Method for producing silicon-containing composite particles

Abstract

In a first aspect, the present invention provides a method of making silicon-containing composite particles, the method comprising the steps of: (a) providing a plurality of porous particles comprising micropores and / or mesopores, wherein: (i) the porous particles have a D 50 particle size in the range of 0.5 to 200 µm; (ii) the total pore volume of the micropores and mesopores, as measured by gas adsorption, is in the range of 0.4 to 2.2 cm 3 / g; (iii) the PD 50 pore diameter, as measured by gas adsorption, is no more than 30 nm; (b) combining a charge of the porous particles with a charge of a silicon-containing precursor in a batch pressure reactor, wherein the charge of the porous particles has a volume of at least 20 cm 3 / liter of reactor volume (cm 3 / L RV ), preferably at least 200 cm 3 / liter of reactor volume (cm 3 / L RV ), and wherein the charge of the silicon-containing precursor comprises at least 2 g of silicon per liter of reactor volume (g / L RV ); and (c) heating the reactor to a temperature effective to cause deposition of silicon in the pores of the porous particles, thereby providing silicon-containing composite particles.

Description

[0001] This application is a divisional application of the patent application filed on October 22, 2021, with application number 202180072042.4 and entitled "Method for Preparing Silicon-Containing Composite Particles".

[0002] This invention generally relates to a method for preparing silicon-containing composite particles by depositing silicon in the pores of porous particles. Silicon-containing composite particles are generally suitable for use as anode active materials in rechargeable metal-ion batteries.

[0003] Rechargeable metal-ion batteries are widely used in portable electronic devices, such as mobile phones and laptops, and are increasingly being used in electric or hybrid vehicles. Rechargeable metal-ion batteries typically include an anode in the form of a metal current collector, which is provided with a layer of electroactive material, defined herein as a material capable of inserting and releasing metal ions during battery charging and discharging. The terms “cathode” and “anode” are used herein in the context of placing the battery across a load such that the anode is the negative electrode. When a metal-ion battery is charged, metal ions are transported from the metal-ion-containing cathode layer to the anode via the electrolyte and inserted into the anode material. The term “battery” herein refers both to a device containing a single anode and a single cathode and to a device containing multiple anodes and / or multiple cathodes.

[0004] There is interest in improving the gravimetric and / or volumetric capacity of rechargeable metal-ion batteries. To date, commercial lithium-ion batteries have been primarily limited to using graphite as the anode active material. When the graphite anode is charged, lithium is intercalated between the graphite layers to form lithium with the empirical formula Lia. x Materials with a C6 content (where x is greater than 0 and less than or equal to 1) are used. Therefore, graphite has a maximum theoretical capacity of 372 mAh / g in lithium-ion batteries, with a slightly lower actual capacity (approximately 340 to 360 mAh / g). Other materials such as silicon, tin, and germanium can intercalate lithium at significantly higher capacities than graphite, but they have not yet found widespread commercial applications due to the difficulty in maintaining sufficient capacity over multiple charge / discharge cycles.

[0005] Silicon is considered a promising alternative for manufacturing rechargeable metal-ion batteries with high gravimetric and volumetric capacity due to its very high capacity for lithium (see, for example, Insertion ElectrodeMaterials for Rechargeable Lithium Batteries, Winter, M). et al (in Adv. Mater. 1998, 10, No. 10). At room temperature, silicon has a theoretical maximum specific capacity of approximately 3600 mAh / g in lithium-ion batteries (based on Li). 15(Si4). However, when silicon is lithiated to its maximum capacity, lithium insertion into the bulk silicon results in a significant increase in silicon material volume, up to 400% of its original volume. Repeated charge-discharge cycles induce significant mechanical stress in the silicon material, leading to fracture and delamination of the silicon anode material. The volumetric shrinkage of silicon particles during delithiation causes loss of electrical contact between the anode material and the current collector. Another challenge is that the solid electrolyte interface (SEI) layer formed on the silicon surface lacks sufficient mechanical tolerance to accommodate the expansion and contraction of silicon. As a result, the newly exposed silicon surface leads to further electrolyte decomposition and an increase in SEI layer thickness, as well as irreversible lithium consumption. These failure mechanisms collectively result in unacceptable losses of electrochemical capacity during continuous charge and discharge cycles.

[0006] Numerous methods have been proposed to overcome the problems associated with the volume changes observed during charging of silicon-containing anodes. Fine silicon structures with cross-sections below approximately 150 nm, such as silicon films and silicon nanoparticles, have been reported to be more tolerant of volume changes during charging and discharging compared to silicon particles in the micrometer size range. However, these are not suitable for commercial-scale applications in their unmodified forms; nanoscale particles are difficult to fabricate and process, and silicon films do not provide sufficient volumetric capacity.

[0007] WO 2007 / 083155 discloses that improved capacity retention can be achieved using silicon particles with a high aspect ratio (i.e., the ratio of the maximum to the minimum particle size). The small cross-section of such particles reduces structural stress on the material due to volume changes during charge and discharge. However, these particles can be difficult to manufacture, expensive, and potentially brittle. Furthermore, the high surface area can lead to excessive SEI formation, resulting in excessive capacity loss during the first charge-discharge cycle.

[0008] Generally, it is also known that electroactive materials (such as silicon) can be deposited within the pores of porous support materials (such as activated carbon). These composites provide some of the beneficial charge-discharge properties of nanoscale silicon particles while avoiding the handling difficulties of nanoparticles. Guo et al. (Journal of Materials Chemistry A, 2013, pp.14075-14079) disclosed a silicon-carbon composite material in which a porous carbon substrate provides a conductive framework, wherein silicon nanoparticles are deposited in a uniform distribution within the pore structure of the substrate. The results showed that the composite material exhibited improved capacity retention over multiple charge cycles; however, the initial capacity (in mAh / g) of the composite material was significantly lower than that of silicon nanoparticles.

[0009] The inventors previously reported the development of a class of electroactive materials with composite structures in which nanoscale electroactive materials (such as silicon) are deposited into a pore network of highly porous conductive particulate materials (e.g., porous carbon materials).

[0010] For example, WO 2020 / 095067 and WO 2020 / 128495 report that the improved electrochemical performance of these materials can be attributed to the way in which the electroactive material is located in the form of small domains with a size of about a few nanometers or smaller within the porous material. These fine electroactive structures are considered to have lower resistance to elastic deformation and higher resistance to fracture compared to larger electroactive structures, thus enabling lithiation and delithiation without excessive structural stress. As a result, the electroactive material exhibits good reversible capacity retention over multiple charge-discharge cycles. Secondly, by controlling the silicon loading within the porous carbon framework, the uncharged silicon occupies only a portion of the pore volume, and the unoccupied pore volume of the porous carbon framework can accommodate a large amount of silicon expansion internally. Furthermore, by positioning the nanoscale silicon domains within small mesopores and / or micropores as described above, only a small area of ​​silicon surface is readily accessible to the electrolyte, thus limiting the formation of the SEI. This essentially prevents additional silicon exposure during subsequent charge-discharge cycles, making SEI formation not a significant failure mechanism leading to capacity loss. This contrasts sharply with the characterization of, for example, the excessive SEI formation of materials disclosed by Guo (see above).

[0011] The materials described in WO 2020 / 095067 and WO 2020 / 128495 have been synthesized by chemical vapor infiltration (CVI) in various reactor systems (static, rotary, and FBR). Porous conductive particles were contacted with a silicon-containing precursor (CVI) stream (typically silane gas) in the form of a mixture with an inert gas at atmospheric pressure and temperatures between 400 and 700 °C. All these reactor configurations operated in a batch mode for the solid carbon scaffold and a continuous mode for the silicon precursor gas. Silanes react rapidly at these temperatures; however, silane molecules need to traverse the porous system of the solid particles via a tortuous path. This means that relatively high temperatures are required to achieve uniform infiltration in such reactor systems to prevent mass transfer from becoming a rate-limiting step. The overall result is the formation of composite products with a relatively high average surface area and a relatively low hydride-terminated silicon content. Both of these factors are considered to contribute to reduced electrochemical performance.

[0012] Another drawback of using a continuous flow of silicon-containing precursor gas is the requirement for good mixing of the solids within the gas; otherwise, product batches may include compositional inhomogeneities. Without effective mixing, solids with longer contact times with the gas will contain more silicon than those with shorter contact times with the unreacted silane gas stream; the deposition on the powder bed will be unequal.

[0013] Simply lowering the temperature of the CVI process does not overcome the aforementioned drawbacks. If the temperature is too low, mass transfer becomes the rate-limiting step, resulting in poor penetration of the porous carbon framework, uneven silicon distribution, and the formation of coarse silicon domains.

[0014] US 10,147,950 B2 describes the deposition of silicon from monosilane SiH4 into porous carbon via CVD (chemical vapor deposition) in a tube furnace or similar furnace type, preferably with stirred particles, at temperatures ranging from 300 to 900 °C. This method uses a mixture of 2 mol% silane and nitrogen as an inert gas. Such conditions require very long reaction times. US 10,147,950 B2 mentions various temperature and pressure ranges.

[0015] WO 2012 / 097969 A1 describes the deposition of ultrafine silicon particles in the range of 1 to 20 nm on a porous carbon support by heating silane, which serves as a silicon precursor, at 200 to 950 °C. The silane is diluted with an inert gas to prevent the deposited silicon particles from agglomerating and / or forming thick layers. The deposition is carried out at a pressure range of 0.1 to 5 bar.

[0016] Motevalian et al, Ind. Eng. Chem. Res. 2017, 56, 14995 describes the deposition of silicon layers under high pressure, although not in the presence of a porous matrix. Again, the silicon precursor used (silane SiH4 in this case) is present only at a low concentration of at most 5 mol% of the total gas volume.

[0017] The methods described above typically require long reaction times to obtain a high silicon content in the silicon-containing composite particles. Another drawback of these methods is that only a small fraction of the supplied reactive gas reacts, so the gas leaving the reactor must undergo expensive and inconvenient recycling or disposal operations, which further increases costs, especially when using silicon precursors subject to stringent technical safety requirements.

[0018] Therefore, there is a need in the art for a method for preparing silicon-containing composite particles that reduces or even overcomes at least one of the aforementioned disadvantages, preferably the disadvantages discussed regarding high-temperature and low-temperature CVI processes or long reaction times. Methods starting from porous particles and silicon precursors are preferably technically easy to implement. Silicon-containing composite particles preferably have a high storage capacity for lithium ions, and when used as an active material in the anode of a lithium-ion battery, preferably achieve high cycle stability.

[0019] In a first aspect, the present invention provides a method for preparing silicon-containing composite particles, the method comprising the following steps: (a) Provides a variety of porous particles including micropores and / or mesopores, wherein: (i) D of porous particles50 The particle size ranges from 0.5 to 200 µm; (ii) The total pore volume of micropores and mesopores, measured by gas adsorption, ranged from 0.4 to 2.2 cm³. 3 Within the range of / g; (iii) PD measured by gas adsorption 50 Aperture not exceeding 30 nm; (b) Combining a porous particle charge with a silicon-containing precursor charge in an intermittent pressure reactor, wherein the porous particle charge has a diameter of at least 20 cm. 3 / L reactor volume (cm²) 3 / L RV (, preferably at least 200 cm) 3 / L reactor volume (cm²) 3 / L RV The volume of the silicon-containing precursor charge includes at least 2 g silicon per liter of reactor volume (g / L). RV );and (c) The reactor is heated to a temperature that effectively induces silicon deposition in the pores of the porous particles, thereby providing silicon-containing composite particles.

[0020] In a preferred embodiment of the present method according to the first aspect of the invention, the above steps a) to c), particularly steps b) to c), are divided into process stages 1 to 7: Phase 1: Packing an intermittent pressure reactor with one or more porous particles. Phase 2: Packing a batch pressure reactor with one or more silicon-containing precursors. Stage 3: The batch pressure reactor is heated to the target temperature, at which one or more silicon-containing precursors begin to decompose in the batch pressure reactor. Stage 4: Decomposition of the silicon-containing precursor, wherein silicon is deposited in the pores of the porous particles and optionally on the surface of the porous particles, thereby providing silicon-containing composite particles. Phase 5: Cooling the intermittent pressure reactor. Stage 6: The gaseous reaction products formed during the deposition process are removed from the intermittent pressure reactor. Stage 7: Remove silicon-containing composite particles from the intermittent pressure reactor. The feature is that, during stage 4, the pressure in the intermittent pressure reactor is increased to at least 7 bar.

[0021] A more preferred method is to prepare silicon-containing composite particles by thermally decomposing one or more silicon-containing precursors in the presence of one or more porous particles, wherein silicon is deposited in the pores of the porous particles and optionally deposited on the surface of the porous particles, the method comprising at least stages 1 to 7: Phase 1: Packing an intermittent pressure reactor with one or more porous particles. The porous particles in the filling have a diameter of at least 20 cm. 3 / L reactor volume (cm²) 3 / L RV (, preferably at least 200 cm) 3 / L reactor volume (cm²) 3 / L RV The volume of ) and The porous particles include micropores and / or mesopores, wherein: (i) D of porous particles 50 The particle size ranges from 0.5 to 200 µm; (ii) The total pore volume of micropores and mesopores, measured by gas adsorption, ranged from 0.4 to 2.2 cm³. 3 Within the range of / g; (iii) PD measured by gas adsorption 50 Aperture not exceeding 30 nm; Phase 2: Packing a batch pressure reactor with one or more silicon-containing precursors. The silicon-containing precursor charge includes at least 2 g silicon per liter of reactor volume (g / L) RV ), Stage 3: The batch pressure reactor is heated to the target temperature, at which one or more silicon-containing precursors begin to decompose in the batch pressure reactor. Stage 4: Decomposition of the silicon-containing precursor, wherein silicon is deposited in the pores of the porous particles and optionally on the surface of the porous particles, thereby providing silicon-containing composite particles. Phase 5: Cooling the intermittent pressure reactor. Stage 6: The gaseous reaction products formed during the deposition process are removed from the intermittent pressure reactor. Stage 7: Remove silicon-containing composite particles from the intermittent pressure reactor. During phase 4, the pressure in the intermittent pressure reactor is increased to at least 7 bar.

[0022] In another aspect, the present invention provides a method for preparing silicon-containing composite particles by thermally decomposing one or more silicon-containing precursors in the presence of one or more porous particles, wherein silicon is deposited in the pores of the porous particles, preferably in the pores and on the surface of the porous particles, the method comprising at least stages 1 to 7: Phase 1: Packing an intermittent pressure reactor with one or more porous particles. Phase 2: Packing a batch pressure reactor with one or more silicon-containing precursors. Stage 3: The batch pressure reactor is heated to the target temperature, at which one or more silicon-containing precursors begin to decompose in the batch pressure reactor. Stage 4: Decomposition of the silicon-containing precursor, wherein silicon is deposited in the pores of the porous particles, preferably in the pores and on the surface of the porous particles. Phase 5: Cooling the intermittent pressure reactor. Stage 6: The gaseous reaction products formed during the deposition process are removed from the intermittent pressure reactor. Stage 7: Remove silicon-containing composite particles from the intermittent pressure reactor. The method is characterized in that, during stage 4, the pressure in the intermittent pressure reactor is increased to at least 7 bar.

[0023] A more preferred method is to prepare silicon-containing composite particles by thermally decomposing one or more silicon-containing precursors in the presence of one or more porous particles, wherein silicon is deposited in the pores of the porous particles, preferably in the pores and on the surface of the porous particles, the method comprising at least stages 1 to 7: Phase 1: Packing an intermittent pressure reactor with one or more porous particles. The porous particles in the filling have a diameter of at least 20 cm. 3 / L reactor volume (cm²) 3 / L RV (, preferably at least 200 cm) 3 / L reactor volume (cm²) 3 / L RV The volume of ) and The porous particles include micropores and / or mesopores, wherein: (i) D of porous particles 50 The particle size ranges from 0.5 to 200 µm; (ii) The total pore volume of micropores and mesopores, measured by gas adsorption, ranged from 0.4 to 2.2 cm³. 3 Within the range of / g; (iii) PD measured by gas adsorption 50 Aperture not exceeding 30 nm; Phase 2: The batch pressure reactor is filled with one or more silicon-containing precursors. The silicon-containing precursor charge includes at least 2 g silicon per liter of reactor volume (g / L) RV ), Stage 3: The batch pressure reactor is heated to a target temperature, at which one or more silicon-containing precursors begin to decompose in the batch pressure reactor. Stage 4: Decomposition of the silicon-containing precursor, wherein silicon is deposited in the pores of the porous particles, preferably in the pores and on the surface of the porous particles. Phase 5: Cooling the intermittent pressure reactor. Stage 6: The gaseous reaction products formed during the deposition process are removed from the intermittent pressure reactor. Stage 7: Remove silicon-containing composite particles from the intermittent pressure reactor. The method is characterized in that, during stage 4, the pressure in the intermittent pressure reactor is increased to at least 7 bar.

[0024] For clarification only, the preferred and alternative embodiments described below refer to each of the above aspects of the present invention and each of the above preferred methods of the present invention.

[0025] Therefore, this invention generally relates to a method for preparing composite particulate materials, wherein nanoscale silicon domains are deposited into a pore network of porous particles. Thus, the porous particles form a framework comprising nanoscale silicon domains. As used herein, the term "nanoscale silicon domain" refers to a nanoscale silicon body having dimensions imposed by the position of silicon within the micropores and / or mesopores of the porous particles.

[0026] The method of this invention differs from previous methods in that silicon deposition is carried out in batches for porous particles and silicon-containing precursors. Furthermore, the corresponding charge of porous particles and silicon-containing precursors per liter of reactor volume means that silicon deposition is carried out under autogenous pressure higher than atmospheric pressure, and can be at least one or even two orders of magnitude higher than atmospheric pressure.

[0027] This method is associated with many advantages, particularly due to the loading of silicon-containing precursors into a batch pressure reactor and the parameters according to the invention. The advantageous effects can be further enhanced synergistically through preferred pressure measures.

[0028] First, the silicon-containing precursor can be distributed throughout the entire volume of the reactor. Therefore, the reaction can proceed to the same level of conversion at any point in the reactor, especially as long as there is no temperature distribution. This avoids product composition inhomogeneity caused by solid-gas contact, and the materials can have identical properties regardless of their position in the reactor. The batch composition is preferably homogeneous.

[0029] Secondly, the silicon-containing precursor can be distributed throughout the porous system of porous particles before the reaction occurs. Therefore, since the silicon-containing precursor is already present in the pores at the start of the reaction, mass transfer confinement can be reduced. Furthermore, batch reactors can be loaded with large quantities of porous particles to reduce or even eliminate headspace in the reactor, ensuring that any silicon-containing precursor molecules in the remaining reactor volume outside the pore volume of the porous particles (e.g., in the interstitial spaces) have only a short mean free path to the nearest particle.

[0030] Third, the higher the pressure, the higher the amount of silane that can be fed into the reactor in a single batch. Silanes are supercritical above 47.8 atmospheres, and due to the compressibility under these conditions, a high loading of silicon can be introduced into a single batch at ambient temperature.

[0031] Surprisingly, current batch methods are able to prepare silicon-containing composite particles in a shorter reaction time and therefore more efficiently. The method of the present invention surprisingly achieves an increased amount of silicon-containing precursor (particularly within porous particles) decomposition and thus a correspondingly increased amount of silicon deposited within the porous particles. Furthermore, the silicon deposition is particularly uniform. This can be further improved by the preferred pressure of the present invention. This is particularly surprising given that, as is known from methods of producing polycrystalline silicon, silicon deposition at relatively high pressures is accompanied by an increase in dust and undesirable formation (JO Odden et al., Solar Energy Mat. & Solar Cells 2005, 86, 165) (which is detrimental to silicon deposition on the inner surfaces of the pores and the outer surfaces of the porous particles, as well as to the yield of the composite particles). The method of the present invention surprisingly overcomes this detrimental effect. These effects are particularly pronounced at instantaneous pressures, especially at at least 7 bar.

[0032] Fourth, the temperature is typically raised to the deposition temperature only after the reactor is packed with silicon-containing precursors under pressure. This also introduces new methods for controlling the reaction rate and product composition. Higher hydride deposition can be carried out at lower temperatures because the system does not have to deal with mass transfer limitations. Therefore, compared to atmospheric pressure synthesis routes, product composite particles with lower surface areas and higher hydride-terminated silicon can be obtained.

[0033] Current methods for producing silicon-containing composite particles offer several advantages over existing technologies. One particular advantage is the possibility of complete conversion of the silicon precursor within a short reaction time. These advantages are preferably further enhanced by the pressure increase in the batch pressure reactor during step (c) or stage 4, which is not, or is not solely, caused by a temperature increase.

[0034] Another advantage is the reduced amount of inert gas or the possibility of completely eliminating inert gas, which also leads to higher space / time yields, thus enabling faster and more uniform deposition of silicon in or on porous particles.

[0035] In addition, it can prevent the continuous recirculation or treatment of reactor exhaust gas, as is often the case in the operation of open reactors.

[0036] In addition, implementation in a batch pressure reactor makes it very easy to deposit the same reactive components (such as silicon-containing precursors) multiple times in precisely adjustable amounts of deposited products (based on the reactants in the corresponding deposition steps).

[0037] Therefore, silicon-containing composite particles obtained by the method of the present invention are preferably distinguished by the favorable uniformity of the deposited layer.

[0038] Furthermore, a particular advantage is the avoidance of dust generation, which is often described. This can be achieved, for example, through the large surface area of ​​porous particles (which can be used to deposit silicon from silicon-containing precursors), or through the strong penetration of porous particles into the silicon-containing precursor. Simultaneously, high yields of deposited silicon are obtained in this manner.

[0039] Furthermore, the current approach, which starts with porous particles and silicon precursors, is technically easy to implement.

[0040] Due to the advantages of the method of the present invention, silicon-containing composite particles are advantageously readily available quickly and economically, and are particularly useful as active materials for lithium-ion battery anodes with excellent performance.

[0041] Surprisingly, the silicon-containing composite particles prepared according to the current method exhibit high lithium-ion storage capacity and achieve surprisingly high cycle stability when used as an active material in the anode of a lithium-ion battery. The current silicon-containing composite material advantageously demonstrates low volume change during cycling.

[0042] Silicon-containing composite particles can be obtained by the method of the present invention, and they possess improved properties for use in lithium-ion batteries with high volumetric energy capacity. The silicon-containing material obtained by the method of the present invention is permeable to lithium ions and electrons, thus allowing charge transport. Furthermore, this method can reduce the amount of electrolyte solvent and the formation of a solid electrolyte interface (“SEI”). Excessive SEI is known to negatively impact the cycle efficiency of lithium-ion batteries.

[0043] To avoid ambiguity, the term "particle size" as used herein refers to the equivalent sphere diameter (esd), which is the diameter of a sphere having the same volume as a given particle, where particle volume should be understood to include the volume of any pores within the particle. The term "D" as used herein... 50 "and "D 50"Particle size" refers to the volume-based median particle size, that is, the diameter of the particle population to which it is found in 50% by volume. As used in this paper, the term "D"... 10 "and "D 10 "Particle size" refers to the 10th percentile volume median particle size, that is, the diameter of the particle population found in the 10th percentile volume. The term "D" is used as in this paper. 90 "and "D 90 "Particle size" refers to the 90th percentile volume median particle size, that is, the diameter below the 90th percentile of the particle population in which it is found.

[0044] Particle size and particle size distribution can be determined using conventional laser diffraction techniques according to ISO 13320:2009. Laser diffraction relies on the principle that particles scatter light at an angle that varies depending on the particle size, and a set of particles will produce a scattered light pattern defined by the intensity and angle that can be correlated with the particle size distribution. A variety of commercially available laser diffraction instruments are available for rapid and reliable determination of the distribution. Unless otherwise stated, particle size distribution measurements indicated or reported herein are as performed by means of measurements from Malvern Instruments. TM Regular Malvern Mastersizer TM Measurements taken with a 3000 particle size analyzer. Malvern Mastersizer TM The 3000 particle size analyzer operates by projecting a helium-neon gas laser beam through a transparent cell containing particles of interest suspended in an aqueous solution. Light striking the particles is scattered by an angle inversely proportional to the particle size, and a photodetector array measures the light intensity at multiple predetermined angles. The particle size distribution is determined by computer processing of the intensities measured at different angles using standard theoretical principles. The laser diffraction values ​​reported in this paper are obtained using a wet dispersion of particles in 2-propanol with the addition of 5 vol% surfactant SPAN. TM The results were obtained at -40°C (sorbitan monopalmitate). The refractive index of the porous particles was 2.68, that of the composite particles was 3.50, and the dispersant index was 1.378. The particle size distribution was calculated using the Mie scattering model.

[0045] Alternatively, particle size and particle size distribution can be determined according to ISO 13320 using a Mie model and a Horiba LA 950 measuring instrument with static laser scattering, preferably with ethanol as the dispersion medium for the particles.

[0046] Typically, porous particles have a density (D) in the range of 0.5 to 200 µm. 50 Particle size. Optionally, the D of porous particles... 50The particle size can be at least 1 µm, or at least 1.5 µm, or at least 2 µm, or at least 3 µm, or at least 4 µm, or at least 5 µm. Optionally, the D of the porous particles... 50 The particle size may not exceed 150 µm, or 100 µm, or 70 µm, or 50 µm, or 40 µm, or 30 µm, or 25 µm, or 20 µm, or 18 µm, or 15 µm, or 12 µm or 10 µm.

[0047] For example, porous particles may have a D in the range of 0.5 to 150 µm, or 0.5 to 100 µm, or 0.5 to 50 µm, or 0.5 to 30 µm, or 1 to 25 µm, or 1 to 20 µm, or 2 to 25 µm, or 2 to 20 µm, or 2 to 18 µm, or 3 to 20 µm, or 3 to 18 µm, or 3 to 15 µm, or 4 to 18 µm, or 4 to 15 µm, or 4 to 12 µm, or 5 to 15 µm, or 5 to 12 µm, or 5 to 10 µm. 50 Particle size. Particles within these size ranges and having the porosity and pore size distribution described herein are ideally suited for preparing composite particles for metal-ion battery anodes via the CVI process.

[0048] D of porous particles 10 The particle size is preferably at least 0.2 µm, or at least 0.5 µm, or at least 0.8 µm, or at least 1 µm, or at least 1.5 µm, or at least 2 µm. By using D... 10 Maintaining a particle size of 0.2 µm or larger reduces the likelihood of undesirable agglomeration of submicron-sized particles and improves the dispersibility of the resulting composite particles. 10 The particle size is preferably ≤10 µm, more preferably ≤5 µm, and most preferably ≤3 µm.

[0049] Optionally, the D of porous particles 90 The particle size is preferably no more than 300 µm, or no more than 250 µm, or no more than 200 µm, or no more than 150 µm, or no more than 100 µm, or no more than 80 µm, or no more than 60 µm, or no more than 40 µm, or no more than 30 µm, or no more than 25 µm, or no more than 20 µm, more preferably no more than 18 µm, even more preferably no more than 15 µm, and most preferably no more than 13 µm. D 90 The particle size is preferably ≥ 4 µm and more preferably ≥ 8 µm.

[0050] The volume-weighted particle size distribution of porous particles is preferably at the diameter percentile d. 10≥ 0.2 µm and d 90 ≤ 20.0 μm, more preferably in d 10 ≥ 0.4 µm and d 90 ≤ 15.0 µm, most preferably d 10 ≥ 0.6 µm to d 90 ≤ 12.0 µm.

[0051] Porous particles preferably have a narrow size distribution span. For example, the particle size distribution span (defined as (D...) 90 -D 10 ) / D 50 The particle size distribution is preferably 5 or less, more preferably 4 or less, more preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. By maintaining a narrow size distribution span, it is easier to achieve efficient filling of particles into a dense powder layer.

[0052] The volume-weighted particle size distribution of the porous particles has a preferred ≤15.0 μm, a more preferred ≤12.0 μm, a very preferred ≤10.0 μm, a particularly preferred ≤8.0 μm, and a most preferred ≤4.0 μm d 90 and d 10 The difference in value (D) 90 -D 10 (Poor). The volume-weighted particle size distribution of the porous particles has a preferred ≥ 0.6 µm, more preferably ≥ 0.8 µm, and most preferably ≥ 1.0 µm d 90 -d 10 Difference.

[0053] Porous particles are preferably present in the form of separate or aggregated particles. Porous particles are preferably non-aggregate and even more preferably non-agglomerate. Aggregation generally refers to the initial formation and fusion of primary particles during the production process of porous particles, and / or the primary particles being linked together by, for example, covalent bonds, thus forming aggregates. Primary particles are typically separate particles. Aggregates or separate particles can form clusters. Clusters are, for example, aggregates or loosely connected primary particles linked together by van der Waals interactions or hydrogen bonds. Agglomerates can be readily broken down into aggregates using conventional kneading and dispersing techniques. By these techniques, aggregates cannot be decomposed or can only be partially decomposed into primary particles. The presence of porous particles in the form of aggregates, clusters, or separate particles can be seen, for example, by conventional scanning electron microscopy (SEM). In contrast, static light scattering methods used to determine the particle size distribution or particle size of matrix particles cannot distinguish between aggregates and clusters.

[0054] Porous particles can have any desired shape, and therefore can be, for example, flat, irregular, fragmented, spherical or needle-like, with fragmented or spherical particles being preferred.

[0055] Porous particles may have an average sphericity greater than 0.5 (as defined herein). Preferably, they have an average sphericity of at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, or at least 0.8, or at least 0.85. Spherical particles are considered to contribute to uniformity of deposition and to denser packing in batch pressure reactors and to denser packing of the final product when incorporated into electrodes.

[0056] Highly accurate two-dimensional projections of micron-scale particles can be obtained using scanning electron microscopy (SEM) and dynamic image analysis, where a digital camera is used to record the shadows cast by the particles. The term "sphericity," as used herein, should be understood as the ratio of the area of ​​the particle projection (obtained from this imaging technique) to the area of ​​a circle, where the particle projection and the circle have the same circumference. Therefore, for a single particle, the sphericity S can be defined as: Where A m It is the measured area of ​​the particle projection, and C m This is the measured perimeter of the particle projection. For example, the average sphericity S of the particle population used in this paper... av Defined as: Where n represents the number of particles in the population. The average sphericity of the particle population is preferably calculated from the two-dimensional projections of at least 50 particles.

[0057] Porous particles comprise a three-dimensional interconnected network of open pores, which includes micropores and / or mesopores, as well as optional macropores with small volumes. According to standard IUPAC terminology, the term “micropore” is used herein to refer to a pore with a diameter less than 2 nm, the term “mesopore” is used herein to refer to a pore with a diameter between 2 and 50 nm, and the term “macropore” is used herein to refer to a pore with a diameter greater than 50 nm.

[0058] References in this document to the volumes of micropores, mesopores, and macropores in porous particles, as well as any references to the distribution of pore volume within porous particles, relate to the internal pore volume of the porous particles used as starting material in step (a) of the claimed method, prior to the deposition of silicon into the pore volume in step (c).

[0059] Porous particles are characterized by a total volume of micropores and mesopores (i.e., the total pore volume in the range of 0 to 50 nm) ranging from 0.4 to 2.2 cm³. 3 Within the range of / g. Typically, porous particles include micropores and mesopores. However, the use of porous particles that include micropores without mesopores or mesopores without micropores is not excluded.

[0060] More preferably, the total volume of micropores and mesopores in the porous particles is at least 0.45 cm³. 3 / g, or at least 0.5 cm 3 / g, at least 0.55 cm 3 / g, or at least 0.6 cm 3 / g, or at least 0.65 cm 3 / g, or at least 0.7 cm 3 / g, or at least 0.75 cm 3 / g, or at least 0.8 cm 3 / g, at least 0.85 cm 3 / g, or at least 0.9 cm 3 / g, or at least 0.95 cm 3 / g, or at least 1 cm 3 / g. Using high-porosity particles may be advantageous because it allows for the containment of a larger amount of silicon within the pore structure.

[0061] The internal pore volume of the porous particles is suitably limited to a value at which the increased brittleness of the porous particles outweighs the advantage of the increased pore volume for accommodating a larger amount of silicon. Preferably, the total volume of micropores and mesopores in the porous particles does not exceed 2 cm³. 3 / g, or not exceeding 1.8 cm 3 / g, or not exceeding 1.6 cm 3 / g, or not exceeding 1.5 cm 3 / g, or not exceeding 1.45 cm 3 / g, or not exceeding 1.4 cm 3 / g, or not exceeding 1.35 cm 3 / g, or not exceeding 1.3 cm 3 / g, or not exceeding 1.25cm 3 / g, or not exceeding 1.2 cm 3 / g.

[0062] In some instances, the total volume of micropores and mesopores in porous particles can range from 0.45 to 2.2 cm³. 3 / g, or 0.5 to 2 cm 3 / g, or 0.55 to 2 cm 3 / g, or 0.6 to 1.8 cm 3 / g, or 0.65 to 1.8 cm 3 / g, or 0.7 to 1.6 cm 3 / g, or 0.75 to 1.6 cm 3 / g, or 0.8 to 1.5 cm 3 Within the range of / g.

[0063] In other examples, the total volume of micropores and mesopores in porous particles can range from 0.4 to 0.75 cm³. 3 / g, or 0.4 to 0.7 cm 3 / g, or 0.4 to 0.65 cm 3 / g, 0.45 to 0.75 cm 3 / g, or 0.45 to 0.7 cm 3 / g, or 0.45 to 0.65cm 3 / g, or 0.45 to 0.6 cm 3 Within the range of / g.

[0064] In other examples, the total volume of micropores and mesopores in porous particles can range from 0.6 to 2 cm³. 3 / g, or 0.6 to 1.8 cm 3 / g, or 0.7 to 1.8 cm 3 / g, or 0.7 to 1.6 cm 3 / g, or 0.8 to 1.6 cm 3 / g, or 0.8 to 1.5 cm 3 / g, or 0.8 to 1.4 cm 3 / g, or 0.9 to 1.5 cm 3 / g, or 0.9 to 1.4 cm 3 / g, or 1 to 1.4 cm 3 Within the range of / g.

[0065] D of porous particles 50 The pore size is preferably no more than 30 nm, and optionally no more than 25 nm, or no more than 20 nm, or no more than 15 nm, or no more than 12 nm, or no more than 10 nm, or no more than 8 nm, or no more than 6 nm, or no more than 5 nm, or no more than 4 nm, or no more than 3 nm, or no more than 2.5 nm, or no more than 2 nm, or no more than 1.5 nm. As used herein, the term "PD" is preferred. 50 "Aperture" refers to the volume-based median pore size based on the total volume of micropores and mesopores (i.e., the pore size less than 50% of the total volume of micropores and mesopores). Therefore, according to the present invention, at least 50% of the total volume of micropores and mesopores is in the form of pores with a diameter of less than 30 nm.

[0066] To avoid ambiguity, and to determine PD 50 The purpose of this value is to disregard any large pore volume (pore diameter greater than 50 nm).

[0067] The volume ratio of micropores to mesopores in porous particles can be in the range of 100:0 to 0:100. Preferably, the volume ratio of micropores to mesopores is 90:10 to 55:45, or 90:10 to 60:40, or 85:15 to 65:35.

[0068] The pore size distribution of porous particles can be unimodal, bimodal, or multimodal. As used herein, the term "pore size distribution" refers to the distribution of the pore size of porous particles relative to the cumulative total internal pore volume. Bimodal or multimodal pore size distributions may be preferred because the close proximity between micropores and larger diameter pores provides the advantage of efficient ion transport to silicon through the porous network.

[0069] The total volume of micropores and mesopores, as well as the pore size distribution of micropores and mesopores, were determined according to the standard methods described in ISO 15901-2 and ISO 15901-3, at 77 K to 10 -6 Nitrogen adsorption at relative pressures p / p0 is determined using quenched solid density functional theory (QSDFT) or classical adsorption models, such as the Horvath-Kawazoe model according to DIN 66135 for micropores and the BJH model according to DIN 66134 for mesopores. Nitrogen adsorption is a technique for characterizing the porosity and pore size distribution of a material by condensing a gas within the pores of a solid. As pressure increases, the gas first condenses in the pores of smallest diameter, and the pressure increases until a saturation point is reached, at which all pores are filled with liquid. The nitrogen pressure is then gradually decreased to allow the liquid to evaporate from the system. Analysis of the adsorption and desorption isotherms and the hysteresis between them allows for the determination of pore volume and pore size distribution. Suitable instruments for measuring pore volume and pore size distribution by nitrogen adsorption include the TriStar II and TriStar II Plus porosity analyzers (available from Micromeritics Instrument Corporation, USA) and the Autosorb IQ porosity analyzer (available from Quantachrome Instruments).

[0070] Nitrogen adsorption is effective for measuring the pore volume and pore size distribution of pores with a diameter of at most 50 nm, but it is less reliable for pores with much larger diameters. For the purposes of this invention, nitrogen adsorption is therefore used only for pores with a diameter of at most 50 nm and including 50 nm (i.e., only for micropores and mesopores) to determine the pore volume and pore size distribution. Similarly, the PD is determined relative to the total volume of only micropores and mesopores. 50 .

[0071] Due to limitations in available analytical techniques, it is not possible to measure pore volume and pore size distribution across the entire range of micropores, mesopores, and macropores using a single technique. In the case of porous particles including macropores, the volume of pores with diameters ranging from greater than 50 nm to at most 100 nm can be determined by mercury porosimetry, and preferably not exceeding 0.3 cm³. 3 / g, or not exceeding 0.20cm 3 / g, or not exceeding 0.1 cm 3 / g, or not exceeding 0.05 cm 3 / g. A small portion of the macropores can be used to facilitate the entry of electrolytes into the pore network, but the advantages of this invention are primarily obtained by accommodating silicon in the micropores and smaller mesopores.

[0072] Any pore volume with a pore size of 50 nm or less, as measured by mercury porosimetry (as described above, nitrogen adsorption is used to characterize mesopores and micropores), is not considered. For the purposes of this invention, pore volumes above 100 nm, as measured by mercury porosimetry, are assumed to be interparticle porosity and are also not considered.

[0073] Mercury intrusion porosimetry (MIP) is a technique for characterizing the porosity and pore size distribution of a material sample by applying different levels of pressure to the sample immersed in mercury. The pressure required for mercury to penetrate into the pores of the sample is inversely proportional to the pore size. The values ​​obtained by MIP reported in this paper are based on ASTM UOP578-11, where the surface tension γ is 480 mN / m for mercury at room temperature, and the contact angle is... Take 140°C. At room temperature, the density of mercury is taken as 13.5462 g / cm³. 3 A variety of high-precision mercury porosimetry instruments are commercially available, such as the AutoPore IV series of automated mercury porosimeters, which are available from Micromeritics Instrument Corporation in the United States. For a complete overview of mercury porosimetry, see PA Webb and C. Orr in “Analytical Methods in Fine Particle Technology, 1997, Micromeritics Instrument Corporation, ISBN 0-9656783-0”.

[0074] It should be understood that intrusion techniques such as gas adsorption and mercury porosimetry are only effective for determining the pore volume of pores accessible to nitrogen or mercury from the outside of porous particles. The porosity values ​​specified herein should be understood as referring to the volume of open pores (pores accessible to the outside of porous particles by fluid). When determining porosity values, completely encapsulated pores that cannot be identified by nitrogen adsorption or mercury porosimetry should not be considered herein. Similarly, any pore volume located in pores as small as or below the detection limit of nitrogen adsorption is not considered.

[0075] Porous particles preferably have a density of ≥ 0.2 cm. 3 / g, more preferably ≥ 0.6 cm 3 / g and the optimal value is ≥ 1.0 cm 3 / g of Gurwitsch gas accessible pore volume. This is useful for obtaining lithium-ion batteries with high capacity. The Gurwitsch gas accessible pore volume is determined by gas adsorption measurement using nitrogen, according to DIN 66134.

[0076] Preferred porous particles have a diameter of less than 0.3 cm. 3 / g and more preferably less than 0.15 cm 3 Those pore volumes that are inaccessible to gas ( / g). In this way, the capacity of lithium-ion batteries can also be increased. The inaccessible gas pore volume can be determined by the following formula: The volume of gas-inaccessible pores = 1 / density of pure material - 1 / density of the framework.

[0077] The pure material density here is based on the theoretical density of porous particles of a pure material, which is determined by its phase composition or density (the density of the material as if it did not have closed porosity). Data on pure material density can be found by technicians at, for example, the National Institute of Standards and Technology's Ceramic Data Portal (NIST, https: / / srdata.nist.gov / CeramicDataPortal / scd). For example, the pure material density of carbon is 2.2 to 2.3 g / cm³. 3 The density of pure silicon dioxide is 2.203 g / cm³. 3 The pure boron nitride material has a concentration of 2.25 g / cm³. 3 The pure material concentration of silicon nitride is 3.44 g / cm³. 3 The pure material strength of silicon carbide is 3.21 g / cm³. 3 The skeletal density is the actual density of porous particles (accessible to gas) determined by the helium specific gravity bottle method.

[0078] The porous particles are preferably based on one or more materials selected from hard carbon, soft carbon, amorphous carbon in the form of mesophase carbon microspheres, natural or synthetic graphite, single-walled and multi-walled carbon nanotubes and graphene; oxides, such as silicon dioxide, alumina, mixed silicon-alumina oxides, titanium dioxide, magnesium oxide, lead oxide and zirconium oxide; carbides, such as silicon carbide and boron carbide; nitrides, such as silicon nitride and boron nitride; and other ceramic materials.

[0079] Examples of ceramic materials are described by the following composition formulas: Al a B b C c Mg d N e O f Si g Where 0 ≤ a, b, c, d, e, f, g ≤ 1; and at least two coefficients a to g > 0 and a 3 + b 3 + c 4 +d 2 + g 4 3 e 3 + f 2.

[0080] Ceramic materials can be, for example, binary, ternary, quaternary, pentagonal, hexavalent, or heptagonal compounds. Preferred ceramic materials are those with the following compositional formulas: Non-stoichiometric boron nitride (BN) z Where z = 0.2 to 1, Non-stoichiometric carbon nitride (CN) z Where z = 0.1 to 4 / 3, Boron carbonitride B x CN z , where x = 0.1 to 20 and z = 0.1 to 20, where x 3 + 4 3 z 3, Boron nitride oxide (BN) z O r , where z = 0.1 to 1 and r = 1 to 0.1, where 3 3 r 2 + z 3, Boron carbonitride oxide B x CN z O r , where x = 0.1 to 2, z = 0.1 to 1 and r = 0.1 to 1, where x 3 + 4 3 r 2 + z 3, silicon carbide Si x CO z , where x = 0.1 to 2 and z = 0.1 to 2, where x 4 + 4 3 z 2, Silicon carbonitride (Si) x CN z , where x = 0.1 to 3 and z = 0.1 to 4, where x 4 + 4 3 z 3, boron carbonitride silicon Si w B x CN z Where w = 0.1 to 3, x = 0.1 to 2 and z = 0.1 to 4, where w 4 + x 3 +4 3 z 3, boron carbonitride silicon Si w B x CO z Where w = 0.10 to 3, x = 0.1 to 2 and z = 0.1 to 4, where w 4 + x 3 +4 3 z 2, boron carbonitride silicon oxide Si v B w CN x O z Where v = 0.1 to 3, w = 0.1 to 2, x = 0.1 to 4 and z = 0.1 to 3, where v 4 + w 3 + 4 3 x 3 + z 2, and Silicon boron aluminum oxide carbonitride (Al) u B v Si x CN w O z Where u = 0.1 to 2, v = 0.1 to 2, w = 0.1 to 4, x = 0.1 to 2 and z = 0.1 to 3, where u 3 + v 3 + x 4 + 43 w 3 + z 2.

[0081] An example of porous metal oxide particles is TiO₂. x Titanium oxides, wherein x has a value greater than 1 and less than 2.

[0082] Preferred porous particles are based on carbon, silicon dioxide, titanium dioxide, boron nitride, silicon carbide, and / or silicon nitride. More preferred materials are carbon, boron nitride, and silicon dioxide.

[0083] Porous particles are more preferably porous conductive particles, and most preferably porous carbon particles.

[0084] Porous carbon particles can be based on materials selected from amorphous carbon, natural or synthetic graphite, carbon nanotubes (such as single-walled and multi-walled carbon nanotubes), and graphene. Amorphous carbon can be in the form of hard carbon, soft carbon, or mesophase carbon microspheres. Carbon can be crystalline carbon, amorphous carbon, or a mixture of amorphous and crystalline carbon. Porous carbon particles can be hard carbon particles or soft carbon particles.

[0085] The porous carbon particles preferably contain at least 80% by weight of carbon, more preferably at least 90% by weight of carbon, even more preferably at least 95% by weight of carbon, and optionally at least 98% by weight or at least 99% by weight of carbon.

[0086] As used in this article, the term "hard carbon" typically refers to carbon atoms found primarily in nanoscale polyaromatic domains. 2 A disordered carbon matrix in a hybrid state (triple bond). Polyaromatic domains are cross-linked via chemical bonds such as COC bonds. Due to the chemical cross-linking between polyaromatic domains, hard carbon cannot be converted to graphite at high temperatures. Hard carbon exhibits graphitic properties, as evidenced by the large G band (~1600 cm⁻¹) in Raman spectroscopy. -1 This has been demonstrated. However, the carbon is not typically entirely graphitic, as evidenced by the prominent D band (~1350 cm⁻¹) in the Raman spectrum. -1 As proven by ).

[0087] As used in this article, the term "soft carbon" also generally refers to sp(s) in which carbon atoms are found to be primarily located in polyaromatic domains with a size in the range of 5-200 nm. 2 Disordered carbon matrix in a hybrid state (triple bond). Compared to hard carbon, the polyaromatic domains in soft carbon are typically associated by intermolecular forces rather than cross-linked by chemical bonds. This means they will graphitize at high temperatures. Porous carbon particles preferably contain at least 50% sp(s) as measured by XPS. 2 Hybridized carbon. For example, porous carbon particles can suitably contain 50% to 98% sp. 2 Hybridized carbon, 55% to 95% sp2 Hybridized carbon, 60% to 90% sp 2 Hybridized carbon, or 70% to 85% sp 2 Hybridized carbon.

[0088] A variety of materials can be used to prepare suitable porous carbon frameworks. Examples of usable organic materials include plant biomass, including lignocellulosic materials (such as coconut shells, rice husks, wood, etc.); and fossil carbon sources, such as coal. Examples of resin and polymer materials that form porous carbon particles upon pyrolysis include phenolic resins, phenolic varnish resins, bitumen, melamine, polyacrylates, polystyrene, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers containing monomer units of acrylates, styrene, α-olefins, vinylpyrrolidone, and other olefinically unsaturated monomers. A wide variety of carbon materials are available in the art depending on the starting materials and conditions of the pyrolysis process. Porous carbon particles of various sizes are available from commercial suppliers.

[0089] Porous carbon particles can undergo chemical or gas-based activation processes to increase the volume of mesopores and micropores. Suitable activation methods include, for example, contacting pyrolytic carbon with one or more of oxygen, steam, CO, CO2, or KOH at temperatures ranging from 600 to 1000°C.

[0090] Porous particles are preferably open-celled. Open-celled generally means that pores are connected to the surface of the particle, for example, via channels, and can preferably transfer mass with the surrounding environment, especially gaseous compounds. This can be demonstrated using gas adsorption measurements (according to the assessment of Brunauer, Emmett, and Teller, “BET”), which is a gas adsorption measurement of specific surface area.

[0091] Porous particles preferably have a diameter of at least 50 μm 2 / g, or at least 750 m 2 / g, or at least 1,000 m 2 / g, or at least 1,250 m 2 / g, or at least 1,500 m 2 / g BET surface area. As used herein, the term "BET surface area" should be understood to refer to the surface area per unit mass calculated from the measurement of the physical adsorption of gas molecules on a solid surface according to ISO 9277 using the Brunauer–Emmett–Teller principle. Preferably, the BET surface area of ​​the porous particles does not exceed 4,000 m². 2 / g, or not exceeding 3,500 m 2 / g, or not exceeding 3,250 m 2 / g, or not exceeding 3,000 m 2 / g. For example, porous particles can have a density of 750 m. 2 / g to 4,000 m 2 / g, or 1,000 m 2 / g to 3,500 m 2 / g, or 1,250 m 2 / g to 3,250 m 2 / g, or 1,500 m 2 / g to 3,000 m 2 BET surface area within the range of / g.

[0092] Porous particles preferably have a density of 0.1 to 7 g / cm³. 3 More preferably 0.3 to 3 g / cm 3 The skeleton density was determined by the helium specific gravity bottle method. This is advantageous for increasing the gravimetric capacity (mAh / g) of lithium-ion batteries.

[0093] Porous particles preferably have a concentration of at least 0.35 and more preferably less than 3 g / cm³. 3 More preferably less than 2 g / cm 3 More preferably less than 1.5 g / cm 3 The optimal value is 0.35 to 1.2 g / cm³. 3 The particle density. As used herein, the term “particle density” refers to the “apparent particle density” (i.e., the mass of the particle divided by the particle volume, where the particle volume is the sum of the solid material and any closed or blind pores (“blind pores” are pores that are too small to be measured by mercury porosimetry)) as measured by mercury porosimetry.

[0094] Preferably, the porous particles have a density of at least 0.4 g / cm³. 3 or at least 0.45 g / cm 3 or at least 0.5 g / cm 3 or at least 0.55 g / cm 3 or at least 0.6 g / cm 3 or at least 0.65 g / cm 3 or at least 0.7 g / cm 3 The particle density is measured by mercury intrusion porosimetry. Preferably, the porous particles have a density not exceeding 1.15 g / cm³. 3 or not exceeding 1.1 g / cm 3 or not exceeding 1.05 g / cm 3 or not exceeding 1 g / cm 3 or not exceeding 0.95 g / cm 3 Or not exceeding 0.9 g / cm 3 The particle density was measured by mercury intrusion porosimetry.

[0095] For clarity, it should be noted that porous particles are generally different from silicon-containing composite particles. Porous particles are used as starting materials for the production of silicon-containing composite particles. Silicon is typically absent, and more particularly preferably absent, silicon obtained by depositing silicon precursors, which are located in the pores and on the surface of the porous particles.

[0096] Under standard conditions (100 kPa and 20°C), the silicon-containing precursor is preferably a silicon-containing liquid or gas. Preferably, the silicon-containing precursor is a silicon-containing gas under standard conditions.

[0097] Silicon-containing precursors are typically formed into silicon through heat treatment. Preferred silicon-containing precursors are silane-containing compounds, chlorosilanes, and alkylsilanes.

[0098] Examples of silanes are monosilanes (SiH4), disilanes (Si2H6), trisilanes (Si3H8), and more advanced straight-chain, branched, or cyclic homologues, such as neopentasilanes (Si5H). 12 Cyclohexasilane Si6H 12 Examples of chlorosilanes are trichlorosilane HSiCl3, dichlorosilane H2SiCl2, chlorosilane H3SiCl, tetrachlorosilane SiCl4, hexachlorodisilane Si2Cl6, and higher-order straight-chain, branched, or cyclic homologues such as 1,1,2,2-tetrachlorodisilane Cl2HSi-SiHCl2, chlorinated or partially chlorinated oligosilanes or polysilanes, and methylchlorosilanes such as trichloromethylsilane MeSiCl3, dichlorodimethylsilane Me2SiCl2, trichlorotrimethylsilane Me3SiCl, tetramethylsilane Me4Si, dichloromethylsilane MeHSiCl2, chloromethylsilane MeH2SiCl, and dichlorodimethylsilane Me2HSiCl. Examples of alkylsilanes are methylsilane MeH3Si, dimethylsilane Me2H2Si, and trimethylsilane Me3SiH.

[0099] A more preferred silicon-containing precursor is selected from monosilane SiH4; general formula Si n H n+2 A straight-chain silane, where n can include an integer in the range of 2-10; general formula - [SiH2] n - Cyclic silanes, wherein n can include integers in the range of 3 to 10; trichlorosilane HSiCl3, dichlorosilane H2SiCl2, and chlorosilane H3SiCl. Particularly preferred silicon-containing precursors include silanes (SiH4), disilanes (Si2H6), trisilanes (Si3H8), methylsilanes, dimethylsilanes, and chlorosilanes. Even more preferred silicon-containing precursors are selected from SiH4, HSiCl3, and H2SiCl2. Silane (SiH4) is the most preferred.

[0100] The porous particle packing used in step (b) preferably has a diameter of at least 30 cm.3 / L RV or at least 40 cm 3 / L RV or at least 50 cm 3 / L RV or at least 75 cm 3 / L RV or at least 100 cm 3 / L RV or at least 150 cm 3 / L RV or at least 200 cm 3 / L RV And more preferably at least 250 cm 3 / L RV or at least 300 cm 3 / L RV or at least 400 cm 3 / L RV or at least 500 cm 3 / L RV or at least 600 cm 3 / L RV or at least 700 cm 3 / L RV or at least 800 cm 3 / L RV or at least 900 cm 3 / L RV The volume. Preferably, the porous particles used in step (b) are packed with a volume of at least 500 cm³. 3 / L RV And in some embodiments, it is optionally sufficient to substantially fill the reactor volume of the batch pressure reactor.

[0101] As used herein, the volume of porous particles refers to the equivalent mass of the porous particles as determined by their tap density. For example, a 200 cm³ porous particle with a tap density of 1000 g / L, as defined herein. 3 The volume of the porous granular material is equivalent to 200 g of porous granular material. The tap density is measured according to ISO 3953 using 12,000 taps as the standard.

[0102] The silicon-containing precursor charge used in step (b) contains at least 2 g / L RV Silicon, preferably at least 5 g / L RV Silicon, or at least 10 g / L RV Silicon, or at least 15 g / L RV Silicon, or at least 20 g / L RV Silicon, or at least 40 g / LRV Silicon, or at least 60 g / L RV Silicon, or at least 80 g / L RV Silicon, or at least 100 g / L RV Silicon, or at least 150 g / L RV Silicon, or at least 200 g / L RV Silicon, or at least 250 g / L RV Silicon.

[0103] Preferably, the silicon-containing precursor used in step (b) is gaseous. The partial pressure of the silicon-containing precursor in the batch pressure reactor after step (b) is preferably at least 200 kPa, or at least 300 kPa, or at least 500 kPa, or more preferably at least 700 kPa, or at least 1,000 kPa, or at least 1,500 kPa, or at least 2,000 kPa, or at least 2,500 kPa, or at least 3,000 kPa, or at least 4,000 kPa, or at least 5,000 kPa.

[0104] Once porous particles and silicon-containing precursors are added, the batch pressure reactor is preferably substantially oxygen-free. For example, following a standard procedure for a reaction carried out in an oxygen-free atmosphere, oxygen can be sufficiently removed from the reactor by emptying the reactor volume and rinsing it with an inert gas or a silicon-containing precursor gas.

[0105] In addition to silicon-containing precursors, batch pressure reactors may also contain inert packing gases; such as rare gases like helium, neon, argon, krypton, xenon, or nitrogen, carbon dioxide, or synthesis gases. Preferred inert gases include argon, and especially nitrogen.

[0106] The feed of the intermittent pressure reactor may also include hydrogen, especially when the silicon precursor is a chlorosilane, preferably with an atomic ratio of hydrogen to chlorine of at least 1:1.

[0107] The batch pressure reactor may be additionally charged with one or more dopants. The dopants are based on compounds containing, for example, boron, nitrogen, phosphorus, arsenic, germanium, iron, or nickel. Preferred dopants are ammonia (NH3), diborane (B2H6), phosphine (PH3), germanane (GeH4), arsine (AsH3), and nickel tetracarbonyl (Ni(CO)4). The dopants may be added to the batch pressure reactor, for example, in step (b) or in stage 1 or stage 2 of the current method.

[0108] The intermittent pressure reactor may be additionally charged with one or more hydrocarbons selected from the following: aliphatic hydrocarbons having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, such as methane, ethane, propane, butane, pentane, isobutane, hexane, cyclopropane, cyclobutane, cyclopentane, cyclohexane, and cycloheptane; unsaturated hydrocarbons having 1 to 10 carbon atoms, such as ethylene, acetylene, propylene or butene, isoprene, butadiene, divinylbenzene, vinylacetylene, cyclohexadiene, and cyclooctadiene; cyclic unsaturated hydrocarbons such as cyclopropylene, cyclobutene, cyclopentene, cyclohexene, cyclohexadiene, cyclopentadiene, dicyclopentadiene, or norbornene; and aromatic hydrocarbons such as benzene, toluene, p-xylene, m-xylene or o-xylene, styrene (vinylbenzene), ethylbenzene, and diphenylmethylbenzene. Alkanes or naphthalenes, other aromatic hydrocarbons such as phenol, o-cresol, m-cresol, p-cresol, umbelliferene, nitrobenzene, chlorobenzene, pyridine, anthracene, or phenanthrene; myrcene, geraniol, thioterpineol, norbornene, borneol, isoborneol, camphor, limonene, terpinene, pinene, pinane, carene, phenol, aniline, anisole, furan, furfural, furfuryl alcohol, hydroxymethylfurfural, dihydroxymethylfuran, and mixed fractions containing a variety of such compounds, such as those from natural gas condensate, crude oil distillate, or coke oven condensate, mixed fractions from product streams of fluid catalytic cracking (FCC), steam cracking, or Fischer-Tropsch synthesis units, or, very generally, hydrocarbon-containing material streams from the processing of wood, natural gas, crude oil, and coal. Hydrocarbons may be added to the batch pressure reactor, for example, in step (b) or in stage 1 or stage 2 of the current method.

[0109] After step (b), the contents of the intermittent pressure reactor may preferably consist essentially of porous particles, silicon precursors, and optionally an inert filling gas or hydrogen.

[0110] The mass ratio of porous particles to silicon in the silicon-containing precursor typically defines the silicon content of the composite particle product. Preferably, the mass ratio of porous particles to silicon precursor (based on silicon equivalent) in step (b) is 95:5 to 40:60, yielding composite particles with a theoretical silicon content of 5 to 60% by weight. For example, the mass ratio of porous particles to silicon precursor (based on silicon equivalent) in step (b) can be at least 90:10, at least 85:15, or at least 80:20. Optionally, the mass ratio of porous particles to silicon precursor (based on silicon equivalent) in step (b) can not exceed 50:50, or not exceed 60:40, or not exceed 70:30.

[0111] The temperature in step (c) is preferably in the range of 300 to 800°C, or 300 to 750°C, or 300 to 650°C, or 300 to 600°C, or 320 to 550°C, or 320 to 500°C, or 340 to 450°C, or 350 to 450°C, or 300 to 395°C, or 320 to 380°C. Generally, lower temperatures (e.g., 320 to 500°C, or 340 to 450°C, or 350 to 450°C, or 320 to 380°C) are preferred because the reaction is not limited by mass transfer.

[0112] The pressure in the batch pressure reactor in step (c) is an autogenous pressure and will depend on the type of silicon-containing precursor used, the size of the porous particle charge, and the presence of any inert packing gas. However, in all cases, the pressure in step (c) is above atmospheric pressure, and preferably significantly above atmospheric pressure. For example, the pressure in step (c) can be at least 200 kPa, or at least 300 kPa, or at least 500 kPa, or preferably at least 700 kPa, or at least 1,000 kPa, or at least 1,500 kPa, or at least 2,000 kPa, or at least 2,500 kPa, or at least 3,000 kPa, or at least 4,000 kPa, or at least 5,000 kPa. Step (c) may optionally be performed above the critical pressure of the silicon precursor.

[0113] Depositing silicon from silicon-containing precursors typically results in the elimination of byproduct gases and generally leads to an increase in reactor pressure. For example, depositing silicon from silane gas (SiH4) typically results in the elimination of two moles of hydrogen per mole of silane precursor. Consequently, the partial pressure of the eliminated hydrogen is usually significantly higher than the partial pressure of the unreacted silane. In some cases, such as when the feed of the silicon-containing precursor to the reactor is small compared to the reactor volume, the pressure increase caused by the complete conversion of the silicon-containing precursor may fall within the pressure tolerance of a batch pressure reactor. After the reaction is complete, the byproduct gases can then be simply vented from the reactor.

[0114] In other cases, it may be necessary to control the pressure increase during the reaction, preferably ensuring that the total pressure in the batch pressure reactor does not exceed the maximum design pressure of the batch pressure reactor. Preferably, the pressure reactor includes an integrated hydrogen-selective membrane, preferably used to control the pressure increase during the reaction, and even more preferably to prevent exceeding the maximum design pressure. This allows for the separation of hydrogen byproducts from unreacted silanes (or disilanes, trisilanes, etc.), so that hydrogen can be discharged from the reactor.

[0115] Depending on the amount of silicon to be deposited in step (c), the method of the present invention can be operated as a multi-pass process, wherein successive deposition steps are used to deposit the target amount of silicon. The multi-pass process preferably includes the following additional steps: (d) Discharge byproduct gases from the intermittent pressure reactor; (e) Adding another charge of silicon precursor to the batch pressure reactor, wherein the other charge of silicon precursor gas comprises at least 2 g silicon per liter of reactor volume (g / L) RV );and (f) Heat the reactor to a temperature that effectively induces further deposition of silicon into the pores of the porous particles.

[0116] If necessary, steps (d) through (f) can be repeated multiple times to deposit the target amount of silicon.

[0117] The preferred operating parameters for packing the reactor with the silicon-containing precursor in step (b) and the reaction in step (c) above also apply to the repetition of these steps in steps (e) and (f). Steps (e) and (f) can be carried out under the same conditions as steps (b) and (c) or under different conditions.

[0118] Optionally, at least one step (f) can be performed at a lower temperature and / or lower pressure than step (c). In the case of repeating step (f), each instance of step (f) can be performed at a lower temperature and / or lower pressure than the previous silicon deposition step (i.e., step (c) or the previous step (f)).

[0119] It is believed that higher temperatures and higher pressures favor faster deposition rates and quicker pore coverage, resulting in lower surface areas. However, these conditions can also favor silicon deposition on the outer surfaces of the particles, which is detrimental due to the formation of SEI on exposed silicon. Therefore, the ability to vary the rate and location of silicon deposition is a significant advantage. In step (c), the silicon deposition rate can be high to fill most of the pore structure through multiple loading steps at varying temperatures and / or pressures, followed by one or more subsequent steps (f) at lower pressures and / or temperatures to slow the deposition rate, control the coverage rate, and prevent silicon deposition on the outer surfaces of the particles. Step (d) may optionally include cooling the batch pressure reactor to temperatures below 300°C, i.e., too low for silicon deposition to occur. This allows the reactor to be reequilibrated with a fresh charge containing silicon precursors before being heated back to the reaction temperature. However, if the injection time of the fresh charge containing silicon precursors is short, the cooling step may not be necessary.

[0120] A range of different silicon loadings in the composite particles can be obtained using the method of the present invention. For example, based on the total mass of silicon and the porous particle framework, the amount of silicon in the composite particle product of step (c) or step (f) can suitably range from 5 to 60% by weight. Preferably, the amount of silicon in the composite particle product from step (c) or step (f) is 10 to 60% by weight, or 15 to 60% by weight, or 20 to 60% by weight, or 25 to 60% by weight, or 30 to 60% by weight, or 35 to 60% by weight, or 40 to 60% by weight, or 45 to 55% by weight.

[0121] The amount of silicon in the composite particles can be selected such that after step (c), at least 25% and up to 80% or more of the internal pore volume of the porous particles are occupied by silicon. For example, silicon may account for 25% to 60%, or 25% to 55%, or 30% to 50%, or 53% to 55%, or 40% to 60%, or 25% to 45%, or 25% to 40% of the internal pore volume of the porous particles. Within these preferred ranges, the pore volume of the porous particles effectively accommodates the silicon expansion during charging and discharging, but avoids excessive pore volume that does not contribute to the volumetric capacity of the particulate particles. However, the amount of silicon is not high enough to hinder effective lithiation due to insufficient metal ion diffusion rates or mechanical resistance to lithiation caused by insufficient expansion volume.

[0122] The amount of silicon in porous particles can be determined by the mass ratio of silicon to porous particles within [0.5×P]. 1 The requirement is related to the available orifice volume within the range of 1.9 × P1:1, where P1 is the orifice volume in cm. 3 / g represents a dimensionless quantity representing the total pore volume of micropores and mesopores in porous particles (e.g., if the porous particles have a pore volume of 1.2 cm³). 3 If the total volume of micropores and mesopores is given by / g, then P1 = 1.2). This relationship takes into account the density of silicon and the pore volume of porous particles to define the weight ratio of silicon at which the pore volume accounts for approximately 20% to 82%.

[0123] Preferably, at least 90% by weight of silicon in the composite particles, more preferably at least 95% by weight, and even more preferably at least 98% by weight, is located within the internal pore volume of the porous particles, such that no silicon or negligible silicon is located on the outer surface of the composite particles. The reaction kinetics of the CVI process ensure that preferential silicon deposition occurs on the inner surface of the porous particles.

[0124] The composite particles were further characterized by their performance under thermogravimetric analysis (TGA) in air. This analytical method relies on the principle that a weight increase is observed when silicon is oxidized to silicon dioxide (SiO2) in air at high temperatures. The mechanism of silicon oxidation is temperature-dependent. Silicon atoms at the surface of the silicon nanostructure are oxidized at lower temperatures than silicon atoms in the bulk of the silicon nanostructure (Reference: Bardet et al.). Phys. Chem. Chem. Phys. (2016), 18, 18201).

[0125] As determined by TGA, the composite particles of the present invention preferably have a low content of coarse bulk silicon. Coarse bulk silicon is defined herein as silicon that has undergone oxidation at temperatures above 800°C, as determined by TGA, wherein the TGA is performed in air at a heating rate of 10°C / min. Therefore, the content of coarse bulk silicon is determined according to the following formula: Z = 1.875 × [(M f - M 800 ) / M f ] ×100% Where Z is the percentage of unoxidized silicon at 800℃, and M... 800 It is the mass of the sample at 800℃, M f This is the mass of ash when oxidation is complete at 1400℃. For the purposes of this analysis, it is assumed that any mass increase above 800℃ corresponds to silicon oxidation to SiO2, and the total mass when oxidation is complete is SiO2.

[0126] Silicon oxidized at temperatures above 800°C is not ideal. Preferably, no more than 10% by weight of silicon, or no more than 8% by weight of silicon, or no more than 6% by weight of silicon, or no more than 5% by weight of silicon, or no more than 3% by weight of silicon, or no more than 2% by weight of silicon are coarse bulk silicon as determined by TGA.

[0127] The amount of silicon in the composite particles can be determined by elemental analysis. Preferably, elemental analysis is used to determine the weight percentage of carbon (and optionally hydrogen, nitrogen, and oxygen) in the individual porous carbon particles and the silicon-containing composite particles. Determining the weight percentage of carbon in the individual porous carbon particles takes into account the possibility that the porous carbon particles contain small amounts of heteroatoms. Combining these two measurements allows for a reliable determination of the weight percentage of silicon relative to the porous carbon particles.

[0128] Silicon content is preferably determined by ICP-OES (Inductively Coupled Plasma Emission Spectrometry). Many ICP-OES instruments are commercially available, such as the iCAP® 7000 series ICP-OES analyzers from ThermoFisher Scientific. The carbon content (and hydrogen, nitrogen, and oxygen contents, if desired) of composite particles and individual porous carbon particles is preferably determined by IR absorption. A suitable instrument for determining carbon, hydrogen, nitrogen, and oxygen content is the TruSpec® Micro elemental analyzer from Leco Corporation.

[0129] The composite particles preferably have a low total oxygen content. Oxygen may be present in the composite particles, for example as part of the porous particles or as an oxide layer on any exposed silicon surface. Preferably, the total oxygen content of the composite particles is less than 15% by weight, more preferably less than 10% by weight, even more preferably less than 5% by weight, for example less than 2% by weight, or less than 1% by weight, or less than 0.5% by weight.

[0130] The silicon-containing composite particles preferably have a D-value in the range of 0.5 to 30 µm. 50 Particle size. If the D of the composite particles is at the end of the CVI process... 50 If the particle size is greater than 30 µm, then before using the composite particles to manufacture electrodes, it is preferable, for example, to reduce the size of the composite particles to no more than 30 µm by grinding. 50 Particle size. Having a D particle size not exceeding 30 µm. 50 The composite particles of this size exhibit good dispersibility in slurry, robust structure, high capacity retention during repeated charge-discharge cycles, and are suitable for forming dense electrode layers of uniform thickness in the conventional thickness range of 20 to 50 µm.

[0131] Optionally, the D of silicon-containing composite particles 50 The particle size can be at least 1 µm, or at least 2 µm, or at least 3 µm, or at least 4 µm, or at least 5 µm. Optionally, D 50 The particle size may not exceed 20 µm, or 18 µm, or 16 µm, or 14 µm, or 12 µm, or 10 µm or 8 µm.

[0132] For example, silicon-containing composite particles may have a D in the range of 1 to 20 µm, or 1 to 18 µm, or 1 to 16 µm, or 2 to 16 µm, or 2 to 14 µm, or 2 to 12 µm, or 2 to 10 µm, or 2 to 8 µm. 50 Particle size.

[0133] D containing silicon composite particles 10The particle size is preferably at least 0.5 µm, or at least 0.8 µm, or at least 1 µm. This is achieved by using D... 10 By keeping the particle size at 0.5 µm or larger, the likelihood of undesirable agglomeration of submicron-sized particles is reduced, resulting in improved dispersibility of particulate materials and increased capacity retention.

[0134] D containing silicon composite particles 90 The particle size is no more than 50 µm, or no more than 40 µm, or no more than 30 µm, or no more than 25 µm, or no more than 20 µm, or no more than 15 µm. The presence of very large particles leads to uneven particle formation and accumulation in the electrode active layer, thereby disrupting the formation of a dense electrode layer, especially for electrode layers with a thickness in the range of 20 to 50 µm. Therefore, D is preferred. 90 The particle size is at most 40 µm, and even more preferably lower.

[0135] Silicon-containing composite particles preferably have a narrow size distribution span. For example, the particle size distribution span (defined as (D...) 90 -D 10 ) / D 50 The particle size distribution is preferably 5 or smaller, more preferably 4 or smaller, more preferably 3 or smaller, more preferably 2 or smaller, and most preferably 1.5 or smaller. By maintaining a narrow size distribution span, it is easier to achieve efficient filling of particles into the dense electrode layer.

[0136] Silicon-containing composite particles preferably have a diameter of no more than 300 μm. 2 / g, or not exceeding 250 mg 2 / g, or not exceeding 200 m 2 / g, or not exceeding 150 mg 2 / g, or not exceeding 100 mg 2 / g, or not exceeding 80 m 2 / g, or not exceeding 60 m 2 / g, or not exceeding 40m 2 / g, or not exceeding 30 mg 2 / g, or not exceeding 25 mg 2 / g, or not exceeding 20 mg 2 / g, or not exceeding 15 mg 2 / g, or not exceeding 10m 2 / g, or not exceeding 5 mg 2The BET surface area is approximately 0.1 m² / g. Generally, a low BET surface area is preferred to minimize the formation of a solid electrolyte interphase (SEI) layer at the surface of the composite particles during the first charge-discharge cycle of the anode. However, excessively low BET surface areas result in unacceptably low charge rates and capacities due to the inaccessibility of the electroactive material bulk to metal ions in the surrounding electrolyte. For example, a BET surface area of ​​at least 0.1 m² / g is preferred. 2 / g, or at least 1 m 2 / g, or at least 2 m 2 / g, or at least 5 mg 2 / g. For example, the surface area of ​​BET can be 1 m². 2 / g to 25 m 2 Within the range of / g, more preferably within 2 m 2 / g to 15 m 2 Within the range of / g.

[0137] The silicon-containing composite particles preferably have a specific charge capacity of 1200 to 2340 mAh / g during the first lithiation. Preferably, the silicon-containing composite particles have a specific charge capacity of at least 1400 mAh / g during the first lithiation.

[0138] The reaction process can be carried out using any reactor capable of operating in batch mode and under high pressure. A batch pressure reactor is typically a type of reactor that operates such that the pressure inside the reactor is greater than the surrounding pressure.

[0139] The batch pressure reactor is preferably selected from tubular reactors, fluidized bed reactors, fixed bed reactors, and autoclaves. Fluidized bed reactors and autoclaves are particularly preferred, especially autoclaves.

[0140] Porous particles and the resulting composite particles can exist in the reactor as a static bed of particles or as a moving bed of particles. A static bed of particles is preferred when the volume of the porous particle charge is high relative to the available volume of the batch pressure reactor, for example, at least 80%, at least 90%, or at least 95% of the available volume of the batch pressure reactor (i.e., such that the reactor is substantially filled with porous particles in step (b)). Then, the silicon-containing precursor can be distributed throughout the entire volume of the porous particles before the reaction begins. Therefore, since the silicon-containing precursor is already present in the pores at the start of the reaction, mass transfer limitations are eliminated. As long as there is no temperature distribution in the reactor, the reaction proceeds at the same conversion rate at any location in the reactor.

[0141] Intermittent pressure reactors that can be used in static beds without mixing can have any desired geometry. Preferred reactor structures are cylindrical, conical, spherical, and polyhedral forms, or combinations thereof.

[0142] The preferred reactor for static bed reactions is a shell-and-tube furnace reactor. This type of reactor comprises multiple reactor tubes (e.g., 10 to 500 tubes) arranged within a pressure vessel shell. The tubes typically have a diameter of 5 to 200 mm to minimize any temperature distribution during the CVI reaction. The tubes are hermetically sealed to the shell to form two separate cavities within the reactor. The tube-side cavity constitutes the reactor volume and contains porous particles and silicon-containing precursors during the CVI reaction. The shell-side cavity may contain a heat transfer fluid to heat or cool the contents of the tubes. Alternatively, the tubes can be heated by convection or conduction using resistance heating elements.

[0143] Porous particles can be loaded into the tube, for example, by suction through a porous plate located at one end of the tube. Then, before introducing a predetermined amount of silicon-containing precursor, the tube-side cavity can be sealed, purged using a vacuum, and blown with an inert gas. The tube-side cavity may include a hydrogen-selective membrane element to facilitate the removal of hydrogen byproducts and control of internal pressure.

[0144] When the volume of the porous particle charge is smaller than the reactor volume of the batch pressure reactor, the porous particles are preferably in the form of a moving bed to maintain uniformity in the reactor.

[0145] Reactors used for moving bed reactions include autoclave reactors, which include an internal stirrer. The autoclave can be internally heated via multiple heating rods or tubular heat exchangers. Alternatively, the outer wall of the autoclave can be heated by resistance heating elements or by convection heating. The autoclave reactor may be equipped with hydrogen-selective membrane elements to facilitate the removal of hydrogen byproducts and control of internal pressure. Other methods for maintaining a moving bed of particles during CVI reactions include vibration, ultrasonic treatment, and fluidization techniques. Reactors for moving bed reactions include those from Parr Instrument Company. RTM Stirred pressure reactor system and from Büchi AG RTM Novoclave RTM Stirred autoclave.

[0146] Moving bed intermittent pressure reactors can have any type of reactor structure in which a solid bed can be stirred. For example, these are moving reactors, reactors with moving stirring elements, or gas-pass reactors or combinations thereof.

[0147] The preferred form of motion in a moving bed reactor is rotational motion. Other forms of motion are also applicable. Preferred structural forms of rotating reactors are, for example, drum or tubular reactors, conical reactors, double-cone reactors, reactors with offset cones, spherical reactors, polyhedral reactors, V-shaped reactors, double-V-shaped reactors, or geometric combinations thereof. In the case of a symmetrical structure, the axis of rotation is preferably located on the reactor's axis of symmetry. In the case of an asymmetrical structure, the axis of rotation preferably passes through the reactor's center of gravity. In another preferred embodiment, the axis of rotation is selected to produce tumbling motion. Mixing events within the moving bed reactor are preferably facilitated by internal components. Typical internal components are guide plates, blades, vanes, and plowshares. According to the invention, the orientation of the axis of rotation is freely selectable. The axis of rotation is preferably vertical, horizontal, or oriented at a free angle relative to the horizontal embodiment.

[0148] Another preferred configuration for a moving bed is a stationary batch pressure reactor with moving stirring elements. Preferred geometries for this purpose are cylindrical, conical, spherical, polyhedral, or combinations thereof. The movement of the stirring elements is preferably rotational. Other forms of movement are also applicable. The stirring elements are preferably driven via stirring shafts, and each stirring shaft may have one or more stirring elements. A batch pressure reactor preferably includes multiple stirring shafts, each with one or more stirring elements. The main reactor axis is preferably horizontally or vertically aligned. In another preferred embodiment, the stirring shafts are mounted horizontally or vertically in the reactor in any orientation. For vertically operating batch pressure reactors, preferred configurations are those in which, for example, one or more stirring elements mix the bed material via rotational movement via the main stirring shaft. Additionally, configurations in which two or more stirring shafts operate in parallel are preferred. Preferred configurations also exist in which two or more stirring shafts operate non-parallel to each other. Another preferred configuration of a vertically operating batch pressure reactor is characterized by the use of a screw conveyor. The screw conveyor preferably transports the bed material at the center. Another design according to the invention is a screw conveyor rotating along the edge of the reactor. For horizontally operating batch pressure reactors, preferred configurations are those in which, for example, one or more stirring elements mix the bed material via the rotational motion of a main stirring shaft. Configurations in which two or more stirring shafts operate in parallel are also possible. Configurations in which two or more stirring shafts do not operate parallel to each other are also preferred. For vertically operating batch pressure reactors, preferred stirring elements are those selected from screw agitators, helical agitators, anchor agitators, or generally stirring elements that convey the bed material axially or radially, or simultaneously axially and radially. In the case of horizontally operating batch pressure reactors, it is preferable to have multiple stirring elements on one shaft. Configurations according to the invention for stirring elements in horizontally operating reactors are plowshare agitators, paddle agitators, blade agitators, screw agitators, or generally stirring elements that convey the bed material simultaneously axially and radially. In addition to moving stirring elements, rigid internal components, such as guide plates, are preferred for stationary batch pressure reactors with moving stirring elements. Configurations in which both the reactor and the stirring elements rotate are also particularly preferred.

[0149] As another possibility for mixing, the material bed is preferably subjected to an airflow. A particularly preferred structure is that of a fluidized bed reactor. Further preferred is an intermittent pressure reactor in which a mixing zone is intentionally created within the reactor using pneumatic devices.

[0150] For the structure of a batch pressure reactor, any material is generally suitable, provided that it possesses the necessary mechanical strength and chemical resistance under the appropriate operating conditions. In terms of chemical resistance, a batch pressure reactor can be composed of appropriate solid materials and chemically inactive (pressure-bearing) materials with specific coatings or platings on the parts in contact with the medium.

[0151] These materials are preferably selected from: - Metallic materials, for steel, corresponding to material groups 1 to 11 (according to DIN CEN ISO / TR 15608); for nickel and nickel alloys, corresponding to material groups 31 to 38; for titanium and titanium alloys, corresponding to material groups 51 to 54; for zirconium and zirconium alloys, corresponding to material groups 61 and 62; and for cast iron, corresponding to material groups 71 to 76. - Ceramic materials, including oxide ceramics in single-material systems such as alumina, magnesium oxide, zirconium oxide, and titanium dioxide (capacitor materials), and multi-material systems such as aluminum titanate (a mixture of alumina and titanium oxide), mullite (a mixture of alumina and silicon oxide), lead zirconate titanate (piezoelectric ceramics), or dispersion ceramics such as alumina reinforced with zirconium oxide (ZTA – zirconium oxide reinforced alumina – Al2O3 / ZrO2). - Non-oxide ceramics, such as carbides, examples of which are silicon carbide and boron carbide; nitrides, examples of which are silicon nitride, aluminum nitride, boron nitride and titanium nitride; borides and silicides; and mixtures thereof; and - Composite materials belonging to the following group: particulate composite materials, such as hard alloys, ceramic composites, concrete and polymer concrete, fiber composite materials, such as glass fiber reinforced glass, metal matrix composites (MMC), fiber cement, carbon fiber reinforced silicon carbide, self-reinforcing thermoplastics, reinforced concrete, fiber reinforced concrete, fiber-plastic composites, such as carbon fiber reinforced plastics (CRP), glass fiber reinforced plastics (GRP) and aramid fiber reinforced plastics (ARP), fiber-ceramic composites (ceramic matrix composites (CMC)), infiltrated composite materials, such as metal matrix composites (MMC), dispersion-reinforced aluminum alloys or dispersion-reinforced nickel-chromium alloys, layered composite materials, such as bimetallic, titanium-graphite composites, composite plates and composite pipes, glass fiber reinforced aluminum and sandwich structures, and structural composite materials.

[0152] The surface of electroactive materials deposited via CVI typically reacts with oxygen and usually forms a native oxide layer when exposed to atmospheric oxygen. In the case of silicon, an amorphous silicon dioxide film typically forms immediately upon exposure of the silicon surface to oxygen. The formation of the native oxide layer is typically exothermic, thus requiring careful process control to prevent the particulate material from overheating or even burning during manufacturing. The presence of the native oxide layer is generally associated with irreversible capacity loss and reduced cycle life, and can therefore be detrimental to the performance of the electroactive materials in lithium-ion batteries. Therefore, the method of the present invention may optionally include the step (g) of contacting the surface of the deposited silicon with a passivating agent, wherein the silicon is not exposed to oxygen prior to contact with the passivating agent.

[0153] Step (g) is preferably performed immediately after the final silicon deposition step (i.e., step (c) in the case of a single deposition step), or after the final step (f) in a multi-pass deposition process.

[0154] Passivating agents are defined in this paper as compounds that can modify the surface of electroactive materials in a way that inhibits or prevents the formation of surface oxides.

[0155] Suitable passivating agents include, for example, compounds containing olefin, alkyne or carbonyl functional groups, more preferably terminal olefin, terminal alkyne or aldehyde groups.

[0156] Preferred passivating agents include one or more compounds of the following formula: (i) R-CH=CH-R; (ii) RC≡CR; (iii) O=CH-R; and Wherein R represents H or an unsubstituted or substituted aliphatic or aromatic hydrocarbon group having 1 to 20 carbon atoms, preferably 2 to 10 carbon atoms, or wherein the two R groups in formula (i) form an unsubstituted or substituted hydrocarbon ring structure containing 3 to 8 carbon atoms.

[0157] Particularly preferred passivating agents include one or more compounds of the following formula: (i)CH2=CH-R; and (ii) HC≡CR; Wherein R is as defined above. Preferably, R is unsubstituted.

[0158] Examples of suitable compounds include ethylene, propylene, 1-butene, butadiene, 1-pentene, 1,4-pentadiene, 1-hexene, 1-octene, styrene, divinylbenzene, acetylene, phenylacetylene, norbornene, norbornadiene, and bicyclo[2.2.2]oct-2-ene. Mixtures of different passivating agents may also be used.

[0159] It should be understood that the olefin, alkyne, or carbonyl groups of the passivating agent typically undergo an insertion reaction with the MH group (where M represents an atom of the electroactive material) on the surface of the electroactive material to form a covalently passivated surface resistant to air oxidation. When silicon is the electroactive material, the passivation reaction between the silicon surface and the passivating agent can be understood as a form of hydrosilylation, as schematically illustrated below.

[0160] Other suitable passivating agents include compounds containing active hydrogen atoms bonded to oxygen, nitrogen, sulfur, or phosphorus. For example, passivating agents can be alcohols, amines, thiols, or phosphine. The reaction of the group –XH – with the hydride group at the surface of the electroactive material is understood to lead to the elimination of H2 and the formation of a direct bond between X and the surface of the electroactive material.

[0161] Suitable passivators in this category include compounds such as those with the following formula. (iv) HX-R, Where X represents O, S, NR, or PR, and each R is independently as defined above. The two R groups in formula (iv) may also form an unsubstituted or substituted hydrocarbon ring structure comprising 3 to 8 carbon atoms. Preferably, X represents O or NH, and R represents an optionally substituted aliphatic or aromatic group having 2 to 10 carbon atoms. The amine group may also be incorporated into a 4-10 member aliphatic or aromatic ring structure, such as pyrrolidine, pyrrole, imidazole, piperazine, indole, or purine.

[0162] The contact between the electroactive material and the passivating agent in step (g) can be carried out at a temperature ranging from 25 to 800°C, preferably not exceeding 750°C, or not exceeding 700°C, and at a pressure ranging from 100 kPa to 50 MPa. For example, step (g) can be suitably carried out within the preferred temperature and pressure ranges of steps (c) and / or (f) described herein.

[0163] The passivation in step (g) may optionally be performed in the same batch pressure reactor as in steps (c) and / or (f) for example by cooling the batch pressure reactor to a suitable temperature and venting the byproduct gas from the batch pressure reactor; adding a passivating agent charge to the batch pressure reactor; and allowing the passivating agent to passivate the exposed silicon surface of the composite particles.

[0164] The method of the present invention may further include the step of depositing lithium-ion permeable material into the remaining exposed pores and / or the outer surface of the composite particles after the final deposition in step (c), step (f), or step (g). This further improves the performance of the composite particles when used as an electroactive material in lithium-ion batteries by reducing the surface area of ​​the composite particles and sealing the nanoscale electroactive material domains away from the electrolyte contact.

[0165] Suitable lithium-ion permeable materials include, for example, conductive pyrolytic carbon materials. Conductive pyrolytic carbon materials in the pores and / or on the outer surface of the composite particles are advantageous because they improve electron transport into and out of the composite particle bulk. This contributes to improved rate performance of the composite particles.

[0166] Pyrolytic carbon can be deposited using chemical vapor deposition (CVD), which involves thermally decomposing volatile carbon-containing gases (such as ethylene) onto the surface of silicon-containing composite particles.

[0167] Suitable methods include, for example, the following steps: (h) Combining the composite particles from step (c), step (f), or step (g) with a pyrolytic carbon precursor; and (i) Heating the pyrolytic carbon precursor to a temperature that effectively induces the deposition of pyrolytic conductive carbon material into the pores and / or outer surface of the composite particles.

[0168] Step (h) is suitably performed at a temperature of 300 to 800°C or 400 to 700°C. For example, the temperature in step (i) may not exceed 680°C or 660°C, or 640°C, or 620°C, or 600°C, or 580°C, or 560°C, or 540°C, or 520°C, or 500°C. The minimum temperature in step (i) will depend on the type of carbon precursor used. Preferably, the temperature in step (i) is at least 300°C, or at least 350°C, or at least 400°C, or at least 450°C, or at least 500°C. The pressure in step (i) may be in the range of 100 kPa to 50 MPa.

[0169] Suitable examples of pyrolytic carbon precursors include the hydrocarbons mentioned above.

[0170] Other examples of suitable hydrocarbons include polycyclic hydrocarbons comprising 10 to 25 carbon atoms and optionally 1 to 3 heteroatoms, optionally wherein the polycyclic aromatic hydrocarbons are selected from naphthalene, substituted naphthalenes such as dihydroxynaphthalene, anthracene, tetraphenylene, pentaphenylene, fluorene, acenaphthene, phenanthrene, fluoranthene, pyrene, chrysene, dinaphthalene-benzene, hexabenzobenzene, fluorenone, anthraquinone, anthrone, and their alkyl-substituted derivatives. Suitable pyrolytic carbon precursors also include bicyclic monoterpenes, optionally wherein the bicyclic monoterpenes are selected from camphor, borneol, eucalyptol, camphene, careen, juniper, thujone, and pinene. Other suitable pyrolytic carbon precursors include C2-C10 hydrocarbons, optionally wherein the hydrocarbons are selected from alkanes, alkenes, alkynes, cycloalkanes, cycloalkenes, and aromatics, such as methane, ethylene, propylene, limonene, styrene, cyclohexane, cyclohexene, α-terpinene, and acetylene. Other suitable pyrolytic carbon precursors include phthalocyanine, sucrose, starch, graphene oxide, reduced graphene oxide, pyrene, hexadecylhydropyrene, triphenylene, tetraphenylene, benzo[a]pyrene, dinaphthalene, hexabenzo[a]pyrene, and β-phenylene. A preferred carbon precursor is acetylene.

[0171] The pyrolytic carbon precursor used in step (i) can be used in its pure form or as a diluted mixture with an inert carrier gas (such as nitrogen or argon). For example, the pyrolytic carbon precursor can be used in amounts ranging from 0.1 to 100 vol%, or 0.5 to 20 vol%, or 1 to 10 vol%, or 1 to 5 vol%, based on the total volume of the precursor and the inert carrier gas. The presence of oxygen should again be minimized to prevent undesirable oxidation of the deposited electroactive material. Preferably, the oxygen content is less than 0.01 vol%, more preferably less than 0.001 vol%, based on the total volume of the gas used in step (i).

[0172] CVD deposition of conductive carbon can optionally be carried out in the same batch pressure reactor as step (c) and / or step (f) for example by: cooling the batch pressure reactor to a suitable temperature and venting the byproduct gas from the batch pressure reactor; adding a passivating agent charge to the batch pressure reactor; and heating the reactor to a temperature sufficient to allow the pyrolytic conductive carbon material to be deposited into the pores and / or outer surface of the composite particles.

[0173] Alternatively, conductive carbon deposition via CVD can be carried out in another conventional reactor type (e.g., a fluidized bed reactor or a rotary kiln reactor) under an airflow containing carbon-containing precursors. Alternatively, the carbon coating can be formed by depositing a solution of carbonaceous compounds onto the surface of composite particles followed by pyrolysis.

[0174] The carbon coating offers several advantages: it further reduces the BET surface area of ​​the composite particles by smoothing any surface defects and filling any remaining surface micropores, thereby further reducing first-cycle losses. Additionally, the carbon coating improves the conductivity of the composite particle surface, reducing the need for conductive additives in the electrode composition, and creates an optimal surface for forming a stable SEI layer, thus improving capacity retention during cycling.

[0175] The reduction in the surface area of ​​the composite particles also reduces the amount of binder required to form the electrode active layer containing the composite particles. Excessive binder is known to contribute to decreased rate performance.

[0176] When a carbon coating is present, the silicon-containing composite particles preferably have a particle size of no more than 150 μm. 2 / g, or not exceeding 100mg 2 / g, or not exceeding 80 m 2 / g, or not exceeding 60 m 2 / g, or not exceeding 40 m 2 / g, or not exceeding 30 mg 2 / g, or not exceeding 25m 2 / g, or not exceeding 20 mg 2 / g, or not exceeding 15 mg 2 / g, or not exceeding 10 mg 2 / g, or not exceeding 5 mg 2 / g, or not exceeding 3m 2 / g of BET surface area.

[0177] When the lithium-ion permeable filler material is a conductive pyrolytic carbon material, the same compound can be used simultaneously as the passivating agent in step (g) and the pyrolytic carbon precursor in step (h). For example, if styrene is chosen as the pyrolytic carbon precursor, then silicon will also act as a passivating agent if it is not exposed to oxygen before contacting styrene. In this case, the passivation in step (g) and the deposition of the conductive carbon material in steps (h) and (i) can be carried out simultaneously, for example, at a temperature in the range of 300-800°C. Alternatively, the passivation in step (g) and the deposition of the conductive carbon material in steps (h) and (i) can be carried out sequentially with the same material as the passivating agent and the pyrolytic carbon precursor, but step (i) is carried out at a higher temperature than step (g). For example, step (g) can be carried out at a temperature in the range of 25°C to less than 300°C, and step (i) can be carried out at a temperature in the range of 300-800°C.

[0178] Alternatively, different compounds can be used as the passivating agent in step (g) and the pyrolytic carbon precursor in step (h). For example, the electroactive material can first be contacted with the passivating agent in step (g), and then a conductive pyrolytic carbon material can be deposited in steps (h) and (i), wherein the pyrolytic carbon precursor used in step (h) is different from the passivating agent used in step (g). For example, the passivating agent in step (g) can be styrene, and the pyrolytic carbon precursor in step (h) can be a compound capable of forming the pyrolytic carbon material but not passivating the surface of the electroactive material, such as cyclohexane.

[0179] In the following sections, some preferred embodiments of phases 1 to 7 of the present method will be described in more detail. For clarity, the above-described general or preferred embodiments of the present method (such as starting materials, like porous particles, silicon-containing precursors, dopants, or hydrocarbons, or reaction conditions, such as temperature, pressure, or inert gas filling), or embodiments of the batch pressure reactor or the method execution method, are also referred to below in conjunction with the descriptions of phases 1 to 7.

[0180] In stage 1, the batch pressure reactor is filled with porous particles. Afterward, the batch pressure reactor is typically shut down.

[0181] Packing a batch pressure reactor with porous particles can be carried out, for example, in an inert gas atmosphere or preferably in ambient air. The inert gas can be selected from hydrogen; rare gases such as helium, neon, argon, krypton, xenon; nitrogen; carbon dioxide or synthesis gases or mixtures thereof. Argon or, in particular, nitrogen is preferred.

[0182] In stage 2, a batch pressure reactor is filled with one or more silicon-containing precursors.

[0183] In stage 2, firstly, specifically before filling the batch pressure reactor with the silicon-containing precursor, the batch pressure reactor is filled with an inert gas or vented, with venting being particularly preferred. Examples and preferred embodiments of inert gases have been described above with respect to stage 1. Particularly preferably, the operation is carried out without an inert gas.

[0184] Preferably, a certain amount of silicon-containing precursor is packed into the intermittent pressure reactor so that, relative to the amount of porous particles weighed, a sufficient amount of silicon is deposited to produce the target capacity of silicon-containing composite particles.

[0185] In this context, charging typically means introducing a silicon-containing precursor into a batch pressure reactor. During the introduction of the precursor into the batch pressure reactor, it may be present, for example, in a gaseous, liquid, or sublimable solid state. The batch pressure reactor is then typically shut down in a hermetically sealed manner.

[0186] In stage 2, the batch pressure reactor is packed with one or more silicon-containing precursors and optionally with one or more other components (such as one or more inert gases, hydrogen, one or more dopants, or one or more hydrocarbons). The silicon-containing precursors can typically be introduced into the batch pressure reactor in the form of a mixture or alone, or in the form of a mixture with an inert gas, or as a pure substance. Based on the total pressure of the silicon-containing precursor under standard conditions (according to DIN 1343), the partial pressure of the inert gas is preferably 0 to 99%, more preferably up to 50%, particularly preferably up to 30%, and very preferably up to 5%. In a particularly preferred embodiment, the batch pressure reactor is free of inert gas. Embodiments using such dopants or such hydrocarbons have been described above.

[0187] In stage 3, in other words, after the batch pressure reactor is typically filled with a silicon-containing precursor, the normally closed batch pressure reactor is heated until a target temperature is reached. At the target temperature, decomposition of the silicon-containing precursor begins as silicon deposits in the pores of the porous particles and optionally on the surface of the porous particles. The decomposition of the silicon-containing precursor with silicon deposition can be experimentally determined by an increase in pressure within the batch pressure reactor, not caused by an increase in temperature within the batch pressure reactor. In the case of silicon-containing precursor decomposition, gaseous molecules and silicon are typically formed, causing an increase in pressure within the batch pressure reactor. The volume of the batch pressure reactor is typically kept constant during the implementation of this method. Decomposition temperatures are also listed in standard chemical tables relating to the properties of the chemical substances.

[0188] Preferably, in stage 3, the pressure change during heating of the closed intermittent pressure reactor depends primarily on the temperature change, as can be described, for example, by the thermodynamic equation of state according to equation 1: After the target temperature for decomposing the silicon-containing precursor is reached in stage 3, the temperature in stage 4 of the batch pressure reactor may, for example, be increased, kept constant, or decreased within a small range relative to the target temperature of stage 3.

[0189] In Phase 3, temperature, pressure, or differential pressure measurements in the batch pressure reactor can be performed using measurement techniques and equipment commonly used in batch pressure reactors. After routine calibration, different measuring devices produce the same results.

[0190] The target temperature is preferably in the range of 370 to 1000°C, more preferably 390 to 800°C, and most preferably 400 to 550°C. For SiH4, the target temperature is preferably between 370 and 500°C, more preferably in the range of 390 to 450°C, and very preferably in the range of 400 to 420°C. The target temperature for HSiCl3 is preferably between 400 and 1000°C, more preferably in the range of 600 to 800°C. The target temperature for H2SiCl2 is preferably between 350 and 800°C, more preferably in the range of 450 to 550°C.

[0191] When hydrocarbons are loaded, the target temperature applied at the end of stage 3 and during stage 4 is preferably the temperature at which the hydrocarbons begin to decompose and carbon is deposited in the pores of the porous particles and optionally on the surface of the porous particles. In this embodiment, the selected target temperature is preferably in the range of 250 to 1000°C, more preferably 350 to 850°C, and most preferably 450 to 650°C.

[0192] During stage 4, the pressure in the intermittent pressure reactor is preferably increased to at least 7 bar.

[0193] In a preferred embodiment, the reaction progress during the process is monitored based on pressure changes. In this way, for example, the degree of penetration or the end of penetration can be determined. Penetration refers to the deposition of silicon in the pores of the porous particles and optionally on the surface of the porous particles in stage 4. For example, the end of penetration can be determined based on the absence of any further pressure increase.

[0194] The pressure changes in the batch pressure reactor during stage 4 are generally caused primarily by temperature changes and / or changes in the amount of material during the silicon deposition process, as represented by, for example, Equation 2: The pressure changes in stage 4 are preferably a result of the quantitative changes in silicon deposition. Therefore, it is advantageous that the end of the reaction of the silicon-containing precursor can be identified by the absence of any further pressure increase at the end of stage 4, thus allowing for the efficient triggering of further stages in terms of time without the need for unnecessary removal of unreacted silicon-containing precursors from the reactor to achieve complete conversion.

[0195] In stage 4, the temperature preferably does not increase through heating. The temperature in stage 4 preferably increases due to heat generated by the possible exothermic decomposition of the silicon-containing precursor. Furthermore, a slight temperature decrease in stage 4 is preferred, and a slight temperature decrease of up to 20°C during stage 4 is more preferable.

[0196] The pressure increase in the batch pressure reactor during stage 4 (decomposition of silicon precursors) is preferably higher than the pressure increase during stage 3 (heating of the batch pressure reactor), as can be represented, for example, by equation 3a or 3b: (3a), or (3b).

[0197] In stage 4, the pressure in the batch pressure reactor preferably reaches at least 10 bar, more preferably at least 50 bar, and even more preferably at least 100 bar. In stage 4, the pressure in the batch pressure reactor is preferably kept below 400 bar, more preferably below 300 bar, and especially preferably below 200 bar.

[0198] In stage 4, the dominant temperature in the intermittent pressure reactor is preferably in the range of 100 to 1000°C, more preferably in the range of 300 to 900°C, and most preferably in the range of 380 to 750°C.

[0199] In Phase 4, temperature, pressure, pressure changes, or differential pressure measurements in the batch pressure reactor can be determined using measurement techniques and equipment commonly used in batch pressure reactors. After routine calibration, different measuring devices produce the same results. The amount of substance or change in amount of substance can be determined, for example, by taking a defined volume of sample from the batch pressure reactor and determining its substantial composition in a conventional manner using gas chromatography.

[0200] The heating of the batch pressure reactor in Stage 3 and optionally Stage 4 can be carried out, for example, at a constant heating rate or at a variety of different heating rates. The technician can adjust the heating rate in each individual case according to the process design (e.g., based on the reactor size, the number of porous particles in the reactor, the stirring technique, or the planned reaction time). In Stage 3, it is preferable to heat the entire batch pressure reactor at a rate such that, despite rapid heating, the maximum temperature gradient in the batch pressure reactor at the temperature at which the decomposition of the silicon-containing precursor begins is kept below 1000 °C / m, more preferably below 100 °C / m, and very preferably below 10 °C / m. In this way, for example, it can be ensured that the bulk of the silicon is deposited in the pores of the porous particles, rather than on their outer surfaces.

[0201] The temperature at which the decomposition of a silicon-containing precursor begins can depend on, for example, the porous particles or silicon-containing precursor used, as well as other boundary conditions of the decomposition, such as the partial pressure of the silicon-containing precursor during decomposition, and the presence of other reactive components (e.g., catalysts) that affect the decomposition reaction.

[0202] The heating of the intermittent pressure reactor in stage 3 is preferably carried out at a heating rate of 1-100°C / min, more preferably at a heating rate of 2-50°C / min, and very preferably at a heating rate of 3-10°C / min.

[0203] During the decomposition of the silicon-containing precursor in stage 4, the temperature can be kept constant or varied. The goal is to convert the silicon-containing precursor substantially completely in the shortest possible time to produce a silicon-containing material suitable for use.

[0204] To control the rate of pressure increase at various stages of operation, a variety of technical solutions can be used. To increase or decrease the pressure increase, it is preferable to increase or decrease the heat supplied to the reactor contents, respectively. To reduce the rate of pressure increase, it is also preferable to increase heat removal from the batch pressure reactor by cooling; for this purpose, it is preferable to cool one or more reactor walls or introduce facilities into the reactor to remove heat, examples being cooling pipes or cooling fins. To control the pressure in the reactor very quickly, it is preferable to supply or remove a small amount of gas or evaporating liquid from the batch pressure reactor. In this context, after cooling and / or removing a portion of the total flow, the sub-flow removed from the batch pressure reactor is preferably returned, wholly or partially, to the reactor contents in a closed loop.

[0205] Preferably, the reaction process in monitoring stage 4 is analyzed to identify the end of the reaction, thereby minimizing reactor occupancy time. Methods for observing the reaction process include, for example, temperature measurements to determine exothermic or endothermic events, pressure measurements to determine the reaction process by changing the ratio of solid to gaseous reactor contents, and other techniques that enable observation of changes in the composition of the gas space during the reaction.

[0206] It is preferable to monitor pressure changes, especially pressure increases, in the batch pressure reactor during implementation. This increase is an indicator of the deposition rate, and therefore an indicator of the remaining surface area in the porous particles and / or the resulting silicon-containing material.

[0207] In stage 5, the intermittent pressure reactor is cooled. Cooling is preferably carried out after deposition, optionally cooling to below the target temperature, preferably cooling to the temperature of stage 6.

[0208] In stage 6, the gaseous byproducts of the reaction formed during the deposition process are preferably removed at the deposition temperature or after reaching the temperature required for removal of the gaseous reaction byproducts, for example, by purging from the gas space of the batch pressure reactor. The use of a purge gas is preferred. The batch pressure reactor is preferably purged at least once before being introduced with the purge gas. Preferred purge gases are inert gases, such as rare gases, such as helium, neon, argon, krypton, xenon, or hydrogen, nitrogen, or carbon dioxide, and can be used alone or in mixtures, or as a mixture with oxygen (such as air or lean air).

[0209] The intermittent pressure reactor is preferably purged with a mixture of inert gas and oxygen. In this way, the surface of the silicon-containing composite particles can be modified (e.g., deactivated). For example, any reactive groups present on the surface of the silicon-containing composite particles can be reacted. The mixture of nitrogen and oxygen preferably contains at most 20% by volume, more preferably at most 10% by volume, and particularly preferably at most 5% by volume of oxygen. This step is preferably carried out at a temperature of at most 200°C, more preferably at most 100°C, and particularly preferably at most 50°C.

[0210] In stage 7 of the method, the silicon-containing composite particles are removed from the batch pressure reactor, optionally retaining the inert gas atmosphere present in the batch pressure reactor.

[0211] In a preferred embodiment of the method, stages 2 through 6 are repeated multiple times, in which case the silicon-containing precursor loaded in stage 2 may be the same or different in each case.

[0212] In another preferred embodiment of the method, stage 6 directly follows stage 4; in other words, stage 5 can be omitted; in other words, stage 6 can continue after stage 4 without cooling the intermittent pressure reactor.

[0213] In another preferred embodiment of the method, stages 2 to 6 are repeated individually or multiple times, in which case, optionally, stage 6 is omitted in one or more repetitions.

[0214] In another preferred embodiment, with stage 5 optionally omitted, stages 2 to 6 are repeated individually or multiple times (reaction cycles). In this case, a silicon-free reactive component may also be used in the individual or multiple repetitions. The silicon-free reactive component in each repetition may be the same or different, provided that a reactive component containing a silicon-containing precursor is used in at least one reaction cycle. The silicon-free reactive component preferably does not contain a silicon-containing precursor. The silicon-free reactive component preferably contains one or more hydrocarbons. In this preferred embodiment, the silicon-free reactive component can be used to repeat stages 2 to 6. The preferred silicon-free reactive component is a hydrocarbon. When using a silicon-free reactive component, carbon is preferably deposited in the pores and optionally deposited on the surface of the porous particles or silicon-containing composite particles.

[0215] In a particularly preferred embodiment, in the first reaction cycle, in stage 2, one or more silicon-containing precursors are loaded, and in the second reaction cycle, a reactive component comprising one or more hydrocarbons is loaded, the latter preferably containing no silicon-containing precursor; stage 5 is optionally omitted. In this way, for example, silicon-containing composite particles without an outwardly oriented free silicon surface can be obtained.

[0216] In another preferred embodiment, in the first reaction cycle, in stage 2, a reactive component comprising at least one hydrocarbon and free of silicon-containing precursors is introduced, and in the second reaction cycle, a reactive component comprising one or more silicon-containing precursors is used, optionally omitting stage 5. Optionally, in the third reaction cycle, another hydrocarbon-containing reactive component free of silicon-containing precursors is used, optionally omitting stage 5. As a result, for example, silicon-containing composite particles are obtained, which have a carbon layer between the porous particles and the deposited silicon, and optionally additionally carry an external carbon layer, meaning that there is no outwardly oriented free silicon surface. The preferred reactive component, different from the silicon-containing precursor, is one or more hydrocarbons. Hydrocarbons and their preferred embodiments are described above.

[0217] The reactive component containing one or more hydrocarbons but not silicon precursors preferably contains no other components or one or more inert gases and / or hydrogen and / or more dopants. Dopants and their preferred embodiments have been described above.

[0218] During stages 2 to 6, the porous particles and the resulting silicon-containing composite particles can typically be present in a fixed bed or in a stirred state with mixing. Stirred mixing of the porous particles and / or the resulting silicon-containing composite particles in a batch pressure reactor is preferred. For example, it allows for uniform contact of all porous particles with the reactive components, particularly the silicon-containing precursor, or a uniform temperature distribution within the bed. The particles can be stirred, for example, by stirring internal components of the reactor, by moving the reactor as a whole, or by fluidizing the solids in the reactor using an airflow.

[0219] The current method steps a) to c) are preferably divided into the above-described method stages 1 to 7, and more preferably, steps b) to c) are divided into method stages 1 to 7. Step b) preferably includes stages 1 and 2. Step c) preferably includes stages 3 to 7, especially stages 3 and 4.

[0220] The silicon-containing composite particles obtained by the method of this invention have a diameter percentile d 50 The preferred particle size distribution is a volume-weighted particle size distribution in the range of 0.5 to 20 μm. 50 The value is preferably at least 1.5 µm, more preferably at least 2 µm. Diameter percentile d 50 Preferably, it is up to 13 µm, more preferably up to 8 µm.

[0221] The volume-weighted particle size distribution of silicon-containing composite particles is preferably located at the diameter percentile d. 10 ≥ 0.2 µm and d 90 ≤20.0 μm, more preferably in d 10 ≥ 0.4 µm and d 90 ≤ 15.0 µm, most preferably d 10 ≥ 0.6 µm to d 90 Between ≤12.0 µm.

[0222] Silicon-containing composite particles have a diameter percentile d 10 A volume-weighted particle size distribution of ≤ 10 μm is preferred, more preferably ≤ 5 μm, particularly preferably ≤ 3 μm, and most preferably ≤ 1 μm. (Diameter percentile d) 10 Preferably ≥ 0.2 µm, more preferably ≥ 0.4 µm, and most preferably ≥ 0.6 µm.

[0223] Silicon-containing composite particles have a diameter percentile d 90 A volume-weighted particle size distribution of ≥ 5 μm is preferred, and more preferably ≥ 10 μm is preferred. Diameter percentile d 90 Preferably ≤ 20 µm, more preferably ≤ 15 µm, and most preferably ≤ 12 µm.

[0224] The volume-weighted particle size distribution of the silicon-containing composite particles preferably has a dm of ≤15.0 μm, more preferably ≤12.0 μm, more preferably ≤10.0 μm, particularly preferably ≤8.0 μm, and most preferably ≤4.0 μm. 90 -d 10 Poor. The volume-weighted particle size distribution of the silicon-containing composite particles has a preferred ≥ 0.6 µm, more preferably ≥ 0.8 µm, and most preferably ≥ 1.0 µm d 90 -d 10 Difference.

[0225] Silicon-containing composite particles can be separated or aggregated. Preferably, the silicon-containing composite particles are non-agglomerated and even more preferably non-agglomerated. The terms separated, agglomerated, and non-agglomerated have already been defined above regarding porous particles. The presence of silicon-containing composite particles in the form of aggregates or clusters can be seen, for example, by conventional scanning electron microscopy (SEM).

[0226] Silicon-containing composite particles can have any desired morphology, and therefore can be, for example, flat, irregular, fragmented, spherical or needle-like, with fragmented or spherical particles being preferred.

[0227] According to Wadell's definition, sphericity ψ It is the ratio of the surface area of ​​a sphere of equal volume to the actual surface area of ​​the solid body. In the case of a sphere, ψ The value is 1. According to this definition, the silicon-containing composite particles obtainable by the method of the present invention have a sphericity preferably from 0.3 to 1.0, more preferably from 0.5 to 1.0, and most preferably from 0.65 to 1.0. ψ .

[0228] sphericity S It is the ratio of the circumference of the equivalent circle having the same area A as the projection of the particle onto the surface to the measured circumference U of that projection: In the case of ideally round particles, S The value will be 1. For silicon-containing composite particles obtainable by the method of this invention, the percentile based on the numerical sphericity distribution... S 10 to S 90 sphericity S Preferably, it is in the range of 0.5 to 1.0, more preferably 0.65 to 1.0. For example, sphericity. S It is measured by optical micrographs of individual particles, or preferably, in the case of particles smaller than 10 µm, by scanning electron microscopy and by graphical evaluation using image analysis software such as ImageJ.

[0229] The cycle stability of lithium-ion batteries can be further improved by the morphology and material composition of silicon-containing composite particles, especially by specific surface area or internal porosity.

[0230] Based on the total weight of the silicon-containing composite particles, the silicon-containing composite particles preferably contain 10 to 90% by weight, more preferably 20 to 80% by weight, very preferably 30 to 60% by weight, and especially preferably 40 to 50% by weight of porous particles.

[0231] Based on the total weight of the silicon-containing composite particles (preferably determined by elemental analysis such as ICP-OES), the silicon-containing composite particles preferably contain 10 to 90% by weight, more preferably 20 to 80% by weight, very preferably 30 to 60% by weight, and especially preferably 40 to 50% by weight of silicon obtained by deposition from a silicon-containing precursor.

[0232] If the porous particles contain silicon compounds, such as silicon dioxide, the aforementioned weight percentage of silicon obtained by deposition from the silicon-containing precursor can be determined by subtracting the silicon mass of the porous particles, as determined by elemental analysis, from the silicon mass of the silicon-containing composite particles and dividing the result by the mass of the silicon-containing composite particles.

[0233] The volume of silicon contained in the silicon-containing composite particles and obtained via deposition from the silicon precursor is calculated by dividing the mass fraction of silicon obtained via deposition from the silicon-containing precursor (as a proportion of the total mass of the silicon-containing composite particles) by the density of silicon (2.336 g / cm³). 3 The result of ).

[0234] The pore volume P of silicon-containing composite particles is the sum of the gas-accessible pore volume and the gas-inaccessible pore volume. According to DIN 66134, the Gurwitsch gas-accessible pore volume of silicon-containing composite particles can be determined by gas adsorption measurement using nitrogen.

[0235] The gas-inaccessible pore volume of silicon-containing composite particles can be determined using the following formula: Gas-inaccessible pore volume = (1 / pure material density) – (1 / skeletal density).

[0236] Here, the pure material density of the silicon-containing composite particles is a theoretical density, which can be calculated by multiplying the theoretical pure material densities of the components contained in the silicon-containing composite particles by the sum of their respective weight-based percentage fractions in the total material. Therefore, for example, for silicon-containing composite particles in which silicon is deposited on porous particles: Pure material density = (theoretical pure material density of silicon x fraction of silicon (in weight %)) + theoretical pure material density of porous particles x fraction of porous particles (in weight %).

[0237] Data on the density of pure materials can be obtained by technicians from sources such as the National Institute of Standards and Technology's Ceramic Data Portal (NIST, https: / / srdata.nist.gov / CeramicDataPortal / scd). For example, the density of pure carbon is 2.2 to 2.3 g / cm³. 3 The density of pure silicon dioxide is 2.203 g / cm³. 3 The pure boron nitride material has a concentration of 2.25 g / cm³.3 The pure material concentration of silicon nitride is 3.44 g / cm³. 3 The pure material strength of silicon carbide is 3.21 g / cm³. 3 .

[0238] Based on the volume of silicon contained in the silicon-containing composite particles and obtained from the deposition of silicon-containing precursors, the pore volume P of the silicon-containing composite particles is preferably in the range of 0 to 400 vol%, more preferably in the range of 100 to 350 vol%, and even more preferably in the range of 200 to 350 vol%.

[0239] The porosity contained in the silicon-containing composite particles can be either gas-accessible or gas-inaccessible. The volume ratio of gas-accessible porosity to gas-inaccessible porosity of the silicon-containing composite particles can typically be in the range of 0 (no gas-accessible pores) to 1 (all pores are gas-accessible). The volume ratio of gas-accessible porosity to gas-inaccessible porosity of the silicon-containing composite particles 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.

[0240] The pores of the silicon-containing composite particles can have any desired diameter, such as those in the range of macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm). The silicon-containing composite particles can also contain any desired mixture of different pore types. Preferably, the silicon-containing composite particles contain up to 30% macropores based on the total pore volume; particularly preferred are silicon-containing composite particles without macropores; and very particularly preferred are silicon-containing composite particles having at least 50% (based on the total pore volume) of pores with an average pore diameter of less than 5 nm. More particularly preferably, the silicon-containing composite particles have only pores with a diameter of up to 2 nm.

[0241] The silicon-containing composite particles include a silicon structure having a structural size of preferably up to 1000 nm, more preferably less than 100 nm, and very preferably less than 5 nm in at least one dimension (measured by scanning electron microscopy (SEM) and / or high-resolution transmission electron microscopy (HR-TEM)).

[0242] The silicon-containing composite particles preferably comprise a silicon layer with a thickness of less than 1000 nm, more preferably less than 100 nm, and very preferably less than 5 nm (measured by scanning electron microscopy (SEM) and / or high-resolution transmission electron microscopy (HR-TEM)). The silicon-containing composite particles may also comprise silicon in particulate form. The silicon particles have a diameter preferably at most 1000 nm, more preferably less than 100 nm, and very preferably less than 5 nm (measured by scanning electron microscopy (SEM) and / or high-resolution transmission electron microscopy (HR-TEM)). The figures for the silicon particles are preferably based on the diameter of the circle surrounding the particle in the microscope image.

[0243] Silicon-containing composite particles have a maximum size of 50 μm 2 / g, preferably less than 30 m 2 / g, especially less than 10 m 2 The specific surface area is measured per g. The BET surface area is determined according to DIN 66131 (using nitrogen). Therefore, when silicon-containing composite particles are used as the active material in the anode of a lithium-ion battery, SEI formation can be reduced and the initial coulombic efficiency can be improved.

[0244] The silicon deposited from the silicon-containing precursor in the silicon-containing composite particles may further contain one or more dopants, such as those selected from 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, and rare earth elements. Lithium and / or tin are preferred here. Based on the total weight of the silicon-containing composite particles, the amount of dopants in the silicon-containing composite particles, as determined by ICP-OES, is preferably at most 1% by weight, more preferably at most 100 ppm.

[0245] Silicon-containing composite particles typically exhibit remarkably high stability under compressive and / or shear loads. The pressure and shear stability of silicon-containing composite particles are demonstrated, for example, by the absence or near absence of change in the porous structure of the particles under compressive loads (e.g., during electrode pressing) and shear loads (e.g., during electrode fabrication) as observed in SEM images.

[0246] The silicon-containing composite particles may optionally further comprise elements such as carbon. The carbon exists in the form of thin layers having a layer thickness of at most 1 µm, preferably less than 100 nm, more preferably less than 5 nm, and very preferably less than 1 nm (which can be measured by SEM or HR-TEM). These carbon layers may exist in the pores and on the surface of the silicon-containing composite particles. The order and number of the different layers in the silicon-containing composite particles are also arbitrary through the corresponding repetition of stages 2 to 6. Thus, a layer of another material (e.g., carbon) different from the porous particles may first exist on the porous particles, and this layer may support a silicon layer or a silicon particle layer. It is also possible that a layer of another material, which may be different from or the same as the material of the porous particles, may be present sequentially on the silicon layer or the silicon particle layer, regardless of whether there is a layer of another material different from the material of the porous particles between the porous particles and the silicon layer or the layer composed of silicon particles. The method of the present invention proves particularly advantageous here because the repetition of stages 2 to 6 can be directly followed by the opening of the intermittent pressure reactor without interruption.

[0247] The silicon-containing composite particles preferably contain ≤50% by weight, more preferably ≤40% by weight, and particularly preferably ≤20% by weight of additional elements. The silicon-containing composite particles preferably contain ≥1% by weight, more preferably ≥3% by weight, and particularly preferably ≥2% by weight of additional elements. Figures expressed in weight percent are based on the total weight of the silicon-containing composite particles. In alternative embodiments, the silicon-containing composite particles do not contain any additional elements.

[0248] In a second aspect of the invention, a composition is provided comprising or composed of particulate materials (i.e., current silicon-containing composite particles) obtainable by the methods of the invention. Specifically, a composition is provided comprising silicon-containing composite particles obtainable by the methods of the invention and at least one other component selected from: (i) a binder; (ii) a conductive additive; and (iii) an additional particulate electroactive material. The composition according to the second aspect of the invention can be used as an electrode composition and therefore can be used to form the active layer of an electrode.

[0249] The composition can be a hybrid electrode composition comprising silicon-containing composite particles and at least one additional particulate electroactive material. Examples of the additional particulate electroactive material include graphite, hard carbon, silicon, tin, germanium, aluminum, and lead. The at least one additional particulate electroactive material is preferably selected from graphite and hard carbon, and most preferably, the at least one additional particulate electroactive material is graphite.

[0250] In the case of a mixed electrode composition, based on the total dry weight of the composition, the composition preferably contains 3 to 60% by weight, or 3 to 50% by weight, or 5 to 50% by weight, or 10 to 50% by weight, or 15 to 50% by weight of silicon-containing composite particles.

[0251] At least one additional particulate electroactive material is present in an amount of 20 to 95% by weight, or 25 to 90% by weight, or 30 to 750% by weight.

[0252] At least one additional particulate electroactive material preferably has a D in the range of 10 to 50 µm, more preferably 10 to 40 µm, more preferably 10 to 30 µm, most preferably 10 to 25 µm, for example 15 to 25 µm. 50 Particle size.

[0253] At least one additional particulate electroactive material D 10 The particle size is preferably at least 5 µm, more preferably at least 6 µm, even more preferably at least 7 µm, further preferably at least 8 µm, more preferably at least 9 µm, and even more preferably at least 10 µm.

[0254] At least one additional particulate electroactive material D 90 The particle size is preferably up to 100 µm, more preferably up to 80 µm, more preferably up to 60 µm, even more preferably up to 50 µm, and most preferably up to 40 µm.

[0255] At least one additional particulate electroactive material is preferably selected from carbon particles, graphite particles, and / or hard carbon particles, wherein the graphite and hard carbon particles have a Dx in the range of 10 to 50 µm. 50 Particle size. More preferably, at least one additional particulate electroactive material is selected from graphite particles, wherein the graphite particles have a D-size in the range of 10 to 50 µm. 50 Particle size.

[0256] The composition can also be a non-mixed (or “high-load”) electrode composition that is substantially free of additional particulate electroactive materials. In this context, the term “substantially free of additional particulate electroactive materials” should be interpreted as meaning that the composition contains less than 15% by weight, preferably less than 10% by weight, preferably less than 5% by weight, preferably less than 2% by weight, more preferably less than 1% by weight, and more preferably less than 0.5% by weight of any additional electroactive material (i.e., additional material capable of inserting and releasing metal ions during battery charging and discharging).

[0257] This type of "high-load" electrode composition preferably contains at least 50% by weight, or at least 60% by weight, or at least 70% by weight, or at least 80% by weight, or at least 90% by weight of silicon-containing composite particles obtained according to the method of the invention, based on the total dry weight of the composition.

[0258] The composition may optionally include an adhesive. The adhesive is used to adhere the composition to the current collector and maintain the integrity of the composition. Examples of adhesives that can be used according to the invention include polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, carboxymethyl cellulose (CMC), modified carboxymethyl cellulose (mCMC), sodium carboxymethyl cellulose (Na-CMC), polyvinyl alcohol (PVA), alginate and its alkali metal salts, styrene-butadiene rubber (SBR), and polyimide. The composition may include a mixture of adhesives. Preferably, the adhesive comprises a polymer selected from polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0259] Based on the total dry weight of the composition, the adhesive may be present in an amount of 0.5 to 20% by weight, preferably 1 to 15% by weight, more preferably 2 to 10% by weight, and most preferably 5 to 10% by weight.

[0260] The adhesive may optionally be present in combination with one or more additives that modify the properties of the adhesive (such as crosslinking accelerators, coupling agents and / or adhesive promoters).

[0261] The composition may optionally include one or more conductive additives. Preferred conductive additives are non-electroactive materials included to improve conductivity between the electroactive components of the composition and between the electroactive components of the composition and the current collector. Conductive additives may be selected from carbon black, carbon fibers, carbon nanotubes, graphene, acetylene black, Ketjen black, metal fibers, metal powders, and conductive metal oxides. Preferred conductive additives include carbon black and carbon nanotubes.

[0262] Based on the total dry weight of the composition, one or more conductive additives may be present in a total amount of 0.5 to 20% by weight, preferably 1 to 15% by weight, more preferably 2 to 10% by weight, and most preferably 5 to 10% by weight.

[0263] In a third aspect, the present invention provides an electrode comprising silicon-containing composite particles that are in hydroelectric contact with a current collector and can be obtained by the method according to the invention. The particulate material used to prepare the electrode of the third aspect of the invention may be in the form of a composition according to the second aspect of the invention.

[0264] As used herein, the term current collector refers to any conductive substrate capable of transporting current to and from the electroactive particles in the composition. Examples of materials that can be used as current collectors include copper, aluminum, stainless steel, nickel, titanium, and sintered carbon. Copper is a preferred material. Current collectors are typically in the form of foils or meshes with a thickness between 3 and 500 μm. The particulate material of the present invention can be applied to one or both surfaces of the current collector to a thickness preferably in the range of 10 μm to 1 mm (e.g., 20 to 500 μm, or 50 to 200 μm).

[0265] The electrode of the third aspect of the invention can be manufactured by combining the silicon-containing composite particles of the invention with a solvent and optionally one or more viscosity-modifying additives to form a slurry. The slurry is then cast onto the surface of a current collector and the solvent is removed, thereby forming an electrode layer on the surface of the current collector. Further steps, such as heat treatment, may be suitably performed to cure any binder and / or calendering of the electrode layer. The electrode layer suitably has a thickness in the range of 20 µm to 2 mm, preferably 20 µm to 1 mm, preferably 20 µm to 500 µm, preferably 20 µm to 200 µm, preferably 20 µm to 100 µm, preferably 20 µm to 50 µm.

[0266] Alternatively, the slurry can be formed into a separate film or pad comprising the particulate material of the present invention, for example by casting the slurry onto a suitable casting mold, removing the solvent, and then removing the casting mold. The resulting film or pad is cohesive and independent, which can then be bonded to the current collector by known methods.

[0267] The electrode of the third aspect of the present invention can be used as the anode of a metal-ion battery. Therefore, in a fourth aspect, the present invention provides a rechargeable metal-ion battery comprising an anode including the electrode as described above; a cathode including a cathode active material capable of releasing and reabsorbing metal ions; and an electrolyte between the anode and the cathode.

[0268] The metal ions are preferably lithium ions. More preferably, the rechargeable metal ion battery of the present invention is a lithium ion battery, and the cathode active material is capable of releasing and accepting lithium ions.

[0269] The cathode active material is preferably a composite material based on metal oxides. Examples of suitable cathode active materials include LiCoO2 and LiCo. 0.99 Al 0.01 O2, LiNiO2, LiMnO2, LiCo 0.5 Ni 0.5 O2, LiCo 0.7 Ni 0.3 O2, LiCo 0.8 Ni0.2 O2, LiCo 0.82 Ni 0.18 O2, LiCo 0.8 Ni 0.15 Al 0.05 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2 and LiNi 0.33 Co 0.33 Mn 0.34 O2. The thickness of the cathode current collector is typically between 3 and 500 μm. Examples of materials that can be used as cathode current collectors include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0270] Electrolytes are preferably non-aqueous electrolytes containing metal salts such as lithium salts, and may include, but are not limited to, non-aqueous electrolyte solutions, solid electrolytes, and inorganic solid electrolytes. Examples of usable non-aqueous electrolyte solutions include aprotic organic solvents such as propylene carbonate, ethylene carbonate, butyl carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, sulfolane, methyl sulfolane, and 1,3-dimethyl-2-imidazolium ketone.

[0271] Examples of organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate polymers, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ion-dissociating groups.

[0272] Examples of inorganic solid electrolytes include lithium salt nitrides, halides, and sulfides, such as Li5NI2, Li3N, LiI, LiSiO4, Li2SiS3, Li4SiO4, LiOH, and Li3PO4.

[0273] Lithium salts are suitably soluble in a chosen solvent or a mixture of solvents. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO4, LiBF4, LiBC4O8, LiPF6, LiCF3SO3, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, and CF3SO3Li.

[0274] When the electrolyte is a non-aqueous organic solution, metal-ion batteries preferably include a separator between the anode and cathode. The separator is typically formed of an insulating material with high ion permeability and high mechanical strength. Separators typically have pore sizes between 0.01 and 100 μm and thicknesses between 5 and 300 μm. Examples of suitable electrode separators include microporous polyethylene membranes.

[0275] The diaphragm can be replaced by a polymer electrolyte material, and in this case, the polymer electrolyte material is present within both the composite anode layer and the composite cathode layer. The polymer electrolyte material can be a solid polymer electrolyte or a gel-type polymer electrolyte.

[0276] Example The following examples are provided to further illustrate the invention described herein.

[0277] The analytical methods and instruments used for characterization are as follows: Scanning electron microscopy (SEM / EDX): Microscopic analysis was performed using a Zeiss Ultra 55 scanning electron microscope and an Oxford X-Max 80Nx energy-dispersive X-ray spectrometer. Prior to analysis, carbon vapor deposition was performed on the samples using a Safematic Compact Coating Unit 010 / HV to prevent charging phenomena. Cross-sections of the silicon-containing composite particles were fabricated at 6 kV using a Leica TIC 3X ion cutter.

[0278] Inorganic analysis / elemental analysis: The reported C content in the examples was determined using a Leco CS 230 analyzer; the O and, where appropriate, N and H contents were determined using a Leco TCH-600 analyzer. Qualitative and quantitative determinations of other reported elements were performed by ICP (Inductively Coupled Plasma) optical emission spectrometry (Optima 7300 DV, from Perkin Elmer). For this analysis, the samples were acid-digested (HF / HNO3) in a microwave (Microwave 3000, from Anton Paar). The ICP-OES determinations were guided by ISO 11885 "Water quality—Determination of selected elements by inductively coupled plasma optical emission spectrometry (ICP-OES) (ISO 11885:2007; German version EN ISO 11885:2009)," which is used for the analysis of acidic aqueous solutions (e.g., acidified samples of drinking water, wastewater and other waters, aqua regia extracts from soil and sediments).

[0279] Particle size determination: In the context of this invention, particle size distribution is determined by static laser scattering using a Horiba LA 950 according to ISO 13320. In sample preparation, particular care must be taken regarding the dispersion of particles in the measurement solution to avoid measuring the size of aggregates rather than individual particles. For the measurement, the particles are dispersed in ethanol. For this purpose, the dispersion is sonicated at 250W for 4 minutes in a Hielscher UIS250V ultrasonic laboratory instrument with an LS24d5 ultrasonic welding electrode, whenever necessary, prior to measurement.

[0280] BET surface area measurement: The specific surface area of ​​a material is measured by the BET method (using nitrogen, determined according to DIN ISO 9277:2003-05) using a Sorptomatic 199090 instrument (Porotec) or an SA-9603MP instrument (Horiba) via gas adsorption of nitrogen.

[0281] Skeletal density: According to DIN 66137-2, the skeletal density is determined by the He specific gravity bottle method, which is the density of a porous solid based solely on the volume of the pore space into which gas can enter from the outside.

[0282] Gurwich gas accessible pore volume: According to DIN 66134, the gas accessible pore volume of Gurwitsch gas is determined by measuring the gas adsorption of nitrogen.

[0283] PD50 aperture: The PD50 aperture is calculated as a volume-based median aperture based on the total volume of micropores defined by the Horvath Kawazoe method according to DIN 66135 and mesopores defined by the BJH method according to DIN 66134.

[0284] The materials and equipment used in conducting the experimental embodiments are as follows: The autoclave used consists of a cylindrical lower section (beaker) and a lid with multiple connections (e.g., for gas supply, gas removal, temperature measurement, and pressure measurement). The autoclaves have volumes of 594 ml (AK1), 312 ml (AK2), and 5300 ml (AK3). The autoclave is electrically heated. The agitator used is a very narrow-gap spiral agitator. The height of the agitator is approximately 50% of the net height inside the reactor. The spiral agitator has a design that allows for direct temperature measurement within the bed.

[0285] The 4.0 grade SiH4 used was obtained from Linde GmbH.

[0286] The porous particles used: Porous particles 1 to 6 are porous carbon, porous particle 7 is porous silicon oxide, and porous particle 8 is porous boron nitride.

[0287] Table 1 reproduces the composition and some physical properties of the porous particles 1 to 8 used.

[0288] Examples 1 to 23: Silicon-containing composite particles were produced using monosilane SiH4 as a silicon-containing precursor. Table 2 summarizes the corresponding values ​​of parameter AL, the material number X of the porous particles, and the type of autoclave.

[0289] In Stage 1, the autoclave is filled with Ag of porous material X and then closed, where K is the charge of porous particles per liter of reactor volume. In Stage 2, the autoclave is first emptied. Then, Bg of SiH4 is applied at a pressure of C bar, where the charge of Si per liter of reactor volume is L. In Stage 3, the autoclave is heated to E°C within D minutes, and in Stage 4, the temperature is maintained for F minutes. The pressure is increased according to Equation 1 until the total heating time (D+F) is G minutes. During Stage 4, the pressure is increased to H bar according to Equation 2. During the 12-hour process, the autoclave is cooled to room temperature in Stage 5. After this cooling, the pressure in the autoclave is maintained at 1 bar. In Stage 6, the pressure in the autoclave is reduced to 1 bar, and then the autoclave is purged 5 times with nitrogen, 5 times with oxygen-lean air (5% oxygen fraction), 5 times with oxygen-lean air (10% oxygen fraction), and then purged 5 times with air. In Stage 7, Jg of silicon-containing composite particles in the form of fine black solids are separated.

[0290] Table 3 summarizes the analytical data for the obtained silicon-containing composite particles. Electrochemical cells based on selected examples of the obtained silicon-containing composite particles were prepared according to Example 29. The electrochemical characterization of the silicon-containing composite particles is also listed in Table 3.

[0291] Table 1: Physical properties of the porous particles used:

[0292] Example 24: Silicon-containing composite particles are produced by repeating stages 2 through 6: In Stage 1, the autoclave (AK2) was filled with 5.0 g of porous material 1 and closed, with the porous particles being charged at 50 g per liter of reactor volume. In Stage 2, the autoclave was emptied and charged with 7 g of monosilane SiH4 (12 bar), with Si being charged at 19.63 g per liter of reactor volume. In Stage 3, the autoclave was heated to 420°C over a 65-minute process. Up to this point, the pressure increase conformed to Equation 1. In Stage 4, the temperature was maintained for 180 minutes, during which the pressure increased to 68 bar according to Equation 2. Over a 600-minute process, in Stage 5, the autoclave was cooled to a temperature of 20°C. In Stage 6, after the reactor pressure was reduced to 1 bar by releasing the gaseous reactor contents, the pressure was reduced to 1 mbar in another Stage 2, and 7 g of SiH4 (12 bar) was again charged into the autoclave, with Si being charged at 19.63 g per liter of reactor volume. Subsequently, in the second stage 3, the autoclave was heated to 450°C over a 70-minute process. In the second stage 4, the temperature was maintained for 240 minutes, during which the pressure was increased to 50 bar according to Equation 2. In the final repetition of stage 6, the pressure in the autoclave was reduced to 1 mbar, and after cooling to 30°C over a 600-minute process, the gas space of the autoclave was purged five times with nitrogen, five times with lean air (5% oxygen), five times with lean air (10% oxygen), and then purged five times with air. In stage 7, 12.5 g of silicon-containing composite particles in the form of a fine black powder were separated from the reactor.

[0293] Table 3 summarizes the analytical data of the obtained silicon-containing composite particles.

[0294] Electrochemical characterization of silicon-containing composite particles in the battery according to Example 29 is also listed in Table 3.

[0295] Example 25: Silicon-containing composite particles are produced by repeating stages 2 through 6: In Stage 1, the autoclave (AK3) was filled with 69 g of porous material 1 and closed, with the porous particles being charged at a rate of 40.7 g per liter of reactor volume. In Stage 2, the autoclave was first emptied, and then SiH4 (9.5 bar) was added at a temperature of 300°C, with Si being charged at a rate of 6.8 g per liter of reactor volume. In Stage 3, the autoclave was heated to 420°C over a 15-minute process. Up to this point, the pressure increase conformed to Equation 1. In Stage 4, the temperature was maintained for 30 minutes, during which the pressure increased to 38 bar according to Equation 2. In Stage 6, after the reactor pressure was reduced to 1 bar by releasing the gaseous reactor contents, the pressure was further reduced to 1 mbar in another Stage 2, and SiH4 (11 bar) was again added to the autoclave, with Si being charged at a rate of 7.9 g per liter of reactor volume. In the second stage, 3, the autoclave was heated to 420°C over a 10-minute process. In the second stage, 4, the temperature was maintained for 30 minutes, during which the pressure was increased to 23 bar according to Equation 2. In the final repetition of stage 6, the pressure in the autoclave was reduced to 1 mbar, and after cooling to 30°C over a 600-minute process, the gas space of the autoclave was purged five times with nitrogen, five times with lean air (5% oxygen), five times with lean air (10% oxygen), and then purged five times with air. In stage 7, 140 g of silicon-containing composite particles in the form of a fine black powder were separated from the reactor.

[0296] Table 3 summarizes the analytical data of the obtained silicon-containing composite particles.

[0297] Electrochemical characterization of silicon-containing composite particles in the battery according to Example 29 is also listed in Table 3.

[0298] Example 26: Silicon-containing composite particles are produced by repeating stages 2 through 6 multiple times: In Stage 1, the autoclave (AK3) was filled with 180 g of porous material 1 and closed, with the porous particles being charged at a rate of 106.1 g per liter of reactor volume. In Stage 2, the autoclave was emptied and then SiH4 (9.5 bar) was added at a temperature of 370°C, with Si being charged at a rate of 7.1 g per liter of reactor volume. In Stage 3, the autoclave was heated to 420°C over a 10-minute process. So far, the pressure increase conforms to Equation 1. In Stage 4, the temperature was maintained for 30 minutes, during which the pressure increased to 24 bar according to Equation 2. In Stage 6, after the reactor pressure was reduced to 1 bar by releasing the gaseous reactor contents, the pressure was further reduced to 1 mbar in another Stage 2, and SiH4 (9.5 bar) was again added to the autoclave, with Si being charged at a rate of 5.6 g per liter of reactor volume. In stage 3 of the second phase, the autoclave is heated to 420°C over a 10-minute period. In stage 4 of the second phase, the temperature is maintained for 30 minutes, during which the pressure increases to 22 bar according to Equation 2. In stage 6 of the second phase, the reactor pressure is reduced to 1 bar by releasing the gaseous reactor contents. In stage 2 of the third phase, the pressure is reduced to 1 mbar, and SiH4 (9.5 bar) is added back to the autoclave at 400°C, with a Si charge of 5.6 g per liter of reactor volume. In stage 3 of the third phase, the autoclave is heated to 420°C over a 10-minute period. In stage 4 of the third phase, the temperature is maintained for 30 minutes, during which the pressure increases to 20 bar according to Equation 2. In stage 6, the reactor pressure is reduced to 1 bar by releasing the gaseous reactor contents. In stage 2 of the fourth phase, the pressure is reduced to 1 mbar, and SiH4 (11 bar) is added back to the autoclave at 400°C, with a Si charge of 6.4 g per liter of reactor volume. In stage 3 of the fourth phase, the autoclave is heated to 420°C over a 10-minute process. In stage 4 of the fourth phase, the temperature is maintained for 30 minutes, during which the pressure increases to 23 bar according to Equation 2. After the reactor pressure is reduced to 1 bar in stage 6 by releasing the gaseous reactor contents, the pressure is reduced to 1 mbar in stage 2 of the fifth phase, and SiH4 (11 bar) is added back to the autoclave at 400°C, with a Si charge of 6.4 g per liter of reactor volume. In stage 3 of the fifth phase, the autoclave is heated to 420°C over a 10-minute process. In stage 4 of the fifth phase, the temperature is maintained for 30 minutes, during which the pressure increases to 23 bar according to Equation 2. After the reactor pressure is reduced to 1 bar in stage 6 by releasing the gaseous reactor contents, the pressure is reduced to 1 mbar in stage 2 of the sixth phase, and SiH4 (11 bar) is added back to the autoclave at 400°C, with a Si charge of 7.1 g per liter of reactor volume.In stage 6, part 3, the autoclave was heated to 420°C over a 10-minute process. In stage 6, part 4, the temperature was maintained for 30 minutes, during which the pressure was increased to 23 bar according to equation 2. In the final repetition of stage 6, the pressure in the autoclave was reduced to 1 mbar, and after cooling to 30°C over a 600-minute process, the gas space of the autoclave was purged five times with nitrogen, five times with lean air (5% oxygen), five times with lean air (10% oxygen), and then purged five times with air. In stage 7, 376 g of silicon-containing composite particles in the form of a fine black powder were separated from the reactor.

[0299] Table 3 summarizes the analytical data of the obtained silicon-containing composite particles.

[0300] Electrochemical characterization of silicon-containing composite particles in the battery according to Example 29 is also listed in Table 3.

[0301] Example 27: Silicon-containing composite particles are produced by repeatedly performing stages 2 to 6 and by controlling the reaction through reactor pressure. In Stage 1, the autoclave (AK3) is filled with 180 g of porous material 1 and closed, with a charge of 106.1 g of porous particles per liter of reactor volume. In Stage 2, the autoclave is emptied and SiH4 (9.5 bar) is added at 370°C, with a Si charge of 7.1 g per liter of reactor volume. In Stage 3, the autoclave is heated to 420°C over a 10-minute process. The pressure increase so far is according to Equation 1. The temperature in Stage 4 is maintained for 30 minutes, during which the pressure increases to 24 bar according to Equation 2. In Stage 6, after reducing the reactor pressure to 1 bar by releasing the gaseous reactor contents, the pressure in Stage 2 is reduced to 1 mbar, and SiH4 (9.5 bar) is again added to the autoclave at 400°C, with a Si charge of 6.1 g per liter of reactor volume. In the second stage, 3, the autoclave is heated to 420°C over a 10-minute process; the temperature from the second stage, 4, is maintained for 30 minutes, during which the pressure increases to 21 bar according to Equation 2. In stage 6, after the reactor pressure is reduced to 1 bar by releasing the gaseous reactor contents, the pressure from the third stage, 2, is reduced to 1 mbar, and SiH4 (9.5 bar) is added back to the autoclave at 400°C, with a Si charge of 6.1 g per liter of reactor volume. In the third stage, 3, the autoclave is heated to 420°C over a 10-minute process; the temperature from the third stage, 4, is maintained for 30 minutes, during which the pressure increases to 20 bar according to Equation 2. In stage 6, after the reactor pressure is reduced to 1 bar by releasing the gaseous reactor contents, the pressure from the fourth stage, 2, is reduced to 1 mbar, and SiH4 (11 bar) is added back to the autoclave at 400°C, with a Si charge of 7.1 g per liter of reactor volume. In stage 3 of the fourth phase, the autoclave is heated to 420°C over a 10-minute period. In stage 4 of the fourth phase, the temperature is maintained for 30 minutes, during which the pressure increases to 23 bar according to Equation 2. In stage 6, after the reactor pressure is reduced to 1 bar by releasing the gaseous reactor contents, the pressure from stage 2 of the fifth phase is reduced to 1 mbar, and SiH4 (11 bar) is added back to the autoclave at 400°C, with a Si charge of 7.1 g per liter of reactor volume. In stage 3 of the fifth phase, the autoclave is heated to 420°C over a 10-minute period. In stage 4 of the fifth phase, the temperature is maintained for 30 minutes, during which the pressure increases to 23 bar according to Equation 2. In stage 6, after the reactor pressure is reduced to 1 bar by releasing the gaseous reactor contents, the pressure from stage 2 of the sixth phase is reduced to 1 mbar, and SiH4 (11 bar) is added back to the autoclave at 400°C, with a Si charge of 7.1 g per liter of reactor volume.In stage 6, 3, the autoclave was heated to 420°C over a 10-minute period. In stage 6, 4, the temperature was maintained for 30 minutes, during which the pressure increased to 23 bar according to Equation 2. After reducing the reactor pressure to 1 bar in stage 6 by releasing the gaseous reactor contents, the pressure in stage 7, 2, was reduced to 1 mbar, and SiH4 (11 bar) was added back to the autoclave at 400°C, with a Si charge of 7.1 g per liter of reactor volume. In stage 7, 3, the autoclave was heated to 420°C over a 10-minute period. After 20 minutes in stage 7, 4, the recorded pressure increases decreased significantly over time. The lower steepness of the pressure curve indicated a low surface area in the material, therefore the experiment was terminated at a pressure of 22.5 bar, where the pressure in the autoclave decreased to 1 mbar. After cooling the autoclave to 30°C over a 600-minute process, the gas space of the autoclave was purged five times with nitrogen, five times with oxygen-lean air (5% oxygen), five times with oxygen-lean air (10% oxygen), and then purged five times with air. In stage 7, 439 g of silicon-containing composite particles in the form of fine black powder were separated from the reactor.

[0302] Table 3 summarizes the analytical data of the obtained silicon-containing composite particles.

[0303] Electrochemical characterization of silicon-containing composite particles in the battery according to Example 29 is also listed in Table 3.

[0304] Example 28: Preparation of silicon-containing composite particles using in-situ carbon coating: In Stage 1, the autoclave (AK2) was filled with 8 g of porous material 1 and closed, with a charge of 80.1 g of porous particles per liter of reactor volume. In Stage 2, the autoclave was first emptied and then SiH4 (16 bar) was added, with a charge of 7.1 g of Si per liter of reactor volume. In Stage 3, the autoclave was heated to 420°C over a 40-minute process. The pressure increase so far conforms to Equation 1. In Stage 4, the temperature was maintained for 170 minutes, during which the pressure increased to 85 bar according to Equation 2. Over a 600-minute process, in Stage 5, the autoclave was cooled to a temperature of 20°C. In Stage 6, after reducing the reactor pressure to 1 bar by releasing the gaseous reactor contents, the pressure was reduced to 1 mbar in the second Stage 2, and 2 g of liquid styrene was added to the autoclave. In the second Stage 3, the autoclave was heated to 650°C over a 90-minute process, and in the second Stage 4, the temperature was maintained for 120 minutes. In stage 6, the pressure in the autoclave was reduced to 1 bar, followed by purging with nitrogen five times, then with lean air (5% oxygen) five times, then with lean air (10% oxygen) five times, and finally with air five times. In stage 7, 17.3 g of silicon-containing composite particles in the form of fine black powder were separated from the reactor.

[0305] Table 3 summarizes the analytical data of the obtained silicon-containing composite particles.

[0306] Electrochemical characterization of silicon-containing composite particles in the battery according to Example 29 is also listed in Table 3.

[0307] Example 29: Electrochemical characterization of silicon-containing composite particles used as active materials in lithium-ion battery anodes: 29.71 g of polyacrylic acid (dried to constant weight at 85 °C; Sigma-Aldrich, Mw ~450,000 g / mol) and 756.6 g of deionized water were stirred for 2.5 h using a shaker (290 l / min) until the polyacrylic acid was completely dissolved. 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 SenTixRJD probe). The solution was then mixed again using a shaker for 4 h. 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, 3.40 g of silicon-containing composite particles from each of Examples 1, 6, 7, 9, 10, 11, 22, 23, 27, or 30 were stirred at 2000 rpm for 1 minute. Then, 1.21 g of 8% conductive carbon black dispersion and 0.8 g of deionized water were added and combined at 2000 rpm on a planetary mixer. The mixture was then dispersed in a dissolver at 3000 rpm and a constant temperature of 20°C for 30 minutes. The ink was degassed again in a planetary mixer at 2500 rpm under reduced pressure for 5 minutes. The completed dispersion was then applied to a 0.03 mm thick copper foil (Schlenk Metallfolien, SE-Cu58) using a coating rack (Erichsen, model 360) with a gap height of 0.1 mm. The resulting anodized coating was then dried at 50°C and 1 bar for 60 minutes. The average basis weight of the dried anodized coating was 1.9 mg / cm³. 2 And the coating density is 0.9 g / cm³. 3 .

[0308] Electrochemical studies were conducted on a coin cell (CR2032 type, Hohsen Corp.) with a two-electrode arrangement. The electrode coating was used as either the counter or anode (Dm = 15 mm); a content of 94.0% and an average basis weight of 15.9 mg / cm³ were used. 2 A 6:2:2 coating of lithium nickel manganese cobalt oxide (obtained from SEI) was used as the working electrode or positive electrode (Dm = 15 mm). Glass fiber filter paper (Whatman, GD D type) impregnated with 60 μl of electrolyte was used as the separator (Dm = 16 mm). The electrolyte consisted of a 1.0 mol solution of lithium hexafluorophosphate in a 1:4 (v / v) mixture of ethylene fluorocarbonate and diethyl carbonate. The battery was constructed in a glove box (< 1 ppm H₂O, O₂); the water content in the dry matter of all components used was less than 20 ppm.

[0309] Electrochemical tests were conducted at 20°C. Using the cc / cv (constant current / constant voltage) method, the battery was charged at a constant current of 5 mA / g (equivalent to C / 25) in the first cycle, and at a constant current of 60 mA / g (equivalent to C / 2) in subsequent cycles. Upon reaching a voltage limit of 4.2 V, the battery was charged at a constant voltage until the current dropped below 1.2 mA / g (equivalent to C / 100) or 15 mA / g (equivalent to C / 8). Using the cc (constant current) method, the battery was discharged at a constant current of 5 mA / g (equivalent to C / 25) in the first cycle, and at a constant current of 60 mA / g (equivalent to C / 2) in subsequent cycles until reaching a voltage limit of 2.5 V. The specific current chosen was based on the weight of the positive electrode coating. The ratio of the battery's charge capacity to its discharge capacity is called the coulombic efficiency. Electrodes were selected to establish a cathode to anode capacity ratio of 1:1.2.

[0310] Table 3 lists the electrochemical test results of full cells of lithium-ion batteries containing active materials from Examples 1, 6, 7, 9, 10, 11, 22, 23, 27 or 30.

[0311] Comparative Example 30: Production of silicon-containing composite particles 2.2 g of porous particles 1 were introduced into a 1-liter tubular reactor, and the reactor was then shut off. The tubular reactor was subsequently heated to 410°C and passed through a nitrogen gas stream of 10% SiH4 for 5 hours. After cooling, 5.24 g of silicon-containing composite particles in the form of a black powder were separated.

[0312] The resulting product has a silicon content of 56% by weight (ICP) and 9 m 2 Surface area per g, 2.16 g / cm³ 3 The density (He specific gravity bottle method) and oxygen content of 8.76% by weight.

[0313] Electrochemical tests were performed on a full-cell lithium-ion battery according to Example 29. The corresponding results are also listed in Table 3.

[0314] Figure 1 SEM micrographs of the cross-section of the silicon-containing composite particles from Example 1 are shown.

[0315] Figure 2 SEM micrographs of a cross-section of the silicon-containing composite particle from Comparative Example 30 are shown.

[0316] In Comparative Example 30, 5.24 g of material was produced in a 1000 ml reactor over a period of 300 minutes (without a heating phase) using a non-inventive method; in Example 1, 11.4 g of material was produced in a 312 ml reactor over a period of 195 minutes using the method of the present invention. Therefore, in Example 1, the material yield was increased by 10.7 times relative to time and reactor volume compared to Example 30.

[0317] Furthermore, a comparison of SEM micrographs of the cross-sections of the materials from Example 1 and Comparative Example 30 reveals that the material produced in Example 1 exhibits greater uniformity in silicon content among the particles. One indicator of this is the color of the individual particles in the SEM micrograph. Lighter colors indicate a higher silicon content relative to all other particles, while darker colors indicate a lower silicon content relative to all other particles. Similar grayscale values ​​for two or more particles indicate similar silicon content. Therefore, silicon-containing composite particles can be obtained much faster by the method of the present invention, further characterized by a very uniform deposition of silicon in the pores and on the surface of the porous particles, and due to its stability and electrochemical properties, it is particularly suitable as an active material in lithium-ion battery anodes.

[0318] Table 3: Analytical data of silicon-containing composite particles:

Claims

1. A method for preparing silicon-containing composite particles, the method comprising the following steps: (a) Provides a variety of porous conductive particles including micropores and / or mesopores, wherein: (i) D of the porous conductive particles 50 The particle size ranges from 0.5 to 200 µm; (ii) The total pore volume of micropores and mesopores, measured by gas adsorption, ranged from 0.4 to 2.2 cm³. 3 Within the range of / g; (iii) PD measured by gas adsorption 50 Aperture not exceeding 30 nm; (b) Combining the charge of the porous conductive particles with a charge of a silicon-containing precursor in an intermittent pressure reactor, wherein the charge of the porous conductive particles has a volume of at least 20 cm³. 3 / L reactor volume (cm²) 3 / L RV ), and the charge of the silicon-containing precursor comprises at least 2 g silicon per liter of reactor volume (g / L) RV );and (c) Heating the reactor to a temperature that effectively causes silicon to deposit in the pores of the porous conductive particles, thereby providing the silicon-containing composite particles; The intermittent pressure reactor is a moving bed intermittent pressure reactor, and the porous particles are stirred during step (c).

2. The method according to claim 1, wherein the moving bed intermittent pressure reactor is selected from a moving reactor, a reactor with a moving stirring element, a gas-passing reactor, or a combination thereof.

3. The method according to claim 2, wherein the moving bed intermittent pressure reactor is a fluidized bed reactor.

4. The method of claim 1, wherein the intermittent pressure reactor comprises a moving stirring element.

5. The method of claim 4, wherein the movement of the one or more stirring elements is a rotational movement.

6. The method of claim 5, wherein the intermittent pressure reactor is operated horizontally or vertically.

7. The method of claim 6, wherein the intermittent pressure reactor is vertically operated, and wherein the one or more stirring elements are selected from helical stirrers, spiral stirrers, and anchor stirrers.

8. The method of claim 6, wherein the intermittent pressure reactor is horizontally operated, and wherein the one or more stirring elements are selected from plowshare agitators, paddle agitators, blade agitators, and spiral agitators.

9. The method of claim 4, wherein the intermittent pressure reactor is a high-pressure reactor containing an internal stirrer.

10. The method of claim 9, wherein the autoclave comprises a spiral stirrer with a narrow gap.

11. The method according to any of the preceding claims, wherein the pressure in step (c) is at least 200 kPa, or at least 300 kPa, or at least 500 kPa, or preferably at least 700 kPa, or at least 1,000 kPa, or at least 1,500 kPa, or at least 2,000 kPa, or at least 2,500 kPa, or at least 3,000 kPa, or at least 4,000 kPa, or at least 5,000 kPa.

12. The method according to any one of the preceding claims, wherein the temperature in step (c) is in the range of 300 to 800 °C, or in the range of 300 to 750 °C, or in the range of 300 to 700 °C, or in the range of 300 to 650 °C, or in the range of 300 to 600 °C, or in the range of 320 to 550 °C, or in the range of 320 to 500 °C, or in the range of 340 to 450 °C, or in the range of 350 to 450 °C, or in the range of 300 to 395 °C, or in the range of 320 to 380 °C.

13. The method according to any one of the preceding claims, wherein, in addition to the silicon-containing precursor, the intermittent pressure reactor further comprises an inert filling gas or hydrogen.

14. The method according to any one of the preceding claims, further comprising the step of contacting the surface of the deposited silicon with a passivating agent, wherein the silicon is not exposed to oxygen prior to contacting the passivating agent.

15. The method according to any one of the preceding claims, wherein the intermittent pressure reactor comprises an integrated hydrogen-selective membrane.

16. The method of claim 15, wherein hydrogen byproducts are discharged from the reactor as the reaction proceeds.

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