Method for preparing electroactive composite particles

Abstract

The present invention relates to a method for preparing composite particles. The method includes the steps of: preparing a plurality of porous particles including micropores and / or mesopores; contacting the porous particles with a silicon-containing precursor at a temperature effective to induce the deposition of a plurality of silicon domains within the pores of the porous particles; subjecting the particles to heat treatment at a temperature of at least 400°C in the presence of an inert gas; and contacting the particles with the silicon-containing precursor at a temperature effective to induce the deposition of further silicon domains within the pores of the porous particles.

Description

[Technical Field]

[0001] The present invention relates to a method for preparing composite particles containing silicon deposited in the pores of porous particles. The method of the present invention includes the step of heating the composite particles after silicon deposition. The composite particles are useful as electroactive materials in electrodes of rechargeable metal-ion batteries. In particular, the method of the present invention enables the preparation of composite particles having high electrochemical capacity, which are suitable for use as anode active materials in rechargeable metal-ion batteries. The present invention also relates to novel composite particles prepared by the method of the present invention. [Background technology]

[0002] A lithium-ion battery (LIB) generally comprises an anode, a cathode, and a lithium-containing electrolyte. The anode generally comprises a metal current collector with a layer of electroactive material, as defined herein, a material capable of inserting and releasing lithium ions during charging and discharging of the battery. When an LIB is charged, lithium ions are transported from the cathode through the electrolyte to the anode and inserted into the electroactive material of the anode as inserted lithium atoms. Thus, in this specification, the terms “cathode” and “anode” are used in the sense that the battery is loaded such that the anode becomes the negative electrode. In this specification, the term “battery” is used to refer to both a device containing a single lithium-ion battery and a device containing multiple connected lithium-ion batteries.

[0003] Lithium-ion batteries (LIBs) have been widely applied in portable electronic devices since their development in the 1980s and 1990s. The recent development of electric and hybrid vehicles has created a significant new LIB market, and renewable energy sources are driving further demand for on-grid energy storage, at least part of which can be met by LIB farms. Overall, global LIB production is projected to grow from approximately 290 GWh in 2018 to over 2000 GWh in 2028.

[0004] Alongside the growth in total storage capacity, there is great interest in improving the gravimetric and / or volumetric capacity of rechargeable metal-ion batteries so that the same energy storage can be achieved with smaller battery mass and / or smaller battery volume. Conventional lithium-ion batteries (LIBs) use graphite as the anode electroactive material. A graphite anode can accommodate up to one lithium atom for every six carbon atoms, resulting in a maximum theoretical relative capacity of 372 mAh / g in lithium-ion batteries, although the practical capacity is slightly lower (approximately 340 mAh / g to 360 mAh / g).

[0005] Silicon is a promising alternative to graphite due to its very high capacity relative to lithium (see, for example, Non-Patent Document 1). Silicon has a theoretical maximum specific capacity of approximately 3600 mAh / g in lithium-ion batteries. 15 (Based on Si4). However, due to the high ratio of lithium inserted to silicon, the silicon material expands to 400% of its original volume. Repeated charge-discharge cycles cause significant mechanical stress on the silicon material, leading to fracture and structural failure. Furthermore, charging the anode in a LIB forms a solid electrolyte interface (SEI) layer. This SEI layer is ionically conductive yet insulating, formed by the reductive decomposition of the electrolyte on the exposed electrode surface during the initial charge. In graphite anodes, this SEI layer remains relatively stable during subsequent charge-discharge cycles. However, the expansion and contraction of the silicon anode cause fracture and delamination of the SEI layer, exposing a new silicon surface, which further decomposes the electrolyte, increases the thickness of the SEI layer, and irreversibly consumes lithium. Collectively, these defect mechanisms result in unacceptable electrochemical capacity loss over consecutive charge-discharge cycles.

[0006] The inventors have previously reported the development of electroactive materials of a type having a composite structure in which electroactive materials, such as silicon, are deposited within a pore network of highly porous particles, such as porous carbon materials, having a carefully controlled pore size distribution. For example, Patent Documents 1 and 2 report that the improvement in the electrochemical performance of these materials may be due to the electroactive material forming small domains of several nanometers or less in size within the pore network of porous particles, which function as the framework of the composite particles. The fine electroactive structure is thought to have lower resistance to elastic deformation and higher fracture resistance than larger electroactive structures, and therefore can be lithitated and delithiated without excessive structural stress. As a result, the electroactive material exhibits excellent reversible capacity retention over many charge-discharge cycles. Secondly, by controlling the filling of silicon within the porous carbon framework so that only a portion of the pore volume is occupied by uncharged silicon, the unoccupied pore volume of the porous carbon framework can accommodate a considerable amount of silicon expansion inside. Excessive expansion is suppressed by the particle framework. Furthermore, since only a small portion of the electroactive material surface is accessible to the electrolyte, SEI formation is substantially hindered.

[0007] In Patent Document 3, the applicant reports a further development in which controlling the distribution of electroactive silicon within the pore network of the particle skeleton leads to further improvements in the electrochemical performance of composite particles. Specifically, the applicant has shown that the electrochemical performance is optimized when the length scale of the individual silicon structures in the composite particles is minimized such that a large proportion of silicon atoms are located in the surface region of the silicon structure and a relatively small proportion of silicon atoms are located within the bulky / coarse silicon structure. The applicant has identified an optimized pore structure for the porous particle skeleton and a set of conditions for the deposition of silicon onto the porous particle skeleton. This makes it possible to increase the proportion of this so-called "surface" silicon while ensuring that a large amount of silicon as a whole is incorporated into the composite particles to meet the requirements of the overall volumetric energy density.

[0008] To achieve a commercially attractive balance between silicon content and residual surface area, efficiently depositing silicon into porous particles is difficult without the accumulation of so-called crude silicon. Crude silicon is silicon with a characteristically large length scale because it is deposited within mesopores or on the outer surface of porous particles. In this deposition regime, the silicon domain size can expand indefinitely. Crude silicon can adversely affect the electrochemical performance of composite particles.

[0009] This study found that further improvements to the composite particle structure after silicon deposition can further enhance the electrochemical properties of the composite particles. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] International Publication No. 2020 / 095067 [Patent Document 2] International Publication No. 2020 / 128495 [Patent Document 3] International Publication No. 2022 / 029422 [Non-patent literature]

[0011] [Non-Patent Document 1] Insertion Electrode Materials for Rechargeable Lithium Batteries, Winter, M. et al. in Adv. Mater. 1998, 10, No. 10 [Overview of the Initiative]

[0012] In a first embodiment, the present invention relates to a method for preparing composite particles, (a) A step of preparing a plurality of porous particles including micropores and / or mesopores, (b) A step of bringing porous particles and a silicon-containing precursor into contact at a temperature effective in causing the deposition of multiple silicon domains into the pores of the porous particles, (c) A step of subjecting the particles derived from step (b) to heat treatment at a temperature of at least 400°C in the presence of an inert gas, (d) A step of bringing particles derived from step (c) and a silicon-containing precursor into contact at a temperature effective in causing further deposition of silicon domains into the pores of the porous particles, This provides a method that includes [something].

[0013] The method of the present invention includes, in step (b), the formation of composite particles in which a plurality of silicon domains are deposited within a pore network of porous particles by thermal decomposition of a suitable precursor compound. The composite particles derived from step (b) are then subjected to heat treatment in step (c).

[0014] Without being constrained by theory, it is thought that silicon domains deposited in porous particles can block micropores and mesopores, creating enclosed voids that prevent further silicon deposition within the pores. This is thought to reduce the silicon density in the composite particles and contribute to the formation of crude silicon.

[0015] The silicon domains formed by the thermal decomposition of the silicon-containing precursor are thought to be in the form of nanoclusters of silicon atoms substantially terminated by silicon-hydrogen bonds (Si-H). The heat treatment of the particles in step (c) is thought to promote the removal of hydrogen and form molecular hydrogen (H2). If the silicon domains that are a direct result of step (b) do not contain hydrogen atoms, the silicon domains may be reduced before step (c). Those skilled in the art are aware of suitable methods for reducing silicon domains. The heat treatment in step (c) may also cause the removal of terminal portions other than hydrogen bonded to the silicon surface. The removal of terminal portions such as hydrogen is thought to cause shrinkage of the silicon domains, exposing further pores that were previously blocked by deposited silicon. This increases the porosity of the particles by increasing the pore volume that can accommodate further silicon deposition.

[0016] The increase in particle porosity after the heat treatment process is measurable. Porosity can be measured, for example, using the quenched solid density functional theory (QSDFT) according to the standard methodology specified in ISO 15901-2 and ISO 15901-3, where the relative pressure p / p0 is at least 10 at 77K. -6 This can be directly measured by using nitrogen gas adsorption to measure the total volume of micropores and / or mesopores. The increase in the BET surface area of ​​the treated particles also indicates an increase in the particle's porosity.

[0017] Increasing the porosity of the particles allows for further silicon deposition. In step (d), additional silicon is infiltrated into the exposed pores. The deposition of silicon domains in mesoporous and / or microporous particles is carried out under a kinetically controlled regime that is selective for micropores and fine mesopores due to their relatively high surface area. This avoids silicon deposition outside of micropores and fine mesopores, thereby improving structural control.

[0018] The method of the present invention increases the silicon filling of composite particles, producing a high-density composite in which silicon is preferentially located within the pores of porous particles rather than on the particle surface or within large, accessible open mesopores. In this way, the structure and characteristic length scale of the silicon are better controlled.

[0019] Therefore, the present invention makes it possible to achieve a high composite density while maintaining a low crude silicon value.

[0020] In a second embodiment, the present invention provides a particulate material consisting only of a plurality of composite particles that can be obtained by the method of the first embodiment.

[0021] In a third embodiment, the present invention provides a composition comprising a particulate material according to the second embodiment and at least one other component.

[0022] In a fourth embodiment, the present invention provides an electrode comprising a particulate material according to the second embodiment or a composition according to the third embodiment.

[0023] In a fifth embodiment, the present invention provides a rechargeable metal-ion battery comprising electrodes according to the fourth embodiment. [Brief explanation of the drawing]

[0024] [Figure 1] This graph shows the effect of the heat treatment in step (c) according to the present invention on the total volume of micropores and mesopores of composite particles obtained by chemical vapor phase penetration of silicon into the pores of porous particles. [Modes for carrying out the invention]

[0025] The present invention relates in general to a method for preparing composite particles by depositing multiple silicon domains in a pore network of microporous and / or mesoporous porous particles using the thermal decomposition of a silicon-containing precursor. The porous particles typically function as a silicon skeleton deposited in the form of multiple silicon domains. As used herein, the term “silicon domain” refers to a body of elemental silicon having a maximum dimension determined by the position of silicon within the micropores and / or mesopores of the porous particle. Silicon domains may also be described as nanoscale silicon domains, where the term “nanoscale” is generally understood to refer to dimensions less than 100 nm. However, due to the dimensions of micropores and mesopores, silicon domains typically have a maximum dimension of less than 50 nm, and usually significantly smaller than 50 nm, in any direction. Domains can take the form of, for example, regular or irregular particles or bounded layers or coating regions.

[0026] Porous particles generally consist of a three-dimensionally interconnected network of pores, including micropores and / or mesopores, and optionally a small amount 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 nm to 50 nm, and the term “macropore” is used herein to refer to pores with a diameter greater than 50 nm.

[0027] References herein to the volumes of micropores, mesopores and macropores in porous particles, and also to the pore volume distribution within porous particles, relate to the internal pore volume of porous particles used as a starting material in step (a) of the claimed method, i.e., prior to the deposition of silicon into the pore volume in step (b).

[0028] Porous particles can be characterized by the total volume of micropores and mesopores (i.e., the total pore volume in the pore diameter range of 0 nm to 50 nm). Typically, porous particles contain both micropores and mesopores. However, it is not ruled out that porous particles containing micropores but not mesopores, or conversely, containing mesopores but not micropores, may be used.

[0029] The total volume of micropores and mesopores, as well as 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 at least 10 at 77K. -6This is determined using nitrogen gas adsorption. Nitrogen gas adsorption is a technique for characterizing the porosity and pore diameter distributions of a material by condensing a gas within the pores of a solid. As the pressure is increased, the gas initially condenses in the pores with the smallest diameter, and the pressure is increased until a saturation point is reached where all pores are filled with liquid. Then, the nitrogen gas pressure is gradually decreased to evaporate the liquid from the system. Pore volume and pore diameter distributions can be determined by analyzing the adsorption isotherms and desorption isotherms, as well as the hysteresis between them. Suitable instruments for measuring pore volume and pore diameter distributions by nitrogen gas adsorption include the TriStar II and TriStar II Plus porosity analyzers available from Micromeritics Instrument Corporation in the United States, and the Autosorb IQ porosity analyzer available from Quantachrome Instruments.

[0030] Nitrogen gas adsorption is effective for measuring pore volume and pore size distribution of pores with diameters up to 50 nm, but becomes 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 of 50 nm or less (i.e., only micropores and mesopores). Similarly, PD 50 The value is determined based on the total volume of micropores and mesopores only.

[0031] 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 greater than 50 nm and up to 100 nm can be measured by mercury intrusion, up to 0.3 cm³. 3 Less than / g, or 0.2cm 3 Less than / g, or 0.1cm 3 Less than / g, or 0.05cm 3It is preferably below / g. A small proportion of macropores may be useful for facilitating the access of electrolytes into the pore network, but the advantages of the present invention are substantially obtained by accommodating the electroactive material in micropores and smaller mesopores. Disregard any pore volume measured by mercury intrusion porosimetry at pore sizes of 50 nm or less (as described above, nitrogen adsorption is used to characterize mesopores and micropores). The pore volume measured by mercury intrusion porosimetry above 100 nm is assumed to be the interparticle porosity for the purposes of the present invention, and this pore volume is also disregarded.

[0032] Mercury intrusion porosimetry is a technique for characterizing the porosity and pore diameter distributions of a material by applying various levels of pressure to a sample of the material immersed in mercury. The pressure required to cause mercury to penetrate the pores of the sample is inversely proportional to the pore size. The values obtained by mercury intrusion porosimetry reported herein were obtained in accordance with ASTM UOP578-11 with the surface tension γ of mercury at room temperature being 480 mN / m and the contact angle φ being 140 degrees. The density of mercury at room temperature is 13.5462 g / cm 3 is taken as. Many high-precision mercury intrusion devices are commercially available, such as the AutoPore IV series of automatic mercury intrusion porosimeters available from Micromeritics Instrument Corporation in the United States. For a complete report on mercury intrusion porosimetry, reference can be made to "Analytical Methods in Fine Particle Technology" by P.A. Webb and C. Orr, 1997, Micromeritics Instrument Corporation, ISBN 0-9656783-0.

[0033] It will be understood that intrusion methods such as gas adsorption and mercury intrusion are effective only for determining the pore volume of pores in which nitrogen or mercury can access from outside the porous particle. The porosity values ​​specified herein should be understood to refer to the volume of openings, i.e., pores in which fluid can access from outside the porous particle. Completely enclosed pores that cannot be identified by nitrogen adsorption or mercury intrusion shall not be considered when determining the porosity values ​​herein. Similarly, any pore volume located in pores so small that they fall below the detection limit by nitrogen adsorption shall not be considered.

[0034] The total pore volume of micropores and mesopores in porous particles, as measured by gas adsorption, is at least 0.4 cm³. 3 It may be / g. The total pore volume of micropores and mesopores in porous particles, as measured by gas adsorption, is at least 0.5 cm³. 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 The particle size may be per gram. The use of highly porous particles may be preferable because it allows for the accommodation of a larger amount of electroactive material within the pore volume.

[0035] The internal pore volume of porous particles is appropriately limited to a value where the increased fragility of the particle structure outweighs the benefit of increased pore volume in accommodating a larger amount of electroactive material. The total pore volume of micropores and mesopores in porous particles, as measured by gas adsorption, is 2 cm³. 3 Less than / g, or 1.8cm 3 Less than / g, or 1.7cm 3 Less than / g, or 1.6cm 3 Less than / g, or 1.55cm 3 Less than / g, or 1.5cm 3 Less than / g, or 1.45cm 3 Less than / g, or 1.4cm 3 Less than / g, or 1.35cm3 Less than / g, or 1.3cm 3 Less than / g, or 1.25cm 3 Less than / g, or 1.2cm 3 It may be less than / g.

[0036] The total pore volume of micropores and mesopores in porous particles, as measured by gas adsorption, is 0.4 cm³. 3 / g~2cm 3 / g, or 0.4cm 3 / g~1.8cm 3 / g, or 0.4cm 3 / g~1.7cm 3 / g, or 0.5cm 3 / g~1.6cm 3 / g, or 0.5cm 3 / g~1.55cm 3 / g, or 0.6cm 3 / g~1.5cm 3 / g, or 0.6cm 3 / g~1.45cm 3 / g, or 0.65cm 3 / g~1.4cm 3 / g, or 0.65cm 3 / g~1.35cm 3 / g, or 0.7cm 3 / g~1.3cm 3 / g, or 0.7cm 3 / g~1.25cm 3 / g, or 0.75cm 3 / g~1.2cm 3 / g, or 0.75cm 3 / g~1.1cm 3 / g, or 0.8cm 3 / g~1.2cm 3 / g, or 0.8cm 3 / g~1.1cm 3 The range of / g is also acceptable.

[0037] "PD n In this specification, the general term "pore diameter" refers to the pore diameter of the nth percentile on a volume basis relative to the total volume of micropores and mesopores. For example, as used herein, "PD 50The term "pore diameter" refers to the pore diameter below which 50% of the total micropore and mesopore volume is observed. To avoid misunderstanding, any macropore volume (pore diameter greater than 50 nm) is not included in the PD. n This is not considered for the purpose of calculating the value.

[0038] PD of porous particles 90 The pore size may be 30 nm or less, or 25 nm or less, or 20 nm or less, or 15 nm or less, or 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less.

[0039] PD of porous particles 90 The pore size may be at least 3.2 nm, or at least 3.5 nm, or at least 3.8 nm, or at least 4 nm.

[0040] PD of porous particles 90 The pore size may be in the range of 3.2 nm to 30 nm, 3.5 nm to 25 nm, 3.8 nm to 20 nm, or 4 nm to 8 nm.

[0041] PD of porous particles 50 The pore size may be 20 nm or less, or 15 nm or less, or 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less, or 1.5 nm or less.

[0042] The volume fraction of micropores to the total volume of micropores and mesopores in porous particles may be at least 0.4, or at least 0.45, or at least 0.5, or at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7.

[0043] The total pore volume of the micropores and mesopores of the composite particles formed in the final step (d), as measured by gas adsorption, is 0.6 cm³. 3 Less than / g, or 0.5cm 3 Less than / g, or 0.4cm 3Less than / g, or 0.3cm 3 Less than / g, or 0.2cm 3 Less than / g, or 0.1cm 3 It may be less than / g.

[0044] The total pore volume of the micropores and mesopores of the composite particles formed in the final step (d), as measured by gas adsorption, is at least 0.01 cm³. 3 / g is also acceptable.

[0045] 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 size relative to the cumulative total internal pore volume of porous particles. Bimodal or multimodal pore size distributions may be preferred because the proximity of micropores to larger diameter pores provides the advantage of efficient transport of ions through the porous network to the electroactive material.

[0046] As used herein, the term “particle size” refers to the equivalent diameter (ESD), that is, the diameter of a sphere having the same volume as a given particle, where the volume of the particle is understood to include the volume of the pores within the particle. 50 " and "D 50 The term "particle diameter" refers to the median particle diameter on a volume basis, i.e., the diameter below which 50% of the particle population is located. 10 " and "D 10 The term "particle diameter" refers to the median particle diameter of the 10th percentile on a volume basis, i.e., the diameter at which 10% of the particle population is below that diameter. 90 " and "D 90 The term "particle diameter" refers to the median particle diameter of the 90th percentile on a volume basis, i.e., the diameter below which 90% of the particle population is located.

[0047] Particle size and particle size distribution can be determined by standard laser diffraction techniques in accordance with ISO 13320:2009. Laser diffraction is based on the principle that particles scatter light at angles that vary depending on their size, and that the aggregate of particles generates a scattered light pattern defined by intensity and angle that can correlate with the particle size distribution. Many laser diffraction devices are commercially available for the rapid and reliable determination of particle size distribution. Unless otherwise specified, the particle size distribution measurements specified or reported herein were measured using a conventional Malvern Mastersizer™ 3000 particle size analyzer manufactured by Malvern Instruments™. This Malvern Mastersizer™ 3000 particle size analyzer operates by projecting a helium-neon gas laser beam through 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 the intensity of the light is measured at several predetermined angles by a photodetector array. The intensities measured at various 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 volume% of the surfactant SPAN®-40 (sorbitan monopalmitate). A particle refractive index of 2.68 is used for porous particles, and 3.50 for composite particles, with a dispersant refractive index of 1.378. The particle size distribution is calculated using a Mie scattering model.

[0048] Porous particles are D in the range of 1 μm to 30 μm. 50 It may have 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 2.5 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 25 μm or less, or 20 μm or less, or 18 μm or less, or 15 μm or less, or 12 μm or less, or 10 μm or less, or 8 μm or less.

[0049] D of the porous particles 10 The particle diameter is preferably 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. D 10 By maintaining the particle diameter at 0.5 μm or more, the possibility of undesirable aggregation of submicron-sized particles is reduced, and the dispersibility of the composite particles formed is improved.

[0050] D of the porous particles 90 The particle diameter 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.

[0051] The porous particles preferably have a narrow particle size distribution span. For example, the particle size distribution span ((D 90 - D 10 ) / D 50 as defined) is preferably 5 or less, more preferably 4 or less, more preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. By maintaining a narrow particle size distribution span, efficient filling of particles into a dense powder bed can be more easily achieved.

[0052] The composite particles formed in the final step (d) may have a D 50 particle diameter in the range of 1 μm to 30 μm.

[0053] The composite particles formed in the final step (d) may have a D 10 particle diameter of 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.

[0054] The composite particles formed in the final step (d) may have a D 90 particle diameter of 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.

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

number

number

[0056] Porous particles may have an average sphericity greater than 0.5 (as defined above). Preferably, porous particles 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. Preferably, porous particles have an average sphericity of at least 0.90, or at least 0.92, or at least 0.93, or at least 0.94, or at least 0.95. Spherical particles are thought to aid in the uniformity of deposition and promote a higher density packing of the final product when taken into the batch pressure reactor and electrodes.

[0057] As used herein, the term "BET surface area" should be construed to refer to the surface area per unit mass calculated from the measurement of physical adsorption of gas molecules on the surface of a solid using the Brunauer-Emmett-Teller theory and in accordance with ISO 9277.

[0058] The porous particles may have a BET surface area in the range of 100 m 2 / g to 4000 m 2 / g, or 500 m 2 / g to 4000 m 2 / g, or 750 m 2 / g to 3500 m 2 / g, or 1000 m 2 / g to 3250 m 2 / g, or 1000 m 2 / g to 3000 m 2 / g, or 1000 m 2 / g to 2500 m 2 / g, or 1000 m 2 / g to 2000 m 2 / g.

[0059] The composite particles formed in step (c) may have a BET surface area at least 30 m 2 / g, or at least 40 m 2 / g, or at least 50 m 2 / g, or at least 60 m 2 / g, or at least 70 m 2 / g, or at least 80 m 2 / g, or at least 90 m 2 / g, or at least 100 m 2 / g greater than that of the composite particles formed in step (b).

[0060] The composite particles formed in the final step (d) may have a BET surface area of 0.1 m 2 / g to 100 m 2 / g, or 0.1 m 2 / g to 80 m 2 / g, or 0.5 m 2 / g to 60 m 2 / g, or 0.5 m 2 / g to 40 m2 / g, or 1m 2 / g~30m 2 / g, or 1m 2 / g~25m 2 / g, or 2m 2 / g~20m 2 The BET surface area may be in the range of / g. Generally, a low BET surface area is preferred to minimize the formation of a solid electrolyte interface (SEI) layer on the composite particle surface during the first charge-discharge cycle of the anode. However, if the BET surface area is excessively low, the charging speed and capacity will be unacceptably low because a large amount of electroactive material is unable to access the metal ions in the surrounding electrolyte.

[0061] As used herein, the term “particle density” refers to the “apparent particle density” measured by the mercury intrusion method (i.e., particle mass divided by particle volume, where particle volume is interpreted as the sum of the volumes of the solid material and any closed or blocked pores ("closed pores" being pores too small to be measured by the mercury intrusion method)). Porous particles preferably have a density of at least 0.35 g / cm³. 3 And 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 g / cm³, most preferably 0.35 g / cm³ 3 ~1.2g / cm 3 It has a particle density of at least 0.4 g / cm³. The porous particles have a particle density of 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 It is preferable that the porous particles have a particle 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 3The following, or 0.95 g / cm³ 3 The following, or 0.9 g / cm³ 3 It is preferable that the following particle densities be present.

[0062] Porous particles are (i) 0.4cm 3 / g~1.8cm 3 Total pore volume of micropores and mesopores measured by nitrogen gas adsorption in the range of / g, (ii) PD of 10 nm or less 50 PD with a pore size of preferably 20 nm or less 90 Pore ​​diameter, and (iii) D in the range of 1 μm to 30 μm 50 Particle size, It may have.

[0063] Porous particles are (i) 0.5cm 3 / g~1.6cm 3 Total pore volume of micropores and mesopores measured by nitrogen gas adsorption in the range of / g, (ii) PD of 8nm or less 50 PD with a pore size of preferably 15 nm or less 90 Pore ​​diameter, and (iii) D in the range of 1 μm to 25 μm 50 Particle size, It may have.

[0064] Porous particles are (i) 0.6 cm 3 / g~1.5cm 3 Total pore volume of micropores and mesopores measured by nitrogen gas adsorption in the range of / g, (ii) PD of 6nm or less 50 PD with a pore size of preferably 12 nm or less 90 Pore ​​diameter, and (iii) D in the range of 1.5 μm to 20 μm 50 Particle size, It may have.

[0065] Porous particles are (i) 0.65 cm3 / g~1.4cm 3 Total pore volume of micropores and mesopores measured by nitrogen gas adsorption in the range of / g, (ii) PD of 2.5 nm or less 50 PD with a pore size of preferably 10 nm or less 90 Pore ​​diameter, and (iii) D in the range of 1.5 μm to 18 μm 50 Particle size, It may have.

[0066] Porous particles are (i) 0.7cm 3 / g~1.3cm 3 Total pore volume of micropores and mesopores measured by nitrogen gas adsorption in the range of / g, (ii) PD of 4nm or less 50 PD with a pore size of preferably 8 nm or less 90 Pore ​​diameter, and (iii) D in the range of 2 μm to 15 μm 50 Particle size, It may have.

[0067] Porous particles are (i) 0.75 cm 3 / g~1.2cm 3 Total pore volume of micropores and mesopores measured by nitrogen gas adsorption in the range of / g, (ii) PD of 3nm or less 50 PD with a pore size of preferably 6 nm or less 90 Pore ​​diameter, and (iii) D in the range of 2 μm to 12 μm 50 Particle size, It may have.

[0068] Porous particles are (i) 0.8cm 3 / g~1.2cm 3 Total pore volume of micropores and mesopores measured by nitrogen gas adsorption in the range of / g, (ii) PD of 2nm or less 50 PD with a pore size of preferably 5 nm or less 90Pore ​​diameter, and (iii) D in the range of 2.5 μm to 10 μm 50 Particle size, It may have.

[0069] The porous particles may be conductive porous particles. The porous particles may also be conductive porous carbon particles. The use of conductive porous particles is preferable because the porous particles form a conductive framework within the composite particles, which facilitates the flow of electrons between the lithium atoms / ions inserted into the electroactive material and the current collector.

[0070] The conductive porous carbon particles may contain at least 80% by weight of carbon, or at least 85% by weight of carbon, or at least 90% by weight of carbon, or at least 95% by weight of carbon. The carbon may be crystalline carbon, amorphous carbon, or a mixture of amorphous and crystalline carbon. The conductive porous carbon particles may be either hard carbon particles or soft carbon particles.

[0071] As used herein, the term “hard carbon” means carbon atoms that are primarily composed of nanoscale polycyclic aromatic domains sp. 2 This refers to a disordered carbon matrix that takes on a hybrid state (three-way bonding). These polycyclic aromatic domains are cross-linked by chemical bonds, such as COC bonds. Because the polycyclic aromatic domains are chemically cross-linked with each other, hard carbon cannot be converted to graphite at high temperatures. The high G band (approximately 1600 cm⁻¹) in the Raman spectrum... -1 As is evident from the results, hard carbon has graphite-like properties. However, in the Raman spectrum, the high D band (approximately 1350 cm⁻¹) -1 As is evident from the above, carbon is not entirely like graphite.

[0072] As used herein, the term "soft carbon" also refers to carbon atoms that are primarily polycyclic aromatic domains having dimensions in the range of 5 nm to 200 nm. 2This refers to a disordered carbon matrix that exhibits a hybrid state (three-way bonding). In contrast to hard carbon, the polycyclic aromatic domains in soft carbon are bonded by intermolecular forces rather than by chemical bonds. That is, at high temperatures, soft carbon can graphitize. Porous carbon particles preferably have at least 50% sp when measured by XPS. 2 It contains mixed carbon. For example, porous carbon particles preferably contain 50% to 98% sp 2 Hybrid carbon, 55%~95% sp 2 Hybrid carbon, 60%~90% sp 2 Mixed carbon, or 70%-85% sp 2 It can contain hybrid carbon.

[0073] Various different materials can be used to produce suitable porous carbon particles by pyrolysis. Examples of usable organic materials 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 pyrolysis include phenolic resins, novolac resins, pitch, melamine, polyacrylate, polystyrene, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers containing monomer units of acrylate, styrene, α-olefin, vinylpyrrolidone, and other ethylenically unsaturated monomers. Depending on the starting materials and the conditions of the pyrolysis process, various different carbon materials are available in the art. A wide variety of porous carbon particles with different specifications are available from suppliers.

[0074] To increase the volume of mesopores and micropores, porous carbon particles can be subjected to a chemical or gas activation process. A preferred activation process involves contacting the thermally decomposed carbon with one or more of oxygen, steam, CO, CO2, and KOH at a temperature in the range of 600°C to 1000°C.

[0075] Mesopores can also be obtained by known templating processes using extractable pore-forming agents such as MgO and other colloidal or polymer templates, which can be removed by thermal or chemical means after thermal decomposition or activation.

[0076] Alternatives to carbon-based conductive particles include titanium nitride (TiN), titanium carbide (TiC), silicon carbide (SiC), and nickel oxide (NiO x ), titanium silicon nitride (TiSiN), nickel nitride (Ni3N), molybdenum nitride (MoN), titanium oxynitride (TiO2) x N 1-x The porous particles include titanium nitride (TiN), silicon oxycarbide (SiOC), boron nitride (BN), or vanadium nitride (VN). Preferably, the porous particles include titanium nitride (TiN), silicon oxycarbide (SiOC), or boron nitride (BN).

[0077] The composite particles of the present invention are preferably prepared by chemical vapor infiltration (CVI) of a silicon-containing precursor into the pore structure of porous particles. As used herein, CVI refers to the process in which a silicon-containing precursor is thermally decomposed on a surface, forming elemental silicon on the surface and by-products.

[0078] The silicon-containing precursor may be a gaseous silicon-containing precursor. The gaseous silicon-containing precursor in step (b) and / or step (d) may be used in pure form (or substantially pure form) or as a dilution mixture with an inert carrier gas, such as nitrogen or argon. The gaseous silicon-containing precursor in step (b) and / or step (d) may independently contain at least 30 vol% or at least 40 vol% or at least 50 vol% or at least 60 vol% or at least 70 vol% or at least 80 vol% or at least 90 vol% or at least 95 vol% or at least 97 vol% or at least 99 vol% of silicon-containing precursor relative to the total volume of the gas.

[0079] The silicon-containing precursor in step (b) and / or step (d) is independently silane (SiH4), disilane (Si2H6), trisilane (Si3H8), tetrasilane (Si4H 10 ), may be selected from the group consisting of methylsilane, dimethylsilane and chlorosilane, preferably silane (SiH4), disilane (Si2H6), trisilane (Si3H8) and tetrasilane (Si4H 10 A selection may be made from the group consisting of ). A particularly preferred silicon-containing precursor is silane.

[0080] When the precursor is a chlorinated compound, such as chlorosilane, it is preferable that the precursor be used in a mixture with hydrogen gas, preferably in an atomic ratio of at least 1:1 hydrogen to chlorine.

[0081] Optionally, the precursor is chlorine-free. Chlorine-free means that the precursor contains less than 1% by weight, preferably less than 0.1% by weight, and preferably less than 0.01% by weight of a chlorine-containing compound.

[0082] In accordance with conventional methods for operations in an inert atmosphere, the presence of oxygen in steps (b) and (d) should be avoided to prevent undesirable oxidation of the deposited silicon. Preferably, the oxygen content is less than 0.01% by volume, more preferably less than 0.001% by volume, relative to the total volume of gas used in step (b) or step (d).

[0083] Step (b) and / or step (d) may be carried out independently at temperatures in the range of 340°C to 500°C, or 350°C to 480°C, or 350°C to 450°C, or 350°C to 420°C, or 355°C to less than 400°C, or 355°C to 395°C, or 360°C to 390°C, or 360°C to 385°C, or 360°C to 380°C. Preferably, steps (b) and / or step (d) are carried out independently at temperatures in the range of 340°C to less than 400°C, or 370°C to 395°C.

[0084] Steps (b) and / or (d) may be carried out independently at pressures ranging from 1 kPa to 10,000 kPa, or 10 kPa to 6,000 kPa, or 20 kPa to 4,000 kPa, or 50 kPa to 2,000 kPa, or 80 kPa to 1,500 kPa, or 90 kPa to 1,000 kPa, or 90 kPa to 600 kPa, or approximately 100 kPa.

[0085] Any reference to pressure in any step of the claimed method refers to the absolute pressure in the reaction zone, which may include any suitable type of reactor vessel.

[0086] Silicon deposition by CVI results in the removal of by-products, particularly by-product gases such as hydrogen. Step (b) preferably further includes the separation of by-products from the particles formed in step (b). Separation of by-products can be achieved by flushing the reactor with an inert gas and / or by exhausting the reactor by reducing the pressure. For example, separation of by-products from the particles formed in step (b) can be achieved by exhausting the reactor to a pressure of less than 100 kPa, or less than 80 kPa, or less than 60 kPa, or less than 40 kPa, or less than 20 kPa, or less than 10 kPa, or less than 5 kPa, or less than 2 kPa, or less than 1 kPa. Evaporating the reactor to a low pressure may be effective not only for removing gaseous by-products but also for desorbing any by-products that may be adsorbed on the deposited silicon surface.

[0087] The ratio of the BET surface area of ​​the particles formed in step (c) to the BET surface area of ​​the particles formed in step (b) may be at least 1.1:1, or at least 1.2:1, or at least 1.3:1, or at least 1.4:1, or at least 1.5:1, or at least 2:1, or at least 3:1, or at least 4:1, or at least 5:1.

[0088] The ratio of the BET surface area of ​​the particles formed in step (c) to the BET surface area of ​​the particles formed in step (b) may be 15:1 or less, or 14:1 or less, or 13:1 or less, or 12:1 or less.

[0089] The ratio of the total pore volume of micropores and mesopores measured by gas adsorption of particles formed in step (c) to the total pore volume of micropores and mesopores measured by gas adsorption of particles formed in step (b) may be at least 2:1, or at least 3:1, or at least 4:1, or at least 5:1, or at least 6:1, or at least 7:1, or at least 8:1.

[0090] The ratio of the total pore volume of micropores and mesopores measured by gas adsorption of particles formed in step (c) to the total pore volume of micropores and mesopores measured by gas adsorption of particles formed in step (b) may be 20:1 or less, or 19:1 or less, or 18:1 or less, or 17:1 or less, or 16:1 or less, or 15:1 or less.

[0091] The ratio of the total hydrogen content of the particles formed in step (c) to the total hydrogen content of the particles formed in step (b) may be 0.8:1 or less, or 0.7:1 or less, or 0.6:1 or less, or 0.5:1 or less.

[0092] The ratio of the total hydrogen content of the particles formed in step (c) to the total hydrogen content of the particles formed in step (b) may be at least 0.1:1, or at least 0.2:1, or at least 0.3:1.

[0093] The temperature in process (c) may be higher than the temperature in process (b). The temperature in process (c) may be at least 20°C, or at least 40°C, or at least 60°C, or at least 80°C, or at least 100°C, or at least 120°C, or at least 140°C, or at least 150°C higher than the temperature in process (b).

[0094] The temperature in step (c) may be at least 450°C, or at least 500°C, or at least 510°C, or at least 520°C, or at least 540°C, or at least 560°C, or at least 580°C, or at least 600°C, or at least 610°C, or at least 620°C, or at least 630°C, or at least 640°C, or at least 650°C. Preferably, the temperature in step (c) is at least 500°C. More preferably, the temperature in step (c) is at least 510°C. More preferably, the temperature in step (c) is at least 520°C. The temperature in step (c) may be 900°C or less, or 850°C or less, or 800°C or less, or 750°C or less, or 700°C or less, or 680°C or less, or 660°C or less, or 650°C or less. Preferably, the temperature in step (c) is 750°C or less. More preferably, the temperature in step (c) is 700°C or lower.

[0095] The temperature in step (c) may be in the range of 400°C to 900°C, 500°C to 900°C, or 600°C to 900°C. The temperature in step (c) may be in the range of 500°C to 800°C, 510°C to 800°C, 520°C to 750°C, 540°C to 700°C, 560°C to 680°C, 580°C to 660°C, or 600°C to 650°C. Preferably, the temperature in step (c) is in the range of 500°C to 750°C. More preferably, the temperature in step (c) is in the range of 510°C to 750°C. More preferably, the temperature in step (c) is in the range of 520°C to 700°C.

[0096] The duration of step (c) is preferably at least 1 minute, or at least 2 minutes, or at least 5 minutes, or at least 10 minutes, or at least 15 minutes, or at least 20 minutes, or at least 30 minutes, or at least 45 minutes, or at least 1 hour, or at least 2 hours. Preferably, step (c) is performed over a period of at least 30 minutes. More preferably, step (c) is performed over a period of at least 1 hour. More preferably, step (c) is performed over a period of at least 90 minutes. Preferably, the duration of step (c) is 72 hours or less, or 48 hours or less, or 24 hours or less, or 12 hours or less, or 6 hours or less, or 5 hours or less, or 4 hours or less, or 3 hours or less. Preferably, step (c) is performed over a period of 24 hours or less. More preferably, step (c) is performed over a period of 12 hours or less. More preferably, step (c) is performed over a period of 6 hours or less.

[0097] The duration of step (c) may be in the range of 1 minute to 72 hours, or 2 minutes to 48 hours, or 5 minutes to 24 hours, or 10 minutes to 12 hours, or 15 minutes to 6 hours, or 20 minutes to 5 hours, or 30 minutes to 4 hours, or 1 hour to 4 hours, or 1 hour to 3 hours. Preferably, the duration of step (c) is in the range of 30 minutes to 24 hours. More preferably, the duration of step (c) is in the range of 1 hour to 12 hours. More preferably, the duration of step (c) is in the range of 90 minutes to 6 hours.

[0098] Step (c) preferably includes maintaining the particles derived from step (b) above a lower threshold temperature TL of at least 400°C over time t. More preferably, step (c) includes maintaining the particles derived from step (b) between a lower threshold temperature TL and an upper threshold temperature TU over time t.

[0099] The lower threshold temperature TL in step (c) may be 450°C, 500°C, 510°C, 520°C, 540°C, 560°C, 580°C, 600°C, 610°C, 620°C, 630°C, 640°C, or 650°C. Preferably, the lower threshold temperature TL in step (c) is 500°C. More preferably, the lower threshold temperature TL in step (c) is 510°C. More preferably, the lower threshold temperature TL in step (c) is 520°C. Preferably, the upper threshold temperature TU in step (c) is 900°C, 850°C, 800°C, 750°C, 700°C, 695°C, 680°C, 660°C, or 650°C. More preferably, the upper threshold temperature TU in step (c) is 750°C. More preferably, the upper threshold temperature TU in step (c) is 700°C.

[0100] The lower threshold temperature TL and the upper threshold temperature TU may be 400°C and 900°C, or 500°C and 900°C, or 600°C and 900°C, respectively. The lower threshold temperature TL and the upper threshold temperature TU may be 500°C and 800°C, or 510°C and 800°C, or 520°C and 750°C, or 540°C and 700°C, or 560°C and 680°C, or 580°C and 660°C, or 600°C and 650°C, respectively. Preferably, the lower threshold temperature TL and the upper threshold temperature TU are 500°C and 750°C, respectively. More preferably, the lower threshold temperature TL and the upper threshold temperature TU are 510°C and 750°C, respectively. More preferably, the lower threshold temperature TL and the upper threshold temperature TU are 520°C and 700°C, respectively.

[0101] The time t is preferably at least 1 minute, or at least 2 minutes, or at least 5 minutes, or at least 10 minutes, or at least 15 minutes, or at least 20 minutes, or at least 30 minutes, or at least 45 minutes, or at least 1 hour, or at least 2 hours. Preferably, the time t is at least 30 minutes. Preferably, the time t is at least 1 hour. Preferably, the time t is at least 90 minutes. Preferably, the time t is 72 hours or less, or 48 hours or less, or 24 hours or less, or 12 hours or less, or 6 hours or less, or 5 hours or less, or 4 hours or less, or 3 hours or less. Preferably, the time t is 24 hours or less. Preferably, the time t is 12 hours or less. Preferably, the time t is 6 hours or less.

[0102] The time t may be in the range of 1 minute to 72 hours, or 2 minutes to 48 hours, or 5 minutes to 24 hours, or 10 minutes to 12 hours, or 15 minutes to 6 hours, or 20 minutes to 5 hours, or 30 minutes to 4 hours, or 1 hour to 4 hours, or 1 hour to 3 hours. Preferably, the time t is in the range of 30 minutes to 24 hours. More preferably, the time t is in the range of 1 hour to 12 hours. More preferably, the time t is in the range of 90 minutes to 6 hours.

[0103] Step (c) is carried out in the presence of an inert gas. In this specification, an inert gas refers to any gas that does not react under the conditions of step (c). Therefore, no gas that reacts under the conditions of step (c) is present in step (c). The inert gas is preferably selected from nitrogen and noble gases, particularly argon. Optionally, the inert gas may include hydrogen. The inert gas can be selected from the group consisting of nitrogen, argon, helium, and combinations thereof. Step (c) may be carried out in the presence of hydrogen and a gas selected from the group consisting of nitrogen, argon, helium, and combinations thereof.

[0104] Step (c) is, (i) At temperatures in the range of 400℃ to 900℃, (ii) Over a period of 1 minute to 72 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0105] Step (c) is, (i) At temperatures in the range of 500℃ to 900℃, (ii) Over a period of 30 minutes to 4 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0106] Step (c) is, (i) At temperatures in the range of 600°C to 900°C, (ii) Over a period of 1 to 4 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0107] Step (c) is, (i) At temperatures in the range of 500°C to 750°C, (ii) over a period of 30 minutes to 24 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0108] Step (c) is, (i) At temperatures in the range of 500°C to 750°C, (ii) Over a period of 1 to 12 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0109] Step (c) is, (i) At temperatures in the range of 500°C to 700°C, (ii) Over a period of 90 minutes to 6 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0110] Step (c) is, (i) At temperatures in the range of 510°C to 750°C, (ii) over a period of 30 minutes to 24 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0111] Step (c) is, (i) At temperatures in the range of 510°C to 750°C, (ii) Over a period of 1 to 12 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0112] Step (c) is, (i) At temperatures in the range of 510°C to 700°C, (ii) Over a period of 90 minutes to 6 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0113] Step (c) is, (i) At temperatures in the range of 520°C to 750°C, (ii) over a period of 30 minutes to 24 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0114] Step (c) is, (i) At temperatures in the range of 520°C to 750°C, (ii) Over a period of 1 to 12 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0115] Step (c) is, (i) At temperatures in the range of 520°C to 700°C, (ii) Over a period of 90 minutes to 6 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0116] Step (c) is, (i) With a lower threshold temperature TL of 500°C and an upper threshold temperature TU of 750°C, (ii) Over a period of time t from 30 minutes to 24 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0117] Step (c) is, (i) With a lower threshold temperature TL of 500°C and an upper threshold temperature TU of 750°C, (ii) Over a period of time t from 1 hour to 12 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0118] Step (c) is, (i) With a lower threshold temperature TL of 500°C and an upper threshold temperature TU of 700°C, (ii) Over a period of time t between 90 minutes and 6 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0119] Step (c) is, (i) With a lower threshold temperature TL of 510°C and an upper threshold temperature TU of 750°C, (ii) Over a period of time t from 30 minutes to 24 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0120] Step (c) is, (i) With a lower threshold temperature TL of 510°C and an upper threshold temperature TU of 750°C, (ii) Over a period of time t from 1 hour to 12 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0121] Step (c) is, (i) With a lower threshold temperature TL of 510°C and an upper threshold temperature TU of 700°C, (ii) Over a period of time t between 90 minutes and 6 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0122] Step (c) is, (i) With a lower threshold temperature TL of 520°C and an upper threshold temperature TU of 750°C, (ii) Over a period of time t from 30 minutes to 24 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0123] Step (c) is, (i) With a lower threshold temperature TL of 520°C and an upper threshold temperature TU of 750°C, (ii) Over a period of time t from 1 hour to 12 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0124] Step (c) is, (i) With a lower threshold temperature TL of 520°C and an upper threshold temperature TU of 700°C, (ii) Over a period of time t between 90 minutes and 6 hours, (iii) Optionally in the presence of an inert gas containing hydrogen, It is preferable to do so.

[0125] Step (c) preferably includes subjecting the particles derived from step (b) to heat treatment at a temperature of at least 400°C in the presence of an inert gas in order to promote the formation of Si-Si bonds in the silicon domains, promote the formation of covalent bonds between silicon and the inner surface of the porous particle skeleton while avoiding the formation of silicon carbide, reduce the surface area of ​​the silicon domains, and / or increase the chemical stability of the silicon domains.

[0126] Steps (b), (c), and (d) may be carried out in the same reactor vessel. Alternatively, step (b) may be carried out in the first reactor vessel, and then the particles formed in step (b) may be transferred to the second reactor vessel and step (c) may be carried out. The particles may be kept at a temperature lower than the temperature in step (b) while being transferred to the second reactor vessel. Preferably, the particles are kept at a temperature of at least 50°C while being transferred to the second reactor vessel. After that, the particles formed in step (c) may be transferred to the first reactor vessel and step (d) may be carried out. Alternatively, the particles formed in step (c) may be transferred to the third reactor vessel and step (d) may be carried out.

[0127] In one aspect, the present invention relates to a method for preparing composite particles, (a) A step of preparing a plurality of porous particles including micropores and / or mesopores, (b) A step of bringing porous particles and a silicon-containing precursor into contact at a temperature effective in causing the deposition of multiple nanoscale silicon domains into the pores of the porous particles, (c) A step of maintaining the particles derived from step (b) above a lower threshold temperature TL of at least 400°C over time t, (d) A step of bringing particles derived from step (c) and a silicon-containing precursor into contact at a temperature effective in causing further deposition of silicon domains into the pores of the porous particles, This provides a method that includes [something].

[0128] Step (c) preferably includes maintaining the particles derived from step (b) between a lower threshold temperature TL and an upper threshold temperature TU over time t.

[0129] Preferably, the lower threshold temperature TL is 500°C, the upper threshold temperature TU is 700°C, and the time t is 90 minutes to 6 hours.

[0130] The above aspects of the present invention can optionally be combined with any other features disclosed herein in connection with the first aspect of the present invention.

[0131] Step (c) and / or step (d) may be repeated one or more times.

[0132] The composite particles obtained by the method of the present invention can be characterized by their performance under thermogravimetric analysis (TGA) in air. This analytical method is based on the principle that an increase in weight is observed when electroactive materials are oxidized in air and at higher temperatures.

[0133] As defined herein, “surface silicon” is calculated from the initial mass increase of the TGA trace from a minimum value between 150°C and 500°C to a maximum mass measured in the temperature range between 550°C and 650°C, with TGA performed at a heating rate of 10°C / min in air. This mass increase is assumed to result from the oxidation of surface silicon and is therefore given by the following equation: Y = 1.875 × [(M max -M min ) / M f ] × 100% (In the formula, Y is the percentage of surface silicon as the ratio of total silicon in the sample, and M max This is the maximum mass of a sample measured in the temperature range between 550°C and 650°C, and M min This is the minimum mass of the sample at temperatures above 150°C and below 500°C, M f The percentage of surface silicon as a ratio to the total amount of silicon can be determined according to the mass of the sample at 1400°C (where is the mass of the sample when oxidation is complete). For completeness, it will be understood that 1.875 is the molar mass ratio of SiO2 to O2 (i.e., the mass ratio of formed SiO2 to the mass increase due to the addition of oxygen). Typically, TGA analysis is performed using a sample size of 10 mg ± 2 mg.

[0134] It has been found that when the surface silicon determined by the above TGA method is at least 20% by weight of the total amount of silicon in the composite particles, the reversible capacity retention over many charge-discharge cycles is significantly improved. Preferably, the surface silicon determined by thermogravimetric analysis (TGA) is at least 22% by weight, or at least 25% by weight, at least 30% by weight, or at least 35% by weight, or at least 40% by weight, or at least 45% by weight of silicon.

[0135] As used herein, "crude bulk silicon" is defined as silicon that undergoes oxidation above 800°C, as determined by TGA, where TGA is performed at a heating rate of 10°C / min in air. Therefore, the crude bulk silicon content is given by the following formula: Z = 1.875 × [(M f -M 800 ) / M f ] × 100% (In the formula, Z is the percentage of unoxidized silicon at 800°C, and M 800 This is the mass of the sample at 800°C, M f The mass is determined according to the mass of ash at 1400°C (where is the mass of ash when oxidation is complete). For the purposes of this analysis, any mass increase above 800°C is assumed to correspond to oxidation from silicon to SiO2, and the total mass at the completion of oxidation is assumed to be SiO2.

[0136] Preferably, 10% by weight or less, 8% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or 1.5% by weight or less of the silicon in the particles formed in the final step (d) is crude bulk silicon determined by TGA.

[0137] Preferably, at least 30% by weight of silicon is surface silicon and 10% by weight or less of silicon is crude bulk silicon, both determined by TGA. More preferably, at least 35% by weight of silicon is surface silicon and 8% by weight or less of silicon is crude bulk silicon, both determined by TGA. More preferably, at least 40% by weight of silicon is surface silicon and 5% by weight or less of silicon is crude bulk silicon, both determined by TGA. More preferably, at least 45% by weight of silicon is surface silicon and 2% by weight or less of silicon is crude bulk silicon, both determined by TGA. The method of the present invention is considered capable of producing composite particles with a low crude silicon content. Preferably, 10% by weight or less of silicon, or 8% by weight or less of silicon, or 6% by weight or less of silicon, or 5% by weight or less of silicon, or 4% by weight or less, or 3% by weight or less, or 2% by weight or less, or 1.5% by weight or less of silicon in the composite particles formed in the final step (d) is crude bulk silicon as determined by thermogravimetric analysis (TGA).

[0138] The amount of silicon in the composite particles can be determined by elemental analysis. Preferably, elemental analysis is used to determine the elemental composition of the porous particles alone and the composition of the composite particles.

[0139] The silicon content is preferably determined by ICP-OES (inductively coupled plasma emission spectroscopy). Many ICP-OES analyzers are commercially available, such as the iCAP® 7000 series from ThermoFisher Scientific. The carbon, hydrogen, nitrogen, and / or oxygen content in composite particles and / or porous carbon particles is preferably determined by IR absorption. A suitable instrument for determining the carbon, hydrogen, nitrogen, and / or oxygen content is the TruSpec® Micro elemental analyzer available from Leco Corporation.

[0140] Filling of composite particles with a range of different silicon can be obtained using the method of the present invention. The particles formed in the final step (d) may contain 5% to 85% by weight, or 10% to 85% by weight, or 15% to 85% by weight, or 20% to 80% by weight, or 25% to 80% by weight, or 30% to 75% by weight, or 35% to 75% by weight, or 40% to 70% by weight, or 45% to 65% by weight, based on the total mass of the particles.

[0141] The amount of silicon in the composite particles formed in the final step (d) is such that the mass ratio of silicon to porous particles is [0.50 × P 1 ~1.9×P 1 The requirement that ]:1 can be related to the available pore volume in porous particles, where P 1 is, cm 3 This is a dimensionless number that has the same value as the total pore volume of micropores and mesopores in porous particles, as measured by gas adsorption, as expressed in / g (for example, if the porous particles are 1.2 cm²). 3 If the total volume of micropores and mesopores is 1 / g, then P 1 (=1.2). This relationship takes into account the density of silicon and the pore volume of porous particles, and defines the weight ratio of silicon that occupies approximately 20% to 82% of the pore volume. The weight ratio of silicon in the composite particles formed in the final step (d) is [0.6 × P 1 ~1.8×P 1 ]:1, or [0.7 × P 1 ~1.7×P 1 ]:1, or [0.8 × P 1 ~1.6×P 1 ]:1 is preferable.

[0142] The amount of silicon in the composite particles is preferably selected such that at least 25% and a maximum of 90% of the internal pore volume of the porous particles is occupied by silicon after the final step (d). For example, silicon may occupy 25% to 80%, or 25% to 75%, or 30% to 70%, or 35% to 65%, or 40% to 60%, or 45% to 55% of the internal pore volume of the porous particles. Within these preferred ranges, the remaining pore volume of the porous particles is effective in accommodating the expansion of the electroactive material during charging and discharging, without having excess pore volume that does not contribute to the volumetric capacity of the particulate particles. However, the amount of electroactive material is also not high enough to hinder effective lithiation due to an inadequate metal ion diffusion rate or an inadequate expansion volume that results in mechanical resistance to lithiation.

[0143] At least 85% by weight of silicon in the particles formed in the final step (d) may be located within the internal pore volume of the porous particles. Optionally, at least 90% by weight, or at least 95% by weight, or at least 98% by weight of silicon in the particles formed in the final step (d) may be located within the internal pore volume of the porous particles. As discussed above, silicon deposition during the CVI process occurs on the surface of the porous particles. Given the very high internal surface area of ​​the porous particles, the reaction kinetics of the CVI process ensure that silicon deposition occurs almost entirely within the pores of the porous particles. Internal silicon deposition is further improved by the requirement that the particles formed in step (b) be subjected to a heat treatment step (c) followed by further silicon deposition in step (d).

[0144] The method of the present invention is (e) The final step of bringing the surface of particles derived from (d) into contact with a passivating agent. It can further include:

[0145] As defined herein, a passivator is a compound or mixture of compounds capable of reacting with the silicon surface deposited in the final step (d) to form a modified surface. In particular, the passivators defined herein are materials that react with the silicon surface to further reduce its surface energy.

[0146] The passivating agent can be selected from (i) oxygen-containing gas, (ii) ammonia, (iii) a gas containing ammonia and oxygen, and (iv) phosphine.

[0147] Passivation agents are (i)R 1 -CH=CH-R 1 , (ii)R 1 -C≡CR 1 , (iii) O=CR 1 R 1 , (iv) HX-R 2 , and, (v)HX-C(O)-R 1 , (In the formula, X is O, S, NR) 1 or PR 1 This represents, Each R 1 can independently represent H, or an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, or two R 1 The group forms an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring. R 2 represents an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, or R 1 and R 2 These can be selected from unsubstituted or substituted ring structures (which together form an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring).

[0148] One type of passivation layer is the native oxide layer. For example, the native oxide layer may be formed by exposing the silicon surface to a passivating agent selected from air or another oxygen-containing gas. The passivation layer may comprise silicon oxide of the formula SiO x (where 0 < x ≦ 2). The silicon oxide is preferably amorphous silicon oxide. The formation of the native oxide layer is exothermic and thus requires careful process control to prevent overheating or even combustion of the particulate material. When the passivating agent is an oxygen-containing gas, step (c) may include cooling the material formed in step (b) to a temperature below 300°C, preferably below 200°C, optionally below 100°C, before contacting the silicon surface with the oxygen-containing gas.

[0149] Another type of passivation layer is, for example, a nitride layer formed by exposing the silicon surface to a passivating agent selected from ammonia or another nitrogen-containing molecule. The passivation layer may comprise silicon nitride of the formula SiN x (where 0 < x ≦ 4 / 3). The silicon nitride is preferably amorphous silicon nitride. The nitride layer can be formed by contacting the silicon surface with ammonia at a temperature in the range of 200°C to 700°C, preferably 400°C to 700°C, more preferably 400°C to 600°C. Then, if necessary, the temperature can be raised to the range of 500°C to 1000°C to form a nitride surface (e.g., a silicon nitride surface of the formula SiN x (where x ≦ 4 / 3)). Nitride passivation may be preferred over oxide passivation in some cases. Stoichiometric nitrides (e.g., SiN x (where 0 < x ≦ 4 / 3)) are conductive, so the nitride passivation layer functions as a conductive network that enables more rapid charging and discharging of electroactive materials. Phosphine may also be used as a passivating agent as a phosphorus analog of ammonia.

[0150] Another type of passivation layer is, for example, an oxynitride layer formed by exposing the silicon surface to a passivating agent containing ammonia (or another nitrogen-containing molecule) and oxygen gas. The passivation layer may contain silicon oxynitride of the formula SiO x N y (where 0 < x < 2, 0 < y < 4 / 3, and 0 < (2x + 3y) ≦ 4). The silicon nitride is preferably amorphous silicon oxynitride.

[0151] Another type of passivation layer is a carbide layer. The passivation layer may contain silicon carbide of the formula SiC x (where 0 < x ≦ 1). The silicon carbide is preferably amorphous silicon carbide. The carbide layer may be formed by contacting the silicon surface with a passivating agent selected from carbon-containing precursors such as methane or ethylene at an elevated temperature, for example, in the range of 250°C to 700°C. At lower temperatures, covalent bonds are formed between the silicon surface and the carbon-containing precursor, which is converted to a single layer of crystalline silicon carbide as the temperature rises. The modifier material domain may contain silicon carbide of the formula SiC x (where 0 < x ≦ 1).

[0152] [[ID=!16]]Other suitable passivating agents include compounds containing alkene, alkyne or carbonyl functional groups, more preferably compounds containing terminal alkene, terminal alkyne, aldehyde or ketone groups.

[0153] [[ID=1!9]] Particularly preferred passivating agents include the following formulas: (i) CH2=CH-R 1 and (ii) HC≡C-R 1 (where R 1 is as defined above) includes one or more compounds. Preferably, R 1 is unsubstituted.

[0154] Note: There seems to be a minor error in the original text where "!16" and "1!9" are used instead of "16" and "19". The translation is done as per the provided text.Suitable passivators include ethylene, propylene, 1-butene, butadiene, 1-pentene, 1,4-pentadiene, 1-hexene, 1-octene, styrene, divinylbenzene, acetylene, phenylacetylene, norbornene, norbornadiene, and bicyclo[2.2.2]octa-2-ene. Optionally, mixtures of different passivators may also be used.

[0155] Passivating agents containing alkenes, alkynes, or carbonyl groups are thought to form a covalently passivated surface resistant to oxidation by air through insertion reactions with Si-H groups on the silicon surface. Therefore, the passivation reaction between the silicon surface and the passivating agent can be understood as a form of hydrosilylation, as schematically shown below. [ka]

[0156] 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 XH group and the hydride group on the silicon surface is understood to result in the removal of H2 and the formation of a direct bond between X and the electroactive material surface.

[0157] A suitable passivator in this category is given by the following formula: (iv) HX-R 2 , and, (v)HX-C(O)-R 1 (In the formula, X and each R) 1 and R 2 This includes compounds (which are independently defined above).

[0158] Preferably, X represents O or NH.

[0159] Preferably, R 2represents an optionally substituted aliphatic or aromatic group having 2 to 10 carbon atoms. The amine group may be incorporated into a 4- to 10-membered aliphatic or aromatic ring structure, as in pyrrolidine, pyrrole, imidazole, piperazine, indole, or purine.

[0160] Another suitable passivating agent is water. For example, the silicon surface may be exposed to water vapor. Alternatively, the particles from step (d) may be immersed in water. Optionally, passivation with water may be performed following passivation with one or more of the passivating agents disclosed above.

[0161] It is preferable to carry out step (e) using a passivation agent other than air.

[0162] Step (e) may be carried out at a temperature in the range of 25°C to 500°C, preferably in the range of 50°C to 450°C, and more preferably in the range of 100°C to 400°C.

[0163] The method of the present invention is (f) A step of combining particles derived from the final step (d) or step (e) with a pyrolytic carbon precursor, and heating the pyrolytic carbon precursor to a temperature effective in causing the deposition of conductive pyrolytic carbon material in the pores and / or on the outer surface of the composite particles. It can further include:

[0164] If step (e) is included in the method, step (f) may optionally be performed before or after step (e). In either case, step (f) is performed after the final step (d).

[0165] The pyrolytic carbon precursor is preferably a hydrocarbon. Suitable hydrocarbons include polycyclic hydrocarbons containing 10 to 25 carbon atoms and optionally 1 to 3 heteroatoms, and optionally, polycyclic aromatic hydrocarbons are selected from naphthalene, substituted naphthalenes, e.g., dihydroxynaphthalene, anthracene, tetracene, pentacene, fluorene, acenaphthene, phenanthrene, fluorantene, pyrene, chrysene, perylene, coronene, fluorenone, anthraquinone, anthrone and their alkyl-substituted derivatives. Suitable pyrolytic carbon precursors also include bicyclic monoterpenoids, and optionally, bicyclic monoterpenoids are selected from camphor, borneol, eucalyptol, camphene, careen, sabinene, thujene and pinene. Further suitable pyrolytic carbon precursors include C2-C 10 Hydrocarbons are included, optionally selected from alkanes, alkenes, alkynes, cycloalkanes, cycloalkenes, and arenes, such as methane, ethylene, propylene, limonene, styrene, cyclohexane, cyclohexene, α-terpinene, and acetylene. Other suitable pyrolytic carbon precursors include phthalocyanines, sucrose, starch, graphene oxide, reduced graphene oxide, pyrene, perhydropyrene, triphenylene, tetracene, benzopyrene, perylene, coronene, and chrysene. The preferred carbon precursor is acetylene.

[0166] The suitable temperature for depositing the pyrolytic carbon material in step (f) is in the range of 300°C to 800°C, or 400°C to 700°C. For example, the temperature 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 varies depending on the type of carbon precursor used. Preferably, the temperature 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.

[0167] The pyrolytic carbon precursor used in step (f) may be used in pure form or in a mixture diluted with an inert carrier gas such as nitrogen or argon. For example, the pyrolytic carbon precursor may be used in an amount in the range of 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.

[0168] When the pyrolytic carbon material is deposited in step (f), the same compound can function as both the passivating agent in step (e) and the pyrolytic carbon precursor in step (f). For example, if styrene is selected as the pyrolytic carbon precursor, it will also function as a passivating agent if the particles from step (d) are not exposed to another passivating agent prior to contact with styrene. In this case, the passivation and deposition of the conductive carbon material during the process can be carried out simultaneously, for example, at a temperature in the range of 300°C to 700°C. Alternatively, the passivation and deposition of the conductive pyrolytic carbon material can be carried out continuously if the passivating agent and the pyrolytic carbon precursor are the same material, but step (f) is carried out after step (e) at a higher temperature than the passivation in step (e). For example, the passivation in step (e) can be carried out at a temperature in the range of 25°C to less than 300°C, and the deposition of pyrolytic carbon can be carried out at a temperature in the range of 300°C to 700°C. These two steps can be appropriately carried out continuously by raising the temperature while maintaining contact with the compound that functions as both the passivating agent and the pyrolytic carbon precursor. At a lower temperature (for example, in the range of 25°C to less than 300°C), passivation will be the main process. As the temperature rises (for example, to 300°C to 700°C), the deposition of pyrolytic carbon is considered to subsequently occur.

[0169] The process of the reaction may be carried out using any reactor capable of bringing solids and gases into contact at an elevated temperature. The porous particles and the composite particles to be formed may be present in the reactor in the form of a fixed bed of particles, or in the form of a moving bed or a stirred bed of particles.

[0170] In a second embodiment, the present invention provides a particulate material consisting only of a plurality of composite particles that can be obtained by the method of the first embodiment.

[0171] In a third aspect of the present invention, a composition is provided comprising a particulate material according to a second aspect of the present invention and at least one other component, the at least one other component being one or more of (i) a binder, (ii) a conductive additive, and (iii) further particulate electroactive materials. The composition according to the third aspect of the present invention is useful as an electrode composition and can therefore be used to form an active layer of an electrode.

[0172] The composition may be a hybrid electrode composition comprising 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.

[0173] In the case of a hybrid electrode composition, the composition preferably contains particulate material according to a second embodiment of the present invention in an amount of 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.

[0174] At least one additional particulate electroactive material is preferably present in an amount of 20% to 95% by weight, or 25% to 90% by weight, or 30% to 75% by weight.

[0175] At least one additional particulate electroactive material is preferably 10 μm to 50 μm, preferably 10 μm to 40 μm, more preferably 10 μm to 30 μm, most preferably 10 μm to 25 μm, for example, in the range of 15 μm to 25 μm. 50 It has a particle size.

[0176] D of at least one additional particulate electroactive material 10 The 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 even more preferably at least 10 μm.

[0177] D of at least one additional particulate electroactive material 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.

[0178] At least one additional particulate electroactive material is preferably selected from carbon-containing particles, graphite particles, and / or hard carbon particles, where graphite particles and hard carbon particles are in the range of 10 μm to 50 μm. 50 The particle size is determined. More preferably, at least one additional particulate electroactive material is selected from graphite particles, where the graphite particles are in the range of 10 μm to 50 μm. 50 It has a particle size.

[0179] The composition may be a non-hybrid (i.e., “highly packed”) electrode composition substantially free of additional particulate electroactive material. In this context, the term “substantially free of additional particulate electroactive material” should be interpreted as meaning that the composition contains any additional electroactive material (i.e., additional material capable of inserting and releasing metal ions during charging and discharging of the battery) in an amount of 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, relative to the total dry weight of the composition.

[0180] This type of "highly packed" electrode composition preferably contains, with respect to the total dry weight of the composition, particulate material according to the second embodiment of the present invention in an amount of 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.

[0181] 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 can 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 contain a mixture of binders. Preferably, the binder comprises a polymer selected from polyacrylic acid (PAA) and its alkali metal salts, as well as modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0182] The binder can 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, relative to the total dry weight of the composition.

[0183] 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.

[0184] The composition may optionally contain one or more conductive additives. Preferred conductive additives are non-electroactive materials included to improve conductivity between the electroactive components of the composition and between the electroactive components of the composition and the current collector. Conductive additives can 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.

[0185] 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.

[0186] In a fourth embodiment, the present invention provides an electrode comprising a particulate material according to a second embodiment of the present invention or a composition according to a third embodiment of the present invention. The particulate material can be electrically contacted with a current collector.

[0187] As used herein, the term current collector refers to any conductive substrate capable of conducting electric current to and from electroactive particles in a 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 typically take the form of foil or mesh having a thickness of 3 μm to 500 μm. The particulate material of the present invention can be applied to one or both sides of a current collector, preferably with a thickness ranging from 10 μm to 1 mm, for example, 20 μm to 500 μm, or 50 μm to 200 μm.

[0188] An electrode according to a fourth aspect of the present invention can be prepared by forming a slurry by combining the particulate material according to the second aspect 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, and the solvent is removed to form an electrode layer on the surface of the current collector. Further steps such as heat treatment to cure any binder and / or calendering of the electrode layer can be performed 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.

[0189] Alternatively, the slurry can be formed into a self-supporting film or mat containing the particulate material of the present invention by, for example, casting the slurry onto a suitable cast template, removing the solvent, and then removing the cast template. The resulting film or mat has the form of self-supporting aggregates and can then be adhered to a current collector by known methods.

[0190] The electrode according to the fourth aspect of the present invention can be used as an anode in a metal-ion battery. Therefore, in the fifth aspect, the present invention provides a rechargeable metal-ion battery comprising the electrode according to the fourth aspect as an anode.

[0191] The metal ion is preferably a lithium ion. More preferably, the rechargeable metal ion battery of the present invention is a lithium ion battery, and the cathode active material is capable of releasing and receiving lithium ions.

[0192] The cathode of a rechargeable metal-ion battery typically comprises a current collector and a cathode active material capable of releasing and reabsorbing metal ions. The cathode active material is preferably a metal oxide composite. Examples of suitable cathode active materials include LiCoO2, LiCo 0.99 Al 0.01 O2, LiNiO2, LiMnO2, LiCo 0.5 Ni 0.5O2, 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 O2 is one example. The cathode current collector typically has a thickness of 3 μm to 500 μm. Examples of materials that can be used as cathode current collectors include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0193] Suitable electrolytes are non-aqueous electrolytes containing metal salts, such as lithium salts, and include, but are not limited to, non-aqueous electrolytes, solid electrolytes, and inorganic solid electrolytes. Examples of non-aqueous electrolytes that can be used include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, sulfolane, methylsulfolane, and aprotic organic solvents such as 1,3-dimethyl-2-imidazolidinone.

[0194] Examples of organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociation groups.

[0195] Examples of inorganic solid electrolytes include nitrides, halides, and sulfides of lithium salts such as Li5NI2, Li3N, LiI, LiSiO4, Li2SiS3, Li4SiO4, LiOH, and Li3PO4.

[0196] Lithium salts are preferably soluble in a selected solvent or a mixture of solvents. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO4, LiBF4, LiBC4O8, LiPF6, LiCF3SO3, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, and CF3SO3Li.

[0197] When the electrolyte is a non-aqueous organic solution, the metal-ion battery preferably includes a separator inserted between the anode and the cathode. 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 μm to 100 μm and a thickness of 5 μm to 300 μm. A suitable example of an electrode separator is a microporous polyethylene film.

[0198] The separator can be replaced with a polymer electrolyte material, in which case the polymer electrolyte material is present in both the composite anode layer and the composite cathode layer. The polymer electrolyte material can be a solid polymer electrolyte or a gel-type polymer electrolyte. [Examples]

[0199] Example 1 A silicon-carbon composite sample A (30g) was packed into the furnace tube. After sealing the furnace tube, it was purged with nitrogen (0.3 L / min) for 30 minutes. The furnace tube was heated to the target temperature (650°C) under nitrogen (0.3 L / min) for 97 minutes.

[0200] Next, the silicon-carbon composite was annealed at 650°C for 90 minutes under nitrogen (0.5 L / min). Then, the furnace temperature was cooled to room temperature under nitrogen (0.5 L / min).

[0201] Next, the annealed material was passed through a nitrogen stream (0.2 L / min) and an air stream (0.3 L / min) at room temperature for 35 minutes, followed by a 90-minute passivation period under an air stream (0.5 L / min).

[0202] The obtained powder was used as sample B for characterization.

[0203] The characterization of Sample A and Sample B is shown in Table 1 below. Sample A is the silicon-carbon composite used to prepare Sample B.

[0204] Cumulative pore volume (cm³) of sample A and sample B 3 Figure 1 shows the values ​​for / g).

[0205] [Table 1]

[0206] Example 2 A silicon-carbon composite sample C (40g) was packed into a rotary kiln tube. After sealing the rotary kiln tube, it was purged with nitrogen (0.3 L / min) for 30 minutes. The furnace tube was heated to the target temperature (520°C) under nitrogen (0.3 L / min) for 80 minutes and stabilized for 10 minutes.

[0207] The nitrogen flow was increased to 0.66 L / min, the rotation speed was increased to 50 rpm, and the silicon-carbon composite was annealed for 180 minutes. The furnace was then cooled to room temperature.

[0208] Next, the annealed material was passed through a nitrogen stream (0.2 L / min) and an air stream (0.3 L / min) at room temperature for 30 minutes, followed by a 30-minute passivation period under an air stream (0.5 L / min).

[0209] The obtained powder was used as sample D for characterization.

[0210] Samples E and F were prepared using the method described for sample D and the conditions outlined in Table 2 below. The characterization of samples C to F is shown in Table 3 below. Sample C is the silicon-carbon composite used in the preparation of samples D to F.

[0211] [Table 2]

[0212] [Table 3]

[0213] As shown in Tables 1 and 3, the hydrogen content decreases as a result of annealing.

[0214] The addition of hydrogen to the annealing atmosphere (as in sample F) results in increased hydrogen retention within the structure, thereby bringing the surface silicon content closer to that of the basic silicon-carbon composite sample C.

Claims

1. A method for preparing composite particles, (a) A step of preparing a plurality of porous particles including micropores and / or mesopores, (b) A step of bringing the porous particles and the silicon-containing precursor into contact at a temperature effective in causing the deposition of multiple silicon domains into the pores of the porous particles, (c) A step of subjecting the particles derived from step (b) to heat treatment at a temperature of at least 400°C in the presence of an inert gas, (d) A step of bringing particles derived from step (c) and a silicon-containing precursor into contact at a temperature effective in causing further deposition of silicon domains into the pores of the porous particles, Methods that include...

2. The total pore volume of micropores and mesopores in the porous particles, as measured by gas adsorption, is at least 0.4 cm³. ３ / g, or at least 0.5cm ３ / g, or at least 0.6cm ３ / g, or at least 0.65 cm ３ / g, or at least 0.7cm ３ / g, or at least 0.75 cm ３ / g, or at least 0.8cm ３ The method according to claim 1, wherein the value is / g.

3. The total pore volume of micropores and mesopores in the porous particles, measured by gas adsorption, is 2 cm ３ / g or less, or 1.8 cm ３ / g or less, or 1.7 cm ３ / g or less, or 1.6 cm ３ / g or less, or 1.55 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 less, or 1.35 cm ３ / g or less, or 1.3 cm ３ / g or less, or 1.25 cm ３ / g or less, or 1.2 cm ３ / g or less, according to the method of claim 1 or 2.

4. The PD of the porous particles ９０ The method according to any one of claims 1 to 3, wherein the pore diameter is 30 nm or less, or 25 nm or less, or 20 nm or less, or 15 nm or less, or 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less.

5. The PD of the porous particles ９０ The method according to any one of claims 1 to 4, wherein the pore size is at least 3.2 nm, or at least 3.5 nm, or at least 3.8 nm, or at least 4 nm.

6. The PD of the porous particles ５０ The method according to any one of claims 1 to 5, wherein the pore size is 20 nm or less, or 15 nm or less, or 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less, or 1.5 nm or less.

7. The method according to any one of claims 1 to 6, wherein the volume fraction of micropores to the total volume of micropores and mesopores in the porous particle is at least 0.4, or at least 0.45, or at least 0.5, or at least 0.55, or at least 0.6, or at least 0.65, or at least 0.

7.

8. The porous particles are 100 m ２ / g to 4000m ２ / g, or 500m ２ / g to 4000m ２ / g, or 750m ２ / g to 3500m ２ / g, or 1000m ２ / g ~ 3250m ２ / g, or 1000m ２ / g to 3000m ２ / g, or 1000m ２ / g to 2500m ２ / g, or 1000m ２ / g to 2000m ２ The method according to any one of claims 1 to 7, having a BET surface area in the range of / g.

9. The method according to any one of claims 1 to 8, wherein the porous particles are conductive porous particles, preferably conductive porous carbon particles, more preferably conductive porous carbon particles containing at least 80% by weight of carbon, or at least 85% by weight of carbon, or at least 90% by weight of carbon, or at least 95% by weight of carbon.

10. The method according to any one of claims 1 to 9, wherein the silicon-containing precursor is a gaseous precursor.

11. The method according to claim 10, wherein step (b) and / or step (d) is to bring the porous particles into contact with a gas containing a silicon-containing precursor in an amount of at least 30 volume% or at least 40 volume% or at least 50 volume% or at least 60 volume% or at least 70 volume% or at least 80 volume% or at least 90 volume% or at least 95 volume% or at least 97 volume% or at least 99 volume% of the total volume of the gas.

12. The silicon-containing precursor in step (b) and / or step (d) is independently a silane (SiH ４ ), disilane (Si ２ H ６ ), trisilane (Si ３ H ８ ), tetrasilane (Si ４ H １０ A silane (SiH) is selected from the group consisting of methylsilane, dimethylsilane, and chlorosilane, and is preferably selected from the group consisting of methylsilane, methylsilane, and chlorosilane. ４ ), disilane (Si ２ H ６ ), trisilane (Si ３ H ８ ) and tetrasilane (Si ４ H １０ The method according to any one of claims 1 to 11, selected from the group consisting of ).

13. The method according to any one of claims 1 to 12, wherein 10% by weight or less of silicon in the particles formed in the final step (d) is crude bulk silicon as determined by thermogravimetric analysis (TGA).

14. The method according to any one of claims 1 to 13, wherein step (b) and / or step (d) are carried out independently at a temperature in the range of 340°C to 500°C, or 350°C to 480°C, or 350°C to 450°C, or 350°C to 420°C, or 355°C to less than 400°C, or 355°C to 395°C, or 360°C to 390°C, or 360°C to 385°C, preferably, step (b) and / or step (d) are carried out independently at a temperature in the range of 340°C to less than 400°C, or 370°C to 395°C.

15. The method according to any one of claims 1 to 14, wherein step (b) and / or step (d) are carried out independently at a pressure in the range of 1 kPa to 10,000 kPa, or 10 kPa to 6,000 kPa, or 20 kPa to 4,000 kPa, or 50 kPa to 2,000 kPa, or 80 kPa to 1,500 kPa, or 90 kPa to 1,000 kPa, or 90 kPa to 600 kPa.

16. The method according to any one of claims 1 to 15, wherein the ratio of the BET surface area of ​​the particles formed in step (c) to the BET surface area of ​​the particles formed in step (b) is at least 1.1:1, or at least 1.2:1, or at least 1.3:1, or at least 1.4:1, or at least 1.5:1, or at least 2:1, or at least 3:1, or at least 4:1, or at least 5:

1.

17. The method according to any one of claims 1 to 16, wherein the ratio of the BET surface area of ​​the particles formed in step (c) to the BET surface area of ​​the particles formed in step (b) is 15:1 or less, or 14:1 or less, or 13:1 or less, or 12:1 or less.

18. The method according to any one of claims 1 to 17, wherein the ratio of the total pore volume of micropores and mesopores measured by gas adsorption of particles formed in step (c) to the total pore volume of micropores and mesopores measured by gas adsorption of particles formed in step (b) is at least 2:1, or at least 3:1, or at least 4:1, or at least 5:1, or at least 6:1, or at least 7:1, or at least 8:

1.

19. The method according to any one of claims 1 to 18, wherein the ratio of the total pore volume of micropores and mesopores measured by gas adsorption of particles formed in step (c) to the total pore volume of micropores and mesopores measured by gas adsorption of particles formed in step (b) is 20:1 or less, or 19:1 or less, or 18:1 or less, or 17:1 or less, or 16:1 or less, or 15:1 or less.

20. The method according to any one of claims 1 to 19, wherein the ratio of the total hydrogen content of the particles formed in step (c) to the total hydrogen content of the particles formed in step (b) is 0.8:1 or less, or 0.7:1 or less, or 0.6:1 or less, or 0.5:1 or less.

21. The method according to any one of claims 1 to 20, wherein the ratio of the total hydrogen content of the particles formed in step (c) to the total hydrogen content of the particles formed in step (b) is at least 0.1:1, or at least 0.2:1, or at least 0.3:

1.

22. The method according to any one of claims 1 to 21, wherein the inert gas used in step (c) is selected from the group consisting of nitrogen, argon, helium and combinations thereof.

23. The method according to claim 22, wherein the inert gas contains hydrogen.

24. The method according to any one of claims 1 to 23, wherein step (c) is carried out in the presence of nitrogen and hydrogen.

25. The method according to any one of claims 1 to 24, wherein the temperature in step (c) is higher than the temperature in step (b), and optionally, the temperature in step (c) is at least 20°C, at least 40°C, at least 60°C, at least 80°C, at least 100°C, at least 120°C, at least 140°C, or at least 150°C higher than the temperature in step (b).

26. The method according to any one of claims 1 to 25, wherein the temperature in step (c) is at least 450°C, or at least 500°C, or at least 510°C, or at least 520°C, or at least 540°C, or at least 560°C, or at least 580°C, or at least 600°C, or at least 610°C, or at least 620°C, or at least 630°C, or at least 640°C, or at least 650°C, preferably the temperature in step (c) is at least 500°C, more preferably the temperature in step (c) is at least 510°C, and more preferably the temperature in step (c) is at least 520°C.

27. The method according to any one of claims 1 to 26, wherein the temperature in step (c) is 900°C or less, or 850°C or less, or 800°C or less, or 750°C or less, or 700°C or less, or 680°C or less, or 660°C or less, or 650°C or less, preferably the temperature in step (c) is 750°C or less, and more preferably the temperature in step (c) is 700°C or less.

28. The method according to any one of claims 1 to 27, wherein step (c) is performed for at least 1 minute, or at least 2 minutes, or at least 5 minutes, or at least 10 minutes, or at least 15 minutes, or at least 20 minutes, or at least 30 minutes, or at least 45 minutes, or at least 1 hour, or at least 2 hours, preferably for at least 30 minutes, more preferably for at least 1 hour, or more preferably for at least 90 minutes.

29. The method according to any one of claims 1 to 28, wherein step (c) is carried out for 72 hours or less, or 48 hours or less, or 24 hours or less, or 12 hours or less, or 6 hours or less, or 5 hours or less, or 4 hours or less, or 3 hours or less, preferably step (c) is carried out for 24 hours or less, more preferably step (c) is carried out for 12 hours or less, and more preferably step (c) is carried out for 6 hours or less.

30. The method according to any one of claims 1 to 29, wherein step (c) comprises maintaining the particles derived from step (b) above a lower threshold temperature TL of at least 400°C over time t, and preferably, step (c) comprises maintaining the particles derived from step (b) between the lower threshold temperature TL and the upper threshold temperature TU over time t.

31. The method according to claim 30, wherein the lower threshold temperature TL is 500°C, the upper threshold temperature TU is 700°C, and the time t is 90 minutes to 6 hours.

32. The method according to any one of claims 1 to 31, wherein step (c) and / or step (d) are repeated one or more times.

33. The weight ratio of silicon in the particles formed in step (d) to the porous particles is [0.50 × P １ ~1.9 x P １ ]: 1, or [0.6 × P １ ~1.8 x P １ ]: 1 or [0.7 × P １ ~1.7 x P １ ]: 1, or [0.8 × P １ ~1.6 x P １ ]: is in the range of 1, where P １ is, cm ３ The method according to any one of claims 1 to 32, wherein the dimensionless number is the same as the total pore volume of micropores and mesopores in the porous particle, as measured by gas adsorption, and is expressed as / g.

34. The method according to any one of claims 1 to 33, wherein the particles formed in the final step (d) contain silicon in an amount of 5% to 85% by weight, or 10% to 85% by weight, or 15% to 85% by weight, or 20% to 80% by weight, or 25% to 80% by weight, or 30% to 75% by weight, or 35% to 75% by weight, or 40% to 70% by weight, or 45% to 65% by weight, based on the total mass of the particles.

35. The method according to any one of claims 1 to 34, wherein the amount of silicon in the particles formed in the final step (d) accounts for at least 25% and up to 90% of the internal pore volume of the porous particles.

36. The method according to any one of claims 1 to 35, wherein at least 85% by weight, more preferably at least 90% by weight, more preferably at least 95% by weight, and more preferably at least 98% by weight of the silicon in the particles formed in the final step (d) is located within the internal pore volume of the porous particles.

37. The particles formed in the final step (d) are 0.1 m ２ / g to 100m ２ / g, or 0.1m ２ / g to 80m ２ / g, or 0.5m ２ / g ~ 60m ２ / g, or 0.5m ２ / g to 40m ２ / g, or 1m ２ / g to 30m ２ / g, or 1m ２ / g to 25m ２ / g, or 2m ２ / g to 20m ２ The method according to any one of claims 1 to 36, having a BET surface area in the range of / g.

38. The total pore volume of micropores and mesopores in the particles formed in the final step (d), as measured by gas adsorption, is 0.6 cm³. ３ / g or less, or 0.5cm ３ Less than or equal to 0.4 cm / g, or 0.4 cm ３ Less than or equal to 0.3 cm / g ３ Less than or equal to 0.2 cm / g, or 0.2 cm ３ Less than or equal to 0.1 cm / g, or 0.1 cm ３ The method according to any one of claims 1 to 37, wherein the amount is less than or equal to / g.

39. The total pore volume of micropores and mesopores in the particles formed in the final step (d), as measured by gas adsorption, is at least 0.01 cm³. ３ The method according to any one of claims 1 to 38, wherein the amount is / g.

40. The particles formed in the final step (d) are in the range of 1 μm to 30 μm. ５０ The method according to any one of claims 1 to 39, having a particle size.

41. The particles formed in the final step (d) are 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. １０ The method according to any one of claims 1 to 40, having a particle size.

42. D ９０ The method according to any one of claims 1 to 41, having a particle size.

43. (e) A step of bringing the surface of the particles derived from the final step (d) into contact with a passivation agent. The method according to any one of claims 1 to 42, further comprising:

44. The method according to claim 43, wherein the passivating agent is selected from (i) an oxygen-containing gas, (ii) ammonia, (iii) a gas containing ammonia and oxygen, (iv) phosphine, and (v) water.

45. The passivating agent is (i)R １ -CH=CH-R １ 、 ())) １ .≡.!R １ 、 (iii)O=CR １ R １ 、 (iv) HX-R ２ , and, (v)HX-C(O)-R １ (In the formula, X is O, S, NR) １ or PR １ This represents, Each R １ can independently represent H, or an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, or two R １ The group forms an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring. R ２ represents an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, or R １ and R ２ together form an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring), and is selected from The method according to claim 43.

46. The method according to claim 43, wherein the passivating agent is ethylene.

47. (f) A step of combining particles derived from the final step (d) or step (e) with a pyrolytic carbon precursor, and heating the pyrolytic carbon precursor to a temperature effective in causing the deposition of conductive pyrolytic carbon material in the pores and / or on the outer surface of the composite particles. The method according to any one of claims 1 to 46, further comprising:

48. A particulate material comprising only a plurality of composite particles that can be obtained by the method described in any one of claims 1 to 47.

49. A composition comprising the particulate material according to claim 48 and at least one other component.

50. An electrode comprising the particulate material according to claim 48 or the composition according to claim 49.

51. A rechargeable metal-ion battery comprising the electrode described in claim 50.

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