Composite particles

Abstract

Provided is a composite particle for use as an electroactive material for a metal ion battery, the composite particle comprising: a particulate porous framework comprising micropores and optionally mesopores; and a domain of electroactive material located within the pores of the particulate porous frame; wherein: 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 volume of pores having a pore diameter of 0.7 nm or less in the particulate porous framework, expressed in percentage of P1, where VP07 is in the range of 5.1-40%; wherein P1 and VP07 are measured by a nitrogen adsorption method.

Description

Technical Field

[0001] This invention relates to particulate porous frameworks with optimized pore structures. These frameworks are particularly suitable for preparing composite particles for use as electroactive materials in metal-ion batteries, such as lithium-ion batteries. Background Technology

[0002] A lithium-ion battery (LIB) typically comprises an anode, a cathode, and a lithium-containing electrolyte. The anode typically includes a metal current collector with a layer of electroactive material, defined herein as a material capable of inserting and releasing lithium ions during battery charging and discharging. When the LIB is charged, lithium ions migrate from the cathode to the anode via the electrolyte and insert into the electroactive material of the anode in the form of intercalated lithium atoms. Therefore, as used herein, the terms “cathode” and “anode” refer to the state in which the battery is connected to a load, such that the anode is the negative electrode. The term “battery” as used herein refers both to a device containing a single cell (such as a Li-ion cell or a Na-ion cell) and to a device containing multiple connected cells.

[0003] Conventional lithium-ion batteries (LIBs) use graphite as the anode electroactive material. Graphite anodes can accommodate a maximum of one lithium atom for every six carbon atoms, resulting in a maximum theoretical specific capacity of 372 mAh / g in lithium-ion batteries, while the actual capacity is slightly lower (approximately 340 to 360 mAh / g). Silicon is a promising alternative to graphite due to its very high lithium capacity (e.g., see Insertion Electrode Materials for Rechargeable Lithium Batteries, Winter, M et al., Adv. Mater. 1998, 10, No. 10). The theoretical maximum specific capacity of silicon in lithium-ion batteries is approximately 3,600 mAh / g (based on Li). 15 (Si4). However, such a high lithium-to-silicon intercalation ratio causes the silicon material to expand by up to 400% of its original volume. Repeated charge-discharge cycles impose significant mechanical stress on the silicon material, leading to cracking and structural failure. Furthermore, anodic charging in LIBs results in the formation of a solid electrolyte interface (SEI) layer. This SEI layer is ionicly conductive but insulating, formed during the initial charging phase when the electrolyte undergoes reductive decomposition on the exposed electrode surface. In graphite anodes, this SEI layer is relatively stable during subsequent charge / discharge cycles. However, the expansion and contraction of the silicon anode causes the SEI layer to crack and peel off, exposing fresh silicon surfaces, leading to further electrolyte decomposition, increased SEI layer thickness, and irreversible lithium consumption. These failure mechanisms collectively result in unacceptable electrochemical capacity loss during continuous charge-discharge cycles.

[0004] One approach reported by the inventors to address these problems is the development of a class of electroactive materials with composite structures, wherein the electroactive material (such as silicon) is deposited into a pore network of highly porous particles (e.g., porous carbon materials) with a precisely controlled pore size distribution. For example, WO2020 / 095067, WO2020 / 128495, and WO2022 / 029422 report that the improved electrochemical performance of these materials can be attributed to the way the electroactive material forms small domains of a few nanometers or smaller within the pore network of porous particles, thus acting as a framework for the composite particles. It is believed that fine electroactive structures have lower resistance to elastic deformation and higher resistance to fracture than larger electroactive structures, and therefore enable lithiation and delithiation without generating excessive structural stress. Consequently, the electroactive materials exhibit good reversible capacity retention over multiple charge-discharge cycles. By controlling the silicon loading within the porous particle framework, such that silicon occupies only a portion of the pore volume in the uncharged state, the unoccupied pore volume within the porous particle framework can accommodate a significant amount of silicon expansion internally. Excessive expansion is limited by the particulate framework. Furthermore, since only a small area of ​​the electroactive material surface is in contact with the electrolyte, SEI formation is essentially prevented.

[0005] However, various raw materials and synthetic methods exist for obtaining porous materials that can be used as frameworks for this type of composite particles. Although the inventors have reported desirable pore size distribution parameters for the frameworks, it remains difficult to determine which porous materials are expected to provide particularly advantageous frameworks for preparing composite particles without the time-consuming process of preparing numerous batches of composite particles and performing electrochemical testing on each. Therefore, further optimization of the pore structure of the frameworks is needed to further improve the properties of the composite particles thus prepared. Furthermore, an effective and reliable assessment is still needed to determine whether new sources of porous frameworks are suitable for preparing composite particles with desirable properties for downstream applications in LIBs. Summary of the Invention

[0006] This invention provides composite particles for use as electroactive materials in metal-ion batteries, the composite particles comprising:

[0007] Including granular porous frameworks with micropores and optionally mesopores; and

[0008] Electroactive material domains located within the pores of a granular porous framework; wherein:

[0009] P1 is the total volume of micropores and mesopores in the granular porous framework, expressed in cm. 3 / g indicates that P1 is at least 0.35; and

[0010] VP07 is the volume of pores with a pore diameter of 0.7 nm or smaller in the granular porous framework, expressed as a percentage of P1, wherein VP07 is in the range of 5.1-40%;

[0011] P1 and VP07 were measured by nitrogen adsorption method.

[0012] The inventors have discovered that pores with a diameter of 0.7 nm or smaller (i.e., 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. An electrode comprising the composite particles, a rechargeable metal-ion battery comprising the electrode, and a process for manufacturing the electrode are also provided.

[0013] The present invention also provides a process for preparing composite particles, the process comprising the steps of: (a) providing a particulate porous framework as defined herein; and (b) depositing electroactive material domains in the pores of the particulate porous framework.

[0014] The present invention also provides a process comprising the following steps:

[0015] (a1) Provide one or more groups of granular porous frameworks comprising micropores and optionally mesopores;

[0016] (a2) Measure the pore structure of each population;

[0017] (a3) Accept each group having an optimized pore structure and reject each group not having the optimized pore structure, wherein in the optimized pore structure:

[0018] P1 is the total volume of micropores and mesopores in the granular porous framework, expressed in cm. 3 / g indicates that P1 is at least 0.35; and

[0019] VP07 is the volume of pores with a pore diameter of 0.7 nm or smaller in the granular porous framework, expressed as a percentage of P1, wherein VP07 is in the range of 5.1-40%;

[0020] P1 and VP07 were measured by nitrogen adsorption method;

[0021] (b) Depositing electroactive material domains into the pores of a recognized population of particulate porous frameworks.

[0022] In this process, the inventors’ understanding of how to select porous frames with optimized pore structures is advantageously used to screen a variety of frame sources and select those frames that are expected to provide composite particles with desirable properties. Attached Figure Description

[0023] Figure 1 The average surface silicon and VPO7 values ​​of the composite particles prepared in Example 1 are shown.

[0024] Figure 2 The average surface silicon and VP20-VP5 values ​​of the composite particles prepared in Example 1 are shown.

[0025] Figure 3 The maximum silicon and VPO7 values ​​of the composite particles prepared in Example 1 are shown.

[0026] Figure 4 The surface silicon and VPO7 values ​​of the composite particles prepared in Example 3 are shown.

[0027] Figure 5 The surface silicon and VP20-VP5 values ​​of the composite particles prepared in Example 3 are shown.

[0028] Figure 6 The surface silicon and VPO7 values ​​of the composite particles prepared in Example 4 are shown.

[0029] Figure 7 The surface silicon and VP20-VP5 values ​​of the composite particles prepared in Example 4 are shown. Detailed Implementation

[0030] The inventors determined the optimized pore structure based on the following: electroactive materials, such as silicon, can be efficiently deposited within a porous framework using a chemical vapor infiltration (CVI) process. This is a variant of chemical vapor deposition (CVD), in which the decomposition surface is located within the pores of the porous framework. For a silicon precursor to decompose into silicon, the precursor must be able to enter the pores of the framework and reach a suitable decomposition site. A desirable framework typically comprises a three-dimensionally interconnected network of open pores, including micropores and optionally mesopores, and optionally a small number of macropores. According to conventional IUPAC terminology, the term "micropore" is used herein to refer to pores with a diameter less than 2 nm, the term "mesopore" is used herein to refer to pores with a diameter between 2 and 50 nm, and the term "macropore" is used herein to refer to pores with a diameter greater than 50 nm. As used herein, P1 is the total volume of micropores and mesopores, in cm⁻¹. 3 / g represents the volume of pores with a diameter of 0.7 nm or smaller, expressed as a percentage of P1. In the literature, pores with a diameter less than 0.7 nm are usually referred to as "micropores".

[0031] By limiting VP07 to 5.1-40%, a framework with an optimized pore structure is provided. This optimized pore structure facilitates the fabrication of composite particles with desirable properties for use as electroactive materials. This is surprising because pores with diameters of 0.7 nm or smaller (i.e., pores at the smaller end of the pore diameter distribution) have not previously been considered to be associated with the properties of electroactive materials. Given that 0.7 nm is less than twice the size of a typical silicon precursor used in CVI for depositing silicon into a particulate porous framework (which has a diameter of about 0.4-0.6 nm), it is expected that most of these small pores will be capped after deposition and at least partially unfilled, and thus ignored when selecting a porous framework. However, the inventors have realized that some pore volume of the framework is formed by pores with diameters of 0.7 nm or smaller, which is an advantage. The presence of these pores (which may remain at least partially unfilled after silicon deposition) improves the elastic response of the composite under large strains (e.g., during lithiation and delithiation), which helps to minimize the outward expansion of the scale and significantly reduce the fracture of the composite. However, if VP07 is too high, it is believed that the tortuosity and narrowness will increase, and the BET surface area of ​​the framework will also increase, making it more difficult to control the deposition of electroactive materials in a desirable form within the framework.

[0032] 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 the framework of VP07 within these ranges allows for the preparation of composite particles with a good balance between average surface silicon and silicon content, as observed in the examples.

[0033] VP07 is a representation of the total volume of micropores and mesopores in a granular porous framework. However, for some applications, it is advantageous to specify a minimum absolute value of the volume of pores with a pore diameter of 0.7 nm or smaller. Therefore, the volume of pores with a pore diameter of 0.7 nm or smaller in a granular porous framework can be at least 0.05 cm³. 3 / g, preferably 0.08-0.5 cm 3 / g, most preferably 0.1-0.3 cm 3 / g; when measured by nitrogen adsorption method.

[0034] In the absence of any indication to the contrary, composite particles (e.g., P1, VP07, VP1, PD) n The pore structure (such as pore diameter) is defined by the pore structure of a separately measured granular porous framework, i.e., measured in the absence of any electroactive material (or any other material) occupying the pores of the granular porous framework.

[0035] VP1, VP2, and VP5 are the volumes of pores with diameters of 1.0 nm or less, 2.0 nm or less, and 5.0 nm or less in the granular porous framework, respectively, expressed as a percentage of P1. VP1, VP2, and VP5 are measured by nitrogen 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%.

[0036] Preferably, VP2 is at least 20%. For some applications, VP2 is at least 40%, at least 50%, at least 55%, or at least 60%, or at least 70%, or at least 80%, or at least 85%, meaning that micropores constitute the majority of the volume of micropores and mesopores. Alternatively, VP2 is less than 50%, or no more than 45%, or no more than 40%, meaning that mesopores constitute the majority of the volume of micropores and mesopores.

[0037] VP2 may be less than 99%, or less than 98%, or less than 95%, or preferably less than 90%, for example, 40-90%.

[0038] 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%.

[0039] The micropore volume is preferably at least 0.3 cm³. 3 / g. Based on the inventors' identified desired value for VP07, it has been found that the micropore volume is at least 0.3 cm³. 3 The granular porous framework, with a density of / g, provides a further optimized pore structure for depositing electroactive materials such as silicon. The micropore volume can be at least 0.4 cm³. 3 / g, or at least 0.5 cm 3 / g, or at least 0.6 cm 3 / g.

[0040] The properties of the framework and the resulting composite particles can be further refined by controlling the pore volume at larger pore sizes. VP20 and VP10 are defined as the volumes of pores with diameters of 20.0 nm or less and 10.0 nm or less in the particulate porous framework, respectively, expressed as a percentage of P1. VP10 and VP20 are measured by nitrogen 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%.

[0041] VP20-VP5 represents the pore volume in a particulate porous framework with a pore diameter greater than 5.0 nm to up to 20.0 nm (inclusive), expressed as a percentage of P1. VP20-VP5 can be less than 20%, less than 15%, preferably less than 12%, preferably less than 10%, or more preferably less than 9%. Optionally, VP20-VP5 is at least 0.5%, at least 1%, or at least 2%. VP20-VP5 can be 0.5-20%, 0.5-15%, or 1-12%, or 2-10%, or 2-9%, or 3-9%. It has been found that particulate porous frameworks with VP20-VP5 values ​​in these ranges provide further improvements in surface silicon.

[0042] VP20-VP2 can be at least 45%, or at least 50%, or at least 55%.

[0043] Particulate porous frameworks are characterized by P1, the total volume of micropores and mesopores (i.e., the total pore volume with a pore diameter ranging from 0 to 50 nm). Typically, particulate porous frameworks include both micropores and mesopores. However, the use of particulate porous frameworks that include micropores but not mesopores is not excluded. The P1 of the 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 particles with higher porosity may be advantageous because it allows for the containment of a larger amount of electroactive material within the pore volume.

[0044] The internal pore volume of the granular porous framework is suitably limited to a value at which the increased fragility of the framework structure outweighs the advantages of the increased pore volume (thus accommodating a larger amount of electroactive material). The P1 value of the granular porous framework may be no more than 2.5, or no more than 2.0, or no more than 1.8, or no more than 1.7, or no more than 1.6, or no more than 1.55, or no more than 1.5, or no more than 1.45, or no more than 1.4, or no more than 1.35, or no more than 1.3, or no more than 1.25, or no more than 1.2, or no more than 1.1.

[0045] Preferably, the P1 of the granular porous framework is in the range of 0.4 to 1.8, 0.5 to 1.6, or most preferably 0.6 to 1.2.

[0046] The total volume of micropores and mesopores, and the pore size distribution of micropores and mesopores (including P1, VP07, VP1, VP2, VP5, VP10, VP20 and PD as defined in this paper). n The pore diameter parameter was obtained using nitrogen adsorption at 77 K and decreased to 10 K. -7 Under relative pressure p / p0, the porosity and pore size distribution of a material are determined using quenched solid density functional theory (QSDFT) according to standard methods, preferably as described in ISO 15901-2:2022. Nitrogen adsorption is a technique for characterizing the porosity and pore diameter distribution of a material by condensing a gas within the pores of a solid. As pressure increases, the gas first condenses in the pores with the smallest diameter, and the pressure continues to increase until a saturation point is reached, at which point all pores are filled with liquid. The nitrogen pressure is then gradually reduced to allow the liquid to evaporate from the system. Analysis of the adsorption and desorption isotherms and the hysteresis between them allows for the determination of pore volume and pore size distribution. Instruments suitable for measuring pore volume and pore size distribution by nitrogen adsorption include the ASAP 2020 Plus porosity analyzer from Micromeritics Instrument Corporation (USA) and the Autosorb IQ porosity analyzer from Quantachrome Instruments.

[0047] The porosity parameter of the granular porous framework mentioned in this article refers to the internal pore volume of the granular porous framework measured alone (i.e., in the absence of any electroactive material or other material occupying some or all of the pore volume).

[0048] Nitrogen adsorption is effective for measuring pore volume and pore size distribution of pores up to 50 nm in diameter, but it is less reliable for pores with larger diameters. Therefore, for the purposes of this invention, nitrogen adsorption is only used to determine the pore volume and pore size distribution of pores up to 50 nm in diameter (including 50 nm) (i.e., only for micropores and mesopores). Similarly, PD... n The value is determined only relative to the total volume of micropores and mesopores.

[0049] Due to the limitations of available analytical techniques, it is impossible to measure the pore volume and pore size distribution across the entire micropore, mesopore, and macropore range using a single technique. In the case of granular porous frameworks including macropores, the volume of pores with diameters ranging from greater than 50 nm to up to 100 nm can be measured by mercury porosimetry, and preferably not exceeding 0.3 cm³. 3 / g, or no more than 0.2 cm 3 / g, or no more than 0.1 cm 3 / g, or no more than 0.05 cm 3 / g. A small portion of the macropores can be used to facilitate the entry of electrolytes into the porous network, but the advantages of this invention are primarily obtained by accommodating electroactive materials in micropores and optionally mesopores.

[0050] Any pore volume with a pore size of 50 nm or less measured by mercury porosimetry is ignored (as explained above, nitrogen adsorption is used to characterize mesopores and micropores). For the purposes of this invention, pore volumes above 100 nm measured by mercury porosimetry are assumed to be interparticle porosity and are also ignored.

[0051] Mercury intrusion porosimetry (MIP) is a technique for characterizing the porosity and pore diameter distribution of a material by applying varying levels of pressure to a sample immersed in mercury. The pressure required to penetrate the pores of the sample is inversely proportional to the pore size. The values ​​obtained by MIP as reported herein are based on ASTM UOP578-11, where the surface tension γ of mercury is taken as 480 mN / m at room temperature and the contact angle φ as 140°. The density of mercury at room temperature is taken as 13.5462 g / cm³. 3 Many high-precision mercury porosimetry instruments are commercially available, such as the AutoPore IV series automatic mercury porosimetry instrument from Micromeritics Instrument Corporation. For a complete overview of mercury porosimetry, see PA Webb and C. Orr, "Analytical Methods in Fine Particle Technology, 1997, Micromeritics Instrument Corporation, ISBN 0-9656783-0".

[0052] It should be understood that intrusion techniques (such as gas adsorption and mercury porosimetry) are only effective in determining the pore volume of pores through which nitrogen or mercury can enter from the outside of the granular porous framework. The porosity values ​​specified herein should be understood as the volume of what is referred to as open pores, i.e., pores through which fluid can enter from the outside of the granular porous framework. Completely closed pores that cannot be identified by nitrogen adsorption or mercury porosimetry should not be considered when determining porosity values ​​herein. Similarly, any pore volume located in pores that are small enough to be below the detection limit of nitrogen adsorption is also excluded.

[0053] The pore structure of a particulate porous framework can include a unimodal, bimodal, or multimodal pore size distribution. As used herein, the term "pore size distribution" refers to the distribution of pore sizes relative to the cumulative total internal pore volume of the particulate porous framework. Bimodal or multimodal pore size distributions are preferred because the close proximity between micropores and larger diameter pores provides the advantage of efficient ion migration through the porous network to the electroactive material.

[0054] The general term "PD" in this article n "Pore diameter" refers to the nth percentile pore diameter based on the total volume of micropores and mesopores. For example, as used herein, the term "PD" is... 50 "Pore diameter" refers to the pore diameter that accounts for less than 50% of the total volume of micropores and mesopores. To avoid ambiguity and for the purpose of determining PD... n For the purpose of this study, no large pore volume (pore diameter greater than 50 nm) is considered. The granular porous framework preferably has a PD of no more than 25 nm, or 1-20 nm, or 1.5-10 nm, or 2-9 nm. 90 Pore ​​diameter. The granular porous framework preferably has a PD of no more than 4 nm, or no more than 3 nm, or 1-2.5 nm. 50 Pore ​​diameter.

[0055] The modal pore diameter of the micropores and mesopores in the granular porous framework can be ≥0.50 nm, preferably ≥0.60 nm.

[0056] In the case of granular porous frameworks including macropores, the volume of pores in the range of 50 nm to up to 100 nm can be referred to as P² cm⁻¹. 3 / g, and measured by mercury porosimetry. The volume of macropores (and the corresponding P2 value) is preferably smaller compared to the volume of micropores and mesopores (and the corresponding P1 value). Although a small fraction of macropores can be used to facilitate the entry of electrolytes into the porous network, the advantages of the present invention are primarily obtained by accommodating electroactive materials in micropores and smaller mesopores. Therefore, the P2 of the particulate porous framework preferably has a value of <0.2×P1, or <0.1×P1, or <0.05×P1, or <0.02×P1, or <0.01×P1, or <0.005×P1.

[0057] P2 can account for <15%, <10%, <8%, or <5% of the total volume of micropores, mesopores, and pores with diameters in the range of >50-100 nm.

[0058] Generally speaking, the D of composite particles 50 The particle size is no more than 100 μm, or preferably no more than 30 μm. Optionally, the D of the composite particles... 50The 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 no more than 25 μm, or no more than 20 μm, or no more than 18 μm, or no more than 15 μm, or no more than 12 μm, or no more than 10 μm, or no more than 8 μm.

[0059] 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. This is achieved by using D... 10 Maintaining the particle size at 0.5 μm or larger reduces the likelihood of undesirable aggregation of submicron particles and improves the dispersibility of the resulting composite particles.

[0060] 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 extremely small particles is reduced, thereby reducing the detrimental effects of high cohesion and surface area associated with extremely small particles.

[0061] 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.

[0062] D of composite particles 90 The particle size is preferably no more than 50 μm, or no more than 40 μm, or no more than 30 μm, or no more than 25 μm, or no more than 20 μm, or no more than 15 μm.

[0063] D of composite particles 98 The particle size is preferably no more than 35 μm, or no more than 30 μm, or no more than 25 μm, or no more than 20 μm, or no more than 15 μm. This is achieved by controlling D... 98 Particle size reduction reduces the presence of even a small number of excessively large particles remaining within the composite particle group, thereby reducing the adverse effects associated with excessively large particles on packing efficiency and non-uniformity in the electrode layer.

[0064] D of composite particles 100 The particle size is preferably no more than 40 μm.

[0065] The composite particles preferably have a narrow size distribution span. For example, the particle size distribution span (defined as (D...) 90 -D 10 ) / D 50The particle size distribution span is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, even more preferably 2 or less, and most preferably 1.5 or less. By maintaining a narrower size distribution span, it is easier to effectively fill the dense powder bed with particles. Particle size distribution span (D) 98 -D1) / D 50 Preferably less than 2. Maintain D 98 The close distribution between the D1 particle size and the composite particles is believed to facilitate the deposition of electroactive materials during the preparation of composite particles, thereby ensuring a uniform distribution of the frame in the reaction vessel typically used during manufacturing.

[0066] Particle size distribution can be controlled using known classification methods, such as dynamic air classification, hydroclassification, or gravity separation. Suitable classification equipment is a dynamic air classifier, such as the Alpine TTD ultrafine air classifier from Hosokawa Micron Powder Systems.

[0067] As used herein, the term "particle size" refers to the equivalent spherical diameter (esd), which is the diameter of a sphere having the same volume as a given particle, where particle volume should be understood to include the volume of any internal pores within the particle. As used herein, the term "D"... n "and "D n "Particle size" refers to the median particle size based on volume, which is the diameter that is less than n% of the diameter found in the particle population by volume.

[0068] Particle size and particle size distribution can be determined using laser diffraction techniques according to ISO 13320:2009. The principle behind laser diffraction is that particles scatter light at angles varying depending on their size, and the aggregate of particles produces a pattern of scattered light, defined by intensity and angle that are relevant to the particle size distribution. Many laser diffraction instruments are commercially available for the rapid and reliable determination of particle size distribution. Unless otherwise stated, all particle size distribution measurements specified or reported herein are performed by Malvern Instruments. TM Regular Malvern Mastersizer TM Measured using a 3000 particle size analyzer. Perform the following operations using a Malvern Mastersizer. TM3000 Particle Size Analyzer: A helium-neon gas laser beam is projected through a transparent cell containing target particles suspended in an aqueous solution. The light illuminating the particles is scattered at an angle inversely proportional to the particle size, and a photodetector array measures the light intensity at several predetermined angles. A computer processes the measured intensities at different angles using standard theoretical principles to determine the particle size distribution. The laser diffraction values ​​reported herein were obtained using wet-dispersed particles in 2-propanol with the addition of 5% by volume of the surfactant SPAN. TM -40 (sorbitan monopalmitate). The refractive index of the granular porous framework was taken as 2.68 and the refractive index of the composite particles was taken as 3.50, and the dispersant index was taken as 1.378. The particle size distribution was calculated using the Mie scattering model.

[0069] The average sphericity of the composite particles (as defined herein) may be greater than 0.5. Preferably, their average sphericity is 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 average sphericity of the composite particles is 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 considered to contribute to the uniformity of deposition and to a denser packing in batch pressure reactors and when the final product is incorporated into the electrode.

[0070] High-precision two-dimensional projections of micron-sized particles can be obtained through scanning electron microscopy (SEM) or dynamic image analysis, where the shadows cast by the particles are recorded using a digital camera. The term "sphericity," as used herein, should be understood as the ratio of the particle's projected area (obtained from such imaging techniques) to the area of ​​a circle, where the particle's projection and the circle have the same circumference. Therefore, for a single particle, the sphericity S can be defined as:

[0071]

[0072] Where A m Let C be the measured area of ​​the particle projection. m The measured perimeter of the particle projection. The average sphericity S of the particle population used in this paper. av Defined as:

[0073]

[0074] Where n represents the number of particles in the population. The average sphericity of the particle population is preferably calculated by two-dimensional projection of at least 50 particles.

[0075] It is assumed that the particle size distribution of the granular porous framework will not be altered by 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 granular porous framework (e.g., D). 50 (such as sphericity).

[0076] The BET surface area of ​​the granular porous framework is preferably at least 750 m². 2 / g, more preferably at least 1,000 m 2 / g, or at least 1,100 m 2 / g, or at least 1,250 m 2 / g, or at least 1,500 m 2 / g. As used herein, the term "BET surface area" should be considered as the surface area per unit mass calculated by measuring the physical adsorption of gas molecules on a solid surface using the Brunauer-Emmett-Teller theory according to ISO 9277:2022. Preferably, the BET surface area of ​​the particulate porous framework is no more than 4,000 m². 2 / g, or no more than 3,500 m 2 / g, or no more than 3,250 m 2 / g, or no more than 3,000 m 2 / g, or no more than 2,500 m 2 / g, or no more than 2,000 m 2 / g. For example, the BET surface area of ​​granular porous frameworks can reach 100 m². 2 / g 10 to 4,000 m 2 / g, or 500 m 2 / g to 4,000 m 2 / g, or 750 m 2 / g to 3,500 m 2 / g, or 1,000 m 2 / g to 3,250 m 2 / g, or 1,000 m 2 / g to 3,000 m 2 / g, or 1,000 m 2 / g to 2,500 m 2 / g, or 1,000m 2 / g to 2,000 m 2 Within the range of / g.

[0077] The BET surface area of ​​the composite particles is preferably no more than 300 m². 2 / g, or no more than 250 m 2 / g, or no more than 200m2 / g, or no more than 150 m 2 / g, or no more than 100 m 2 / g, or no more than 80 mg 2 / g, or more preferably no more than 60 m 2 / g, or no more than 50 mg 2 / g, or no more than 40 mg 2 / g, or no more than 30 mg 2 / g, or no more than 25 mg 2 / g, or no more than 20 mg 2 / g, or no more than 15 mg 2 / g, or no more than 10 mg 2 / g, or no more than 5 mg 2 / g. Generally, a low BET surface area is preferred during the first charge-discharge cycle of the anode to minimize the formation of a solid electrolyte interphase (SEI) layer at the surface of the composite particles. However, an excessively low BET surface area leads to unacceptably low charge rates and capacities because most of the electroactive material cannot contact the metal ions in the surrounding electrolyte. The BET surface area is preferably at least 0.1 m² / g. 2 / g, or at least 1 m 2 / g, or at least 2 m 2 / g, or at least 5 mg 2 / g. For example, the BET surface area of ​​composite particles can range from 0.1 to 100 m². 2 / g, or 0.1 to 80 m 2 / g, or 0.5 to 60 m 2 / g, or 0.5 to 40 m 2 / g, or 1 to 30 m 2 / g, or 1 to 25 mg 2 / g, or 1 to 20m 2 / g, or 1 to 15 m 2 / g, or 2 to 10 mg 2 Within the range of / g.

[0078] The particle density of the composite particles is preferably at least 0.35, and preferably less than 3 g / cm³. 3 More preferably less than 2 g / cm 3 More preferably less than 1.5 g / cm 3 The most preferred value is less than 0.35 to 1.2 g / cm³. 3As used herein, the term "particle density" refers to the "apparent particle density" as measured by mercury intrusion spectroscopy (i.e., the mass of the particle divided by the particle volume, where the particle volume is considered as the sum of the volume of the solid material and the volume of any closed pores or blind pores ("blind pores" are pores too small to be measured by mercury intrusion spectroscopy)). Preferably, the particle density of the composite particles is at least 0.4 g / cm³. 3 or at least 0.45 g / cm 3 or at least 0.5 g / cm 3 or at least 0.55 g / cm 3 or at least 0.6 g / cm 3 or at least 0.65 g / cm 3 or at least 0.7 g / cm 3 Preferably, the particle density of the composite particles is no more than 1.15 g / cm³. 3 or not more than 1.1 g / cm 3 or not more than 1.05 g / cm 3 or not more than 1 g / cm 3 or not more than 0.95 g / cm 3 or no more than 0.9 g / cm 3 .

[0079] In one aspect, the present invention provides composite particles for use as electroactive materials in metal-ion batteries, the composite particles comprising:

[0080] Including granular porous frameworks with micropores and optionally mesopores; and

[0081] Electroactive material domains located within the pores of a granular porous framework; wherein:

[0082] P1 represents the total volume of micropores and mesopores in the granular porous framework, expressed in cm³. 3 / g represents, where P1 is 0.35-1.8; and

[0083] VP07 is the volume of pores with a pore diameter of 0.7 nm or smaller in the granular porous framework, expressed as a percentage of P1, wherein VP07 is in the range of 7-35%;

[0084] VP2 is the volume of pores with a pore diameter of 2.0 nm or smaller in the particulate porous framework, expressed as a percentage of P1, wherein VP2 is at least 20%;

[0085] VP10 is the volume of pores with a pore diameter of 10.0 nm or smaller in a particulate porous framework, expressed as a percentage of P1, wherein VP10 is at least 70%;

[0086] VP20 is the volume of pores with a pore diameter of 20.0 nm or smaller in a particulate porous framework, expressed as a percentage of P1, wherein VP20 is at least 80%;

[0087] VP5 is the volume of pores with a diameter of 5.0 nm or smaller in the granular porous framework, expressed as a percentage of P1; where VP20-VP5 is less than 15%.

[0088] P1, VP07, VP5, VP10 and VP20 were measured by nitrogen adsorption method;

[0089] Among them, the composite particles D 50 The particle size is no more than 30 μm, as measured by laser diffraction.

[0090] In one aspect, the present invention provides composite particles for use as electroactive materials in metal-ion batteries, the composite particles comprising:

[0091] Including granular porous frameworks with micropores and optionally mesopores; and

[0092] Electroactive material domains located within the pores of a granular porous framework; wherein:

[0093] P1 represents the total volume of micropores and mesopores in the granular porous framework, expressed in cm³. 3 / g represents, where P1 is 0.4-1.8; and

[0094] VP07 is the volume of pores with a diameter of 0.7 nm or smaller in a particulate porous framework, expressed as a percentage of P1, where VP07 is in the range of 10-30%.

[0095] VP2 is the volume of pores with a pore diameter of 2.0 nm or smaller in the particulate porous framework, expressed as a percentage of P1, wherein VP2 is at least 20%;

[0096] VP10 is the volume of pores with a pore diameter of 10.0 nm or smaller in a particulate porous framework, expressed as a percentage of P1, wherein VP10 is at least 70%;

[0097] VP20 is the volume of pores with a pore diameter of 20.0 nm or smaller in a particulate porous framework, expressed as a percentage of P1, wherein VP20 is at least 80%;

[0098] VP5 is the volume of pores with a diameter of 5.0 nm or smaller in the granular porous framework, expressed as a percentage of P1; where VP20-VP5 are 1-9%;

[0099] P1, VP07, VP5, VP10 and VP20 were measured by nitrogen adsorption method;

[0100] Among them, the composite particles D 98 The particle size is no more than 30 μm and the D1 particle size is at least 1 μm, as measured by laser diffraction.

[0101] In another aspect, the present invention provides composite particles for use as electroactive materials in metal-ion batteries, the composite particles comprising:

[0102] Including granular porous carbon frameworks with micropores and optionally mesopores; and

[0103] Silicon domains located within the pores of a granular porous carbon framework; wherein:

[0104] P1 is the total volume of micropores and mesopores in the granular porous carbon framework, expressed in cm. 3 / g represents, where P1 is 0.4-1.8; and

[0105] VP07 is the volume of pores with a diameter of 0.7 nm or smaller in a particulate porous carbon framework, expressed as a percentage of P1, where VP07 is in the range of 7-30%.

[0106] P1 and VP07 were measured by nitrogen adsorption method;

[0107] Among them, the composite particles D 50 The particle size is no more than 30 μm, as measured by laser diffraction;

[0108] The composite particles contain 20-80 wt% silicon.

[0109] In another aspect, the present invention provides composite particles for use as electroactive materials in metal-ion batteries, the composite particles comprising:

[0110] Including granular porous carbon frameworks with micropores and optionally mesopores; and

[0111] Silicon domains located within the pores of a granular porous carbon framework; wherein:

[0112] P1 is the total volume of micropores and mesopores in the granular porous carbon framework, expressed in cm. 3 / g represents, where P1 is 0.5-1.6; and

[0113] VP07 is the volume of pores with a diameter of 0.7 nm or smaller in a particulate porous carbon framework, expressed as a percentage of P1, where VP07 is in the range of 10-27%.

[0114] P1 and VP07 were measured by nitrogen adsorption method;

[0115] Among them, the composite particles D 50 Particle size ranges from 1 to 30 μm, as measured by laser diffraction;

[0116] The particle size distribution span of the composite particles (D) 98 -D1) / D 50 The value is less than 2, as measured by laser diffraction.

[0117] The composite particles contain 20-80 wt% silicon, of which at least 20 wt% is surface silicon, as determined by thermogravimetric analysis (TGA).

[0118] In another aspect, the present invention provides composite particles for use as electroactive materials in metal-ion batteries, the composite particles comprising:

[0119] Including granular porous carbon frameworks with micropores and optionally mesopores; and

[0120] Silicon domains located within the pores of a granular porous carbon framework; wherein:

[0121] P1 is the total volume of micropores and mesopores in the granular porous carbon framework, expressed in cm. 3 / g indicates that P1 is at least 0.35; and

[0122] VP07 is the volume of pores with a diameter of 0.7 nm or smaller in a particulate porous carbon framework, expressed as a percentage of P1, where VP07 is in the range of 5.1-35%.

[0123] The micropore volume of the granular porous carbon framework is at least 0.3 cm³. 3 / g;

[0124] P1, VP07, and micropore volume were measured by nitrogen adsorption method;

[0125] Among them, the composite particles D 50 The particle size is no more than 30 μm, as measured by laser diffraction;

[0126] The composite particles contain 20-80 wt% silicon.

[0127] In another aspect, the present invention provides composite particles for use as electroactive materials in metal-ion batteries, the composite particles comprising:

[0128] Including granular porous carbon frameworks with micropores and optionally mesopores; and

[0129] Silicon domains located within the pores of a granular porous carbon framework; wherein:

[0130] P1 is the total volume of micropores and mesopores in the granular porous carbon framework, expressed in cm. 3 / g indicates that P1 is at least 0.35; and

[0131] VP07 and VP2 are the volumes of pores with pore diameters of 0.7 nm or less and 2.0 nm or less in the particulate porous carbon framework, respectively, expressed as a percentage of P1, wherein VP07 is in the range of 5.1-35% and VP2 is at least 2.5 × VP07;

[0132] The micropore volume of the granular porous carbon framework is at least 0.3 cm³. 3 / g;

[0133] P1, VP07, VP2, and micropore volume were measured using nitrogen adsorption.

[0134] Among them, the composite particles D 50 The particle size is no more than 30 μm, as measured by laser diffraction;

[0135] The composite particles contain 20-80 wt% silicon, of which at least 20 wt% is surface silicon, as determined by thermogravimetric analysis (TGA).

[0136] In another aspect, the present invention provides composite particles for use as electroactive materials in metal-ion batteries, the composite particles comprising:

[0137] Including granular porous carbon frameworks with micropores and optionally mesopores; and

[0138] Silicon domains located within the pores of a granular porous carbon framework; wherein:

[0139] P1 is the total volume of micropores and mesopores in the granular porous carbon framework, expressed in cm. 3 / g indicates that P1 is at least 0.35; and

[0140] VP07, VP2, VP5, and VP20 represent the volumes of pores with diameters of 0.7 nm or less, 2.0 nm or less, 5.0 nm or less, and 20.0 nm or less in particulate porous carbon frameworks, respectively, expressed as a percentage of P1. VP07 is in the range of 5.1-35%, VP2 is in the range of 45-90%, and VP20-VP5 are less than 20%.

[0141] The BET surface area of ​​the granular porous carbon framework is at least 1,000 m². 2 / g;

[0142] P1, VP07, VP2, VP5 and VP20 were measured by nitrogen adsorption method;

[0143] Among them, the composite particles D 50 The particle size is no more than 30 μm, as measured by laser diffraction;

[0144] The composite particles contain 20-80 wt% silicon.

[0145] The particulate porous framework preferably contains a conductive material. Using conductive particulate porous frameworks is advantageous because they form a conductive framework within the composite particles, thereby facilitating the flow of electrons between lithium atoms / ions inserted into the electroactive material and the current collector.

[0146] The preferred type of particulate porous framework contains or is composed of conductive carbon material, referred to herein as conductive particulate porous carbon framework.

[0147] The particulate porous framework preferably comprises at least 80 wt% carbon, more preferably at least 85 wt% carbon, more preferably at least 90 wt% carbon, more preferably at least 95 wt% carbon, and optionally at least 98 wt% or at least 99 wt% carbon. The carbon may be crystalline carbon or amorphous carbon, or a mixture of crystalline and amorphous carbon. The porous carbon particles may be hard carbon particles or soft carbon particles.

[0148] As used in this article, the term "hard carbon" refers to a disordered carbon matrix in which carbon atoms are predominantly sp. 2 Hybridized states (triangular bonds) exist within nanoscale polycyclic aromatic hydrocarbon (PAH) domains. These PAH domains are cross-linked through chemical bonds, such as COC bonds. Due to the chemical cross-linking between PAH domains, hard carbon cannot be converted into graphite at high temperatures. Hard carbon exhibits graphite-like properties, as evidenced by the large G band (approximately 1600 cm⁻¹) in Raman spectroscopy. -1 This has been proven. However, carbon is not completely graphitized, as evidenced by the prominent D band (approximately 1350 cm⁻¹) in the Raman spectrum. -1 This has been proven.

[0149] As used in this article, the term "soft carbon" also refers to a disordered carbon matrix in which carbon atoms are mainly sp atoms. 2 Hybridized states (triangular bonds) exist within polycyclic aromatic hydrocarbon domains ranging in size from 5 to 200 nm. Compared to hard carbon, the polycyclic aromatic hydrocarbon domains in soft carbon are associated through intermolecular forces but not cross-linked by chemical bonds. This means they graphitize at high temperatures. The porous carbon particle framework preferably contains at least 50% sp. 2 Hybrid carbon, as measured by XPS. For example, particulate porous carbon frameworks can suitably contain 50% to 98% sp. 2 Hybridized carbon, 55% to 95% sp 2 Hybridized carbon, 60% to 90% sp 2 Hybrid carbon or 70% to 85% sp2 Hybridized carbon.

[0150] When the granular porous framework is a granular porous carbon framework, the relative intensity ratio (ID) of the D peak to the G peak of the granular porous carbon framework is... D / I G The Ig can be ≤2.0 or ≤1.8, as measured by Raman spectroscopy. Alternatively or additionally, the Ig of granular porous carbon frameworks... D / I G It can be ≥0.6, ≥0.8, ≥1, or ≥1.05. For example, the Ig of granular porous carbon frameworks. D / I G It can be in the range of 0.6-1.8 or 1.0-1.6.

[0151] Particulate porous frameworks can be provided either by synthesizing frameworks or by obtaining frameworks from suppliers.

[0152] More preferably, the granular porous framework is a granular porous carbon framework. The granular porous carbon framework used in this invention is most preferably in the form of activated carbon. The term "activated carbon" refers to a carbonaceous material that has undergone physical or chemical treatment to increase its porosity and surface area. Chemical activation or physical activation mechanisms (e.g., high-temperature steam or CO2) are commonly used methods in activated carbon production. Suitable activation processes involve contacting pyrolytic carbon with one or more of oxygen, steam, CO, and CO2 at temperatures ranging from 300 to 1500°C, 600 to 1200°C, or 600 to 1000°C.

[0153] Alternatively, known methods can be used to obtain frameworks with customized pore structures by template-assisted carbonization of zeolites. In another approach, frameworks with customized pore structures can be obtained by carbonizing metal-organic frameworks (such as zinc imidazolium ester frameworks) and washing the carbonized material to remove residual metals.

[0154] Mesoporous structures can also be obtained through known template processes, using extractable pore-forming agents such as MgO and other colloidal or polymeric templates, which can be removed by thermal or chemical methods after pyrolysis or activation.

[0155] Depending on the starting materials and pyrolysis process conditions, a wide variety of particulate porous carbon frameworks are available in the art. Particulate porous carbon frameworks of various sizes are available from commercial suppliers.

[0156] Various carbonaceous materials can be used to prepare suitable particulate porous carbon frameworks via pyrolysis. Plant sources are preferred. Examples of plant sources include the shells and husks of seeds, nuts, and fruits (including drupes, kernels, and pits). Examples of these plant sources include the shells and husks of coconuts (including coconut fiber), peanuts, walnuts, apricots, almonds, palm seeds, peaches, olives, hazelnuts, bamboo, and bark (e.g., the bark of cork trees (including pine, spruce, larch, and poplar) and hardwood trees (including oak)). Coconut shells are a preferred plant source. Fossil carbon sources, such as coal, can also be used. Examples of resins and polymers used as carbonaceous materials include phenolic resins, phenolic varnish resins, asphalt, melamine, polyacrylates, polystyrene, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers comprising monomer units of acrylates, styrene, α-olefins, vinylpyrrolidone, and other vinyl unsaturated monomers.

[0157] Carbonaceous materials (e.g., plant-derived) preferably have an elemental composition comprising at least 40 wt% carbon, at least 3 wt% hydrogen, and at least 30 wt% oxygen. Trace amounts of nitrogen, sulfur, and chlorine may also be present. More preferably, the elemental composition of the carbonaceous material comprises about 50 wt% carbon, 5 wt% hydrogen, and 40 wt% oxygen, with trace amounts of nitrogen, sulfur, and chlorine present.

[0158] Particulate porous carbon frameworks are typically obtained from carbonaceous materials in a two-step process. First, the carbonaceous material is pyrolyzed by heating in an inert atmosphere. The inert atmosphere can be nitrogen, CO2, rare gases, or mixtures thereof. Pyrolysis is typically carried out at temperatures of about 400 to 900°C, or about 500 to 700°C, or about 550 to 700°C, to allow the carbon to dehydrate and lose volatiles. Preferably, the temperature does not exceed about 700°C. Optionally, the carbonaceous material is pretreated to remove impurities prior to heating. Optionally, the carbonaceous material is purified and / or washed and dried prior to heating. Optionally, the carbonaceous material is sieved and crushed or ground to obtain uniformly sized particles prior to heating. Optionally, the carbonaceous material is granulated prior to heating.

[0159] Secondly, the pyrolysis material is activated by heating it in a flow of one or more of oxygen, steam, CO, and CO2 at a temperature between 600°C and 1200°C. This allows a chemical reaction between the carbon and the flowing gas to occur on the inner surface of the carbon, removing carbon from the pore walls and thus increasing the pore volume. This gas activation process, also known as a physical activation process, allows for easy modification of the pore size, thereby producing activated carbon with the desired porosity. Preferably, the pyrolysis material is activated with steam.

[0160] Physical activation can be suitably carried out in a rotary kiln, fixed-bed reactor, or fluidized-bed reactor. Optionally, additional washing, rinsing, or purification steps may be performed after activation. Optionally, the pyrolysis and activation steps can be combined into a continuous process. Optionally, after the activation step, the activated material is pulverized (e.g., ground) and / or sieved to obtain particles of the desired size.

[0161] The burn-off rate of the pyrolytic material during activation is preferably at least 15%, or at least 30%, or at least 40%. The burn-off rate is preferably no more than 80%, or no more than 75%, or no more than 70%. The burn-off rate is the mass fraction of the pyrolytic material removed during the physical activation step, expressed as a percentage of the material mass before the start of physical activation.

[0162] In chemical activation methods, carbonaceous materials are impregnated with chemical activators (such as NaOH, KOH, K₂CO₃, H₃PO₄, CaCl₂, ZnCl₂, and mixtures thereof). The carbonaceous materials are typically impregnated before pyrolysis, and the pyrolysis step occurs simultaneously with activation, although the carbonaceous materials may be carbonized before chemical impregnation. Pyrolysis in chemical activation can be carried out at 250–1000 °C or 500–950 °C. If porous carbon is formed using a chemical activation process, the activation mechanism does not create pores by removing carbon, but rather by enlarging existing pores or pushing apart (peeling) graphene sheets. This is detrimental to maintaining a high proportion of micropore space accessible via narrow channels / openings. This is considered to result in relatively poor electrochemical performance of composite materials prepared from chemically activated porous carbon materials. Therefore, it is preferable to prepare particulate porous carbon frameworks by physical activation.

[0163] It has been found that granular porous carbon frameworks with target VP07 values ​​and other desirable porosity parameters defined herein can be obtained by controlling the processing parameters during carbon activation. It is assumed that VP07 increases with increasing activation time until a certain limit is reached, after which VP07 is expected to decrease. For example, for synthetic (i.e., polymer or resin) carbon activated by CO2 to different loss-on-ignition levels (38 wt%, 47 wt%, and 55 wt%), an increase in VP07 was observed as the loss-on-ignition level decreased. P1 also increases with increasing loss-on-ignition level. A similar trend was observed when steam activation was used. At the same loss-on-ignition level, CO2 activation provided higher VP07 values ​​than steam activation for both synthetic carbon and plant-derived carbon.

[0164] A process is provided for preparing a particulate porous carbon framework as defined herein, the process comprising activating pyrolytic carbon by heating in a CO2 flow at a temperature between 600°C and 1200°C, wherein the pyrolytic carbon has a burn-off rate of not more than 50 wt% or not more than 45 wt%, and optionally at least 15%. This process may constitute step (a) in a process for preparing the composite particles provided herein. Therefore, this process preferably proceeds to the step of: (b) depositing electroactive material domains in the pores of the particulate porous framework.

[0165] 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).

[0166] The following is an example of typical activated carbon synthesis:

[0167] Synthetic activated carbon was prepared from a mixture of Novolak resin and 11% hexamethylenetetramine powder (Bakelite PF 6705 FP, purchased from Hexion GmbH). This starting material was crosslinked at 150°C for 1 h, and the crosslinked solid mass was hammered into small pieces of 2–3 cm, then ground into particles of approximately 100 μm. The cured resin powder was then pyrolyzed at 800°C under a nitrogen flow of 1 L / min for 10 min. The carbon yield from this precursor was 57–59%. After carbonization, the carbon was ball-milled to a particle size of 3–4 μm, and the total pore volume of the obtained carbon material was 0.25–0.3 cm³. 3 / g, including 0.20–0.22 cm 3 Microporosity of / g and 650–700 m 2 / g surface area. This carbon is then activated in steam or CO2 to achieve a desired pore volume. CO2 activation is used to achieve 0.8–0.9 cm². 3 The typical activation temperature for / g total pore volume is 950-980℃, with a residence time of 5-8h, depending on the amount of activated carbon, CO2 flow rate, and furnace type. Because steam is more reactive, the temperature used for steam activation is lower than that for CO2, typically 850℃. The residence time of steam at the activation temperature is usually 6-9h, depending on the type and amount of activated carbon, steam flow rate, and furnace type.

[0168] Examples of activated carbon prepared using steam activation are as follows:

[0169] To prepare a material with a total pore volume of 0.79 cm³ 3 / g of steam-activated synthetic framework, with steam introduced via a humidifier consisting of a nitrogen atomizer (3 bar injection pressure), and water added dropwise into the atomization chamber through a 1 mm orifice perpendicular to the 1 mm orifice, wherein a high-pressure nitrogen gas flow induces atomization by impacting the water droplets with the high-pressure gas. Heating belts are used at the inlet and outlet to prevent accidental steam condensation. The carbonized phenolic resin is ball-milled in a planetary ball mill to D 50 = 3 μm (60 g loading, 105, 10 mm balls, 300 RPM, 20 min intervals). Subsequently, 15 g of the milled carbonized phenolic resin was loaded into a short alumina crucible, ensuring the material was evenly distributed throughout the crucible. Steam activation was performed in a tube furnace with the crucible placed in the center of the heating zone. The furnace was purged with N2 at 0.8 L / min for 10–30 min. A heating rate of 8.7 °C / min was used, with a setpoint of 850 °C. When the temperature reached 840 °C, water was injected into the atomizing nozzle at a rate of 0.25 mL / min (water injection volume), and the temperature was stabilized after reaching 850 °C. A residence time of 345 min was observed. Upon completion of the residence time, the steam flow rate was set to zero, and the heating belt was shut off.

[0170] Alternatives to particulate porous carbon frameworks include those composed of 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 carbide, boron nitride, or vanadium nitride. Preferred alternatives to particulate porous carbon frameworks are those composed of titanium nitride, silicon carbide, or boron nitride.

[0171] The electroactive material is suitably selected from silicon, tin, germanium, and aluminum, as well as mixtures and alloys thereof. Silicon is a particularly preferred electroactive material. The electroactive material may optionally contain small amounts of one or more dopants. Suitable dopants include boron and phosphorus, other n-type or p-type dopants, or nitrogen. Preferably, the dopant is present in a total amount of no more than 2 wt%, based on the total amount of the electroactive material (e.g., silicon) and the dopant.

[0172] Particulate porous frameworks provide the framework for electroactive material domains. The term "electroactive material domain" refers to an electroactive material volume, typically existing in elemental form, whose maximum size is determined by the pore size of the particulate porous framework in which it resides. Electroactive material domains are typically located within the micropores and optionally mesopores of the particulate porous framework. Thus, due to the size of the micropores and mesopores, electroactive domains can be described as nanoscale electroactive domains, where the term "nanoscale" is generally understood to mean a size less than 100 nm, although the maximum size of the electroactive domain in any direction is typically less than 50 nm, and usually significantly less than 50 nm, due to the size of the micropores and mesopores. For example, domains can take the form of regular or irregular particles, or bounded layers or regions of a coating.

[0173] The particulate porous framework defined herein as part of the composite particles of the present invention can be provided independently, i.e., in the absence of electroactive material domains located within the pores. This provides a convenient starting material for manufacturing the composite particles of the present invention. Therefore, the present invention provides a particulate porous framework comprising micropores and optionally mesopores; wherein:

[0174] P1 represents the total volume of micropores and mesopores in the granular porous framework, expressed in cm³. 3 / g indicates that P1 is at least 0.35; and

[0175] VP07 is the volume of pores with a diameter of 0.7 nm or smaller in a particulate porous framework, expressed as a percentage of P1, where VP07 is in the range of 5.1-40%.

[0176] P1 and VP07 were measured by nitrogen adsorption method.

[0177] The particulate porous framework can be supplied as a kit along with the electroactive material precursor. The kit components can be stored separately until the electroactive material domains are deposited into the pores of the particulate porous framework using the electroactive material precursor.

[0178] The process for preparing composite particles includes the following steps: (a) providing a particulate porous framework as defined herein; and (b) depositing electroactive material domains within the pores of the particulate porous framework. Step (b) typically involves contacting the particulate porous framework with an electroactive material precursor at a temperature sufficient to deposit the electroactive material domains within the pores of the particulate porous framework. The precursor is most preferably gaseous, as such precursors are readily available for use in CVI processes.

[0179] Suitable silicon precursors include silane (SiH4), disilane (Si2H6), trisilane (Si3H8), and tetrasilane (Si4H). 10 ), pentasilane (Si5H) 12 ), hexasilane (Si6H)14 The silicon precursor is selected from silane (SiH4), disilane (Si2H6), trimethylsilane (Si3H8), tetramethylsilane (Si4H), or chlorosilane, such as trichlorosilane (HSiCl3), dichlorosilane (H2SiCl2), or chlorosilane (H3SiCl), or methylchlorosilane, such as methyltrichlorosilane (CH3SiCl3) or dimethyldichlorosilane ((CH3)2SiCl2). Preferably, the silicon precursor is selected from silane (SiH4), disilane (Si2H6), trisilane (Si3H8), tetrasilane (Si4H6), and methylchlorosilane (Si2H6). 10 A particularly preferred silicon precursor is silane (SiH4).

[0180] Suitable germanium precursors include germanane (GeH4), hexamethyldigerane ((CH3)3GeGe(CH3)3), tetramethylgerane ((CH3)4Ge), hydrogenated tributylgermanium ([CH3(CH2)3]3GeH), hydrogenated triethylgermanium ((C2H5)3GeH), and hydrogenated triphenylgermanium ((C6H5)3GeH). Germanane is the preferred germanium precursor.

[0181] Suitable tin precursors include bis[bis(trimethylsilyl)amino]tin(II) ([[(CH3)3Si]2N]2Sn), tetraallyltin ((H2C=CHCH2)4Sn), tetra(diethylamide)tin(IV) ([(C2H5)2N]4Sn), tetra(dimethylamide)tin(IV) ([(CH3)2N]4Sn), tetramethyltin (Sn(CH3)4), tetravinyltin (Sn(CH=CH2)4), and tin(II) acetylacetonate (C 10 H 14 O4Sn), trimethyl(phenylethynyl)tin (C6H5C≡CSn(CH3)3) and trimethyl(phenyl)tin (C6H5Sn(CH3)3). The preferred tin precursor is tetramethyltin.

[0182] Suitable aluminum precursors include tris(2,2,6,6-tetramethyl-3,5-heptadecanoic acid)aluminum (Al(OCC(CH3)3CHCOC(CH3)3)3), trimethylaluminum ((CH3)3Al), and tris(dimethylamino)aluminum(III) (Al(N(CH3)2)3). Trimethylaluminum is the preferred aluminum precursor.

[0183] Step (b) can suitably be carried out via chemical vapor infiltration (CVI) of a gaseous electroactive material precursor into the porous structure of a particulate porous framework. As used herein, CVI refers to the process of thermally decomposing a gaseous precursor on a surface to form an electroactive material (typically present in its elemental form) and gaseous byproducts at the surface. In the case of a chlorinated compound (such as a chlorosilane), the precursor is mixed with hydrogen, preferably at an atomic ratio of at least 1:1 hydrogen to chlorine.

[0184] Optionally, the precursor is chlorine-free. Chlorine-free means that the precursor contains less than 1 wt%, preferably less than 0.1 wt%, and more preferably less than 0.01 wt% of chlorine-containing compounds.

[0185] The gaseous electroactive material precursor can be used in pure form (or substantially pure form) or as a dilution mixture with an inert carrier gas (such as nitrogen or argon). Preferably, step (b) includes contacting the particulate porous framework with a gas, which, based on the total volume of the gas, contains at least 30% by volume, or at least 40% by volume, or at least 50% by volume, or at least 60% by volume, or at least 70% by volume, or at least 80% by volume, or at least 90% by volume, or at least 95% by volume, or at least 97% by volume, or at least 99% by volume of the gaseous electroactive material precursor.

[0186] According to standard procedures for working in an inert atmosphere, the presence of oxygen in step (b) should be avoided to prevent unwanted oxidation of the deposited electroactive material. Preferably, the oxygen content is less than 0.01% by volume, more preferably less than 0.001% by volume, based on the total volume of the gas used in step (b).

[0187] 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 350 to less than 400°C, or 355 to 395°C, or 360 to 390°C, or 360 to 385°C, or 360 to 380°C.

[0188] The pressure in step (b) may be in the range of 1 to 5000 kPa, or 20 to 500 kPa, or 40 to 200 kPa, or 50 to 150 kPa, or 60 to 120 kPa, or 80 to 100 kPa. The pressure in step (b) may be maintained at no more than 200 kPa, or no more than 150 kPa, or no more than 120 kPa, or no more than 110 kPa, or no more than 100 kPa, or no more than 90 kPa, or no more than 80 kPa. The pressure in any step of the claimed process refers to the absolute pressure in the reaction zone, which may include any suitable reactor vessel. It is considered advantageous to deposit electroactive materials under high pressure because of the selection of granular porous frameworks with significant pore volumes of small pore diameters of 0.7 nm or less, as this facilitates 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 no more than 5000 kPa, or no more than 3000 kPa, or no more than 2000 kPa. For example, preferably the pressure in step (b) is in the range of 200-2000 kPa.

[0189] CVI deposition of electroactive materials leads to the elimination of byproducts, particularly byproduct gases such as hydrogen. Step (b) preferably further includes separating the byproducts from the particles formed in step (b). This separation can be achieved by introducing an inert gas into the reactor and / or by evacuating the reactor at a reduced pressure. For example, separation of the byproducts from the particles formed in step (b) can be achieved by evacuating the reactor to a pressure 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 not only effectively removes byproducts from the gas phase but also desorbs any byproducts that may be adsorbed on the surface of the deposited electroactive material.

[0190] Various loadings of electroactive materials can be obtained in the composite particles. The composite particles preferably contain 20-80 wt% electroactive material, or 30-70 wt% electroactive material, or 40-60 wt% electroactive material. The composite particles may contain at least 26 wt% electroactive material, or at least 28 wt% electroactive material, or at least 30 wt% electroactive material, or at least 32 wt% electroactive material, or at least 34 wt% electroactive material, or at least 36 wt% electroactive material, or at least 38 wt% electroactive material, or at least 40 wt% electroactive material, or at least 42 wt% electroactive material, or at least 44 wt% electroactive material. When the electroactive material is silicon, these ranges may refer to the amount of silicon; for example, the composite particles preferably contain 20-80 wt% silicon.

[0191] Preferably, the amount of electroactive material in the composite particles is selected such that, after step (b), at least 20% to up to 90% of the internal pore volume of the particulate porous framework is occupied by the electroactive material. For example, the electroactive material may 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 can effectively accommodate the expansion of the electroactive material during charging and discharging without a large amount of excess pore volume that is detrimental to the volumetric capacity of the composite particles. However, the amount of electroactive material will not be high enough to hinder effective lithiation due to insufficient metal ion diffusion rate or mechanical resistance to lithiation due to insufficient expansion volume.

[0192] When the electroactive material is silicon, the amount of silicon in the composite particles can be related to the available pore volume in the particulate porous framework by the following requirement: the mass ratio of silicon to the particulate porous framework is in the range of [0.5 × P1 to 1.9 × P1] : 1, where P1 is as defined above (e.g., if the total volume of micropores and mesopores in the particulate porous framework is 1.2 cm). 3 / g, then P1 = 1.2). This relationship takes into account the density of silicon and the pore volume of the particulate porous framework, thereby defining the weight ratio of silicon at which the pore volume occupies about 20% to 82%. Preferably, the weight ratio of silicon to the particulate porous framework is in the range of [0.6×P1 to 1.8×P1] : 1, or [0.7×P1 to 1.7×P1] : 1, or [0.8×P1 to 1.6×P1] : 1.

[0193] The amount of silicon or other electroactive materials in the composite particles can be determined by elemental analysis. The content of electroactive materials is preferably determined by ICP-OES (Inductively Coupled Plasma Emission Spectrometry). Many ICP-OES instruments are commercially available, such as the iCAP® 7000 series ICP-OES analyzer available from ThermoFisher Scientific. The carbon content (and, if necessary, the hydrogen, nitrogen, and oxygen content) of the individual composite particles and the granular porous framework 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.

[0194] Preferably, at least 70 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, or most preferably 98 wt% of the electroactive material in the composite particles is located within the internal pore volume of the particulate porous framework, such that little or no electroactive material is located on the external surface of the particulate porous framework. As discussed above, in the CVI process, the deposition of the electroactive material occurs at the surface of the particulate porous framework. Given the very high 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 entirely within the pores of the particulate porous framework.

[0195] Before the electroactive material is deposited within the pores of the granular porous framework, the nitrogen-accessible pore volume of the composite particles may be less than 0.05 × P1, where P1 is the total volume of micropores and mesopores in the granular porous framework, expressed in cm³. 3 / g represents the total volume of micropores and mesopores in the composite particles after deposition of the electroactive material, under ideal conditions. 3 / g or less than 0.01 cm 3 / g.

[0196] Composite particles can be characterized by thermogravimetric analysis (TGA) in air. This analytical method relies on the principle that an increase in weight is observed when electroactive materials are oxidized in air at high temperatures.

[0197] Generally, it is known that atoms at the surface of a material have different bonding interactions with atoms in the bulk material, and this difference is usually described by the surface energy of the material. In the case of silicon deposition via chemical vapor infiltration (CVI), the free valences of silicon atoms at the surface typically carry hydride groups. If such a hydride-terminated silicon surface comes into contact with air, it reacts with oxygen to form a native oxide surface. However, surfaces inaccessible to air retain their hydride-terminated form.

[0198] As defined herein, “surface silicon” is calculated based on the initial mass increase of the TGA trace measured over a temperature range from a minimum between 150°C and 500°C to between 550°C and 650°C, where the TGA is performed in air at a heating rate of 10°C / min. It is assumed that this mass increase is due to oxidation of the surface silicon, and therefore the percentage of surface silicon to total silicon can be determined according to the following formula:

[0199] Y = 1.875 × [(M max – M min ) / M f ] ×100%

[0200] Where Y is the percentage of surface silicon in the sample relative to the total silicon, and M... max M represents the maximum mass of a sample measured within a temperature range of 550°C to 650°C. min The minimum mass of the sample measured at temperatures above 150°C and below 500°C, and M f This represents the mass of the sample after oxidation at 1400°C. For completeness, it should be understood that 1.875 is the molar mass ratio of SiO2 to O2 (i.e., the mass ratio of the generated SiO2 to the mass increase due to the addition of oxygen). Typically, TGA analysis is performed using a sample size of 10 mg ± 2 mg.

[0201] It has been found that when the surface silicon, as determined by the TGA method described above, constitutes at least 10 wt% of the total silicon in the composite particles, the reversible capacity retention over multiple charge / discharge cycles is significantly improved. Therefore, preferably, at least 10 wt%, or at least 15 wt%, or more preferably at least 20 wt%, or at least 22 wt%, or at least 25 wt%, or at least 30 wt%, or at least 35 wt% of the silicon in the composite particles is surface silicon, as determined by thermogravimetric analysis (TGA). One advantage of this invention is that providing a particulate porous framework helps achieve a favorable amount of surface silicon when silicon is deposited in a framework using a silicon precursor.

[0202] Even after passivation in air, a significant proportion of hydride-terminated surface silicon was still measurable in the particulate material, indicating that the composite particles contain internal silicon surfaces inaccessible to air. This suggests that the internal pore spaces of the porous carbon framework were first lined with silicon and then capped to form internal void spaces, with the hydride-terminated silicon surfaces oriented toward the closed internal void spaces. This, in turn, indicates that the characteristic length scale of the silicon domains is much smaller than that of the pores themselves.

[0203] Because the internal voids cannot contact the electrolyte, the silicon surface is protected from SEI formation, thus minimizing irreversible lithium loss during the first charge cycle. Further exposure of the electroactive material is also significantly prevented in subsequent charge-discharge cycles, ensuring that SEI formation does not become a significant failure mechanism leading to capacity loss. Simultaneously, this silicon is constrained by hydrostatic pressure during lithiation, allowing it to utilize the voids during lithiation-induced expansion.

[0204] In addition to the surface silicon content, the composite particles preferably have a low content of coarse bulk silicon, as determined by TGA. Coarse bulk silicon is defined herein as silicon that oxidizes above 800°C, as determined by TGA, wherein the TGA is performed in air at a heating rate of 10°C / min. Therefore, the coarse bulk silicon content is determined according to the following formula:

[0205] Z = 1.875 × [(M f - M 800 ) / M f ] ×100%

[0206] Where Z represents the percentage of unoxidized silicon at 800℃, and M... 800 The mass of the sample at 800℃ is given, and M is given. f The mass of ash is the mass of silicon at which oxidation is complete at 1400°C. For the purposes of this analysis, it is assumed that any increase in mass above 800°C corresponds to the oxidation of silicon to SiO2, and that the total mass at which oxidation is complete is SiO2.

[0207] Silicon that oxidizes above 800°C is less desirable. Preferably, as determined by TGA, no more than 10 wt%, or no more than 8 wt%, or no more than 6 wt%, or no more than 5 wt%, or no more than 4 wt%, or no more than 3 wt%, or no more than 2 wt%, or no more than 1.5 wt% of silicon is crude bulk silicon.

[0208] Preferably, at least 30 wt% of the silicon is surface silicon, and no more than 10 wt% of the silicon is crude bulk silicon, both determined by TGA. More preferably, at least 35 wt% of the silicon is surface silicon, and no more than 8 wt% of the silicon is crude bulk silicon, both determined by TGA. More preferably, at least 40 wt% of the silicon is surface silicon, and no more than 5 wt% of the silicon is crude bulk silicon, both determined by TGA. More preferably, at least 45 wt% of the silicon is surface silicon, and no more than 2 wt% of the silicon is crude bulk silicon, both determined by TGA.

[0209] When the granular porous framework is a granular porous carbon framework, the relative intensity ratio (ID) of the D peak to the G peak of the composite particles is...D / I G The Ig can be ≤2.0 or ≤1.8, as measured by Raman spectroscopy. Alternatively or additionally, the Ig of the composite particles... D / I G It can be ≥0.6, ≥0.8, ≥1, or ≥1.05. For example, the I of composite particles... D / I G It can be in the range of 0.6-1.8 or 1.0-1.6.

[0210] The process may include an annealing step after step (b), in which the composite particles are annealed at high temperature in an inert or reducing atmosphere.

[0211] The annealing step is associated with a number of interconnected thermally induced processes that stabilize 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, the volume shrinkage of Si domains leading to the reopening of some pore spaces, and the promotion of covalent bonds (e.g., Si-C bonds in the case of a particulate porous framework) between silicon and the internal surfaces of the particulate porous framework.

[0212] For example, the annealing temperature 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 annealing temperature is no more than 900°C, or no more than 850°C, or no more than 800°C, or no more than 750°C, or no more than 700°C, or no more than 680°C, or no more than 660°C, or no more than 650°C.

[0213] The annealing temperature can 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. Alternatively, the annealing temperature can 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.

[0214] The temperature of the annealing step may be higher than the temperature in step (b). Preferably, the temperature of 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).

[0215] 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 no more than 72 hours, or no more than 48 hours, or no more than 24 hours, or no more than 12 hours, or no more than 6 hours, or no more than 5 hours, or no more than 4 hours, or no more than 3 hours.

[0216] The duration of the annealing step can 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.

[0217] The annealing step is carried out in an inert or reducing atmosphere. Preferably, the atmosphere is selected from a nitrogen atmosphere, or an atmosphere including a hydrogen atmosphere, an inert gas atmosphere, or a mixture thereof.

[0218] Preferably, the annealing step is performed at a temperature ranging from 400°C to 900°C for a period of 1 minute to 72 hours. Alternatively, it is performed at a temperature ranging from 500°C to 900°C for a period of 30 minutes to 4 hours. Or, it is performed at a temperature ranging from 600°C to 900°C for a period of 1 hour to 4 hours.

[0219] The ratio of the BET surface area of ​​the particles formed after the annealing step to the BET surface area of ​​the composite particles can 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.

[0220] 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 no more than 15:1, no more than 14:1, no more than 13:1, or no more than 12:1.

[0221] The ratio of the total pore volume of micropores and mesopores of the particles formed after the annealing step (as measured by gas adsorption) to the total pore volume of micropores and mesopores of the composite particles (as measured by gas adsorption) 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.

[0222] The ratio of the total pore volume of micropores and mesopores of the particles formed after the annealing step (as measured by gas adsorption) to the total pore volume of micropores and mesopores of the composite particles (as measured by gas adsorption) may not exceed 20:1, 19:1, 18:1, 17:1, 16:1, or 15:1.

[0223] 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 not exceed 0.8:1, 0.7:1, 0.6:1, or 0.5:1.

[0224] The ratio of the total hydrogen content of the particles formed after the annealing step to the total hydrogen content of the composite particles can be at least 0.1:1, at least 0.2:1, or at least 0.3:1.

[0225] After step (b), the process may include a passivation step in which the composite particles are brought into contact with a passivating agent.

[0226] As defined herein, a passivating agent is a compound or mixture of compounds capable of reacting with the surface of the silicon deposited in step (b) to form a modified surface. Specifically, a passivating agent as defined herein is a material capable of reacting with the surface of silicon to further reduce its surface energy.

[0227] Preferably, the passivation step is performed after the annealing step. As discussed above, one effect of the annealing step is to reopen the pore spaces previously blocked or capped by the silicon nanostructures, allowing the passivation gas to enter these pore spaces, thereby allowing for more extensive passivation of the silicon surface and eliminating hydrogen-capped silicon surfaces.

[0228] One type of passivation layer is a natural oxide layer. A natural oxide layer can be formed, for example, by exposing the silicon surface to a passivating agent selected from air or another oxygen-containing gas. The passivation layer may include a SiO2-based passivation layer. x The silica is silicon dioxide, wherein 0 < x ≤ 2. The silica is preferably amorphous silica. The formation of the natural oxide layer is exothermic and therefore requires careful process control to prevent the particulate material from overheating or even burning. 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, and optionally below 100°C before contact with the oxygen-containing gas.

[0229] Another type of passivation layer is, for example, a nitride layer formed by exposing a silicon surface to a passivating agent selected from ammonia or another nitrogen-containing molecule. The passivation layer may include the formula SiN... xThe silicon nitride is amorphous silicon nitride, wherein 0 < x ≤ 4 / 3. The nitride layer can be formed by contacting a silicon surface with ammonia at a temperature in the range of 200-700°C, preferably 400-700°C, more preferably 400-600°C. Then, if desired, the temperature can be increased to the range of 500-1000°C to form a nitride surface (e.g., SiN). x The silicon nitride surface, where x ≤ 4 / 3). Nitride passivation is superior to oxide passivation. Due to substoichiometric nitrides (such as SiN... x (where 0 < x ≤ 4 / 3) exhibits conductivity, and the nitride passivation layer can act as a conductive network, allowing for faster charging and discharging of electroactive materials. Phosphine can also be used as a passivating agent, as a phosphorus analog of ammonia. Another type of passivation layer is an oxide oxynitride layer, which is formed, for example, by exposing a silicon surface to a passivating agent containing ammonia (or another nitrogen-containing molecule) and oxygen. The passivation layer may include the formula SiO2. x N y The silicon oxynitride is amorphous silicon oxynitride, wherein 0 < x < 2, 0 < y < 4 / 3, and 0 < (2x+3y) ≤ 4.

[0230] Another type of passivation layer is a carbide layer. Passivation layers may include those of the formula SiC. x The silicon carbide is amorphous silicon carbide, wherein 0 < x ≤ 1. The silicon carbide is preferably amorphous silicon carbide. A carbide layer can be formed by contacting the silicon surface with a passivating agent selected from a carbon-containing precursor (e.g., in the range of 250 to 700°C). At lower temperatures, covalent bonds are formed between the silicon surface and the carbon-containing precursor; as the temperature increases, these covalent bonds transform into a monolayer of crystalline silicon carbide. Silicon carbide may have the formula SiC. x , where 0 < x ≤ 1.

[0231] Other suitable passivating agents include compounds containing olefin, alkyne or carbonyl functional groups, more preferably terminal olefin, terminal alkyne, aldehyde or ketone groups.

[0232] Preferred passivating agents include one or more compounds of the following formula:

[0233] (i) R 1 -CH=CH-R 1 ;

[0234] (ii) R 1 -C≡CR 1 ;and

[0235] (iii) O=CR 1 R 1 ;

[0236] Each R 1 Independently representing H or an unsubstituted or substituted aliphatic or aromatic hydrocarbon group having 1 to 20 carbon atoms, or two of which R 1 The groups form unsubstituted or substituted ring structures, which include 3 to 8 carbon atoms.

[0237] In particular, preferred passivating agents include one or more compounds of the following formula:

[0238] (i) CH2=CH-R 1 ;and

[0239] (ii) HC≡CR 1 ;

[0240] Where R 1 As defined above. Preferably, R 1 It is not replaced.

[0241] Examples of suitable passivating agents include ethylene, propylene, 1-butene, butadiene, 1-pentene, 1,4-pentadiene, 1-hexene, 1-octene, styrene, divinylbenzene, acetylene, phenylacetylene, norbornene, norbornadiene, and bicyclo[2.2.2]oct-2-ene. Optionally, mixtures of different passivating agents may also be used.

[0242] It is believed that passivating agents, including those containing olefins, alkynes, or carbonyl groups, undergo an insertion reaction with Si-H groups on the silicon surface to form a covalently passivated surface that is resistant to air oxidation. Therefore, the passivation reaction between the silicon surface and the passivating agent can be understood as a form of hydrosilylation, as shown in the figure below.

[0243]

[0244] Other suitable passivating agents include compounds containing active hydrogen atoms bonded to oxygen, nitrogen, sulfur, or phosphorus. For example, passivating agents can be alcohols, amines, thiols, or phosphine. It should be understood that the reaction of the -XH group with the hydride group at the silicon surface leads to the elimination of H2 and the formation of a direct bond between X and the silicon surface.

[0245] Suitable passivating agents in this category include compounds of the following formula.

[0246] (iv) HX-R 2 ,and

[0247] (v) HX-C(O)-R 1 ,

[0248] Where X represents O, S, NR 1 or PR 1 ; Each R 1Independently as defined above; and R 2 Represents an unsubstituted or substituted aliphatic or aromatic hydrocarbon group having 1 to 20 carbon atoms; or R 1 and R 2 Together they form an unsubstituted or substituted ring structure, in which the ring comprises 3 to 8 carbon atoms.

[0249] Preferably, X represents O or NH.

[0250] Preferably, R 2 This represents an optional substituted aliphatic or aromatic group having 2 to 10 carbon atoms. The amine group can also be incorporated into 4-10 member aliphatic or aromatic ring structures, such as in pyrrolidine, pyrrole, imidazole, piperazine, indole, or purine.

[0251] The contact between the composite particles and the passivating agent can be carried out at a temperature ranging from 25 to 500°C, preferably from 50 to 450°C, and more preferably from 100 to 400°C.

[0252] The process may include a deposition step after step (b) to deposit a lithium-ion permeable material into the pores and / or outer surface of the composite particles. Using lithium-ion fillers reduces SEI formation by decreasing the surface area of ​​the composite particles and preventing contact between the electrolyte and the silicon domains within the particles.

[0253] Preferably, the lithium-ion permeable material is a pyrolytic carbon material, and the deposition step includes combining the composite particles with the pyrolytic carbon precursor; and heating the pyrolytic carbon precursor to a temperature that effectively causes the conductive pyrolytic carbon material to deposit into the pores and / or onto 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, the deposition step is most preferably performed after the passivation step.

[0254] The pyrolytic carbon precursor is preferably a hydrocarbon. Suitable hydrocarbons include polycyclic aromatic hydrocarbons containing 10 to 25 carbon atoms and optionally 1 to 3 heteroatoms, wherein the polycyclic aromatic hydrocarbons are optionally selected from naphthalene, substituted naphthalenes (such as dihydroxynaphthalene), anthracene, tetraphenylene, pentaphenylene, fluorene, acenaphthene, phenanthrene, fluoranthene, pyrene, benzo[a], perylene, cardamom, fluorenone, anthraquinone, anthrone, and their alkyl-substituted derivatives. Suitable pyrolytic carbon precursors also include bicyclic monoterpenes, wherein the bicyclic monoterpenes are optionally selected from camphor, borneol, eucalyptol, camphene, careen, juniperene, thujone, and pinene. Other suitable pyrolytic carbon precursors include C2-C10 hydrocarbons, wherein the hydrocarbons are optionally selected from alkanes, alkenes, alkynes, cycloalkanes, cycloalkenes, and aromatics, such as methane, ethylene, propylene, limonene, styrene, cyclohexane, cyclohexene, α-terpinene, and acetylene. Other suitable pyrolytic carbon precursors include phthalocyanine, sucrose, starch, graphene oxide, reduced graphene oxide, pyrene, perhydropyrene, triphenylene, tetraphenylene, benzo[a]pyrene, perylene, methylbenzene, and β-pyrene. The preferred carbon precursor is acetylene.

[0255] In the deposition step, the suitable temperature for depositing the pyrolytic carbon material is in the range of 300 to 800°C or 400 to 700°C. For example, the temperature may be no more than 680°C, or no more than 660°C, or no more than 640°C, or no more than 620°C, or no more than 600°C, or no more than 580°C, or no more than 560°C, or no more than 540°C, or no more than 520°C, or no more than 500°C. The minimum temperature will depend 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.

[0256] The carbon-containing precursor used in the deposition step can be used in its pure form or as a dilution mixture with an inert carrier gas (such as nitrogen or argon). For example, the carbon-containing precursor can be used in amounts ranging from 0.1 to 100 vol%, or 0.5 to 20 vol%, or 1 to 10 vol%, or 1 to 5 vol%, depending on the total volume of the precursor and the inert carrier gas.

[0257] In the case of depositing pyrolytic carbon materials, the same compound can serve as both a passivating agent in the passivation step and a pyrolytic carbon precursor in the deposition step. For example, if styrene is chosen as the pyrolytic carbon precursor, then styrene will also act as a passivating agent if the composite particles are not exposed to another passivating agent before contacting it. In this case, the passivation and deposition of conductive carbon materials in each step can be carried out simultaneously, for example, at temperatures in the range of 300-700°C. Alternatively, the passivation and deposition of conductive carbon materials can be carried out sequentially, using the same material as both the passivating agent and the pyrolytic carbon precursor, but in which case the deposition step is carried out at a higher temperature than the passivation step and after the passivation step. For example, passivation can be carried out at temperatures in the range of 25°C to less than 300°C, and the deposition of pyrolytic carbon can be carried out at temperatures in the range of 300-700°C. These two steps can be suitably carried out sequentially by increasing the temperature while maintaining contact with the compound, which acts as both a passivating agent and a pyrolytic carbon precursor. At lower temperatures (e.g., in the range of 25°C to <300°C), passivation will be the primary process. As the temperature increases (e.g., to 300-700°C), the deposition of pyrolytic carbon will occur.

[0258] One advantage of this invention is that the determination of optimized pore structures based on VP07 provides a convenient and efficient way to evaluate whether new sources of particulate porous frameworks hold promise as starting materials for preparing composite particles with superior properties for metal-ion batteries. This can be achieved by measuring the pore structure of the frameworks, for example, using the conventional methods described herein, to determine whether an optimized pore structure exists without the expensive and time-consuming steps of depositing electroactive materials in the frameworks and performing electrochemical tests to evaluate the performance of the resulting composite particles. If an optimized pore structure exists, the framework is accepted for subsequent use. If an optimized pore structure does not exist, the framework is rejected. The pore structures of frameworks from different sources can then be measured. Once an optimized population of particulate porous frameworks has been identified, silicon can be deposited into the pores using silicon to provide composite particles.

[0259] Therefore, the present invention provides a process comprising the following steps:

[0260] (a1) Provide one or more groups of granular porous frameworks comprising micropores and optionally mesopores;

[0261] (a2) Measure the pore structure of each population;

[0262] (a3) Accept each group having an optimized pore structure and reject each group not having the optimized pore structure, wherein in the optimized pore structure:

[0263] P1 represents the total volume of micropores and mesopores in the granular porous framework, expressed in cm³. 3 / g indicates that P1 is at least 0.35; and

[0264] VP07 is the volume of pores with a diameter of 0.7 nm or smaller in a particulate porous framework, expressed as a percentage of P1, where VP07 is in the range of 5.1-40%.

[0265] P1 and VP07 were measured by nitrogen adsorption method;

[0266] (b) Depositing electroactive material domains into the pores of a recognized population of particulate porous frameworks.

[0267] It should be understood that the optimized pore structure can be further defined by any pore structure parameters of the granular porous framework defined above.

[0268] A particular advantage of this invention lies in its ability to screen multiple groups of granular porous frameworks. Therefore, preferably, at least two groups are provided in step (a1), and optionally at least one group is rejected in step (a3). The act of rejecting granular porous framework groups provides useful technical guidance because the groups do not need to undergo further testing.

[0269] Optionally, the process can be stopped if no population is accepted after measuring the pore structure of 10 populations. In this way, useful information is still provided that the 10 rejected populations do not have an optimized pore structure.

[0270] One advantage of this invention is that it allows the identification of optimized particulate porous frameworks at a laboratory scale, without requiring all viable particulate porous frameworks to be provided at an industrial scale before their suitability for end use is known. For example, the population 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 are identified in the laboratory, they can be obtained on a large scale with confidence that they will be suitable for manufacturing large quantities of composite particles with good properties. Therefore, the process of this invention preferably further includes providing an industrial-scale population of the accepted population of particulate porous frameworks, optionally wherein the industrial-scale population comprises at least 100 kg or at least 1,000 kg of the accepted particulate porous frameworks; and depositing electroactive material domains in the pores of the industrial-scale population of the accepted particulate porous frameworks. Kits comprising industrial-scale populations and silicon precursors are available.

[0271] Composite particles can be incorporated into compositions containing at least one other component. Specifically, a composition is provided comprising 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 can be used as an electrode composition and thus can be used to form the active layer of an electrode.

[0272] The composition may be a hybrid electrode composition comprising composite particles and at least one additional particulate electroactive material. Examples of the additional particulate electroactive material include graphite, hard carbon, silicon, tin, germanium, aluminum, and lead. The at least one additional particulate electroactive material is preferably selected from graphite and hard carbon, and most preferably, the at least one additional particulate electroactive material is graphite.

[0273] In the case of a mixed electrode composition, the composition preferably comprises 3 to 60 wt%, or 3 to 50 wt%, or 5 to 50 wt%, or 10 to 50 wt%, or 15 to 50 wt% of composite particles, based on the total dry weight of the composition. At least one additional particulate electroactive material is suitably present in an amount of 20 to 95 wt%, or 25 to 90 wt%, or 30 to 75 wt%, based on the total dry weight of the composition.

[0274] D of at least one additional particulate electroactive material 50 The particle size is preferably in the range of 10 to 50 μm, more preferably 10 to 40 μm, more preferably 10 to 30 μm and most preferably 10 to 25 μm, for example 15 to 25 μm.

[0275] 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.

[0276] D of at least one additional particulate electroactive material 90 The particle size is preferably up to 100 μm, more preferably up to 80 μm, more preferably up to 60 μm, more preferably up to 50 μm and most preferably up to 40 μm.

[0277] At least one additional particulate electroactive material is preferably selected from carbon-containing particles, graphite particles, and / or hard carbon particles, wherein the D of graphite and hard carbon particles is... 50 The particle size is in the range of 10 to 50 μm. More preferably, at least one additional particulate electroactive material is selected from graphite particles, wherein the D of the graphite particles is... 50 The particle size is in the range of 10 to 50 μm.

[0278] The composition may also be an unmixed (or “high-load”) electrode composition that is substantially free of additional particulate electroactive material. In this context, the term “substantially free of additional particulate electroactive material” should be interpreted as: based on the total dry weight of the composition, the composition contains less than 15 wt%, preferably less than 10 wt%, preferably less than 5 wt%, preferably less than 2 wt%, more preferably less than 1 wt%, and more preferably less than 0.5 wt% of any additional electroactive material (i.e., additional material capable of inserting and releasing metal ions during battery charging and discharging).

[0279] Based on the total dry weight of the composition, this type of "high-load" electrode composition preferably contains at least 50 wt%, or at least 60 wt%, or at least 70 wt%, or at least 80 wt%, or at least 90 wt% of composite particles.

[0280] The composition may optionally include an adhesive. The adhesive serves to adhere the composition to the current collector and maintain the integrity of the composition. Examples of adhesives include polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, carboxymethyl cellulose (CMC), modified carboxymethyl cellulose (mCMC), sodium carboxymethyl cellulose (Na-CMC), polyvinyl alcohol (PVA), alginate and its alkali metal salts, styrene-butadiene rubber (SBR), and polyimide. The composition may contain mixtures of adhesives. Preferably, the adhesive comprises a polymer selected from polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0281] Based on the total dry weight of the composition, the adhesive may suitably be present in amounts of 0.5 to 20 wt%, preferably 1 to 15 wt%, preferably 2 to 10 wt%, and most preferably 5 to 10 wt%.

[0282] The adhesive may optionally be used in combination with one or more additives that modify the properties of the adhesive, such as crosslinking accelerators, coupling agents and / or adhesion accelerators.

[0283] The composition may optionally include one or more conductive additives. Preferred conductive additives are non-electroactive materials included to improve conductivity between the electroactive components of the composition and between the electroactive components of the composition and the current collector. Conductive additives may be selected from carbon black, carbon fibers, carbon nanotubes, graphene, acetylene black, Ketjen black, metal fibers, metal powders, and conductive metal oxides. Preferred conductive additives include carbon black and carbon nanotubes.

[0284] Based on the total dry weight of the composition, one or more conductive additives may suitably be present in a total amount of 0.5 to 20 wt%, preferably 1 to 15 wt%, preferably 2 to 10 wt%, and most preferably 5 to 10 wt%.

[0285] The present invention also provides an electrode comprising composite particles. The electrode is typically in the form of a current collector, wherein the composite particles are in electrical contact with the current collector. The particulate material used to prepare the electrode may be in the form of a composition comprising composite particles and at least one other component as defined above.

[0286] As used herein, the term current collector refers to any conductive substrate capable of carrying current into and out of 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 foils or meshes with a thickness between 3 and 500 μm. Composite particles can be applied to one or both surfaces of the current collector to achieve a thickness preferably between 10 μm and 1 mm, for example, between 20 and 500 μm or between 50 and 200 μm.

[0287] The electrode can be prepared by mixing 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 the current collector and the solvent is removed, thereby forming an electrode layer on the surface of the current collector. Further steps may be performed, such as heat treatment for curing any adhesive and / or calendering of the electrode layer, as appropriate. The thickness of the electrode layer is suitably in the range of 20 μm to 2 mm, preferably 20 μm to 1 mm, preferably 20 μm to 500 μm, preferably 20 μm to 200 μm, preferably 20 μm to 100 μm, preferably 20 μm to 50 μm.

[0288] Alternatively, the slurry can be formed into a self-supporting film or pad containing the particulate material of the present invention, for example, by casting the slurry onto a suitable casting mold, removing the solvent, and then removing the casting mold. The resulting film or pad is in the form of a cohesive self-supporting material, which can then be bonded to a current collector by known methods.

[0289] The electrode can be used as the anode of a metal-ion battery. Therefore, the present invention provides a rechargeable metal-ion battery comprising an electrode serving as the anode. The metal ion is preferably a lithium ion. More preferably, the rechargeable metal-ion battery is a lithium-ion battery.

[0290] 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-based composite material. Examples of suitable cathode active materials include LiCoO2 and LiCo. 0.99 Al0.01 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, LiNi 0.4 Co 0.3 Mn 0.3 O2 and LiNi 0.33 Co 0.33 Mn 0.34 O2. The thickness of the cathode current collector is typically between 3 and 500 μm. Examples of materials that can be used as cathode current collectors include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0291] Electrolytes suitable for rechargeable metal-ion batteries include non-aqueous electrolytes containing lithium salts, and may include, but are not limited to, non-aqueous electrolyte solutions, organic solid electrolytes, and inorganic solid electrolytes. Examples of usable non-aqueous electrolyte solutions include aprotic organic solvents such as propylene carbonate, ethylene carbonate, butenyl carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, sulfolane, methyl sulfolane, and 1,3-dimethyl-2-imidazolium ketone.

[0292] Examples of organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate polymers, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociation groups.

[0293] Examples of inorganic solid electrolytes include lithium salt nitrides, halides, and sulfides, such as Li5NI2, Li3N, LiI, LiSiO4, Li2SiS3, Li4SiO4, LiOH, and Li3PO4.

[0294] Lithium salts are suitably soluble in a chosen solvent or a mixture of solvents. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO4, LiBF4, LiBC4O8, LiPF6, LiCF3SO3, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, and CF3SO3Li.

[0295] When the electrolyte is a non-aqueous organic solution, a separator is preferably disposed between the anode and cathode in a rechargeable metal-ion battery. The separator is typically made of an insulating material with high ion permeability and high mechanical strength. The pore diameter of the separator is typically between 0.01 and 100 μm, and the thickness is between 5 and 300 μm. Examples of suitable electrode separators include microporous polyethylene membranes. The separator can be replaced by a polymer electrolyte material, and in such cases, 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.

[0296] It should be understood that all process steps in this document are labeled for reference. Unless clearly incompatible, the steps may be performed in any order, with or without other intermediate steps. The descriptions below of particulate porous frameworks, silicon precursors, composite particles, electrodes, cells, etc., also apply to these items provided as the product itself or used as part of the process.

[0297] Example 1

[0298] Preparation and characterization of composite particles

[0299] The particulate porous carbon frameworks C1 to C13 used in this embodiment have the properties described in Tables 1 and 2. The composite particles prepared from these frameworks have the properties described in Table 3.

[0300] Table 1

[0301]

[0302] Table 2

[0303]

[0304] Table 3

[0305]

[0306] Prior to silicon deposition, the particle size, surface area, and pore structure parameters of the carbon framework were measured. The total volume of micropores and mesopores was determined using the 77 K nitrogen adsorption method and QSDFT as described herein.

[0307] Silicon-carbon composite particles were prepared by placing approximately 1.8 g of a granular porous framework with the properties listed in Table 1 on a stainless steel plate, maintaining a constant thickness of 1 mm along its length. The plate was then placed inside a 60 mm outer diameter stainless steel tube with gas inlet and outlet lines located in the hot zone of a muffle furnace. The furnace tube was purged with nitrogen for 30 minutes at room temperature, and the sample temperature was then increased to between 450 and 475 °C. The nitrogen flow rate was adjusted to ensure a residence time of at least 10 seconds in the furnace tube and maintained at this rate for 30 minutes. The gas supply was then switched from nitrogen to a mixture of silane (SiH4) at a concentration of 1.25 vol%. Silane feeding was carried out over a period of up to 5 hours while the reactor pressure was maintained at 101.3 kPa (1 atm). After feeding, the gas flow rate was kept constant while the silane was purged from the furnace using nitrogen. The furnace was purged with nitrogen for 30 minutes, followed by cooling to room temperature over several hours. Then, the atmosphere was gradually switched to air over a two-hour period by switching the airflow from nitrogen to air supplied by compressed air.

[0308] The surface silicon content of the composite particles was measured as follows: 10 mg (±2 mg) of the sample was placed in a 70 μL crucible. The sample was loaded into a Mettler Toledo TGA / DSC 3+ instrument, and Ar purge gas, N2 filling gas, and air reaction gas were introduced at a rate of 100 mL / min. The TGA furnace was heated from 25 °C to 1400 °C at a rate of 10 °C / min. Data were collected at 1-second intervals. The formula defined above was used to calculate the surface silicon (Y) value.

[0309] A series of composite particle samples with varying amounts of deposited silicon were prepared using each of the carbon frameworks. The average surface silicon of each framework was calculated based on the TGA curves of each sample in the framework series and is listed in Table 2. Figure 1 A plot of the average surface silicon of composite particles prepared from each of the porous carbon frameworks is shown relative to the VP07 measured for the framework prior to silicon deposition. It can be seen that, within certain limits of VP07, an increase in average surface silicon is achieved. The inventors have previously demonstrated that high surface silicon levels are associated with improved reversible capacity retention over multiple charge / discharge cycles. Figure 2 The diagram shows an average surface silicon plot of composite particles prepared from each of the porous carbon frameworks relative to VP20-VP5 measured against the framework prior to silicon deposition. Further improvements in average surface silicon are achieved within certain limits of VP20-VP5.

[0310] The surface area of ​​each sample in the frame series was plotted against the amount of silicon deposited, as determined by TGA. It was found that the amount of silicon is inversely proportional to the surface area. The amount of silicon at which the theoretical surface area is zero was extrapolated from the data points and is termed the maximum silicon content. The maximum silicon content represents the maximum amount of silicon that can be deposited within the frame pores before over-deposition occurs on the outer surface of the frame. It is believed that silicon deposition within the pores is advantageous, as expansion and contraction can be accommodated by the frame, rather than being deposited on the surface. Therefore, an increased maximum silicon content allows composite particles to have increased energy density by allowing an increased amount of silicon to be deposited within the frame pores, without the potentially harmful presence of silicon deposited on the outer surface of the frame. Figure 3 The maximum silicon content of the composite particles prepared from each of the frames is plotted relative to the VP07 measured for the frames prior to silicon deposition. A consistently high maximum silicon content value was observed when the VP07 value was below 40%.

[0311] Therefore, frameworks with optimized volumetric pores (pore diameter of 0.7 nm or less) can form composite particles with advantageous properties for use as electroactive materials in LIBs, including a good balance between average surface silicon and maximum silicon content.

[0312] Example 2

[0313] Preparation and characterization of particulate porous frameworks

[0314] The following example demonstrates the fabrication of particulate porous frameworks with customized pore structures.

[0315] All synthetic activated carbons reported below were prepared from a mixture of phenolic varnish resin and 11% hexamethylenetetramine powder (Bakelite PF 6705 FP, Hexion GmbH). This starting material was crosslinked at 150°C for 1 h, and the crosslinked solid mass was hammered into 2–3 cm pieces, which were then ground into particles of approximately 100 μm. This cured resin powder was then carbonized at 800°C under a nitrogen flow of 1 L / min for 10 min. The carbon yield obtained from this precursor was 57–59%. Coconut shell raw materials were carbonized within a similar temperature range (700–1000°C), where the carbon yield decreased (typically 20–30% w / w). After carbonization, the carbon was ball-milled to a particle size of 3–4 μm, and the total pore volume of the resulting carbon material was 0.25–0.3 cm³. 3 / g, including 0.20–0.22 cm 3 Microporosity of / g and 650–700 m 2 / g surface area. This carbon is then activated in steam or CO2 to achieve a desired pore volume. CO2 activation is used to achieve 0.8–0.9 cm².3 Typical activation temperatures for / g total pore volume are 950-980℃, with residence times of 5-8 h, depending on the amount of carbon being activated, the CO2 flow rate, and the type of furnace used. Because steam is more reactive, steam activation is performed at lower temperatures than CO2, typically 850℃. In laboratory-scale synthesis, the residence time of steam at the activation temperature is typically 6-9 h, depending on the type and amount of carbon being activated, the steam flow rate, and the type of furnace used. In a further example, KOH is used for activation, with a KOH to carbonized feedstock ratio of 4:1, which is then washed away after activation.

[0316] Table 4

[0317]

[0318] The results in the table indicate that VP07 can be customized through combinations of activation chemistry, activation conditions, and carbon feedstock. Specifically, CO2 activation of the synthesis feedstock enhances VP07. Steam activation of biomass tends to result in pore widening and a decrease in VP07 for the same pore volume. Chemical activation can also be used in a similar manner to CO2 activation to achieve moderate or high VP07 values. VP07 can be manipulated while maintaining desirable values ​​in the VP20–VP5 range.

[0319] Additionally, by using different framework chemistry, the VP20-VP5 parameters can be modified while maintaining a desirable VP07 value, using an ethylene glycol co-solvent to manipulate the mesopore size distribution and volume fraction. An example of the VP20-VP5 parameter manipulation procedure is as follows:

[0320] i. Provide phenolic varnish resin + hexamine

[0321] ii. Dissolved in pore-forming agent (ethylene glycol)

[0322] iii. Curing at 150°C for 1 hour

[0323] iv. Wash with hot water and then dry.

[0324] v. to carbonize at 800°C

[0325] vi. Activated to different levels

[0326] Table 5

[0327]

[0328] Samples 8, 10, and 11 were prepared using the same starting formulation, consisting of 100 g of phenolic varnish resin and hexamethylenetetramine mixed with 150 g of ethylene glycol. Sample 9 contained the same amount of resin and hexamethylenetetramine, but 100 g less ethylene glycol. The mixture was cured in air in an oven at 150 °C for 1 hour, with a heating rate of 1 °C / min and held at 100 °C for 1 hour.

[0329] After curing, the samples were pulverized and granulated, and then washed with warm deionized water to remove ethylene glycol. They were then dried overnight at 90°C and carbonized at 800°C with a nitrogen flow rate of 1°C / min, thereby 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 and CO2 for approximately 3 hours to achieve the desired total pore volume. A smaller amount of pore-forming agent can be used to further reduce VP20-VP5.

[0330] Example 3

[0331] Preparation and characterization of composite particles

[0332] The particulate porous carbon frameworks C14 to C18 used in this embodiment have the properties described in Tables 6 and 7. The composite particles prepared from these frameworks have the properties described in Table 8.

[0333] Table 6

[0334]

[0335] Table 7

[0336]

[0337] Table 8

[0338]

[0339] Prior to silicon deposition, the particle size, surface area, and pore structure parameters of the carbon framework were measured.

[0340] Silicon-carbon composite particles were prepared using a 0.6 L volumetric pressure reactor system according to the following procedure. First, 25 g of granular porous framework with the properties listed in Tables 6 and 7 was weighed and loaded into the reactor chamber, which was then sealed, inertized, and pressure-tested using nitrogen. The reactor was then heated to 320–350 °C while stirring at 200 rpm. Silane gas was then injected, and the furnace setpoint was raised to 550 °C. Silane was injected in four pulses, totaling 27 g, with a pressure setpoint between 9–12 bar for each cycle. The completion of the reaction under each pulse was determined by pressure monitoring—pressure stability was used to determine the completion of the conversion of silane to silicon on carbon. After each silane injection, the reactor was again inertized with nitrogen. Subsequently, sixty passivation cycles were performed at 150 °C using air in a nitrogen atmosphere with increasing concentrations until the temperature and pressure stabilized at 100% air after each injection. These steps resulted in the growth of a silica passivation layer on the outer surface of the composite particles. The resulting composite powder was then recovered by breaking the reactor seal and sieving the recovered composite powder through a 53 μm sieve.

[0341] The amount of silicon in the composite particles was determined using TGA. The mass of the composite particle sample was measured in air using a TGA instrument until complete oxidation was achieved at approximately 1400°C. It was assumed that the composite particles consisted only of carbon, silicon, and oxygen. It was assumed that the mass after oxidation was only SiO2, thus determining the silicon content of the initial composite particles. Determination of the silicon content of composite particles prepared from each of C14-C18 by TGA demonstrated that the deposited silicon was sufficient to allow the composite particles to be used as an anode material for lithium-ion batteries.

[0342] The surface silicon content of the composite particles was measured as follows: 10 mg (±2 mg) of the sample was placed in a 70 μL crucible. The sample was loaded into a Mettler Toledo TGA / DSC 3+ instrument, and Ar purge gas, N2 filling gas, and air reaction gas were introduced at a rate of 100 mL / min. The TGA furnace was heated from 25 °C to 1400 °C at a rate of 10 °C / min. Data were collected at 1-second intervals. The formula defined above was used to calculate the surface silicon (Y) value.

[0343] Figure 4 and Figure 5 Surface silicon plots of composite particles prepared from each of the porous carbon frameworks are shown, relative to VP07 and VP20-VP5 as measured against the framework prior to silicon deposition. A favorable higher value was observed for the composite particles prepared from C14-C17.

[0344] Example 4

[0345] Preparation and characterization of composite particles

[0346] The particulate porous carbon frameworks C19 to C27 used in this embodiment have the properties described in Tables 9 and 10. The composite particles prepared from these frameworks have the properties described in Table 11.

[0347] Table 9

[0348]

[0349] Table 10

[0350]

[0351] Table 11

[0352]

[0353] Prior to silicon deposition, the particle size, surface area, and pore structure parameters of the carbon framework were measured.

[0354] Silicon-carbon composite particles were prepared and characterized using the same procedure as in Example 3.

[0355] Figure 6 and Figure 7 Surface silicon plots of composite particles prepared from each of the porous carbon frameworks are shown, relative to VP07 and VP20-VP5 as measured against the framework prior to silicon deposition. A favorable higher value was observed for the composite particles prepared from C19-C24.

Claims

1. Composite particles used as electroactive materials in metal-ion batteries, said composite particles comprising: Particulate porous frameworks including micropores and optionally mesopores; as well as Electroactive material domains located within the pores of the granular porous framework; wherein: P1 is the total volume of micropores and mesopores in the granular porous framework, expressed in cm. 3 / g indicates that P1 is at least 0.35; and VP07 is the volume of pores with a pore diameter of 0.7 nm or smaller in the granular porous framework, expressed as a percentage of P1, wherein VP07 is in the range of 5.1-40%; P1 and VP07 were measured by nitrogen adsorption method.

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

3. The composite particles as claimed in any of the preceding claims, wherein the micropore volume of the particulate porous framework is at least 0.3 cm³. 3 / g, or at least 0.4 cm 3 / g, or at least 0.5 cm 3 / g, or at least 0.6 cm 3 / g.

4. The composite particles as claimed in any of the preceding claims, wherein VP1 is the volume of pores with a pore diameter of 1.0 nm or less in the particulate porous framework as measured by nitrogen adsorption, expressed as a percentage of P1, wherein VP1 is at least 1.5 × VP07 or at least 2 × VP07.

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

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

7. The composite particles according to any one of claims 1 to 5, wherein VP2 is the volume of pores with a pore diameter of 2.0 nm or less in the particulate porous framework as measured by nitrogen adsorption, expressed as a percentage of P1, wherein VP2 is less than 50%, or not more than 45%, or not more than 40%.

8. The composite particles as claimed in any of the preceding claims, wherein VP5 is the volume of pores with a pore diameter of 5.0 nm or less in the particulate porous framework as measured by nitrogen adsorption, expressed as a percentage of P1, wherein 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 composite particles according to any of the preceding claims, wherein the volume of the pores with a diameter of 0.7 nm or less in the particulate porous framework is at least 0.05 cm³. 3 / g, or 0.08-0.5 cm 3 / g, or 0.1-0.3 cm 3 / g.

10. The composite particles as claimed in any of the preceding claims, wherein VP20 is the volume of pores with a pore diameter of 20.0 nm or less in the particulate porous framework, expressed as a percentage of P1, wherein VP20 is at least 80%, or at least 90%, or at least 95%, or at least 97%, or at least 98%; wherein VP20 is measured by nitrogen adsorption.

11. The composite particles as claimed in any of the preceding claims, wherein VP20 and VP5 are the volumes of pores with pore diameters of 20.0 nm or less and 5.0 nm or less, respectively, in the particulate porous framework, expressed as a percentage of P1, wherein 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%; wherein VP20 and VP5 are measured by nitrogen adsorption.

12. The composite particles as claimed in any of the preceding claims, wherein VP10 is the volume of pores with a pore diameter of 10.0 nm or less in the particulate porous framework, expressed as a percentage of P1, wherein VP10 is at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 97%; wherein VP10 is measured by nitrogen adsorption.

13. The composite particles as claimed in any of the preceding claims, wherein P1 is 0.4-1.8, or 0.5-1.6, or 0.6-1.

2.

14. The composite particles as claimed in any of the preceding claims, wherein P2 is the total volume of pores in the particulate porous framework with diameters in the range of >50-100 nm, expressed in cm⁻¹ 3 / g indicates that P2 is <0.2×P1, or <0.05×P1, or <0.005×P1.

15. The composite particles as claimed in any of the preceding claims, wherein P2 is the total volume of pores in the particulate porous framework with diameters in the range of >50-100 nm, expressed in cm⁻¹ 3 / g represents the total volume of micropores, mesopores, and pores with diameters in the range of >50-100 nm, which is <15%, <10%, <8%, or <5%.

16. The composite particles as claimed in any of the preceding claims, wherein the particulate porous framework comprises a bimodal or multimodal pore size distribution.

17. The composite particles as claimed in any of the preceding claims, wherein the D of the composite particles 50 The particle size is no greater than 100 μm, or no greater than 30 μm, or 1-30 μm, or 1-20 μm, or 2-8 μm, as measured by laser diffraction.

18. The composite particles as claimed in any of the preceding claims, wherein the particle size distribution span (D) of the composite particles is... 98 -D1) / D 50 The value is less than 2, as measured by laser diffraction.

19. The composite particles as claimed in any of the preceding claims, wherein the PD of the particulate porous framework is... 90 The pore diameter is no greater than 25 nm, or 1-20 nm, or 1.5-10 nm, or 2-9 nm; wherein the PD 90 The pore diameter is such that, as measured by nitrogen adsorption, the pore diameter of 90% of the total micropore and mesopore volume is lower than its pore diameter.

20. The composite particles as claimed in any of the preceding claims, wherein the PD of the particulate porous framework is... 50 The pore diameter is no greater than 4 nm, no greater than 3 nm, or 1-2.5 nm; wherein the PD 50 The pore diameter is such that, as measured by nitrogen adsorption, the pore diameter of 50% of the total micropore and mesopore volume is lower than its pore diameter.

21. The composite particles as claimed in any of the preceding claims, wherein the BET surface area of ​​the particulate porous framework is at least 750 m². 2 / g, or at least 1,000 m 2 / g or 1,000-3,000 m 2 / g.

22. The composite particles according to any of the preceding claims, wherein the granular porous framework is composed of titanium nitride, titanium carbide, silicon carbide, boron carbide, nickel oxide, silicon oxide, silicon dioxide, aluminum oxide, aluminum silicon ternary oxide, magnesium oxide, lead oxide, zirconium oxide, silicon nitride, titanium silicon nitride, nickel nitride, molybdenum nitride, titanium oxynitride, silicon carbide, boron nitride, or vanadium nitride; or wherein the granular porous framework is composed of titanium nitride, silicon carbide, or boron nitride.

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

24. The composite particles of claim 23, wherein the ratio of the relative intensities of the D peak and the G peak of the particulate porous carbon framework, as measured by Raman spectroscopy, is (I0) D / I G The values ​​are ≥0.6, ≥0.8, ≥1, ≥1.05 and / or ≤2.0 or ≤1.

8.

25. The composite particles of any of the preceding claims, wherein the granular porous framework is composed of pyrolytic carbon; optionally, the pyrolytic carbon is derived from plants, or pyrolytic bitumen, or pyrolytic polymers, or pyrolytic resins.

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

27. The composite particles according to any of the preceding claims, comprising 20-80 wt% of the electroactive material, or 30-70 wt% of the electroactive material, or 40-60 wt% of the electroactive material.

28. The composite particles according to any of the preceding claims, wherein the electroactive material is silicon, wherein, as determined by thermogravimetric analysis (TGA), at least 10 wt%, or at least 20 wt%, or at least 25 wt%, or at least 30 wt%, or at least 35 wt% of the silicon is surface silicon.

29. The composite particles according to any of the preceding claims, wherein the electroactive material is silicon, wherein, as determined by TGA, no more than 10 wt%, or no more than 8 wt%, or no more than 6 wt%, or no more than 5 wt%, or no more than 4 wt%, or no more than 3 wt%, or no more than 2 wt%, or no more than 1.5 wt% of the silicon is crude bulk silicon.

30. The composite particles of any of the preceding claims, wherein at least 70 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, or 98 wt% of the electroactive material in the composite particles are located within the internal pore volume of the particulate porous framework.

31. The composite particles as claimed in any of the preceding claims, wherein the nitrogen-accessible pore volume of the composite particles is less than 0.05 × P1.

32. The composite particles as claimed in any of the preceding claims, wherein the total volume of micropores and mesopores in the composite particles is less than 0.03 cm³. 3 / g or less than 0.01 cm 3 / g.

33. The composite particles as claimed in any of the preceding claims, wherein the BET surface area of ​​the composite particles is less than 50 m². 2 / g, or less than 30 m 2 / g, less than 20 m 2 / g, or less than 15 m 2 / g, or less than 10 m 2 / g.

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

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

36. A process for preparing composite particles as described in any one of claims 1 to 33, the process comprising the following steps: (a) Providing a granular porous framework as defined by any one of claims 1 to 33; as well as (b) Depositing electroactive material domains in the pores of the particulate porous framework.

37. The process of claim 36, wherein step (b) comprises contacting the particulate porous framework with the electroactive material precursor at a temperature sufficient to deposit the electroactive material domain in the pores of the particulate porous framework.

38. The process of claim 37, wherein the electroactive material precursor is gaseous.

39. The process of claim 38, wherein the electroactive material precursor is a silicon precursor; optionally, the silicon precursor is selected from silane (SiH4), disilane (Si2H6), trisilane (Si3H8), and tetrasilane (Si4H6). 10 ), pentasilane (Si5H) 12 ), hexasilane (Si6H) 14 ), methylsilane (CH3SiH3), dimethylsilane ((CH3)2SiH2), trimethylsilane ((CH3)3SiH), tetramethylsilane ((CH3)4Si), and chlorosilane, such as trichlorosilane (HSiCl3) or dichlorosilane (H2SiCl2) or chlorosilane (H3SiCl), or methylchlorosilane, such as methyltrichlorosilane (CH3SiCl3) or dimethyldichlorosilane ((CH3)2SiCl2); optionally, the silicon precursor is silane (SiH4).

40. The process of any one of claims 36 to 39, wherein step (b) is carried out at a pressure of at least 150 kPa or at least 200 kPa, optionally not exceeding 5,000 kPa.

41. A process comprising the following steps: (a1) Provide one or more groups of granular porous frameworks comprising micropores and optionally mesopores; (a2) Measure the pore structure of each population; (a3) Accept each group having an optimized pore structure and reject each group not having the optimized pore structure, wherein in the optimized pore structure: P1 is the total volume of micropores and mesopores in the granular porous framework, expressed in cm. 3 / g indicates that P1 is at least 0.35; and VP07 is the volume of pores with a pore diameter of 0.7 nm or smaller in the granular porous framework, expressed as a percentage of P1, wherein VP07 is in the range of 5.1-40%; P1 and VP07 were measured by nitrogen adsorption method; (b) Depositing electroactive material domains into the pores of a recognized population of particulate porous frameworks.

42. The process of claim 41, wherein at least two groups are provided in step (a1), and optionally at least one of the groups is rejected in step (a3).

43. The process of claim 41 or claim 42, comprising the following steps: (a4) Providing an industrial-scale population of a recognized group of granular porous frameworks, optionally wherein said industrial-scale population comprises at least 100 kg or at least 1000 kg of said recognized granular porous frameworks; and (b) Depositing electroactive material domains into the pores of the industrial-scale population of the recognized particulate porous framework.

44. A granular porous framework comprising micropores and optionally mesopores; wherein: P1 is the total volume of micropores and mesopores in the granular porous framework, expressed in cm. 3 / g indicates that P1 is at least 0.35; and VP07 is the volume of pores with a pore diameter of 0.7 nm or smaller in the granular porous framework, expressed as a percentage of P1, wherein VP07 is in the range of 5.1-40%; P1 and VP07 were measured by nitrogen adsorption method.

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