Composite particles

Abstract

A composite particle is provided for use as an electroactive material for metal ion batteries, the composite particle comprising a particulate porous framework containing micropores and optionally mesopores, and electroactive material domains located within the pores of the particulate porous framework, where P1 is the total volume of micropores and mesopores in the particulate porous framework, expressed in cm3 / g, and P1 is at least 0.35, and VP07 is the pore volume of pores with a diameter of 0.7 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP07 is in the range of 5.1 to 40%, and P1 and VP07 are measured by nitrogen gas adsorption.

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 electroactive materials for 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 relative to 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 may be 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 function as a backbone for the composite particles. 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, the electroactive materials exhibit good reversible capacity retention over multiple charge-discharge cycles. 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 on the surface of the electroactive material 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 use in preparing composite particles with desirable properties for downstream applications of LIBs. [Overview of the project]

[0006] The present invention provides composite particles for use as electroactive materials in metal-ion batteries, and the composite particles are A particulate porous framework containing micropores and optionally mesopores, It comprises electroactive material domains located within the pores of a particulate porous framework, P1 is cm 3 Expressed in g, this is the total volume of micropores and mesopores in the particulate porous framework, and P1 is at least 0.35. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP07 is in the range of 5.1 to 40%. P1 and VP07 are measured by nitrogen gas adsorption.

[0007] The inventors have discovered that pore diameters of 0.7 nm or less, i.e., pore diameters at the smaller end of the pore diameter distribution, play a crucial role in the suitability of porous particles as a framework for depositing electroactive materials such as silicon. By controlling the pore volume of these small pores, defined by parameter VP07, an optimized pore structure is provided, resulting in composite particles with advantageous properties for use in metal-ion batteries. Electrodes containing the composite particles, rechargeable metal-ion batteries containing the electrodes, and processes for their fabrication are also provided.

[0008] The present invention also provides a process for preparing composite particles, the process comprising (a) providing a particulate porous framework as defined herein, and (b) depositing electroactive material domains in the pores of the particulate porous framework.

[0009] The present invention (a1) Providing a group of one or more particulate porous skeletons including micropores and optionally mesopores, (a2) A step of measuring the pore structure of each group, (a3) A step of accepting each group having an optimized pore structure and not accepting each group not having an optimized pore structure, wherein the optimized pore structure is P1 is cm 3 Expressed in g, this is the total volume of micropores and mesopores in the particulate porous framework, and P1 is at least 0.35. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP07 is in the range of 5.1 to 40%. P1 and VP07 are measured by nitrogen gas adsorption, in the steps of acceptance and non-acceptance. (b) The process also provides a step of depositing electroactive material domains into the pores of an accepted collection of particulate porous frameworks.

[0010] In this process, the understanding provided by the inventors regarding a method for selecting a porous framework having an optimized pore structure is advantageously used to screen multiple sources of frameworks and select one that is expected to impart desirable properties to the composite particles. [Brief explanation of the drawing]

[0011] [Figure 1] The average surface silicon and VP07 values ​​of the composite particles prepared in Example 1 are shown. [Figure 2] The average surface silicon and VP20-VP5 values ​​of the composite particles prepared in Example 1 are shown. [Figure 3] The maximum silicon and VP07 values ​​of the composite particles prepared in Example 1 are shown. [Figure 4] The surface silicon and VP07 values ​​of the composite particles prepared in Example 3 are shown. [Figure 5] The surface silicon and VP20-VP5 values ​​of the composite particles prepared in Example 3 are shown. [Figure 6] The surface silicon and VP07 values ​​of the composite particles prepared in Example 4 are shown. [Figure 7]The surface silicon and VP20-VP5 values ​​of the composite particles prepared in Example 4 are shown. [Modes for carrying out the invention]

[0012] The optimized pore structure was determined by the inventors based on the fact that the deposition of electroactive materials such as silicon in a 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 a silicon precursor to be decomposed into silicon, the precursor must be able to enter the pores of the framework and move to a suitable decomposition site. The desired framework generally includes a three-dimensionally interconnected open pore network containing micropores, optionally mesopores, and optionally a small amount of large pores. According to conventional IUPAC terminology, in this specification, the term "micropore" refers to a pore with a diameter of less than 2 nm, the term "mesopore" refers to a pore with a diameter of 2 to 50 nm, and the term "large pore" refers to a pore with a diameter greater than 50 nm. As used herein, P1 is cm 3 This is the total volume of micropores and mesopores, expressed in units of g. VP07 is the volume of pores with a diameter of 0.7 nm or less, expressed as a percentage of P1. Pores with a diameter of less than 0.7 nm are often referred to as "ultrafine pores" in the literature.

[0013] By limiting VP07 to 5.1–40%, a framework with an optimized pore structure is provided. This optimized pore structure facilitates the production of composite particles with desirable properties for use as electroactive materials. This is surprising because pores with a diameter of 0.7 nm or less, i.e., pores at the smaller end of the pore size distribution, have not previously been considered relevant to the properties of electroactive materials. Since 0.7 nm is less than twice the size of typical silicon precursors (approximately 0.4–0.6 nm) that CVI uses to deposit silicon into particulate porous frameworks, it is expected that most of these small pores will be capped or at least partially unfilled after deposition, and are therefore ignored when selecting porous frameworks. However, the inventors have found advantages in forming part of the framework's pore volume from pores with a diameter of 0.7 nm or less. These pores may remain at least partially unfilled after silicon deposition, and their presence helps improve the elastic response of the composite material under large strains (such as during lithiation and delithiation), minimizing the scale of outward expansion and significantly reducing composite material failure. However, if VP07 is too high, the curvature and constriction of the framework increase along with the BET surface area, making it more difficult to control and deposit the electroactive material in the desired form within the framework.

[0014] VP07 is preferably in the range of 5.5-35%, or 7-30%, or 10-27%, or most preferably 15-25%. It has been found that with a framework in which VP07 is within these ranges, composite particles with a good balance of average surface silicon and silicon content can be prepared, as observed in the examples.

[0015] VP07 is expressed as the total volume of micropores and mesopores within the particulate porous framework. However, in some applications, it is advantageous to specify the minimum absolute volume of pores with a diameter of 0.7 nm or less. Therefore, the volume of pores with a diameter of 0.7 nm or less in the particulate porous framework should be at least 0.05 cm³ when measured by nitrogen adsorption. 3 / g, preferably 0.08-0.5cm 3 / g, most preferably 0.1-0.3cm 3 It could be / g

[0016] Unless otherwise instructed, the pore structure of the composite particles (e.g., P1, VP07, VP1, PD) n Pore ​​diameter, etc., is defined by measuring the pore structure of the particulate porous framework in isolation, i.e., in the absence of electroactive material (or other material) occupying the pores of the particulate porous framework.

[0017] VP1, VP2, and VP5 are the volumes of pores in the particulate porous framework with pore diameters of 1.0 nm or less, 2.0 nm or less, and 5.0 nm or less, respectively, expressed as a percentage of P1. VP1, VP2, and VP5 are measured by nitrogen gas adsorption. Preferably, VP1 is at least 1.5 × VP07, or at least 2 × VP07. Preferably, VP2 is at least 2.5 × VP07, or at least 3 × VP07, or at least 4 × VP07. Preferably, VP5 is at least 55%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 92%, or at least 93%.

[0018] Preferably, VP2 is at least 20%. In some applications, VP2 is at least 40%, at least 50%, at least 55%, or at least 60%, at least 70%, at least 80%, or at least 85%, i.e., micropores form the majority of the volume of micropores and mesopores. Alternatively, VP2 is less than 50%, or 45% or less, or 40% or less, i.e., mesopores form the majority of the volume of micropores and mesopores.

[0019] VP2 may be less than 99%, or less than 98%, or less than 95%, or preferably less than 90%, for example, 40-90%.

[0020] VP2 can be in the range of 45 - 98%, or 45 - 90%, or 45 - 85%, or 45 - 80%, or 45 - 78%, or 45 - 75%, or 45 - 70%, or 45 - 60%, or 50 - 98%, or 50 - 90%, or 50 - 85%, or 50 - 80%, or 50 - 78%, or 50 - 75%, or 50 - 70%, or 55 - 98%, or 55 - 90%, or 55 - 85%, or 55 - 80%, or 55 - 78%, or 55 - 75%, or 55 - 70%, or 55 - 69%.

[0021] The micropore volume is preferably at least 0.3 cm 3 / g. By combining with the desirable value of VP07 identified by the inventors, it has been found that a particulate porous skeleton having a micropore volume of at least 0.3 cm 3 / g provides a pore structure further optimized for the deposition of electroactive materials such as silicon. The micropore volume can be at least 0.4 cm 3 / g, or at least 0.5 cm 3 / g, or at least 0.6 cm 3 / g.

[0022] By controlling the pore volume at larger pore sizes, the properties of the skeleton and the resulting composite particles can be further improved. VP20 and VP10 are defined as the volume of pores with pore diameters of 20.0 nm or less or 10.0 nm or less in the particulate porous skeleton, expressed as a percentage with respect to P1. VP10 and VP20 are measured by nitrogen gas adsorption. VP20 can be at least 80%, or at least 90%, or at least 95%, or at least 97%, or at least 98%. VP10 can be at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 97%.

[0023] VP20-VP5 is the pore volume of the particulate porous framework with a pore diameter greater than 5.0 nm and less than or equal to 20.0 nm, expressed as a percentage of P1. VP20-VP5 may be less than 20%, less than 15%, preferably less than 12%, preferably less than 10%, or more preferably less than 9%. Optionally, VP20-VP5 may be at least 0.5%, or at least 1%, or at least 2%. VP20-VP5 may be 0.5-20%, 0.5-15%, or 1-12%, or 2-10%, or 2-9%, or 3-9%. Particulate porous frameworks with VP20-VP5 values ​​within these ranges have been found to result in further improvements to surface silicon.

[0024] VP20-VP2 may be at least 45%, or at least 50%, or at least 55%.

[0025] Particulate porous frameworks are characterized by the total volume P1 of micropores and mesopores (i.e., the total pore volume in the pore size range of 0–50 nm). Typically, particulate porous frameworks contain both micropores and mesopores. However, the use of particulate porous frameworks that contain micropores but not mesopores is not ruled out. The P1 of a particulate porous framework is at least 0.35, or at least 0.4, or at least 0.5, 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. Using highly porous particles can be advantageous because it allows for the accommodation of more electroactive material within the pore volume.

[0026] The internal pore volume of the 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 P1 of the particulate porous framework may be ≤2.5, ≤2.0, ≤1.8, ≤1.7, ≤1.6, ≤1.55, ≤1.5, ≤1.45, ≤1.4, ≤1.35, ≤1.3, ≤1.25, ≤1.2, or ≤1.1.

[0027] Preferably, the particulate porous framework P1 is in the range of 0.4 to 1.8, or 0.5 to 1.6, or most preferably 0.6 to 1.2.

[0028] The total volume of micropores and mesopores, and the pore size distribution of micropores and mesopores (P1, VP07, VP1, VP2, VP5, VP10, VP20, and PD as defined herein). n (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 -7 The pore size distribution is determined, preferably according to the standard methodology described in 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 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 ASAP 2020 Plus porosity analyzer available from Micromeritics Instrument Corporation, USA, and the Autosorb IQ porosity analyzer available from Quantachrome Instruments.

[0029] In this specification, references to porosity parameters of particulate porous frameworks refer to the internal pore volume of the particulate porous framework measured in isolation (i.e., the absence of electroactive material or other material occupying part or all of the pore volume).

[0030] 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.

[0031] Given the limitations of available analytical techniques, it is impossible to measure pore volume and pore size distribution across the entire range of micropores, mesopores, and large pores using a single technique. When the particulate porous framework contains large pores, the volume of pores with diameters ranging from 50 nm to 100 nm can be measured by mercury porosimetry, preferably 0.3 cm³. 3 Less 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 large pores 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 optionally in mesopores.

[0032] 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.

[0033] 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, see "Analytical Methods in Fine Particle Technology," 1997, Micromeritics Instrument Corporation, ISBN 0-9656783-0, by PAWebb and C. Orr.

[0034] It will be understood that penetration techniques such as gas adsorption and mercury porosimetry are only effective when determining the pore volume of pores that are accessible to nitrogen or mercury from outside the particulate porous framework. The porosity values ​​defined herein will be understood to refer to the volume of open pores, i.e., pores 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 the porosity value. Similarly, pore volumes in pores so small that they are below the detection limit by nitrogen adsorption are not considered.

[0035] The pore structure of a particulate porous framework may include a unimodal, bimodal, or multimodal pore size distribution. As used herein, the term “pore size distribution” refers to the pore size distribution relative 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.

[0036] 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, large pore volume (pore diameter exceeding 50 nm) is not considered. The particulate porous framework is preferably PD of 25 nm or less, or 1 to 20 nm, or 1.5 to 10 nm, or 2 to 9 nm. 90 It has a pore size. The particulate porous framework preferably has PD of 4 nm or less, or 3 nm or less, or 1 to 2.5 nm. 50 It has a pore size.

[0037] The particulate porous framework may have mode pore diameters of 0.50 nm or larger, preferably 0.60 nm or larger, for both micropores and mesopores.

[0038] When the particulate porous framework contains large pores, the volume of pores in the range from 50 nm to 100 nm is P2 cm². 3It may be called / g and is measured by mercury porosimetry. The large pore volume (and therefore the value of P2) is preferably small compared to the volumes of micropores and mesopores (and therefore the value of P1). A small amount of large pores may be useful in facilitating electrolyte access to the pore network, but the advantages of the present invention are substantially obtained by housing the electroactive material in micropores and even smaller mesopores. Therefore, the P2 of the particulate porous framework preferably has a value of less than 0.2 × P1, or less than 0.1 × P1, or less than 0.05 × P1, or less than 0.02 × P1, or less than 0.01 × P1, or less than 0.005 × P1.

[0039] P2 may be less than 15%, less than 10%, less than 8%, or less than 5% of the total volume of micropores, mesopores, and pores having a diameter of more than 50 to 100 nm.

[0040] Generally, composite particles have a diameter of 100 μm or less, or preferably 30 μm or less. 50 It has a particle size. Optionally, the D of the composite particle 50 The particle size may be at least 1 μm, or at least 1.5 μm, or at least 2 μm, or at least 2.5 μm, or at least 3 μm, or at least 4 μm, or at least 5 μm. Optionally, the D of the composite particles 50 The particle size may be 25 μm or less, or 20 μm or less, or 18 μm or less, or 15 μm or less, or 12 μm or less, or 10 μm or less, or 8 μm or less.

[0041] D of composite particles 10 The particle size 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. 10 Maintaining a particle size of 0.5 μm or larger reduces the possibility of undesirable aggregation of submicron-sized particles, improving the dispersibility of the resulting composite particles.

[0042] The D1 particle size of the composite particles is preferably at least 0.5 μm, or 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. By controlling the D1 particle size, the presence of very small particle sizes is reduced, and the harmful effects of high aggregation and surface area associated with very small particles are mitigated.

[0043] The D0 particle size of the composite particles is preferably at least 0.3 μm, or at least 0.5 μm, or at least 1 μm.

[0044] D of composite particles 90 The particle size is preferably 50 μm or less, or 40 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less, or 15 μm or less.

[0045] D of composite particles 98 The particle size is preferably 35 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less, or 15 μm or less. 98 By controlling the particle size, the presence of a small number of oversized particles remaining within the composite particle population is reduced, mitigating the detrimental effects on packing efficiency and decreasing heterogeneity within the electrode layer associated with oversized particles.

[0046] D of composite particles 100 The particle size is preferably 40 μm or less.

[0047] The composite particles preferably have a narrow size distribution span. For example, the particle size distribution span ((D 90 -D 10 ) / D 50 The particle size distribution span (D), defined as D, 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. 98 -D1) / D 50 It is preferable that it is less than 2.98 Maintaining a precise distribution between particle size and D1 particle size is thought to facilitate the deposition of electroactive materials when preparing composite particles by ensuring a uniform distribution of the framework within the reaction vessels typically used during manufacturing.

[0048] Control of particle size distribution can be achieved by known classification methods such as dynamic air classification, hydraulic classification, and gravity separation. Suitable classifiers include dynamic air classifiers such as the Alpine TTD Ultra-Fine Air Classifier from Hosokawa Micron Powder Systems.

[0049] As used herein, the term “particle diameter” refers to the equivalent spherical 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. n " and "D n The term "particle diameter" refers to the volume-based median particle diameter, i.e., the diameter below which n% of the volume of a particle population lies.

[0050] 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, and the dispersant index is assumed to be 1.378. The particle size distribution is calculated using a Mie scattering model.

[0051] The composite particles 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 composite particles have an average sphericity of at least 0.90, or at least 0.92, or at least 0.93, or at least 0.94, or at least 0.95. Spherical particles are thought to enhance depositional uniformity and promote high-density packing both in batch pressure reactors and in the final product incorporated into electrodes.

[0052] 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 and the circumference of the circle are the same. Therefore, the sphericity S of an individual particle can be defined as follows:

number

number

[0053] The particle size distribution of the particulate porous framework is assumed not to change due to the process of forming the composite particles (e.g., step (b)). Therefore, the particle size distribution parameters defined for the composite particles can also be used to define the particulate porous framework (e.g., D50 (Sphericity, etc.)

[0054] The particulate porous framework preferably has a thickness of at least 750 m 2 / g, more preferably at least 1,000m 2 / g, or at least 1,100m 2 / 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, in accordance with ISO 9277:2022. Preferably, the BET surface area of ​​the particulate porous framework is 4,000 m² / g. 2 / g or less, or 3,500m 2 Less than / g, or 3,250m 2 / g or less, or 3,000m 2 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.

[0055] The composite particles are preferably 300 m 2 / g or less, or 250m 2 / g or less, or 200m 2 / g or less, or 150 m 2 / g or less, or 100 m 2 / g or less, or 80 m 2 / g or less, or more preferably 60 m 2 / g or less, or 50 m 2 / g or less, or 40 m 2 / g or less, or 30 m 2 / g or less, or 25 m 2 / g or less, or 20 m 2 / g or less, or 15 m 2 / g or less, or 10 m 2 / g or less, or 5 m 2 It has a BET surface area of / g or less. Generally, 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, it is preferable that the BET surface area is low. However, if the BET surface area is too low, most of the electroactive material will not allow metal ions in the surrounding electrolyte to access, resulting in unacceptably low charging rates and capacities. The BET surface area is preferably at least .1 m 2 / g, or at least 1 m 2 / g, or at least 2 m 2 / g, or at least 5 m 2 / g. For example, the BET surface area of the composite particles is 2 0.1 - 100 m 2 / g, or 2 0.1 - 80 m 2 / g, or 2 0.5 - 60 m 2 / g, or 2 0.5 - 40 m 2 / g, or 2 1 - 30 m 2 / g, or 2 1 - 25 m 2 / g, or 2 1 - 20 m 2 / g, or 2 1 - 15 m 2 / g, or 2 2 - 10 m 2 / g and can be in the range of.

[0056] The composite particles preferably have a particle density of at least 0.35, preferably less than 3 g / cm 3 and more preferably less than 2 g / cm 3 and even more preferably less than 1.5 g / cm 3It is even more preferable that it be less than 0.35 to 1.2 g / cm³. 3 It is most preferable that the particle density is as follows: As used herein, the term “particle density” refers to the “apparent particle density” measured by mercury porosimetry (i.e., the value obtained by dividing the mass of the particles by the volume of the particles, where the particle volume is the sum of the volume of the solid material and the closed or blind pores (“blind pores” are pores too small to be measured by mercury porosimetry)). Preferably, the composite particles have 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 composite particles have a density of 1.15 g / cm³. 3 The following, or 1.1 g / cm³ 3 The following, or 1.05 g / cm³ 3 The following, or 1 g / cm³ 3 The following, or 0.95 g / cm³ 3 The following, or 0.9 g / cm³ 3 It has the following particle density.

[0057] In one embodiment, the present invention provides composite particles for use as an electroactive material in a metal ion battery, wherein the composite particles are A particulate porous framework containing micropores and optionally mesopores, It comprises electroactive material domains located within the pores of a particulate porous framework, P1 is cm 3 Expressed in g, P1 is the total volume of micropores and mesopores in the particulate porous framework, and P1 is between 0.35 and 1.8. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP07 is in the range of 7-35%. VP2 is the volume of pores with a diameter of 2.0 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP2 is at least 20%. VP10 is the volume of pores with a diameter of 10.0 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP10 is at least 70%. VP20 is the volume of pores with a diameter of 20.0 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP20 is at least 80%. VP5 is the volume of pores with a diameter of 5.0 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP20-VP5 is less than 15%. P1, VP07, VP5, VP10, and VP20 were measured by nitrogen gas adsorption. When measured by laser diffraction, the composite particles have a diameter of 30 μm or less. 50 It has a particle size.

[0058] In one embodiment, the present invention provides composite particles for use as an electroactive material in a metal ion battery, wherein the composite particles are A particulate porous framework containing micropores and optionally mesopores, It comprises electroactive material domains located within the pores of a particulate porous framework, P1 is cm 3 Expressed in g, P1 is the total volume of micropores and mesopores in the particulate porous framework, and P1 is between 0.4 and 1.8. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP07 is in the range of 10-30%. VP2 is the volume of pores with a diameter of 2.0 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP2 is at least 20%. VP10 is the volume of pores with a diameter of 10.0 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP10 is at least 70%. VP20 is the volume of pores with a diameter of 20.0 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP20 is at least 80%. VP5 is expressed as a percentage of P1 and represents the volume of pores with a diameter of 5.0 nm or less in the particulate porous framework, where VP20-VP5 is 1-9%. P1, VP07, VP5, VP10, and VP20 were measured by nitrogen gas adsorption. When measured by laser diffraction, the composite particles have a diameter of 30 μm or less. 98 The particle has a particle diameter and a D1 particle diameter of at least 1 μm.

[0059] In another aspect, the present invention provides composite particles for use as an electroactive material in a metal-ion battery, wherein the composite particles are A particulate porous carbon skeleton containing micropores and optionally mesopores, It comprises silicon domains located within the pores of a particulate porous carbon skeleton, P1 is cm 3 Expressed in g, P1 is the total volume of micropores and mesopores in the particulate porous carbon skeleton, and P1 is between 0.4 and 1.8. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous carbon skeleton, expressed as a percentage of P1, and VP07 is in the range of 7-30%. P1 and VP07 were measured by nitrogen gas adsorption. When measured by laser diffraction, the composite particles have a diameter of 30 μm or less. 50 Having particle size, The composite particles contain 20-80% by weight of silicon.

[0060] In another aspect, the present invention provides composite particles for use as an electroactive material in a metal-ion battery, wherein the composite particles are A particulate porous carbon skeleton containing micropores and optionally mesopores, It comprises silicon domains located within the pores of a particulate porous carbon skeleton, P1 is cm 3Expressed in g, P1 is the total volume of micropores and mesopores in the particulate porous carbon skeleton, and P1 is between 0.5 and 1.6. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous carbon skeleton, expressed as a percentage of P1, and VP07 is in the range of 10-27%. P1 and VP07 were measured by nitrogen gas adsorption. When measured by laser diffraction, the composite particles have a diameter of 1-30 μm. 50 Having particle size, When composite particles are measured by laser diffraction, the particle size distribution span (D) is 98 -D1) / D 50 If it is less than 2, The composite particles contain 20–80% by weight of silicon, and as determined by thermogravimetric analysis (TGA), at least 20% by weight of the silicon is surface silicon.

[0061] In another aspect, the present invention provides composite particles for use as an electroactive material in a metal-ion battery, wherein the composite particles are A particulate porous carbon skeleton containing micropores and optionally mesopores, It comprises silicon domains located within the pores of a particulate porous carbon skeleton, P1 is cm 3 Expressed in g, this is the total volume of micropores and mesopores in the particulate porous carbon skeleton, where P1 is at least 0.35. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous carbon skeleton, expressed as a percentage of P1, and VP07 is in the range of 5.1 to 35%. The micropore volume of the particulate porous carbon skeleton is at least 0.3 cm³. 3 / g P1, VP07, and micropore volume were measured by nitrogen gas adsorption. When measured by laser diffraction, the composite particles have a diameter of 30 μm or less. 50 Having particle size, The composite particles contain 20-80% by weight of silicon.

[0062] In another aspect, the present invention provides composite particles for use as an electroactive material in a metal-ion battery, wherein the composite particles are A particulate porous carbon skeleton containing micropores and optionally mesopores, It comprises silicon domains located within the pores of a particulate porous carbon skeleton, P1 is cm 3 Expressed in g, this is the total volume of micropores and mesopores in the particulate porous carbon skeleton, where P1 is at least 0.35. VP07 and VP2 are expressed as percentages of P1, representing the volume of pores in the particulate porous carbon skeleton with pore diameters of 0.7 nm or less and 2.0 nm or less, respectively. VP07 is in the range of 5.1 to 35%, and VP2 is at least 2.5 × VP07. The micropore volume of the particulate porous carbon skeleton is at least 0.3 cm³. 3 / g P1, VP07, VP2, and micropore volume were measured by nitrogen gas adsorption. When measured by laser diffraction, the composite particles have a diameter of 30 μm or less. 50 Having particle size, The composite particles contain 20–80% by weight of silicon, and as determined by thermogravimetric analysis (TGA), at least 20% by weight of the silicon is surface silicon.

[0063] In another aspect, the present invention provides composite particles for use as an electroactive material in a metal-ion battery, wherein the composite particles are A particulate porous carbon skeleton containing micropores and optionally mesopores, It comprises silicon domains located within the pores of a particulate porous carbon skeleton, P1 is cm 3 Expressed in g, this is the total volume of micropores and mesopores in the particulate porous carbon skeleton, where P1 is at least 0.35. VP07, VP2, VP5, and VP20 are expressed as percentages of P1 and represent the volume of pores in the particulate porous carbon skeleton with pore diameters of 0.7 nm or less, 2.0 nm or less, 5.0 nm or less, and 20.0 nm or less, respectively. VP07 is in the range of 5.1-35%, VP2 is in the range of 45-90%, and VP20-VP5 are less than 20%. The particulate porous carbon skeleton has a minimum thickness of 1,000 m 2 Having a BET surface area of ​​ / g, P1, VP07, VP2, VP5, and VP20 were measured by nitrogen gas adsorption. When measured by laser diffraction, the composite particles have a diameter of 30 μm or less. 50 Having particle size, The composite particles contain 20-80% by weight of silicon.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] As used herein, the term “hard carbon” refers to a nanoscale polycyclic aromatic domain in which carbon atoms are primarily sp-coupled. 2This 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.

[0068] When the particulate porous framework is a particulate porous carbon framework, the particulate porous carbon framework is measured by Raman spectroscopy, and the ratio of the relative intensities of the D peak to the G peak (I D / I G ) may be 2.0 or less or 1.8 or less. Alternatively or additionally, the I of the particulate porous carbon skeleton D / I G I can be 0.6 or higher, or 0.8 or higher, or 1 or higher, or 1.05 or higher. For example, I of a particulate porous carbon skeleton D / I G This can be in the range of 0.6 to 1.8, or 1.0 to 1.6.

[0069] The particulate porous framework can be provided by synthesizing the framework or by obtaining the framework from a supplier.

[0070] 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 activation 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 pyrolytic carbon with one or more of oxygen, steam, CO, and CO2 at temperatures in the range of 300-1500°C, 600-1200°C, or 600-1000°C.

[0071] Alternatively, a skeleton with a controlled pore structure can be obtained by template-assisted carbonization using zeolites, employing known methods. Another approach involves carbonizing a metallic organic skeleton, such as a zinc imidazolate skeleton, and then washing the carbonized material to remove residual metal, thereby obtaining a skeleton with a controlled pore structure.

[0072] Mesopores can also be obtained by known stenography processes using extractable pore-forming agents such as MgO and other colloidal or polymer templates, and these templates can be removed by thermal or chemical means after thermal decomposition or activation.

[0073] Depending on the starting materials and the conditions of the pyrolysis process, various different particulate porous carbon skeletons are available in this art. Particulate porous carbon skeletons of various different specifications are available from commercial suppliers.

[0074] Various different 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 husks and shells (including coir), peanuts, walnuts, apricots, almonds, palm seeds, peaches, olives, hazelnuts, bamboo, and tree bark (e.g., the bark of conifers including pine, spruce, larch, and poplar, and the bark of broad-leaved trees including oak). A preferred plant source is coconut husk. 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.

[0075] The carbonaceous material, for example, a plant source, preferably has an elemental composition containing at least 40% by weight of carbon, at least 3% by weight of hydrogen, and at least 30% by weight of oxygen. Trace amounts of nitrogen, sulfur, and chlorine may also be present. More preferably, the carbonaceous material has an elemental composition containing about 50% by weight of carbon, about 5% by weight of hydrogen, and about 40% by weight of oxygen, with smaller amounts of nitrogen, sulfur, and chlorine present.

[0076] Particulate porous carbon skeletons are typically obtained from carbonaceous materials 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 before heating to obtain particles of uniform size. Optionally, the carbonaceous material is pelletized before heating.

[0077] 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.

[0078] 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.

[0079] The burnup rate of the pyrolysis material during activation is preferably at least 15%, or at least 30%, or at least 40%. The burnup rate is preferably 80% or less, or 75% or less, or 70% or less. The burnup 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.

[0080] 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.

[0081] It has been found that particulate porous carbon skeletons with target VP07 values ​​and other desirable porosity parameters as defined herein can be obtained by controlling processing parameters during the carbon activation process. It is thought that as the activation time increases, VP07 increases up to a certain limit, and then decreases thereafter. For example, in the case of synthetic carbon (polymers or resins) activated with CO2 at different levels of combustion rate (38 wt%, 47 wt%, and 55 wt%), it has been observed that VP07 increases as the level of combustion rate decreases. P1 increases as the level of combustion rate increases. A similar trend was observed when steam activation was used. It has been found that CO2 activation yields higher VP07 values ​​than steam activation when the combustion rate is at the same level for both synthetic carbon and plant-derived carbon.

[0082] A process for producing a particulate porous carbon skeleton as defined herein is provided, which includes activating pyrolysis carbon by heating it in a CO2 stream at a temperature of 600°C to 1200°C, wherein the combustion rate of the pyrolysis carbon is 50% by weight or less, or 45% by weight or less, and optionally at least 15%. This process may constitute step (a) in a process for preparing composite particles provided herein. Thus, this process is preferably followed by a step of (b) depositing electroactive material domains in the pores of the particulate porous skeleton.

[0083] Additional information on the synthesis of activated carbon with the target pore structure can be found in *Porous Carbons: Syntheses and Applications* (Kang, Feiyu; Inagaki, Michio; Itoi, Hiroyuki; Elsevier; ISBN 978-0-12-822115-0).

[0084] A typical example of activated carbon synthesis is as follows:

[0085] 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. 3 The 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.

[0086] Examples of activated carbon produced by steam activation are as follows:

[0087] 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. 50The 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.

[0088] Alternatives to the particulate porous carbon skeleton include particulate porous skeletons formed from 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 formed from titanium nitride, silicon oxycarbide, or boron nitride.

[0089] The electroactive material can be appropriately selected from silicon, tin, germanium, aluminum, and mixtures and alloys thereof. Silicon is a particularly preferred electroactive material. The electroactive material may optionally contain trace amounts of one or more dopants. Suitable dopants include boron, phosphorus, other n-type or p-type dopants, or nitrogen. Preferably, the dopants are present in a total amount of 2% by weight or less, based on the total amount of the electroactive material (e.g., silicon) and the dopant(s).

[0090] The particulate porous framework provides the framework for electroactive material domains. The term “electroactive material domain” typically refers to the body of the electroactive material in elemental form, whose maximum dimensions are determined by the dimensions of the pores in the particulate porous framework in which the electroactive material is located. Electroactive material domains are typically located within the micropores and optionally mesopores of the particulate porous framework. Thus, depending on the size of the micropores and mesopores, 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 the micropores and mesopores, electroactive domains typically have a maximum dimension of less than 50 nm in any direction, and are usually significantly below 50 nm. Domains can take the form of, for example, regular or irregular particles, or layers or regions with coating boundaries.

[0091] The particulate porous framework defined herein as part of the composite particles of the present invention may be provided alone, i.e., without electroactive material domains located within the pores. This represents a convenient starting material for the production of the composite particles of the present invention. Accordingly, the present invention provides a particulate porous framework comprising micropores and optionally mesopores. P1 is cm 3 Expressed in g, this is the total volume of micropores and mesopores in the particulate porous framework, and P1 is at least 0.35. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP07 is in the range of 5.1 to 40%. P1 and VP07 are measured by nitrogen gas adsorption.

[0092] The particulate porous framework may be provided as a kit together with an electroactive material precursor. The components of the kit can be kept separately until the electroactive material domains are deposited into the pores of the particulate porous framework using the electroactive material precursor.

[0093] A process for preparing composite particles includes (a) providing a particulate porous framework as defined herein, and (b) depositing electroactive material domains in the pores of the particulate porous framework. Step (b) typically includes contacting the particulate porous framework with an electroactive material precursor at a temperature effective for depositing electroactive material domains in the pores of the particulate porous framework. The precursor is most preferably a gas because it can be conveniently used in the CVI process.

[0094] Suitable silicon precursors are silane (SiH4), disilane (Si2H6), trisilane (Si3H8), and tetrasilane (Si4H 10 ), Pentasilane (Si5H 12 ), Hexasilane (Si6H 14 ), methylsilane (CH3SiH3), dimethylsilane ((CH3)2SiH2), trimethylsilane ((CH3)3SiH), tetramethylsilane ((CH3)4Si), or chlorosilane, for example trichlorosilane (HSiCl3) or dichlorosilane (H2SiCl2) or chlorosilane (H3SiCl), or methylchlorosilane, for example methyltrichlorosilane (CH3SiCl3) or dimethyldichlorosilane (((CH3)2SiCl2). Preferably, the silicon precursor includes silane (SiH4), disilane (Si2H6), trisilane (Si3H8), tetrasilane (Si4H 10 A silicon precursor is selected from the following. A particularly preferred silicon precursor is silane (SiH4).

[0095] Suitable germanium precursors include germane (GeH4), hexamethyldigermanium ((CH3)3GeGe(CH3)3), tetramethylgermanium ((CH3)4Ge), tributylgermanium hydride ([CH3(CH2)3]3GeH), triethylgermanium hydride ((C2H5)3GeH), and triphenylgermanium hydride ((C6H5)3GeH). The preferred germanium precursor is germane.

[0096] Suitable tin precursors include bis[bis(trimethylsilyl)amino]tin(II)([[(CH3)3Si]2N]2Sn), tetraallylutin((H2C=CHCH2)4Sn), tetrakis(diethylamide)tin(IV)([(C2H5)2N]4Sn), tetrakis(dimethylamide)tin(IV)([(CH3)2N]4Sn), tetramethyltin(Sn(CH3)4), tetravinyltin(Sn(CH=CH2)4), and tin(II) acetylacetonate(C 10 H 14 It contains O4Sn), trimethyl(phenylethynyl)tin (C6H5C≡CSn(CH3)3), and trimethyl(phenyl)tin (C6H5Sn(CH3)3). A preferred tin precursor is tetramethyltin.

[0097] Suitable aluminum precursors include aluminum tris(2,2,6,6-tetramethyl-3,5-heptanedione)(Al(OCC(CH3)3CHCOC(CH3)3)3), trimethylaluminum((CH3)3Al), and tris(dimethylamide)aluminum(III)(Al(N(CH3)2)3). The preferred aluminum precursor is trimethylaluminum.

[0098] Step (b) is appropriately carried out by chemical vapor infiltration (CVI) of a gaseous electroactive material precursor into the pore structure of a particulate porous framework. As used herein, CVI refers to the process by which a gaseous precursor is thermally decomposed on the surface, typically forming an electroactive material on the surface in elemental form and producing gaseous byproducts. 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.

[0099] 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.

[0100] The gaseous electroactive material 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 (b) involves contacting a particulate porous skeleton 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 the gaseous electroactive material precursor, based on the total volume of the gas.

[0101] In accordance with conventional procedures for working in an inert atmosphere, the presence of oxygen in step (b) 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 (b).

[0102] The temperature in step (b) 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.

[0103] The pressure in step (b) may be in the range of 1–5000 kPa, or 20–500 kPa, or 40–200 kPa, or 50–150 kPa, or 60–120 kPa, or 80–100 kPa. The pressure in step (b) may be 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 reaction vessel. By selecting a particulate porous framework with a small pore diameter of 0.7 nm or less and a considerable pore volume, it is considered advantageous to deposit electroactive materials under high pressure to promote deposition within small pores. Therefore, in one embodiment, the pressure in step (b) is at least 150 kPa, or at least 200 kPa, and optionally 5000 kPa or less, or 3000 kPa or less, or 2000 kPa or less. For example, preferably, the pressure in step (b) is in the range of 200 to 2000 kPa.

[0104] The deposition of electroactive material by CVI removes byproducts, particularly byproduct gases such as hydrogen. Step (b) preferably further includes separating the byproducts from the particles formed in step (b). 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 (b) 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 electroactive material.

[0105] It is possible to incorporate various different electroactive materials into the composite particles. The composite particles preferably contain 20-80% by weight of electroactive material, or 30-70% by weight of electroactive material, or 40-60% by weight of electroactive material. The composite particles may contain at least 26% by weight of electroactive material, or at least 28% by weight of electroactive material, or at least 30% by weight of electroactive material, or at least 32% by weight of electroactive material, or at least 34% by weight of electroactive material, or at least 36% by weight of electroactive material, or at least 38% by weight of electroactive material, or at least 40% by weight of electroactive material, or at least 42% by weight of electroactive material, or at least 44% by weight of electroactive material. If the electroactive material is silicon, these ranges may refer to the amount of silicon, for example, the composite particles preferably contain 20-80% by weight of silicon.

[0106] The amount of electroactive material in the composite particles is preferably selected such that, after step (b), the electroactive material occupies at least 20% and up to 90% of the internal pore volume of the particulate porous framework. For example, the electroactive material 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 particulate porous framework. Within these preferred ranges, the remaining pore volume of the particulate porous framework is effective in accommodating the expansion of the electroactive material during charging and discharging without resulting in 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.

[0107] When the electroactive material is silicon, the amount of silicon in the composite particles can be related to the available pore volume of the particulate porous framework, provided that the mass ratio of silicon to the particulate porous framework is in the range of [0.5×P1~1.9×P1]:1, where P1 is as defined above (for example, the total volume of micropores and mesopores in the particulate porous framework is 1.2 cm³).3 (For / g, P1 = 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 particulate porous framework. Preferably, the weight ratio of silicon to particulate porous framework is in the range of [0.6×P1~1.8×P1]:1 or [0.7×P1~1.7×P1]:1 or [0.8×P1~1.6×P1]:1.

[0108] The amount of silicon or other electroactive material in the composite particles can be determined by elemental analysis. The electroactive material 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 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.

[0109] Preferably, at least 70%, 80%, 85%, 90%, 95%, or most preferably 98% by weight of the electroactive material in the composite particles is located within the internal pore volume of the particulate porous framework, and there is no electroactive material at all, or only a very small amount, on the outer surface of the particulate porous framework. As described above, the deposition of the 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 the electroactive material occurs almost completely within the pores of the particulate porous framework.

[0110] The nitrogen-accessible pore volume of the composite particles may be less than 0.05 × P1, where P1 is cm 3This is expressed as the total volume of micropores and mesopores in the particulate porous framework before the electroactive material is deposited within the pores of the particulate porous framework, expressed as 1 / g. Absolutely speaking, the total volume of micropores and mesopores in the composite particles after the deposition of the electroactive material is preferably 0.03 cm³. 3 Less than / g or 0.01cm 3 It is less than / g.

[0111] Composite particles can be characterized by their performance in air using thermogravimetric analysis (TGA). This analytical method is based on the principle that electroactive materials increase in weight when oxidized in air and at high temperatures.

[0112] 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.

[0113] 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%

[0114] 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 a sample between 150°C and 500°C, M f is the mass of the sample when oxidation is complete at 1400°C. For completeness, it should 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.

[0115] It has been found that when the surface silicon measured by the TGA method described above is at least 10% by weight of the total silicon amount in the composite particles, reversible capacity retention over multiple charge / discharge cycles is significantly improved. Therefore, preferably, at least 10% by weight, or at least 15% by weight, or more 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 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 a 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.

[0116] The fact that a significant proportion of hydride-terminated silicon can be measured 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.

[0117] Because the electrolyte cannot access the internal voids, the silicon surface is protected from SEI formation, thereby 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.

[0118] 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 herein as silicon oxidized at over 800°C as determined by TGA, and TGA is performed in air at a temperature rise rate of 10°C / min. Thus, the rough bulk silicon content is determined according to the following formula. Z = 1.875 × [(M f -M 800 ) / M f ] × 100%

[0119] 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.

[0120] Silicon that oxidizes above 800°C is undesirable. Preferably, as determined by TGA, 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 of silicon.

[0121] 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.

[0122] When the particulate porous framework is a 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 It can be 0.6 or greater, or 0.8 or greater, or 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 0.6 to 1.8, or 1.0 to 1.6.

[0123] This process may include, after step (b), an annealing step in which the composite particles are annealed at a high temperature under an inert or reducing atmosphere.

[0124] 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).

[0125] 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, or 850°C or lower, or 800°C or lower, or 750°C or lower, or 700°C or lower, or 680°C or lower, or 660°C or lower, or 650°C or lower.

[0126] 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.

[0127] The temperature in the annealing step may be higher than the temperature in step (b). Preferably, the temperature in the annealing step is at least 20°C, or at least 40°C, or at least 60°C, or at least 80°C, or at least 100°C, or at least 120°C, or at least 140°C, or at least 150°C higher than the temperature in step (b).

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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, or 14:1 or less, or 13:1 or less, or 12:1 or less.

[0134] 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.

[0135] 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.

[0136] 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, or 0.7:1 or less, or 0.6:1 or less, or 0.5:1 or less.

[0137] 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.

[0138] This process may include a passivation step after step (b), in which the composite particles are brought into contact with a passivating agent.

[0139] As defined herein, a passivator is a compound or mixture of compounds that can react with the silicon surface deposited in step (b) 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.

[0140] Preferably, the passivation step is performed after the annealing step. As described above, one of the effects of the annealing step is to reopen pore spaces that were previously blocked or capped by the silicon nanostructure, allowing the passivation gas to access these pore spaces, thus enabling more extensive passivation of the silicon surface and removal of hydrogen-terminated silicon surfaces.

[0141] 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.

[0142] 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 - 700 °C, preferably 400 - 700 °C, more preferably 400 - 600 °C. Next, the temperature can be raised to the range of 500 - 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. Since nitrides with a sub-stoichiometric ratio (such as SiN x where 0 < x ≦ 4 / 3) are conductive, the nitride passivation layer can function as a conductive network that enables faster charging and discharging of electroactive materials. Phosphine, as a phosphorus analogue of ammonia, can also be used as a passivating agent. Another type of passivation layer is, for example, an 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 has the formula SiO x N yIt may contain silicon oxynitride, where 0 < x < 2, 0 < y < 4 / 3, and 0 < (2x + 3y) ≦ 4). The silicon nitride is preferably amorphous silicon oxynitride.

[0143] 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 at a high temperature in the range of, for example, 250 to 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.

[0144] 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 1 independently represents H or an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, or two R 1 groups form an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring.

[0145] Particularly preferred passivating agents include one or more compounds of the following formulas (i) CH2=CH-R 1 and (ii) HC≡C-R 1 , where R1 This is as defined above. Preferably, R 1 It has not been replaced.

[0146] 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.

[0147] 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]

[0148] 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.

[0149] 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 2represents 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.

[0150] Preferably, X represents O or NH.

[0151] Preferably, R 2 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, or purine.

[0152] 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.

[0153] This process may include a deposition step after step (b) 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.

[0154] 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.

[0155] 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.

[0156] 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 at least 300°C, or at least 350°C, or at least 400°C, or at least 450°C, or at least 500°C.

[0157] 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.

[0158] 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.

[0159] One of the advantages of the present invention is that by determining an optimized pore structure based on VP07, 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 an electroactive material 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 framework sources can be measured. Once a group of optimized particulate porous frameworks is identified, silicon can be used to deposit silicon in the pores, thereby providing composite particles.

[0160] Therefore, the present invention is (a1) Providing a group of one or more particulate porous skeletons including micropores and optionally mesopores, (a2) A step of measuring the pore structure of each group, (a3) A step of accepting each group having an optimized pore structure and not accepting each group not having an optimized pore structure, wherein the optimized pore structure is P1 is cm 3 Expressed in g, this is the total volume of micropores and mesopores in the particulate porous framework, where P1 is at least 0.35. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP07 is in the range of 5.1 to 40%. P1 and VP07 are measured by nitrogen gas adsorption, in the steps of acceptance and non-acceptance. (b) A process is provided which includes the step of depositing electroactive material domains in the pores of an accepted collection of particulate porous frameworks.

[0161] It will be understood that the optimized pore structure can be further defined by any of the pore structure parameters defined above for the particulate porous framework.

[0162] 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 (a1), and at least one of them is optionally rejected in step (a3). 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.

[0163] After measuring the pore structure of 10 populations at will, the process can be stopped if no population is acceptable. Thus, the useful information that the 10 unaccepted populations lack an optimized pore structure is still provided.

[0164] One advantage of the present invention is that it is not necessary to provide all feasible particulate porous frameworks on an industrial scale before it can be determined whether they are suitable for end use, and the identity of optimized particulate porous frameworks can be determined on a laboratory scale. For example, the aggregate of optimized particulate porous frameworks provided in steps (a) and (a1) may be less than 50 kg or less than 10 kg. Once optimized particulate porous frameworks have been identified in the laboratory, they can be made available on a larger scale with confidence that they are suitable for mass production of composite particles with superior properties. The process of the present invention therefore preferably further comprises providing an industrial-scale aggregate of the accepted aggregate of particulate porous frameworks, optionally comprising at least 100 kg or at least 1,000 kg of the accepted particulate porous frameworks, wherein electroactive material domains are deposited in the pores of the industrial-scale aggregate of the accepted particulate porous frameworks. A kit comprising the industrial-scale aggregate and a silicon precursor may be provided.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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).

[0173] 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.

[0174] 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, carboxymethyl cellulose (CMC), modified carboxymethyl cellulose (mCMC), sodium carboxymethyl cellulose (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 polymers selected from polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0175] The binder may be present in an amount suitably of 0.5 to 20% by weight, preferably 1 to 15% by weight, preferably 2 to 10% by weight, most preferably 5 to 10% by weight, based on the total dry weight of the composition.

[0176] The binder may optionally be present in combination with one or more additives that modify the properties of the binder, such as a crosslinking promoter, a coupling agent, and / or an adhesion promoter.

[0177] The composition may optionally contain one or more conductive additives. Preferred conductive additives are non-electroactive materials included to improve the electrical conductivity between the electroactive components of the composition and between the electroactive components of the composition and the current collector. The conductive additive may be selected from carbon black, carbon fiber, carbon nanotube, graphene, acetylene black, ketjen black, metal fiber, metal powder, and conductive metal oxide. Preferred conductive additives include carbon black and carbon nanotubes.

[0178] One or more conductive additives may be present in a total amount suitably of 0.5 to 20% by weight, preferably 1 to 15% by weight, preferably 2 to 10% by weight, most preferably 5 to 10% by weight, based on the total dry weight of the composition.

[0179] The present invention also provides an electrode comprising composite particles. The electrode is typically in the form of a current collector, and 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 the composite particles and at least one other component as defined above.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] 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 Ni 0.15 Al 0.05 O2, LiLiLi 0.4 Co 0.3 Mn 0.3 O2 and LiNi 0.33 Co 0.33 Mn 0.34 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.

[0185] 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.

[0186] 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.

[0187] Examples of inorganic solid electrolytes include nitrides, halides, and sulfides of lithium salts, such as Li5NI2, Li3N, LiI, LiSiO4, Li2SiS3, Li4SiO4, LiOH, and Li3PO4.

[0188] Lithium salts dissolve well in selected solvents or mixtures of solvents. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO4, LiBF4, LiBC4O8, LiPF6, LiCF3SO3, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, and CF3SO3Li.

[0189] When the electrolyte is a non-aqueous organic solution, a rechargeable metal ion battery preferably has a separator interposed between the anode and the cathode. The separator is typically formed of an insulating material with high ion permeability and high mechanical strength. The separator typically has a pore diameter of 0.01 to 100 μm and a thickness of 5 to 300 μm. Examples of suitable electrode separators include microporous polyethylene films. The separator can be replaced with a polymer electrolyte material, and in such a case, the polymer electrolyte material is present in both the composite anode layer and the composite cathode layer. The polymer electrolyte material can be a solid polymer electrolyte or a gel-type polymer electrolyte.

[0190] It will be understood that the steps of the processes herein are labeled for ease of reference. The steps can be performed in any order, with or without other intervening steps, provided they are not mutually incompatible. The descriptions of the particulate porous skeletons, silicon precursors, composite particles, electrodes, batteries, etc. below apply equally whether provided as products themselves or used as part of a process.

Examples

[0191] Example 1 Preparation and characterization of composite particles The particulate porous carbon skeletons C1 to C13 used in this example have the characteristics shown in Tables 1 and 2. The composite particles made from these skeletons have the characteristics shown in Table 3.

Table 1

Table 2

Table 3

[0192] Prior to silicon deposition, the particle size, surface area, and pore structure parameters of the carbon skeleton were measured. The total volume of micropores and mesopores was determined using nitrogen gas adsorption at 77 K and QSDFT, as described herein.

[0193] Silicon-carbon composite particles were prepared by arranging approximately 1.8 g of particulate porous framework having the properties described in Table 1 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 was purged under a nitrogen atmosphere for 30 minutes and then cooled to room temperature over several hours. Next, the atmosphere is gradually changed to air over two hours by switching the gas flow from nitrogen to air from the compressed air supply.

[0194] 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 was collected at 1-second intervals. The formula defined above is used to calculate the surface silicon (Y) value.

[0195] Using each carbon framework, a series of composite particle samples with varying amounts of deposited silicon were prepared. The average surface silicon for each framework was calculated from the TGA curves of each sample in that series of frameworks and is shown in Table 2. Figure 1 shows the average surface silicon of composite particles prepared from each porous carbon framework plotted against VP07 measured on the framework before silicon deposition. It is found that an increase in average surface silicon is achieved within a specific limit of VP07. We previously showed that higher surface silicon levels are associated with improved reversible capacity retention across multiple charge / discharge cycles. Figure 2 shows the average surface silicon of composite particles prepared from each porous carbon framework plotted against VP20-VP5 measured on the framework before silicon deposition. Further improvements in average surface silicon are achieved within a specific limit of VP20-VP5.

[0196] The surface area of ​​each sample in a series of skeletons was plotted against the amount of deposited silicon determined by TGA. It was found that the amount of silicon was inversely proportional to the surface area. The amount of silicon when the theoretical surface area is zero was extrapolated from the data points and is called the maximum silicon content. The maximum silicon content indicates the maximum amount of silicon that can be deposited within the pores of the skeleton before excessive deposition occurs on the outer surface of the skeleton. It is considered more advantageous for silicon to be deposited within pores where expansion and contraction can be absorbed by the skeleton, rather than on the surface. Therefore, as the maximum silicon content increases, the energy density of the composite particles increases by increasing the amount of silicon deposited within the pores of the skeleton without the potentially harmful presence of silicon deposited on the outer surface of the skeleton. Figure 3 shows the maximum silicon content of composite particles made from each skeleton plotted against VP07 measured on the skeleton before silicon deposition. When the VP07 value was less than 40%, consistently high maximum silicon content was observed.

[0197] Therefore, a framework with optimized pore volume and pore diameters of 0.7 nm or less enables the formation of composite particles with advantageous properties for use as electroactive materials in lithium-ion batteries, including a good balance between average surface silicon and maximum silicon content.

[0198] Example 2 Preparation and characterization of particulate porous skeletons The following examples illustrate the preparation of a particulate porous framework with a controlled pore structure.

[0199] All synthetic activated carbons reported below were prepared from a mixture of novolac resin and 11% hexamethylenetetramine powder (Bakelite PF 6705 FP) purchased from Hexion GmbH. This starting material was crosslinked at 150°C for 1 hour. The solid blocks of crosslinked material were then broken into 2-3 cm pieces and subsequently ground to approximately 100 μm particles. This cured resin powder was carbonized at 800°C for 10 minutes under a nitrogen flow of 1 L / min. The carbon yield obtained from this precursor was 57-59%. Coconut shell raw materials were carbonized in a similar temperature range (700-1000°C), but the carbon yield was lower (typically 20-30% w / w). After carbonization, the carbon was ball-milled to a particle size of 3-4 μm, and the resulting carbon material was 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 the total pore volume per 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 in laboratory-scale synthesis is typically 6–9 hours, depending on the type and amount of carbon to be activated, the steam flow rate, and the type of furnace used. In yet another example, the ratio of KOH to carbon carbide raw materials is 4:1, with KOH used for activation and then washed away after activation. [Table 4]

[0200] The results in the table show that VP07 can be adjusted by combinations of activation chemistry, activation conditions, and carbon raw materials. In particular, CO2 activation of synthetic raw materials can enhance VP07. Steam activation of biomass tends to widen pores and lower VP07 for the same pore volume. Chemical activation can also be used to achieve intermediate or high values ​​of VP07 in a similar manner to CO2 activation. VP07 can be manipulated while maintaining desirable values ​​of VP20-VP5.

[0201] Therefore, by using different scaffold chemistry and employing schemes that manipulate the mesopore size distribution and volume fraction using ethylene glycol as a cosolvent, the VP20-VP5 parameters can be modified while maintaining the desired value of VP07. An example of a procedure for manipulating the VP20-VP5 parameters is as follows: i. Provide novolac resin + hexamine. ii. Dissolve in a pore-forming agent (ethylene glycol) iii. Cure at 150°C for 1 hour. iv. Wash with hot water and dry. It carbonizes at 800°C. vi. Activate to different levels [Table 5]

[0202] Samples 8, 10, and 11 were prepared with the same initial formulation, which involved mixing 100 g of Novalac phenol resin and hexamine with 150 g of ethylene glycol. Sample 9 contained the same amounts of resin and hexamine, but less ethylene glycol (100 g). The mixtures were cured in an oven in air at 150°C for 1 hour, with the heating lamp increasing at 1°C / min and held at 100°C for 1 hour.

[0203] After curing, the samples were pulverized and granulated, and then the ethylene glycol was washed off with warm deionized water. They were then dried overnight at 90°C and carbonized at 800°C under a 1°C / min lamp with a 1 L / min nitrogen stream, activating samples 8, 10, and 11 to different levels. The carbonized material was then ball-milled at 300 rpm for 6 hours. Sample 9 was further activated at 950°C for approximately 3 hours under CO2 until the desired total pore volume was reached. Smaller amounts of pore-forming agent may be used to further reduce VP20-VP5.

[0204] Example 3 Preparation and characterization of composite particles The particulate porous carbon skeletons C14-C18 used in this example have the properties shown in Tables 6 and 7. The composite particles prepared from these skeletons have the properties shown in Table 8. [Table 6] [Table 7] [Table 8]

[0205] Before depositing silicon, the particle size, surface area, and pore structure parameters of the carbon skeleton were measured.

[0206] 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 6 and 7 were weighed and placed in the reactor chamber, then sealed, deactivated, and pressure tested using nitrogen gas. Next, the reactor was heated to a temperature of 320-350°C while 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, increasing the air concentration in nitrogen at 150°C, 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.

[0207] 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 C14 to C18 indicates that sufficient silicon has been deposited for the composite particles to be used as an anode material for lithium-ion batteries.

[0208] 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 was collected at 1-second intervals. The formula defined above is used to calculate the surface silicon (Y) value.

[0209] Figures 4 and 5 show the surface silicon of composite particles prepared from porous carbon skeletons, plotted against VP07 and VP20-VP5 measured on the skeleton before silicon deposition, respectively. Advantageously, high values ​​are observed for composite particles prepared from C14-C17.

[0210] Example 4 Preparation and characterization of composite particles The particulate porous carbon skeletons C19-C27 used in this example have the properties shown in Tables 9 and 10. The composite particles prepared from these skeletons have the properties shown in Table 11. [Table 9] [Table 10] [Table 11]

[0211] Before depositing silicon, the particle size, surface area, and pore structure parameters of the carbon skeleton were measured.

[0212] Silicon-carbon composite particles were prepared and characterized using the same procedure as in Example 3.

[0213] Figures 6 and 7 show the surface silicon of composite particles prepared from porous carbon skeletons, plotted against VP07 and VP20-VP5 measured on the skeleton before silicon deposition, respectively. Advantageously, high values ​​are observed in composite particles prepared from C19-C24.

Claims

1. Composite particles for use as an electroactive material for metal ion batteries, wherein the composite particles are A particulate porous framework containing micropores and optionally mesopores, The particulate porous framework comprises electroactive material domains located within the pores, P1 is cm ３ This is the total volume of micropores and mesopores in the particulate porous framework, expressed as / g, where P1 is at least 0.

35. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP07 is in the range of 5.1 to 40%. P1 and VP07 are the composite particles, measured by nitrogen gas adsorption.

2. The composite particles according to claim 1, wherein VP07 is in the range of 5.5 to 35%, or 7 to 30%, or 10 to 27%, or 15 to 25%.

3. The volume of the micropores in the particulate porous framework is at least 0.3 cm³. ３ / g, or at least 0.4cm ３ / g, or at least 0.5cm ３ / g, or at least 0.6cm ３ A composite particle according to any of the prior claims, wherein the particle size is / g.

4. The composite particle according to any of the prior claims, wherein VP1 is the volume of pores with a diameter of 1.0 nm or less in the particulate porous framework, expressed as a percentage of P1 measured by nitrogen gas adsorption, and VP1 is at least 1.5 × VP07 or at least 2 × VP07.

5. The composite particle according to any of the prior claims, wherein VP2 is the volume of pores with a diameter of 2.0 nm or less in the particulate porous framework, expressed as a percentage of P1 measured by nitrogen gas adsorption, and VP2 is at least 2.5 × VP07, or at least 3 × VP07, or at least 4 × VP07.

6. The composite particle according to any of the prior claims, wherein VP2 is the volume of pores with a diameter of 2.0 nm or less in the particulate porous framework, expressed as a percentage of P1 measured by nitrogen gas adsorption, and VP2 is at least 20%, at least 50%, at least 55%, or at least 60%, at least 70%, at least 80%, or at least 85%.

7. The composite particle according to any one of claims 1 to 5, wherein VP2 is the volume of pores with a diameter of 2.0 nm or less in the particulate porous framework, expressed as a percentage of P1 measured by nitrogen gas adsorption, and VP2 is less than 50%, or 45% or less, or 40% or less.

8. The composite particle according to any of the prior claims, wherein VP5 is the volume of pores with a diameter of 5.0 nm or less in the particulate porous framework, expressed as a percentage of P1 measured by nitrogen gas adsorption, and VP5 is at least 55%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 92%, or at least 93%.

9. The volume of pores with a diameter of 0.7 nm or less in the particulate porous framework is at least 0.05 cm³. ３ / g, or 0.08-0.5cm ３ / g, or 0.1-0.3cm ３ A composite particle according to any of the prior claims, wherein the particle size is / g.

10. The composite particle according to any of the prior claims, wherein VP20 is the pore volume of the particulate porous framework with a pore diameter of 20.0 nm or less, expressed as a percentage of P1, and VP20 is at least 80%, or at least 90%, or at least 95%, or at least 97%, or at least 98%, and VP20 is measured by nitrogen gas adsorption.

11. The composite particle according to any of the prior claims, wherein VP20 and VP5 are the volumes of pores in the particulate porous framework having pore diameters of 20.0 nm or less and 5.0 nm or less, respectively, expressed as a percentage of P1, VP20-VP5 is less than 20%, or less than 15%, or less than 12%, or less than 10%, or less than 9%, and optionally at least 0.5%, or at least 1%, or at least 2%, and VP20 and VP5 are measured by nitrogen gas adsorption.

12. The composite particle according to any of the prior claims, wherein VP10 is the volume of pores with a diameter of 10.0 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP10 is at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 97%, and VP10 is measured by nitrogen gas adsorption.

13. The composite particle according to any of the prior claims, wherein P1 is 0.4 to 1.8, or 0.5 to 1.6, or 0.6 to 1.

2.

14. P2 is cm ３ / g, which is the total volume of pores in the particulate porous skeleton with a diameter in the range of more than 50 to 100 nm, and P2 is less than 0.2 × P1, or less than 0.05 × P1, or less than 0.005 × P1, The composite particles according to any one of the preceding claims.

15. P2 is cm ３ The composite particle according to any of the prior claims, wherein P2 is the total volume of the pores in the particulate porous framework having a diameter in the range of more than 50 to 100 nm, expressed as g / g, and P2 is less than 15%, less than 10%, less than 8%, or less than 5% of the total volume of micropores, mesopores, and pores having a diameter in the range of more than 50 to 100 nm.

16. The particulate porous framework has a bimodal or multimodal pore size distribution, as described in any of the prior claims, as a composite particle.

17. The composite particles, when measured by laser diffraction, have a diameter of 100 μm or less, or 30 μm or less, or 1 to 30 μm, or 1 to 20 μm, or 2 to 8 μm. ５０ A composite particle having a particle size, as described in any of the prior claims.

18. When the composite particles are measured by laser diffraction, the particle size distribution span (D ９８ -D １ ) / D ５０ A composite particle according to any of the prior claims, wherein the ratio is less than 2.

19. The particulate porous framework has PD of 25 nm or less, or 1 to 20 nm, or 1.5 to 10 nm, or 2 to 9 nm. ９０ Having a pore size, the PD ９０ The composite particle according to any of the prior claims, wherein the pore diameter is such that, below this pore diameter, 90% of the total volume of the micropores and mesopores, as measured by nitrogen gas adsorption, is present.

20. The particulate porous framework has PD of 4 nm or less, or 3 nm or less, or 1 to 2.5 nm. ５０ Having a pore size, the PD ５０ The composite particle according to any of the prior claims, wherein the pore diameter is such that, below this pore diameter, 50% of the total volume of the micropores and mesopores, as measured by nitrogen gas adsorption, is present.

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

22. The particulate porous framework is formed from 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, or the particulate porous framework is formed from titanium nitride, silicon oxycarbide, or boron nitride, according to any of the prior claims.

23. The composite particle according to any one of claims 1 to 21, wherein the particulate porous skeleton is a particulate porous carbon skeleton.

24. When the particulate porous carbon skeleton is measured by Raman spectroscopy, the relative intensity ratio of the D peak to the G peak (I Ｄ / I Ｇ The composite particle according to claim 23, wherein the ratio is 0.6 or greater, or 0.8 or greater, or 1 or greater, or 1.05 or greater, and / or 2.0 or less, or 1.8 or less.

25. The composite particle according to any of the prior claims, wherein the particulate porous skeleton is formed from pyrolytic carbon, optionally pyrolytic carbon derived from a plant source, or pyrolytic pitch, or pyrolytic polymer, or pyrolytic resin.

26. The electroactive material is selected from silicon, tin, germanium, aluminum, and mixtures and alloys thereof, or the electroactive material is silicon, according to any of the prior claims, the composite particle.

27. A composite particle according to any of the prior claims, comprising 20 to 80% by weight of the electroactive material, or 30 to 70% by weight of the electroactive material, or 40 to 60% by weight of the electroactive material.

28. The composite particle according to any of the prior claims, wherein the electroactive material is silicon, and as determined by thermogravimetric analysis (TGA), at least 10% by weight, or at least 20% 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.

29. The composite particles according to any of the prior claims, wherein the electroactive material is silicon, and 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.

30. The composite particle according to any of the prior claims, wherein at least 70% by weight, 80% by weight, 85% by weight, 90% by weight, 95% by weight, or 98% by weight of the electroactive material in the composite particle is located within the internal pore volume of the particulate porous framework.

31. The composite particle according to any of the prior claims, wherein the nitrogen-accessible pore volume of the composite particle is less than 0.05 × P1.

32. The total volume of the micropores and mesopores in the composite particles is 0.03 cm³. ３ Less than 0.01 cm / g or 0.01 cm ３ A composite particle according to any of the prior claims, wherein the amount is less than / g.

33. The aforementioned composite particles are 50 m ２ Less than 1g, or 30mg ２ Less than 20m / g ２ Less than 15mg / g, or 15mg ２ Less than 10mg / g, or 10mg ２ A composite particle according to any of the prior claims, having a BET surface area of ​​less than 1g.

34. An electrode comprising composite particles as described in any of the prior claims.

35. A rechargeable metal-ion battery comprising the electrode described in claim 34.

36. A process for preparing composite particles according to any one of claims 1 to 33, wherein the process is: (a) the step of providing a particulate porous skeleton according to any one of claims 1 to 33, (b) The process comprising the step of depositing electroactive material domains in the pores of the particulate porous framework.

37. The process according to claim 36, wherein step (b) involves contacting the particulate porous framework with an electroactive material precursor at a temperature effective for depositing electroactive material domains in the pores of the particulate porous framework.

38. The process according to claim 37, wherein the electroactive material precursor is a gas.

39. The electroactive material precursor is a silicon precursor, and optionally the 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 ) are selected, and optionally, the silicon precursor is silane (SiH ４ The process according to claim 38, wherein the process is as follows:

40. Step (b) is performed at a pressure of at least 150 kPa, or at least 200 kPa, optionally, 5000 kPa or less, according to any one of claims 36 to 39.

41. It is a process, (a1) Providing a group of one or more particulate porous frameworks including micropores and optionally mesopores, (a2) A step of measuring the pore structure of each group, (a3) A step of accepting each group having an optimized pore structure and not accepting each group not having the optimized pore structure, wherein the optimized pore structure is P1 is cm ３ This is the total volume of micropores and mesopores in the particulate porous framework, expressed as / g, where P1 is at least 0.

35. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP07 is in the range of 5.1 to 40%. P1 and VP07 are measured by nitrogen gas adsorption, in the acceptance and non-acceptance steps, (b) The process comprising the step of depositing electroactive material domains in the pores of an accepted collection of particulate porous frameworks.

42. The process according to claim 41, wherein step (a1) provides at least two groups, of which at least one is optionally rejected in step (a3).

43. (a4) Providing an industrial-scale collection of accepted particulate porous skeletons, wherein the industrial-scale collection comprises at least 100 kg or at least 1,000 kg of the accepted particulate porous skeletons, (b) The process according to claim 41 or 42, comprising the step of depositing electroactive material domains within the pores of an industrial-scale collection of the accepted particulate porous framework.

44. A particulate porous framework comprising micropores and optionally mesopores, P1 is cm ３ This is the total volume of micropores and mesopores in the particulate porous framework, expressed as / g, where P1 is at least 0.

35. VP07 is the volume of pores with a diameter of 0.7 nm or less in the particulate porous framework, expressed as a percentage of P1, and VP07 is in the range of 5.1 to 40%. P1 and VP07 are the particulate porous framework, measured by nitrogen gas adsorption.

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