas phase pulsation assistance, Powder Technol., 284, 2015, 521-529] described the effect of a pulsed fluidization gas flow on the fluidization characteristics of SiO2 and TiO2 particles (Geldert C and ABF grades) in a fluidized bed. The homogeneity of the fluidization was evaluated visually and by pressure drop measurements. The use of gas breaks down the gas channels and transforms the fluidized bed into a visually homogeneous state with a significantly larger bed expansion than without pulsation. Pressure drop measurements allowed for the transformation of the complete particle bed into a fluidized bed. It was also found that fluidization with pulsation was achieved at a lower minimum fluidization velocity than without pulsation.

[0016] Cadoret et al. [Cadoret, L., Reuge, N., Pannala, S., Syamlal, M., Rossignol, C., Dexpert-Ghys, J., Coufort, C., Caussat, B., Silicon Chemical Vapor Deposition on Macro and Submicron Powders in a Fluidized Bed, Powder Technol., 190, 185-191, 2009] described the deposition of silicon from monosilane SiH4 onto submicrometer-sized (Geldart C grade) nonporous titanium dioxide particles in a vibrating fluidized-bed reactor. The goal of this work was to uniformly coat TiO2 particles without any primary particle size. The vibration input restricted weak agglomerates to a size range of 300–600 μm within the fluidized bed. Pressure drop measurements indicated that the complete particle bed was fluidized during the coating reaction. Uniform reaction conditions throughout the fluidized-bed reactor were demonstrated by electron micrographs of uniformly coated particles removed at different locations within the reactor. Oscillating systems have disadvantages related to the economic viability of the process, as vibration adversely affects the strength of the reactor material and shortens the equipment's lifespan. Also disadvantages include the increased complexity of running an oscillating fluidized-bed reactor from a scaling perspective, and the use of highly reactive gases, such as those required for silicon deposition from gaseous silicon precursors in porous particles, making ensuring the integrity of such a fluidized-bed reactor critical from a safety perspective.

[0017] US 10,668,499 B2 describes a method for applying a surface coating to Geldart C-class particles, which may be porous, in a fluidized-bed reactor, in which an oscillating fluidizing gas flow is adjusted to form a standing wave of gas flow. The standing wave results in a uniform distribution of the particles in the fluidized-bed reactor. At the same time, the use of the standing wave makes it possible to deposit a thin layer on the surface with a uniform distribution over all particles. To create the standing wave, a reflector must be incorporated into the fluidized-bed reactor, which must be partially permeable to the reaction gas. Under the reaction conditions of the deposition process, the interior of such a reactor is very disadvantageous because the material being deposited can also accumulate on the reflector, which reduces the gas permeability to the point of complete blockage of the fluidized-bed reactor as the process time increases.

[0018] US 10,508,335 B1 describes a fluidized bed process for the deposition of silicon from SiH4 in a porous carbon matrix. However, in this case, the particle diameter d 50 Particles with sizes exceeding 50 μm are used to avoid the formation of large agglomerates of primary particles, because the formation of agglomerates would first create a heterogeneous fluidized bed, leading to homogeneous reaction conditions at the reactor level, while slow mass transfer within the agglomerates would also lead to heterogeneous reaction conditions at the agglomerate level. A drawback of the described method is that the resulting material for use as an anode material in lithium-ion batteries must be milled to the required size of less than 20 μm in a complex additional step. This additional step results in additional material loss, significantly limiting the economic attractiveness of the method. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] European Patent No. 1730800 [Patent Document 2] U.S. Patent No. 10,559,812 [Patent Document 3] U.S. Patent No. 10,819,400 [Patent Document 4] European Patent No. 3335262 [Patent Document 5] U.S. Patent No. 10,508,335 [Patent Document 6] U.S. Patent No. 7,658,340 [Patent Document 7] U.S. Patent No. 10,668,499 [Non-patent literature]

[0020] [Non-Patent Document 1] M.Obrovac, VL Chevrier Chem. Rev.2014, 114, 11444 [Non-patent document 2] VDI-Waermeatlas [VDI Heat Atlas], 11th edition, Section L3.2, Stroemungsformen and Druckverlust in Wirbelschichten [Types of flow and pressure drop in fluidized beds], pp. 1371-1382, Springer Verlag, Berlin Heidelberg, 2013 [Non-patent document 3] Bizhaem, Hamed K., Tabrizi, Hassan B., Experimental study on hydrodynamic characteristics of gas-solid pulsed fluidized bed. In: Power Technology 237(2013), p.14-23 [Non-patent document 4] Baerns, M.: Effect of interparticle adhesive forces on fluidization of fine particles. In: Industrial & Engineering Chemistry Fundamentals 5(1966), no.4, p.508-516 [Non-patent document 5] Gerdart, D., Types of Gas Fluidization, Power Technol., 7, 1973, 285-292. [Non-patent document 6] Shabanian, J., Jafari, R., Chaouki, J., Fluidization of Ultrafine Powders, IRECHE., Volume 4, N.1, 16-50. [Non-Patent Document 7] Akhavan, A., Rahman, F., Wang, S., Rhodes, M., Enhanced fluidization of nanoparticles with gas phase pulsation assistance, Powder Technol., 284, 2015, 521-529 [Non-patent document 8] Cadoret, L., Reuge, N., Pannala, S., Syamlal, M., Rossignol, C., Dexpert-Ghys, J., Coufort, C., Caussat, B., Silicon Chemical Vapor Deposition on macro and submicron powders in a fluidized bed, Powder Technol., 190, 185-191, 2009 Summary of the Invention [Problem to be solved by the invention]

[0021] Against this background, the problem addressed was to provide a technically feasible method for producing silicon-containing materials by depositing silicon in the pores and on the surface of porous particles by thermal decomposition of at least one silicon precursor in a fluidized-bed reactor with sufficiently homogeneous fluidization, which results in silicon-containing materials with a high lithium ion storage capacity and high cycling stability when used as active material in the anode of a lithium-ion battery, and which avoids the drawbacks of the methods described in the prior art, particularly with regard to the insufficient homogeneity of the product. [Means for solving the problem]

[0022] Surprisingly, it has been found that the above-mentioned problems associated with prior art methods for the deposition of silicon from silicon precursors into or onto porous particles can be effectively solved by carrying out the deposition in a fluidized bed using a fluidizing gas flow having a wave-shaped pulsating effect on the fluidized bed so as to form a homogeneous fluidized bed characterized by a fluidization index of FI≧0.95. In a preferred embodiment, the homogeneous fluidized bed has a maximum heat transfer coefficient α between any surface of the components present in the fluidized bed and the fluidized bed itself. max The heat transfer coefficient α between any surface of the component present in the fluidized bed and the fluidized bed itself is based on α / α max ≧0.95.

[0023] Furthermore, it has surprisingly been found that in the inventive deposition of silicon from gaseous silicon precursors, even when agglomerates are formed in the fluidized bed, it is possible to produce a homogeneously infiltrated product both within the agglomerates and throughout the fluidized bed reactor due to the internal porosity.

[0024] The present invention provides a method for producing silicon-containing materials in a fluidized bed reactor by depositing silicon from at least one silicon precursor in the pores and on the surface of porous particles, characterized in that a fluidizing gas flow propagates in the fluidized bed reactor in a pulsating wave form and acts on the fluidized bed to form a homogeneous fluidized bed characterized by a fluidization index FI of at least 0.95. Therefore, the fluidization index FI is generally selected from the range of 0.95 to 1.

[0025] In a preferred embodiment, the fluidized bed has a maximum heat transfer coefficient α between any surface of the components present in the fluidized bed and the fluidized bed itself. max The heat transfer coefficient α between any surface of the component present in the fluidized bed and the fluidized bed itself is based on α / α max ≧0.95.

[0026] The primary particles of porous particles as fine particles can generally only be fluidized with the formation of weak agglomerates, if any. Therefore, it is all the more surprising that the method of the present invention results in a uniform volume of silicon within and on the porous particles. The resulting silicon-containing material can be advantageously used as the active material for the anode of a lithium-ion battery, and the uniform deposition of silicon within the pores and on the surface of the porous particles allows for the provision of lithium-ion batteries with very high cycle stability.

[0027] The method of the present invention preferably comprises the following steps: Step 1: Packing porous particles into a fluidized bed reactor; A second step: fluidizing the porous particles with at least one internal gas as a fluidizing gas and adjusting the temperature of the fluidized bed reactor to a temperature for conversion in a third step; Third step: fluidizing with at least one internal gas as a fluidizing gas with the addition of a reactive gas containing one or more silicon precursors to convert the silicon precursors and deposit silicon in the pores and on the surface of the porous particles; Fourth step: cooling the fluidized bed reactor and fluidizing it with at least one inert gas as the fluidizing gas; Step 5: Removing the reaction product from the fluidized bed reactor.

[0028] In the first stage, a fluidized bed reactor is packed with porous particles.

[0029] In the second stage, the porous particles, also commonly referred to as a "particle bed," are fluidized and generally simultaneously purged by feeding at least one inert gas. The inert gas selected is preferably a gas or gas mixture selected from the group comprising hydrogen, helium, neon, argon, nitrogen, and forming gas, with the use of nitrogen or argon being particularly preferred. The inert gas components of the fluidizing gas are preferably present in an amount of at least 50%, more preferably at least 90%, and most preferably at least 99%, based on the partial pressure of the inert gas components in the total pressure of the fluidizing gas under standard conditions (according to DIN 1343).

[0030] More specifically, the method is characterized in that the fluidizing gas flow is induced to propagate in a pulsating wave form through the fluidized-bed reactor, or, in other words, to oscillate in a pulsed manner. Advantageously, the transmission of gas oscillations to the fluidized bed makes it possible to avoid the adverse fluidization characteristics of Geldart Class C particles. The fluidizing gas flow can be, for example, fully or partially pulsating. When the overall fluidizing gas flow is composed of pulsed and non-pulsated fluidizing gas substreams, the ratio of the pulsed fluidizing gas substreams to the overall fluidizing gas flow is preferably in the range of 0.1 to 1, more preferably 0.3 to 1, and particularly preferably 0.5 to 1. The oscillation can be induced, for example, in the form of a square profile, a triangular profile, a sawtooth profile, a sinusoidal profile, or any combination thereof. The frequency of the oscillation, given by the reciprocal of the period duration, is preferably in the range of 0.1 to 20 Hz, preferably 0.5 to 10 Hz, and more preferably 0.5 to 6 Hz. The duty factor, which describes the ratio of pulse duration to periodic time, is preferably in the range of 0.1 to 0.9, more preferably in the range of 0.2 to 0.8. The induced oscillation is preferably periodic with a constant frequency, pulse shape, and duty factor. In a more preferred embodiment, the fluidizing gas flow is made to oscillate with a frequency and / or pulse shape and / or duty factor that varies over time. The pulsed fluidizing gas flow preferably enters the fluidized-bed reactor through a gas-permeable base. Undesirable effects, such as channel formation or uncontrolled agglomerate growth, can be prevented, for example, by adjusting the fluidizing gas flow, preferably instantaneously, to a value within the desired working range.

[0031] The process is preferably carried out with a fluidizing gas stream having a superficial velocity above the measured minimum fluidization velocity of the pulsed gas stream, with the preferred operating range being between 1 and 10 times the measured minimum fluidization velocity, preferably between 2 and 8 times the measured minimum fluidization velocity, and more preferably between 2 and 5 times the measured minimum fluidization velocity.

[0032] The method is also characterized in that the fluidized state of the fluidized bed is characterized by a dimensionless fluidization index FI ≥ 0.95. The fluidization index FI is determined by the pressure drop across the fluidized bed Δp ws,measured and the theoretically achievable maximum pressure drop p ws,th It is defined as the ratio of

[0033]

number

[0034] The theoretically achievable maximum pressure drop is given by the mass of the bed m, ignoring the gas density. S , acceleration due to gravity g, cross-sectional area A WS From Δp WS,th =m S g / A WS Other parameters for determining the fluidization index can be found further below at the beginning of the example description.

[0035] This method determines the maximum heat transfer coefficient α between any surface of the component present in the fluidized bed and the fluidized bed itself. max The heat transfer coefficient α between any surface of the component present in the fluidized bed and the fluidized bed itself is α / α max Preferably, it is characterized in that the ratio is ≧0.95.

[0036] Similar to fluidization, the second stage involves continuing to pulse at least one fluidizing gas while adjusting the temperature of the fluidized bed reactor to a temperature for reaction in the third stage.

[0037] The conversion in the third stage generally refers to the decomposition of the silicon precursor with the deposition of silicon within the pores and on the surface of the porous particles.

[0038] In a third stage, particularly after attainment of the temperature for silicon deposition, fluidization of the fluidized bed is generally continued by pulsed supply of at least one inert gas to the fluidized bed and supply of a reactive gas, which is preferably supplied as a partial to complete addition to the inert gas stream, in other words as a constituent of the fluidizing gas or elsewhere in the reaction space independently of the fluidizing gas.

[0039] The inert gas constituents of the fluidizing gas are preferably present in an amount of at least 50%, based on the partial pressure of the inert gas constituents in the total pressure of the fluidizing gas under standard conditions (according to DIN 1343).

[0040] The reaction temperature or the temperature for silicon deposition is preferably in the range of 100 to 1000°C, more preferably in the range of 300 to 900°C, and particularly preferably in the range of 380 to 750°C.

[0041] The deposition of silicon is preferably carried out in a pressure range between 0.1 and 5 bar, more preferably at atmospheric pressure.

[0042] The supply of reactive gas preferably does not substantially change the fluidization state. The fluidized bed is still characterized by a fluidization index FI≧0.95. In a further embodiment, the fluidized bed is characterized by a maximum coefficient of heat transfer α between any surface of the components present in the fluidized bed and the fluidized bed itself, given an optimal fluidization of the fluidized bed at a given fluidizing gas temperature and composition. max The coefficient of heat transfer α between any surface of the component present in the fluidized bed and the fluidized bed itself is α / α max Preferably, it is characterized in that the ratio is ≧0.95.

[0043] The reactive gas used in the third step comprises at least one or more silicon precursors. As well as the silicon precursor, the reactive gas may comprise an inert gas. The reactive gas preferably comprises more than 50%, more preferably more than 80%, particularly preferably more than 90% of the inert gas, based on the partial pressure of the inert gas in the total pressure of the reactive gas under standard conditions (DIN 1343).

[0044] Silicon precursors generally contain at least one reactive component that can react to provide silicon under thermal treatment. The reactive component is a silicon-hydrogen compound, such as monosilane SiH4, disilane Si2H6, and higher linear, branched, or cyclic analogs, such as neopentasilane Si5H. 12 , cyclohexasilane Si6H 12 Preferably selected from the group comprising chlorinated silanes such as trichlorosilane HSiCl3, dichlorosilane H2SiCl2, chlorosilane H3SiCl, tetrachlorosilane SiCl4, hexachlorodisilane Si2Cl6 and higher linear, branched or cyclic analogues such as 1,1,2,2-tetrachlorodisilane Cl2HSi-SiHCl2, chlorinated and partially chlorinated oligo- and polysilanes, methylchlorosilanes such as trichloromethylsilane MeSiCl3, dichlorodimethylsilane Me2SiCl2, chlorotrimethylsilane Me3SiCl, tetramethylsilane Me4Si, dichloromethylsilane MeHSiCl2, chloromethylsilane MeH2SiCl, methylsilane MeH3Si, chlorodimethylsilane Me2HSiCl, dimethylsilane Me2H2Si, trimethylsilane Me3SiH or mixtures of the mentioned silicon compounds.

[0045] Particularly preferred reactive components are monosilanes SiH4, oligomeric or polymeric silanes, especially those of the general formula SiH4, where n can be an integer in the range of 2 to 10. n H n+2 and linear silanes of the general formula -[SiH2], where n may include an integer ranging from 3 to 10. n -, trichlorosilane HSiCl3, dichlorosilane H2SiCl2 and chlorosilane H3SiCl, which can be used on their own or in mixtures, with very particular preference being given to using SiH4, HSiCl3 and H2SiCl2 on their own or in mixtures.

[0046] Furthermore, the reactive gas may contain further components, such as dopants based on compounds containing boron, nitrogen, phosphorus, arsenic, germanium, iron or nickel, which are preferably selected from the group comprising ammonium NH3, diborane B2H6, phosphine PH3, germane GeH4, arsane AsH3 and nickel tetracarbonyl Ni(CO)4.

[0047] During the third stage, the temperature is generally kept constant or can be varied by heating or cooling. In order to obtain a material with particularly homogeneous properties, a substantially spatially uniform conversion of the silicon precursor within the pores and on the surface of the porous particles is preferred.

[0048] To control the reaction rate of the conversion of the silicon precursor in the third stage, different technical solutions can be used. It is preferred to increase or decrease the heat supply in the fluidized-bed reactor. This can increase or decrease the conversion rate, for example. The removal of heat from the fluidized-bed reactor is preferably facilitated by cooling, for example, by cooling one or more reactor walls or by introducing a heat removal device, such as a coolable plate, tube, or tube bundle, into the fluidized-bed reactor. For example, this can slow down the reaction rate. More preferably, the reaction gas composition is changed to very quickly control the reaction rate.

[0049] The progress of the conversion of the reactive gas in the third stage is preferably monitored by analysis. In this way, it is possible, for example, to recognize the achievement of a desired amount of deposited silicon and, as a result, to minimize the time occupied by the reactor. Such methods preferably include, for example, temperature measurements to determine exothermic or endothermic reactions, pressure measurements to check the progress of the conversion by, for example, varying the ratio of solid to gaseous components of the reactor contents, and further methods that, for example, allow the observation of the various compositions of the gas space during the conversion of the reactive gas.

[0050] In a further preferred embodiment, in the third stage, particularly after a desired residence time, a portion of the formed silicon-containing material is removed from the fluidized bed reactor, while the porous particles are replenished, more preferably by a quantity of porous particles corresponding to the portion of the removed silicon-containing material. At the desired residence time, sufficient conversion of the silicon precursor or sufficient deposition of silicon in or on the porous particles is achieved. This point can be confirmed, for example, by gas chromatography analysis of the gas stream leaving the fluidized bed reactor.

[0051] In the fourth stage, preferably after the conversion of the reactive gas is completed, the fluidizing gas for the pulsed fluidization of the fluidized-bed reactor is switched to a gas stream containing an inert gas, more preferably pure inert gas. In this way, it is possible, for example, to remove reactive components from the fluidized-bed reactor. The components of the inert gas stream used are preferably inert gases selected from the group including hydrogen, helium, neon, argon, or nitrogen, or forming gas, optionally with the addition of air. Particular preference is given here to nitrogen, argon, air, or mixtures thereof. Preference is given to simultaneously cooling the temperature of the fluidized-bed reactor to the desired lower temperature, more preferably to 20-50°C, particularly preferably to 20-30°C.

[0052] In a specific embodiment, the fluidized bed reactor is purged. Purging is preferably carried out with a mixture containing an inert gas and oxygen. This mixture preferably contains 20% by volume or less of oxygen, more preferably 10% by volume or less, and particularly preferably 5% by volume or less. The temperature here is preferably 200°C or less, more preferably 100°C or less, and particularly preferably 50°C or less. In this way, for example, the surface of the silicon-containing material can be modified, for example, passivated. For example, it is possible to achieve reaction of any reactive groups present on the surface of the silicon-containing material.

[0053] In the fifth step, the reaction products, particularly the silicon-containing material, are removed from the fluidized bed reactor, optionally maintaining an inert gas atmosphere in the fluidized bed reactor.

[0054] Measurement of temperature, pressure or pressure difference in a fluidized bed reactor can be determined using measuring devices and standard test methods for fluidized bed reactors. After normal calibration, different measuring devices give the same measurement results.

[0055] In a preferred embodiment, the sequence from the second stage to the fourth stage is repeatedly carried out. Here, it is particularly preferred not to remove the particles forming the fluidized bed from the fluidized bed reactor. Here, the silicon precursor used in each third stage can be the same or different. Here, it is possible to omit the fourth stage in one or more sequences. It is also preferred that the fourth stage is carried out in the last sequence.

[0056] In a further preferred embodiment, the sequence of the second, third, and optionally fourth stages is repeated, i.e., optionally omitting the fourth stage, but in this case, it is also possible to use a reactive gas that does not contain a silicon precursor in the third stage in one or more sequences, where the reactive gas that does not contain a silicon precursor can generally be the same or different in each sequence, but a reactive gas that contains a silicon precursor is used in at least one sequence. The reactive gas that does not contain a silicon precursor generally does not contain any silicon precursor. The reactive gas that does not contain a silicon precursor preferably contains one or more hydrocarbons. In this specific embodiment, the reactive gas that does not contain a silicon precursor can be used in a sequence before or after the silicon deposition, or can be used between two silicon depositions.

[0057] In a preferred specific embodiment, when a sequence of the second, third, and optional fourth steps is repeatedly performed, in the first sequence, a silicon precursor-containing reactive gas is used in the third step, and in the second sequence, a hydrocarbon-containing reactive gas not containing a silicon precursor is used in the third step. Here, it is preferable to be able to omit the fourth step in the first sequence. These embodiments provide a silicon-containing material that does not have an outer silicon surface.

[0058] In a more preferred specific embodiment, when the sequence of the second, third, and optionally fourth stages is performed multiple times, in the first sequence, a reactive gas containing a hydrocarbon but not a silicon precursor is used in the third stage, and in the second sequence, a reactive gas containing a silicon precursor is used. Optionally, in the third sequence, a reactive gas containing an additional hydrocarbon but not a silicon precursor can be used in the third stage. In this case, the fourth stage can be omitted in the first sequence after the third stage and / or in the second sequence after the third stage. In this way, it is possible to obtain, for example, a silicon-containing material having a carbon layer between the porous particles and the deposited silicon, and optionally additionally carrying an outer carbon layer, so that there is no outer silicon surface.

[0059] Examples of reactive gases that do not contain silicon precursors that can be used include any gas or mixture of gases that can be converted into a solid by increasing the temperature. Examples of these include aliphatic hydrocarbons having 1 to 10 carbon atoms, especially 1 to 6 carbon atoms (preferably methane, ethane, propane, butane, pentane, isobutane, hexane, cyclopropane, cyclobutane, cyclopentane, cyclohexane, and cycloheptane), unsaturated hydrocarbons having 1 to 10 carbon atoms (e.g., ethene, acetylene, propene or butene, isoprene or butadiene, divinylbenzene, vinylacetylene, cyclohexadiene, cyclooctadiene), cyclic unsaturated hydrocarbons (e.g., cyclopropene, cyclobutene, cyclopentene, cyclohexene, cyclohexadiene, cyclopentadiene, dicyclopentadiene, or norbornadiene), aromatic hydrocarbons (e.g., benzene, toluene, p-, m-, o-xylene, styrene (vinylbenzene), ethylbenzene, diphenylmethane, or naphthyl ether). terylene), further aromatic hydrocarbons (for example, phenol, o-, m-, p-cresol, cymene, nitrobenzene, chlorobenzene, pyridine, anthracene, phenanthrene, myrcene, geraniol, thioterpineol, norbornane, borneol, isoborneol, bornane, camphor, limonene, terpinene, pinene, pinane, carene, phenol, aniline, anisole, furan, furfural, furfuryl alcohol, hydroxymethylfurfural or bishydroxymethylfuran and mixed fractions containing a number of these compounds (for example, mixed fractions from natural gas condensates, mineral oil distillates, coking oven condensates, product streams of fluid catalytic crackers (FCC), steam pyrolyzers or Fischer-Tropsch synthesis plants), or generally hydrocarbon-containing streams of materials from the processing of wood, natural gas, mineral oil and coal.

[0060] The reactive gas containing hydrocarbons and no silicon precursor can contain one hydrocarbon or a mixture of two or more hydrocarbons. The reactive gas containing hydrocarbons and no silicon precursor can be used without additional components or as a mixture with other reactive gases such as inert gases or hydrogen. Furthermore, the reactive gas containing hydrocarbons and no silicon precursor can also contain other reactive components, such as dopants based on compounds containing boron, nitrogen, phosphorus, arsenic, germanium, iron, or nickel. The dopants are preferably selected from the group consisting of ammonia NH3, diborane B2H6, phosphine PH3, germane GeH4, arsane AsH3, and nickel tetracarbonyl Ni(CO)4.

[0061] The fluidized bed reactor used may be of any design known to those skilled in the art. As is typical, the region of a fluidized bed reactor begins with a gas-permeable base in which a bed containing, for example, porous particles is fluidized, thus forming a fluidized bed.

[0062] The gas-permeable base is also called a gas distributor base or inflow base. Examples of these include porous plates, perforated plates, nozzle trays, bubble cap trays, manufacturer-specific or proprietary designs, or combinations thereof. For example, it is possible to introduce the inert components of the fluidizing gas into a fluidized-bed reactor through one type of tray, and to introduce the reactive gas into the fluidized-bed reactor as an addition or part of the fluidizing gas through another type of tray. In a preferred embodiment, the reactive gas is mixed with the fluidizing gas and forms a fluidized bed therewith as a component thereof. In a further embodiment, the reactive gas is supplied to the reaction space within a specific nozzle in the base plate parallel to the fluidizing gas. In a further preferred embodiment, the reactive gas is supplied to the fluidized-bed reactor at different locations removed from the base plate, for example, in countercurrent flow.

[0063] When the reactive gas is supplied in at least portions through the base plate of the fluidized bed reactor, it is preferable to cool the gas-permeable base to a temperature below the reaction temperature, thereby avoiding reaction of the reactive gas with the surface of the gas-permeable base.

[0064] With regard to the cross-sectional area of the fluidized bed reactor, preferred embodiments are circular, elliptical, square, rectangular, or substantially convex polygonal. The shape of the fluidized bed reactor in which the bed is fluidized is preferably implemented as a cylinder, an elliptical cylinder, or a prism with any base area. Above the region where the fluidized bed is formed, it is preferred to follow a clear expansion of the cross-sectional area. The design of this "settlement zone" is preferably carried out in a similar manner to the region where the fluidized bed is formed. In a further preferred embodiment, there is already a change in the cross-sectional area in the region of the fluidized bed, where the cross-sectional area can be of any shape. In addition, the fluidized bed reactor can in principle also be implemented as a circulating fluidized bed.

[0065] The outlet of the fluidizing gas from the fluidized-bed reactor is preferably designed so that particles entrained in the flow are separated from the fluidizing gas stream. The particles are preferably removed by mechanical filtration, particularly through filter cartridges, filter bags, filter pouches or filter hoses, or through electrostatic filters. A further preferred mode of deposition of solid particles from the gas stream is achieved by using a gravity separator, such as a cyclone or centrifugal sifter. A further preferred design is a combination, such as connecting a gravity separator upstream of a mechanical filter.

[0066] The filtration unit is preferably cooled to a temperature below the silicon volume temperature, in this way it is also possible to avoid undesired reactions between the reactive gases and the surface of the filtration material.

[0067] To generate pulsations in the fluidizing gas flow, different methods of inducing oscillations in the fluidizing gas flow are preferred. Fluidizing gas flow oscillations are preferably generated via pressure changes, more preferably via pneumatic and / or mechanical devices. Fluidizing gas oscillations are preferably generated by sudden changes in the fluidizing gas pressure in the flow supply device on the gas-permeable base, in the fluidized bed chamber itself, and / or at the gas outlet upstream or downstream of the filter, where the pressure changes are preferably generated via a ventilator and / or a shut-off valve. Thus, a valve in the gas supply stream is preferably periodically opened and closed. For example, the duration of the open and closed positions is used to adjust the pulsation frequency. A further preferred embodiment is the use of a rotating flap in the gas supply. For example, the pulsation frequency can be changed by setting the speed of the rotating flap.

[0068] An embodiment for generating a partially pulsed fluidizing gas stream is achieved by controlled division of gas streams in the gas feed to the fluidized-bed reactor, with one of the gas streams being induced to oscillate. Both gas streams may be introduced into the fluidized-bed reactor independently through a gas-permeable base, or may be mixed upstream of the gas-permeable base and introduced into the fluidized-bed reactor as a mixture. Closed-loop control of the two gas streams allows the ratio of the pulsed fluidizing gas stream to the total fluidizing gas stream to be fixed.

[0069] The process temperature can be controlled, for example, using a heating or cooling device. A preferred procedure is preheating the fluidizing gas in the feed to the fluidized-bed reactor. Heat is preferably transferred by radiation and convection. This preheating is preferably carried out by an electric fluidizing heater, a gas-fired fluidizing heater, a steam-based fluidizing heater, or a combination thereof. To establish the desired reaction temperature in the fluidized-bed reactor, heating and cooling of the fluidized bed is preferred. The fluidized bed is preferably heated and cooled by the heat transfer mechanisms of radiation, particle convection, and gas convection. Preferred implementations for heating the heat transfer surface are radiant ovens with heating elements, gas firing, steam heating, heating by heat transfer oil (e.g., WACKER Helisol® with heating medium temperatures up to 425°C), induction heating, or resistance heating devices. Heat energy is preferably exchanged between the heat transfer surface and the fluidized bed by irradiation, particle convection, and gas convection. The fluidized bed is also preferably heated by direct radiation, such as, for example, an infrared source or microwaves. A further preferred embodiment for heating the fluidized bed is direct induction heating of the fluidized bed.

[0070] Reactor cooling is preferably carried out by heat transfer to a flowing cooling medium, which may preferably be in liquid form or may be both liquid and gaseous due to boiling. Heat transfer surfaces for heating and cooling are preferably provided by the reactor walls and by internals of any shape and size in the fluidized bed, such as tubes, tube bundles or plates through which a fluid flows.

[0071] Fluidizing gas pulsation and further fluidization auxiliary Further preferred embodiments include a combination of the fluidized bed generated by the pulsation of the fluidizing gas and the mechanical vibration of the fluidized bed reactor. For example, the fluidized bed generated by the pulsation of the fluidizing gas can be mechanically moved by a stirring unit. Furthermore, the superposition of the pulsation of the fluidizing gas and the mechanical vibration of the fluidized bed reactor is preferred. Also preferred is a combination of the pulsation of the fluidizing gas and the introduction of an additional gas jet, which can be injected into the fluidized bed at a significantly higher gas velocity.

[0072] In principle, any material for the construction of a fluidized bed reactor must have the necessary mechanical strength under the respective process conditions. With regard to chemical stability, the fluidized bed reactor can be made of, for example, the corresponding pure material or a chemically unstable material (pressure-bearing) with a specific coating or plating on the parts that come into contact with the medium.

[0073] The material for the fluidized bed reactor is preferably a metallic material (DIN CEN ISO / TR 15608) (which corresponds to material groups 1 to 11 for steel, 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 (oxide ceramics in single-material systems, e.g., aluminum oxide, magnesium oxide, zirconium oxide, silicon dioxide, titanium dioxide (capacitor material), and multi-material systems, e.g., aluminum titanate (a mixed form of aluminum oxide and titanium oxide), mullite (a mixed form of aluminum oxide and silicon oxide), lead zirconate titanate (piezoceramics), and dispersed ceramics, e.g., zirconia-toughened aluminum oxide (ZTA-Al2O3 / ZrO2) and non-oxide ceramics (carbides, e.g., silicon carbide, boron carbide; nitrides, e.g., silicon nitride, aluminum nitride, boron nitride, titanium nitride). They are preferably selected from the group comprising: inorganic fillers, inorganic borides, inorganic silicides), and mixtures thereof, as well as composite materials that form part of the group of particulate composites (for example, cemented carbides, ceramic composites, concrete, polymer concrete), fiber composites (for example, glass fiber reinforced glass, metal matrix composites (MMC), fiber cement, carbon fiber reinforced silicon carbide, intrinsically reinforced thermoplastics, steel reinforced concrete, fiber concrete, fiber-polymer composites (for example, carbon fiber reinforced plastics (CFRP), glass fiber reinforced plastics (GFRP), aramid fiber reinforced plastics (AFK))), fiber-ceramic composites (ceramic matrix composites (CMC)), infiltrated composites or metal matrix composites (MMC) (for example, dispersion reinforced aluminum alloys or dispersion hardened NiCr superalloys), composite laminates (for example, bimetals, TiGr composites, composite sheets and tubes, glass fiber reinforced aluminum, sandwich structures).

[0074] The method of the present invention for producing silicon-containing materials offers various advantages over the prior art. A particular advantage is the production of a product with uniform properties in a single, efficiently scalable reaction step. Another advantage is improved mass and heat transfer via pulsation of the flowing gas stream. A further advantage is believed to be process control through specific adjustments of reaction temperature and reactive gas composition, which can be varied during the process. Furthermore, this process scheme allows for cyclic multiple depositions of all reactive gases, free of silicon precursors, from the same or different silicon precursors. These advantages, in particular, allow for rapid and economical access to silicon-containing materials for use as active materials in lithium-ion battery anodes with superior properties, in an advantageous manner.

[0075] The porous particles are preferably selected from the group comprising hard carbon, soft carbon, mesocarbon microbeads, natural or synthetic graphite, single and multi-walled carbon nano-beads for use with graphene, oxides selected from the group comprising silicon dioxide, aluminum oxide, mixed silicon-aluminum oxide, magnesium oxide, lead oxide and zirconium oxide, carbides selected from the group comprising silicon carbide and boron carbide, nitrides selected from the group comprising silicon nitride and boron nitride, and other ceramic materials that can be described by the following formula: Al a B b C c Mg d N e O f Si g , 0≦a, b, c, d, e, f, g≦1, at least two coefficients a~g>0, and a * 3+b * 3+c * 4+d * 2+g * 4≧e * 3+f * It is 2.

[0076] The ceramic material can be, for example, a binary, ternary, quaternary, pentanary, hexanary or heptanary compound. Preference is given to ceramic materials having the following formula:

[0077] Non-stoichiometric boron nitride BN with z=0.2-1 z ,

[0078] Non-stoichiometric carbon nitride CN with z=0.1-4 / 3 z ,

[0079] x=0.1~20 and z=0.1~20, x * 3+4≧z * 3 Boron carbonitride B x CN z ,

[0080] z=0.1~1 and r=0.1~1, 3≧r * 2+z * 3 Boron nitroxide BN z O r ,

[0081] x=0.1~2, z=0.1~1 and r=0.1~1, x * 3+4≧r * 2+z * 3 Boron carbonitride oxide B x CN z O r ,

[0082] x=0.1~2 and z=0.1~2, x * 4+4≧z * 2 is silicon carboxide Si x CO z ,

[0083] x=0.1~3 and z=0.1~4, x * 4+4≧z * 3, silicon carbonitride Si x CN z ,

[0084] w=0.1~3, x=0.1~2 and z=0.1~4, w * 4+x * 3+4≧z * 3, silicon borocarbonitride Si w B x CN z ,

[0085] w=0.1~3, x=0.10~2 and z=0.1~4, w * 4+x * 3+4≧z * 2 is silicon borocarbonoxide Si w B x CO z ,

[0086] v=0.1~3, w=0.1~2, x=0.1~4 and z=0.1~3, v * 4+w * 3+4≧x * 3+z * Silicon borocarbonitride oxide Si v B w CN x O z , and

[0087] u=0.1~2, v=0.1~2, w=0.1~4, x=0.1~2 and z=0.1~3, u * 3+v * 3+x * 4+4≧w * 3+z * 2, aluminum borosilicocarbonitride oxide Al u B v Si x CN w O z .

[0088] Porous particles are determined by helium pycnometry and have a particle size of 0.1-7 g / cm 3 , more preferably 0.3 to 3 g / cm 3 This is the gravimetric capacity (mAh / cm) of a lithium-ion battery. 3 ) is advantageous for increasing

[0089] The porous particles used are preferably amorphous carbon, silicon dioxide, boron nitride, silicon carbide and silicon nitride, or mixed materials based on these materials, with preference being given to the use of amorphous carbon, boron nitride and silicon dioxide.

[0090] The porous particles preferably have a diameter percentile d of 0.5 μm or more, more preferably 1.5 μm or more, and most preferably 2 μm or more. 50 The diameter percentile d 50 is preferably 20 μm or less, more preferably 12 μm or less, and most preferably 8 μm or less.

[0091] The volume-weighted particle size distribution of the porous particles is preferably determined by the diameter percentile d 10 ≧0.2μm~d 90 ≦20.0 μm, more preferably d 10 ≧0.4μm~d 90 ≦15.0 μm, most preferably d 10 ≧0.6μm~d 90 ≦12.0 μm.

[0092] The porous particles preferably have a diameter percentile d of 10 μm or less, more preferably 5 μm or less, particularly preferably 3 μm or less, and most preferably 2 μm or less. 10 The diameter percentile d 10 is preferably 0.2 μm or more, more preferably 0.5 μm or more, and most preferably 1 μm or more.

[0093] The porous particles preferably have a diameter percentile d of 4 μm or more, more preferably 10 μm or more. 90 The diameter percentile d 90 is preferably 18 μm or less, more preferably 15 μm or less, and most preferably 13 μm or less.

[0094] The volume-weighted particle size distribution of the porous particles preferably has a span d of 15.0 μm or less, more preferably 12.0 μm or less, particularly preferably 10.0 μm or less, particularly preferably 8.0 μm or less, and most preferably 4.0 μm or less. 90 -d 10 The volume-weighted particle size distribution of the porous particles preferably has a span d of 0.6 μm or more, more preferably 0.8 μm or more, and most preferably 1.0 μm or more. 90 -d 10 It has.

[0095] The volume weighted particle size distribution of porous particles can be determined according to ISO 13320 by static laser scattering using the Mie model on a Horiba LA 950 measuring instrument with ethanol as the dispersion medium for the porous particles.

[0096] The porous particles are preferably in the form of particles. The particles may be, for example, in an isolated or agglomerated form. The porous particles are preferably not agglomerated, and preferably not agglomerated. Generally, "agglomeration" means that primary particles are initially formed and then fused together during the porous particle manufacturing process, and / or the primary particles are bonded to each other, for example, via covalent bonds, thus forming agglomerates. Primary particles are generally isolated particles. Agglomerates or isolated particles may form agglomerates. Agglomerates are loose coalescences of agglomerates or primary particles bonded to each other, for example, via van der Waals interactions or hydrogen bonds. Agglomerates that have agglomerated can be easily broken down into agglomerates again by standard kneading and dispersion methods. Agglomerates can only partially, if at all, be broken down into primary particles by these methods. The presence of porous particles in the form of agglomerates, agglomerates, or isolated particles can be visualized, for example, by conventional scanning electron microscopy (SEM). In contrast, static light scattering methods for determining the particle size distribution or particle size of matrix particles cannot distinguish between agglomerates and agglomerates.

[0097] The porous particles can have any desired morphology and thus can be, for example, sputtery, plate-like, spherical, or acicular, with sputtery and spherical particles being preferred.

[0098] The morphology can be characterized, for example, by the sphericity Ψ or sphericity S. According to Wadell's definition, sphericity Ψ is the ratio of the surface area of a sphere of equal volume to the actual surface area of the object. For a sphere, the value of Ψ is 1. According to this definition, the porous particles preferably have a sphericity Ψ of 0.3 to 1.0, more preferably 0.5 to 1.0, and most preferably 0.65 to 1.0.

[0099] The sphericity S is the ratio of the circumference of an equivalent circle having the same area A as the projection of the particle onto the surface to the measured circumference U of this projection,

[0100]

number

[0101] The porous particles are preferably 0.2 cm 3 / g or more, more preferably 0.6 cm 3 / g or more, most preferably 1.0 cm 3 / g or more, which is useful for obtaining high-capacity lithium-ion batteries. The gas-accessible pore volume was determined by gas absorption measurements with nitrogen according to DIN 66134.

[0102] The porous particles are preferably open-pore. Open pore generally means that the pores are connected to the surface of the particle via channels and are preferably in a state of mass transfer with the surroundings, especially the transfer of gaseous compounds. This can be verified using gas absorption measurements (evaluated by Brunauer, Emmett and Teller, "BET"), i.e., gas absorption measurements of the specific surface area. The porous particles are preferably 50 m 2 / g or more, more preferably 500m 2 / g or more, most preferably 1000m 2 / g or more, the BET specific surface area being determined in accordance with DIN 66131 (with nitrogen).

[0103] The pores of the porous particles can have any desired diameter, i.e., generally in the range of macropores (greater than 50 nm), mesopores (2-50 nm), and micropores (less than 2 nm). Porous particles can be used in any desired mixture of different pore types. Preference is given to using porous particles with less than 30% macropores, based on the total pores, more preferably porous particles without macropores, and very preferably porous particles with at least 50% pores with an average pore diameter of less than 5 nm. Very particularly preferred, the porous particles contain only pores with a pore diameter of less than 2 nm (determination method: pore size distribution by BJH (gas adsorption) according to DIN 66134 in the mesopore range and pore size distribution by Horvath-Kawazoe (gas adsorption) according to DIN 66135 in the micropore range; evaluation of the pore size distribution in the macropore range is carried out by mercury porosimetry according to DIN ISO 15901-1).

[0104] The preferred porous particles are 0.3 cm 3 / g, more preferably less than 0.15 cm 3 The gas inaccessible pore volume is less than 1 / g. In this way, it is possible to increase the capacity of lithium ion batteries. The gas inaccessible pore volume can be calculated using the following formula: Gas inaccessible pore volume = 1 / pure material density - 1 / skeletal density

[0105] The pure material density referred to here is the theoretical density of the porous particles and is based on the phase composition or density of the pure material (the density of the material as if it had no closed porosity). Data regarding pure material density can be found by those skilled in the art, for example, at the Ceramic Data Portal of the National Institute of Standards and Technology (NIST, https: / / srdata.nist.gov / CeramicDataPortal / scd). For example, the pure material density of silicon oxide is 2.203 g / cm. 3 The density of pure boron nitride is 2.25 g / cm 3 The density of pure silicon nitride is 3.44 g / cm 3 The density of pure silicon carbide is 3.21 g / cm 3 Skeletal density is the actual density of the porous particles (gas accessible) determined by helium pycnometry.

[0106] For clarity, it should be noted that the porous particles are different from silicon-containing materials. The porous particles serve as the starting material for producing silicon-containing materials. There is preferably no silicon present within the pores of the porous particles and on the surface of the porous particles, more specifically no silicon obtained by deposition of a silicon precursor.

[0107] By means of the process according to the invention, it is quite surprisingly possible to fluidize porous particles belonging to the Geldart C class in a fluidized bed by means of a pulsed fluidizing gas flow.

[0108] The silicon-containing material obtained by the deposition of silicon in the pores and on the surface of the porous particles preferably has a diameter d in the range of 0.5 to 20 μm. 50 The particle size distribution has a volume weighted value of d 50 Preferably, the value is at least 1.5 μm, more preferably at least 2 μm. Diameter percentile d 50 is preferably at most 13 μm, more preferably at most 8 μm.

[0109] The volume weighted particle size distribution of the silicon-containing material is preferably determined by the diameter percentile d 10≧0.2μm~d 90 ≦20.0 μm, more preferably d 10 ≧0.4μm~d 90 ≦15.0 μm, most preferably d 10 ≧0.6μm~d 90 ≦12.0 μm.

[0110] The silicon-containing material preferably has a diameter percentile d of 10 μm or less, more preferably 5 μm or less, particularly preferably 3 μm or less, and most preferably 1 μm or less. 10 The diameter percentile d 10 is preferably 0.2 μm or more, more preferably 0.4 μm or more, and most preferably 0.6 μm or more.

[0111] The silicon-containing material preferably has a diameter percentile d of 5 μm or more, more preferably 10 μm or more. 90 The diameter percentile d 90 is preferably 20 μm or less, more preferably 15 μm or less, and most preferably 12 μm or less.

[0112] The volume weighted particle size distribution of the silicon-containing material preferably has a span d of 15.0 μm or less, more preferably 12.0 μm or less, more preferably 10.0 μm or less, particularly preferably 8.0 μm or less, and most preferably 4.0 μm or less. 90 -d 10 The volume weighted particle size distribution of the silicon-containing material preferably has a span d of 0.6 μm or more, more preferably 0.8 μm or more, and most preferably 1.0 μm or more. 90 -d 10 It has.

[0113] The silicon-containing material is preferably in the form of particles. The particles can be isolated or agglomerated. The silicon-containing material is preferably not agglomerated, and more preferably not agglomerated. The terms isolated, agglomerated and not agglomerated have already been defined above in relation to the porous particles. The presence of the silicon-containing material in the form of agglomerates or agglomerates can be visualized, for example, by conventional scanning electron microscopy (SEM).

[0114] The silicon-containing material may have any desired morphology, and thus may be, for example, sputtered, plate-like, spherical, or acicular, with sputtered or spherical particles being preferred.

[0115] According to Wadell's definition, sphericity Ψ is the ratio of the surface area of a sphere of equal volume to the actual surface area of the object. For a sphere, the value of Ψ is 1. According to this definition, the silicon-containing material preferably has a sphericity Ψ of 0.3 to 1.0, more preferably 0.5 to 1.0, and most preferably 0.65 to 1.0.

[0116] The sphericity S is the ratio of the circumference of an equivalent circle having the same area A as the projection of the particle onto the surface to the measured circumference U of this projection,

[0117]

number

[0118] The cycling stability of lithium-ion batteries can be further enhanced by the morphology, material composition, especially the specific surface area or internal porosity of silicon-containing materials.

[0119] The silicon-containing material preferably comprises 10 to 90 wt. %, more preferably 20 to 80 wt. %, very preferably 30 to 60 wt. %, and particularly preferably 40 to 50 wt. % of porous particles, based on the total weight of the silicon-containing material.

[0120] The silicon-containing material preferably contains 10 to 90 wt. %, more preferably 20 to 80 wt. %, very preferably 30 to 60 wt. %, and especially preferably 40 to 50 wt. % silicon obtained by deposition from a silicon precursor, based on the total weight of the silicon-containing material (preferably determined by elemental analysis such as ICP-OES).

[0121] When the porous particles comprise a silicon compound in the form of silicon dioxide, for example, the above weight percent value for silicon obtained by deposition from a silicon precursor can be determined by subtracting the mass of silicon in the porous particles as determined by elemental analysis from the mass of silicon in the silicon-containing material as determined by elemental analysis, and dividing the result by the mass of the silicon-containing material.

[0122] The volume of silicon contained in the silicon-containing material and obtained by deposition from a silicon precursor is the product of the mass fraction of silicon obtained by deposition from the silicon precursor as a percentage of the total mass of the silicon-containing material, and the density of silicon (2.336 g / cm 3 ) is divided by

[0123] The pore volume P of a silicon-containing material is the product of the gas-accessible pore volume plus the gas-inaccessible pore volume. The Gurwitsch gas-accessible pore volume of a silicon-containing material can be determined by nitrogen gas sorption measurements according to DIN 66134.

[0124] The gas inaccessible pore volume of a silicon-containing material can be determined by the following formula: Gas inaccessible pore volume = 1 / pure material density - 1 / skeletal density

[0125] Here, the pure material density of the silicon-containing material is a theoretical density that can be calculated by multiplying the sum of the theoretical pure material densities of the components contained in the silicon-containing material by the percentage ratio of each component by weight in the entire material. Thus, for example, for a silicon-containing material in which silicon is deposited on porous particles, Pure material density = theoretical pure material density of silicon x silicon proportion (wt%) + theoretical pure material density of porous particles x porous particle proportion (wt%).

[0126] Data on pure material density can be obtained by those skilled in the art, for example, from the Ceramic Data Portal of the National Institute of Standards and Technology (NIST, https: / / srdata.nist.gov / CeramicDataPortal / scd). For example, the pure material density of silicon oxide is 2.203 g / cm. 3 The density of pure boron nitride is 2.25 g / cm 3 The density of pure silicon nitride is 3.44 g / cm 3 The density of pure silicon carbide is 3.21 g / cm 3 is.

[0127] The pore volume P of the silicon-containing material is in the range of 0 to 400 vol%, preferably in the range of 100 to 350 vol%, and more preferably in the range of 200 to 350 vol%, based on the volume of silicon contained in the silicon-containing material and obtained from the deposition of the silicon precursor.

[0128] The porosity contained in the silicon-containing material can be both gas-accessible and gas-inaccessible. The volume ratio of the gas-accessible porosity to the gas-inaccessible porosity of the silicon-containing material can generally be in the range of 0 (no gas-accessible pores) to 1 (all pores are gas-accessible). The volume ratio of the gas-accessible porosity to the gas-inaccessible porosity of the silicon-containing material is preferably in the range of 0 to 0.8, more preferably in the range of 0 to 0.3, and particularly preferably in the range of 0 to 0.1.

[0129] The pores of the silicon-containing material can have any desired diameter, for example, within the range of macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm). The silicon-containing material may also contain any desired mixture of different pore types. The silicon-containing material preferably contains up to 30% macropores, based on the total pore volume. Silicon-containing materials without macropores are particularly preferred, and silicon-containing materials having at least 50% pores, based on the total pore volume, with an average pore diameter of less than 5 nm are highly preferred. The silicon-containing material more particularly preferably contains only pores with a diameter of up to 2 nm.

[0130] The silicon-containing material comprises silicon structures having a structure size in at least one dimension of preferably up to 1000 nm, more preferably less than 100 nm, and very preferably less than 5 nm (determination by scanning electron microscope (SEM) and / or high-resolution transmission electron microscope (HR-TEM)).

[0131] The silicon-containing material preferably comprises a silicon layer having a layer thickness of less than 1000 nm, more preferably less than 100 nm, and very preferably less than 5 nm (determination method: scanning electron microscope (SEM) and / or high-resolution transmission electron microscope (HR-TEM)). The silicon-containing material may also comprise silicon in the form of particles. The silicon particles have a diameter of at most 1000 nm, more preferably less than 100 nm, and very preferably less than 5 nm (determination method: scanning electron microscope (SEM) and / or high-resolution transmission electron microscope (HR-TEM)). The numerical values for silicon particles herein are preferably based on the diameter of a circle around the particle in a microscopic image.

[0132] The silicon-containing material is preferably up to 50 m 2 / g, more preferably 30m 2 / g or less, particularly preferred 10m 2 / g. The BET specific surface area is determined according to DIN 66131 (using nitrogen). Therefore, when silicon-containing materials are used as active materials in the anode of lithium-ion batteries, SEI formation can be reduced and the initial coulombic efficiency can be increased.

[0133] The silicon in the silicon-containing material deposited from the silicon precursor may further comprise a dopant selected from the group including, for example, 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, with lithium and / or tin being preferred. The amount of dopant in the silicon-containing material is up to 1 wt. %, more preferably up to 100 ppm, based on the total weight of the silicon-containing material, as determinable by ICP OES.

[0134] Silicon-containing materials generally have surprisingly high stability under compressive and / or shear loads. The pressure stability and shear stability of silicon-containing materials are manifested, for example, by the lack or substantial lack of change in the porous structure of the silicon-containing material in an SEM under compressive loads (e.g., compressing an electrode) and shear loads (e.g., fabricating an electrode), respectively.

[0135] The silicon-containing material may optionally further comprise additional elements, such as carbon. The carbon is preferably present in the form of a thin layer having a thickness of up to 1 μm, preferably less than 100 nm, more preferably less than 5 nm, and very preferably less than 1 nm (determinable by SEM or HR TEM). These carbon layers may be on the inner surface of the pores and / or on the outer surface of the silicon-containing material. The arrangement and number of different layers in the silicon-containing material due to the use of different reactive gases in multiple third stages is also arbitrary. Thus, for example, a layer of a material different from the porous particles, such as carbon, may first be present on the porous particles, and this layer may support the silicon layer or layer of silicon particles. It is also possible to subsequently present a layer of a material different from or the same as the material of the porous particles on the silicon layer or layer of silicon particles, regardless of whether a layer of a material different from the material of the porous particles exists between the porous particles and the silicon layer or layer consisting of silicon particles. The method of the present invention proves particularly advantageous here, since multiple coatings are possible without interruption by opening the fluidized bed reactor.

[0136] The silicon-containing material preferably contains 50% by weight or less of the additional element, more preferably 40% by weight or less, and particularly preferably 20% by weight or less. The silicon-containing material preferably contains 1% by weight or more of the additional element, more preferably 3% by weight or more, and particularly preferably 2% by weight or more. The weight percentage figures are based on the total weight of the silicon-containing material. In another embodiment, the silicon-containing material does not contain the additional element.

[0137] The present invention further provides the use of a silicon-containing material produced by the method of the present invention as an active material in an anode material for an anode of a lithium ion battery, and the use of the anode of the present invention for the manufacture of a lithium ion battery.

[0138] The anode material is preferably based on a mixture comprising a silicon-containing material that can be used by the method of the present invention, one or more binders, optionally graphite as a further active material, optionally one or more further conductive components, and optionally one or more additives.

[0139] The use of additional conductive components in the anode material can reduce the contact resistance within the electrode and between the electrode and the current collector, thereby improving the current carrying capacity of the lithium-ion battery. Examples of preferred additional conductive components are conductive carbon black, carbon nanotubes, or metal particles such as copper.

[0140] The primary particles of the conductive carbon black preferably have a diameter percentile d 10 =5nm~d 90 = 200 nm. The primary particles of conductive carbon black may have chain-like branches and form structures up to μm in size. The carbon nanotubes preferably have diameters of 0.4 to 200 nm, more preferably 2 to 100 nm, and most preferably 5 to 30 nm. The metal particles preferably have a diameter percentile d 10 =5nm~d 90 = 800 nm.

[0141] The anode material preferably comprises 0 to 95 wt %, more preferably 0 to 40 wt %, and most preferably 0 to 25 wt %, of one or more further conductive components, based on the total weight of the anode material.

[0142] In anodes for lithium ion batteries, the silicon-containing material may be present in an amount of preferably 5 to 100 wt %, more preferably 30 to 100 wt %, and most preferably 60 to 100 wt %, based on the total active material present in the anode material.

[0143] Preferred binders are polyacrylic acid or its alkali metal salts, particularly lithium or sodium salts, polyvinyl alcohol, cellulose or cellulose derivatives, polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, polyimides, particularly polyamideimides, or thermoplastic elastomers, particularly ethylene-propylene-diene terpolymers. Particularly preferred are polyacrylic acid, polymethacrylic acid, or cellulose derivatives, particularly carboxymethylcellulose. Particularly preferred are alkali metal salts of the binders, particularly lithium or sodium salts. Most preferred are alkali metal salts of polyacrylic acid or polymethacrylic acid, particularly lithium or sodium salts. All, or preferably some, of the acid groups of the binder can be present in the form of a salt. The binder preferably has a molar mass of 100,000 to 1,000,000 g / mol. A mixture of two or more binders can also be used.

[0144] Generally, natural or synthetic graphite can be used as the graphite. The graphite particles preferably have a diameter percentile d 10 >0.2μm~d 90 <200 μm.

[0145] Examples of additives are pore formers, dispersants, flow control agents or dopants, one example being elemental lithium.

[0146] A preferred formulation for the anode material preferably comprises 5 to 95 wt %, more particularly 60 to 90 wt %, of a silicon-containing material, 0 to 90 wt %, more particularly 0 to 40 wt %, of a further conductive component, 0 to 90 wt %, more particularly 5 to 40 wt %, of graphite, 0 to 25 wt %, more particularly 5 to 20 wt %, of a binder, and 0 to 80 wt %, more particularly 0.1 to 5 wt %, of an additive, the figures expressed in wt % being based on the total weight of the anode material and the fractions of all components of the anode material adding up to 100 wt %.

[0147] The components of the anode material that make up the anode ink or anode paste can be processed in a solvent preferably selected from the group including, for example, water, hexane, toluene, tetrahydrofuran, N-methylpyrrolidone, N-ethylpyrrolidone, acetone, ethyl acetate, dimethyl sulfoxide, dimethylacetamide, and ethanol, and mixtures of these solvents, preferably using a rotor-stator machine, a high-energy mill, a planetary kneader, an agitator ball mill, a shaker table, or an ultrasonic device.

[0148] The anode ink or anode paste preferably has a pH of 2 to 7.5 (as determined, for example, at 20° C. using a WTW pH 340i pH meter with a SenTix RJD probe).

[0149] The anode ink or anode paste can be applied, for example, to a copper foil or another current collector by a doctor blade. Other coating methods, such as spin coating, roller coating, dipping or slot die coating, painting, or spraying, can also be used in accordance with the present invention.

[0150] Before being coated with the anode material of the present invention, the copper foil is preferably treated with a commercially available primer, for example, based on a polymer resin or silane, which can improve adhesion to the copper but generally has no substantial electrochemical activity itself.

[0151] The anode material is generally dried to a constant weight. The drying temperature depends on the components and solvent used. The drying temperature is preferably between 20 and 300°C, more preferably between 50 and 150°C.

[0152] The layer thickness, meaning the dry layer thickness of the anode coating, is preferably 2 to 500 μm, more preferably 10 to 300 μm.

[0153] Finally, the electrode coating is preferably calendered to set a defined porosity. The electrode thus produced preferably has a porosity of 15 to 85%, which can be determined by mercury porosimetry in accordance with DIN ISO 15901-1. Preferably, 25 to 85% of the pore volume, which can be determined in this way, is provided by pores with diameters of 0.01 to 2 μm.

[0154] The present invention further provides a lithium-ion battery comprising a cathode, an anode, two conductive connections to these electrodes, a separator, and an electrolyte impregnating the separator and the two electrodes, as well as a casing containing the elements described, characterized in that the anode comprises a silicon-containing material obtainable by the method of the present invention.

[0155] In the context of the present invention, the term lithium-ion battery also encompasses cells. A cell generally comprises a cathode, an anode, a separator, and an electrolyte. In addition to one or more cells, a lithium-ion battery preferably further comprises a battery management system. A battery management system generally serves to control the battery by means of electronic circuits, for example, to recognize the state of charge, to protect against depletion discharge, or to protect against overcharging.

[0156] Preferred cathode materials that can be used in the present invention include lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide (doped or undoped), lithium manganese oxide (spinel), lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium vanadium phosphate, or lithium vanadium oxide.

[0157] The separator is generally an electrically insulating, ion-permeable membrane, preferably made of polyolefin, such as polyethylene (PE) or polypropylene (PP), or polyester, or a corresponding laminate. Alternatively, as is customary in battery manufacturing, the separator may consist of or be coated with glass or ceramic materials. The separator conventionally separates the first electrode from the second electrode, thus preventing a conductive connection (short circuit) between the electrodes.

[0158] The electrolyte is preferably a solution containing one or more lithium salts (=conductive salts) in an aprotic solvent. The conductive salt is preferably selected from the group consisting of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium imide, lithium methide, lithium trifluoromethanesulfonate LiCF3SO3, lithium bis(trifluoromethanesulfonimide), and lithium borate. The concentration of the conductive salt is preferably between 0.5 mol / L and the solubility limit of the salt in question, based on the solvent. The concentration of the conductive salt is more preferably between 0.8 and 1.2 mol / L.

[0159] The solvent used according to the present invention may preferably be a cyclic carbonate, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethoxyethane, diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, gamma-butyrolactone, dioxolane, acetonitrile, organic esters of carbonic acid, or nitriles, which may be used individually or as mixtures thereof.

[0160] The electrolyte preferably contains a film-forming agent, such as vinylene carbonate or fluoroethylene carbonate. In this way, it is possible to achieve a significant improvement in the cycling stability of anodes containing silicon-containing active materials obtained by the method of the present invention. This improvement is primarily due to the formation of a solid electrolyte interphase interface on the surface of the active particles. The proportion of the film-forming agent in the electrolyte is preferably between 0.1 and 20.0 wt.%, more preferably between 0.2 and 15.0 wt.%, and most preferably between 0.5 and 10 wt.%.

[0161] To best match the actual capacities of the electrodes in a lithium-ion cell, it is advantageous to balance the amounts of material in the positive and negative electrodes. Of particular importance in this context is the fact that during the first or initial charge / discharge cycles (known as activation) of a secondary lithium-ion cell, a coating layer forms on the surface of the electrochemically active material in the anode. This coating layer, called the solid electrolyte interphase interface (SEI), generally consists primarily of electrolyte decomposition products and a certain amount of lithium, and is therefore no longer available for further charge / discharge reactions. The thickness and composition of the SEI depend on the anode material and the nature and quality of the electrolyte solution used. In the case of graphite, the SEI is particularly thin. On graphite, there is typically a 5-35% loss of mobile lithium ions during the first charging step, with a corresponding decrease in the reversible capacity of the battery.

[0162] For anodes having silicon-containing materials obtained by the method of the present invention, the first charging step is accompanied by a loss of mobile lithium ions of preferably at most 30%, more preferably at most 20%, and most preferably at most 10%, which is well below the values described in the prior art, e.g., U.S. Pat. No. 10,147,950 B1.

[0163] The lithium ion batteries of the present invention can be manufactured in any conventional form, such as, for example, wound, folded, or stacked.

[0164] As noted above, all of the substances and materials utilized for the fabrication of the lithium-ion batteries of the present invention are known. The components of the batteries of the present invention are fabricated and assembled to obtain the batteries of the present invention by methods known in the art of battery fabrication.

[0165] The silicon-containing materials obtained by the method of the present invention are notable for their significantly improved electrochemical properties, resulting in lithium-ion batteries with high volumetric capacity and excellent performance characteristics. The silicon-containing materials obtained by the method of the present invention are also permeable to lithium ions and electrons, thus enabling charge transport. The SEI of lithium-ion batteries can be significantly reduced with the silicon-containing materials obtained by the method of the present invention. Furthermore, due to the design of the silicon-containing materials obtained by the method of the present invention, there is no longer any peeling of the SEI from the surface of the active material, or at least there is only significantly reduced peeling. All of this leads to high cycling stability of the components of such lithium-ion batteries whose anodes comprise silicon-containing materials obtained by the method of the present invention. [Brief explanation of the drawings]

[0166] [Figure 1] 1 shows an SEM cross section through the particle for a representative sample of Example 1. [Figure 2] 1 shows an SEM cross section through the particle for a representative sample of Comparative Example 3. [Example]

[0167] The following examples serve to further elucidate the invention described herein.

[0168] The analytical methods and instruments used for characterization were as follows:

[0169] Scanning electron microscope (SEM / EDX) Microscopic analysis was performed with a Zeiss Ultra 55 scanning electron microscope and an Oxford X-Max 80N energy dispersive X-ray spectrometer. Prior to analysis, the samples were subjected to carbon deposition in a Safematic Compact Coating Unit 010 / HV to prevent charging phenomena. Cross sections of the silicon-containing materials shown in the figures were prepared using a Leica TIC 3X ion cutter at 6 kV.

[0170] Inorganic analysis / elemental analysis The C content reported in the examples was confirmed using a Leco CS 230 analyzer, and a Leco TCH-600 analyzer was used for the determination of O and, where appropriate, N and H content. Qualitative and quantitative determination of other reported elements in the resulting silicon-containing materials was performed using ICP (inductively coupled plasma) optical emission spectroscopy (Perkin Elmer Optima 7300 DV). For this analysis, samples were subjected to acid digestion (HF / HNO3) in a microwave (Anton Paar Microwave 3000). ICP-OES determinations are guided by ISO 11885 "Water quality - Determination of selected elements by inductively coupled plasma optical emission spectrometry (ICP-OES) (ISO 11885:2007), German equivalent EN ISO 11885:2009", which is used for the analysis of acidic aqueous solutions (e.g., drinking water, acidified samples of wastewater and other waters, aqua regia extracts of soils and sediments).

[0171] Particle size determination In the context of the present invention, particle size distribution was determined by static laser scattering using a Horiba LA 950 in accordance with ISO 13320. When preparing the samples, particular attention must be paid to the dispersion of particles in the measurement solution, so as not to measure the size of weak agglomerates rather than individual particles. For the porous starting materials and silicon-containing materials considered here, the particles were dispersed in ethanol. For this purpose, prior to measurement, the dispersion was treated with 250W ultrasound for 4 minutes in a Hielscher model UIS250v ultrasonic laboratory instrument with an LS24d5 sonotrode, if necessary.

[0172] BET specific surface area measurement The specific surface area of the materials was measured by gas adsorption with nitrogen by the BET method (determination according to DIN ISO 9277:2003-05 with nitrogen) using a Sorptomatic 199090 instrument (Porotec) or a SA-9603MP instrument (Horiba).

[0173] skeletal density The skeletal density, i.e. the density of the porous solid based on the volume of the externally gas-accessible pore space only, was determined by He pycnometry according to DIN 66137-2.

[0174] Gas accessible pore volume The Gurwitsch gas-accessible pore volume was determined by gas sorption measurements with nitrogen according to DIN 66134.

[0175] Determination of liquidity index The fluidization index is the ratio of the measured pressure drop to the theoretically possible maximum pressure drop. To determine the fluidization index, the pressure drop across the fluidized bed must be measured. The pressure drop is measured by measuring the pressure difference between the top and bottom of the fluidized bed. The pressure difference meter converts the pressure detected by the membrane into a digital value and displays the pressure difference. The pressure measurement conduit should be designed so that it is positioned immediately above the gas-permeable base and immediately above the fluidized bed. Determining the fluidization index also requires an accurate determination of the weight of the introduced particle bed. See also [VDI-Waermeatlas 11th Edition, Section L3.2 Stroemungsformen and Druckverlust in Wirbelschichten, pp. 1371-1382, Springer Verlag, Berlin Heidelberg, 2013].

[0176] Determining the minimum fluidization velocity The minimum fluidization velocity is the fluidization velocity based on the apparent cross-sectional reactor area at which the particle bed changes from a fixed bed through which gas flows to a fluidized bed. The minimum fluidization velocity can be ascertained by simultaneous measurement of the fluidization gas flow rate with a calibrated mass flow meter and the pressure drop with a digital means measuring the pressure difference across the fluidized bed. With knowledge of the cross-sectional area of the reactor, the measured fluidization gas flow rate can be used to calculate the fluidization gas velocity. The progression of the recorded pressure drop versus the fluidization gas velocity is called the fluidized bed characteristic. It is important to note that the fluidized bed characteristic progresses from a high fluidization gas velocity with a gradual decrease in velocity. For pure fixed-bed flow, the pressure drop increases linearly. The corresponding fluidization index FI is less than 1. For a fully formed fluidized bed, the measured pressure drop is constant. The corresponding fluidization index FI is equal to 1. The transition between these two regions represents a state of minimum fluidization. The corresponding fluidization gas velocity based on the apparent cross-sectional reactor area is equal to the minimum fluidization velocity. If the transition from a fixed bed to a fluidized bed is characterized by a region, the intersection of the extrapolated fixed bed characteristics and the extrapolated fluidized bed characteristics is defined as the point of minimum fluidization. [See also VDI-Waermeatlas 11th Edition, Section L3.2 Stroemungsformen and Druckverlust in Wirbelschichten, pp. 1371-1382, Springer Verlag, Berlin Heidelberg, 2013].

[0177] Heat Transfer Measurement To determine the heat transfer between any surface and the fluidized bed, a heat flow probe is used. This probe is referred to as the heat flow rate defined by resistive heating.

[0178]

number

[0179]

number

[0180] Determination of weak aggregate size Samples are taken from the fluidized bed reactor to determine the size of the porous particles and agglomerates formed during the fluidization of Geldart C grade silicon-containing material. Sampling is performed by turning off the fluidization gas and opening the reactor. It should be ensured that the sampling does not change the size of the agglomerates. To determine the agglomerate size, the agglomerates are examined under a high-resolution optical digital microscope. The reported results may represent the size range of the agglomerates.

[0181] The fluidized-bed reactor used in the experimental performance consisted of a cylindrical section with an outer diameter of 160 mm and a height of 1200 mm. The cylindrical section consisted of a chamber with a bottom and the actual fluidized-bed reactor. The two sections were separated from each other by a gas-permeable base. Above the cylindrical reactor section was a connecting reactor section, whose cross-sectional area was twice that of the cylindrical reactor section. The upper end of the reactor had a lid equipped with a filter element for the gas outlet and connections for the introduction of a temperature sensor and a heat flow probe. The reaction temperature was controlled by heating the reactor wall; the height of the heating zone was 80% of the length of the cylinder, starting from the gas-permeable base. Heating was performed electrically. The fluidizing gas was preheated with a gas heater according to the process step prior to its introduction into the fluidized-bed reactor. Pulsation of the fluidizing gas flow was achieved by using a directly controlled magnetic valve. The heat flow probe was installed 7 cm above the gas-permeable base. The reaction temperature was confirmed by multiple temperature sensors in the fluidized bed, distributed axially at a fixed distance from the reactor wall.

[0182] In preliminary experiments, pressure drop measurements across the fluidized bed and heat transfer analysis using a heat flow probe for different gas compositions and temperatures confirmed the minimum flow velocity and maximum heat transfer coefficient for the porous particles and fluidizing gas used in the following examples.

[0183] [Example 1] Production of silicon-containing materials in a fluidized bed reactor using a pulsed fluidizing gas flow.

[0184] In the first step of the method, porous particles (specific surface area = 1907 m 2 / g, pore volume = 0.96 cm 3 / g, volume-weighted median particle size D 50 1000 g of amorphous carbon in the form of (diameter = 2.95 μm, particle density = 0.7 g / cm 3 , Geldart Class C particles) were introduced into the reactor.

[0185] In the second stage, the particle bed was fluidized with a fluidization gas consisting of nitrogen, the gas volume fixed so that the minimum fluidization velocity was at least three times the minimum fluidization velocity confirmed in the preliminary experiment. At the same time, a magnetic valve was used to induce an oscillation of the gas flow at a frequency of 3 Hz between the open and closed positions of the valve. Pressure drop measurements and heat transfer measurements were performed with a fluidization index FI = 0.99 and a heat transfer coefficient α / α based on the maximum heat transfer coefficient determined using the optimum fluidization at the same temperature and the same gas composition. max = 0.98. Once a stable fluidized bed was formed, the fluidizing gas was stopped and the reactor was opened to take samples to measure the size of the agglomerates at different points within the bed of particles in the fluidized bed reactor. The agglomerate size was 237 ± 50 μm. The reactor was then closed again and fluidization was resumed. Once a stable fluidized bed was formed again (FI = 0.99, α / α max = 0.99), the temperature inside the reactor was raised to a temperature between 400 and 450°C. During the temperature increase, the fluidization index FI was 0.99, and the relative heat transfer coefficient α / α max was 0.98. Due to the temperature increase, the fluidization gas flow rate had to be adjusted for this purpose.

[0186] When the reaction temperature reached 400-450 °C, in the third stage of the process, the fluidizing gas consisting of pure nitrogen was replaced with a fluidizing gas consisting of 5 vol.% monosilane SiH4 as silicon precursor in nitrogen. The gas flow pulsation with a frequency between the open and closed positions of the valve of 3 Hz remained constant during and after the exchange of the fluidizing gas, with a fluidization index FI = 0.98 and a relative heat transfer coefficient α / α max= 0.98 was still confirmed. Because the density of the porous particles changes during silicon deposition, the gas velocity of the fluidizing gas was adjusted so that the values of the fluidization index and the relative heat transfer coefficient were always greater than 0.95.

[0187] After 220 minutes of reaction time, in the fourth stage, the fluidization gas was switched to a pulsed nitrogen stream, again with a fluidization index FI=0.99 and a relative heat transfer coefficient α / α max A value of 0.99 was obtained. The heating power was reduced. Once a temperature of 50°C was reached, the fluidization gas flow was switched to a fluidization gas consisting of 5% by volume of oxygen in nitrogen and maintained for 60 minutes to allow for controlled reaction of any reactive groups present on the surface of the resulting product. The reactor was then cooled to room temperature.

[0188] After opening the reactor, samples were taken from the bed at different points in the fifth step. These samples were used to determine the size of the agglomerates, where it was possible to ascertain an average agglomerate size of 289±70 μm.

[0189] After sampling, 2248 g of black solid material was discharged from the reactor. The resulting silicon-containing material was introduced into a cylindrical container and homogenized in a drum hoop mixer. The weak agglomerates formed by the fluidized bed process could be easily removed by sieving. Samples were taken from the homogenized and sieved product for physicochemical analysis, electrochemical analysis, and electron microscopy studies.

[0190] The analytical data of the obtained solid material are listed in Table 1.

[0191] For electron microscopy studies, the product particles were singulated and embedded in epoxy resin. To assess the silicon distribution within the particles, the embedded particles were sectioned.

[0192] Figure 1 shows an SEM cross section through the particle for a representative sample, where it can be seen that the silicon-infiltrated porous particle (A) appears lighter in color than the porous particle itself (B). The vast majority of the product particles have a light hue, thus demonstrating that a homogeneous and uniform silicon deposition has occurred within the pores.

[0193] [Example 2] Production of silicon-containing materials with carbon coatings in a fluidized bed reactor using a pulsed fluidizing gas flow

[0194] The procedure involved the same porous particles (specific surface area = 1907 m) used in Example 1. 2 / g, pore volume = 0.96 cm 3 / g, volume-weighted median particle size D 50 =2.95μm, particle density=0.7g / cm 3 , Geldart C class particles) was used. 1000 g of the same amount was also introduced into the reactor.

[0195] The performance of the second and third stages was similar to that of Example 1, using the same fluidization gas flow and pulsation frequency. After silicon deposition in the third stage was completed, the fourth stage was omitted, and in the second stage, the fluidization gas was switched to a pure pulsed nitrogen stream. The reactor temperature was then set to 700-750°C. The fluidization gas flow had to be readjusted due to the temperature increase.

[0196] Once the reaction temperature reached 700-750 °C, the third stage of the process was carried out again, this time replacing the fluidizing gas consisting of pure nitrogen with a fluidizing gas consisting of 5 vol% ethyne C2H2 as the carbon precursor in nitrogen. A gas flow pulsation with a frequency between the open and closed valve positions of 3 Hz was maintained during and after the fluidizing gas change, resulting in a fluidization index FI = 0.99 and a relative heat transfer coefficient α / α max = 0.98. The carbon coating resulted in only a slight increase in weight and no adjustment of the fluidization gas flow was required.

[0197] After 80 minutes of reaction time, the fourth stage was carried out, where the fluidization gas was switched to a pulsed nitrogen stream. The gas flow was adjusted during cooling, resulting in a fluidization index FI=0.98 and a relative heat transfer coefficient α / α max A value of =0.97 was again obtained. The heating was switched off and the reactor was allowed to cool to room temperature.

[0198] After opening the reactor, samples were taken from the bed at different points in the reactor in the fifth step. These samples were used to measure the size of the agglomerates. Here, by comparison with Example 1, coarse agglomerates with an average diameter of 358±90 μm were found.

[0199] After sampling, 2360 g of black solid was discharged from the reactor. The resulting silicon-containing material was introduced into a cylindrical container and homogenized in a drum hoop mixer. The weak agglomerates formed by the fluidized bed process could be easily removed by sieving. Samples were taken from the homogenized and sieved product for physicochemical and electrochemical analyses. The analytical data of the resulting solid are shown in Table 1.

[0200] Comparative Example 3 Production of silicon-containing materials in a fluidized bed reactor without fluidizing gas pulsations.

[0201] Comparative Example 3 was carried out in the same manner as Example 1. The same porous particles (specific surface area = 1907 m) as used in Examples 1 and 2 were used. 2 / g, pore volume = 0.96 cm 3 / g, volume-weighted median particle size D 50 =2.95μm, particle density=0.7g / cm 3 , Geldart Class C particles) was used. The same amount, 1000 g, was again introduced into the reactor in the first stage.

[0202] In the second stage, the exact same fluidization gas flow as in Example 1 was established, but without pulsation of the fluidization gas flow. The homogeneity of the fluidized bed was determined by the fluidization index FI = 0.78 and the heat transfer coefficient α / α based on the maximum heat transfer coefficient determined for the optimal fluidization with pulsation at the same temperature and gas composition. max= 0.63. From these values it could be inferred that the particle bed was not fully fluidized. Nor was it possible to determine this from the agglomerate diameters observed here. In the upper region of the bed, it was possible to measure an agglomerate diameter of 650 ± 300 μm. In the lower region of the bed, the gas-permeable base removed agglomerates with a size of 3000 ± 1000 μm. This wide range of agglomerates in size combined with partial fluidization is typical of the formation of ABF fluidized beds.

[0203] In the third stage of the process, similar to Example 1, once the reaction temperature of 400-450 °C was reached, the fluidizing gas consisting of pure nitrogen was replaced with a fluidizing gas consisting of 5 vol% monosilane SiH4 as the silicon precursor in nitrogen. The fluidization index and relative heat transfer coefficient were calculated as FI = 0.75 and α / α max = 0.58. Similar to the second stage, these values suggested a heterogeneous fluidized bed during the deposition process. As the density of the porous particles changed during silicon deposition, the gas velocity of the fluidizing gas changed similarly to the gas amount set in Example 1.

[0204] As in Example 1, after 220 minutes of reaction time in the fourth stage, the fluidizing gas was switched to a nitrogen stream. The fluidization index and heat transfer coefficient were FI=0.76 and α / α max = 0.62 was confirmed. The heating power was reduced. Once a temperature of 50 °C was reached, the fluidization gas flow was switched to a fluidization gas consisting of 5% by volume of oxygen in nitrogen and maintained for 60 minutes to allow for controlled reaction of any reactive groups present on the surface of the resulting product. The reactor was then cooled to room temperature.

[0205] After opening the reactor, samples were taken from the bed at different points in the reactor in the fifth step. Here, agglomerates of 700 ± 300 μm in size were measured in the upper region of the bed. Agglomerates of 3500 ± 1000 μm in size were found just above the gas-permeable base.

[0206] After sampling, 2150 g of black solid was discharged from the reactor. The resulting silicon-containing material was introduced into a cylindrical container and homogenized in a drum hoop mixer. The weak agglomerates formed by the fluidized bed process could be easily removed by sieving. Samples of the homogenized and sieved product were taken for physicochemical analysis, electrochemical analysis, and electron microscopy studies. The analytical data of the resulting solid are listed in Table 1.

[0207] For electron microscopy studies, product particles were separated and embedded in epoxy resin. To assess the silicon distribution within the particles, the embedded particles were sectioned. Figure 2 shows an SEM cross section through the particle for a representative sample. It can be seen that the silicon-infiltrated porous particle (A) has a thinner appearance than the porous particle itself (B). Apart from pulsation, significant heterogeneity in silicon distribution is evident, even under identical process conditions. From this, it can be concluded that a homogeneous product can only be produced by the method of the present invention as defined in claim 1.

[0208] Compared to Example 1, where the homogeneity of the fluidized bed may be increased even without pulsation, increasing the fluidizing gas flow rate did not result in a value of the relative heat transfer coefficient comparable to that of Inventive Example 1. Also, higher fluidizing gas flow rates are expected to result in increased particle emissions. Another drawback is the reduced contact time between the solid surface and the gas with the elevated fluidizing gas flow, which leads to lower conversion of the reactive components used in the fluidizing gas flow.

[0209] [Table 1]

[0210] Comparative Example 4 Production of silicon-containing materials in a tubular reactor

[0211] The tubular reactor contained 3.0 g of the same porous carbon (specific surface area = 1907 m) as in Examples 1 to 3 in a quartz glass boat.2 / g, pore volume = 0.96 cm 3 / g, volume-weighted median particle size D 50 =2.95μm, particle density=0.7g / cm 3 The reactor was filled with 10% SiH4 in N2 (10 L (STP) / hr). After inerting with nitrogen, the reactor was heated to 410°C. Once the reaction temperature was reached, reaction gas (10% SiH4 in N2, 10 L (STP) / hr) was passed through the reactor for 5.2 hours. The reactor was then purged with inert gas, and the product was heat-treated at 500°C for 1 hour. Before being removed from the reactor, the product was cooled to room temperature under inert gas. The analytical data of the resulting solid are listed in Table 1.

[0212] [Example 5] Anodes Comprising Silicon-Containing Materials and Electrochemical Testing in Lithium-Ion Batteries of the Present Invention

[0213] 29.71 g of polyacrylic acid (dried to constant weight at 85°C, Sigma-Aldrich, Mw approx. 450,000 g / mol) and 756.60 g of deionized water were stirred on a shaker (290 1 / min) for 2.5 hours until dissolution of the polyacrylic acid was complete. Lithium hydroxide monohydrate (Sigma-Aldrich) was added to the solution in portions until the pH reached 7.0 (measured using a WTW pH 340i pH meter with a SenTix RJD probe). The solution was then mixed on a shaker for an additional 4 hours. 3.87 g of the neutralized polyacrylic acid solution and 0.96 g of graphite (Imerys, KS6L C) were introduced into a 50 ml container and mixed at 2000 rpm in a planetary mixer (SpeedMixer, DAC 150 SP). Next, 3.35 g of the silicon-containing material from Example 1 was added and stirred at 2000 rpm for 1 minute. Next, 1.21 g of an 8% dispersion of conductive carbon black and 0.8 g of deionized water were added and introduced into a planetary mixer at 2000 rpm. Dispersion was then carried out in a dissolver at 3000 rpm for 30 minutes at a constant temperature of 20° C. The ink was again degassed in the planetary mixer under reduced pressure at 2500 rpm for 5 minutes.

[0214] The completed dispersion was then applied to a copper foil (Schlenk Metallfolien, SE-Cu58) with a thickness of 0.03 mm by means of a film applicator frame (Erichsen, Model 360) with a gap height of 0.1 mm. The anode coating thus produced was subsequently dried at 50°C for 60 minutes under an air pressure of 1 bar. The average basis weight of the dried anode coating was 3.0 mg / cm. 2 The coating density is 0.7g / cm 3 It was.

[0215] Electrochemical studies were carried out on a two-electrode button cell (CR2032 type, Hohsen Corp.). The electrode coating was used as the counter or negative electrode (Dm = 15 mm). It was based on lithium nickel manganese cobalt oxide 6:2:2, with a content of 94.0% and an average basis weight of 15.9 mg / cm. 2 A coating (obtained from the company SEI) was used as the working 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 constructed in a glove box (<1 ppm H2O, O2), and the moisture content of the dry mass of all components used was less than 20 ppm.

[0216] Electrochemical testing was performed at 20 °C. The cells were charged by the cc / cv (constant current / constant voltage) method at a constant current of 5 mA / g (equivalent to C / 25) in the first cycle and 60 mA / g (equivalent to C / 2) in subsequent cycles. After reaching a voltage limit of 4.2 V, the cells were charged at a constant voltage until the current fell below 1.2 mA / g (equivalent to C / 100) or 15 mA / g (equivalent to C / 8). The cells were discharged by the cc (constant current) method at a constant current of 5 mA / g (equivalent to C / 25) in the first cycle and 60 mA / g (equivalent to C / 2) in subsequent cycles until a voltage limit of 2.5 V was reached. The selected specific current was based on the weight of the coating on the positive electrode. The electrodes were selected to establish a cathode-to-anode capacity ratio of 1:1.2.

[0217] From Example 5, the following test results were obtained for a full lithium ion battery. - Reversible specific capacity of negative electrode in the second cycle: 1280mAh / g (4.2~2.5V) - Cycle count with 80% or more capacity retention: 350 charge / discharge cycles

[0218] [Example 6] Anodes with silicon-containing materials from Example 2 and electrochemical testing in lithium-ion batteries of the present invention

[0219] The silicon-containing material from Example 2 obtained by the method of the present invention was used to fabricate an anode as described in Example 5. The anode was incorporated into a lithium-ion battery and subjected to testing according to the same procedures as described in Example 5.

[0220] From Example 6, the following test results were obtained for a full lithium ion battery. - Reversible specific capacity of negative electrode in the second cycle: 1210mAh / g (4.2~2.5V) - Cycle count with 80% or more capacity retention: 410 charge / discharge cycles

[0221] Comparative Example 7 Anodes with silicon-containing materials from Comparative Example 3 and electrochemical testing in lithium-ion batteries

[0222] The silicon-containing material obtained from Comparative Example 3, which was not obtained by the method of the present invention, was used to prepare an anode as described in Example 5. The anode was assembled into a lithium-ion battery and subjected to testing according to the same procedures as described in Example 5.

[0223] From Comparative Example 7, the following test results were obtained for the full lithium ion battery. - Reversible specific capacity of negative electrode in the second cycle: 1150mAh / g (4.2~2.5V) - Cycle count with 80% or more capacity retention: 208 charge / discharge cycles

[0224] [Comparative Example 8] Anodes with silicon-containing materials from Comparative Example 4 and electrochemical testing in lithium-ion batteries

[0225] The silicon-containing material obtained from Comparative Example 4, which was not obtained by the method of the present invention, was used to prepare an anode as described in Example 5. The anode was incorporated into a lithium-ion battery and subjected to testing according to the same procedures as described in Example 5.

[0226] From Comparative Example 8, the following test results were obtained for a full lithium ion battery. - Reversible specific capacity of negative electrode in the second cycle: 1240mAh / g (4.2~2.5V) - Cycle count with 80% or more capacity retention: 282 charge / discharge cycles

[0227] [Table 2]

Claims

1. 1. A method for producing silicon-containing materials in a fluidized bed reactor by depositing silicon from at least one silicon precursor within the pores and on the surface of Geldart C porous particles, wherein a fluidizing gas stream in the fluidized bed reactor is induced to oscillate in a fully or partially pulsed manner, propagating in the form of waves and acting on the fluidized bed as pulsed gas streams to form a homogeneous fluidized bed characterized by a fluidization index FI of at least 0.95, the pulsations having a frequency in the range of 0.1 to 20 Hz and a pulse duty ratio in the range of 0.1 to 0.9, the fluidizing gas stream having an apparent velocity that exceeds the minimum measured fluidization velocity of the pulsed gas stream, and the pulsations combined with mechanical agitation as a further fluidization aid.

2. 2. The method of claim 1, comprising at least the following steps: Step 1: Packing porous particles into a fluidized bed reactor; A second step: fluidizing the porous particles with at least one internal gas as a fluidizing gas and adjusting the temperature of the fluidized bed reactor to a temperature for conversion in a third step; Third step: fluidizing with at least one internal gas as a fluidizing gas with the addition of a reaction gas containing one or more silicon precursors to convert the silicon precursors and deposit silicon in the pores and on the surface of the porous particles; Fourth step: cooling the fluidized bed reactor and fluidizing it with at least one inert gas as the fluidizing gas; Step 5: Removing the reaction product from the fluidized bed reactor.

3. The fluidized bed of the fluidized bed reactor has a maximum heat transfer coefficient α between any surface of the components in the fluidized bed and the fluidized bed itself during the second to fourth stages. ｍａｘ The heat transfer coefficient α between any surface of the component in the fluidized bed and the fluidized bed itself is α / α ｍａｘ 3. The method of claim 2, characterized by being ≧0.

95.

4. 4. The method according to claim 2 or 3, characterized in that the temperature of the third stage is in the range of 100 to 1000°C.

5. 5. The method of claim 2, wherein the fluidizing gas comprises an inert component selected from the group consisting of hydrogen, helium, nitrogen, neon, argon, krypton, xenon, and carbon dioxide in an amount of at least 50% of the total pressure of the fluidizing gas, based on the partial pressure of the inert component.

6. 6. The method according to claim 2, wherein the third stage is carried out with a fluidizing gas stream having an apparent velocity above the minimum measured fluidizing velocity of the pulsed gas stream.

7. 7. The process according to claim 2, wherein during the second to fourth stages, the ratio of the pulsed fluidizing gas flow to the total fluidizing gas flow in the fluidized bed reactor is in the range of 0.1 to 1.

8. 8. The method according to claim 2, wherein in the third stage, a portion of the particles forming the fluidized bed is discharged and replaced by porous particles.

9. 9. The method according to any one of claims 2 to 8, characterized in that the sequence of the second, third and optionally fourth steps is repeated at least once, optionally omitting the fourth step in one or more cases.

10. 10. The method of claim 9, wherein a fluidizing gas comprising at least one hydrocarbon and no silicon precursor is used in at least one repetition of the third stage.

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