Method for producing silicon-containing composite particles

Abstract

To provide a process for preparing silicon-containing composite particles suitable for use as anode active materials in lithium-ion batteries.SOLUTION: The process comprises the steps of: (a) providing a plurality of porous particles comprising micropores and / or mesopores, where (i) the D50 particle diameter of the porous particles is 0.5 to 200 μm, (ii) the total pore volume of micropores and mesopores measured by gas adsorption is 0.4 to 2.2 cm3 / g, and (iii) the PD50 pore diameter measured by gas adsorption is 30 nm or less; (b) combining a charge of the porous particles with a charge of a silicon-containing precursor in a batch pressure reactor, where the charge of porous particles has a volume of at least 20 cm3 per liter of reactor volume, and where the charge of the silicon-containing precursor comprises at least 2 g of silicon per liter of reactor volume; and (c) heating the reactor to a temperature effective to cause deposition of silicon in the pores of the porous particles, thereby providing the silicon-containing composite particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing silicon-containing composite particles by depositing silicon within the pores of porous particles. Silicon-containing composite particles are generally suitable for use as a negative electrode active material in metal-ion secondary batteries. [Background technology]

[0002] Rechargeable metal-ion batteries are widely used in portable electronic devices such as mobile phones and laptops, and their application in electric and hybrid vehicles is progressing. Rechargeable metal-ion batteries generally include a negative electrode in the form of a metal current collector with a layer of electroactive material, which is defined as a material that can insert and release metal ions during charging and discharging of the battery. The terms “positive electrode” and “negative electrode” are used herein in the sense that the battery is positioned across the load such that the negative electrode is the negative electrode. When a metal-ion battery is charged, metal ions are transported from the metal-ion-containing positive electrode layer through the electrolyte to the negative electrode and inserted into the negative electrode material. In this specification, the term “battery” is used to refer to both a device having a single positive electrode and a single negative electrode, and a device having multiple positive electrodes and / or multiple negative electrodes.

[0003] We are interested in improving the gravimetric and / or volumetric capacity of rechargeable metal-ion batteries. To date, commercially available lithium-ion batteries have been limited to those using graphite as the negative electrode active material. When the graphite negative electrode is charged, lithium intercalates between the graphite layers, empirically formula Li x This forms a material containing C6 (where x is greater than 0 and less than or equal to 1). As a result, the maximum theoretical capacity of a lithium-ion battery made of graphite is 372 mAh / g, while the practical capacity is somewhat lower (approximately 340-360 mAh / g). Other materials such as silicon, tin, and germanium can intercalate lithium at considerably higher capacities than graphite, but they are not yet widely used commercially because it is difficult to maintain sufficient capacity over a large number of charge-discharge cycles.

[0004] Silicon, in particular, is recognized as a promising alternative to graphite in the manufacture of rechargeable metal-ion batteries with high gravimetric and volumetric capacities due to its very large capacity relative to lithium (see, for example, Insertion Electrode Materials 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 3,600 mAh / g in lithium-ion batteries (Li 15 It is Si4-based. However, when silicon is lithium-ionized to its maximum capacity through lithium intercalation of bulk silicon, the capacity of the silicon material increases significantly, by up to 400%. Repeated charging and discharging places a large mechanical stress on the silicon material, resulting in fracture and delamination of the silicon anode material. The volume contraction of silicon particles due to delamination can cause a loss of electrical contact between the anode material and the current collector. Furthermore, a drawback is that the solid electrolyte interface (SEI) layer formed on the silicon surface does not have sufficient mechanical resistance to cope with the expansion and contraction of silicon. As a result, when the silicon surface is newly exposed, the electrolyte decomposes, the thickness of the SEI layer increases, and lithium is irreversibly consumed. These failure mechanisms lead to an unacceptable decrease in electrochemical capacity during continuous charge-discharge cycles.

[0005] Many methods have been proposed to solve problems related to the capacity changes observed during charging of silicon-containing negative electrodes. Fine silicon structures with a cross-section of 150 nm or less, such as silicon films and silicon nanoparticles, have been reported to be more resistant to capacity changes during charging and discharging compared to micron-sized silicon particles. However, none of these are suitable for commercial-scale applications in their original state; nanoscale particles are difficult to prepare and handle, and silicon films do not provide sufficient bulk capacity.

[0006] WO2007 / 083155 discloses that improved capacity retention may be achieved by using silicon particles with a high aspect ratio, i.e., the ratio of the maximum particle size to the minimum particle size. The small cross-section of such particles reduces the structural stress on the material caused by capacity changes during charge and discharge. However, such particles can be difficult and costly to manufacture and can be fragile. Furthermore, the high surface area can lead to excessive SEI formation, resulting in excessive capacity loss in the first charge-discharge cycle.

[0007] It is also commonly known that electroactive materials such as silicon can be deposited within the pores of porous carrier materials such as activated carbon. These composites offer 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) disclose a silicon-carbon composite material in which a porous carbon substrate provides a conductive framework and silicon nanoparticles are uniformly deposited within the pore structure of the substrate. This composite material has been shown to have improved capacity retention over multiple charge cycles, although the initial capacity (mAh / g) of the composite material is significantly lower than that of silicon nanoparticles.

[0008] The present inventors have previously reported the development of a class of electroactive materials having a composite structure in which nanoscale electroactive materials such as silicon are deposited on a highly porous conductive particle material, such as a porous carbon material with a porous framework.

[0009] For example, WO2020 / 095067 and WO2020 / 128495 report that the improved electrochemical performance of these materials can be attributed to the way in which the electroactive material is located in porous materials in the form of small domains with dimensions on the order of a few nanometers or less. Such fine electroactive structures are thought to have lower resistance to elastic deformation and higher fracture resistance compared to larger electroactive structures, thus enabling lithiation and delithiation without applying excessive structural stress. As a result, this electroactive material exhibits good reversible capacity retention over multiple charge-discharge cycles. Next, by controlling the loading of silicon within the porous carbon skeleton so that only a portion of the pore volume is occupied by uncharged silicon, the unoccupied pore volume of the porous carbon skeleton can accommodate a considerable amount of silicon expansion inside. Furthermore, by arranging nanoscale silicon domains in small mesopores and / or micropores as described above, SEI formation is limited because only small areas of the silicon surface can access the electrolyte. Since further silicon exposure in subsequent charge-discharge cycles is substantially prevented, SEI formation is not a critical failure mechanism leading to capacity loss. This is in stark contrast to the excessive SEI formation that characterizes, for example, the material disclosed by Guo (see above).

[0010] The materials described in WO2020 / 095067 and WO2020 / 128495 were synthesized by chemical vapor infiltration (CVI) in different reactor systems (stationary, rotating, and FBR). Porous conductive particles are contacted as a mixture with an inert gas to a flow of silicon-containing precursor (CVI), typically silane gas, at atmospheric pressure and a temperature of 400–700°C. All of these reactor configurations operate in batch mode for the solid carbon scaffold and in continuous mode for the silicon precursor gas. The reaction rate of silane is fast at this temperature, but the silane molecules must travel through meandering paths across the pore system of the solid particles. In other words, relatively high temperatures are required to obtain homogeneous infiltration in such reactor systems to avoid mass transfer becoming a rate-limiting step. As a result, composite products are formed with a relatively large surface area and, on average, a relatively low content of hydride-terminated silicon. All of these factors are thought to lead to a decrease in electrochemical performance.

[0011] Another drawback of systems using a continuous flow of silicon-containing precursor gas is the need for good mixing of the solids within the gas; otherwise, non-uniformity of composition can occur in the product batch. If effective mixing does not occur, solids that have been in contact with the gas for a longer time will contain more silicon than solids that have been in contact with the unreacted silane gas flow for a shorter time, resulting in uneven deposition across the powder bed.

[0012] Simply lowering the temperature of the CVI process does not solve the aforementioned drawbacks. At low temperatures, mass transfer becomes a rate-limiting process, leading to poor penetration of the porous carbon framework, a non-homogeneous silicon distribution, and the formation of coarse silicon domains.

[0013] US10,147,950B2 describes the deposition of silicon from monosilane, SiH4, onto porous carbon by a CVD (chemical vapor deposition) process at 300–900°C, preferably in a tubular furnace or equivalent type with particle agitation. This process uses nitrogen as the inert gas and mixes 2 mol% of monosilane. Such conditions require very long reaction times. US10,147,950B2 mentions various temperature and pressure ranges.

[0014] WO2012 / 097969 A1 describes the deposition of ultrafine silicon particles in the range of 1–20 nm on a porous carbon support by heating silane as a silicon precursor at 200–950°C, where the silane is diluted with an inert gas to prevent aggregation and / or formation of thick layers of deposited silicon particles. Deposition is carried out at a pressure range of 0.1–5 bar.

[0015] Motevalian et al, Ind.Eng.Chem.Res.2017,56,14995, describe the deposition of silicon layers under increased pressure, although not in the presence of a porous matrix. Here again, the silicon precursor used, in this case monosilane, SiH4, is present at a very low concentration of up to 5 mol% of the total gas volume.

[0016] The processes described above generally require long reaction times to achieve a high silicon fraction in silicon-containing composite particles. Another drawback of these processes is that only a small fraction of the supplied reactive gas reacts, meaning the gas leaving the reactor must undergo expensive and inconvenient recycling or disposal, which further increases costs, especially when using silicon precursors that comply with stringent technical safety requirements. [Overview of the project]

[0017] Therefore, in the art, there is a need for a method for producing silicon-containing composite particles that reduces or solves at least one of the drawbacks discussed above, preferably the drawbacks discussed for high-temperature and low-temperature CVI processes or long reaction times. The process starting from porous particles and a silicon precursor can preferably be carried out technically simply. The silicon-containing composite particles preferably have a high storage capacity for lithium ions, which preferably enables high cycle stability when used as an active material in the negative electrode of a lithium-ion battery.

DETAILED DESCRIPTION OF THE INVENTION

[0018] In a first aspect, the present invention provides a method for producing silicon-containing composite particles, the method comprising the following steps: (a) providing a plurality of porous particles comprising micropores and / or mesopores, (i) the D 50 particle size of the porous particles is in the range of 0.5 to 200 μm, (ii) the total pore volume of the micropores and mesopores measured by gas adsorption is in the range of 0.4 to 2.2 cm 3 / g, (iii) the PD 50 pore diameter measured by gas adsorption is 30 nm or less, (b) combining the charge of the porous particles with the 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 / L RV per liter of the reactor volume (cm 3 ), preferably having a volume of at least 200 cm 3 / L RV per liter of the reactor volume (cm 3 ), and the charge of the silicon-containing precursor contains at least 2 g of silicon per liter of the reactor volume (cm 3 / L RV ), (c) A step of heating the reactor to a temperature effective in causing the deposition of silicon into the pores of the porous particles, thereby providing the silicon-containing composite particles, Includes.

[0019] In a preferred embodiment of the process according to the first aspect of the present invention, steps a) to c), particularly steps b) to c), are the following process phases 1 to 7: Phase 1: Filling the batch-type pressure reactor with one or more porous particles. Phase 2: Fill the batch-type pressure reactor with one or more silicon-containing precursors. Phase 3: Heat the batch pressure reactor to a target temperature and initiate the decomposition of one or more silicon-containing precursors within the batch pressure reactor at this temperature. Phase 4: Decompose the silicon-containing precursor and deposit silicon within the pores of the porous particles and optionally on the surface of the porous particles, thereby providing the silicon-containing composite particles. Phase 5: Cooling the batch pressure reactor. Phase 6: Removing the gaseous reaction products formed during the deposition process from the batch-type pressure reactor. Phase 7: Removing the silicon-containing composite particles from the batch pressure reactor. It was divided into, During Phase 4, the pressure inside the batch pressure reactor rises to at least 7 bar.

[0020] A method for producing silicon-containing composite particles by thermal decomposition of 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 on the surface of the porous particles, and the method comprises at least the following phases 1 to 7: Phase 1: Filling a batch-type pressure reactor with one or more porous particles, wherein the charge of porous particles is such that the reactor volume (cm³) 3 / L RV ) At least 20 cm per liter 3It has a volume of preferably a reactor volume (cm³). 3 / L RV ) at least 200 cm³ per liter 3 The porous particles have a volume and include micropores and / or mesopores. (i) D of the porous particles 50 The particle size is within the range of 0.5 to 200 μm. (ii) The total pore volume of micropores and mesopores measured by gas adsorption is 0.4 to 2.2 cm³. 3 It is within the range of / g (iii) PD measured by gas adsorption 50 The pore size must be 30 nm or less. Phase 2: Filling the batch pressure reactor with one or more silicon-containing precursors, wherein the silicon-containing precursor charge is such that the reactor volume (g / L) RV ) Contains at least 2g of silicon per liter. Phase 3: Heat the batch pressure reactor to a target temperature and initiate the decomposition of one or more silicon-containing precursors within the batch pressure reactor at this temperature. Phase 4: Decompose the silicon-containing precursor and deposit silicon within the pores of the porous particles and optionally on the surface of the porous particles, thereby providing the silicon-containing composite particles. Phase 5: Cooling the batch pressure reactor. Phase 6: Removing the gaseous reaction products formed during the deposition process from the batch-type pressure reactor. Phase 7: Removing the silicon-containing composite particles from the batch pressure reactor. It was divided into, A preferred manufacturing method is one in which the pressure in the batch pressure reactor rises to at least 7 bar during Phase 4.

[0021] In a further embodiment, the present invention relates to a method for producing silicon-containing composite particles by thermal decomposition of one or more silicon-containing precursors in the presence of one or more porous particles, wherein the silicon is deposited in the pores of the porous particles, preferably in the pores and on the surface of the porous particles, and the method comprises at least the following phases 1 to 7: Phase 1: Filling the batch-type pressure reactor with one or more porous particles. Phase 2: Fill the batch-type pressure reactor with one or more silicon-containing precursors. Phase 3: Heat the batch pressure reactor to a target temperature and initiate the decomposition of one or more silicon-containing precursors within the batch pressure reactor at this temperature. Phase 4: Decompose the silicon-containing precursor and deposit silicon in the pores of the porous particles, preferably in the pores and on the surface of the porous particles. Phase 5: Cooling the batch pressure reactor. Phase 6: Removing the gaseous reaction products formed during the deposition process from the batch-type pressure reactor. Phase 7: Removing the silicon-containing composite particles from the batch pressure reactor. Includes, During Phase 4, the pressure inside the batch pressure reactor rises to at least 7 bar.

[0022] A preferred method for producing silicon-containing composite particles is by thermal decomposition of 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, and the method comprises at least the following phases 1 to 7: Phase 1: Filling a batch-type pressure reactor with one or more porous particles, wherein the charge of porous particles is such that the reactor volume (cm³) 3 / L RV ) At least 20 cm per liter 3 It has a volume of preferably a reactor volume (cm³). 3 / L RV ) at least 200 cm³ per liter 3The porous particles have a volume and include micropores and / or mesopores. (i) D of the porous particles 50 The particle size is within the range of 0.5 to 200 μm. (ii) The total pore volume of micropores and mesopores measured by gas adsorption is 0.4 to 2.2 cm³. 3 It is within the range of / g (iii) PD measured by gas adsorption 50 The pore size must be 30 nm or less. Phase 2: Filling the batch pressure reactor with one or more silicon-containing precursors, wherein the silicon-containing precursor charge is such that the reactor volume (g / L) RV ) Contains at least 2g of silicon per liter. Phase 3: Heat the batch pressure reactor to a target temperature and initiate the decomposition of one or more silicon-containing precursors within the batch pressure reactor at this temperature. Phase 4: Decompose the silicon-containing precursor and deposit silicon in the pores of the porous particles, preferably in the pores and on the surface of the porous particles. Phase 5: Cooling the batch pressure reactor. Phase 6: Removing the gaseous reaction products formed during the deposition process from the batch-type pressure reactor. Phase 7: Removing the silicon-containing composite particles from the batch pressure reactor. It was divided into, During Phase 4, the pressure inside the batch pressure reactor rises to at least 7 bar.

[0023] For the sake of clarity, however, the preferred and alternative embodiments described below refer to each of the above-described aspects of the present invention and each of the above-described preferred processes of the present invention.

[0024] Therefore, the present invention relates, in general terms, to a method for producing a composite particle material in which nanoscale silicon domains are deposited in a pore network of porous particles. Thus, the porous particles form a framework containing nanoscale silicon domains. As used herein, the term “nanoscale silicon domain” refers to a nanoscale body of silicon having dimensions determined by the position of silicon within the micropores and / or mesopores of the porous particles.

[0025] The method of the present invention differs from conventional methodologies in that silicon deposition is carried out in batch mode for both porous particles and silicon-containing precursors. In addition, the respective charges of porous particles and silicon-containing precursors per liter of reactor volume mean that silicon deposition is carried out at a spontaneous pressure above atmospheric pressure, and may be at least one or two orders of magnitude higher than atmospheric pressure.

[0026] The method of the present invention is particularly associated with many advantages due to the charging of silicon-containing precursors in batch-type pressure reactors and the parameters according to the present invention. These advantageous effects can be synergistically further enhanced by preferred pressure means.

[0027] Firstly, the silicon-containing precursor can be distributed throughout the entire volume of the reactor. Therefore, the reaction can be carried out at any point in the reactor, especially up to the same conversion level, unless there is a temperature profile. Heterogeneous product composition due to contact between the solid and the gas flow is avoided, and the material can have the same properties regardless of its position in the reactor. The batch composition will preferably be homogeneous.

[0028] Secondly, silicon-containing precursors can be distributed through the porous system of porous particles before the reaction occurs. Therefore, since silicon-containing precursors are already present in the pores at the start of the reaction, the limitations on mass transfer can be reduced. Furthermore, batch reactors can be charged with a large number of porous particles to reduce or eliminate the headspace within the reactor, so that silicon-containing precursor molecules present in the remaining reactor volume outside the pore volume of the porous particles (e.g., the gaps) have only a short mean free path to the nearest particle.

[0029] Thirdly, the higher the pressure, the greater the amount of silane that can be supplied to the reactor in a single batch. Silane is in a supercritical state at pressures above 47.8 atmospheres, and under these conditions, it has a compressibility factor, allowing for the introduction of highly packed silicon into a single batch at room temperature.

[0030] Surprisingly, the batch process allows for the production of silicon-containing composite particles in a shorter reaction time and therefore in a more efficient manner. This method, remarkably, enables the decomposition of an increased amount of silicon-containing precursor, particularly within the porous particles, and therefore allows for a correspondingly increased amount of deposited silicon 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, as it is known from methods for producing polycrystalline silicon that silicon deposition at relatively high pressures is accompanied by the formation of increased unwanted dust (JOOdden et al., Solar Energy Mat. & Solar Cells 2005, 86, 165), which is unproductive for both silicon deposition on the inner surface of the pores and the outer surface of the porous particles, and for the yield of composite particles. Surprisingly, this harmful effect is resolved by the method of the present invention. These effects are particularly pronounced at the said pressure, especially at least 7 bar.

[0031] Fourth, the temperature is generally raised to the deposition temperature only after the silicon-containing precursor has been packed into the reactor under pressure. This also introduces a new method for controlling the reaction rate and the composition of the product. Higher silicon hydride deposition can be carried out at lower temperatures because the system does not need to deal with mass transfer limitations. Thus, compared to the atmospheric pressure synthesis route, it is possible to obtain product composite particles with a lower surface area and higher silicon hydride terminals.

[0032] The method of the present invention for producing silicon-containing composite particles offers various advantages compared to the prior art. In particular, it has the advantage of enabling the complete conversion of the silicon precursor in a short reaction time. These advantages are preferably further enhanced by a pressure increase in the batch pressure reactor during step (c) or phase 4, which is not caused by, or not caused by, a temperature increase.

[0033] Another advantage is that the amount of inert gas can be reduced or even completely avoided, which similarly results in a higher space / time yield and therefore allows for more rapid and uniform deposition of silicon within or on porous particles.

[0034] Furthermore, it is possible to prevent the continuous recycling and treatment of reactor off-gas, which is normally generated during the operation of open-type reactors.

[0035] Furthermore, by using a batch-type pressure reactor, multiple depositions from the same reactant, such as silicon-containing precursors, can be carried out very easily, with precisely controllable amounts of deposited products based on the reactants in each deposition step.

[0036] Therefore, silicon-containing composite particles obtained by the method of the present invention are preferably distinguished by the favorable homogeneity of the deposited layer.

[0037] Furthermore, a particular advantage is that the often-described dust generation can be avoided. This can be achieved, for example, by the large surface area of ​​the porous particles made available for silicon deposition from the silicon-containing precursor, and by the vigorous penetration of the porous particles with the silicon-containing precursor. At the same time, this method yields a high yield of deposited silicon.

[0038] Furthermore, this method, which starts with porous particles and a silicon precursor, can be implemented relatively easily.

[0039] As a result of the advantages of the method of the present invention, silicon-containing composite particles can be obtained advantageously, quickly, and economically for use as an active material for the negative electrode of lithium-ion batteries, particularly for their excellent properties.

[0040] Remarkably, the silicon-containing composite particles produced according to this method have a high storage capacity for lithium ions, which enables remarkably high cycle stability when used as an active material for the negative electrode of lithium-ion batteries. These silicon-containing composite particles exhibit advantageously low volume changes during cycling.

[0041] Silicon-containing composite particles can be obtained by the present invention, which have improved properties for use in lithium-ion batteries with high volumetric energy capacity. The silicon-containing material obtained by the present invention is permeable to lithium ions and electrons, thus enabling charge transport. Furthermore, the amount of decomposition electrolyte solvent and the formation of solid electrolyte interfaces ("SEI") can be reduced by the means of the present invention. Excessive SEI is known to negatively affect the cycle efficiency of lithium-ion batteries.

[0042] To avoid misunderstanding, the term "particle diameter" as used herein refers to the equivalent spherical diameter (ESD), i.e., the diameter of a sphere having the same volume as a given particle, where the particle volume is understood to include the volume of any pores within the particle. 50 " and "D 50"Particle diameter" refers to the volume-based median particle diameter, i.e., the diameter below which 50% of the volume of the particle population is found. The term "D" as used herein refers to the volume-based median particle diameter. 10 " and "D 10 "Particle diameter" refers to the median particle diameter on a 10% volume basis, i.e., the diameter below which 10% of the volume of the particle ensemble is found. The term "D" as used herein is defined as "D 90 " and "D 90 "Particle diameter" refers to the median particle diameter based on 90% volume, i.e., the diameter below which 90% of the particle population's volume is found.

[0043] Particle size and particle size distribution can be determined by standard laser diffraction methods in accordance with ISO 13320:2009. Laser diffraction relies on the principle that particles scatter light at angles that vary with particle size, and that aggregates of particles generate a pattern of scattered light defined by intensity and angle, which can correlate to the particle size distribution. Many laser diffraction devices are commercially available, enabling rapid and reliable measurement of particle size distribution. Unless otherwise specified, particle size distribution measurements specified or reported herein were performed using the conventional Malvern Mastersizer® 3000 particle size analyzer from Malvern Instruments®. The Malvern Mastersizer® 3000 particle size analyzer operates by projecting helium-neon gas laser light onto a transparent cell containing the target particles suspended in an aqueous solution. The light beam striking the particles is scattered at angles inversely proportional to the particle size, and a photodetector array measures the intensity of the light at several predetermined angles. The intensities measured at different angles are processed by a computer using standard theoretical principles to determine the particle size distribution. The laser diffraction values ​​reported herein are obtained using a wet dispersion of particles in 2-propanol with 5 vol% of the surfactant SPAN®-40 (sorbitan monopalmitate). The refractive index of the particles is assumed to be 2.68 for porous particles and 3.50 for composite particles, and the index of the dispersion medium is assumed to be 1.378. The particle size distribution is calculated using the Mie scattering model.

[0044] Alternatively, particle size and particle size distribution can be determined according to ISO 13320 by static laser scattering using the Mie model and the Horiba LA 950 detector, preferably using ethanol as the particle dispersion medium.

[0045] Generally, porous particles are D in the range of 0.5 to 200 μm. 50 It has a particle size. Optionally, the D of porous particles. 50 The particle size may 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 porous particles 50 The particle size may be 150 μm or less, or 100 μm or less, or 70 μm or less, or 50 μm or less, or 40 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less, or 18 μm or less, or 15 μm or more, or 12 μm or more, or 10 μm or less.

[0046] For example, porous particles are within the range of 0.5-150 μm, or 0.5-100 μm, or 0.5-50 μm, or 0.5-30 μm, or 1-25 μm, or 1-20 μm, or 2-25 μm, or 2-20 μm, or 2-18 μm, or 3-20 μm, or 3-18 μm, or 3-15 μm, or 4-18 μm, or 4-15 μm, or 4-12 μm, or 5-15 μm, or 5-12 μm, or 5-10 μm. 50 Particles may have a particle size. Particles within these size ranges and having the porosity and pore size distribution defined herein are ideally suited for the production of composite particles for use in negative electrodes for metal-ion batteries by the CVI process.

[0047] 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. 10By maintaining a particle size of 0.2 μm or larger, the possibility of undesirable aggregation of submicron-sized particles is reduced, and the dispersibility of the resulting composite particles is improved. 10 The particle size is preferably ≤10 μm, more preferably ≤5 μm, and most preferably ≤3 μm.

[0048] D of porous particles 90 The particle size is preferably 300 μm or less, or 250 μm or less, or 200 μm or less, or 150 μm or less, or 100 μm or less, or 80 μm or less, or 60 μm or less, or 40 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less, more preferably 18 μm or less, even more preferably 15 μm or less, and most preferably 13 μm or less. 90 The particle size is preferably 4 μm or larger, and more preferably 8 μm or larger.

[0049] The volume-weighted particle size distribution of porous particles is preferably diameter percentage d 10 ≥0.2μm~d 90 ≤20.0μm, more futurized 10 ≥0.4μm~d 90 ≤15.0 μm, and most preferably d 10 The range is ≥0.6μm ~ d90 ≤ 12.0μm.

[0050] Porous particles preferably have a narrow particle size distribution range. For example, a particle size distribution range ((D 90 -D 10 ) / D 50 The particle size distribution (as defined) is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. By keeping the particle size distribution range narrow, efficient particle filling into a dense powder bed can be achieved more easily.

[0051] The volume-weighted particle size distribution of porous particles is d 90 Value and d 10 Difference in values ​​(D 90 -D 10The difference is preferably ≤15.0 μm, more preferably ≤12.0 μm, very preferably ≤10.0 μm, particularly preferably ≤8.0 μm, and most preferably ≤4.0 μm. The volume-weighted particle size distribution of the porous particles is preferably ≥0.6 μm, more preferably ≥0.8 μm, and most preferably ≥1.0 μm. 90 -d 10 It contains the difference.

[0052] Porous particles preferably exist in the form of isolated particles or aggregates. Porous particles are preferably not aggregated and preferably not in aggregates. Aggregation generally means that, during the manufacturing process of porous particles, primary particles are initially formed, undergo fusion, and / or the primary particles bond to each other, for example, via covalent bonds, thus forming aggregates. Primary particles are generally isolated particles. Aggregates or isolated particles can form aggregates. Aggregates are loose associations of aggregates or primary particles, which are linked to each other, for example, via van der Waals interactions or hydrogen bonds. Aggregates can be easily returned to aggregates by conventional kneading and dispersion techniques. Aggregates cannot be broken down into primary particles by these techniques, or can only be broken down partially. The presence of porous particles in the form of aggregates, aggregates, or isolated particles can be visualized, for example, by conventional scanning electron microscopy (SEM). Static light scattering methods for determining the particle size distribution or particle size of matrix particles, in contrast, cannot distinguish between aggregates and aggregates.

[0053] The porous particles may have any desired shape, and therefore may be, for example, plate-like, irregular, fragment-like, spherical, or other needle-like, with fragment-like or spherical particles being preferred.

[0054] 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 thought to help with deposition uniformity and promote denser packing in both batch pressure reactors and the final product incorporated into electrodes.

[0055] High-precision two-dimensional projections of micron-scale particles can be obtained using scanning electron microscopy (SEM) or dynamic image analysis, which records the shadows projected by particles using a digital camera. The term "sphericity" as used herein is understood to mean the ratio of the area of ​​the particle projection (obtained from such imaging techniques) to the area of ​​a circle, where the particle projection and the circle have the same circumference. Therefore, for individual particles, the sphericity S can be defined as follows:

number

number

[0056] Porous particles consist of a three-dimensionally interconnected network of pores comprising micropores and / or mesopores and optionally trace amounts of macropores. According to conventional IUPAC terminology, the term "micropore" is used herein to refer to pores with a diameter of less than 2 nm, the term "mesopore" is used herein to refer to pores with a diameter of 2 to 50 nm, and the term "macropore" is used herein to refer to pores with a diameter greater than 50 nm.

[0057] In this specification, references to the volumes of micropores, mesopores, and macropores within porous particles, and references to the distribution of pore volumes within porous particles, relate to the internal pore volumes of porous particles used as starting materials in step (a) of the prescribed method, i.e., before silicon is deposited into the pore volumes in step (c).

[0058] Porous particles are 0.4-2.2 cm 3 It is characterized by the total volume of micropores and mesopores within the range of / g (i.e., the total pore volume within the range of 0 to 50 nm). Typically, porous particles contain both micropores and mesopores. However, this does not preclude the use of porous particles that contain micropores but not mesopores, or porous particles that contain mesopores but not micropores.

[0059] More preferably, the total volume of micropores and mesopores in the porous particles is at least 0.45 cm³. 3 / g, or at least 0.5cm 3 / g, at least 0.55cm 3 / g, or at least 0.6cm 3 / g, or at least 0.65cm 3 / g, or at least 0.7cm 3 / g, or at least 0.75cm 3 / g, or at least 0.8cm 3 / g, at least 0.85cm 3 / g, or at least 0.9cm 3 / g, or at least 0.95cm 3 / g, or at least 1cm 3 The value is / g. The use of highly porous particles may be advantageous because it allows for the inclusion of a larger amount of silicon within the pore structure.

[0060] The internal pore volume of the porous particles is preferably set with an upper limit at a value where the advantage of the increase in the pore volume for accommodating a larger amount of silicon outweighs the increase in the fragility of the porous particles. Preferably, the total volume of micropores and mesopores in the porous particles is 2 cm 3 / g or less, or 1.8 cm 3 / g or less, or 1.6 cm 3 / g or less, or 1.5 cm 3 / g or less, or 1.45 cm 3 / g or less, or 1.4 cm 3 / g or more, or 1.35 cm 3 / g or more, or 1.3 cm 3 / g or more, or 1.25 cm 3 / g or more or 1.2 cm 3 / g or more.

[0061] In some examples, the total volume of micropores and mesopores in the porous particles is 0.45 - 2.2 cm 3 / g, or 0.5 - 2 cm 3 / g, or 0.55 - 2 cm 3 / g, or 0.6 - 1.8 cm 3 / g, or 0.65 - 1.8 cm 3 / g, or 0.7 - 1.6 cm 3 / g, or 0.75 - 1.6 cm 3 / g, or 0.8 - 1.5 cm 3 / g.

[0062] In other examples, the total volume of micropores and mesopores in the porous particles is 0.4 - 0.75 cm 3 / g, or 0.4 - 0.7 cm 3 / g, or 0.4 - 0.65 cm 3 / g, 0.45 - 0.75 cm 3 / g, or 0.45 - 0.7 cm 3 / g, or 0.45 - 0.65 cm 3 / g, or 0.45 - 0.6 cm 3 / g.

[0063] In other examples, the total volume of micropores and mesopores in porous particles is 0.6–2 cm³. 3 / g, or 0.6-1.8cm 3 / g, or 0.7-1.8cm 3 / g, or 0.7-1.6cm 3 / g, or 0.8-1.6cm 3 / g, or 0.8-1.5cm 3 / g, or 0.8-1.4cm 3 / g, or 0.9-1.5cm 3 / g, or 1-1.4cm 3 It may be within the range of / g.

[0064] PD of porous particles 50 The pore size is preferably 30 nm or less, and optionally 25 nm or less, 20 nm or less, 15 nm or less, 12 nm or less, 10 nm or less, 8 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, 3 nm or less, 2.5 nm or more, 2 nm or more, or 1.5 nm or less. 50 The term "pore diameter" refers to the volume-based median pore diameter (i.e., pore diameters less than or equal to the pore diameter in which 50% of the total volume of micropores and mesopores reside), based on the total volume of micropores and mesopores. Therefore, according to the present invention, at least 50% of the total volume of micropores and mesopores are in the form of pores having a diameter of less than 30 nm, preferably.

[0065] To avoid any doubt, all macropore volumes (pore diameters greater than 50 nm) are PD 50 It is not considered for the purpose of determining the value.

[0066] In principle, the volume ratio of micropores to mesopores in porous particles may 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.

[0067] The pore size distribution of porous particles may be unimodal, bimodal, or multimodal. As used herein, the term “pore size distribution” refers to the distribution of pore sizes of porous particles relative to the cumulative total internal pore volume. Bimodal or multimodal pore size distributions are considered preferable because the proximity between micropores and larger diameter pores provides the advantage of efficient ion transport to silicon through the porous network.

[0068] The total volume of micropores and mesopores and the pore size distribution of micropores and mesopores were determined using the rapid solid density functional theory (QSDFT) according to the standard methodology specified in ISO 15901-2 and ISO 15901-3, with a relative pressure p / p0 of 10 at 77 K. -6 Pore ​​volume and pore size distribution are determined either by nitrogen gas adsorption until a certain point is reached, or by using classical adsorption models such as the Horvath-Kawazoe model for micropores according to DIN66135 and the BJH model for mesopores according to DIN66134. Nitrogen gas adsorption is a method for evaluating the porosity and pore size distribution of a material by condensing gas in the pores of a solid. As the pressure increases, the gas first condenses in the smallest diameter pores, and the pressure rises until it reaches a saturation point where all pores are filled with liquid. Then, the pressure of the nitrogen gas is gradually reduced, and the liquid evaporates out of the system. By analyzing the adsorption-desorption isotherms and the hysteresis between them, the pore volume and pore size distribution can be determined. Suitable instruments for measuring pore volume and pore size distribution by nitrogen gas 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.

[0069] Nitrogen gas adsorption is effective for measuring pore volume and pore size distribution of pores with diameters up to 50 nm, but is unreliable for pores with much larger diameters. Therefore, for the purposes of this invention, nitrogen adsorption is used to determine pore volume and pore size distribution only for pores with diameters up to 50 nm (i.e., only for micropores and mesopores). PD 50 Similarly, this is determined based only on the total volume of micropores and mesopores.

[0070] Given the limitations of available analytical techniques, it is impossible to measure pore volume and pore size distribution across the entire range of micropores, mesopores, and macropores using a single technique. If porous particles contain macropores, the volume of pores with diameters in the range of over 50 nm and up to 100 nm can be measured by mercury porosimetry, preferably 0.3 cm². 3 Less than / g, or 0.20cm 3 Less than / g, or 0.1cm 3 Less than / g, or 0.05cm 3 The value is less than / g. While a small number of macropores are useful for facilitating electrolyte access to the pore network, the advantages of the present invention are substantially obtained by accommodating silicon in micropores and even smaller mesopores.

[0071] Pore ​​volumes measured by mercury porosimetry for pore diameters of 50 nm or less are all ignored (as mentioned above, nitrogen adsorption is used to characterize mesopores and micropores). Pore volumes measured by mercury porosimetry for pore diameters greater than 100 nm are assumed to be interparticle porosity and are also ignored for the purposes of this invention.

[0072] Mercury porosimetry is a technique for characterizing the porosity and pore size distribution of a material by applying various levels of pressure to a sample immersed in mercury. The pressure required for mercury to penetrate the pores of the sample is inversely proportional to the pore size. The values ​​obtained by mercury porosimetry reported herein are obtained according to ASTM UOP578-11, with a surface tension γ of 480 mN / m and a contact angle φ of 140° for mercury at room temperature. The density of mercury is 13.5462 g / cm³ at room temperature. 3 It is said that... Many high-precision mercury porosimeters are commercially available, such as the AutoPore IV series automatic mercury porosimeters from Micromeritics, Inc. in the United States. For more information on mercury porosimetry, see "Analytical Methods in Fine Particle Technology, 1997, Micromeritics Instrument Corporation, ISBN 0-9656783-0" by PA Webb and C. Orr.

[0073] It will be understood that penetration techniques such as gas adsorption and mercury porosimetry are only effective for determining the pore volume of pores that are accessible to nitrogen or mercury from outside the porous particle. The porosity values ​​defined herein are understood to refer to the volume of open pores, i.e., pores that are accessible to fluid from outside the porous particle. Completely sealed pores that cannot be identified by nitrogen adsorption or mercury porosimetry are not considered when determining the porosity values ​​herein. Similarly, pore volumes present in pores so small that they are below the detection limit by nitrogen adsorption are not considered.

[0074] The porous particles are preferably ≥0.2 cm 3 / g, more preferably ≥0.6cm 3 / g, most preferably ≥1.0cm 3 It has a pore volume that allows Gurwich gas to penetrate at a rate of / g. This is useful for obtaining high-capacity lithium-ion batteries. The pore volume that allows Gurwich gas to penetrate was determined by gas absorption measurement with nitrogen in accordance with DIN66134.

[0075] Preferred porous particles are 0.3 cm 3 Less than 0.15 cm / g, more preferably 0.15 cm 3 It has a pore volume that is impervious to gas ingress of less than / g. Even in this way, it is possible to increase the capacity of lithium-ion secondary batteries. The pore volume that is impervious to gas ingress can be calculated using the following formula. Pore ​​volume that cannot be penetrated by gas = 1 / density of pure matter - 1 / skeleton density

[0076] The term "pure substance density" here refers to the theoretical density of porous particles based on their phase composition, or the density of the pure substance (the density of a material without closed pores). Those skilled in the art can find pure substance density data, for example, at the Ceramic Data Portal of the National Institute of Standards and Technology (NIST, https: / / srdata.nist.gov / CeramicDataPortal / scd). For example, the pure substance density of carbon is 2.2-2.3 g / m³. 3 The pure substance density of silicon dioxide is 2.203 g / cm³. 3 The pure substance density of boron nitride is 2.25 g / cm³. 3 The pure substance density of silicon nitride is 3.44 g / cm³. 3 The pure substance density of silicon carbide is 3.21 g / cm³. 3 The skeletal density is the actual density (gas-penetrating) of porous particles determined by helium pycnometry.

[0077] The porous particles are preferably based on one or more materials selected from the group consisting of hard carbon, soft carbon, mesocarbon, amorphous carbon in the form of microbeads, natural or synthetic graphite, single-walled and multi-walled carbon nanotubes and graphene; oxides such as silicon dioxide, aluminum oxide, mixed silicon-aluminum oxide, titanium oxide, 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.

[0078] Examples of ceramic materials include the following component formula: Al a B b C c Mg d N e O f Si g It is described as such that 0 ≤ a, b, c, d, e, f, g ≤ 1, at least two coefficients a ~ g > 0, and a × 3 + b × 3 + c × 4 + d × 2 + g × 4 ≥ e × 3 + f × 2.

[0079] The ceramic material may be, for example, a compound of two, three, four, five, six, or seven elements. A preferred ceramic material has the following component formula: Non-stoichiometric boron nitride (BN) z (In the formula, z=0.2~1) Non-stoichiometric carbonitrides CN z (In the formula, z=0.1~4 / 3) Boron Carbonitride B x CN z (In the formula, x=0.1~20, z=0.1~20, x×3+4≧z×3) Boron nitride oxide BN z O r (In the formula, z=0.1~1, r=0.1~1, 3≧r×2+z×3) Boron Carbonitride B x CN z O r (In the formula, x=0.1~2, z=0.1~1, r=0.1~1, x×3+4≧r×2+z×3) Silicon carbide (Si) x CO z (In the formula, x=0.1~2, z=0.1~2, x×4+4≧z×2) Silicon carbide nitride (Si) x CN z (In the formula, x=0.1~3, z=0.1~4, x×4+4≧z×3) Silicon boronite carbonitride (Si) w B x CN z (In the formula, w=0.1~3, x=0.1~2, z=0.1~4, w×4+x×3+4≧z×3) Silicon boronate carbide (Si) w Bx CO z (In the equation, w = 0.10~3, x = 0.1~2, z = 0.1~4, and w × 4 + x × 3 + 4 ≥ z × 2) Silicon boron carbon oxide Si v B w CN x O z (In the formula, v=0.1~3, w=0.1~2, x=0.1~4, z=0.1~3, v×4+w×3+4≧x×3+z×2) Aluminum boron silicon carbon oxide Al u B v Si x CN w O z (In the formula, u=0.1~2, v=0.1~2, w=0.1~4, x=0.1~2, z=0.1~3, u×3+v×3+x×4+4≧w×3+z×2)

[0080] An example of porous metal oxide particles is the formula TiO x It is a titanium oxide having a value greater than 1 and less than 2.

[0081] 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.

[0082] The porous particles are more preferably porous conductive particles, and most preferably porous carbon particles.

[0083] Porous carbon particles may be based on materials selected from the group consisting of amorphous carbon, natural or synthetic graphite, carbon nanotubes such as single-walled and multi-walled carbon nanotubes, and graphene. Amorphous carbon may be in the form of hard carbon, soft carbon, or mesocarbon microbeads. Carbon may be crystalline carbon, amorphous carbon, or a mixture of amorphous and crystalline carbon. Porous carbon particles may be either hard carbon particles or soft carbon particles.

[0084] The porous carbon particles preferably contain at least 80% by weight of carbon, more preferably at least 90% by weight of carbon, more preferably at least 95% by weight of carbon, and optionally at least 98% by weight or at least 99% by weight of carbon.

[0085] As used herein, the term “hard carbon” generally refers to carbon atoms in nanoscale polyaromatic domains with sp² 2 This refers to the disordered carbon matrix mainly found in hybridized states (triple bonds). Polyaromatic domains are generally cross-linked by 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 a large G-band (~1600 cm⁻¹) in its Raman spectrum. -1 As can be seen from the presence of ), it generally has properties similar to graphite. However, the large D band (~1350 cm) in the Raman spectrum... -1 As can be seen from this, carbon is generally not in a perfect graphite state.

[0086] As used herein, the term "soft carbon" generally refers to polyaromatic domains in which carbon atoms have dimensions in the range of 5 to 200 nm and are sp 2 This refers to the disordered carbon matrix mainly found in hybridized states (triple bonds). In contrast to hard carbon, polyaromatic domains in soft carbon are generally bonded by intermolecular forces but not cross-linked by chemical bonds. This means that it graphitizes at high temperatures. Porous carbon particles preferably have at least 50% sp, as measured by XPS. 2 It contains hybridized carbon. For example, porous carbon particles preferably have 50% to 98% sp 2 Hybrid carbon, 55%~95% sp 2 Hybrid carbon, 60%~90% sp 2 Hybrid carbon, or 70-85% sp 2 It contains hybrid carbon.

[0087] Various different materials can be used to manufacture a suitable porous carbon skeleton. Examples of organic materials that can be used include plant biomass, including lignocellulosic materials (such as coconut shells, rice husks, and wood), and fossil carbon sources such as coal. Examples of resins and polymer materials that form porous carbon particles by thermal decomposition include phenolic resins, novolac resins, pitch, melamine, polyacrylate, polystyrene, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP); and various copolymers consisting of monomer units of acrylate, styrene, α-olefin, vinylpyrrolidone, and other ethylenically unsaturated monomers. Depending on the starting materials and the conditions of the thermal decomposition process, a variety of different carbon materials are available in this art. Porous carbon particles of various different specifications are available from suppliers.

[0088] Porous carbon particles can be subjected to chemical or gaseous activation treatments to increase the volume of mesopores and micropores. A suitable activation treatment includes, for example, contacting thermally decomposed carbon with one or more of oxygen, vapor, CO, CO2, or KOH at a temperature in the range of 600 to 1000°C.

[0089] Porous particles are preferably open pores. Open pores generally mean that the pores are connected to the particle surface, for example, via channels, which is preferably possible for mass transfer with the surroundings, particularly for the transfer of gaseous compounds. This can be confirmed using gas absorption spectroscopy (evaluation by Brunauer, Emmett, and Teller, "BET"), i.e., measurement of specific surface area.

[0090] The porous particles preferably have a minimum size of 50m 2 / g, or at least 750m 2 / g, or at least 1,000m 2 / g, or at least 1,250m 2 / g, or at least 1,500m 2It has a BET surface area of ​​4,000 m² / g. The term "BET surface area" as used herein 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 using the Brunauer-Emmett-Teller theory, in accordance with ISO 9277. Preferably, the BET specific surface area of ​​porous particles is 4,000 m² / g. 2 / g or less, or 3,500m 2 Less than / g, or 3,250m 2 / g or less, or 3,000m 2 It is less than / g. For example, porous particles are 750m 2 / g~4,000m 2 / g, or 1,000m 2 / g~3,500m 2 / g, or 1,250m 2 / g~3,250m 2 / g, or 1,500m 2 / g~3,000m 2 The BET surface area may be within the range of / g.

[0091] The porous particles are preferably 0.1 to 7 g / cm³, as determined by helium pycnometry. 3 More preferably 0.3 to 3 g / cm³ 3 It has a skeletal density. This is advantageous for increasing the weight capacity (mAh / g) of lithium-ion batteries.

[0092] The porous particles are preferably at least 0.35, preferably 3 g / cm³ 3 Less than 2 g / cm³, more preferably 2 g / cm³ 3 Less than 1.5 g / cm³, more preferably 1.5 g / cm³ 3 Less than 0.35 to 1.2 g / cm³ 3 It has a particle density of . As used herein, the term “particle density” means “apparent particle density” as measured by mercury porosimetry (i.e., the mass of the particles divided by the volume of the particles, where the volume of the particles is considered to be the sum of the solid material and any closed or blind holes (“blind holes” being holes too small to be measured by mercury porosimetry)).

[0093] Preferably, the porous particles contain at least 0.4 g / cm³ 3 , or at least 0.45 g / cm³ 3 , or at least 0.5 g / cm³ 3 , or at least 0.55 g / cm³ 3 , or at least 0.6 g / cm³ 3 , or at least 0.65 g / cm³ 3 , or at least 0.7 g / cm³ 3 The particle density is measured by mercury porosimetry. Preferably, the porous particles have a density of 1.15 g / cm³. 3 The following, or 1.1 g / cm³ 3 The following, or 1.05 g / cm³ 3 The following, or 1 g / cm³ 3 The following, or 0.95 g / cm³ 3 The following, or 0.9 g / cm³ 3 It has a particle density measured by mercury porosimetry.

[0094] For clarification, it should be noted that porous particles are generally different from silicon-containing composite particles. Porous particles serve as starting materials for manufacturing silicon-containing composite particles. Generally, silicon located within the pores of porous particles and on the surface of porous particles, more specifically silicon obtained by the deposition of silicon precursors, is preferably absent.

[0095] The silicon-containing precursor is preferably a silicon-containing liquid or gas under standard conditions (100 kPa and 20°C). Preferably, the silicon-containing precursor is a silicon-containing gas under standard conditions.

[0096] Silicon-containing precursors generally form silicon under heat treatment. Preferably, silicon-containing precursors are selected from the group consisting of silicon-hydrogen compounds, chlorine-containing silanes, and alkylsilanes.

[0097] Examples of silicon-hydrogen compounds include monosilane (SiH4), disilane (Si2H6), trisilane (Si3H8), and their linear, branched, or cyclic higher-order congeners, such as neopentasilane (Si5H). 12 Cyclohexasilane Si6H 12 Examples of chlorine-containing silanes are trichlorosilane HSiCl3, dichlorosilane H2SiCl2, chlorosilane H3SiCl, tetrachlorosilane SiCl4, hexachlorodisilane Si2Cl6, and linear, branched, or cyclic higher-order homologues, e.g., 1,1,2,2-tetrachlorodisilane Cl2HSi-SiHCl2, chlorinated or partially chlorinated oligosilanes or polysilanes, methylchlorosilanes, e.g., trichloromethylsilane MeSiCl3, dichlorodimethylsilane Me2SiCl2, chlorotrimethylsilane Me3SiCl, tetramethylsilane Me4Si, dichloromethylsilane MeHSiCl2, chloromethylsilane MeH2SiCl, and chlorodimethylsilane MeH2SiCl. Examples of alkylsilanes are methylsilane MeH3Si, dimethylsilane Me2H2Si, and trimethylsilane Me3SiH.

[0098] A more preferred silicon-containing precursor is monosilane SiH4; general formula Si n H n+2 Linear silane (wherein n is an integer in the range of 2 to 10); general formula - [SiH2] n - A cyclic silane (wherein n is an integer in the range of 3 to 10); selected from the group consisting of trichlorosilane HSiCl3, dichlorosilane H2SiCl2, and chlorosilane H3SiCl. Particularly preferred silicon-containing precursors are silane (SiH4), disilane (Si2H6), trisilane (Si3H8), methylsilane, dimethylsilane, and chlorosilane. Even more preferred silicon-containing precursors are selected from the group consisting of SiH4, HSiCl3, and H2SiCl2. The most preferred is silane (SiH4).

[0099] The charge for the porous particles used in step (b) is preferably at least 30 cm 3 / L RV, or at least 40cm 3 / L RV , or at least 50cm 3 / L RV , or at least 75cm 3 / L RV , or at least 100cm 3 / L RV , or at least 150cm 3 / L RV , or at least 200cm 3 / L RV , more preferably at least 250 cm 3 / L RV , or at least 300cm 3 / L RV , or at least 400cm 3 / L RV , or at least 500cm 3 / L RV , or at least 600cm 3 / L RV , or at least 700cm 3 / L RV , or at least 800cm 3 / L RV , or at least 900cm 3 / L RV It has a volume of . Preferably, the charge of porous particles used in step (b) is at least 500 cm³ 3 / L RV In some embodiments, this is sufficient to substantially fill the reactor volume of an optional batch pressure reactor.

[0100] As used herein, the volume of porous particles refers to the equivalent mass of porous particles determined from the tap density. For example, 200 cm³ of porous particle material having a tap density of 1000 g / L as defined herein. 3 The particle volume is equivalent to 200g of porous particle material. Tap density is measured according to ISO 3953, using 12,000 taps as the standard.

[0101] The silicon-containing precursor charge used in step (b) must be at least 2 g / LRV 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 Contains silicon, or at least 40 g / L RV 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 It contains silicon.

[0102] Preferably, the silicon-containing precursor used in step (b) is a gas. The partial pressure of the silicon-containing precursor in the batch pressure reactor following 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.

[0103] Batch-type pressure reactors are preferably essentially oxygen-free after the addition of porous particles and silicon-containing precursor charges. Oxygen can be sufficiently removed from the reactor, for example, by evacuating the reactor volume and flushing with an inert gas or silicon-containing precursor gas, following standard procedures for reactions carried out in an oxygen-free atmosphere.

[0104] The batch pressure reactor may contain, in addition to the silicon-containing precursor, an inert padding gas, such as a noble gas like helium, neon, argon, krypton, or xenon, or nitrogen, carbon dioxide, or a foaming gas. Preferred inert gases include argon, and especially nitrogen.

[0105] The packing of the batch-type pressure reactor may include hydrogen gas, especially when the silicon-containing precursor is chlorosilane, and preferably the atomic ratio of hydrogen to chlorine is at least 1:1.

[0106] The batch pressure reactor may be further filled with one or more dopants. The dopants are based on compounds containing, for example, boron, nitrogen, phosphorus, arsenic, germanium, iron, or nickel. The dopants are preferably selected from the group consisting of ammonia (NH3), diborane (B2H6), phosphan (PH3), germane (GeH4), alsan (AsH3), and nickel tetracarbonyl (Ni(CO)4). The dopants may be filled into the batch pressure reactor, for example, in step (b) or in phase 1 or phase 2 of the present invention.

[0107] The batch pressure reactor further contains 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, cycloheptane; unsaturated hydrocarbons having 1 to 10 carbon atoms, such as ethene, acetylene, propene or butene, isoprene, butadiene, divinylbenzene, vinylacetylene, cyclohexadiene, cyclooctadiene; cyclic unsaturated hydrocarbons, such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, cyclohexadiene, cyclopentadiene, dicyclopentadiene or norbornadiene; aromatic hydrocarbons, such as benzene, toluene, p-, m- or o-xylene, styrene (vinylbenzene), ethylbenzene, diphenylmethane or naphthalene; and other aromatic hydrocarbons. For example, the mixture can be filled with one or more hydrocarbons selected from the group consisting of phenol, o-, m-, p-cresol, cymene, nitrobenzene, chlorobenzene, pyridine, anthracene or phenanthrene; myrcene, geraniol, thioterpineol, norbornane, borneol, isoborneol, bornane, camphor, limonene, terpinene, pinene, karane, phenol, aniline, anisole, furan, furfural, furfuryl alcohol, hydroxymethylfurfural, bishydroxymethylfuran and mixed fractions containing multiple compounds thereof, for example, from natural gas condensates, crude oil distillates or coke oven condensates, mixed fractions from product streams from fluid catalytic cracking (FCC), steam crackers or Fischer-Tropsch synthesis plants, or more commonly, hydrocarbon-containing material streams from the processing of wood, natural gas, crude oil and coal. The hydrocarbons may be filled into a batch pressure reactor, for example, in step (b) or in phase 1 or phase 2 of the method of the present invention.

[0108] Following step (b), the contents of the batch pressure reactor may preferably consist essentially of porous particles, a silicon precursor, and optionally an inert padding gas or hydrogen.

[0109] The mass ratio of porous particles to silicon in the silicon-containing precursor generally determines the silicon content of the composite particle product. Preferably, the mass ratio (on a silicon-equivalent basis) of porous particles to silicon precursor in step (b) is 95:5 to 40:60, resulting in composite particles having a theoretical silicon content of 5 to 60 wt%. For example, the mass ratio (on a silicon-equivalent basis) of porous particles to silicon precursor in step (b) may be at least 90:10, or at least 85:15, or at least 80:20. Optionally, the mass ratio (on a silicon-equivalent basis) of porous particles to silicon precursor in step (b) may be 50:50 or less, or 60:40 or less, or 70:30 or less.

[0110] The temperature in step (c) is preferably in the range of 300-800°C, or 300-750°C, or 300-700°C, or 300-650°C, or 300-600°C, or 320-550°C, or 320-500°C, or 340-450°C, or 350-450°C, or 300-395°C, or 320-380°C. Generally, lower temperatures (e.g., 320-500°C, or 340-450°C, or 350-450°C, or 320-380°C) are preferred because the reaction is not limited by mass transfer.

[0111] The pressure in the batch pressure reactor in step (c) is the spontaneous pressure and will depend on the type of silicon-containing precursor used, as well as the size of the porous particle charge and the presence of any inert padding gas. However, in all embodiments, the pressure in step (c) is above atmospheric pressure, preferably significantly above atmospheric pressure. For example, the pressure in step (c) may 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 carried out at or above the critical pressure of the silicon precursor.

[0112] When silicon is deposited from a silicon-containing precursor, by-product gases are generally removed, and the reactor pressure generally increases. For example, when silicon is deposited from silane gas (SiH4), approximately 2 moles of hydrogen gas are generally removed per mole of silane gas precursor. As a result, the partial pressure of the removed hydrogen is generally significantly higher than the partial pressure of the unreacted silane. In some cases, for example, if the amount of silicon-containing precursor packed into the reactor is small compared to the reactor volume, the pressure increase resulting from the complete conversion of the silicon-containing precursor may remain within the pressure tolerance range of a batch-type pressure reactor. Subsequently, the by-product gases can simply be evacuated from the reactor after the reaction is complete.

[0113] In other cases, it is necessary to control the pressure rise as the reaction progresses, preferably so 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 to control the pressure rise as the reaction progresses, and more preferably to prevent it from exceeding the maximum design pressure. This allows the by-product hydrogen gas to be separated from unreacted silane (or disilane, trisilane, etc.) so that the hydrogen gas can be discharged from the reactor.

[0114] Depending on the amount of silicon deposited in step (c), the method of the present invention can be operated as a multi-pass method using a series of deposition steps to deposit a target amount of silicon. The multipass method preferably includes the following additional steps: (d) A process of discharging by-product gas from a batch-type pressure reactor, (e) A step of adding a further charge of silicon-containing precursor to a batch pressure reactor, wherein the further charge of silicon-containing precursor gas is such that the reactor volume (g / L) RV ) A process that includes at least 2g of silicon per liter, (f) Heating the reactor to a temperature effective in causing further deposition of silicon in the pores of the porous particles, Includes.

[0115] Steps (d) to (f) can be repeated as many times as necessary to deposit the target amount of silicon.

[0116] The preferred operating parameters for loading the silicon-containing precursor into the reactor in step (b) and for the reaction in step (c) described above also apply to the iterations 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.

[0117] Optionally, at least one step (f) may be carried out at a lower temperature and / or pressure than step (c). If step (f) is repeated, each embodiment of step (f) may be carried out at a lower temperature and / or pressure than the preceding silicon deposition step (i.e., step (c) or the preceding step (f)).

[0118] It is believed that higher temperatures and pressures are favorable for faster deposition rates and faster pore capping, resulting in a lower surface area. However, these conditions may promote silicon deposition on the outer surface of the particles, which is unfavorable for SEI formation on exposed silicon. Therefore, the ability to vary the silicon deposition rate and location is a significant advantage. By having multiple packing steps at different temperatures and / or pressures, the silicon deposition rate in step (c) can be increased to fill most of the pore structure, and then one or more steps (f) can be performed at lower pressures and / or temperatures to slow down the deposition rate, thereby controlling the capping rate and preventing silicon deposition on the outer surface of the particles. Step (d) may optionally include a step of cooling the batch pressure reactor to a temperature below 300°C, i.e., a temperature too low for silicon deposition to occur. This allows the reactor to be re-equilibrium with a fresh pack of silicon-containing precursor before being reheated to the reaction temperature. However, if the injection time for the new silicon-containing precursor is short, a cooling step may not be necessary.

[0119] The range of different silicon filling amounts in the composite particles can be obtained using the method of the present invention. For example, the amount of silicon in the composite particle product from step (c) or step (f) may preferably be in the range of 5 to 60% by weight, based on the total mass of silicon and porous particle framework. Preferably, the amount of silicon in the composite particle product from step (c) or step (f) is 10-60% by weight, or 15-60% by weight, or 20-60% by weight, or 25-60% by weight, or 30-60% by weight, or 35-60% by weight, or 40-60% by weight, or 45-55% by weight.

[0120] The amount of silicon in the composite particles may be selected, following step (c), such that silicon occupies at least 25% and up to 80% or more of the internal pore volume of the porous particles. For example, silicon may occupy 25%–60%, 25%–55%, 30%–50%, 53–55%, 40–60%, 25%–45%, or 25%–40% of the internal pore volume of porous particles. Within these preferred ranges, the pore volume of porous particles is effective in accommodating the expansion of silicon during charging and discharging, while avoiding excessive pore volume that does not contribute to the volumetric capacity of particulate particles. However, the amount of silicon is not high enough to inhibit effective lithiation due to insufficient metal ion diffusion rates or mechanical resistance to lithiation resulting from insufficient expansion volume.

[0121] The amount of silicon in porous particles is determined by the mass ratio of silicon to porous particles [0.5 × P 1 ~1.9×P 1 The requirement that ]:1 can be correlated with the available pore volume, where P1 is the size of the total pore volume of micropores and mesopores in the porous particle in cm². 3 It is a dimensionless quantity expressed in / g (for example, a porous particle with a total volume of micropores and mesopores of 1.2 cm³). 3 If / g is present, P 1 =1.2). This relationship defines the weight ratio of silicon that occupies approximately 20% to 82% of the pore volume, taking into account the silicon density and the pore volume of porous particles.

[0122] Preferably, at least 90% by weight, more preferably at least 95% by weight, and even more preferably at least 98% by weight of the silicon mass in the composite particles are located within the internal pore volume of the porous particles, such that there is no or very little silicon located on the external surface of the composite particles. The reaction kinetics of the CVI process ensure that preferential deposition of silicon occurs on the internal surface of the porous particles.

[0123] The properties of composite particles can be further characterized by thermogravimetric analysis (TGA) in air. This analytical method is based on the principle that when silicon is oxidized to silicon dioxide (SiO2) in air at high temperatures, a weight increase is observed. The mechanism of silicon oxidation is temperature-dependent. Silicon atoms on the surface of silicon nanostructures are oxidized at a lower temperature than the bulk silicon atoms of the silicon nanostructures (Reference: Bardet et al., Phys.Chem.Chem.Phys. (2016), 18, 18201).

[0124] The composite particles of the present invention preferably have a low coarse bulk silicon content, as determined by TGA. Coarse bulk silicon is defined herein as silicon that undergoes oxidation above 800°C, as determined by TGA, where TGA is carried out in air at a temperature rise rate of 10°C / min. Therefore, the coarse bulk silicon content is determined according to the following formula. Z = 1.875 × [(M f -M 800 ) / M f ] × 100% In the formula, Z is the proportion of unsilicon oxide at 800°C, and M 800 This is the mass of the sample at 800°C, M f This represents the mass of the ash at the end of oxidation at 1400°C. In this analysis, we assume that the mass increase above 800°C corresponds to the oxidation of silicon to SiO2, and that the total mass at the end of oxidation is SiO2.

[0125] Silicon that undergoes oxidation above 800°C is not very desirable. Preferably, the coarse bulk silicon determined by TGA is 10% by weight or less, or 8% by weight or less, or 6% by weight or less, or 5% by weight or less, or 3% by weight or less, or 2% by weight or less.

[0126] The amount of silicon in the composite particles can be determined by elemental analysis. Preferably, elemental analysis can be used to determine the weight percentages of carbon (and optionally hydrogen, nitrogen, and oxygen) in the porous carbon particles alone and in the silicon-containing composite particles. Determining the weight percentage of carbon in the porous carbon particles alone takes into account the possibility that the porous carbon particles contain small amounts of heteroatoms. By performing both measurements together, the weight percentage of silicon in the porous carbon particles can be reliably determined.

[0127] The silicon content is preferably determined by ICP-OES (inductively coupled plasma-optical emission spectroscopy). Numerous ICP-OES instruments are commercially available, such as the iCAP® 7000 series ICP-OES analyzers available from ThermoFisher Scientific. The carbon content (and, if necessary, hydrogen, nitrogen, and oxygen content) of composite particles and porous carbon particles alone is preferably determined by IR absorption. A suitable instrument for measuring the carbon, hydrogen, nitrogen, and oxygen content is the TruSpec® Micro elemental analyzer available from Leco Corporation.

[0128] 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, 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.

[0129] The silicon-containing composite particles are preferably D in the range of 0.5 to 30 μm. 50 It has a particle size. D of the composite particles at the end of the CVI process 50 If the particle size exceeds 30 μm, the composite particles are preferably reduced to 30 μm or less by, for example, milling before being used in the manufacture of electrodes. 50 The size is reduced to the particle size. D 50Composite particles with a particle diameter of 30 μm or less exhibit good dispersibility in slurry, structural robustness, and high capacity retention during repeated charge-discharge cycles, making them suitable for forming dense electrode layers with uniform thickness within the conventional thickness range of 20 to 50 μm.

[0130] Optionally, D of silicon-containing composite particles 50 The particle size may 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 be 20 μm or less, or 18 μm or less, or 16 μm or less, or 14 μm or less, or 12 μm or less, or 10 μm or less, or 8 μm or less.

[0131] For example, silicon-containing composite particles are D in the range of 1-20 μm, or 1-18 μm, or 1-16 μm, or 2-16 μm, or 2-14 μm, or 2-12 μm, or 2-10 μm, or 2-8 μm. 50 It may have a particle size.

[0132] D of silicon-containing composite particles 10 The particle size is preferably 0.5 μm or larger, or 0.8 μm or larger, or 1 μm or larger. 10 Maintaining a particle size of 0.5 μm or larger reduces the possibility of undesirable aggregation of submicron-sized particles, resulting in improved dispersibility and volume retention of the particulate material.

[0133] D of silicon-containing composite particles 90 The particle size is preferably 50 μm or less, or 40 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less, or 15 μm or less. The presence of very large particles will result in uneven particle packing in the electrode active layer, and therefore will disrupt the formation of a dense electrode layer, especially an electrode layer having a thickness in the range of 20 to 50 μm. Therefore, D 90 The particle size is preferably a maximum of 40 μm, and more preferably even lower.

[0134] Silicon-containing composite particles preferably have a narrow particle size distribution range. For example, a particle size distribution range ((D 90 -D 10 ) / D 50 The particle size (as defined) is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. By keeping the particle size distribution range narrow, efficient particle filling into a dense electrode layer can be achieved more easily.

[0135] The silicon-containing composite particles are preferably 300 m 2 / g or less, 250m 2 / g or less, 200m 2 / g or less, 150m 2 / g or less, 100m 2 / g or less, 80m 2 / g or less, 60m 2 / g or less, 40m 2 / g or less, 30m 2 / g or less, 25m 2 / g or less, 20m 2 / g or less, 15m 2 / g or more, 10m 2 / g or more, or 5m 2 The BET specific surface area is less than or equal to / g. Generally, a lower BET surface area is preferable to minimize the formation of a solid electrolyte interface (SEI) layer on the surface of the composite particles during the first charge-discharge cycle of the negative electrode. However, an excessively low BET surface area results in unacceptably low charging speed and capacity because the bulk of the electroactive material cannot access the metal ions in the surrounding electrolyte. For example, the BET surface area is preferably at least 0.1m². 2 / g, or at least 1m 2 / g, or at least 2m 2 / g, or at least 5m 2 It is / g. For example, the BET specific surface area is 1m 2 / g~25m 2 It may be within the range of / g, and more preferably 2 to 15m 2 It is within the range of / g.

[0136] Preferably, the silicon-containing composite particles have a specific charge capacity of 1200 to 2340 mAh / g during initial lithiumization. Preferably, the silicon-containing composite particles have a specific charge capacity of at least 1400 mAh / g during initial lithiumization.

[0137] The reaction process can be carried out using any reactor capable of operating in batch mode and at high pressure. A batch pressure reactor is generally a batch reactor that can be operated in such a way that the pressure inside the reactor is greater than the pressure around the reactor.

[0138] Batch-type pressure reactors are preferably types of reactors selected from the group consisting of tubular reactors, fluidized bed reactors, fixed bed reactors, and autoclaves. Fluidized bed reactors and autoclaves are particularly preferred, and autoclaves are especially preferred.

[0139] Porous particles and formed composite particles may be present in the reactor in the form of a static bed of particles or a moving bed of particles. A static bed of particles is preferred when the volume of the charge of porous particles is high relative to the usable volume of the batch pressure reactor, for example, at least 80%, at least 90%, or at least 95% of the usable volume of the batch pressure reactor (i.e., the reactor is substantially filled with porous particles in step (b)). The silicon-containing precursor can then be distributed throughout the entire volume of porous particles before the reaction is initiated. Thus, since the silicon-containing precursor is already present in the pores at the start of the reaction, there is no limitation on mass transfer. The reaction proceeds at the same conversion rate at any location in the reactor, unless there is a temperature profile in the reactor.

[0140] Batch pressure reactors, which can be used in static beds without mixing, can have any desired geometric shape. Preferred forms of reactor structures are cylindrical, conical, spherical, and polyhedral shapes or combinations thereof.

[0141] Reactors preferred for the static bed reaction are shell and tubular furnace reactors. This type of reactor includes a plurality of reaction tubes (e.g., 10 to 500 tubes) disposed within a pressure vessel shell. To minimize the temperature profile during the CVI reaction, the tubes typically have a diameter of 5 to 200 mm. The tubes are sealed from the shell, forming two independent cavities within the reactor. The cavity on the tube side constitutes the reactor volume and contains the porous particles and silicon-containing precursor during the CVI reaction. The cavity on the shell side can be filled with 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.

[0142] The porous particles can be loaded into the tubes, for example, by suction through a porous plate disposed at one end of the tube. Thereafter, before introducing a predetermined amount of the silicon-containing precursor, the cavity on the tube side can be sealed, evacuated using a vacuum, and purged with an inert gas. The cavity on the tube side may include a hydrogen selectivity membrane element to facilitate the removal of hydrogen, which is a by-product, and the control of the internal pressure.

[0143] 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 homogeneity within the reactor.

[0144] Reactors suitable for the moving bed reaction include autoclave reactors equipped with internal stirrers. The autoclave can be heated internally via a plurality of heating rods or a tube-type heat exchanger. Alternatively, the outer wall of the autoclave can be heated by resistance heating elements or convection heating. The autoclave reactor may be provided with a hydrogen selective membrane element to facilitate the removal of hydrogen, which is a by-product, and the control of the internal pressure. Other methods for maintaining a moving bed of particles during the CVI reaction include vibration, ultrasonic waves, and fluidization techniques. Examples of reactors suitable for the moving bed reaction include the stirred pressure reactor system of Parr Instrument Company (registered trademark) and the stirred autoclave of Novoclave (registered trademark) of Buchi AG (registered trademark).

[0145] A moving bed batch reactor can have any form of reactor structure in which the solid bed can be agitated. These are, for example, moving reactors, reactors with moving agitation elements, or gas-passing reactors, or combinations thereof.

[0146] The form of movement in a moving bed reactor is preferably a rotational movement. Other forms of movement are equally suitable. Preferred structural forms of the rotating reactor are, for example, drum reactors 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 symmetric structural form, the axis of rotation is preferably on the axis of symmetry of the reactor. In the case of an asymmetric structural form, the axis of rotation preferably passes through the center of gravity of the reactor. In another preferred embodiment, the axis of rotation is selected such that a tumbling motion occurs. The mixing events in the moving bed reactor are preferably facilitated by internal components. Typical internal components are guide plates, blades, vanes, blades, etc. According to the present invention, the direction of the axis of rotation can now be freely selected. The axis of rotation is preferably oriented in the vertical direction, the horizontal direction, or at a free angle with respect to the horizontal embodiment.

[0147] A more preferred configuration for a moving floor is a fixed batch pressure reactor with a moving agitator. Preferred shapes for this include cylindrical reactors, conical reactors, spherical reactors, polyhedral reactors, or combinations thereof. The movement of the agitator is preferably rotational. Other forms of movement are equally preferred. The agitator is preferably driven via agitator shafts, and there may be one or more agitators per agitator shaft. A batch pressure reactor is preferably incorporated with multiple agitator shafts, each of which may have one or more agitators. The main reactor shafts are preferably aligned horizontally or vertically. In a more preferred embodiment, the agitator shafts are installed horizontally or vertically in reactors of any orientation. For a batch pressure reactor operated vertically, a preferred structural configuration is, for example, one or more agitators that mix the floor material by rotational motion via the main agitator shaft. Furthermore, a configuration in which two or more agitator shafts are arranged in parallel is also preferred. There is also a preferred configuration in which two or more agitator shafts are operated in a non-parallel manner. Another preferred configuration of the structure for a batch pressure reactor operated vertically is characterized by the use of a screw conveyor. The screw conveyor preferably transports the flooring material through the center. A further design according to the present invention is that the screw conveyor rotates along the ends of the reactor. For a batch pressure reactor operated horizontally, a preferred configuration is, for example, that a stirring element or a plurality of stirring elements mix the flooring material by rotational motion via a main stirring shaft. A configuration in which two or more stirring shafts are arranged in parallel is also possible. Even more preferred is a configuration in which two or more stirring shafts do not operate parallel to each other. For a batch pressure reactor operated vertically, preferred stirring elements are selected from the group including helical stirrers, spiral stirrers, anchor stirrers, or stirring elements that generally transport the flooring material axially or radially, or both axially and radially. For a batch pressure reactor operated horizontally, preferably, multiple stirring elements are present on a single shaft.Configurations of structures according to the present invention for stirring elements in horizontally operating reactors include blades, paddles, blade stirrers, spiral stirrers, or generally, stirring elements that convey bed material in both axial and radial directions. In addition to moving stirring elements, rigid internal structures such as guide plates are also preferred in fixed-batch pressure reactors equipped with moving stirring elements. Particularly preferred are configurations in which both the reactor and the stirring element rotate.

[0148] As a further possibility for mixing, the material bed is preferably exposed to a gas flow. Particularly preferred here is a structure such as a fluidized bed reactor. Even more preferred is a batch pressure reactor in which a mixing zone is intentionally formed within the reactor by the use of pneumatic pressure.

[0149] Regarding the structure of a batch-type pressure reactor, in principle, any material is suitable as long as it possesses the necessary mechanical strength and chemical resistance under its respective operating conditions. In terms of chemical resistance, a batch-type pressure reactor can be constructed from a corresponding solid material and a chemically non-reactive material (pressure-resistant material) with a specific coating or plating applied to the parts that come into contact with the medium. These materials are preferably selected from the group including the following: - Metallic materials: (According to DIN CEN ISO / TR 15608) Steel corresponds to material groups 1-11, nickel and nickel alloys to groups 31-38, titanium and titanium alloys to groups 51-54, zirconium and zirconium alloys to groups 61 and 62, and cast iron to groups 71-76. - Ceramic materials containing oxide ceramics, such as elemental systems of aluminum oxide, magnesium oxide, zirconium oxide, titanium dioxide (capacitor material), or multi-system systems of aluminum titanate (mixture of aluminum oxide and titanium oxide), mullite (mixture of aluminum oxide and silicon oxide), lead zirconate titanate (piezoelectric ceramic), or dispersed ceramics such as zirconium oxide-reinforced aluminum oxide (ZTA: zirconia-reinforced aluminum oxide, Al2O3 / ZrO2). - Non-oxide ceramics, such as carbides including silicon carbide and boron carbide, nitrides such as silicon nitride, aluminum nitride, boron nitride and titanium nitride, borides and silicides, and mixtures thereof, and - Composite materials, such as particulate composite materials like cemented carbide, ceramic composite materials, concrete and polymer concrete; fiber composite materials such as glass fiber reinforced glass, metal matrix composite materials (MMC), fiber cement, carbon fiber reinforced silicon carbide, self-reinforcing thermoplastics, steel reinforced concrete and fiber reinforced concrete; fiber-plastic composite materials such as carbon fiber reinforced plastic (CRP), glass fiber reinforced plastic (GRP), aramid fiber reinforced plastic (ARP), fiber-ceramic composite materials (ceramic matrix composite materials (CMC)); impregnated composite materials such as metal matrix composite materials (MMC), dispersion reinforced aluminum alloys and dispersion reinforced nickel-chromium superalloys; and layered composite materials such as bimetals, titanium-graphite composite materials, composite plates and composite tubes, glass fiber reinforced aluminum and sandwich structures, and structural composite materials.

[0150] The surface of electroactive materials deposited by CVI is generally reactive to oxygen, and when exposed to atmospheric oxygen, a native oxide layer is generally formed. In the case of silicon, when the silicon surface is generally exposed to oxygen, an amorphous silicon oxide film is immediately formed. Since the formation of the native oxide layer is generally exothermic, careful process control is required to prevent overheating and combustion of particulate matter during manufacturing. The presence of the native oxide layer is generally associated with irreversible capacity loss and reduced cycle life, and can therefore adversely affect the performance of electroactive materials in lithium-ion batteries. Accordingly, the process of the present invention may optionally include a step (g) of contacting the surface of deposited silicon with a passivation agent, where the silicon is not exposed to oxygen before contact with the passivation agent.

[0151] 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 multipass deposition process.

[0152] A passivator is defined herein as a compound that can modify the surface of an electroactive material to inhibit or prevent the formation of surface oxides.

[0153] Suitable passivating agents include, for example, compounds containing an alkene, alkyne, or carbonyl functional group, more preferably a terminal alkene, terminal alkyne, or aldehyde group.

[0154] Preferred passivating agents include one or more compounds of the following formula. (i) R-CH=CH-R (ii) RC≡CR (iii) O=CH-R In the above formula, R represents H, or an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, preferably 2 to 10 carbon atoms, or the two R groups in formula (i) form an unsubstituted or substituted hydrocarbyl ring structure containing 3 to 8 carbon atoms.

[0155] Particularly preferred passivating agents include one or more compounds of the following formula. (i) CH2 = CH-R (ii) HC≡CR In the above formula, R is as defined above. Preferably, R is non-substitutable.

[0156] Examples of suitable compounds include ethylene, propylene, 1-butene, butadiene, 1-pentene, 1,4-pentadiene, 1-hexene, 1-octene, styrene, divinylbenzene, acetylene, phenylacetylene, norbornene, norbordadiene, and bicyclo[2.2.2]octo-2-ene. Mixtures of different passivators can also be used.

[0157] It is generally understood that the alkenes, alkynes, or carbonyl groups of passivators undergo insertion reactions with the MH groups (where M represents an atom of the electroactive material) on the surface of an electroactive material, forming a covalently passivated surface resistant to oxidation by air. When silicon is the electroactive material, the passivation reaction between the silicon surface and the passivator can be understood as a form of hydrosilylation, as schematically shown below. [ka]

[0158] Other suitable passivators include compounds containing active hydrogen atoms bonded to oxygen, nitrogen, sulfur, or phosphorus. For example, the passivator may be an alcohol, amine, thiol, or phosphine. The reaction between the group -XH and the hydride group on the surface of the electroactive material is understood to result in the exclusion of H2 and the formation of a direct bond between X and the electroactive material surface.

[0159] Suitable passivators in this category include, for example, compounds of the following formula: (iv) HX-R (In the formula, X represents O, S, NR, or PR, and each R is independently defined as described above.) The two R groups in formula (iv) may form an unsubstituted or substituted hydrocarbyl ring structure containing 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. Additionally, amine groups can be incorporated into 4 to 10-membered aliphatic or aromatic ring structures, such as pyrrolidine, pyrrole, imidazole, piperazine, indole, or purine.

[0160] The contact between the electroactive material and the passivating agent in step (g) may be carried out at a temperature within the range of 25 to 800 °C, preferably 750 °C or lower, or 700 °C or lower, and at a pressure within the range of 100 kPa to 50 MPa. For example, step (g) may be suitably carried out within the preferred temperature and pressure ranges of step (c) and / or step (f) defined herein.

[0161] Passivation in step (g) may optionally be carried out in the same batch pressure reactor as in steps (c) and / or (f), for example, by cooling the batch pressure reactor to an appropriate temperature, evacuating by-product gas from the batch pressure reactor; adding a passivating agent charge to the batch pressure reactor; and passivating the exposed silicon surface of the composite particles by the passivating agent.

[0162] The process of the present invention may further include a step of depositing a lithium ion permeable material in the remaining exposed pores and / or on the outer surface of the composite particles after the final deposition from step (c), step (f) or step (g). Thereby, the surface area of the composite particles is reduced, and by sealing the nanoscale electroactive material domains away from the access of the electrolyte, further improvement in the performance of the composite particles when used as an electroactive material for a lithium ion battery can be obtained.

[0163] Suitable lithium ion permeable materials include, for example, conductive pyrolytic carbon materials. The conductive pyrolytic carbon material within the pores and / or on the outer surface of the composite particles is advantageous for improving the electron transport to and from the bulk of the composite particles. This helps to improve the rate performance of the composite particles.

[0164] Pyrolytic carbon can be deposited on the surface of the silicon-containing composite particles by chemical vapor deposition (CVD), i.e., by thermal decomposition of a volatile carbon-containing gas (such as ethylene).

[0165] Suitable processes include, for example, the following steps: (h) A step of combining composite particles from step (c), step (f), or step (g) with a pyrolysis carbon precursor, and (i) A step of heating the pyrolysis carbon precursor to a temperature effective in causing the deposition of pyrolysis conductive carbon material in the pores and / or on the outer surface of the composite particles, Includes.

[0166] Step (h) is preferably carried out at a temperature in the range of 300 to 800°C, or in the range of 400 to 700°C. For example, the temperature in step (i) may be 680°C or lower, or 660°C or lower, or 640°C or lower, or 620°C or lower, or 600°C or lower, or 580°C or lower, or 560°C or lower, or 540°C or lower, or 520°C or lower, or 500°C or lower. The minimum temperature in step (i) depends 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.

[0167] Suitable examples of pyrolysis carbon precursors include the hydrocarbons mentioned above.

[0168] Further examples of suitable hydrocarbons include polycyclic hydrocarbons containing 10 to 25 carbon atoms and optionally 1 to 3 heteroatoms, and optionally, polyaromatic hydrocarbons are selected from naphthalene, substituted naphthalenes such as dihydroxynaphthalene, anthracene, tetracene, pentacene, fluorene, acenaptene, phenanthrene, fluoroanthrene, pyrene, chrysene, perylene, coronene, fluorenone, anthraquinone, anthrone, and alkyl-substituted derivatives thereof. Suitable pyrolysis carbon precursors include bicyclic monoterpenoids, and optionally, the bicyclic monoterpenoids are selected from camphor, borneol, eucalyptol, camphene, carene, sabinene, thujene, and pinene. Further preferred pyrolysis carbon precursors include C2-C10 hydrocarbons, which are optionally selected from alkanes, alkenes, alkynes, cycloalkanes, cycloalkenes, and arenes, such as methane, ethylene, propylene, limonene, styrene, cyclohexene, α-terpinene, and acetylene. Other suitable pyrolysis carbon precursors include phthalocyanines, sucrose, starch, graphene oxide, reduced graphene oxide, pyrenes, perhydropyrene, triphenylene, tetracene, benzopyrene, perylenes, coronene, and chrysene. A preferred carbon precursor is acetylene.

[0169] The pyrolysis carbon precursor used in step (i) may be used in its pure form or diluted and mixed with an inert carrier gas such as nitrogen or argon. For example, the pyrolysis carbon precursor may be used in amounts ranging from 0.1 to 100% by volume, or 0.5 to 20% by volume, or 1 to 10% by volume, or 1 to 5% by volume, 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% by volume, more preferably less than 0.001% by volume, based on the total volume of the gas used in step (i).

[0170] The deposition of conductive carbon by CVD may optionally be carried out 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, discharging the by-product gas from the batch pressure reactor, adding a charge of carbon-containing precursors to the batch pressure reactor, and heating the reactor to a temperature effective in causing the deposition of thermally decomposed conductive carbon material in the pores and / or on the outer surface of the composite particles.

[0171] Alternatively, the deposition of conductive carbon by CVD may be carried out in another conventional reactor type (e.g., a fluidized bed reactor or a rotary kiln reactor) under a flow of gas containing a carbon-containing precursor. Alternatively, the carbon coating may be formed by depositing a solution of a carbon-containing compound onto the surface of composite particles, followed by thermal decomposition.

[0172] Carbon coating has the advantage of further reducing the BET surface area of ​​composite particles by smoothing surface defects and filling remaining surface micropores, thereby further reducing first-cycle losses. Furthermore, carbon coating improves the conductivity of the composite particle surface, reduces the need for conductive additives in the electrode composition, and creates an optimal surface for the formation of a stable SEI layer, resulting in improved capacity retention during cycling.

[0173] Furthermore, reducing the surface area of ​​the composite particles also has the effect of reducing the amount of binder required to form the electrode active layer containing the composite particles. Excess binder is known to contribute to a decrease in rate performance.

[0174] If a carbon coating is present, the silicon-containing composite particles are preferably 150m 2 / g or less, or 100m 2 / g or less, or 80m 2 / g or less, or 60m 2 / g or less, or 40m 2 / g or less, or 30m 2 / g or less, or 25m 2 / g or less, or 20m 2 / g or less, or 15m 2 / g or less, or 10m 2 / g or less, 5m 2 / g or less, or 3m 2 It has a BET surface area of ​​less than or equal to / g.

[0175] When the lithium-ion permeable filler material is a conductive pyrolysis carbon material, the same compound may function as both the passivator in step (g) and the pyrolysis carbon precursor in step (h). For example, if styrene is selected as the pyrolysis carbon precursor, styrene will also function as a passivator if silicon is not exposed to oxygen before contact with 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 at temperatures in the range of 300 to 800°C, for example. Alternatively, the passivation in step (g) and the deposition of the conductive carbon material in steps (h) and (i) can be carried out sequentially using the same material as the passivator and pyrolysis carbon precursor, but step (i) is carried out at a higher temperature than step (g). For example, step (g) may be carried out at temperatures in the range of 25°C to less than 300°C, and step (i) may be carried out at temperatures in the range of 300 to 800°C.

[0176] Alternatively, different compounds may be used as the passivator in step (g) and the pyrolysis carbon precursor in step (h). For example, the electroactive material can first be brought into contact with the passivator in step (g), and then the conductive pyrolysis carbon material can be deposited in steps (h) and (i), where the pyrolysis carbon precursor used in step (h) is different from the passivator used in step (g). For example, the passivator in step (g) may be styrene, and the pyrolysis carbon precursor in step (h) may be a compound such as cyclohexane that can form a pyrolysis carbon material but cannot passivate the surface of the electroactive material.

[0177] Several preferred embodiments of Phases 1-7 of this process are described in more detail below. For clarity, the above-mentioned general or preferred embodiments of this process, such as starting materials like porous particles, silicon-containing precursors, dopants or hydrocarbons, or reaction conditions like temperature, pressure or inert gas padding, or embodiments or execution of the process using a batch pressure reactor, are disclosed with reference to and in combination with the following descriptions of Phases 1-7.

[0178] In Phase 1, porous particles are packed into a batch pressure reactor. The batch pressure reactor is then typically closed.

[0179] The filling of porous particles into a batch pressure reactor can be carried out, for example, under an inert gas atmosphere or preferably under ambient air. The inert gas can be selected from the group consisting of hydrogen; noble gases, such as helium, neon, argon, krypton, xenon; nitrogen; carbon dioxide; or foaming gases or mixtures thereof. Argon, or in particular nitrogen, is preferred.

[0180] In Phase 2, one or more silicon-containing precursors are charged into a batch-type pressure reactor.

[0181] In Phase 2, it is particularly preferable to first charge the batch pressure reactor with an inert gas or to evacuate the batch pressure reactor, especially before charging the silicon-containing precursor into the batch pressure reactor. Examples of inert gases and preferred embodiments are described above for Phase 1. Particularly preferable, the operation is carried out without an inert gas.

[0182] The batch pressure reactor is preferably charged with an amount of silicon-containing precursor such that, in relation to the amount of porous particles weighed, a sufficient amount of silicon is deposited to reach a target volume of silicon-containing composite particles to be produced.

[0183] In this context, charging generally refers to the introduction of a silicon-containing precursor into a batch pressure reactor. During introduction into the batch pressure reactor, the silicon-containing precursor may exist, for example, in the form of a gas, liquid, or sublimable solid. The batch pressure reactor is then generally sealed airtight.

[0184] In phase 2, the batch pressure reactor is charged with one or more silicon-containing precursors and optionally one or more further components such as one or more inert gases, hydrogen, one or more dopants, or one or more hydrocarbons. The silicon-containing precursors can generally be introduced into the batch pressure reactor as a mixture, separately, as a mixture with the inert gas, or as a pure substance. The partial pressure of the inert gas is preferably 0-99%, more preferably up to 50%, particularly preferably up to 30%, and very preferably up to 5%, relative to the total pressure of the silicon-containing precursors under standard conditions (according to DIN 1343). In one particularly preferred embodiment, the batch pressure reactor does not contain an inert gas. Embodiments of such dopants or such hydrocarbons are described above.

[0185] In Phase 3, in other words, after the silicon-containing precursor is typically charged into a batch pressure reactor, the generally closed batch pressure reactor is heated until a target temperature is reached. At the target temperature, the decomposition of the silicon-containing precursor begins, resulting in the deposition of silicon within the pores of the porous particles and optionally on the surface. The initiation of the decomposition of the silicon-containing precursor, accompanied by silicon deposition, can be experimentally confirmed by an increase in pressure within the batch pressure reactor, which is not caused by an increase in temperature within the batch pressure reactor. In the case of the decomposition of the silicon-containing precursor, gaseous molecules are generally formed, similar to silicon, leading to an increase in pressure within the batch pressure reactor. The volume of the batch pressure reactor is generally kept constant throughout the process. The decomposition temperature is also listed in standard chemical tables concerning the properties of chemical substances.

[0186] Preferably, in Phase 3, the pressure change during heating of the closed-batch pressure reactor is expressed, for example, by the following equation 1:

number

[0187] After achieving the target temperature for the decomposition of the silicon-containing precursor in Phase 3, the Phase 4 temperature in the batch pressure reactor can be increased, kept constant, or decreased to a small extent in relation to the target temperature of Phase 3.

[0188] Temperature, pressure, or differential pressure measurements in a Phase 3 batch pressure reactor can be determined using measurement techniques and equipment common to batch pressure reactors. With customary calibration, the same results can be obtained with different measuring instruments.

[0189] 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 example, in the case of SiH4, the target temperature is preferably in the range of 370 to 500°C, more preferably 390 to 450°C, and very preferably 400 to 420°C. The target temperature for HSiCl3 is preferably in the range of 400 to 1000°C, more preferably 600 to 800°C. The target temperature for H2SiCl2 is preferably in the range of 350 to 800°C, and more preferably in the range of 450 to 550°C.

[0190] When hydrocarbons are charged, the target temperature applied at the end of Phase 3 and during Phase 4 is preferably the temperature at which the decomposition of the hydrocarbons begins and carbon deposits in the pores of the porous particles and optionally on the surface. 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.

[0191] During Phase 4, the pressure in the batch pressure reactor preferably rises to at least 7 bar.

[0192] In one preferred embodiment, the progress of the reaction during the process is monitored based on pressure changes. In this way, it is possible to determine, for example, the degree of infiltration or the end of infiltration. Infiltration refers to the deposition of silicon within the pores of the porous particles in phase 4 and optionally on the surface. The end of infiltration can be determined, for example, by the absence of further pressure increases.

[0193] The pressure change in a batch-type pressure reactor during Phase 4 is generally expressed, for example, by Equation 2 below:

number

[0194] The pressure change in Phase 4 is preferably a substantial product of the change in the amount of substance during the silicon deposition process. Therefore, advantageously, the completion of the reaction of the silicon-containing precursor can be recognized by the absence of further pressure increases at the end of Phase 4, thus allowing subsequent phases to be time-effectively triggered without unnecessarily removing unreacted silicon-containing precursors from the reactor, and achieving complete conversion.

[0195] In phase 4, the temperature is preferably not increased by heating. The temperature in phase 4 is preferably increased as a result of heat generated from the potentially exothermic decomposition of the silicon-containing precursor. More preferably, there is a slight temperature decrease in phase 4, and more preferably, a temperature decrease of up to 20°C during phase 4.

[0196] The pressure increase in the batch pressure reactor during Phase 4 (decomposition of silicon-containing precursor) is preferably higher than that during Phase 3 (heating of the batch pressure reactor), as shown in, for example, the following equation 3a:

number

number

[0197] In phase 4, the pressure inside the batch pressure reactor preferably reaches at least 10 bar, more preferably at least 50 bar, and more preferably at least 100 bar. In phase 4, the pressure inside the batch pressure reactor preferably remains at 400 bar or less, more preferably at 300 bar or less, and particularly preferably at 200 bar or less.

[0198] The dominant temperature in the batch pressure reactor during Phase 4 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] Temperature, pressure, pressure change, or differential pressure measurements in a Phase 4 batch pressure reactor can be determined using measurement techniques and equipment common to batch pressure reactors. Different measuring devices will yield the same results if conventional calibration is followed. The amount of a substance or the change in the amount of a substance can be determined, for example, by taking a specified volume of sample from the batch pressure reactor and determining its substantial composition by conventional methods such as gas chromatography.

[0200] The heating of the batch pressure reactor in phase 3 and optionally phase 4 may be carried out, for example, at a constant heating rate or at several different heating rates. The heating rate can be adapted by those skilled in the art on a case-by-case basis according to the design of the process, for example, according to the size of the reactor, the amount of porous particles in the reactor, the stirring technique, or the planned reaction time. The entire batch pressure reactor is preferably heated in phase 3 at a rate such that, despite rapid heating, the maximum temperature gradient within the batch pressure reactor at the temperature at which the decomposition of the silicon-containing precursor begins remains below 1000°C / m, more preferably below 100°C / m, and very preferably below 10°C / m. In this way, for example, it is possible to ensure that most of the silicon is deposited within the pores of the porous particles and not on their outer surface.

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

[0202] In Phase 3, heating of the batch pressure reactor is preferably carried out at a heating rate of 1 to 100°C / min, more preferably 2 to 50°C / min, and very preferably 3 to 10°C / min.

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

[0204] There are various technical solutions available to control the rate of pressure rise at different phases of the operation. To increase or decrease the pressure rise, the heat supplied to the reactor contents is preferably increased or decreased, respectively. To reduce the rate of pressure rise, it is also preferable to increase the removal of heat by cooling from the batch pressure reactor. For this purpose, it is preferable that one or more reactor walls are cooled or that equipment for removing heat is introduced into the reactor, examples of which include cooling pipes or cooling ribs. To control the pressure in the reactor very quickly, it is preferable to supply or remove small amounts of gas from the batch pressure reactor or to supply a liquid to evaporate. In this context, the by-flow removed from the batch pressure reactor is preferably returned to the reactor contents, either entirely or partially, in a closed circuit after cooling and / or removal of part of the overall flow.

[0205] The progress of the reaction in Phase 4 is preferably monitored analytically to recognize the end of the reaction, thereby minimizing the reactor occupancy time. Methods for observing the progress of the reaction include, for example, temperature measurements to determine exothermic or endothermic phenomena, pressure measurements to determine the progress of the reaction through changes in the ratio of solid and gaseous components of the reactor contents, and further techniques that allow observation of the changing composition of the gas space during the reaction.

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

[0207] In Phase 5, the batch pressure reactor is cooled. Cooling is preferably carried out after the completion of deposition and optionally to below the target temperature, preferably to the temperature of Phase 6.

[0208] In phase 6, gaseous byproducts of the reaction formed during the deposition process are preferably removed at the deposition temperature or after a temperature desirable for the removal of gaseous reaction byproducts is achieved, and removal is carried out from the gas space of the batch pressure reactor, for example by purging. It is preferable to use a purge gas. Before the purge gas is charged, the batch pressure reactor is preferably evacuated at least once. Preferred purge gases are inert gases, such as noble gases such as helium, neon, argon, krypton, xenon, or hydrogen, nitrogen, or carbon dioxide, which can be used individually, as a mixture, or as a mixture thereof with oxygen, for example, air or dilute air.

[0209] The batch pressure reactor is preferably purged with a mixture of inert gas and oxygen. In this way, it is possible to modify the surface of the silicon-containing composite particles, for example, by deactivating them. For example, it is possible to achieve reactions of any reactive groups present on the surface of the silicon-containing composite particles. The mixture of nitrogen and oxygen preferably contains up to 20% by volume, more preferably up to 10% by volume, and particularly preferably up to 5% by volume of oxygen. This process is carried out at a temperature preferably up to 200°C, more preferably up to 100°C, and particularly preferably up to 50°C.

[0210] In phase 7 of the process, the silicon-containing composite particles are removed from the batch pressure reactor while optionally maintaining the inert gas atmosphere present in the batch pressure reactor.

[0211] In one preferred embodiment of the process, phases 2 to 6 are repeated many times, in which case the silicon-containing precursor charged in phase 2 may be the same or different in each case.

[0212] In a more preferred embodiment of the process, phase 6 follows directly from phase 4, in other words, phase 5 can be omitted, or in other words, after phase 4, phase 6 can be continued without cooling the batch pressure reactor.

[0213] In a more preferred embodiment of the process, phases 2 to 6 are repeated one or more times, in which case phase 6 is omitted in one or more of the repetitions.

[0214] In a more preferred embodiment, phases 2 to 6, optionally omitting phase 5, are repeated one or more times (reaction cycle), in which case silicon-free reactive components may be used in individual or multiple repetitions, in which case the silicon-free reactive components in each repetition may be the same or different, however, in at least one reaction cycle, a reactive component containing a silicon-containing precursor is used. 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 in the repetition of phases 2 to 6. Preferred silicon-free reactive components are hydrocarbons. When using silicon-free reactive components, carbon is preferably deposited in the pores of porous particles or silicon-containing composite particles and optionally on the surface.

[0215] In one particularly preferred embodiment, in the first reaction cycle, one or more silicon-containing precursors are charged in phase 2, and in the second reaction cycle, one or more reactive components containing hydrocarbons are charged, the latter components preferably not containing silicon-containing precursors, and phase 5 is optionally omitted. This means makes it possible to obtain, for example, silicon-containing composite particles that do not have outward-facing free silicon surfaces.

[0216] In a further preferred embodiment, in the first reaction cycle, in phase 2, a reactive component containing at least one hydrocarbon and not containing a silicon-containing precursor is charged; in the second reaction cycle, a reactive component containing one or more silicon-containing precursors is used, and phase 5 is optionally omitted. Optionally, in the third reaction cycle, a further hydrocarbon-containing reactive component not containing a silicon-containing precursor is used, and phase 5 is optionally omitted. The result is, for example, a silicon-containing composite particle having a carbon layer between porous particles and deposited silicon, and optionally having an additional outer carbon layer, meaning there are no outwardly facing free silicon surfaces. Preferred reactive components other than silicon-containing precursors are one or more hydrocarbons. Hydrocarbons and their preferred embodiments are as described above.

[0217] The reactive component, which contains one or more hydrocarbons but does not contain a silicon-containing precursor, preferably does not contain further components or one or more inert gases and / or hydrogen and / or one or more dopants. Dopants and preferred embodiments thereof are described above.

[0218] During phases 2-6, the porous particles and / or the resulting silicon-containing composite particles may generally exist in the form of a stationary bed or in an stirred form with mixing. A stirred mixture of the porous particles and / or the resulting silicon-containing composite particles in a batch pressure reactor is preferred. This allows, for example, homogeneous contact between all the porous particles and the reactive components, particularly the silicon-containing precursor, or a homogeneous temperature distribution within the bed. The particles can be stirred, for example, by internal stirring components in the reactor, by the movement of the entire reactor, or by fluidizing the solids in the reactor with a gas flow.

[0219] Steps a) to c) of this method are preferably divided into the above process phases 1 to 7, and more preferably steps b) to c) are divided into process phases 1 to 7. Step b) preferably consists of phases 1 and 2. Step c) preferably consists of phases 3 to 7, particularly phases 3 and 4.

[0220] The silicon-containing composite particles that can be obtained by the process of the present invention preferably have a diameter ratio d in the range of 0.5 to 20 μm. 50 It has a volume-weighted particle size distribution. 50 The value is preferably at least 1.5 μm, and more preferably at least 2 μm. Diameter ratio d 50 The particle size is preferably a maximum of 13 μm, and more preferably a maximum of 8 μm.

[0221] The volume-weighted particle size distribution of silicon-containing composite particles is preferably the diameter ratio d 10 ≥0.2μm and d 90 Located between ≤20.0 μm, more preferably 10 ≥0.4μm and d 90 Between ≤15.0 μm, most preferably d 10 ≥0.6μm and d 90 The size should be between ≤12.0 μm.

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

[0223] Silicon-containing composite particles have a diameter ratio d 90 It preferably has a volume-weighted particle size distribution of ≥5 μm, more preferably ≥10 μm. Diameter ratio d 90 The particle size is 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 is preferably ≤15.0 μm, more preferably ≤12.0 μm, even more preferably ≤10.0 μm, particularly preferably ≤8.0 μm, and most preferably ≤4.0 μm. 90 -d 10 There is a difference. The volume-weighted particle size distribution of the silicon-containing composite particles is preferably ≥0.6 μm, more preferably ≥0.8 μm, and most preferably ≥1.0 μm. 90 -d 10 It contains the difference.

[0225] Silicon-containing composite particles may be isolated or aggregated. Preferably, the silicon-containing composite particles are not aggregated and preferably not in the form of clumps. The terms isolated, clumps, and non-aggregated have already been defined above in relation to porous particles. The presence of silicon-containing composite particles in the form of aggregates or clumps can be visualized, for example, by a conventional scanning electron microscope (SEM).

[0226] The silicon-containing composite particles may have any desired shape, and therefore may be, for example, plate-like, irregular, fragment-like, spherical, or other needle-like, with fragment-like or spherical particles being preferred.

[0227] According to Wadell's definition, sphericity ψ is the ratio of the surface area of ​​a sphere of equal volume to the actual surface area of ​​an object. For a sphere, the value of ψ is 1. According to this definition, the silicon-containing composite particles obtainable by the process of the present invention have a sphericity ψ of preferably 0.3 to 1.0, more preferably 0.5 to 1.0, and most preferably 0.65 to 1.0.

[0228] Sphericity S is the ratio of the circumference of an equivalent circle having the same area A as the projection of the particle projected onto the surface to the measured circumference U of this projection:

number

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

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

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

[0232] If the porous particles contain a silicon compound, such as silicon dioxide, the above weight percentage of silicon obtained through deposition from a silicon-containing precursor can be determined by subtracting the silicon mass in the porous particles, as confirmed by elemental analysis, from the silicon mass in the silicon-containing composite particles, as confirmed by elemental analysis, and then dividing the result by the mass of the silicon-containing composite particles.

[0233] The volume of silicon contained in silicon-containing composite particles and obtained through deposition from a silicon-containing precursor is calculated by multiplying the mass fraction of silicon obtained through deposition from the silicon-containing precursor by the total mass of the silicon-containing composite particles, and then calculating the silicon density (2.336 g / cm³). 3 This is the value obtained by dividing by ).

[0234] The pore volume P of silicon-containing composite particles is the sum of the pore volume into which gas can enter and the pore volume into which gas cannot enter. The Gurwich gas-intolerant pore volume of silicon-containing composite particles can be determined by gas adsorption measurement using nitrogen in accordance with DIN66134.

[0235] The pore volume to which gas can penetrate in silicon-containing composite particles is given by the following formula: The pore volume into which gas can enter = (1 / density of pure substance) - (1 / density of framework) This can be determined by [the method described].

[0236] Here, the pure substance density of silicon-containing composite particles is the theoretical density that can be calculated from the sum of the theoretical pure substance densities of the components contained in the silicon-containing composite particles multiplied by their respective weight-based fractions in the entire material. Therefore, for example, in the case of silicon-containing composite particles in which silicon is deposited on porous particles, it is as follows. Pure matter density = (Theoretical pure matter density of silicon × Fraction of silicon (weight %)) + (Theoretical pure matter density of porous particles × Fraction of porous particles (weight %))

[0237] Data on the density of pure materials can be obtained by those skilled in the art, for example, from the ceramic data portal of the U.S. National Institute of Standards and Technology (NIST, https: / / srdata.nist.gov / CeramicDataPortal / scd). For example, the density of pure carbon is 2.2-2.3 g / m³. 3 The pure substance density of silicon dioxide is 2.203 g / cm³. 3 The pure substance density of boron nitride is 2.25 g / cm³. 3 The pure substance density of silicon nitride is 3.44 g / cm³. 3 The pure substance density of silicon carbide is 3.21 g / cm³. 3 That is the case.

[0238] The pore volume P of the silicon-containing composite particles is preferably in the range of 0 to 400 volume%, more preferably in the range of 100 to 350 volume%, and even more preferably in the range of 200 to 350 volume%, based on the volume of silicon contained in the silicon-containing composite particles and obtained by the deposition of a silicon-containing precursor.

[0239] The pores in the silicon-containing composite particles may be both gas-penetrating and gas-impermeable. The ratio of the volume of gas-penetrating pores to the volume of gas-impermeable pores in the silicon-containing composite particles is generally within the range of 0 (no gas-penetrating pores) to 1 (all pores are gas-penetrating). Preferably, the ratio of the volume of gas-penetrating pores to the volume of gas-impermeable pores in the silicon-containing composite particles is within the range of 0 to 0.8, more preferably within the range of 0 to 0.3, and particularly preferably within the range of 0 to 0.1.

[0240] The pores of silicon-containing composite particles may have any desired diameter, for example, in the range of macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm). Silicon-containing composite particles can also contain any desired mixture of different pore types. Based on the total pore volume, silicon-containing composite particles preferably contain up to 30% macropores, silicon-containing composite particles that do not contain macropores are particularly preferred, and silicon-containing composite particles having at least 50% of pores with an average pore diameter of less than 5 nm based on the total pore volume are very particularly preferred. Silicon-containing composite particles particularly preferably have pores with a maximum diameter of 2 nm.

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

[0242] The silicon-containing composite particles preferably contain a silicon layer having a thickness of less than 1000 nm, more preferably less than 100 nm, and very preferably less than 5 nm (determination method: scanning electron microscope (SEM) and / or high-resolution transmission electron microscope (HR-TEM)). The silicon-containing composite particles may also contain silicon in the form of particles. The silicon particles preferably have a diameter of up to 1000 nm, more preferably less than 100 nm, and very preferably less than 5 nm (determination method: scanning electron microscope (SEM) and / or high-resolution transmission electron microscope (HR-TEM)). The numerical values ​​for silicon particles here are preferably based on the diameter of the circle around the particle in the microscope image.

[0243] Silicon-containing composite particles can reach up to 50m 2 / g, preferably 30m 2 Less than / g, particularly preferably 10m 2 It has a specific surface area of ​​less than / g. The BET specific surface area is determined according to DIN 66131 (using nitrogen). Therefore, when silicon-containing composite particles are used as the active material for the negative electrode of a lithium-ion secondary battery, the generation of SEI can be suppressed and the initial Coulomb efficiency can be improved.

[0244] The silicon in the silicon-containing composite particles deposited from the silicon-containing precursor may further contain one or more dopants selected from the group consisting of, for example, Li, Fe, Al, Cu, Ca, K, Na, S, Cl, Zr, Ti, Pt, Ni, Cr, Sn, Mg, Ag, Co, Zn, B, P, Sb, Pb, Ge, Bi, and rare earth elements. Here, lithium and / or tin are preferred. The amount of dopant in the silicon-containing composite particles is preferably up to 1% by weight, more preferably up to 100 ppm, based on the total weight of the silicon-containing composite particles, which can be determined by ICP-OES.

[0245] Silicon-containing composite particles generally exhibit remarkably high stability under compressive and / or shear loading. The pressure and shear stability of silicon-containing composite particles is demonstrated, for example, by the lack or virtually absent change in the porous structure of the silicon-containing composite particles in SEM under compressive loads (e.g., during electrode molding) and shear loads (e.g., during electrode preparation), respectively.

[0246] The silicon-containing composite particles may optionally further contain elements such as carbon. The carbon is preferably present in the form of a thin layer with a thickness of up to 1 μm, preferably less than 100 nm, more preferably less than 5 nm, and very preferably less than 1 nm (determinable via SEM or HR-TEM). These carbon layers may be present both within the pores and on the surface of the silicon-containing composite particles. The order and number of different layers in the silicon-containing composite particles by the corresponding repetitions of phases 2-6 are also arbitrary. Thus, first, a layer of a different material, such as carbon, may exist on the porous particles, and this layer may constitute the silicon layer or the silicon particle layer. Furthermore, regardless of whether a further layer of a different material exists between the porous particles and the silicon layer or silicon particle layer, a layer of a different material may exist on the silicon layer or silicon particle layer, which may be the same as the material of the porous particles. The process of the present invention proves particularly advantageous because the repetitions of phases 2-6 can be continued directly without interruption by opening the batch pressure reactor.

[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 additive elements. The weight percentage values ​​are based on the total weight of the silicon-containing composite particles. In alternative embodiments, the silicon-containing composite particles do not contain additional elements.

[0248] In a second aspect of the present invention, a composition comprising or consisting of particulate materials, i.e., silicon-containing composite particles, which can be obtained by a process according to the present invention, is provided. In particular, a composition is provided comprising silicon-containing composite particles obtained by a process according to the present invention and at least one other component selected from (i) a binder; (ii) a conductive additive; and (iii) additional particulate electroactive materials. A composition according to the second aspect of the present invention is useful as an electrode composition and can therefore be used to form an active layer of an electrode.

[0249] The composition may be a hybrid electrode composition comprising silicon-containing composite particles and at least one additional particulate electroactive material. Examples of additional particulate electroactive materials 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 hybrid electrode 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, based on the total dry weight of the composition, of silicon-containing composite particles.

[0251] At least one additional particulate electroactive material is preferably present in an amount of 20-95% by weight, 25-90% by weight, or 30-75% by weight of the at least one additional particulate electroactive material.

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

[0253] D 10The particle size is preferably at least 5 μm, more preferably at least 6 μm, more preferably at least 7 μm, more preferably at least 8 μm, more preferably at least 9 μm, and still more preferably at least 10 μm.

[0254] D 90 The particle size is preferably up to 100 μm, more preferably up to 80 μm, more preferably up to 60 μm, 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-containing particles, graphite particles and / or hard carbon particles, wherein the graphite particles and hard carbon particles are in the range of 10 to 50 μm. 50 The particles have a particle size. More preferably, at least one additional particulate electroactive material is selected from graphite particles, and the graphite particles are in the range of 10 to 50 μm. 50 It has a particle size.

[0256] The composition may also be a non-hybrid (or “highly packed”) electrode composition that is substantially free of additional particulate electroactive material. In this context, the term “substantially free of additional particulate electroactive material” should be interpreted as the composition containing 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 that can insert and release metal ions during charging and discharging of the battery) based on the total dry weight of the composition.

[0257] This type of "highly packed" electrode composition preferably contains, based on the total dry weight of the composition, 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, silicon-containing composite particles obtained according to the process of the present invention.

[0258] The composition may optionally contain a binder. The binder functions to adhere the composition to the current collector and to maintain the integrity of the composition. Examples of binders that may be used according to the present invention include polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, carboxymethylcellulose (CMC), modified carboxymethylcellulose (mCMC), sodium carboxymethylcellulose (Na-CMC), polyvinyl alcohol (PVA), alginates and their alkali metal salts, styrene-butadiene rubber (SBR), and polyimide. The composition may also contain a mixture of binders. Preferably, the binder 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] The binder may preferably be present in an amount of 0.5 to 20% by weight, preferably 1 to 15% by weight, preferably 2 to 10% by weight, and most preferably 5 to 10% by weight, based on the total dry weight of the composition.

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

[0261] The composition may optionally contain one or more conductive additives. Preferred conductive additives are non-electroactive materials included to improve electrical 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, Ketjenblack, metal fibers, metal powders, and conductive metal oxides. Preferred conductive additives include carbon black and carbon nanotubes.

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

[0263] In a third aspect, the present invention provides an electrode comprising silicon-containing composite particles obtained by a process according to the present invention, which electrically contacts a current collector. The particulate material used to manufacture the electrode according to the third aspect of the present invention may be in the form of a composition according to the second aspect of the present invention.

[0264] As used herein, the term "current collector" refers to any conductive substrate capable of carrying electric 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 having a thickness between 3 and 500 μm. The particulate material of the present invention can be applied to one or both sides of a current collector to a thickness preferably between 10 μm and 1 mm, for example, between 20 and 500 μm, or between 50 and 200 μm.

[0265] An electrode according to a third aspect of the present invention can be manufactured by forming a slurry by combining the silicon-containing composite particles of the present invention with a solvent and optionally one or more viscosity-modifying additives. The slurry is then cast onto the surface of a current collector, the solvent is removed, and an electrode layer is formed on the surface of the current collector. Further steps such as heat treatment to harden the binder and calendering of the electrode layer can be carried out as appropriate. The electrode layer preferably 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, and preferably 20 μm to 50 μm.

[0266] Alternatively, the slurry can be formed into a self-supporting film or mat containing the particulate matter of the present invention by, for example, casting it onto a suitable casting template, removing the solvent, and then removing the casting template. The resulting film or mat is in the form of cohesive, self-supporting clumps and may then be adhered to a current collector by known methods.

[0267] An electrode according to a third aspect of the present invention can be used as the negative electrode of a metal-ion battery. Accordingly, in a fourth aspect, the present invention provides a rechargeable metal-ion battery comprising a negative electrode including the above-described electrode, a positive electrode including a positive electrode active material capable of releasing and reabsorbing metal ions, and an electrolyte between the negative electrode and the positive electrode.

[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 positive electrode active material is capable of releasing and reabsorbing lithium ions.

[0269] The positive electrode active material is preferably a metal oxide composite. Examples of suitable positive electrode active materials include LiCoO2, 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 Ni 0.2 O2, LiCo 0.82 Ni 0.18 O2, LiCo 0.8 Ni 0.15 Al 0.05 O2, LiLiLi 0.4 Co 0.3 Mn 0.3 O2 and LiNi 0.33 Co 0.33 Mn 0.34 Examples include O2. The positive electrode current collector is generally 3 to 500 μm thick. Examples of materials that can be used as a positive electrode current collector include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0270] The electrolyte is preferably a non-aqueous electrolyte containing a metal salt, such as a lithium salt, and is 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, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methylformate, methyl acetate, triester phosphate, trimethoxymethane, sulfolane, methylsulfolane, and 1,3-dimethyl-2-imidazolidinone.

[0271] Examples of organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, sulfurized polyesters, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociation groups.

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

[0273] Lithium salts are preferably soluble in a selected solvent or 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, the metal-ion battery preferably includes a separator interposed between the negative and positive electrodes. The separator is typically made of an insulating material having high ion permeability and high mechanical strength. The separator typically has a pore size of 0.01 to 100 μm and a thickness of 5 to 300 μm. A suitable example of an electrode separator is a microporous polyethylene film.

[0275] The separator may be replaced by a polymer electrolyte material, in which case the polymer electrolyte material is present in both the composite negative electrode layer and the composite positive electrode layer. The polymer electrolyte material may be a solid polymer electrolyte or a gel-type polymer electrolyte. [Examples]

[0276] The following examples are helpful for further illustrating the invention described herein.

[0277] The analytical methods and equipment used for characterization are as follows:

[0278] Scanning electron microscope (SEM / EDX): Microscopic analysis was performed using a Zeiss Ultra 55 scanning electron microscope and an Oxford X-Max 80N energy-dispersive X-ray spectrometer. Prior to analysis, carbon vapor deposition treatment was performed using a Safematic Compact Coating Unit 010 / HV to prevent charging phenomena. Cross-sections of silicon-containing composite particles were prepared using a Leica TIC 3X ion cutter at 6kV.

[0279] Inorganic analysis / elemental analysis: The C content reported in the examples was confirmed using a Leco CS 230 analyzer. The O, and, where necessary, N and H content was determined using a Leco TCH-600 analyzer. Qualitative and quantitative analysis of other reported elements was performed using inductively coupled plasma emission spectrometry (ICP-OES) (Optima 7300 DV, Perkin Elmer). For this analysis, samples were subjected to acid decomposition (HF / HNO3) using a microwave (Microwave 3000, Anton Paar). ICP-OES measurements followed 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)” and were used for the analysis of acidic aqueous solutions (e.g., drinking water, wastewater, other acidified water samples, aqua regia extracts from soil and sediments).

[0280] Particle size measurement In the context of this invention, the particle size distribution was determined by static laser scattering using a Horiba LA 950 in accordance with ISO 13320. During sample preparation, particular care must be taken to ensure the dispersion of particles in the measurement solution, so as not to measure the size of aggregates rather than the size of individual particles. For measurement, the particles were dispersed in ethanol. Therefore, the dispersion before measurement was treated with 250W ultrasound for 4 minutes using a Hielscher Model UIS250v ultrasonic apparatus and LS24d5 sonotrode, as needed.

[0281] Measurement of BET surface area: The specific surface area of ​​the material was measured using the BET method (determination according to DIN ISO 9277:2003-05 using nitrogen) via gas adsorption with nitrogen, using either a Sorptomatic 199090 instrument (Porotec) or a SA-9603MP instrument (Horiba).

[0282] Skeletal density: The skeletal density, i.e., the density of porous solids based solely on the volume of pore spaces into which gases can enter from the outside, was determined by He pycnometry according to DIN 66137-2.

[0283] Gurwich's gas-penetrating pore volume: The gas-penetrating pore volume of Gurwich was determined by gas adsorption measurement using nitrogen, in accordance with DIN 66134.

[0284] PD 50 Pore ​​size: PD 50 The pore diameter was calculated as the volume-based central pore diameter from the total volume of micropores defined by the Horvath-Kawazoe method according to DIN66135 and mesopores defined by the BJH method according to DIN66134.

[0285] The materials and equipment used in conducting the experimental examples are as follows:

[0286] The autoclaves used consisted of a cylindrical base (beaker) and a lid equipped with numerous connections (e.g., gas supply, gas removal, temperature measurement, pressure measurement). The autoclave volumes were 594 ml (AK1), 312 ml (AK2), and 5300 ml (AK3). The autoclaves were electrically heated. The stirrer used was a helical stirrer with very close clearance. The height of this stirrer was approximately 50% of the clear height inside the reactor. This helical stirrer was designed to allow for direct temperature measurement at the floor.

[0287] The SiH4 used was grade 4.0 and was obtained from Linde GmbH.

[0288] Porous particles used: Porous particles 1-6 are porous carbon, porous particle 7 is porous silicon oxide, and porous particle 8 is porous boron nitride.

[0289] Table 1 reproduces the composition and specific properties of the porous particles 1-8 used.

[0290] Examples 1 to 23 Production of silicon-containing composite particles using monosilane SiH4 as a silicon-containing precursor: Table 2 summarizes the values ​​for parameters A-L, porous particle material number X, and autoclave type. In Phase 1, an autoclave was filled with a porous material X in an amount of Ag, and then closed, where K is the amount of porous particles charged per liter of reactor volume. In Phase 2, the autoclave was first evacuated. Next, Bg of SiH4 was added to a pressure of C bar, where L is the amount of Si charged per liter of reactor volume. In Phase 3, the autoclave was heated to a temperature of E°C within D minutes, and in Phase 4, the temperature was maintained for F minutes. For the first G minutes of the total heating time (D+F), the pressure increase was as shown in Equation 1. During Phase 4, the pressure increased to H bar according to Equation 2. In Phase 5, the autoclave was cooled to room temperature over 12 hours. After this cooling, a pressure of I bar remained inside the autoclave. In Phase 6, the pressure inside the autoclave was reduced to 1 bar, and then the autoclave was purged five times with nitrogen, five times with dilute air with an oxygen fraction of 5%, five times with dilute air with an oxygen fraction of 10%, and then five times with air. In Phase 7, Jg of silicon-containing composite particles were isolated in the form of fine black solids.

[0291] The analytical data obtained for the silicon-containing composite particles are summarized in Table 3. Electrochemical cells based on selected examples of the obtained silicon-containing composite particles were manufactured according to Example 29. The electrochemical properties of the silicon-containing composite particles are similarly described in Table 3.

[0292] [Table 1]

[0293] Table 2 Parameters for Examples 1-23 (nd means measurement was not possible for technical reasons) [Table 2]

[0294] Example 24 Manufacturing of silicon-containing composite particles through the repetition of phases 2 to 6: In Phase 1, 5.0 g of porous material 1 was packed into an autoclave (AK2) and closed, with a charge rate of 50 g of porous particles per liter of reactor volume. In Phase 2, the autoclave was evacuated and 7 g of monosilane SiH4 was charged (to 12 bar), with a charge rate of 19.63 g of Si per liter of reactor volume. In Phase 3, the autoclave was heated to 420°C over 65 minutes. Up to this point, the pressure increase followed Equation 1. In Phase 4, this temperature was maintained for 180 minutes, during which time the pressure increased to 68 bar according to Equation 2. In Phase 5, the autoclave was cooled to 20°C over 600 minutes. In Phase 6, after the reactor pressure was reduced to 1 bar by the release of the gaseous reactor contents, the pressure was further reduced to 1 millibar in Phase 2, and 7 g of SiH4 was again charged into the autoclave (12 bar), where the Si charge rate was 19.63 g per liter of reactor volume. Then, in the second Phase 3, the autoclave was heated to 450°C over 70 minutes, and in the second Phase 4, this temperature was maintained for 240 minutes, during which time the pressure was increased to 50 bar according to Equation 2. In the final iteration of Phase 6, the pressure inside the autoclave was reduced to 1 millibar, and the autoclave was cooled to 30°C over 600 minutes, after which the gas space of the autoclave was purged five times with nitrogen, five times with dilute air with an oxygen fraction of 5%, five times with dilute air with an oxygen fraction of 10%, and then five times with air. In Phase 7, 12.5 g of silicon-containing composite particles were isolated from the reactor in the form of a fine black powder.

[0295] The analysis data for the obtained silicon-containing composite particles is summarized in Table 3.

[0296] The silicon-containing composite particles were electrochemically characterized in the cell according to Example 29, and their specifications are similarly described in Table 3.

[0297] Example 25 Manufacturing of silicon-containing composite particles through the repetition of phases 2 to 6: In Phase 1, an autoclave (AK3) was filled with 69 g of porous material 1 and closed, with a charge rate of 40.7 g of porous particles per liter of reactor volume. In Phase 2, the autoclave was first evacuated, and then SiH4 was charged at 300°C (9.5 bar), with a charge rate of 6.8 g of Si per liter of reactor volume. In Phase 3, the autoclave was heated to 420°C over 15 minutes. Up to this point, the pressure increase followed Equation 1. In Phase 4, this temperature was maintained for 30 minutes, during which time the pressure increased to 38 bar according to Equation 2. In Phase 6, after the reactor pressure decreased to 1 bar due to the release of gaseous reactor contents, the pressure decreased to 1 millibar in a further Phase 2, and SiH4 was again charged into the autoclave (11 bar), with a charge rate of 7.9 g of Si per liter of reactor volume. In the second Phase 3, the autoclave was heated to 450°C over 70 minutes, and in the second Phase 4, this temperature was maintained for 30 minutes, during which time the pressure was increased to 23 bar according to Equation 2. In the final iteration of Phase 6, the pressure inside the autoclave was reduced to 1 millibar, and the autoclave was cooled to 30°C over 600 minutes. The gas space inside the autoclave was then purged five times with nitrogen, five times with dilute air with an oxygen fraction of 5%, five times with dilute air with an oxygen fraction of 10%, and then five times with air. In Phase 7, 140 g of silicon-containing composite particles were isolated from the reactor in the form of a fine black powder.

[0298] The analysis data for the obtained silicon-containing composite particles is summarized in Table 3.

[0299] The silicon-containing composite particles were electrochemically characterized in the cell according to Example 29, and their specifications are similarly described in Table 3.

[0300] Example 26 Manufacturing of silicon-containing composite particles by repeating phases 2 to 6 multiple times: In Phase 1, 180 g of porous material 1 was packed into the autoclave (AK3), and it was closed when the amount of porous particles charged was 106.1 g per liter of reactor volume. In Phase 2, the autoclave was evacuated, and then SiH4 was charged at a temperature of 370°C (9.5 bar), where the amount of Si charged was 7.1 g per liter of reactor volume. In Phase 3, the autoclave was heated to 420°C over 10 minutes. Up to this point, the pressure increase followed Equation 1. In Phase 4, this temperature was maintained for 30 minutes, during which time the pressure increased to 24 bar according to Equation 2. In Phase 6, the reactor pressure was reduced to 1 bar by releasing the gaseous reactor contents, and then the pressure was further reduced to 1 millibar in Phase 2, and SiH4 was again charged into the autoclave (9.5 bar), where the amount of Si charged was 5.6 g per liter of reactor volume. In the second phase 3, the autoclave was heated to 420°C over 10 minutes, and in the second phase 4, this temperature was maintained for 30 minutes, during which the pressure rose to 22 bar according to Equation 2. In the second phase 6, the reactor pressure was reduced to 1 bar by releasing the gaseous reactor contents, and then the pressure was reduced to 1 millibar in the third phase 2, and SiH4 was charged back into the autoclave at 400°C (9.5 bar), with a Si charge rate of 5.6 g per liter of reactor volume. In the third phase 3, the autoclave was heated to 420°C over 10 minutes, and in the third phase 4, this temperature was maintained for 30 minutes, during which the pressure rose to 20 bar according to Equation 2. In Phase 6, the reactor pressure was reduced to 1 bar by releasing the gaseous reactor contents, then the pressure was reduced to 1 millibar in the fourth Phase 2, and SiH4 was recharged into the autoclave at 400°C (11 bar), with a Si charge of 6.4 g per liter of reactor volume. In the fourth Phase 3, the autoclave was heated to 420°C over 10 minutes, and in the fourth Phase 4, this temperature was maintained for 30 minutes, during which time the pressure rose to 23 bar according to Equation 2.In Phase 6, after reducing the reactor pressure to 1 bar by releasing the gaseous reactor contents, the pressure was reduced to 1 millibar in the fifth Phase 2, and SiH4 was recharged into the autoclave at 400°C (11 bar), with a Si charge rate of 6.4 g per liter of reactor volume. In the fifth Phase 3, the autoclave was heated to 420°C over 10 minutes, and in the fifth Phase 4, this temperature was maintained for 30 minutes, during which time the pressure rose to 23 bar according to Equation 2. In Phase 6, after reducing the reactor pressure to 1 bar by releasing the gaseous reactor contents, the pressure was reduced to 1 millibar in the sixth Phase 2, and SiH4 was recharged into the autoclave at 400°C (11 bar), with a Si charge rate of 7.1 g per liter of reactor volume. In the sixth iteration of Phase 3, the autoclave was heated to 420°C over 10 minutes, and in the sixth iteration of Phase 4, this temperature was maintained for 30 minutes, during which time the pressure was raised to 23 bar according to Equation 2. In the final iteration of Phase 6, the pressure inside the autoclave was reduced to 1 millibar, and after the autoclave was cooled to 30°C over 600 minutes, the gas space inside the autoclave was purged five times with nitrogen, five times with dilute air with an oxygen fraction of 5%, five times with dilute air with an oxygen fraction of 10%, and then five times with air. In Phase 7, 376 g of silicon-containing composite particles were isolated from the reactor in the form of a fine black powder.

[0301] The analysis data for the obtained silicon-containing composite particles is summarized in Table 3.

[0302] The silicon-containing composite particles were electrochemically characterized in the cell according to Example 29, and their specifications are similarly described in Table 3.

[0303] Example 27 Production of silicon-containing composite particles involving multiple repetitions of phases 2 to 6 and reaction control by reactor pressure: In Phase 1, 180 g of porous material 1 was packed into the autoclave (AK3), and it was closed when the amount of porous particles charged was 106.1 g per liter of reactor volume. In Phase 2, the autoclave was evacuated, and SiH4 was charged at a temperature of 370°C (9.5 bar), where the amount of Si charged was 7.1 g per liter of reactor volume. In Phase 3, the autoclave was heated to 420°C over 10 minutes. Up to this point, the pressure increase followed Equation 1. In Phase 4, this temperature was maintained for 30 minutes, during which time the pressure increased to 24 bar according to Equation 2. In Phase 6, after reducing the reactor pressure to 1 bar by releasing the gaseous reactor contents, the pressure was reduced to 1 millibar in a second Phase 2, and SiH4 was again charged into the autoclave at 400°C (9.5 bar), where the amount of Si charged was 6.1 g per liter of reactor volume. In the second Phase 3, the autoclave was heated to 420°C over 10 minutes, and in the second Phase 4, this temperature was maintained for 30 minutes, during which the pressure rose to 21 bar according to Equation 2. In Phase 6, the reactor pressure was reduced to 1 bar by releasing the gaseous reactor contents, and then the pressure was reduced to 1 millibar in the third Phase 2, and SiH4 was again charged into the autoclave at 400°C (9.5 bar), where the amount of Si charged was 6.1 g per liter of reactor volume. In the third Phase 3, the autoclave was heated to 420°C over 10 minutes, and in the third Phase 4, this temperature was maintained for 30 minutes, during which the pressure rose to 20 bar according to Equation 2. In Phase 6, the reactor pressure was reduced to 1 bar by releasing the gaseous reactor contents, then the pressure was reduced to 1 millibar in the fourth Phase 2, and SiH4 was recharged into the autoclave at 400°C (11 bar), with a Si charge of 7.1 g per liter of reactor volume. In the fourth Phase 3, the autoclave was heated to 420°C over 10 minutes, and in the fourth Phase 4, this temperature was maintained for 30 minutes, during which time the pressure rose to 23 bar according to Equation 2.In Phase 6, after reducing the reactor pressure to 1 bar by releasing the gaseous reactor contents, the pressure was reduced to 1 millibar in the 5th Phase 2, and SiH4 was recharged into the autoclave at 400°C (11 bar), with a Si charge rate of 7.1 g per liter of reactor volume. In the 5th Phase 3, the autoclave was heated to 420°C over 10 minutes, and in the 5th Phase 4, this temperature was maintained for 30 minutes, during which time the pressure rose to 23 bar according to Equation 2. In Phase 6, after reducing the reactor pressure to 1 bar by releasing the gaseous reactor contents, the pressure was reduced to 1 millibar in the 6th Phase 2, and SiH4 was recharged into the autoclave at 400°C (11 bar), with a Si charge rate of 7.1 g per liter of reactor volume. In the sixth phase 3, the autoclave was heated to 420°C over 10 minutes. In the sixth phase 4, this temperature was maintained for 30 minutes, during which time the pressure rose to 23 bar according to Equation 2. In phase 6, the reactor pressure was reduced to 1 bar by releasing the gaseous reactor contents. Then, in the seventh phase 2, the pressure was reduced to 1 millibar, and SiH4 was recharged into the autoclave at 400°C (11 bar), with a Si charge of 7.1 g per liter of reactor volume. In the seventh phase 3, the autoclave was heated to 420°C over 10 minutes. In the seventh phase 4, after 20 minutes, the recorded pressure increase over time had decreased significantly. The low steepness of the pressure curve indicated a small surface area of ​​the material, so the experiment was stopped at a pressure of 22.5 bar, and the pressure inside the autoclave was reduced to 1 millibar. After cooling the autoclave to 30°C over 600 minutes, the autoclave's gas chamber was purged five times with nitrogen, five times with dilute air with an oxygen fraction of 5%, five times with dilute air with an oxygen fraction of 10%, and then five times with air. In Phase 7, 439 g of silicon-containing composite particles were isolated from the reactor in the form of a fine black powder.

[0304] The analysis data for the obtained silicon-containing composite particles is summarized in Table 3.

[0305] The silicon-containing composite particles were electrochemically characterized in the cell according to Example 29, and their specifications are similarly described in Table 3.

[0306] Example 28 Manufacturing of silicon-containing composite particles with in-situ carbon coating: In Phase 1, an autoclave (AK2) was filled with 8 g of porous material 1 and closed, with a charge rate of 80.1 g of porous particles per liter of reactor volume. In Phase 2, the autoclave was first evacuated, and then SiH4 was charged (to 16 bar), with a charge rate of 7.1 g of Si per liter of reactor volume. In Phase 3, the autoclave was heated to 420°C over 40 minutes. Up to this point, the pressure increase followed Equation 1. In Phase 4, this temperature was maintained for 170 minutes, during which time the pressure increased to 85 bar according to Equation 2. In Phase 5, the autoclave was cooled to 20°C over 600 minutes. In Phase 6, after the reactor pressure decreased to 1 bar due to the release of gaseous reactor contents, the pressure decreased to 1 millibar in a second Phase 2, and 2 g of liquid styrene was charged into the autoclave. In the second Phase 3, the autoclave was heated to 650°C over 90 minutes, and in the second Phase 4, this temperature was maintained for 120 minutes. In Phase 6, the pressure inside the autoclave was reduced to 1 bar, and then purged five times with nitrogen, five times with dilute air with an oxygen fraction of 5%, five times with dilute air with an oxygen fraction of 10%, and then five times with air. In Phase 7, 17.3 g of silicon-containing composite particles were isolated from the reactor in the form of a fine black powder.

[0307] The analysis data for the obtained silicon-containing composite particles is summarized in Table 3.

[0308] The silicon-containing composite particles were electrochemically characterized in the cell according to Example 29, and their specifications are similarly described in Table 3.

[0309] Example 29 Electrochemical property evaluation of silicon-containing composite particles for use as active materials in the negative electrode of lithium-ion batteries: 29.71 g of polyacrylic acid (dried to a constant weight at 85°C; Sigma-Aldrich, Mw ~ 450,000 g / mol) and 756.6 g of deionized water were shaken for 2.5 hours using a shaker (290 rpm) until the polyacrylic acid was completely dissolved. Lithium hydroxide monohydrate (Sigma-Aldrich) was partially added to the solution until the pH reached 7.0 (measured using a WTW pH 340 ipH meter with a SenTix RJD probe). Subsequently, 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), followed by further mixing using a shaker for 4 hours. Next, 3.40 g of each silicon-containing composite particle from Examples 1, 6, 7, 9, 10, 11, 22, 23, 27, or 30 was stirred at 2000 rpm for 1 minute. Then, 1.21 g of an 8% dispersion of conductive carbon black and 0.8 g of deionized water were added and incorporated into a planetary mixer at 2000 rpm. The dispersion was carried out in a dissolver at 3000 rpm at a constant temperature of 20°C for 30 minutes. This ink was then degassed again in a planetary mixer at 2500 rpm under reduced pressure for 5 minutes. The completed dispersion was then coated onto a copper foil (Schlenk Metallfolien, SE-Cu58) with a thickness of 0.03 mm using a film applicator frame (Erichsen, Model 360) with a gap height of 0.1 mm. The negative electrode coating thus produced was then dried at 50°C for 60 minutes under an air pressure of 1 bar. The average basis weight of the dried negative electrode coating is 1.9 mg / cm². 2 The coating density is 0.9 g / cm³. 3 That was the case.

[0310] Electrochemical studies were conducted using a two-electrode button cell battery (CR2032 type, Hosen Corporation). Electrode coatings were used as the counter or negative electrode (Dm=15mm) and based on a lithium nickel manganese cobalt oxide 6:2:2 coating (content 94.0%, average basis weight 15.9 mg / cm²). 2A glass fiber filter paper (Whatman, GD type D) impregnated with 60 μl of electrolyte was used as the working electrode or positive electrode (Dm=15 mm). A glass fiber filter paper (Whatman, GD type D) impregnated with 60 μl of electrolyte was used as the separator (Dm=16 mm). The electrolyte was a 1:4 (v / v) mixture of fluoroethylene carbonate and diethyl carbonate with 1.0 mol of lithium hexafluorophosphate dissolved in it. The cell was assembled in a glove box (<1 ppm H2O, O2). The moisture content in the dry mass of all components used was less than 20 ppm.

[0311] Electrochemical tests were performed at 20°C. The cells were charged using the cc / cv (constant current / constant voltage) method, with a constant current of 5 mA / g (equivalent to C / 25) in the first cycle and 60 mA / g (equivalent to C / 2) in subsequent cycles. After reaching a voltage limit of 4.2V, charging was continued at a constant voltage until the current dropped to less than 1.2 mA / g (equivalent to C / 100) or 15 mA / g (equivalent to C / 8). The cells were discharged using the cc (constant current) method, with a constant current of 5 mA / g (equivalent to C / 25) in the first cycle and 60 mA / g (equivalent to C / 2) in subsequent cycles, until reaching a voltage limit of 2.5V. The selected specific current was based on the weight of the positive electrode coating. The ratio of the cell's charging capacity to its discharging capacity is called the Coulomb efficiency. The electrodes were selected so that the positive-to-negative electrode capacity ratio was 1:1.2.

[0312] Table 3 shows the results of electrochemical tests on full cells of lithium-ion batteries containing the active materials of Examples 1, 6, 7, 9, 10, 11, 22, 23, 27, or 30.

[0313] Comparative Example 30 Manufacturing of silicon-containing composite particles

[0314] 2.2 g of porous particles 1 were introduced into a 1 L tubular reactor, and the reactor was closed. The reactor was then heated to 410°C and passed through with a 10% SiH4 gas stream in nitrogen for 5 hours. After cooling, 5.24 g of silicon-containing composite particles were isolated in the form of a black powder.

[0315] The resulting product had a silicon content of 56% by mass (ICP) and a surface area of ​​9 m². 2 / g, density 2.16g / cm 3 (He pycnometry) The oxygen content was 8.76% by mass.

[0316] Electrochemical tests were performed on a full cell of the lithium-ion battery according to Example 29. The corresponding results are similarly listed in Table 3. [Brief explanation of the drawing]

[0317] [Figure 1] Figure 1 shows a SEM micrograph of a cross-section of the silicon-containing composite particles of Example 1.

[0318] [Figure 2] Figure 2 shows an SEM micrograph of a cross-section of the silicon-containing composite particles of Comparative Example 30.

[0319] In Comparative Example 30, 5.24 g of the material was produced in a reactor with a volume of 1000 ml by a method other than the present invention over a period of 300 minutes (without a heating step). In Example 1, 11.4 g of the material was produced by the method of the present invention in a reactor with a volume of 312 ml over a period of 195 minutes. Accordingly, in Example 1, the yield of the material was 10.7 times greater in relation to time and reactor volume compared to Example 30.

[0320] Furthermore, a comparison of SEM micrographs of the cross-sections of the materials from Example 1 and Comparative Example 30 clearly shows that the material produced in Example 1 has higher homogeneity in terms of interparticle silicon content. This is indicated by the color tone of individual particles in the SEM micrograph. A lighter color tone indicates a higher silicon content relative to all other particles, while a darker color tone indicates a lower silicon content relative to all other particles. If the gray tones of two or more particles are similar, it indicates a similar silicon content. From this, it is clear that silicon-containing composite particles can be obtained much more rapidly by the method of the present invention, and are further characterized by the highly homogeneous deposition of silicon in the pores and on the surface of porous particles, and their stability and electrochemical properties make them particularly suitable for use as an active material for negative electrodes in lithium-ion batteries.

[0321] [Table 3]

Claims

1. A method for producing silicon-containing composite particles, wherein the method comprises the following steps: (a) A step of providing a plurality of porous conductive particles including micropores and / or mesopores, (i) D of the porous conductive particles ５０ The particle size is within the range of 0.5 to 200 μm. (ii) The total pore volume of micropores and mesopores measured by gas adsorption is 0.4 to 2.2 cm³. ３ It is within the range of / g, (iii) PD measured by gas adsorption ５０ The process involves a pore size of 30 nm or less. (b) A step in a batch-type pressure reactor to combine the charge of porous conductive particles with the charge of silicon-containing precursor, wherein the charge of porous conductive particles is such that the reactor volume (cm³) ３ / L ＲＶ ) At least 20 cm per liter ３ The reactor has a volume of (cm³) and the charge of the silicon-containing precursor is located within the reactor volume (cm³). ３ / L ＲＶ ) A process that includes at least 2 g of silicon per liter, (c) A step of heating the reactor to a temperature effective in causing the deposition of silicon into the pores of the porous conductive particles, thereby providing the silicon-containing composite particles, Includes, The batch-type pressure reactor is a moving-bed batch-type pressure reactor. A method wherein the porous particles are stirred during step (c).

2. The method according to claim 1, wherein the moving bed batch pressure reactor is selected from a moving reactor, a reactor having a moving stirring element, a gas passage reactor, or a combination thereof.

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

4. The method according to claim 1, wherein the batch pressure reactor has a moving stirring element.

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

6. The method according to claim 5, wherein the batch pressure reactor is operated horizontally or vertically.

7. The method according to claim 6, wherein the batch pressure reactor is operated vertically, and the one or more stirring elements are selected from the group consisting of a helical stirrer, a spiral stirrer, and an anchor stirrer.

8. The method according to claim 6, wherein the batch pressure reactor is operated horizontally, and the one or more stirring elements are selected from the group consisting of blades, paddles, blade stirrers, and spiral stirrers.

9. The method according to claim 4, wherein the batch-type pressure reactor is an autoclave reactor equipped with an internal agitator.

10. The method according to claim 9, wherein the autoclave is equipped with a close-clearance helical stirrer.

11. The method according to any one of claims 1 to 10, wherein the pressure in step (c) is at least 200 kPa, or at least 300 kPa, or at least 500 kPa, or 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 claims 1 to 11, wherein the temperature in step (c) is within the range of 300 to 800°C, or 300 to 750°C, or 300 to 700°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.

13. The method according to any one of claims 1 to 12, wherein the batch pressure reactor includes, in addition to the silicon-containing precursor, an inert padding gas or hydrogen.

14. A step of bringing the surface of the deposited silicon into contact with a passivating agent, wherein the silicon is not exposed to oxygen before contact with the passivating agent. The method according to any one of claims 1 to 13, further comprising:

15. The method according to any one of claims 1 to 14, wherein the batch pressure reactor includes an integrated hydrogen selective membrane.

16. The method according to claim 15, wherein the by-product hydrogen gas is discharged from the reactor as the reaction progresses.

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