Particulate porous skeleton

Abstract

The present invention relates to the field of anode materials for metal-ion batteries, particularly lithium-ion batteries. A process is provided comprising the steps of (a) determining the effective size σ of a silicon precursor, and (b) providing a collection of optimized particulate porous frameworks having a pore structure optimized for the silicon precursor, comprising micropores and / or mesopores, wherein the optimized pore structure has a PD of 1.4σ to 3.0σ. 30 Pore ​​diameter and PD of 5.0σ to 14.0σ 90 Pore ​​diameter and pore diameter range (PD) of 4.0σ to 12.0σ 90 ~PD 10 ) and include, where "effective size σ" refers to the value of σ in the Lennard Jones potential of the silicon precursor, and "PD n "Pore diameter" refers to a pore diameter less than n% of the total volume of micropores and mesopores.

Description

[Technical Field]

[0001] introduction This invention relates to a particulate porous framework having an optimized pore structure. This framework is particularly suitable for preparing composite particles for use as an anode electroactive material in metal-ion batteries such as lithium-ion batteries. [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, which is defined herein as 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 intercalated lithium atoms. Thus, herein the terms “cathode” and “anode” are used in the sense that the battery is positioned on the opposite side of the load such that the anode is the negative electrode. herein the term “battery” is used to refer to both a device containing a single cell (e.g., a lithium-ion cell or a sodium-ion cell) and a device containing multiple connected cells.

[0003] Conventional lithium-ion batteries (LIBs) use graphite as the electroactive anode material. A graphite anode can accommodate up to one lithium atom for every six carbon atoms, giving a theoretical maximum specific capacity of 372 mAh / g for lithium-ion batteries, although the actual capacity is slightly lower (approximately 340-360 mAh / g). Silicon is a promising alternative to graphite due to its very high lithium capacity (see, for example, Insertion Electrode Materials for Rechargeable Lithium Batteries, Winter, M. et al. in Adv. Mater. 1998, 10, No. 10). The theoretical maximum specific capacity of silicon is... (Lithium-ion battery)15 The capacity is approximately 3,600 mAh / g (Si4-based). However, due to the very high ratio of intercalated lithium to silicon, the silicon material expands up to 400% of its original volume. Repeated charge and discharge cycles place significant mechanical stress on the silicon material, leading to breakage and structural failure. Furthermore, when the anode of a LIB is charged, a solid electrolyte interface (SEI) layer is formed. This SEI layer is an ionically conductive yet insulating layer formed by the reductive decomposition of the electrolyte on the electrode surface exposed during the initial charge. In graphite anodes, this SEI layer remains relatively stable during subsequent charge / discharge cycles. However, due to the expansion and contraction of the silicon anode, the SEI layer breaks and peels off, exposing a new silicon surface. As a result, the electrolyte decomposition progresses further, increasing the thickness of the SEI layer and irreversibly consuming lithium. These failure mechanisms work together to cause unacceptable losses of electrochemical capacity throughout continuous charge and discharge cycles.

[0004] One approach to address these problems reported by the inventors is to develop a class of electroactive materials having composite structures in which electroactive materials such as silicon are deposited within a pore network of highly porous particles, such as porous carbon materials, with a carefully controlled pore size distribution. For example, WO2020 / 095067, WO2020 / 128495, and WO2022 / 029422 report that the improved electrochemical performance of these materials is due to the electroactive materials forming small domains on the order of a few nanometers or less in size within the pore network of porous particles, which then function as a framework for the composite particles. First, since fine electroactive structures are thought to have lower resistance to elastic deformation and higher resistance to fracture than larger electroactive structures, lithiation and delithiation are possible without excessive structural stress. As a result, electroactive materials exhibit good reversible capacity retention over multiple charge-discharge cycles. Next, by controlling the silicon filling within the porous particle framework so that only a portion of the pore volume is occupied by silicon in the uncharged state, the pore volume of the porous particle framework can accommodate a considerable amount of silicon expansion internally. Excessive expansion is limited by the particle framework. Furthermore, only a small area of ​​the electroactive material surface can access the electrolyte, significantly preventing SEI formation.

[0005] However, a wide variety of raw materials and synthesis methods exist for obtaining porous materials used as the framework for this type of composite particle. While the inventors have reported desirable pore size distribution parameters for the framework, it can be difficult to determine which porous material is expected to provide a particularly advantageous framework for preparing the composite particles without the cumbersome process of producing many batches of composite particles and performing electrochemical tests on each. Therefore, it is necessary to further optimize the pore structure of the framework to further improve the properties of the composite particles prepared therefrom. Furthermore, it is necessary to efficiently and reliably evaluate whether new sources of porous frameworks are suitable for preparing composite particles with desirable properties for downstream applications of LIBs. [Overview of the project]

[0006] The present invention (a) A step of determining the effective size σ of the silicon precursor, (b) A process comprising the step of providing a collection of optimized particulate porous frameworks having a pore structure optimized for a silicon precursor, comprising micropores and / or mesopores, wherein the optimized pore structure is PD of 1.4σ to 3.0σ 30 Pore ​​diameter and PD of 5.0σ to 14.0σ 90 Pore ​​diameter and Pore ​​diameter span (PD) from 4.0σ to 12.0σ 90 ~PD 10 ) and, "Effective size σ" refers to the value of σ in the Lennard Jones potential of the silicon precursor. "PD n "Pore diameter" refers to the pore diameter below which n% of the total volume of micropores and mesopores exists.

[0007] The inventors discovered that when the pore size distribution is controlled within certain limits based on a multiple of the effective size of the silicon precursor, the pore structure of the framework is optimized for use with the silicon precursor. Thus, the framework is optimized for subsequent silicon deposition steps utilizing the silicon precursor, providing composite particles for use as electroactive materials in metal-ion batteries. The optimized pore structure facilitates the formation of composite particles with desirable properties for this application, such as a high percentage of surface silicon, as shown in the embodiments of the invention. Furthermore, the understanding provided by the inventors regarding a method for selecting porous frameworks having an optimized pore structure can be advantageously used to screen multiple sources of frameworks and multiple silicon precursors and select those expected to impart desirable properties to the composite particles.

[0008] The present invention provides an optimized particulate porous framework having a pore structure optimized for a silicon precursor, comprising micropores and / or mesopores.

[0009] The present invention also provides composite particles, such as those obtained from an optimized particulate porous framework and a silicon precursor. Therefore, the present invention preferably further includes the step of contacting the optimized particulate porous framework provided in step (b) with the silicon precursor of step (a) at a temperature effective for depositing elemental silicon in the pores of the optimized particulate porous framework, thereby providing composite particles. The present invention also provides electrodes containing composite particles, rechargeable metal-ion batteries containing the electrodes, and processes for producing them. [Brief explanation of the drawing]

[0010] [Figure 1] The TGA traces of the composite particles prepared from carbon skeletons C15 and C16 of Example 1 are shown. [Figure 2] The average surface silicon and PD30 values ​​of the composite particles prepared in Example 1 are shown. [Figure 3] The average surface silicon and PD90 values ​​of the composite particles prepared in Example 1 are shown. [Figure 4] The average surface silicon and (PD90~PD10) values ​​of the composite particles prepared in Example 1 are shown. [Figure 5] The surface silicon and PD30 values ​​of the composite particles prepared in Example 2 are shown. [Figure 6] The surface silicon and PD90 values ​​of the composite particles prepared in Example 2 are shown. [Figure 7] The surface silicon and (PD90~PD10) values ​​of the composite particles prepared in Example 2 are shown. [Figure 8] The surface silicon and PD30 values ​​of the composite particles prepared in Example 3 are shown. [Figure 9] The surface silicon and PD90 values ​​of the composite particles prepared in Example 3 are shown. [Figure 10] The surface silicon values ​​and (PD90~PD10) values ​​of the composite particles prepared in Example 3 are shown. [Modes for carrying out the invention]

[0011] It is understood that the process steps in this specification are labeled for ease of reference. The steps can be performed in any order, with or without other intervening steps, unless obviously incompatible. The descriptions below of particulate porous frameworks, silicon precursors, composite particles, electrodes, batteries, etc., apply equally when they are provided as products themselves or used as part of a process.

[0012] The optimized pore structure was determined by the inventors based on the fact that the deposition of silicon onto the porous framework can be efficiently carried out by a chemical vapor infiltration (CVI) process. This is a variation of chemical vapor deposition (CVD), where the decomposition surface is located within the pores of the porous framework. For the silicon precursor to be decomposed into silicon, the precursor must be able to enter the pores of the framework and move to the appropriate decomposition site. The desired framework generally includes a three-dimensionally interconnected open pore network, including micropores and / or mesopores, and optionally a small amount of macropores. According to conventional IUPAC terminology, in this specification, the term “micropore” refers to pores with a diameter of less than 2 nm, the term “mesopore” refers to pores with a diameter of 2 to 50 nm, and the term “macropore” refers to pores with a diameter greater than 50 nm.

[0013] The inventors have determined that the most suitable pore size for a porous framework to form high-performance composite particles after CVI is obtained by controlling the pore size based on the size of the silicon precursor. This is based on the recognition that the transport of silicon precursors within the porous framework is influenced by the pore diameter and the size of the precursor. As the pores become smaller, the interaction between the silicon precursor and the pore wall begins to control the behavior. For CVI to be successful in microporous and mesoporous systems, the silicon precursor must be able to enter the pores for adsorption; that is, the pores must be larger than the target molecule. To allow for the deposition of a meaningful amount of silicon, the precursor molecule must be able to move within the pores; that is, there must be extra space so that the precursor can be transported throughout the pore system without being hindered by already adsorbed precursor molecules. Also, after the precursor molecule has been decomposed, a minimum amount of space must be left so that further precursors can be transported and decomposed to form silicon. Substantively, the pores must be large enough to transport the precursor throughout the framework and have sufficient pore volume to accommodate the amount of silicon required for the application. However, when considering transport into pores, further factors arise, such as collisions between precursor molecules and the walls of the pore system. When pores are sufficiently narrow, the interaction between precursor molecules and pore walls becomes dominant in determining transport properties, and it is thought that adsorbed molecules are retained within the pores by dispersion forces with the walls. These interaction forces are considered to be a major consideration when the molecular size is on the same order of magnitude as the pore width. Therefore, the pore size span is also important, so that there are not too many pores that are too small or too large compared to the size of the precursor. Taking these considerations into account, the inventors determined that the pore structure is optimized for CVI based on a pore size distribution defined by a specific multiple of the size of the precursor.

[0014] As a silicon precursor, a gaseous silicon precursor is most preferred because it can be conveniently used in the CVI process. The gaseous silicon precursors include silane (SiH4), disilane (Si2H6), trisilane (Si3H8), tetrasilane (Si4H 10 ), pentasilane (Si5H 12 ), hexasilane (Si6H 14 ), methylsilane (CH3SiH3), dimethylsilane ((CH3)2SiH2), trimethylsilane ((CH3)3SiH), tetramethylsilane ((CH3)4Si), or chlorosilanes such as trichlorosilane ((HSiCl3) or dichlorosilane (H2SiCl2) or chlorosilane (H3SiCl), or methylchlorosilanes such as methyltrichlorosilane (CH3SiCl3) or dimethyldichlorosilane (((CH3)2SiCl2) and can be selected from them. Preferably, the silicon precursor is selected from silane (SiH4), disilane (Si2H6), trisilane (Si3H8), tetrasilane (Si4H 10 ). A particularly preferred silicon precursor is silane (SiH4). However, in one embodiment, the silicon precursor is not silane (SiH4), and optionally not silane (SiH4) or disilane (Si2H6) either.

[0015] The effective size σ of the silicon precursor is the value σ in the Lennard-Jones potential of the silicon precursor. σ is typically expressed in nm. The Lennard-Jones potential is a widely known intermolecular pair potential for the same particles in the gaseous state and is defined as follows:

Equation

[0016] The effective size is considered to remain unchanged by conditions such as temperature and pressure. Nevertheless, if necessary, the effective size can also be specified at room temperature (25°C) and atmospheric pressure (101,325 Pa).

[0017] Preferably, σ is in the range of 0.4 to 0.6 nm. The σ values ​​for many silicon precursors have been reported in the literature (Gorbachev et al., Technical Physics 2000, 45(8), 1032-1041; Noda et al., Int J Chem Kinet. 2021, 53, 1036-1049; J. Perrin et al., Contrib. Plasma Phys. 1996, 36(3), 3). The σ value can also be calculated from thermodynamic data available in literature such as Kee et al., CHEMKIN Collection, Release 3.6, Reaction Design, Inc., San Diego, CA (2000). The effective sizes of several silicon precursors are shown in the table below. Any of these precursors can be used in the present invention. [Table 1]

[0018] The optimized pore structure is PD of 1.4σ to 3.0σ, preferably 1.6σ to 3.0σ, 1.7σ to 2.8σ, or 1.8σ to 2.2σ 30 Pore ​​diameter and PD of 5.0σ~14.0σ, or 6.0σ~13.5σ, or 8.5σ~13.0σ 90 Pore ​​diameter and Pore ​​diameter span (PD) of 4.0σ to 12.0σ, or 4.5σ to 11.5σ, or 6.0σ to 11.0σ 90 ~PD 10 ) and include.

[0019] The optimized pore structure is defined according to the effective size of the silicon precursor. Thus, each silicon precursor with a different effective size gives a different optimized pore structure.

[0020] In certain cases, the optimized pore structure is PD of 1.6σ to 3.0σ 30 Pore ​​diameter and PD of 5.0σ to 14.0σ 90 Pore ​​diameter and Pore ​​diameter span (PD) from 4.0σ to 12.0σ 90 ~PD 10 )and, 0.4~1.8cm 3 Includes the total volume of micropores and mesopores in the range of / g.

[0021] In another example, the optimized pore structure is PD of 1.7σ to 2.8σ 30 Pore ​​diameter and PD of 6.0σ to 13.5σ 90 Pore ​​diameter and 4.5σ to 11.5σ pore size span (PD) 90 ~PD 10 ) and include.

[0022] In another example, the optimized pore structure is PD of 1.6σ to 3.0σ 30 Pore ​​diameter and PD of 5.0σ to 14.0σ 90 Pore ​​diameter and Pore ​​diameter span (PD) from 4.0σ to 12.0σ 90 ~PD 10 )and, 0.4~1.8cm 3 The total volume of micropores and mesopores in the range of / g includes, The particulate porous framework is D 50 It is a particulate porous carbon skeleton with a particle size of less than 30 μm. The silicon precursor in step (a) is a silane (SiH4) with an effective size σ of 0.408 nm.

[0023] The optimized pore structure is PD less than 4.0σ or less than 3.7σ 50 Pore ​​diameter, and PD of 3.75σ~8.0σ or 5.0σ~7.0σ 75 It may further include one or both of the pore diameters.

[0024] The optimized pore structure may include a unimodal, bimodal, or multimodal pore size distribution. As used herein, the term “pore size distribution” refers to the pore size distribution with respect to the cumulative total internal pore volume of the particulate porous framework. A bimodal or multimodal pore size distribution is preferred because the proximity between micropores and large pores provides the advantage of efficient ion transport through the porous network to the electroactive material.

[0025] Preferably, the bimodal or multimodal pore size distribution has peaks in at least two, and optionally all three, of the following regions: (i) 1.2σ to 1.7σ, (ii) 1.8σ to 2.1σ, and (iii) 2.2σ to 3.2σ. These peaks typically include at least two of the strongest peaks in the pore size distribution, and optionally all three of the strongest peaks. The intensity ratio of peak (i) to peak (iii) is preferably 0.5:1 or greater. The intensity ratio of peak (i) to peak (ii) is preferably less than 5:1.

[0026] In this specification, "PD" n The general term "pore diameter" refers to the volume-based n-th percentile pore diameter, which is based on the total volume of micropores and mesopores. For example, as used herein, "PD 50 The term "pore diameter" refers to the pore diameter below which 50% of the total volume of micropores and mesopores resides. To avoid ambiguity, PD n For the purpose of determining the value, macropore volume (pore diameter exceeding 50 nm) is not considered.

[0027] The total volume of micropores and mesopores, and the pore size distribution of micropores and mesopores (P as defined herein). 1 and PDn (Including pore size parameters) is calculated using rapid solid density functional theory (QSDFT) with nitrogen gas adsorption at 77K, where relative pressure p / p0 is 10 -6 The pore size distribution is determined, preferably according to the standard methodology specified in ISO 15901-2 and ISO 15901-3, most preferably ISO 15901-2:2022. Nitrogen gas adsorption is a technique for characterizing the porosity and pore size distribution of a material by condensing a gas into the pores of a solid. As the pressure increases, the gas first condenses in the smallest diameter pores, and the pressure increases until it reaches a saturation point where all pores are filled with liquid. The pressure of the nitrogen gas is then gradually decreased, causing the liquid to evaporate from the system. By analyzing the adsorption isotherms and desorption isotherms, and the hysteresis between them, the pore volume and pore size distribution can be determined. Suitable instruments for measuring pore volume and pore size distribution by nitrogen gas adsorption include the TriStar II and TriStar II Plus porosity analyzers available from Micromeritics Instrument Corporation, USA, and the Autosorb IQ porosity analyzer available from Quantachrome Instruments.

[0028] Nitrogen gas adsorption is effective for measuring pore volume and pore size distribution for pores with a diameter of up to 50 nm, but its reliability is low 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 a diameter of 50 nm or less (i.e., micropores and mesopores). PD n Similarly, the value is determined based solely on the total volume of micropores and mesopores.

[0029] 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 the particulate porous framework includes macropores, the volume of pores with diameters ranging from 50 nm to 100 nm can be measured by mercury porosimetry, preferably 0.3 cm³. 3Less than / g, or 0.2cm 3 Less than / g, or 0.1cm 3 Less than / g, or 0.05cm 3 The amount is less than / g. While small amounts of macropores may be useful for facilitating electrolyte access to the pore network, the advantages of the present invention are substantially obtained by accommodating the electroactive material in micropores and even smaller mesopores.

[0030] Pore ​​volumes measured by mercury porosimetry for pore sizes of 50 nm or less are ignored (as mentioned above, nitrogen adsorption is used to characterize mesopores and micropores). Pore volumes exceeding 100 nm measured by mercury porosimetry are considered to be interparticle porosity for the purposes of this invention and are therefore also ignored.

[0031] Mercury porosimetry is a technique for characterizing the porosity and pore size distribution of a material by applying varying levels of pressure to a sample of the material immersed in mercury. The pressure required to penetrate the pores of the sample with mercury is inversely proportional to the pore size. The values ​​obtained by the mercury porosimetry method reported herein were obtained according to ASTM UOP578-11, with a surface tension γ of 480 mN / m and a contact angle φ of 140° for mercury at room temperature. The density of mercury at room temperature was 13.5462 g / cm³. 3 It is said that numerous high-precision mercury porosimetry meters are commercially available, such as the AutoPore IV series of automated mercury porosimetry meters sold by Micromeritics Instrument Corporation, USA. For a complete review of mercury porosimetry, it is recommended to refer to "Analytical Methods in Fine Particle Technology," 1997, by PAWebb and C. Orr, Micromeritics Instrument Corporation, ISBN 0-9656783-0.

[0032] It is understood that penetration techniques such as gas adsorption and mercury porosimetry are only effective in determining the pore volume of pores that are accessible to nitrogen or mercury from outside the particulate porous framework. The porosity values ​​defined herein are understood to refer to open pores, i.e., pore volumes that are accessible to fluid from outside the particulate porous framework. Completely enclosed pores that cannot be identified by nitrogen adsorption or mercury porosimetry are not considered herein when determining porosity values. Similarly, pore volumes in pores so small that they are below the detection limit by nitrogen adsorption are not considered.

[0033] An optimized particulate porous framework can be characterized by the total volume of micropores and mesopores (i.e., the total pore volume in the pore size range of 0–50 nm). Typically, an optimized particulate porous framework contains both micropores and mesopores. However, the use of particulate porous frameworks that contain micropores but not mesopores, or conversely, those that contain mesopores but not micropores, is not ruled out.

[0034] The optimized pore structure is defined according to the effective size of the silicon precursor. However, the optimized pore structure can be further defined by an absolute value that is considered advantageous for use with various silicon precursors and provides a particulate porous framework that is favorable for end-uses of LIBs. The optimized pore structure is preferably at least 0.4 cm². 3 / g, or at least 0.5cm 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 This includes the total volume of micropores and mesopores per gram. Using highly porous particles can be advantageous because it allows for the accommodating of more electroactive material within the pore volume.

[0035] The internal pore volume of the optimized particulate porous framework is appropriately limited to a value where the increased fragility of the framework structure outweighs the benefits of increased pore volume in accommodating more electroactive material. The optimized pore structure is 1.8 cm 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 1.35cm 3 Less than / g, or 1.3cm 3 Less than / g, or 1.25cm 3 Less than / g, or 1.2cm 3 Less than / g, or 1.1cm 3 It may contain volumes of micropores and mesopores less than or equal to / g.

[0036] Preferably, the optimized pore structure is 0.4 to 1.8 cm 3 / g, or 0.4-1.7cm 3 / g, or 0.5-1.6cm 3 / g, or 0.5-1.55cm 3 / g, or 0.6-1.5cm 3 / g, or 0.6-1.45cm 3 / g, or 0.65-1.4cm 3 / g, or 0.65-1.35cm 3 / g, or 0.7-1.3cm 3 / g, or 0.7-1.25cm 3 / g, or 0.75-1.2cm 3 / g, or 0.75-1.1cm 3 / g, or 0.8-1.2cm 3 / g, or 0.8-1.1cm 3 This includes the total volume of micropores and mesopores in the range of / g.

[0037] The optimized pore structure is preferably at least 0.3 cm 3 / g, or at least 0.4cm 3 / g, or at least 0.5 cm 3 / g, or at least 0.6 cm 3 It may include a micropore volume of / g.

[0038] The micropore volume fraction of the optimized pore structure can 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, and / or 0.95 or less, or 0.9 or less, or 0.85 or less, or 0.8 or less, based on the total volume of micropores and mesopores within the optimized particulate porous framework.

[0039] The optimized pore structure may have a mode pore diameter of micropores and mesopores of 0.50 nm or more, preferably 0.60 nm or more.

[0040] The total volume of micropores and mesopores (i.e., the total pore volume of pores having a diameter in the range of 0 to 50 nm) is P 1 cm 3 / g and can be referred to as such. When the particulate porous framework contains macropores, the pore volume in the range exceeding 50 nm up to 100 nm can be referred to as P 2 cm 3 / g and is measured by mercury porosimetry. The macropore volume (and thus the value of P 2 ) is preferably small compared to the volume of micropores and mesopores (and thus the value of P 1 ). A small amount of macropores can be useful for facilitating the access of electrolytes to the pore network, but the advantages of the present invention are substantially obtained by accommodating silicon in micropores and smaller mesopores. Therefore, in the optimized pore structure, P 2 preferably has a value of at most 0.2 × P 1 , or at most 0.1 × P 1 , or at most 0.05 × P 1 , or at most 0.02 × P 1 , or at most 0.01 × P 1 , or at most 0.005 × P 1 .

[0041] One of the advantages of the present invention is that by determining the optimized pore structure, a convenient and effective method is obtained to evaluate whether a novel particulate porous framework source can be used as a starting material for preparing composite particles having excellent properties for use in metal-ion batteries. This can be achieved by measuring the pore structure of the framework by conventional means, for example, as described herein, and determining whether an optimized pore structure exists, without requiring the expensive and time-consuming step of depositing silicon in the framework and performing electrochemical tests to evaluate the performance of the resulting composite particles. If an optimized pore structure exists, the framework is acceptable for subsequent use. If an optimized pore structure does not exist, the framework is unacceptable. Next, the pore structures of different frameworks can be measured. Once a population of optimized particulate porous frameworks has been identified, silicon can be deposited in the pores using the silicon precursor of step (a), thereby obtaining composite particles.

[0042] Therefore, step (b) is, (b1) Providing a collection of one or more particulate porous frameworks including micropores and / or mesopores, (b2) A step of measuring the pore structure of each group, (b3) A step of accepting each group having an optimized pore structure and not accepting each group not having an optimized pore structure, (b4) Using one or more of the accepted populations as an optimized population of particulate porous skeletons, or if no population is accepted, repeating steps (b1), (b2), and (b3) for further populations of particulate porous skeletons including micropores and / or mesopores until a population is accepted.

[0043] A collection of silicon precursors and optimized particulate porous frameworks may be provided as a kit. The components of the kit may be held separately until silicon is deposited into the pores of the optimized particulate porous framework using the silicon precursor.

[0044] A special advantage of the present invention is that multiple populations of particulate porous frameworks can be screened. Therefore, preferably, at least two populations are provided in step (b1), and at least one of them is optionally rejected in step (b3). The act of rejecting a population of particulate porous frameworks provides a useful technical lesson in that it eliminates the need for further testing of that population.

[0045] After measuring the pore structure of 10 randomly selected populations, the process can be stopped if no population is acceptable. Thus, the 10 unaccepted populations still provide useful information, indicating that they do not possess a pore structure optimized for the silicon precursor.

[0046] Another advantage of the present invention is that silicon precursors can be optimized into usable particulate porous frameworks without requiring the expensive and time-consuming steps of depositing silicon within a framework from multiple different precursors and performing electrochemical tests to evaluate the performance of the resulting composite particles. Thus, if a particular source of particulate porous framework proves desirable for other reasons, such as low cost and / or availability on a large scale, that source can be used together with an optimized silicon precursor to provide composite particles with excellent properties for use in metal-ion batteries.

[0047] Therefore, the process of the present invention is (a1) To provide one or more silicon precursors, (a2) Determine the effective size σ of each silicon precursor, (b5) To provide a group of particulate porous skeletons including micropores and / or mesopores, (b6) Measuring the pore structure of the population, (a3) Accepting each silicon precursor having an effective size such that the pore structure is optimized for the silicon precursor, and not accepting each silicon precursor having an effective size such that the pore structure is not optimized for the silicon precursor, (a4) If the silicon precursor is not accepted, the process is repeated with further silicon precursors until a silicon precursor is accepted.

[0048] Once the silicon precursor is accepted in step (a3), the collection of particulate porous skeletons provided in step (b5) is understood to be the optimized particulate porous skeleton provided in step (b). The accepted silicon precursor and the optimized particulate porous skeleton can then be provided as a kit. The components of the kit can preferably be held separately until silicon is deposited into the pores of the particulate porous skeleton using the accepted silicon precursor.

[0049] A special advantage of the present invention is that multiple silicon precursors can be screened. Thus, in step (a1), at least two silicon precursors are provided, and at least one of them is optionally rejected in step (a3). The act of rejecting a silicon precursor provides a useful technical lesson in that it does not need to be used in further testing of the population of particulate porous frameworks.

[0050] After optionally determining the effective size σ of 10 silicon precursors, the process can be stopped if the silicon precursors are unacceptable. Thus, useful information is still provided that the particulate porous framework does not have an optimized pore structure for the 10 silicon precursors that were not accepted.

[0051] One advantage of the present invention is that it is not necessary to provide all possible particulate porous skeletons on an industrial scale before knowing whether they are suitable for the end use, and the identity of the optimized particulate porous skeleton can be determined on a laboratory scale. For example, the population of optimized particulate porous skeletons provided in steps (b), (b1), and (b5) may be less than 50 kg or less than 10 kg. Once the optimized particulate porous skeletons have been identified in the laboratory, they can be made available on a larger scale with the confidence that they are suitable for producing large quantities of composite particles with excellent properties. Thus, the process of the present invention preferably further includes providing a further population of optimized particulate porous skeletons on an industrial scale. The industrial scale can be defined as at least 100 kg, preferably at least 1,000 kg, of the optimized particulate porous skeleton. A kit may be provided that includes a further population and a silicon precursor.

[0052] Generally, the particulate porous skeleton has a D 50 particle size in the range of less than 100 μm, or less than 30 μm, preferably 1 to 30 μm. Optionally, the D 50 particle size of the particulate porous skeleton can 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 50 particle size of the particulate porous skeleton can 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 1 μm or less, or 8 μm or less.

[0053] The D 10 particle size of the particulate porous skeleton 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. By maintaining the D 10 particle size at 0.5 μm or more, the possibility of undesirable aggregation of submicron-sized particles is reduced, and the dispersibility of the formed composite particles is improved.

[0054] D of particulate porous skeleton 90 The particle size is preferably 50 μm or less, or 40 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less, or 15 μm or less.

[0055] The particulate porous framework preferably has a narrow size distribution span. For example, the particle size distribution span ((D 90 ~D 10 ) / D 50 The size distribution (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. Maintaining a narrow size distribution span makes it easier to efficiently pack particles into a high-density powder bed.

[0056] As used herein, the term “particle diameter” refers to the equivalent diameter (ESD), i.e., the diameter of a sphere having the same volume as a given particle, and particle volume is understood to include the volume of pores within any particle. 50 " and "D 50 The term "particle diameter" refers to the volume-based median particle diameter, i.e., the diameter below which 50% of the volume of a particle population lies. 10 " and "D 10 The term "particle diameter" refers to the volume-based 10th percentile median particle diameter, i.e., the diameter below which 10% of the volume of a particle population lies. 90 " and "D 90 The term "particle diameter" refers to the 90th percentile median particle diameter based on volume, i.e., the diameter below which 90% of the volume of a particle population lies.

[0057] Particle diameter and particle size distribution can be determined by standard laser diffraction according to ISO 13320:2009. Laser diffraction is based on the principle that particles scatter light at different angles depending on their size, and the aggregate of particles generates a pattern of scattered light defined by intensity and angle, which correlates with the particle size distribution. Numerous laser diffraction devices are commercially available for rapid and reliable measurement of particle size distribution. Unless otherwise stated, the particle size distribution measurements specified or reported herein were measured using a conventional Malvern Mastersizer™ 3000 particle size analyzer from Malvern Instruments™. The Malvern Mastersizer™ 3000 particle size analyzer operates by projecting a helium-neon gas laser beam through a transparent cell containing target particles suspended in an aqueous solution. The light rays striking the particles are scattered at angles inversely proportional to the particle size, a photodetector array measures the intensity of the light at several predetermined angles, and the intensities measured at different angles are processed by a computer using standard theoretical principles to determine the particle size distribution. The laser diffraction values ​​reported herein are obtained using a wet dispersion of particles in 2-propanol with 5 volume% of the surfactant SPAN(trademark)-40 (sorbitan monopalmitate). The refractive index of the particles is assumed to be 2.68 for particulate porous frameworks and 3.50 for composite particles, while the refractive index of the dispersant is assumed to be 1.378. The particle size distribution is calculated using a Mie scattering model.

[0058] The particulate porous framework may have an average sphericity (as defined herein) greater than 0.5. Preferably, they have an average sphericity of at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, or at least 0.8, or at least 0.85. Preferably, the particulate porous framework has 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 enhance depositional uniformity and promote high-density packing both in batch pressure reactors and in the final product incorporated into electrodes.

[0059] High-precision two-dimensional projections of micron-scale particles can be obtained using scanning electron microscopy (SEM) or dynamic image analysis, which records the shadows projected by particles with a digital camera. As used herein, the term "sphericity" is understood as the ratio of the particle projection area (obtained from such imaging techniques) to the area of ​​a circle, where the particle projection area and the circumference of the circle are equal. Therefore, the sphericity S of an individual particle is defined as follows:

number

number

[0060] The particulate porous framework preferably has a thickness of at least 100 m 2 / g, or at least 500m 2 / g, or at least 750m 2 / g, or most preferably at least 1,000m2 / g, or at least 1,250m 2 / g, or at least 1,500m 2 It has a BET surface area of ​​4,000 m² / g. As used herein, the term "BET surface area" is interpreted to mean the surface area per unit mass calculated from measurements of physicoadsorption of gas molecules on a solid surface using the Brunauer-Emmett-Teller theory according to the ISO 9277 method (e.g., ISO 9277:2022). Preferably, the BET surface area of ​​the particulate porous framework is 4,000 m² / g. 2 Less than / g, or 3,500m 2 Less than / g, or 3,250m 2 / g or less, or 3,000m 2 Less than / g, or 2,500m 2 / g or less, or 2,000m 2 It is less than / g. For example, particulate porous framework is 100m 2 / g 10~4,000m 2 / g, or 500m 2 / g~4,000m 2 / g, or 750m 2 / g~3,500m 2 / g, or 1,000m 2 / g~3,250m 2 / g, or 1,000m 2 / g~3,000m 2 / g, or 1,000m 2 / g~2,500m 2 / g, or 1,000m 2 / g~2,000m 2 It may have a BET surface area in the range of / g.

[0061] The particulate porous framework preferably has a particle density of at least 0.35, or 3 g / cm³. 3 Preferably less than 2 g / cm³ 3 It is more preferable to be less than 1.5 g / cm³. 3 It is even more preferable that it be less than 0.35 to 1.2 g / cm³. 3It is most preferable that the particulate porous framework has a 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 has a particle density of 1.15 g / cm³. Preferably, the particulate porous framework has 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 3 The following, or 0.95 g / cm³ 3 The following, or 0.9 g / cm³ 3 It has the following particle density.

[0062] The particulate porous framework preferably comprises a conductive material. The use of a conductive particulate porous framework is advantageous because it forms a conductive framework within the composite particles and facilitates the flow of electrons between the lithium atoms / ions inserted into the electroactive material and the current collector.

[0063] A preferred type of particulate porous skeleton includes or consists of a conductive carbon material, which is referred to herein as a conductive particulate porous carbon skeleton.

[0064] The particulate porous framework preferably contains at least 80% by weight of carbon, more preferably at least 85% by weight of carbon, more preferably at least 90% by weight of carbon, more preferably at least 95% by weight of carbon, and optionally at least 98% by weight or at least 99% by weight of carbon. The carbon may be crystalline carbon, amorphous carbon, or a mixture of amorphous and crystalline carbon. The porous carbon particles may be hard carbon particles or soft carbon particles.

[0065] As used herein, the term “hard carbon” refers to a nanoscale polycyclic aromatic domain in which carbon atoms are primarily sp 2 This refers to a disordered carbon matrix that exists in a hybrid state (three-way bond). Polycyclic aromatic domains are cross-linked by chemical bonds such as COC bonds. Due to the chemical cross-linking between polycyclic aromatic domains, hard carbon cannot be converted to graphite even at high temperatures. Hard carbon has large G bonds in its Raman spectrum (approximately 1600 cm⁻¹). -1 It has graphite-like properties, as evidenced by the following: However, the prominent D bond in the Raman spectrum (approximately 1350 cm⁻¹) -1 As demonstrated by [the relevant source], carbon is not entirely graphite. As used herein, "soft carbon" refers to a polycyclic aromatic domain with dimensions in the range of 5 to 200 nm in which carbon atoms are primarily sp[T]. 2 This also refers to a disordered carbon matrix that exists in a hybrid state (three-way bonding). In contrast to hard carbon, the polyaromatic domains of soft carbon are bound together by intermolecular forces but are not cross-linked by chemical bonds. This means that it graphitizes at high temperatures. The porous carbon particle skeleton has at least 50% sp² as measured by XPS. 2 It is preferable that it contains hybrid carbon. For example, the particulate porous carbon skeleton preferably contains 50% to 98% sp 2 Hybrid carbon, 55%~95% sp 2 Hybrid carbon, 60%~90% sp 2 Hybrid carbon, or 70-85% sp 2 It may contain hybrid carbon.

[0066] When the particulate porous framework is a particulate porous carbon framework, the optimized particulate porous carbon framework has a ratio of the relative intensities of the D peak to the G peak (I) when measured by Raman spectroscopy. D / I G ) may be 2.0 or less or 1.8 or less. Alternatively or additionally, an optimized particulate porous carbon framework I D / I G I can be 1 or greater or 1.05 or greater. For example, I of an optimized particulate porous carbon skeleton D / I G This can be in the range of 1.0 to 1.6.

[0067] Providing a particulate porous skeleton includes synthesizing the skeleton and obtaining the skeleton from a supplier. Most preferably, the particulate porous skeleton is a particulate porous carbon skeleton. The particulate porous carbon skeleton used in the present invention is most preferably in the form of activated carbon. The term "activated carbon" refers to a carbonaceous material that has been physically or chemically treated to increase its porosity and surface area. Chemical or physical activation (e.g., high-temperature steam or CO2) mechanisms are one of the common methods used to produce activated carbon. A suitable activation process involves contacting pyrolyzed carbon with one or more of oxygen, steam, CO, and CO2 at a temperature range of 300-1500°C, 600-1200°C, or 600-1000°C. Mesopores can also be obtained by known template 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 pyrolysis or activation. Depending on the starting materials and the conditions of the pyrolysis process, various different particulate porous carbon skeletons are available in the art. Particulate porous carbon skeletons of various different specifications are available from commercial suppliers.

[0068] Various carbonaceous materials can be used to prepare a suitable particulate porous carbon skeleton via pyrolysis. Preferably, plant sources are used. Examples of plant sources include seeds, nuts, and the shells and husks of fruits (including drupes, kernels, and seeds). Examples of these plant sources include coconut shells and husks (including coir), peanuts, walnuts, apricots, almonds, palm seeds, peaches, olives, hazelnuts, bamboo, and tree bark (e.g., bark of conifers including pine, spruce, larch, and poplar, and bark of broad-leaved trees including oak). A preferred plant source is coconut shell. Fossil carbon sources such as coal may be used. Examples of resins and polymer materials as carbonaceous materials include phenolic resins, novolac resins, pitch, melamine, polyacrylates, polystyrene, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers containing monomer units of acrylates, styrene, α-olefins, vinylpyrrolidone, and other ethylenically unsaturated monomers.

[0069] The carbonaceous material, such as a plant source, preferably has an elemental composition containing at least 40 wt% carbon, at least 3 wt% hydrogen, and at least 30 wt% oxygen. Trace amounts of nitrogen, sulfur, and chlorine may also be present. More preferably, the carbonaceous material has an elemental composition containing about 50 wt% carbon, about 5 wt% hydrogen, and about 40 wt% oxygen, with smaller amounts of nitrogen, sulfur, and chlorine. Particulate porous carbon skeletons are typically obtained from the carbonaceous material in a two-step process. First, the carbonaceous material is heated and thermally decomposed in an inert atmosphere. The inert atmosphere can be nitrogen, CO2, noble gases, or mixtures thereof. The thermal decomposition is usually carried out at a temperature of about 400-900°C, or about 500-700°C, or about 550-700°C, so that dehydration and devolatilization of carbon occur. Preferably, the temperature does not exceed about 700°C. Optionally, the carbonaceous material is pre-treated to remove impurities before heating. Optionally, the carbonaceous material is purified and / or washed and dried before heating. Optionally, the carbonaceous material is sieved, crushed or ground to obtain particles of uniform size before heating. Optionally, the carbonaceous material is pelletized before heating.

[0070] Next, the pyrolyzed material is activated by heating it at a temperature of 600°C to 1200°C in a flow of one or more of oxygen, steam, CO, and CO2. This causes a chemical reaction between the carbon and the flowing gas to occur on the internal surface of the carbon, removing carbon from the pore walls and increasing the pore volume. This gas activation process is also called a physical activation process and can easily change the pore size to produce activated carbon with the desired porosity. Preferably, the pyrolyzed material is activated with steam.

[0071] Physical activation can be appropriately carried out in a rotary furnace, fixed-bed reactor, or fluidized-bed reactor. Optionally, additional washing, cleaning, or purification steps may be performed after activation. Optionally, the pyrolysis and activation steps may be combined into a continuous process. Optionally, the activated material may be crushed (e.g., ground) and / or sieved after the activation step to obtain particles of the desired size.

[0072] The combustion rate of the pyrolysis material during activation is preferably at least 30%, or at least 40%. The combustion rate is preferably 80% or less, or 75% or less, or 70% or less. The combustion rate is the mass fraction of the pyrolysis material removed during the physical activation step, and is expressed as a percentage of the material mass before the physical activation was initiated.

[0073] In chemical activation methods, carbonaceous materials are impregnated with chemical activators (e.g., NaOH, KOH, K2CO3, H3PO4, CaCl2, ZnCl2, and mixtures thereof). While carbonaceous materials may be carbonized before chemical impregnation, typically, they are impregnated before thermal decomposition, with the thermal decomposition step occurring simultaneously with the activation. Thermal decomposition for chemical activation can be carried out at 250–1000°C or 500–950°C. When porous carbon is formed using a chemical activation process, the activation mechanism works by expanding existing pores or spreading (exfoliating) the graphene sheet, rather than generating pores through carbon removal, and does not help maintain a high percentage of micropore space accessible through narrow channels / openings. This is thought to result in relatively reduced electrochemical performance of composite materials prepared from chemically activated porous carbon materials. Therefore, particulate porous carbon skeletons are preferably prepared by physical activation.

[0074] A typical example of activated carbon synthesis is as follows:

[0075] Synthetic activated carbon is prepared from a mixture of novolac resin and 11% hexamethylenetetramine powder (Bakelite PF 6705 FP, manufactured by Hexion GmbH). This starting material is crosslinked at 150°C for 1 hour, and the resulting solid block of crosslinked material is crushed to a size of 2-3 cm, and then crushed into particles of approximately 100 μm. Next, this cured resin powder is thermally decomposed at 800°C for 10 minutes under 1 L / min of nitrogen gas. The carbon yield obtained from this precursor is 57-59%. After carbonization, the carbon is ball-milled to a particle size of 3-4 μm, and the resulting carbon material is 0.20-0.22 cm². 3 0.25-0.3 cm² containing fine porosity / g 3 Total pore volume per gram and 650-700 m 2 It has a surface area of ​​0.8-0.9 cm². Next, this carbon is activated with vapor or CO₂ to achieve the desired pore volume. 3The typical activation temperature used for CO2 activation to achieve a total pore volume of / g is 950-980°C, with a residence time of 5-8 hours depending on the amount of carbon to be activated, the CO2 flow rate, and the type of furnace used. The temperature used for steam activation is lower than that for CO2, typically 850°C, because steam is more reactive. The residence time at the steam activation temperature varies depending on the type and amount of charcoal to be activated, the steam flow rate, and the type of furnace used, but is typically 6-9 hours.

[0076] Examples of activated carbon produced by steam activation are as follows:

[0077] Total pore volume is 0.79 cm³ 3 To produce a vapor-activated synthesis scaffold at / g, vapor is introduced via a humidifier consisting of a nitrogen atomizer (3 bar injection pressure) through a 1 mm orifice positioned perpendicular to a 1 mm orifice, water is added to the atomization chamber in droplet form, and atomization is induced by the high-pressure nitrogen flow causing the high-pressure gas to collide with the water droplets. To prevent accidental vapor condensation, heating tapes are used at the inlet and outlet. Carbohydrate phenolic resin is processed using a planetary ball mill. 50 The material is ball-milled to 3μm (60g load, 105, 10mm balls, 300RPM, 20-minute intervals). Next, 15g of the ground carbide phenol resin is placed in a short alumina crucible, and the material is spread evenly along the crucible. Steam activation is performed in a tubular furnace with the crucible placed in the center of the heating zone. The furnace is purged with 0.8L / min of N2 for 10-30 minutes. A heating rate of 8.7°C / min is used with a set point of 850°C. When the temperature reaches 840°C, water is injected into the spray nozzle at a rate of 0.25mL / min (water injection rate), and the temperature stabilizes when it reaches 850°C. This is held for 345 minutes. Once the holding is complete, the steam flow rate is set to zero and the heating tape is turned off.

[0078] Alternatives to the particulate porous carbon skeleton include particulate porous skeletons comprising titanium nitride, titanium carbide, silicon carbide, boron carbide, nickel oxide, silicon oxide, silicon dioxide, aluminum oxide, silicon-aluminum ternary oxide, magnesium oxide, lead oxide, zirconium oxide, silicon nitride, titanium silicon nitride, nickel nitride, molybdenum nitride, titanium oxynitride, silicon oxycarbide, boron nitride, or vanadium nitride. Preferred alternatives to the particulate porous carbon skeleton are particulate porous skeletons of titanium nitride, silicon oxycarbide, or boron nitride.

[0079] The process of the present invention preferably further comprises the step of (c) contacting the optimized particulate porous framework provided in step (b) with the silicon precursor of step (a) at a temperature effective for depositing elemental silicon in the pores of the optimized particulate porous framework, thereby providing composite particles. In this way, composite particles used as electroactive materials for metal-ion batteries are prepared.

[0080] Particulate porous frameworks typically provide a silicon framework deposited in the form of multiple electroactive domains. The term "electroactive domain" refers to the body of the electroactive material (e.g., elemental silicon), whose maximum dimension is determined by the dimensions of the micropores and / or mesopores in the particulate porous framework in which they reside. Thus, electroactive domains can be described as nanoscale electroactive domains, and the term "nanoscale" is generally understood to refer to dimensions less than 100 nm, however, due to the dimensions of micropores and mesopores, electroactive domains typically have a maximum dimension of less than 50 nm in any direction, and are usually well below 50 nm. Domains can take the form of, for example, regular or irregular particles, or layers or regions with coating boundaries.

[0081] Step (c) is appropriately carried out by chemical vapor infiltration (CVI) of a gaseous silicon precursor into the pore structure of the particulate porous framework. As used herein, CVI refers to the process by which the gaseous precursor is thermally decomposed on the surface, forming elemental silicon and gaseous byproducts on the surface. If the precursor is a chlorinated compound such as chlorosilane, the precursor is used in mixture with hydrogen gas, preferably in such a way that the atomic ratio of hydrogen to chlorine is at least 1:1.

[0082] Optionally, the precursor is chlorine-free. Chlorine-free means that the amount of chlorine-containing compound in the precursor is less than 1% by weight, preferably less than 0.1% by weight, and preferably less than 0.01% by weight.

[0083] The gaseous silicon precursor can be used in a pure form (or substantially pure form) or as a diluted mixture with an inert carrier gas such as nitrogen or argon. Preferably, step (c) involves contacting an optimized particulate porous framework with a gas containing 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 gaseous silicon precursor, based on the total volume of the gas.

[0084] In accordance with conventional procedures for working in an inert atmosphere, the presence of oxygen in step (c) should be avoided to prevent undesirable oxidation of the deposited electroactive material. Preferably, the oxygen content is less than 0.01% by volume, and more preferably less than 0.001% by volume, based on the total volume of gas used in step (c).

[0085] The temperature in step (c) is preferably in the range of 180 to 520°C, or 340 to 500°C, or 350 to 480°C, or 350 to 450°C, or 350 to 420°C, or less than 350 to 400°C, or 355 to 395°C, or 360 to 390°C, or 360 to 385°C, or 360 to 380°C.

[0086] The pressure in step (c) is preferably in the range of 1 to 5000 kPa, or 20 to 500 kPa, or 40 to 200 kPa, or 50 to 150 kPa, or 60 to 120 kPa, or 80 to 100 kPa. Preferably, the pressure in step (b) is maintained at 200 kPa or less, or 150 kPa or less, or 120 kPa or less, or 110 kPa or less, or 100 kPa or less, or 90 kPa or less, or 80 kPa or less. Any reference to pressure in any step of the claimed process refers to the absolute pressure within the reaction zone, which may include any suitable form of reactor vessel.

[0087] The deposition of electroactive material by CVI removes byproducts, particularly byproduct gases such as hydrogen. Step (c) preferably further includes separating the byproducts from the particles formed in step (c). Separation of byproducts can be carried out by flushing the reactor with an inert gas and / or by reducing the pressure and evacuating the reactor. For example, separation of byproducts from the particles formed in step (c) can be carried out by evacuating 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. Evacuating the reactor to a low pressure may be effective not only in removing byproducts in the gas phase but also in desorbing byproducts that may be adsorbed on the surface of the deposited silicon.

[0088] The silicon content in the composite particles can be obtained in a variety of ranges. The composite particles preferably contain at least 26% by weight of silicon, or at least 28% by weight of silicon, or at least 30% by weight of silicon, or at least 32% by weight of silicon, or at least 34% by weight of silicon, or at least 36% by weight of silicon, or at least 38% by weight of silicon, or at least 40% by weight of silicon, or at least 42% by weight of silicon, or at least 44% by weight of silicon. In any case, the composite particles may contain up to 70% by weight of silicon.

[0089] The amount of elemental silicon in the composite particles is preferably selected such that elemental silicon occupies at least 20% and up to 90% of the internal pore volume of the optimized particulate porous framework after step (c). For example, elemental silicon can occupy 20% 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 optimized particulate porous framework. Within these preferred ranges, the remaining pore volume of the optimized particulate porous framework is effective in accommodating the expansion of the electroactive material during charging and discharging without a large excess pore volume that does not contribute to the volumetric capacity of the composite particles. However, the amount of electroactive material is also not so large that it hinders effective lithiation due to insufficient metal ion diffusion rate or mechanical resistance to lithiation due to insufficient expansion volume.

[0090] The amount of silicon in the composite particles is such that the mass ratio of silicon to the optimized particulate porous framework is [0.5 × P 1 ~1.9×P 1 The requirement that ]:1 is within the range can be related to the available pore volume within the optimized particulate porous framework, P 1 This is a dimensionless quantity that represents the size of the total pore volume of micropores and mesopores within the optimized particulate porous framework, and is cm 3 Expressed as / g (for example, the total volume of micropores and mesopores in an optimized particulate porous framework is 1.2 cm³). 3In the case of / g, P 1 (=1.2). This relationship defines the weight ratio of silicon where the pore volume accounts for approximately 20% to 82%, taking into account the silicon density and the pore volume of the optimized particulate porous framework. Preferably, the weight ratio of silicon deposited in step (c) to the optimized particulate porous framework 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 ]: The range is 1.

[0091] The amount of silicon in the composite particles can be determined by elemental analysis. The silicon content is preferably determined by ICP-OES (inductively coupled plasma atomic emission spectrometry). Numerous ICP-OES instruments are commercially available, such as the iCAP® 7000 series ICP-OES analyzers from ThermoFisher Scientific. The carbon content (and hydrogen, nitrogen, and oxygen content, if necessary) of the composite particles and the optimized particulate porous framework alone is preferably determined by IR absorption. A suitable instrument for determining the carbon, hydrogen, nitrogen, and oxygen content is the TruSpec® Micro elemental analyzer, available from Leco Corporation.

[0092] Preferably at least 90% by weight, more preferably at least 95% by weight, and even more preferably at least 98% by weight of elemental silicon in the composite particles are located within the internal pore volume of the optimized particulate porous framework, resulting in the absence or very small amount of electroactive material on the outer surface of the optimized particulate porous framework. As described above, the deposition of electroactive material in the CVI process occurs on the surface of the particulate porous framework. Given the very large internal surface area of ​​the particulate porous framework, the reaction kinetics of the CVI process ensure that the deposition of electroactive material occurs almost completely within the pores of the particulate porous framework.

[0093] Internal deposition of the electroactive material is further improved by the requirement that the pressure in step (c) is maintained below 200 kPa or within the more preferable pressure range described above.

[0094] The composite particles obtained by the method of the present invention can be characterized by their performance by 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 high temperatures.

[0095] Generally, atoms on a material's surface are known to have different bonding interactions than atoms within the material, and this difference is usually explained by the material's surface energy. In the case of silicon deposited by chemical vapor deposition (CVI), the free valence of silicon atoms on the surface generally includes hydride groups. When this hydride-terminated silicon surface is exposed to air, it reacts with oxygen to form a native oxide surface. However, surfaces not exposed to air remain in the hydride-terminated state.

[0096] As used herein, "surface silicon" is calculated from the initial mass increase from the minimum value in the TGA trace between 150°C and 500°C to the maximum mass measured in the temperature range of 550°C and 650°C, where the TGA is performed in air at a temperature increase rate of 10°C / min. Since this mass increase is thought to be due to oxidation of surface silicon, the percentage of surface silicon to the total amount of silicon can be determined according to the following formula. Y = 1.875 × [(M 最大 -M 最小 ) / M f ] × 100% In the formula, Y is the percentage of surface silicon relative to the total silicon in the sample, M 最大 This is the maximum mass of the sample measured in the temperature range of 550°C to 650°C, M 最小 This is the minimum mass of the sample at temperatures between 150°C and 500°C, M fis the mass of the sample when oxidation is complete at 1400°C. For completeness, it will be understood that 1.875 is the molar mass ratio of SiO2 to O2 (i.e., the ratio of the mass of SiO2 formed to the mass increase due to the addition of oxygen). Typically, TGA analysis is performed using a sample size of 10 mg ± 2 mg.

[0097] It has been found that when the surface silicon measured by the TGA method described above is 20% by weight or more of the total silicon amount in the composite particles, reversible capacity retention over multiple charge / discharge cycles is significantly improved. Therefore, preferably, at least 20% by weight, or at least 22% by weight, or at least 25% by weight, or at least 30% by weight, or at least 35% by weight of the silicon in the composite particles is surface silicon determined by thermogravimetric analysis (TGA). One of the advantages of the present invention is that by providing an optimized particulate porous framework, it becomes easier to achieve a favorable amount of surface silicon when a silicon precursor is used to deposit silicon within the framework.

[0098] The fact that a significant percentage of hydride-terminated silicon remains detectable in the particulate material even after passivation in air indicates that the composite particles contain internal silicon surfaces inaccessible to air. This suggests that the internal pore spaces of the porous carbon framework are first covered with silicon and then capped, forming internal void spaces with hydride-terminated silicon surfaces facing closed internal void spaces. This indicates that the silicon domains have a characteristic length scale that is much smaller than the pores themselves.

[0099] Because the electrolyte cannot access the internal voids, the silicon surface is protected from SEI formation, minimizing irreversible lithium loss during the initial charge cycle. Further exposure of the electroactive material in subsequent charge-discharge cycles is also significantly prevented, so SEI formation does not become a critical failure mechanism leading to capacity loss. At the same time, this silicon is hydrostatically constrained during lithiation, allowing the voids to be utilized during the expansion induced by lithiation.

[0100] The composite particles are preferably low in rough bulk silicon content, as determined by TGA, in addition to the surface silicon content. Rough bulk silicon is defined as silicon that is oxidized at 800°C or higher, as determined by TGA, and TGA is performed in air at a temperature rise rate of 10°C / min. Therefore, the rough bulk silicon content is determined according to the following formula. Z = 1.875 × [(M f -M 800 ) / M f ] × 100% In the formula, Z is the percentage of unoxidized silicon at 800°C, M 800 M is the mass of the sample at 800°C. f This is the mass of ash when oxidation is complete at 1400°C. In this analysis, it is assumed that the mass increase above 800°C corresponds to the oxidation of silicon to SiO2, and that the total mass at the completion of oxidation is SiO2.

[0101] Silicon that oxidizes above 800°C is undesirable. Preferably, rough bulk silicon is 10% by weight or less, or 8% by weight or less, or 6% by weight or less, or 5% by weight or less, or 4% by weight or less, or 3% by weight or less, or 2% by weight or less, or 1.5% by weight or less, as determined by TGA.

[0102] Preferably, at least 30% by weight of silicon is surface silicon and 10% by weight or less of silicon is rough 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 rough 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 rough 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 rough bulk silicon, both determined by TGA.

[0103] The composite particles are preferably 300 m 2 / g or less, or 250m 2 / g or less, or 200m 2 / g or less, or 150m 2 It has a BET surface area of ​​100m² or less. More preferably, 100m². 2 / g or less, or 80m 2 / g or less, or 60m 2 / g or less, or 40m 2 / g or less, or 30m 2 / g or less, or 25m 2 / g or less, or 20m 2 / g or less, or 15m 2 / g or less, or 10m 2 / g or less, or 5m 2 It is less than or equal to / g. Generally, a low BET surface area is preferable to minimize the formation of a solid electrolyte interface (SEI) layer on the surface of the composite particles during the first charge-discharge cycle of the anode. However, if the BET surface area is too low, the majority of the electroactive material cannot access the metal ions in the surrounding electrolyte, resulting in unacceptably low charging speed and capacity. The BET surface area is preferably at least 0.1 m². 2 / g, or at least 1m 2 / g, or at least 2m 2 / g, or at least 5m 2The value is / g. For example, the BET surface area of ​​composite particles is 0.1 to 100 m². 2 / g, or 0.1-80m 2 / g, or 0.5-60m 2 / g, or 0.5-40m 2 / g, or 1-30m 2 / g, or 1-25m 2 / g, or 2-20m 2 It could be in the range of / g.

[0104] The particle size distribution of the optimized particulate porous framework is assumed to remain unchanged by the process of forming composite particles (e.g., step (c)). Therefore, the particle size distribution parameters defined for the optimized particulate porous framework can also be used to define composite particles (e.g., D 50 (Sphericity, etc.)

[0105] Unless otherwise instructed, the pore structure of the composite particles (pore volume, PD) n Pore ​​size (and other parameters) is defined by measuring the pore structure of the optimized particulate porous framework in isolation, i.e., in the absence of electroactive material (or other material) occupying the pores of the particulate porous framework. Therefore, the pore structure parameters defined for the optimized particulate porous framework can also be used to define composite particles.

[0106] When the optimized particulate porous framework is an optimized particulate porous carbon framework, the composite particles have a relative intensity ratio of D peak to G peak of 2.0 or less or 1.8 or less when measured by Raman spectroscopy (I D / I G ) may have. Alternatively, or additionally, composite particles I D / I G This can be 1 or greater or 1.05 or greater. For example, the I of a composite particle. D / I G This can be in the range of 1.0 to 1.6.

[0107] This process may include, after step (c), an annealing step in which the composite particles are annealed at a high temperature under an inert or reducing atmosphere.

[0108] The annealing step involves several interrelated thermal induction processes that stabilize the silicon and extend the cycle life of the composite particles in the LIB. These processes include the removal of hydrogen from terminal Si-H bonds, volume contraction of Si domains resulting in the reopening of some pore spaces, and the promotion of covalent bonding between silicon and the inner surface of the particulate porous framework (e.g., Si-C bonds when a particulate porous carbon framework is used).

[0109] For example, the temperature of the annealing step 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 of the annealing step is 900°C or lower, 850°C or lower, 800°C or lower, 750°C or lower, 700°C or lower, 680°C or lower, 660°C or lower, or 650°C or lower.

[0110] The temperature of the annealing step may be in the range of 200°C to 1000°C, 400°C to 900°C, 500°C to 900°C, or 600°C to 900°C. The temperature of the annealing step 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.

[0111] The temperature in the annealing step may be higher than the temperature in step (c). Preferably, the temperature in the annealing step is 20°C or more, or 40°C or more, or 60°C or more, or 80°C or more, or 100°C or more, or 120°C or more, or 140°C or more, or 150°C or more, than the temperature in step (c).

[0112] The duration of the annealing step 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 duration of the annealing step 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.

[0113] The duration of the annealing step may range from 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.

[0114] The annealing step is carried out under an inert or reducing atmosphere. Preferably, the atmosphere is selected from a nitrogen atmosphere, a hydrogen-containing atmosphere, a noble gas atmosphere, or a mixture thereof.

[0115] Preferably, the annealing step is carried out at a temperature range of 400°C to 900°C for 1 minute to 72 hours, or at a temperature range of 500°C to 900°C for 30 minutes to 4 hours, or at a temperature range of 600°C to 900°C for 1 hour to 4 hours.

[0116] The ratio of the BET surface area of ​​the particles formed after the annealing step to the BET surface area of ​​the composite particles 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.

[0117] The ratio of the BET surface area of ​​the particles formed after the annealing step to the BET surface area of ​​the composite particles may be 15:1 or less, 14:1 or less, 13:1 or less, or 12:1 or less.

[0118] The ratio of the total pore volume of micropores and mesopores measured by gas adsorption of particles formed after the annealing step to the total pore volume of micropores and mesopores measured by gas adsorption of composite particles 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.

[0119] The ratio of the total pore volume of micropores and mesopores measured by gas adsorption of particles formed after the annealing step to the total pore volume of micropores and mesopores measured by gas adsorption of composite particles 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.

[0120] The ratio of the total hydrogen content of the particles formed after the annealing step to the total hydrogen content of the composite particles may be 0.8:1 or less, 0.7:1 or less, 0.6:1 or less, or 0.5:1 or less.

[0121] The ratio of the total hydrogen content of the particles formed after the annealing step to the total hydrogen content of the composite particles may be at least 0.1:1, or at least 0.2:1, or at least 0.3:1.

[0122] This process may include a passivation step after step (c), in which the composite particles are brought into contact with a passivating agent.

[0123] As defined herein, a passivator is a compound or mixture of compounds that can react with the silicon surface deposited in step (c) to form a modified surface. In particular, a passivator as defined herein is a material that can react with the silicon surface to further reduce its surface energy.

[0124] Preferably, the passivation step is performed after the annealing step. As described above, one of the effects of the annealing step is to reopen the pore space that was previously blocked or covered by the silicon nanostructure, allowing the passivation gas to access the pore space and enabling more extensive passivation of the silicon surface and removal of the hydrogen-terminated silicon surface.

[0125] One type of passivation layer is the native oxide layer. The native oxide layer can be formed, for example, by exposing the silicon surface to a passivating agent selected from air or other oxygen-containing gases. The passivation layer may contain silicon oxide of the formula SiO x where 0 < x ≦ 2. The silicon oxide is preferably amorphous silicon oxide. Since the formation of the native oxide layer is exothermic, careful process control is required to prevent overheating or combustion of the particulate material. When the passivating agent is an oxygen-containing gas, the passivation step may include cooling the composite particles to a temperature below 300 °C, preferably below 200 °C, optionally below 100 °C, before contacting the composite particles with the oxygen-containing gas.

[0126] 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 other nitrogen-containing molecules. The passivation layer may contain 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 of 200 to 700 °C, preferably 400 to 700 °C, more preferably 400 to 600 °C. Next, the temperature can be raised to the range of 500 to 1,000 °C as needed 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. A nitride with a substoichiometric ratio (SiN xFor example, in the formula, since 0 < x ≦ 4 / 3) is conductive, the nitride passivation layer can function as a conductive network that enables faster charging and discharging of the electroactive material. Phosphine, as a phosphorus analogue of ammonia, can also be used as a passivating agent. Another type of passivation layer is, for example, a oxynitride layer formed by exposing the silicon surface to a passivating agent containing ammonia (or other nitrogen-containing molecules) 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.

[0127] 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 can be formed by contacting the silicon surface with a passivating agent selected from carbon-containing precursors such as methane or ethylene, for example, at a high temperature in the range of 250 - 700 °C. At low temperatures, a covalent bond is formed between the silicon surface and the carbon-containing precursor, and it is converted to a single layer of crystalline silicon carbide as the temperature rises. The chemical formula of silicon carbide is SiC x where 0 < x ≦ 1.

[0128] Other suitable passivating agents include alkenes, alkynes or carbonyl functional groups, more preferably compounds containing terminal alkenes, terminal alkynes, aldehyde or ketone groups. Preferred passivating agents include one or more compounds of the following formulas, (i) R 1 -CH=CH-R 1 、 (ii) R 1 -C≡C-R 1 、and (iii) O=CR 1 R 1 、 where each R 1can 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 within the ring.

[0129] Particularly preferred passivators include one or more compounds of the following formula: (i) CH2 = CH-R 1 , and (ii) HC≡CR 1 , In the formula, R 1 This is as defined above. Preferably, R 1 It has not been replaced.

[0130] Examples of 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]octo-2-ene. Optionally, mixtures of different passivators may also be used.

[0131] Passivating agents containing alkenes, alkynes, or carbonyl groups are thought to undergo insertion reactions with Si-H groups on the silicon surface, forming a covalently passivated surface that is resistant to oxidation by air. 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]

[0132] Other suitable passivators include compounds containing active hydrogen atoms bonded to oxygen, nitrogen, sulfur, or phosphorus. For example, passivators may be alcohols, amines, thiols, or phosphines. It is understood that the reaction between the hydride groups on the silicon surface and the -XH groups results in the elimination of H2, forming a direct bond between X and the silicon surface.

[0133] Suitable passivators in this category include compounds of the following formula: (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 These are defined independently as above, and 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 elements combine to form an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms within the ring.

[0134] Preferably, X represents O or NH.

[0135] Preferably, R 2 Amine represents an optionally substituted aliphatic or aromatic group having 2 to 10 carbon atoms. Amine groups can also be incorporated into 4 to 10-membered aliphatic or aromatic ring structures such as pyrrolidine, pyrrole, imidazole, piperazine, indole, and purine.

[0136] Contact between the composite particles and the passivator is carried out in a temperature range of 25 to 500°C, preferably in a temperature range of 50 to 450°C, and more preferably in a temperature range of 100 to 400°C.

[0137] This process may include a deposition step after step (c) in which a lithium-ion permeable material is deposited inside and / or on the outer surface of the composite particles. The use of lithium-ion fillers reduces the surface area of ​​the composite particles, preventing contact between the electrolyte inside the particles and the silicon domains, thereby reducing SEI formation.

[0138] Preferably, the lithium-ion permeable material is a pyrolysis carbon material, and the deposition step includes combining composite particles with a pyrolysis carbon precursor and heating the pyrolysis carbon precursor to a temperature effective for depositing the conductive pyrolysis carbon material in and / or on the outer surface of the composite particles. If the process includes an annealing step, the deposition step may optionally be performed before or after the annealing step. If a passivation step is performed, most preferably, the deposition step is performed after the passivation step.

[0139] The pyrolysis 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 such as dihydroxynaphthalene, anthracene, tetracene, pentacene, fluorene, acenaphthene, phenanthrene, fluoranthrene, pyrene, chrysene, perylene, coronene, fluorenone, anthraquinone, anthrone, and their alkyl-substituted derivatives. Suitable pyrolysis carbon precursors also include bicyclic monoterpenoids, and optionally, bicyclic monoterpenoids are selected from camphor, borneol, eucalyptol, camphene, carene, sabinene, thujene, and pinene. Furthermore, suitable pyrolysis carbon precursors include C2-C10 hydrocarbons, 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 pyrolysis 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.

[0140] The suitable temperature for depositing pyrolysis carbon material in the deposit step is in the range of 300-800°C or 400-700°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 depends on the type of carbon precursor used. Preferably, the temperature is 300°C or higher, or 350°C or higher, or 400°C or higher, or 450°C or higher, or 500°C or higher.

[0141] The carbon-containing precursor used in the deposition step can be used in pure form or as a diluted mixture with an inert carrier gas such as nitrogen or argon. For example, the carbon-containing precursor may be used in amounts ranging from 0.1 to 100 vol% or 0.5 to 20 vol% or 1 to 10 vol% or 1 to 5 vol% based on the total volume of the precursor and the inert carrier gas.

[0142] When depositing pyrolysis carbon materials, the same compound can function as both a passivator in the passivation step and a pyrolysis carbon precursor in the deposition step. For example, if styrene is selected as the pyrolysis carbon precursor, styrene will also function as a passivator unless the composite particles are exposed to another passivator before contacting styrene. In this case, the passivation and deposition of the conductive carbon material can be carried out stepwise, simultaneously, for example, in a temperature range of 300–700°C. Alternatively, the passivation and deposition of the conductive carbon material can be carried out sequentially using the same material as the passivator and pyrolysis carbon precursor, but the deposition step is carried out after the passivation step, at a higher temperature than the passivation step. For example, passivation may be carried out at a temperature of 25°C to less than 300°C, and the deposition of pyrolysis carbon may be carried out at a temperature of 300–700°C. These two steps can be carried out sequentially and appropriately by increasing the temperature while maintaining contact with the compound that functions as both the passivator and the pyrolysis carbon precursor. At lower temperatures (e.g., in the range of 25°C to less than 300°C), passivation becomes the main process. As the temperature rises (e.g., 300°C to 700°C), pyrolysis carbon deposition occurs.

[0143] The composite particles may be incorporated into a composition comprising at least one other component. In particular, a composition is provided comprising the composite particles and at least one other component selected from (i) a binder, (ii) a conductive additive, and (iii) an additional particulate electroactive material. This composition is useful as an electrode composition and can therefore be used to form the active layer of an electrode.

[0144] 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.

[0145] In the case of a hybrid electrode composition, the composition preferably contains 3 to 60% by weight, or 3 to 50% by weight, or 5 to 50% by weight, or 10 to 50% by weight, or 15 to 50% by weight, of the total dry weight of the composition, of composite particles. At least one additional particulate electroactive material is appropriately present in an amount of 20 to 95% by weight, or 25 to 90% by weight, or 30 to 75% by weight, of the total dry weight of the composition.

[0146] At least one additional particulate electroactive material is preferably 10-50 μm, preferably 10-40 μm, more preferably 10-30 μm, most preferably 10-25 μm, for example, in the range of 15-25 μm. 50 It has a particle size.

[0147] 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.

[0148] D of at least one additional particulate electroactive material 90 The particle size is preferably 100 μm or less, more preferably 80 μm or less, more preferably 60 μm or less, more preferably 50 μm or less, and most preferably 40 μm or less.

[0149] At least one additional particulate electroactive material is preferably selected from carbon-containing particles, graphite particles and / or hard carbon particles, the graphite and hard carbon particles being in the range of 10 to 50 μm. 50 The particles have a particle size. More preferably, at least one additional particulate electroactive material is selected from graphite particles, and the graphite particles are in the range of 10 to 50 μm. 50 It has a particle size.

[0150] The composition may also be a non-hybrid (or “high-load”) 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, based on the total dry weight of the composition, the composition contains less than 15% by weight, preferably less than 10% by weight, preferably less than 5% by weight, preferably less than 2% by weight, more preferably less than 1% by weight, and more preferably less than 0.5% by weight of additional electroactive material (i.e., additional material that can insert and release metal ions during charging and discharging of the battery).

[0151] This type of "high-load" electrode composition preferably contains at least 50% by weight, or at least 60% by weight, or at least 70% by weight, or at least 80% by weight, or at least 90% by weight of composite particles, based on the total dry weight of the composition.

[0152] The composition may optionally contain a binder. The binder has the function of adhering the composition to the current collector and maintaining the integrity of the composition. Examples of binders 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 contains a polymer selected from polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0153] The binder may be present in an amount of 0.5 to 20% by weight, preferably 1 to 15% by weight, preferably 2 to 10% by weight, and most preferably 5 to 10% by weight, based on the total dry weight of the composition.

[0154] The binder may optionally be present in combination with one or more additives that modify the properties of the binder, such as crosslinking promoters, coupling agents, and / or adhesion promoters.

[0155] The composition may optionally contain one or more conductive additives. Preferred conductive additives are non-electroactive materials included to improve electrical conductivity between the electroactive components of the composition and between the electroactive components of the composition and the current collector. Conductive additives may be selected from carbon black, carbon fibers, carbon nanotubes, graphene, acetylene black, Ketjenblack, metal fibers, metal powders, and conductive metal oxides. Preferred conductive additives include carbon black and carbon nanotubes.

[0156] One or more conductive additives may be present in a total amount of 0.5 to 20% by weight, preferably 1 to 15% by weight, preferably 2 to 10% by weight, and most preferably 5 to 10% by weight, based on the total dry weight of the composition.

[0157] The present invention also provides an electrode comprising composite particles and a current collector, wherein the composite particles are in electrical contact with the current collector. The particulate material used to prepare the electrode may be in the form of a composition comprising composite particles and at least one other component as defined above.

[0158] As used herein, the term current collector refers to a conductive substrate that can conduct electric current with respect to 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 are typically in the form of foil or mesh having a thickness of 3 to 500 μm. Composite particles can be coated on one or both sides of the current collector, preferably with a thickness ranging from 10 μm to 1 mm, for example, 20 to 500 μm, or 50 to 200 μm.

[0159] The electrodes may be manufactured by combining composite particles with a solvent and optionally one or more viscosity-modifying additives to form a slurry. The slurry is then cast onto the surface of a current collector, the solvent is removed, and thereby an electrode layer is formed on the surface of the current collector. If necessary, further steps such as heat treatment and / or calendering of the electrode layer to cure any binder may be performed. The electrode layer 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.

[0160] Alternatively, the slurry may 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 casting template, removing the solvent, and then removing the casting template. The resulting film or mat is cohesive and in the form of self-supporting clumps, which can then be bonded to a current collector by known methods.

[0161] The electrode can be used as the anode of a metal-ion battery. Therefore, the present invention provides a rechargeable metal-ion battery that includes the electrode as the anode. Lithium ions are preferred as the metal ions. More preferably, the rechargeable metal-ion battery is a lithium-ion battery.

[0162] The cathode of a rechargeable metal-ion battery typically includes 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 material. Examples of suitable cathode active materials include LiCoO2, LiCo 0.99 Al 0.01 O2, LiNiO2, LiMnO2, LiCo 0.5 Ni 0.5 O2, LiCo 0.7 Ni 0.3 O2, LiCo 0.8 Ni 0.2 O2, LiCo 0.82 Ni 0.18 O2, LiCo 0.8 Ni0.15 Al 0.05 O2, Lithium 0.4 Co 0.3 Mn 0.3 O2 and LiNi 0.33 Co 0.33 Mn 0.34 It contains O2. The thickness of the cathode current collector is typically 3 to 500 μm. Examples of materials that can be used as cathode current collectors include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0163] Suitable electrolytes for rechargeable metal-ion batteries include non-aqueous electrolytes containing lithium salts, and may include, but are not limited to, non-aqueous electrolytes, organic solid electrolytes, and inorganic solid electrolytes. Examples of usable non-aqueous electrolytes include aprotic organic solvents, such as 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, methylformate, methyl acetate, triester phosphate, trimethoxymethane, sulfolane, methylsulfolane, and 1,3-dimethyl-2-imidazolidinone.

[0164] 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.

[0165] Examples of inorganic solid electrolytes include nitrides, halides, and sulfides of lithium salts, such as Li5NI2, Li3N, LiI, LiSiO4, Li2SiS3, Li4SiO4, LiOH, and Li3PO4.

[0166] The lithium salt dissolves appropriately in the selected solvent or mixture of solvents. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO4, LiBF4, LiBC4O8, LiPF6, LiCF3SO3, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, and CF3SO3Li.

[0167] <​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Silicon-carbon composite particles were prepared by arranging approximately 1.8 g of particulate porous framework having the properties described in Tables 1 and 2 on a stainless steel plate with a constant thickness of 1 mm along its length. The plate was then placed inside a 60 mm outer diameter stainless steel tube equipped with gas inlet and outlet lines located in the high-temperature region of a retort furnace. The furnace tube was purged with nitrogen gas at room temperature for 30 minutes, and then the sample temperature was raised to 450-475°C. The nitrogen gas flow rate was adjusted so that the gas residence time in the furnace tube was at least 10 seconds, and this flow rate was maintained for 30 minutes. Next, the gas supply was switched from nitrogen to a mixture of silane (SiH4) in nitrogen at a concentration of 1.25 vol%. The silane dosing was carried out over a maximum of 5 hours while maintaining the reactor pressure at 101.3 kPa (1 atm). After dosing was completed, the gas flow rate was kept constant while the silane was purged from the furnace using nitrogen. The furnace is purged under a nitrogen atmosphere for 30 minutes, and then cooled to room temperature over several hours. Next, the atmosphere is gradually switched to air over two hours by switching the gas flow from nitrogen to air from the compressed air supply.

[0171] The surface silicon of the composite particles was measured as follows: A 10 mg (±2 mg) test sample was placed in a 70 μL crucible. The sample was placed in a Mettler-Toledo TGA / DSC 3+ apparatus while Ar purging gas, N2 padding gas, and air reaction gas flowed at 100 mL / min. The TGA furnace chamber was heated from 25°C to 1400°C at a rate of 10°C / min. Data were collected at 1-second intervals. Figure 1 shows the TGA plots obtained by this method for composite particles prepared from C15 and C16. The formula defined above is used to calculate the surface silicon (Y) value.

[0172] A series of composite particle samples were prepared using each carbon skeleton. The average surface silicon was calculated from the TGA curve for each sample and is shown in Table 2. It can be seen that the average surface silicon increases for carbon skeletons with a pore structure optimized for the silicon precursor (SiH4). In particular, Figures 2-4 show the average surface silicon of composite particles prepared from each porous carbon skeleton plotted against pore structure parameters measured for the skeleton before silicon deposition. The pore structure parameters are expressed relative to the effective size of SiH4. The circular data points are for skeletons with a pore structure optimized for SiH4 (C1-C4, C8, C12-C15). The intersecting data points are for skeletons without a pore structure optimized for SiH4 (C5-C7, C9-C11, C16). It can be seen that composite particles prepared from skeletons with an optimized pore structure consistently have higher average surface silicon compared to composite particles prepared from skeletons without an optimized pore structure. The inventors previously demonstrated that a higher surface silicon level improves reversible capacity retention across multiple charge / discharge cycles. Therefore, a framework with a pore structure optimized for a silicon precursor (SiH4 in this example) allows for the formation of composite particles with advantageous properties for use as an anode electroactive material in LIBs, when silicon is deposited within the framework using the silicon precursor. This effect is expected to be achieved with a carbon framework having a pore structure optimized for an alternative silicon precursor.

[0173] Example 2 Preparation and characterization of composite particles The particulate porous carbon skeletons C17-C21 used in this example have the properties shown in Tables 3 and 4. The composite particles produced from these skeletons have the properties shown in Table 5. [Table 4] [Table 5] [Table 6]

[0174] Before depositing silicon, the particle size, surface area, and pore structure parameters of the carbon skeleton were measured.

[0175] Silicon-carbon composite particles were prepared using a 0.6 L pressure reactor system according to the following procedure. First, 25 g of particulate porous skeletons having the properties described in Tables 3 and 4 were weighed and placed in the reactor chamber, then sealed, inactivated, and pressure tested using nitrogen gas. Next, the reactor was heated to a temperature of 320-350°C with stirring at 200 rpm. Then, silane gas was injected, and the furnace set temperature was raised to 550°C. A total of 27 g of silane was injected in four pulses so that the pressure setpoint for each cycle was 9-12 bar. Completion of the reaction in each pulse was determined by pressure monitoring, and completion of the conversion of silane to silicon on carbon was determined by pressure stabilization. After the silane injection, the reactor was deactivated again using nitrogen gas. Then, passivation was carried out for 60 cycles, with the air concentration in nitrogen at 150°C increasing, until the temperature and pressure stabilized in 100% air with each injection. These steps cause a passivation layer of silicon dioxide to grow on the outer surface of the composite particles. The resulting composite powder is recycled by breaking the reactor seal and passing the regenerated composite powder through a 53 μm sieve.

[0176] The amount of silicon in the composite particles was determined using TGA. The mass of the composite particle samples was measured in air at approximately 1400°C using a TGA instrument until oxidation was complete. The composite particles are assumed to be composed only of carbon, silicon, and oxygen. The mass at the completion of oxidation is assumed to be only SiO2, from which the silicon content of the initial composite particles can be determined. The silicon content determined by TGA for composite particles prepared from each of C17 to C21 indicates that sufficient silicon has been deposited for the composite particles to be used as an anode material for lithium-ion batteries.

[0177] The surface silicon of the composite particles was measured as follows. 10 mg (±2 mg) of the test sample was placed in a 70 μL crucible. The sample was placed in a Mettler Toledo TGA / DSC 3+ apparatus while flowing Ar purge gas, N2 padding gas, and air reaction gas at 100 mL / min. The TGA furnace chamber was heated from 25 °C to 1400 °C at a rate of 10 °C / min. Data was collected at 1-second intervals. The formula defined above was used to calculate the surface silicon (Y) value.

[0178] Figures 5 to 7 show the surface silicon of the composite particles prepared from each porous carbon skeleton plotted against the pore structure parameters measured for the skeleton before silicon deposition. The pore structure parameters are expressed based on the effective size of SiH4. The circular data points are for skeletons with a pore structure optimized for SiH4 (C17 - C20). The crossed data points are for skeletons without a pore structure optimized for SiH4 (C21). The composite particles prepared from skeletons with an optimized pore structure consistently have a higher surface silicon compared to the composite particles prepared from skeletons without an optimized pore structure.

[0179] Example 3 Preparation and characterization of composite particles The particulate porous carbon skeletons C22 - C28 used in this example have the characteristics shown in Tables 6 and 7. The composite particles prepared from these skeletons have the characteristics shown in Table 8. [Table 7] [Table 8] [Table 9]

[0180] Before depositing silicon, the particle size, surface area, and pore structure parameters of the carbon skeleton were measured.

[0181] Silicon-carbon composite particles were prepared and characterized using the same procedure as in Example 2.

[0182] Figures 8-10 show the surface silicon of composite particles prepared from each porous carbon framework plotted against pore structure parameters measured for the framework before silicon deposition. The pore structure parameters are expressed relative to the effective size of SiH4. The circular data points are for frameworks with a pore structure optimized for SiH4 (C22-C26). The intersecting data points are for frameworks without a pore structure optimized for SiH4 (C27 and C28). Composite particles prepared from frameworks with an optimized pore structure consistently have higher surface silicon compared to composite particles prepared from frameworks without an optimized pore structure.

Claims

1. It is a process, (a) A step of determining the effective size σ of the silicon precursor, (b) Providing a collection of optimized particulate porous frameworks comprising micropores and / or mesopores, and having a pore structure optimized for the silicon precursor, wherein the optimized pore structure is 1. PD between 1.4σ and 3.0σ ３０ Pore ​​diameter and PD of 5.0σ to 14.0σ ９０ Pore ​​diameter and 4.0σ to 12.0σ pore size span (PD) ９０ ~PD １０ ) and, "Effective size σ" refers to the value of σ in the Lennard Jones potential of the silicon precursor, "PD ｎ "Pore diameter" refers to a pore diameter less than n% of the total volume of micropores and mesopores. The process referred to above.

2. Step (b) is, (b1) Providing a collection of one or more particulate porous frameworks including micropores and / or mesopores, (b2) A step of measuring the pore structure of each group, (b3) A step of accepting each group having the optimized pore structure and not accepting each group not having the optimized pore structure, (b4) The process according to claim 1, further comprising using one or more of the accepted groups as the group of optimized particulate porous frameworks, or, if no group is accepted, repeating steps (b1), (b2), and (b3) for further groups of particulate porous frameworks including micropores and / or mesopores until a group is accepted.

3. The process according to claim 2, wherein step (b1) provides at least two groups, of which at least one is optionally rejected in step (b3).

4. (a1) The step of providing one or more silicon precursors, (a2) A step of determining the effective size σ of each silicon precursor, (b5) The step of providing a collection of particulate porous frameworks including micropores and / or mesopores, (b6) A step of measuring the pore structure of the group, (a3) A step of accepting each silicon precursor having an effective size such that the pore structure becomes the optimized pore structure with respect to the silicon precursor, and not accepting each silicon precursor having an effective size such that the pore structure does not become the optimized pore structure with respect to the silicon precursor, (a4) If a silicon precursor is not accepted, the process according to claim 1, further comprising the step of repeating steps (a1), (a2), and (a3) ​​with further silicon precursors until a silicon precursor is accepted.

5. The process according to claim 4, wherein step (a1) provides at least two silicon precursors, and optionally at least one of them is not accepted in step (a3).

6. The process according to any of the prior claims, comprising providing a kit comprising the silicon precursor and the optimized particulate porous skeleton.

7. The process according to any of the prior claims, further comprising providing a further population of the optimized particulate porous skeleton on an industrial scale, wherein industrial scale optionally means at least 100 kg or at least 1,000 kg.

8. The optimized pore structure has a PD of 6.0σ to 13.5σ or 8.5σ to 13.0σ. ９０ A process according to any of the prior claims, having a pore size.

9. The optimized pore structure has a pore diameter span (PD) of 4.5σ to 11.5σ or 6.0σ to 11.0σ. ９０ ~PD １０ The process described in any of the prior claims, including ).

10. The optimized pore structure has a PD of 1.6σ to 3.0σ, or 1.7σ to 2.8σ, or 1.8σ to 2.2σ ３０ The process according to any of the preceding claims, including a pore diameter.

11. The optimized pore structure has a PD of less than 4.0σ or less than 3.7σ. ５０ A process according to any of the prior claims, including pore size.

12. The optimized pore structure has a PD of 3.75σ to 8.0σ or 5.0σ to 7.0σ. ７５ A process according to any of the prior claims, including pore size.

13. The process according to any of the prior claims, wherein the particulate porous skeleton is a particulate porous carbon skeleton.

14. The optimized particulate porous carbon skeleton, when measured by Raman spectroscopy, has a relative intensity ratio of D peak to G peak (I Ｄ / I Ｇ )but, 2.0 or less, or 1.8 or less, and / or 1 or more, or 1.05 or more, and / or The process according to claim 13, wherein the value is 1.0 to 1.

6.

15. The process according to claim 13 or 14, comprising chemically or physically activating a carbonaceous material to provide the particulate porous carbon skeleton containing micropores and / or mesopores.

16. The aforementioned physical activation involves activating the carbonaceous material with oxygen, water vapor, CO, and CO ２ The process according to claim 15, comprising heating at a temperature of 600 to 1200°C or 600 to 1000°C in one or more of the flows.

17. The chemical activation includes impregnating the carbonaceous material with a chemical activator to form an impregnated carbonaceous material, and heating the impregnated carbonaceous material at a temperature of 250 to 1000°C or 500 to 950°C, which can be selected as follows: The chemical activator can be optionally selected from NaOH, KOH, and K ２ CO ３ H ３ PO ４ CaCl ２ ZnCl ２ The process according to claim 15, selected from, and mixtures thereof.

18. The process according to any one of claims 15 to 17, wherein the carbonaceous material is pyrolytic carbon, and optionally pyrolytic carbon derived from a plant source, or pyrolytic pitch, or pyrolytic polymer.

19. Providing the particulate porous carbon skeleton involves providing a carbonaceous material from a plant source, thermally decomposing the carbonaceous material by heating it in an inert atmosphere at a temperature of optionally 400 to 900°C, and then dissolving the thermally decomposed material in a temperature range of 300 to 1500°C, or 600 to 1200°C, or 600 to 1000°C in the presence of oxygen, water vapor, CO, and CO ２ The process according to claim 13 or 14, comprising bringing into contact with one or more of the following.

20. In step (a), the silicon precursor is a gaseous silicon precursor, and optionally, the gaseous silicon precursor is a silane (SiH ４ ), disilane (Si ２ H ６ ), trisilane (Si ３ H ８ ), tetrasilane (Si ４ H １０ ), pentasilane (Si ５ H １２ ), hexasilane (Si ６ H １４ ), methylsilane (CH ３ SiH ３ ), dimethylsilane ((CH ３ ) ２ SiH ２ ), trimethylsilane ((CH ３ ) ３ SiH), tetramethylsilane ((CH ３ ) ４ Si), and chlorosilanes, such as trichlorosilane (HSiCl ３ ) or dichlorosilane (H ２ SiCl ２ ) or chlorosilane (H ３ SiCl), or methylchlorosilane, for example, methyltrichlorosilane (CH ３ SiCl ３ ) or dimethyldichlorosilane ((CH ３ ) ２ SiCl ２ A process according to any of the prior claims, selected from ).

21. The process according to any of the prior claims, wherein the effective size σ is a value in the range of 0.4 to 0.6 nm.

22. The silicon precursor in step (a) is Silane (SiH) with an effective size σ of 0.408 nm ４ ),or Disilane (Si) with an effective size σ of 0.483 nm ２ H ６ ),or Trisilane (Si) with an effective size σ of 0.556 nm ３ H ８ ),or Trichlorosilane (HSiCl) with an effective size σ of 0.564 nm ３ ),or Dichlorosilane (H) with an effective size σ of 0.503 nm ２ SiCl ２ ),or Chlorosilane (H) with an effective size σ of 0.415 nm ３ A process according to any of the prior claims, wherein the material is SiCl.

23. The silicon precursor in step (a) is a silane (SiH) with an effective size σ of 0.408 nm. ４ The process according to any one of claims 1 to 21, wherein the process is as follows:

24. The silicon precursor in step (a) is a disilane (Si) with an effective size σ of 0.483 nm. ２ H ６ The process according to any one of claims 1 to 21, wherein the process is as follows:

25. The silicon precursor in step (a) is HSiCl with an effective size σ of 0.564 nm. ３ The process according to any one of claims 1 to 21.

26. The silicon precursor is silane (SiH ４ ) Rather, the silicone precursor may be optionally silane (SiH ４ ) or disilane (Si ２ H ６ The process described in any one of claims 1 to 21, which is not the process described in claim 1 to 21.

27. The process according to any of the prior claims, wherein the optimized pore structure further comprises a micropore volume fraction of at least 0.4 and / or 0.95 or less, based on the total volume of micropores and mesopores.

28. The optimized pore structure, when measured by gas adsorption, has a total volume P of micropores and mesopores. １ cm ３ / g further includes, in the formula, P １ The process according to any of the prior claims, wherein is 0.4 to 1.8, or 0.5 to 1.6, or 0.6 to 1.

1.

29. The optimized pore structure has a total volume P of pores having a diameter in the range of over 50 to 100 nm. ２ cm ３ / g further contains, P ２ is 0.2 × P １ Less than, or 0.05 × P １ Less than, or 0.005 × P １ The process according to claim 28, wherein the process is less than [amount missing].

30. The optimized pore structure has a minimum of 0.3 cm ３ / g, or at least 0.4cm ３ / g, or at least 0.5cm ３ / g, or at least 0.6cm ３ The process according to any of the prior claims, further comprising a micropore volume of / g.

31. The process according to any of the prior claims, further comprising the optimized pore structure being such that the total volume of pores having a diameter in the range of 50 to 100 nm is less than 10%, less than 5%, or less than 1% of the total volume of micropores, mesopores, and pores having a diameter in the range of 50 to 100 nm.

32. The process according to any of the prior claims, wherein the optimized pore structure further comprises a bimodal or multimodal pore size distribution.

33. The pore size distribution is, (i) 1.2σ to 1.7σ, (ii) 1.8σ to 2.1σ, and The process according to claim 32, wherein the peaks are in at least two, and optionally all three, of the regions (i), (ii), and (iii) between 2.2σ and 3.2σ.

34. The process according to claim 33, wherein peaks (i), (ii), and (iii) include at least two of the strongest peaks in the pore size distribution, and optionally include three of the strongest peaks.

35. The optimized particulate porous framework has a length of at least 750 m ２ / g, or at least 1,000m ２ / g, or 1,200-3,000m ２ A process according to any of the prior claims, having a BET surface area of ​​1 / g.

36. The optimized particulate porous framework has a diameter of less than 100 μm, or less than 30 μm, or 1 to 30 μm, or 1 to 20 μm, or 2 to 8 μm. ５０ A process according to any of the prior claims, having a particle size.

37. (c) The process according to any prior claim, further comprising the step of contacting the optimized particulate porous framework provided in step (b) with the silicon precursor of step (a) at a temperature effective for depositing elemental silicon in the pores of the optimized particulate porous framework, thereby providing composite particles.

38. (d) The process according to claim 37, further comprising the step of forming an electrode containing the composite particles.

39. (e) The process according to claim 38, further comprising the step of forming a rechargeable metal-ion battery including the electrodes.

40. An optimized particulate porous framework comprising micropores and / or mesopores, having a pore structure optimized for the silicon precursor, wherein the effective size of the silicon precursor is σ, and the optimized pore structure is 1. PD between 1.4σ and 3.0σ ３０ Pore ​​diameter and PD of 5.0σ to 14.0σ ９０ Pore ​​diameter and 4.0σ to 12.0σ pore size span (PD) ９０ ~PD １０ ) and, "Effective size σ" refers to the value of σ in the Lennard Jones potential of the silicon precursor, "PD ｎ The "pore diameter" refers to a pore diameter less than n% of the total volume of micropores and mesopores in the process described above.

41. A kit comprising the optimized particulate porous framework described in claim 40 and the silicon precursor having the optimized pore structure.

42. A composite particle for use as an electroactive material in a metal ion battery, wherein the composite particle is (i) An optimized particulate porous framework comprising micropores and / or mesopores, having a pore structure optimized for the silicon precursor, wherein the effective size of the silicon precursor is σ, and the optimized pore structure is PD of 1.4σ to 3.0σ ３０ pore size, and PD of 5.0σ to 14.0σ ９０ Pore ​​diameter and 4.0σ to 12.0σ pore size span (PD) ９０ ~PD １０ ) and, "Effective size σ" refers to the value of σ in the Lennard Jones potential of the silicon precursor, "PD ｎ "Pore diameter" refers to a pore diameter less than n% of the total volume of micropores and mesopores, in the optimized particulate porous framework, (ii) The composite particle comprising a plurality of elemental silicon domains located within the pores of the optimized particulate porous framework.

43. The composite particle according to claim 42, wherein, as determined by thermogravimetric analysis (TGA), at least 20% by weight, or at least 22% by weight, or at least 25% by weight, or at least 30% by weight, or at least 35% by weight of the silicon is surface silicon.

44. The composite particle according to any one of claims 42 to 43, wherein, as determined by TGA, 10% by weight or less, or 8% by weight or less, or 6% by weight or less, or 5% by weight or less, 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 the silicon is coarse bulk silicon.

45. A composite particle according to any one of claims 42 to 44, comprising at least 26% by weight, or at least 28% by weight, or at least 30% by weight, or at least 32% by weight of silicon, or at least 34% by weight of silicon, or at least 36% by weight of silicon, or at least 38% by weight of silicon, or at least 40% by weight of silicon, or at least 42% by weight of silicon, or at least 44% by weight of silicon.

46. An electrode comprising composite particles according to any one of claims 42 to 45.

47. A rechargeable metal-ion battery comprising the electrode described in claim 46.

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