Method for preparing electroactive materials for metal-ion batteries

Abstract

This invention relates to a method for preparing composite particles. The method includes: a first step of providing a plurality of porous particles comprising micropores and / or mesopores, wherein the total pore volume of the micropores and mesopores, measured by nitrogen adsorption, is between 0.4 and 2.2 cm³. 3 Within the range of / g. The porous particles are brought into contact with a precursor of the electroactive material at a temperature that effectively induces the deposition of the electroactive material in the pores of the porous particles to form intermediate particles. The deposition of the electroactive material is interrupted, and optionally, byproducts are separated from the intermediate particles. The intermediate particles are then brought into contact with a precursor of the electroactive material at a temperature that effectively induces further deposition of the electroactive material in the pores of the intermediate particles to form composite particles. In at least one of the deposition steps, the reactor pressure is maintained below 200 kPa.

Description

[0001] The present invention generally relates to a method for preparing electroactive materials suitable for use in electrodes of rechargeable metal-ion batteries, and more specifically to particulate materials with high electrochemical capacity suitable for use as anodic active materials in rechargeable metal-ion batteries.

[0002] Rechargeable metal-ion batteries are widely used in portable electronic devices, such as mobile phones and laptops, and are increasingly being applied to electric vehicles or hybrid vehicles. Rechargeable metal-ion batteries typically include an anode in the form of a metal current collector having a layer of electroactive material, defined herein as a material capable of inserting and releasing metal ions during battery charging and discharging. The terms "cathode" and "anode" are used herein in the context of connecting the battery to a load such that the anode is the negative electrode. When a metal-ion battery is charged, metal ions are transported from the metal-ion-containing cathode layer to the anode via the electrolyte and inserted into the anode material. The term "battery" herein refers both to a device containing a single anode and a single cathode and to a device containing multiple anodes and / or multiple cathodes.

[0003] Interestingly, improving the gravimetric and / or volumetric capacity of rechargeable metal-ion batteries is crucial. To date, commercial lithium-ion batteries have been largely limited by the use of graphite as the anode active material. When a graphite anode is charged, lithium is intercalated between the graphite layers to form an empirically defined Lia. x Materials with C6 content (where x is greater than 0 and less than or equal to 1) are used. Therefore, the maximum theoretical capacity of graphite in lithium-ion batteries is 372 mAh / g, with a slightly lower actual capacity (approximately 340 to 360 mAh / g). Other materials such as silicon, tin, and germanium can intercalate lithium at significantly higher capacities than graphite, but they have not yet been widely used commercially due to their difficulty in maintaining sufficient capacity during multiple charge / discharge cycles.

[0004] In particular, silicon is considered a promising alternative to graphite for manufacturing rechargeable metal-ion batteries with high gravimetric and volumetric capacity due to its very high lithium capacity (see, for example, Insertion Electrode Materials for rechargeable Lithium Batteries, Winter, M et al., Adv. Mater. 1998, 10, No. 10). At room temperature, the theoretical maximum specific capacity of silicon in lithium-ion batteries is approximately 3,600 mAh / g (based on Li). 15(Si4). However, when silicon is lithiated to its maximum capacity, lithium insertion into the bulk silicon causes a significant increase in the volume of the silicon material, reaching up to 400% of its original volume. Repeated charge-discharge cycles create significant mechanical stress in the silicon material, leading to breakage and delamination of the silicon anode material. The volume shrinkage of silicon particles during delithiation can result in loss of electrical contact between the anode material and the current collector. Another challenge is that the solid electrolyte interface (SEI) layer formed on the silicon surface lacks sufficient mechanical tolerance to accommodate the expansion and contraction of silicon. As a result, the newly exposed silicon surface leads to further electrolyte decomposition and increased SEI layer thickness, as well as irreversible lithium consumption. These destructive mechanisms collectively result in unacceptable electrochemical capacity loss during continuous charge-discharge cycles.

[0005] Several methods have been proposed to overcome the problems associated with the volume changes observed during charging of silicon-containing anodes. Microcrystalline silicon structures with cross-sections below approximately 150 nm, such as silicon films and silicon nanoparticles, have been reported to be more tolerant of volume changes during charging and discharging compared to silicon particles in the micrometer range. However, none of these are suitable for commercial-scale applications in their unrefined form; nanoscale particles are difficult to fabricate and process, and silicon films do not provide sufficient bulk capacity.

[0006] WO 2007 / 083155 discloses that improved capacity retention can be achieved using silicon particles with a high aspect ratio (i.e., the ratio of the maximum to the minimum particle size). The small cross-section of such particles reduces structural stress on the material due to volume changes during charging and discharging. However, the fabrication of such particles can be difficult and expensive, and they may be brittle. Furthermore, the high surface area can lead to excessive SEI formation, resulting in excessive capacity loss during the first charge-discharge cycle.

[0007] It is also generally known that electroactive materials, such as silicon, can be deposited within the pores of porous support materials, such as activated carbon. These composite materials provide some of the beneficial charge-discharge properties of nanoscale silicon particles while avoiding the handling difficulties of nanoparticles. Guo et al. (Journal of Materials Chemistry A, 2013, pp. 14075-14079) disclosed a silicon-carbon composite material in which a porous carbon substrate provides a conductive framework, and silicon nanoparticles are deposited in the uniformly distributed pore structure of the substrate. The composite material is known to have improved capacity retention over multiple charge cycles, but the initial capacity (in mAh / g) of the composite material is significantly lower than that of the silicon nanoparticles.

[0008] The inventors previously reported the development of a class of electroactive materials with a composite structure in which nanoscale electroactive materials (such as silicon) are deposited into a pore network of highly porous particulate materials (such as porous carbon materials).

[0009] For example, WO 2020 / 095067 and WO 2020 / 128495 report that the improved electrochemical performance of these materials can be attributed to the way that the electroactive materials are located in the form of small structural domains on the order of several nanometers within a porous material. These fine electroactive structures are thought to have lower resistance to elastic deformation and higher fracture resistance compared to larger electroactive structures, thus enabling lithiation and delithiation without excessive structural stress. As a result, the electroactive material exhibits good reversible capacity retention over multiple charge-discharge cycles. Secondly, by controlling the silicon loading within the porous carbon framework, such that only a portion of the pore volume is occupied by silicon in the uncharged state, the unoccupied pore volume of the porous carbon framework can accommodate a significant amount of silicon expansion internally. Furthermore, as described above, by locating nanoscale silicon structural domains within small mesopores and / or micropores, only a small area on the silicon surface is accessible to the electrolyte, thus limiting SEI formation. This largely prevents additional silicon exposure in subsequent charge-discharge cycles, thus making SEI formation not a significant destructive mechanism leading to capacity loss. This contrasts sharply with the excessive SEI formation characteristic of materials disclosed by, for example, Guo (see above).

[0010] The materials described in WO 2020 / 095067 and WO 2020 / 128495 have been synthesized by chemical vapor infiltration (CVI) in various reactor systems (stationary, rotary, and FBR). The porous particles were contacted with a silicon-containing precursor stream (CVI) (typically silane gas) at atmospheric pressure and temperatures ranging from 400 to 700 °C.

[0011] There is still a need in the field for improved methods for preparing electroactive materials with improved properties.

[0012] In a first aspect, the present invention provides a method for preparing composite particles, the method comprising the following steps:

[0013] (a) Provides multiple porous particles comprising micropores and / or mesopores, wherein the total pore volume of micropores and mesopores, as measured by nitrogen adsorption, is between 0.4 and 2.2 cm³. 3 Within the range of / g;

[0014] (b) The porous particles are brought into contact with the precursor of the electroactive material at a temperature that effectively causes the electroactive material to deposit in the pores of the porous particles to form intermediate particles;

[0015] (c) Interrupt the deposition of the electrochemical material and optionally separate the byproducts from the intermediate particles;

[0016] (d) The intermediate particles from step (c) are brought into contact with the precursor of the electroactive material at a temperature that effectively causes further deposition of the electroactive material in the pores of the intermediate particles to form composite particles.

[0017] In at least one of steps (b) and (d), the reactor pressure is kept below 200 kPa.

[0018] Therefore, the present invention generally relates to a method for preparing composite particulate materials, wherein an electroactive material is deposited into the pores of a porous particulate material in at least two separate steps. The initial deposition of the electroactive material is carried out in step (b), and further deposition of the electroactive material is carried out in step (d). Optionally, steps (c) and (d) may be repeated multiple times, such that the method of the present invention includes depositing the electroactive material through three or more steps.

[0019] Steps (b) and (d) use chemical vapor infiltration (CVI) of the electroactive materials to deposit a first and a second electroactive material layer onto the pore surface of the porous particles. Chemical vapor infiltration (CVI) is a process of infiltrating a porous material with another phase, typically performed by contacting a reactive gaseous precursor with the porous material at high temperature. The decomposition / reaction of the reactive gaseous precursor on the pore surface leads to the deposition of a solid phase within the pores.

[0020] By depositing electroactive materials in multiple steps, the deposition of electroactive materials is interrupted by one or more steps (step (c)) in which the deposition of electroactive materials is interrupted. When compared with a process that deposits all electroactive materials in a single step, the interruption of the deposition of electroactive materials in the middle stage of the overall deposition allows for a variety of improvements.

[0021] First, the deposition of electroactive materials in at least two distinct steps allows for the use of different deposition conditions in each step. This allows for better control of the CVI process at different stages of the overall deposition. The deposition of electroactive materials during the CVI process occurs on the surface of porous particles. Given the very high internal surface area of ​​porous particles, the reaction kinetics favor the deposition of electroactive materials that are deposited almost entirely within the pores of the porous particles.

[0022] However, a crucial factor controlling the deposition of electroactive materials is mass transfer from the particle exterior to the deposition site. When mass transfer becomes a limiting factor in the CVI process, the electroactive material may deposit in larger pores or on the outer surface of the electroactive material. Furthermore, the deposited electroactive material may then block access to smaller pore spaces where the electroactive material would ideally be deposited. Performing at least one of steps (b) and (d) at a pressure below 200 kPa results in increased diffusivity of the electroactive material precursor, enabling it to enter micropores and / or minimal mesopores prior to thermal decomposition. Therefore, controlling the pressure of at least one of steps (b) and (d) as described herein allows for improved control over the deposition of the electroactive material.

[0023] Secondly, the interruption of electroactive material deposition in the intermediate stage allows for additional process steps between consecutive electroactive material depositions. An advantageous process step includes separating the intermediate particles formed in step (b), i.e., separating the byproducts from the intermediate particles formed in step (b). When electroactive material deposition is performed in a single step, byproducts need to diffuse out of the pore volume of the porous particles simultaneously while the precursors of the electroactive material need to diffuse into the pore volume. Therefore, byproduct removal is inefficient, and byproducts may be incorporated into the deposited electroactive material, leading to impaired electrochemical performance. The interruption of electroactive material deposition provides an opportunity for byproducts to diffuse out of the porous particles and be removed before continued deposition. As a result, the quality of the deposited material is improved, leading to improved electrochemical performance when composite particles are incorporated into the electrode.

[0024] The interruption of electroactive material deposition in the intermediate stage also allows for the formation of other materials on the surface of the electroactive material deposited in step (b). These materials are generally referred to herein as “modified materials.” A suitable modified material may include a material formed by chemically modifying the surface of the electroactive material deposited in step (b). Another suitable modified material may include another deposited material, wherein the deposited material is electroactive. Modified materials can create at least a partial barrier between the electroactive materials deposited in steps (b) and (d). As a result, the length scale of any continuous electroactive material domain can be limited by the intervening domains of the modified material. It has been found that larger electroactive material domains lead to poorer electrochemical performance. Therefore, using modified materials to interrupt electroactive material domains allows for control over the length scale of individual electroactive material domains while still allowing for a high total content of electroactive material in the composite particles.

[0025] Porous particles act as a framework for electroactive materials, which are typically deposited in the form of multiple electroactive material domains. The term "electroactive material domain" refers to a bulk electroactive material, such as elemental silicon, having a maximum size determined by the size of the micropores and / or mesopores of the porous particles in which it resides. Therefore, electroactive domains can be described as nanoscale electroactive domains, where the term "nanoscale" is generally understood to mean a size less than 100 nm. However, due to the size of the micropores and mesopores, the maximum size of an electroactive material domain in any direction is less than 50 nm, and is typically significantly smaller than 50 nm. Domains can take the form, for example, regular or irregular particles or bounded layers or regions of a coating.

[0026] The porous particles preferably contain a conductive material. The use of conductive porous particles is advantageous because the porous particles form a conductive framework within the composite particles, which facilitates electron flow between lithium atoms / ions embedded in the electroactive material and the current collector.

[0027] A preferred conductive porous particle is a particle containing or composed of conductive carbon material, which is referred to herein as conductive porous carbon particle.

[0028] The conductive porous carbon particles preferably contain at least 80% by weight of carbon, more preferably at least 90% by weight of carbon, even more preferably at least 95% by weight of carbon, and optionally at least 98% by weight or at least 99% by weight of carbon. The carbon can be crystalline carbon or amorphous carbon, or a mixture of amorphous carbon and crystalline carbon. The porous carbon particles can be hard carbon particles or soft carbon particles.

[0029] As used in this paper, the term "hard carbon" refers to a disordered carbon matrix in which carbon atoms are found to be primarily sp(s) in nanoscale polyaromatic domains. 2 Hybridized state (triple bond). Polyaromatic domains are cross-linked using chemical bonds such as COC bonds. Due to the chemical cross-linking between polyaromatic domains, hard carbon cannot be converted to graphite at high temperatures. Hard carbon exhibits graphitic properties, as evidenced by the large G band (~1600 cm⁻¹) in its Raman spectrum. -1 This is evidenced by the fact that the carbon is not entirely graphitic, as evidenced by the distinct D band (~1350 cm⁻¹) in the Raman spectrum. -1 )prove.

[0030] As used in this article, the term "soft carbon" also refers to such a disordered carbon matrix in which carbon atoms are found to be predominantly sp. 2Hybridized states (triple bonds) are found in polyaromatic domains ranging from 5 to 200 nm in size. Compared to hard carbon, the polyaromatic domains in soft carbon are associated through intermolecular forces rather than cross-linked by chemical bonds. This means they will graphitize at high temperatures. Porous carbon particles preferably contain at least 50% sp. 2 Hybridized carbon (measured by XPS). For example, porous carbon particles can suitably contain 50% to 98% sp. 2 Hybridized carbon, 55% to 95% sp 2 Hybridized carbon, 60% to 90% sp 2 Hybridized carbon, or 70% to 85% sp 2 Hybridized carbon.

[0031] Suitable porous carbon particles can be prepared by pyrolysis using a wide variety of different materials. Examples of organic materials that can be used include plant biomass, including lignocellulosic materials (such as coconut shells, rice husks, wood, etc.), and fossil carbon sources such as coal. Examples of resins and polymers that form porous carbon particles during pyrolysis include phenolic resins, phenolic varnish resins, bitumen, melamine-based materials, polyacrylate-based materials, polystyrene-based materials, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers containing monomer units of acrylate monomers, styrene monomers, α-olefins, vinylpyrrolidone, and other olefinically unsaturated monomers. Depending on the raw materials and conditions of the pyrolysis process, a wide variety of carbon materials are available in the art. Porous carbon particles of various specifications are available from commercial suppliers.

[0032] Porous carbon particles can undergo chemical or gas-based activation processes to increase the volume of mesopores and micropores. Suitable activation processes involve contacting pyrolytic carbon with one or more of oxygen, water vapor, CO, CO2, and KOH at temperatures ranging from 600 to 1000 °C.

[0033] Mesoporous structures can also be obtained through known templated processes using removable pore-forming agents such as MgO and other colloidal or polymeric templates (which can be removed by thermal or chemical means after pyrolysis or activation).

[0034] Alternatives to carbon-based conductive particles include porous particles containing the following: titanium nitride (TiN), titanium carbide (TiC), silicon carbide (SiC), nickel oxide (NiOx), titanium silicon nitride (TiSiN), nickel nitride (Ni3N), molybdenum nitride (MoN), and titanium oxynitride (TiO2). x N 1-x The porous particles may contain titanium nitride (TiN), silicon carbide (SiOC), boron nitride (BN), or vanadium nitride (VN). Preferably, the porous particles comprise titanium nitride (TiN), silicon carbide (SiOC), or boron nitride (BN).

[0035] Porous particles comprise a three-dimensional interconnected open network, which includes micropores and / or mesopores, as well as optionally small-volume macropores. According to standard 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.

[0036] The mention of the volume of micropores, mesopores, and macropores in porous particles, as well as any mention of the distribution of pore volume within porous particles, refers to the internal pore volume of the porous particles used as starting materials in step (a) of the claimed method (i.e., prior to the deposition of electroactive material into the pore volume in step (b)).

[0037] Porous particles are characterized by a particle size ranging from 0.4 to 2.2 cm. 3 The total volume of micropores and mesopores in the range of / g (i.e., the total pore volume in the particle size range of 0 to 50 nm). Typically, porous particles include both micropores and mesopores. However, the use of porous particles that include micropores but not mesopores, or porous particles that include mesopores but not micropores, is not excluded.

[0038] More preferably, the total volume of micropores and mesopores in the porous particles is at least 0.45 cm³. 3 / g, or at least 0.5cm 3 / g, or at least 0.55cm 3 / g, or at least 0.6cm 3 / g, or at least 0.65cm 3 / g, or at least 0.7cm 3 / g, or at least 0.75cm 3 / g, or at least 0.8cm 3 / g, or at least 0.85cm 3 / g, or at least 0.9cm 3 / g, or at least 0.95cm 3 / g, or at least 1cm 3 / g. The use of high-porosity particles can be advantageous because it allows for the containment of larger amounts of electroactive materials within the pore volume.

[0039] The internal pore volume of porous particles is suitably limited to a value where the increased brittleness of the particle structure outweighs the advantage of the increased pore volume for accommodating a larger amount of electroactive material. Preferably, the total volume of micropores and mesopores in the porous particles does not exceed 2 cm³. 3 / g, or not exceeding 1.8cm 3 / g, or not exceeding 1.6cm 3 / g, or not exceeding 1.5cm3 / g, or not exceeding 1.45cm 3 / g, or not exceeding 1.4cm 3 / g, or not exceeding 1.35cm 3 / g, or not exceeding 1.3cm 3 / g, or not exceeding 1.25cm 3 / g, or not exceeding 1.2cm 3 / g, or not more than 1.1, or not more than 1, or not more than 0.95.

[0040] Preferably, the total volume of micropores and mesopores in the porous particles is between 0.45 and 2.2 cm³. 3 / g, or 0.5 to 2cm 3 / g, or 0.55 to 2cm 3 / g, or 0.6 to 1.8cm 3 / g, or 0.65 to 1.8cm 3 / g, or 0.7 to 1.6cm 3 / g, or 0.7 to 1.5cm 3 / g, or 0.7 to 1.4cm 3 Within the range of / g.

[0041] The total volume of micropores and mesopores in porous particles can also range from 0.55 to 1.4 cm³. 3 / g, or 0.6 to 1.4cm 3 / g, or 0.6 to 1.3cm 3 / g, or 0.65 to 1.3cm 3 / g, or 0.65 to 1.2cm 3 / g, or 0.7 to 1.2cm 3 / g, or 0.7 to 1.1cm 3 / g, or 0.7 to 1cm 3 / g, or 0.75 to 0.95cm 3 Within the range of / g.

[0042] The total volume of micropores and mesopores in porous particles can also range from 0.4 to 0.75 cm³. 3 / g, or 0.4 to 0.7cm 3 / g, or 0.4 to 0.65cm 3 / g, 0.45 to 0.75cm 3 / g, or 0.45 to 0.7cm 3 / g, or 0.45 to 0.65cm 3 / g, or 0.45 to 0.6cm 3 Within the range of / g.

[0043] The total volume of micropores and mesopores in porous particles can also range from 0.6 to 2 cm³. 3 / g, or 0.6 to 1.8cm 3 / g, or 0.7 to 1.8cm 3 / g, or 0.7 to 1.6cm 3 / g, or 0.8 to 1.6cm 3 / g, or 0.8 to 1.5cm 3 / g, or 0.8 to 1.4cm 3 / g, or 0.9 to 1.5cm 3 / g, or 0.9 to 1.4cm 3 / g, or 1 to 1.4cm 3 Within the range of / g.

[0044] General term "PD" n In this paper, "pore size" refers to the nth percentile pore size based on the total volume of micropores and mesopores. For example, the term "PD" as used herein. 50 "Aperture" refers to the aperture when 50% of the total micropore and mesopore volume is lower than a certain aperture.

[0045] PD of porous particles 50 The pore size is preferably no more than 30 nm, and optionally no more than 25 nm, or no more than 20 nm, or no more than 15 nm, or no more than 12 nm. More preferably, the PD of porous particles... 50 The aperture is no more than 10 nm, or no more than 8 nm, or no more than 6 nm, or no more than 5 nm, or no more than 4 nm, or no more than 3 nm, or no more than 2.5 nm, or no more than 2 nm, or no more than 1.5 nm. As used herein, the term "PD" is used in this document. 50 "Pore diameter" refers to the volumetric median pore diameter based on the total volume of micropores and mesopores. Therefore, according to the present invention, at least 50% of the total volume of micropores and mesopores is preferably in the form of pores with a diameter of less than 30 nm.

[0046] PD of porous particles 30 The aperture may not exceed 25nm, or 20nm, or 15nm, or 12nm, or 10nm, or 8nm, or 6nm, or 5nm, or 4nm, or 3nm, or 2.5nm, or 2nm, or 1nm.

[0047] PD of porous particles 90The pore size can be no more than 35 nm, or no more than 30 nm, or no more than 25 nm, or no more than 20 nm, or no more than 15 nm, or no more than 12 nm, or no more than 10 nm, or no more than 8 nm, or no more than 6 nm, or no more than 5 nm, or no more than 4 nm, or no more than 3 nm, or no more than 2.5 nm, or no more than 2 nm. Preferably, the PD of porous particles... 90 The pore size is at least 2.5 nm, or at least 3 nm, or at least 3.5 nm, or at least 4 nm. For example, the PD of porous particles. 90 The aperture is preferably in the range of 2.5 to 20 nm, or 3 to 15 nm, or 3.5 to 10 nm, or 4 to 8 nm.

[0048] PD of porous particles 10 The pore size can be no more than 10 nm, or no more than 9 nm, or no more than 8 nm, or no more than 7 nm, or no more than 6 nm, or no more than 5 nm, or no more than 4 nm, or no more than 3 nm, or no more than 2.5 nm, or no more than 2 nm, or no more than 1.5 nm, or no more than 1 nm. Preferably, the PD of porous particles... 10 The pore size is at least 0.3 nm, or at least 0.4 nm, or at least 0.5 nm. For example, the PD of porous particles. 10 The aperture is preferably in the range of 0.3 to 10 nm, or 0.3 to 5 nm, or 0.3 to 1 nm, or 0.4 to 1 nm, or 0.5 to 1 nm.

[0049] To avoid ambiguity, and to determine PD n Values, without considering any large pore volume (pore diameter greater than 50nm).

[0050] The volume ratio of micropores to mesopores in porous particles can generally be in the range of 100:0 to 0:100. Preferably, the volume ratio of micropores to mesopores is 90:10 to 55:45, or 90:10 to 60:40, or 85:15 to 65:35.

[0051] The pore size distribution of porous particles can be unimodal, bimodal, or multimodal. As used herein, the term "pore size distribution" refers to the distribution of the pore size of porous particles relative to the cumulative total internal pore volume. Bimodal or multimodal pore size distributions may be preferred because the close proximity between micropores and pores with larger diameters provides the advantage of efficient ion transport from porous networks to electroactive materials.

[0052] Following the standard methods described in ISO 15901-2 and ISO 15901-3, using quenched solid density functional theory (QSDFT), nitrogen adsorption was applied at 77 K to reduce the density to 10. -6The relative pressure p / p0 is used to determine the total volume of micropores and mesopores, as well as the pore size distribution of micropores and mesopores. Nitrogen adsorption is a technique that characterizes the porosity and pore size distribution of a material by condensing a gas within the pores of a solid. As the pressure increases, the gas first condenses in the pores with the smallest diameter, and the pressure increases until a saturation point is reached, at which point all pores are filled with liquid. The nitrogen pressure is then gradually decreased 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. Suitable instruments for measuring pore volume and pore size distribution by nitrogen adsorption include the TriStar II and TriStar IIPlus porosity analyzers (available from Micromeritics Instrument Corporation, USA), and the Autosorb IQ porosity analyzer (available from Quantachrome Instruments).

[0053] Nitrogen adsorption is effective for measuring pore volume and pore size distribution of pores with a maximum diameter of 50 nm, but it is less reliable for pores with much larger diameters. For the purposes of this invention, nitrogen adsorption is therefore used only for pores with a maximum diameter of 50 nm (including 50 nm) (i.e., only for micropores and mesopores) to determine pore volume and pore size distribution. PD 50 The value is also determined only relative to the total volume of micropores and mesopores.

[0054] Due to limitations in available analytical techniques, it is impossible to measure pore volume and pore size distribution across the entire range of micropores, mesopores, and macropores using a single technique. In the case of porous particles including macropores, the volume of pores with diameters in the range of 50 nm to 100 nm can be measured by mercury porosimetry, preferably not exceeding 0.3 cm³. 3 / g, or not exceeding 0.2cm 3 / g, or not exceeding 0.1cm 3 / g, or not exceeding 0.05cm 3 / g. Although a small number of macropores can be useful in facilitating the entry of electrolytes into the porous network, the advantages of the present invention are primarily achieved by accommodating electroactive materials in micropores and smaller mesopores.

[0055] Any pore volume below 50 nm measured by mercury porosimetry is not considered (as mentioned 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 not considered.

[0056] Mercury intrusion porosimetry (MIP) is a technique for characterizing the porosity and pore size distribution of a material sample by applying different levels of pressure to the sample immersed in mercury. The pressure required to allow mercury to penetrate the pores of the sample is inversely proportional to the pore size. The values ​​obtained by MIP reported in this paper are based on ASTM UOP578-11, where the surface tension γ is 480 mN / m for mercury at room temperature, and the contact angle is... The temperature is 140°C. The density of mercury at room temperature is 13.5462 g / cm³. 3 A variety of high-precision mercury porosimetry instruments are commercially available, such as the AutoPore IV series automated mercury porosimeter, which is available from Micromeritics Instrument Corporation in the United States. 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.

[0057] It should be understood that intrusion techniques such as gas adsorption and mercury porosimetry are only effective for determining the pore volume of pores accessible to nitrogen or mercury from the outside of porous particles. Porosity values ​​indicated herein should be understood as referring to the volume of open pores (i.e., pores accessible to fluid from the outside of porous particles). In determining porosity values ​​herein, completely encapsulated pores that cannot be identified by nitrogen adsorption or mercury porosimetry should not be considered. Similarly, any pore volume located in pores as small as or below the detection limit of nitrogen adsorption should not be considered.

[0058] As used herein, the term "particle size" refers to the equivalent sphere diameter (esd), which is the diameter of a sphere with 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"... 50 "and "D 50 "Particle size" refers to the volume median particle size, that is, the diameter at which 50% of the volume of the particle population is measured to be smaller than a certain diameter. As used in this paper, the term "D" is similar. 10 "and "D 10 "Particle size" refers to the 10th percentile volume median particle size, that is, the diameter at which 10% of the volume of the particle population is measured to be smaller than a certain diameter. As used in this paper, the term "D" is similar. 90 "and "D 90 "Particle size" refers to the 90th percentile volume median particle size, that is, the diameter at which 90% of the volume of the particle population is measured to be below a certain diameter.

[0059] Particle size and particle size distribution can be determined using standard laser diffraction techniques according to ISO 13320:2009. Laser diffraction relies on the principle that particles scatter light at an angle that varies with particle size, and that an aggregate of multiple particles will produce a scattered light pattern defined by intensity and angle that can be correlated with particle size distribution. A variety of commercially available laser diffraction instruments are available for rapid and reliable determination of particle size distribution. Unless otherwise stated, particle size distribution measurements specified or reported herein are performed using instruments from Malvern Instruments. TM The standard Malvern Mastersizer TM Measured using a 3000 particle size analyzer. Malvern Mastersizer TM The 3000 particle size analyzer operates by projecting a helium-neon gas laser beam through a transparent cell containing particles of interest suspended in an aqueous solution. The light striking the particles is scattered at an angle inversely proportional to the particle size, and a photodetector array measures the intensity of the light at multiple predetermined angles. The particle size distribution is determined by computer processing of the intensities measured at different angles using standard theoretical principles. The laser diffraction values ​​reported in this paper were obtained using a solution containing 5 vol% surfactant SPAN. TM -40 (sorbitan monopalmitate) particles were obtained in a wet dispersion in 2-propanol. The refractive index of the porous particles was considered to be 2.68, the refractive index of the composite particles was considered to be 3.50, and the refractive index of the dispersant was considered to be 1.378. The particle size distribution was calculated using the Mie scattering model.

[0060] Typically, the D of porous particles 50 The particle size ranges from 0.5 to 200 μm. Optionally, the D of the porous particles... 50 The particle size can be at least 1 μm, or at least 1.5 μm, or at least 2 μm, or at least 2.5 μm, or at least 3 μm, or at least 4 μm, or at least 5 μm. Optionally, the D of the porous particles... 50 The particle size may not exceed 150 μm, or not exceed 100 μm, or not exceed 70 μm, or not exceed 50 μm, or not exceed 40 μm, or not exceed 30 μm, or not exceed 25 μm, or not exceed 20 μm, or not exceed 18 μm, or not exceed 15 μm, or not exceed 12 μm, or not exceed 10 μm, or not exceed 8 μm.

[0061] For example, the D of porous particles 50The particle size can be in the range of 0.5 to 150 μm, or 0.5 to 100 μm, or 0.5 to 50 μm, or 0.5 to 30 μm, or 1 to 25 μm, or 1 to 20 μm, or 2 to 25 μm, or 2 to 20 μm, or 2 to 18 μm, or 2 to 15 μm, or 2 to 12 μm, or 2.5 to 15 μm, or 2.5 to 12 μm, or 2 to 10 μm, or 3 to 20 μm, or 3 to 18 μm, or 3 to 15 μm, or 4 to 18 μm, or 4 to 15 μm, or 4 to 12 μm, or 5 to 15 μm, or 5 to 12 μm, or 5 to 10 μm, or 5 to 8 μm. Particles within these size ranges and having the porosity and pore size distribution described herein are ideally suited for use as composite particles in the anode of metal-ion batteries, prepared via the CVI process.

[0062] D of porous particles 10 The particle size is preferably at least 0.2 μm, or at least 0.5 μm, or at least 0.8 μm, or at least 1 μm, or at least 1.5 μm, or at least 2 μm. This is achieved by using D... 10 Maintaining a particle size above 0.2 μm reduces the likelihood of agglomeration of undesirable submicron-sized particles and improves the dispersibility of the resulting composite particles.

[0063] D of porous particles 90 The preferred size is no more than 300 μm, or no more than 250 μm, or no more than 200 μm, or no more than 150 μm, or no more than 100 μm, or no more than 80 μm, or no more than 60 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.

[0064] Porous particles preferably have a narrow size distribution span. For example, the particle size distribution span (defined as (D...) 90 -D 10 ) / D 50 The particle size distribution is preferably 5 or less, more preferably 4 or less, more preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. By maintaining a narrow size distribution span, it is easier to achieve efficient particle filling into a dense powder bed.

[0065] The average sphericity (as defined herein) of the porous particles can exceed 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 porous 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 also to a denser packing in the final product, both in batch pressure reactors and when incorporated into electrodes.

[0066] Highly accurate two-dimensional projections of micrometer-scale particles can be obtained using scanning electron microscopy (SEM) or dynamic image analysis, where a digital camera is used to record the shadow of the particle projection. As used herein, the term "sphericity" should be understood as the ratio of the area of ​​the particle projection (obtained by such procedural techniques) to the area of ​​a circle, wherein the particle projection and the circle have the same circumference. Therefore, for an individual particle, the sphericity S can be defined as:

[0067]

[0068] Where A m It is the measured area of ​​the particle projection, and C m This is the measured perimeter of the particle's projection. For example, the average sphericity S of multiple particles used in this paper... av Defined as:

[0069]

[0070] Where n represents the number of particles in the swarm. The average sphericity of the multiple particles is preferably calculated by two-dimensional projections of at least 50 particles.

[0071] The BET surface area of ​​porous particles is preferably at least 100 m². 2 / g, or at least 500m 2 / g, or at least 750m 2 / g, or at least 1,000m 2 / g, or at least 1,250m 2 / g, or at least 1,500m 2 / g. As used herein, the term "BET surface area" should be understood to refer to the surface area per unit mass calculated from the measurement of the physical adsorption of gas molecules on a solid surface according to ISO 9277 using the Brunauer–Emmett–Teller principle. Preferably, the BET surface area of ​​the porous particles does not exceed 4,000 m². 2 / g, or not exceeding 3,500m 2 / g, or not exceeding 3,250m 2 / g, or not exceeding 3,000m 2 / g, or not exceeding 2,500m 2 / g, or not exceeding 2,000m 2 / g. For example, the BET surface area of ​​porous particles can be 100m². 2 / g to 4,000m 2 / g, or 500m 2 / g to 4,000m 2 / g, or 750m 2 / g to 3,500m 2 / g, or 1,000m 2 / g to 3,250m 2 / g, or 1,000m 2 / g to 3,000m 2 / g, or 1,000m 2 / g to 2,500m 2 / g, or 1,000m 2 / g to 2,000m 2 Within the range of / g.

[0072] The particle density of the porous particles is preferably at least 0.35 and more preferably less than 3 g / cm³. 3 More preferably less than 2g / cm 3 More preferably less than 1.5 g / cm³ 3 The optimal value is 0.35 to 1.2 g / cm³. 3 As used herein, the term "particle density" refers to the "apparent particle density" measured by mercury porosimetry (i.e., the mass of a particle divided by its volume, where the particle volume is considered as the sum of the volumes of the solid material and any closed or blind pores ("blind pores" are pores too small to be measured by mercury porosimetry). Preferably, the particle density of porous particles is at least 0.4 g / cm³. 3 or at least 0.45 g / cm³ 3 or at least 0.5 g / cm 3 or at least 0.55 g / cm 3 or at least 0.6 g / cm³ 3 or at least 0.65 g / cm³ 3 or at least 0.7 g / cm 3 Preferably, the particle density of the porous particles does not exceed 1.15 g / cm³. 3 or not exceeding 1.1 g / cm³ 3 or not exceeding 1.05 g / cm³ 3 or not exceeding 1g / cm 3 or not exceeding 0.95 g / cm³3 or not exceeding 0.9 g / cm³ 3 .

[0073] Preferably, the porous particles have:

[0074] (i) Between 0.4 and 2.2 cm 3 Total pore volume of micropores and mesopores within the range of / g, measured by nitrogen adsorption;

[0075] (ii) PDs not exceeding 20nm 50 PD aperture, preferably not exceeding 30 nm 90 PD aperture, preferably not exceeding 15 nm 30 Aperture; and

[0076] (iii) D in the range of 0.5 to 30 μm 50 Particle size.

[0077] More preferably, porous particles have:

[0078] (i) Between 0.6 and 1.8 cm 3 Total pore volume of micropores and mesopores within the range of / g, measured by nitrogen adsorption;

[0079] (ii) PDs not exceeding 10nm 50 PD aperture, preferably not exceeding 20 nm 90 PD aperture, preferably not exceeding 8 nm 30 Aperture; and

[0080] (iii) D in the range of 1 to 25 μm 50 Particle size.

[0081] More preferably, porous particles have:

[0082] (i) Between 0.7 and 1.6 cm 3 Total pore volume of micropores and mesopores within the range of / g, measured by nitrogen adsorption;

[0083] (ii) PDs not exceeding 10nm 50 PD aperture, preferably not exceeding 20 nm 90 PD aperture, preferably not exceeding 8 nm 30 Aperture; and

[0084] (iii) D in the range of 1 to 20 μm 50 Particle size.

[0085] More preferably, porous particles have:

[0086] (i) Between 0.7 and 1.5 cm 3Total pore volume of micropores and mesopores within the range of / g, measured by nitrogen adsorption;

[0087] (ii) PDs not exceeding 5nm 50 PD aperture, preferably not exceeding 10 nm 90 PD aperture, preferably not exceeding 3 nm 30 Aperture; and

[0088] (iii) D in the range of 2 to 20 μm 50 Particle size.

[0089] More preferably, porous particles have:

[0090] (i) Between 0.7 and 1.4 cm 3 Total pore volume of micropores and mesopores within the range of / g, measured by nitrogen adsorption;

[0091] (ii) PDs not exceeding 5nm 50 PD aperture, preferably not exceeding 10 nm 90 PD aperture, preferably not exceeding 3 nm 30 Aperture; and

[0092] (iii) D in the range of 2 to 20 μm 50 Particle size.

[0093] More preferably, porous particles have:

[0094] (i) Between 0.7 and 1.4 cm 3 Total pore volume of micropores and mesopores within the range of / g, measured by nitrogen adsorption;

[0095] (ii) PDs not exceeding 5nm 50 PD aperture, preferably not exceeding 10 nm 90 PD aperture, preferably not exceeding 3 nm 30 Aperture; and

[0096] (iii) D in the range of 2 to 18 μm 50 Particle size.

[0097] More preferably, porous particles have:

[0098] (i) Between 0.7 and 1.4 cm 3 Total pore volume of micropores and mesopores within the range of / g, measured by nitrogen adsorption;

[0099] (ii) PDs not exceeding 2nm 50 PD aperture, preferably not exceeding 5 nm 90 PD aperture, preferably not exceeding 1 nm 30Aperture; and

[0100] (iii) D in the range of 2 to 15 μm 50 Particle size.

[0101] The electroactive materials deposited in steps (b) and (d) may be the same or different, and may optionally be independently selected from silicon, tin, germanium, aluminum, and mixtures and alloys thereof. Silicon is a preferred electroactive material. Preferably, the electroactive material deposited in at least one of steps (b) and (d) is silicon. More preferably, the electroactive material deposited in each of steps (b) and (d) is silicon.

[0102] Suitable silicon precursors include: silane (SiH4), silane (Si2H6), propane (Si3H8), and butane (Si4H). 10 ), methylsilane (CH3SiH3), dimethylsilane ((CH3)2SiH2) or chlorosilane such as trichlorosilane (HSiCl3) or methylchlorosilane such as methyltrichlorosilane (CH3SiCl3) or dimethyldichlorosilane ((CH3)2SiCl2). A preferred silicon precursor is silane.

[0103] Suitable tin precursors include: bis[bis(trimethylsilyl)amino]tin(II) ([[(CH3)3Si]2N]2Sn), tetraallyltin ((H2C=CHCH2)4Sn), tetra(diethylamino)tin(IV) ([(C2H5)2N]4Sn), tetra(dimethylamino)tin(IV) ([(CH3)2N]4Sn), tetramethyltin (Sn(CH3)4), tetravinyltin (Sn(CH=CH2)4), tin(II) acetylacetonate (C 10 H 14 O4Sn), trimethyl(phenylethynyl)tin (C6H5C≡CSn(CH3)3) and trimethyl(phenyl)tin (C6H5Sn(CH3)3). A preferred tin precursor is tetramethyltin.

[0104] Suitable aluminum precursors include tris(2,2,6,6-tetramethyl-3,5-heptanedione)aluminum (Al(OCC(CH3)3CHCOC(CH3)3)3), trimethylaluminum ((CH3)3Al), and tris(dimethylamino)aluminum(III) (Al(N(CH3)2)3). A preferred aluminum precursor is trimethylaluminum.

[0105] Suitable germanium precursors include: germanane (GeH4), hexamethyldigermanium ((CH3)3GeGe(CH3)3), tetramethylgermanium ((CH3)4Ge), tributylgermanium hydride ([CH3(CH2)3]3GeH), triethylgermanium hydride ((C2H5)3GeH), and triphenylgermanium hydride ((C6H5)3GeH). A preferred germanium precursor is germanane.

[0106] When the precursor is a chlorinated compound such as a chlorosilane, the precursor is used in combination with hydrogen, preferably in an atomic ratio of at least 1:1 between hydrogen and chlorine.

[0107] Optionally, the precursor is chlorine-free. Chlorine-free means that the precursor contains less than 1% by weight, preferably less than 0.1% by weight, and more preferably less than 0.01% by weight of a chlorine-containing compound.

[0108] The precursors in steps (b) and (d) may be used in pure (or substantially pure) form, or as a mixture diluted with an inert carrier gas such as nitrogen or argon. In the case of a mixture diluted with an inert carrier gas, the precursor is preferably used in an amount ranging from 1 vol% to 95 vol%, or 1 vol% to 85 vol%, or 1 vol% to 70 vol%, or 1 vol% to 50 vol%, or 2 vol% to 40 vol%, or 5 vol% to 30 vol%, or 5 vol% to 25 vol%, based on the total gas volume of the precursor and the inert carrier gas. Following standard procedures for working in an inert atmosphere, the presence of oxygen should be minimized to prevent unsuitable oxidation of the deposited electroactive material. Preferably, the oxygen content is less than 0.01 vol%, more preferably less than 0.001 vol%, based on the total gas volume used in steps (b) and (d).

[0109] The temperatures in steps (b) and (d) are any temperatures at which the precursors are effectively decomposed to form the electroactive material. Preferably, the temperatures in steps (b) and (d) are independently within the ranges of 300 to 800°C, or 350 to 800°C, or 380 to 700°C, or 380 to 650°C, or 380 to 600°C, or 380 to 550°C, or 380 to 500°C, or 400 to 450°C, or 450 to 500°C, or 350 to 500°C, or 350 to 450°C, or 380 to 450°C. More preferably, the temperatures in each of steps (b) and (d) are independently within the range of 380-500°C, preferably 380-450°C.

[0110] The pressure in at least one of steps (b) and (d) is maintained below 200 kPa. Preferably, the pressure in at least one of steps (b) and (d) is maintained at or below 150 kPa, or at or below 120 kPa, or at or below 110 kPa, or at or below 100 kPa, or at or below 90 kPa, or at or below 80 kPa, or at or below 70 kPa, or at or below 60 kPa, or at or below 50 kPa.

[0111] Preferably, the pressure in at least step (b) is maintained below 200 kPa. Preferably, the pressure in at least step (b) is maintained at or below 150 kPa, or at or below 120 kPa, or at or below 110 kPa, or at or below 100 kPa, or at or below 90 kPa, or at or below 80 kPa, or at or below 70 kPa, or at or below 60 kPa, or at or below 50 kPa.

[0112] Optionally, the pressure in both steps (b) and (d) can be kept below 200 kPa. Optionally, the pressure in both steps (b) and (d) can be kept equal to or less than 150 kPa, or equal to or less than 120 kPa, or equal to or less than 110 kPa, or equal to or less than 100 kPa, or equal to or less than 90 kPa, or equal to or less than 80 kPa, or equal to or less than 70 kPa, or equal to or less than 60 kPa, or equal to or less than 50 kPa.

[0113] The pressure in step (b) can be lower than the pressure in step (d). For example, the pressure in step (b) can be kept below 200 kPa while the pressure in step (d) is above 200 kPa, or the pressure in step (b) can be kept below 150 kPa while the pressure in step (d) is above 150 kPa, or the pressure in step (b) can be kept below 120 kPa while the pressure in step (d) is above 120 kPa, or the pressure in step (b) can be kept below 110 kPa while the pressure in step (d) is above 110 kPa, or the pressure in step (b) can be kept below 100 kPa while the pressure in step (d) is above 100 kPa.

[0114] The reduced pressure in step (b) compared to step (d) can be advantageous in situations where additional control over the deposition is required in the early stages of deposition, particularly when penetrating highly microporous particles. As mentioned above, performing step (b) at low pressure results in increased diffusivity of the precursor of the electroactive material, enabling it to enter micropores and / or minimal mesopores prior to thermal decomposition.

[0115] Alternatively, the pressure in step (d) may be lower than the pressure in step (b). For example, the pressure in step (b) may be higher than 200 kPa, while the pressure in step (d) remains lower than 200 kPa; or the pressure in step (b) may be higher than 150 kPa, while the pressure in step (d) remains lower than 150 kPa; or the pressure in step (b) may be higher than 120 kPa, while the pressure in step (d) remains lower than 120 kPa; or the pressure in step (b) may be higher than 110 kPa, while the pressure in step (d) remains lower than 110 kPa; or the pressure in step (b) may be higher than 100 kPa, while the pressure in step (d) remains lower than 100 kPa.

[0116] The reduced pressure in step (d) compared to step (b) can be advantageous in situations where additional control over the deposition is required in the later stages of deposition. For example, in cases where the electroactive material occupies a high proportion of the pore volume of the porous particles, additional control may be needed in the later stages to ensure that the precursor gas permeates the remaining pore volume, thereby ensuring that the electroactive material is preferably deposited within the internal pore volume and not deposited on the outer surface of the porous particles.

[0117] The pressure mentioned in any step of the claimed method refers to the absolute pressure in the reaction zone, which may include any suitable form of reaction vessel.

[0118] The deposition of electroactive materials via CVI results in the elimination of byproducts, particularly byproduct gases such as hydrogen. Step (c) preferably includes at least the separation of byproducts from the intermediate particles formed in step (b). This separation can be achieved by flushing the reactor with an inert gas and / or by venting the reactor at reduced pressure. For example, the separation can be achieved by venting the reactor to pressures below 100 kPa, or below 80 kPa, or below 60 kPa, or below 40 kPa, or below 20 kPa, or below 10 kPa, or below 5 kPa, or below 2 kPa, or below 1 kPa. Venting the reactor to low pressure not only effectively removes byproducts from the gas phase but also effectively desorbs any byproducts that may have adsorbed onto the surface of the deposited electroactive material.

[0119] As discussed above, step (c) may optionally include the step of forming a modified material on the surface of the electroactive material deposited in step (b).

[0120] The modified material formed in step (c) can optionally be a passivation layer formed on the surface of the electroactive material deposited in step (b). Thus, step (c) can also include contacting the intermediate particles from step (b) with a passivating agent. As defined herein, a passivating agent is a compound or mixture of compounds capable of reacting with the surface of the electroactive material deposited in step (b) to form a modified surface.

[0121] The passivation layer can be a native oxide layer. The native oxide layer can be formed, for example, by exposing the surface of the electroactive material to a passivating agent selected from air or other oxygen-containing gases. In the case where the first electroactive material is silicon, the passivation layer can comprise a silicon oxide of the formula SiO x where 0 < x ≤ 2. The silicon oxide is preferably amorphous silicon oxide. The formation of the native oxide layer is exothermic, so careful process control is required to prevent overheating or even combustion of the particulate material. In the case where the modified material formed in step (c) is a native oxide layer, step (c) can include: cooling the material formed in step (b) to a temperature below 300 °C, preferably below 200 °C, optionally below 100 °C, before contacting the surface of the electroactive material domain with an oxygen-containing gas.

[0122] The passivation layer can be a nitride layer formed, for example, by exposing the surface of the electroactive material to a passivating agent selected from ammonia or other nitrogen-containing molecules before depositing a second electroactive material layer. In the case where the first electroactive material is silicon, the passivation layer can comprise a silicon nitride of the formula SiN x where 0 < x ≤ 4 / 3. The silicon nitride is preferably amorphous silicon nitride. The nitride layer can be formed by contacting the surface of the electroactive material domain with ammonia at a temperature in the range of 200 - 700 °C, preferably 400 - 700 °C, more preferably 400 - 600 °C. Then, the temperature can be raised to the range of 500 to 1,000 °C if necessary to form a nitride surface (e.g., a silicon nitride surface of the formula SiNx where x ≤ 4 / 3). For example, in the case of using ammonia, step (c) can be carried out at a temperature the same as or similar to the temperature used in step (b) for depositing the electroactive material domain. Nitride passivation can be superior to oxide passivation. Since sub-stoichiometric nitrides (such as SiN x where 0 < x ≤ 4 / 3) are conductive, the nitride interlayer serves as a conductive network that allows for faster charging and discharging of the electroactive material. The nitride-modified material domain is also thought to improve the capacity retention rate. As a phosphorus analogue of ammonia, phosphine can also be used as a passivating agent.

[0123] The passivation layer can be, for example, an oxynitride layer formed by exposing the surface of the first electroactive material layer to a passivating agent containing ammonia (or other nitrogen-containing molecules) and oxygen before depositing the second electroactive material layer. In the case where the first electroactive material layer is silicon, the first interlayer material can comprise silicon oxynitride of the formula SiO x N y where 0 < x < 2, 0 < y < 4 / 3, and 0 < (2x + 3y) ≤ 4). The silicon nitride is preferably amorphous silicon oxynitride.

[0124] The passivation layer can be a carbide layer. In the case where the first electroactive material layer is silicon, the first interlayer can comprise silicon carbide of the formula SiC x where 0 < x ≤ 1. The silicon carbide is preferably amorphous silicon carbide. The carbide layer can be formed by contacting the surface of the first electroactive material with a passivating agent selected from carbon-containing precursors (such as methane or ethylene) at a high temperature in the range of 250 to 700 °C. At lower temperatures, covalent bonds are formed between the surface of the electroactive material and the carbon-containing precursor, which transforms into a crystalline silicon carbide monolayer as the temperature increases. In the case where the electroactive material domain contains silicon, the modified material domain can comprise silicon carbide of the formula SiCx, where 0 < x ≤ 1.

[0125] The passivation layer can comprise an organic moiety covalently bonded to at least a portion of the surface of the electroactive material. For example, the modified material domain can comprise a carbon-containing organic moiety covalently bonded to at least a portion of the surface of the electroactive material domain. For example, the modified material domain can comprise a hydrocarbon group covalently bonded to the surface of the electroactive material domain.

[0126] Passivating agents suitable for forming a passivation layer comprising an organic moiety covalently bonded to at least a portion of the surface of the electroactive material include: compounds containing an olefin, alkyne or carbonyl functional group, more preferably compounds containing a terminal olefin, terminal alkyne or aldehyde or ketone group.

[0127] Preferred passivating agents include one or more compounds having the following formula:

[0128] (i) R 1 -CH=CH-R 1 ;

[0129] (ii) R 1 -C≡C-R 1 ; and

[0130] (iii) O=CR 1 R 1 ;

[0131] where each R 1Independently 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 group forms an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms.

[0132] Particularly preferred passivating agents include one or more compounds having the following formula:

[0133] (i)CH2=CH-R 1 ;and

[0134] (ii)HC≡CR 1 ;

[0135] Where R 1 As defined above. Preferably, R 1 It is not replaced.

[0136] 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.

[0137] It is believed that passivating agents containing olefin, alkyne, or carbonyl groups undergo an insertion reaction with MH groups (where M represents atoms of the electroactive material) on the surface of the electroactive material to form a covalently passivated surface resistant to air oxidation. When silicon is the electroactive material, the passivation reaction between the silicon surface and the passivating agent can be understood as a form of hydrosilylation, as illustrated below.

[0138]

[0139] Replacing the hydride ends at the surface of the electroactive material domains with covalently bonded organic modified material domains (such as carbon-containing organic parts) is advantageous because hydride ends may decompose to produce hydrogen gas, which could be detrimental to the electrode morphology. Additionally, Si-C bonding is considered to improve conductivity.

[0140] 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. The reaction of the group –XH with the hydride group on the surface of the electroactive material is understood to result in the elimination of H2 and the formation of a direct bond between X and the surface of the electroactive material.

[0141] Suitable passivating agents of this class include compounds having the following formula:

[0142] (iv)HX-R 2 ,and

[0143] (v)HX-C(O)-R 1 ,

[0144] Where X represents O, S, NR 1 or PR 1 ; Each R 1 Independently as defined above; and R 2 It 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 a substituted or substituted ring structure that does not contain 3 to 8 carbon atoms in the ring.

[0145] Preferably, X represents O or NH.

[0146] Preferably, R 2 This indicates an optionally substituted aliphatic or aromatic group having 2 to 10 carbon atoms. An amino group may also be incorporated into a 4-10 member aliphatic or aromatic ring structure, as in pyrrolidine, pyrrole, imidazole, piperazine, indole, or purine.

[0147] The contact between the electroactive material and the passivating agent in step (c) can be carried out at a temperature in the range of 25 to 700°C, preferably in the range of 50 to 500°C, and more preferably in the range of 100 to 300°C.

[0148] The modified material formed in step (c) may optionally comprise pyrolytic carbon material deposited onto the surface of the electroactive material via the thermal decomposition of a carbon-containing precursor, i.e., by chemical vapor infiltration (CVI). The deposition of the pyrolytic carbon material in step (c) can be advantageous because it forms a conductive network between the structural domains of the electroactive material, which can facilitate electron transport within the composite particles. Therefore, step (c) may include contacting the intermediate particles from step (b) with the carbon-containing precursor (preferably a hydrocarbon) at a temperature that effectively induces the deposition of the pyrolytic carbon material in the pores of the intermediate particles.

[0149] Suitable hydrocarbons include polycyclic hydrocarbons containing 10 to 25 carbon atoms and optionally 1 to 3 heteroatoms, wherein the polycyclic hydrocarbon is optionally selected from naphthalene, substituted naphthalene (e.g., dihydroxynaphthalene), anthracene, tetraphenylene, pentaphenylene, fluorene, dihydroacenaphthene, phenanthrene, fluoranthene, pyrene, etc. Perylene, quinone, fluorenone, anthraquinone, anthrone, and their alkyl-substituted derivatives. Suitable pyrolytic carbon precursors also include dicyclic monoterpenes, optionally selected from camphor, borneol, eucalyptol, camphene, careen, juniperene, limonene, and pinene. Other suitable pyrolytic carbon precursors include C2-C. 10Hydrocarbons, optionally selected from alkanes, alkenes, alkynes, cycloalkanes, cycloolefins, and aromatic hydrocarbons, such as methane, ethylene, propylene, limonene, styrene, cyclohexane, cyclohexene, α-terpinene, and acetylene. Other suitable pyrolytic carbon precursors include phthalocyanines, sucrose, starch, graphene oxide, reduced graphene oxide, pyrene, perhydropyrene, 9,10-benzophenanthrene, tetraphenylene, benzo[a]pyrene, perylene, benzo[a]pyrene, and... The preferred carbon precursor is acetylene.

[0150] The suitable temperature for depositing the pyrolytic carbon material in step (c) is in the range of 300 to 800°C, or 400 to 700°C. For example, the temperature may not exceed 680°C, or 660°C, or 640°C, or 620°C, or 600°C, or 580°C, or 560°C, or 540°C, or 520°C, or 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.

[0151] The carbon-containing precursor used in step (c) can be used in pure form or as a mixture diluted 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 vol% to 100 vol%, or 0.5 vol% to 20 vol%, or 1 vol% to 10 vol%, or 1 vol% to 5 vol% based on the total volume of the precursor and the inert carrier gas. The presence of oxygen should be minimized to prevent undesirable oxidation of the deposited electroactive material. Preferably, the oxygen content is less than 0.01 vol% based on the total volume of the gas, more preferably less than 0.001 vol%.

[0152] In step (c), when depositing pyrolytic carbon material, the same compound can act as both a passivating agent and a pyrolytic carbon precursor. For example, if styrene is chosen as the pyrolytic carbon precursor, styrene will also act as a passivating agent if the intermediate particles from step (b) are not exposed to oxygen before contacting the styrene. In this case, passivation and deposition of conductive carbon material can be performed simultaneously, for example, at temperatures in the range of 300-700°C. Alternatively, passivation and deposition of conductive carbon material can be performed sequentially, using the same material as both the passivating agent and the pyrolytic carbon precursor, but with the deposition of the pyrolytic carbon precursor at a higher temperature than passivation. For example, passivation can be performed at temperatures in the range of 25°C to below 300°C, and the deposition of pyrolytic carbon can be performed at temperatures in the range of 300-700°C. These two steps can be performed sequentially by increasing the temperature while maintaining contact with the compound that simultaneously acts as 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 dominant process. As the temperature rises (for example, to 300-700°C), pyrolytic carbon deposition will then occur.

[0153] Depending on the amount of electroactive material deposited in each step, the method of the present invention can be operated as a multi-pass process, wherein steps (c) and (d) are repeated multiple times as needed to deposit a target amount of electroactive material. For example, steps (c) and (d) can be performed 2 to 15 times, resulting in a total of 3 to 16 electroactive material deposition steps including step (b) and repeated step (d).

[0154] When repeating steps (c) and (d), the requirement that the pressure in at least one of steps (b) and (d) be kept below 200 kPa should be interpreted as referring to step (b) or either step (d). Preferably, the pressure in at least step (b) is kept below 200 kPa.

[0155] Optionally, the pressure in more than one of step (b) and repeated step (d) can be kept below 200 kPa. For example, the pressure in at least step (b) and at least one step (d) can be kept below 200 kPa. Optionally, the pressure in all steps (b) and repeated step (d) can be kept below 200 kPa.

[0156] When steps (c) and (d) are repeated, each instance of steps (c) and (d) is performed independently as described above. For example, each repetition of step (c) may include forming the same or different modified material, or optionally, no modified material may be formed in one or more steps. Similarly, the electroactive material deposited in each repetition of step (d) may be the same or different, and may again be the same or different from the electroactive material deposited in step (b). Preferably, the electroactive material deposited in at least one of step (b) and the repeated step (d) is silicon. More preferably, the electroactive material deposited in each of step (b) and the repeated step (d) is silicon.

[0157] When steps (c) and (d) are repeated, the particles used in the repetition of step (c) are intermediate particles obtained from the previous step (d). Therefore, any reference to "particles from step (b)" in the description of step (c) herein should be interpreted as "particles from the previous step (d)" in the case of any repetition of step (c).

[0158] The method of the present invention can be used to obtain a range of electroactive material loadings in different composite particles. For example, based on the total mass of the composite particles, the amount of electroactive material (e.g., silicon) in the composite particles can range from 5 wt% to 85 wt%. Preferably, based on the total mass of the composite particles, the amount of electroactive material in the composite particles is 10 wt% to 85 wt%, or 15 wt% to 85 wt%, or 20 wt% to 80 wt%, or 25 wt% to 80 wt%, or 30 wt% to 75 wt%, or 35 wt% to 75 wt%, or 40 wt% to 70 wt%, or 45 wt% to 65 wt%. The total electroactive material loading in the composite particles is the sum of the electroactive materials deposited in steps (b) and (d) (including repetitions of step (d)).

[0159] The amount of electroactive material (e.g., silicon) in the composite particles is preferably selected such that at least 20% to 90% of the internal pore volume of the porous particles is occupied by the electroactive material after step (c). 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 porous particles. Within these preferred ranges, the remaining pore volume of the porous particles effectively accommodates the expansion of the electroactive material during charging and discharging without a large excess pore volume, which would be detrimental to the volumetric capacity of the particles. However, the amount of electroactive material is not high enough to hinder effective lithiation due to insufficient metal ion diffusion rate or insufficient expansion volume leading to mechanical resistance to lithiation.

[0160] When the electroactive material is silicon, the mass ratio of silicon to porous particles is required to be within [0.5×P]. 1 Up to 1.9×P 1 Within the range of 1, the amount of silicon in the composite particles can be correlated with the available pore volume in the porous particles, where P 1 It is the total pore volume (in cm³) of micropores and mesopores in porous particles. 3 / g represents a dimensionless quantity of size (e.g., if the total volume of micropores and mesopores of a porous particle is 1.2 cm³). 3 / g, then P 1 =1.2). This relationship takes into account the density of silicon and the pore volume of porous particles to define the weight ratio of silicon, at which the occupied pore volume is approximately 20% to 82%.

[0161] The amount of electroactive material in the composite particles can be determined by elemental analysis. Preferably, elemental analysis is used to determine the elemental composition of the individual porous particles and the composition of the composite particles.

[0162] Silicon content is preferably determined by ICP-OES (inductively coupled plasma-optical emission spectrometry). Various commercially available ICP-OES instruments are available, such as... The 7000 series ICP-OES analyzer (available from Thermo Fisher Scientific). Carbon content (and, if necessary, hydrogen, nitrogen, and oxygen content) of composite particles and individual porous carbon particles is preferably determined by IR absorption. Suitable instruments for determining carbon, hydrogen, nitrogen, and oxygen content are... Micro elemental analyzer (available from Leco Corporation).

[0163] Preferably, at least 90% by weight, more preferably at least 95% by weight, and even more preferably at least 98% by weight of the electroactive material in the composite particles are located within the internal pore volume of the porous particles, such that little or no electroactive material is located on the outer surface of the composite particles. As discussed above, the deposition of the electroactive material during the CVI process occurs on the surface of the porous particles. Given the very high internal surface area of ​​the porous particles, the reaction kinetics of the CVI process ensure that the deposition of the electroactive material occurs almost entirely within the pores of the porous particles. The internal deposition of the electroactive material is further improved by requiring that the pressure in at least one of steps (b) and (d) be kept below 200 kPa or within the preferred pressure range discussed above.

[0164] The method of the present invention may optionally further include the following steps:

[0165] (e) A plurality of modified material structural domains are formed in the pores and / or on the outer surface of the composite particles from step (d).

[0166] Step (e) is performed immediately after the final electroactive material deposition step (i.e., step (d), or, in the case of repeating steps (c) and (d), the final repetition of step (d)). The formation of the modified material domains in step (e) is similar to that in step (c) as described above, except that step (e) is performed after the final electroactive material deposition step (the final step (d)), while step (c) is performed between successive electroactive material deposition steps. Any of the modified materials and deposition conditions disclosed herein with respect to step (c) also apply to step (e).

[0167] The modified material domain formed in step (e) may contain the same or different modified materials as the modified material domain formed in step (c).

[0168] Optionally, step (e) includes contacting the composite particles from step (d) with a passivating agent. The preferred passivating agents and passivation conditions described above with respect to step (c) also apply to the passivation in step (e).

[0169] Optionally, step (e) includes depositing a lithium-ion permeable material into the pores and / or outer surface of the composite particles from step (d). This provides further improvement in the performance of the composite particles as electroactive materials in lithium-ion batteries by reducing the surface area of ​​the composite particles and by sealing the electroactive material structural domains away from the electrolyte.

[0170] The lithium-ion permeable material can be deposited immediately after the final electroactive material deposition step (i.e., step (d), or, if steps (c) and (d) are repeated more than once, the final step (d)). Alternatively, the lithium-ion permeable material can be deposited after the first passivation step as discussed above in step (e).

[0171] A suitable lithium-ion permeable material is pyrolytic carbon material. Pyrolytic carbon material can be obtained by chemical vapor infiltration (CVI), which involves thermally decomposing volatile carbon-containing gases (such as ethylene) onto the surface of composite particles.

[0172] A suitable process for depositing pyrolytic carbon materials includes: combining composite particles from step (d) with a pyrolytic carbon precursor; and heating the pyrolytic carbon precursor to a temperature that effectively induces the deposition of pyrolytic conductive carbon material into the pores and / or outer surface of the composite particles.

[0173] The preferred pyrolytic carbon precursor and pyrolysis conditions described above for step (c) also apply to the formation of the pyrolytic carbon material in step (e).

[0174] When the lithium-ion permeable material is a pyrolytic carbon material, in step (e), the same compound can simultaneously act as a passivating agent and a pyrolytic carbon precursor. The conditions suitable for using the same compound as both a passivating agent and a pyrolytic carbon precursor in step (e) for passivation and the formation of the pyrolytic carbon material are the same as those described above regarding step (c).

[0175] Alternatively, different compounds can be used as passivating agents and pyrolytic carbon precursors in step (e). For example, the passivating agent can be styrene, and the pyrolytic carbon precursor can be a compound such as cyclohexane, which can form pyrolytic carbon materials but cannot passivate the surface of the electroactive material.

[0176] The composite particles obtained by the method of this invention can be characterized by their performance under thermogravimetric analysis (TGA) in air. This analytical method relies on the principle that an increase in weight is observed when an electroactive material is oxidized in air at elevated temperatures.

[0177] As defined herein, “surface silicon” is the initial mass increase measured along a TGA trace from a minimum of 150°C to 500°C to a maximum of 550°C to 650°C, where the TGA is performed in air at a heating rate of 10°C / min. This mass increase is considered to be due to oxidation of the surface silicon, thus allowing the percentage of surface silicon as a proportion of the total silicon to be determined according to the following formula:

[0178] Y = 1.875 × [(M max –M min ) / M f ]×100%

[0179] Where Y is the percentage of surface silicon (the proportion of total silicon in the sample), M max M is the maximum mass of the sample measured within the temperature range of 550℃ to 650℃. min It is the minimum mass of the sample at temperatures above 150°C and below 500°C, and M f This refers to the mass of the sample after oxidation at 1400℃. For completeness, 1.875 should be understood as the molar mass ratio of SiO2 to O2 (i.e., the mass ratio of the SiO2 formed to the mass increase due to the addition of oxygen). Typically, TGA analysis uses a sample amount of 10 mg ± 2 mg.

[0180] One advantage of the method of the present invention is that the low-voltage CVI step results in composite particles with a high content as determined by the TGA method described above. As a result, the reversible capacity retention over multiple charge / discharge cycles is significantly improved. In the composite particles prepared according to the method of the present invention, the surface silicon content is generally at least 20% by weight of the total silicon in the composite particles, and may be at least 22% by weight, or at least 25% by weight, at least 30% by weight, or at least 35% by weight, or at least 40% by weight, or at least 45% by weight.

[0181] In addition to the surface silicon content, the silicon-containing composite particles obtained by the method of this invention have a low coarse-phase silicon content, as determined by TGA. Coarse-phase silicon is defined herein as silicon oxidized at temperatures 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-phase silicon content is determined according to the following formula:

[0182] Z = 1.875 × [(M f -M 800 ) / M f ]×100%

[0183] Where Z is the percentage of silicon that was not oxidized at 800℃, and M... 800 The mass of the sample at 800℃, and M f This refers to the mass of ash when oxidation is complete at 1400℃. For the purposes of this analysis, it is assumed that any mass increase above 800℃ corresponds to silicon oxidation to SiO2, and that the total mass at the completion of oxidation is SiO2.

[0184] Silicon oxidized at temperatures above 800°C is less desirable. In the composite particles prepared according to the method of the present invention, the content of coarse phase silicon generally does not exceed 10% by weight of the total amount of silicon in the composite particles, and may not exceed 8% by weight, or 6% by weight, or 5% by weight, or 4% by weight, or 3% by weight, or 2% by weight, or 1.5% by weight.

[0185] Preferably, at least 30% by weight of silicon is surface silicon, and no more than 10% by weight of silicon is bulk silicon, both determined by TGA. More preferably, at least 35% by weight of silicon is surface silicon, and no more than 8% by weight of silicon is bulk silicon, both determined by TGA. More preferably, at least 40% by weight of silicon is surface silicon, and no more than 5% by weight of silicon is bulk silicon, both determined by TGA. More preferably, at least 45% by weight of silicon is surface silicon, and no more than 2% by weight of silicon is bulk silicon, both determined by TGA.

[0186] The BET surface area of ​​the composite particles obtained by the method according to the present invention is preferably no more than 300 m². 2 / g, or not exceeding 250m 2 / g, or not exceeding 200mg 2 / g, or not exceeding 150m 2 / g. More preferably, not exceeding 100m 2 / g, or not exceeding 80m 2 / g, or not exceeding 60m 2 / g, or not exceeding 40m 2 / g, or not exceeding 30m 2 / g, or not exceeding 25m 2 / g, or not exceeding 20m 2 / g, or not exceeding 15m 2 / g, or not exceeding 10m 2 / g, or not exceeding 5m 2 / g. Generally, a low BET surface area is preferred to minimize the formation of a solid electrolyte interface (SEI) layer at the surface of the composite particles during the first charge-discharge cycle of the anode. However, an excessively low BET surface area results in unacceptably low charge rates and capacities due to the inaccessibility of the electroactive material bulk to metal ions in the surrounding electrolyte. The BET surface area is preferably at least 0.1 m². 2 / g, or at least 1m 2 / g, or at least 2m 2 / g, or at least 5m 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 80m 2 / g, or 0.5 to 60m 2 / g, or 0.5 to 40m 2 / g, or 1 to 30m 2 / g, or 1 to 25m 2 / g, or 2 to 20m 2 Within the range of / g.

[0187] The reaction can be carried out using any reactor capable of bringing solids and gases into contact at high temperatures. Porous particles and the resulting composite particles can exist in the reactor as a fixed bed of particles or as a moving or stirred bed of particles.

[0188] In a second aspect, the present invention provides a composite particle that can be obtained by the method of the first aspect of the present invention.

[0189] In a third aspect of the invention, a composition is provided comprising composite particles according to a second aspect of the invention and at least one other component. Specifically, a composition is provided comprising composite particles according to a second aspect of the invention and at least one other component selected from: (i) a binder; (ii) a conductive additive; and (iii) additional particulate electroactive materials. The composition according to the third aspect of the invention can be used as an electrode composition and therefore can be used to form the active layer of an electrode.

[0190] The composition can be a hybrid electrode composition comprising the composite particles and at least one additional particulate electroactive material. Examples of additional particulate electroactive materials include graphite, hard carbon, silicon, tin, germanium, aluminum, and lead. The at least one additional particulate electroactive material is preferably selected from graphite and hard carbon, and most preferably, the at least one additional particulate electroactive material is graphite.

[0191] In the case of a hybrid electrode composition, the composition preferably comprises 3% to 60% by weight, or 3% to 50% by weight, or 5% to 50% by weight, or 10% to 50% by weight, or 15% to 50% by weight of the total dry weight of the composition, based on the composite particles according to the second aspect of the invention.

[0192] At least one additional particulate electroactive material is suitably present in an amount of 20% to 95% by weight, or 25% to 90% by weight, or 30% to 750% by weight.

[0193] At least one other particulate electroactive material D 50 The particle size is preferably in the range of 10 to 50 μm, more preferably in the range of 10 to 40 μm, more preferably in the range of 10 to 30 μm, and most preferably in the range of 10 to 25 μm, for example in the range of 15 to 25 μm.

[0194] At least one other particulate electroactive material D 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 still more preferably at least 10 μm.

[0195] At least one other particulate electroactive material D 90 The particle size is preferably up to 100 μm, more preferably up to 80 μm, more preferably up to 60 μm, more preferably up to 50 μm, and most preferably up to 40 μm.

[0196] At least one additional particulate electroactive material is preferably selected from carbon particles, graphite particles, and / or hard carbon particles, wherein the D of the graphite particles and hard carbon particles is...50 The particle size is in the range of 10 to 50 μm. More preferably, the at least one additional particulate electroactive material is selected from graphite particles, wherein the graphite particles have a D... 50 The particle size is in the range of 10 to 50 μm.

[0197] The composition may also be an unmixed (or “high-loading”) electrode composition that is substantially free of additional particulate electroactive material. In this case, the term “substantially free of additional particulate electroactive material” should be interpreted as meaning that, based on the total dry weight of the composition, the composition contains less than 15% by weight, preferably less than 10% by weight, preferably less than 5% by weight, preferably less than 2% by weight, more preferably less than 1% by weight, and more preferably less than 0.5% by weight of any additional electroactive material (i.e., additional material capable of intercalating and releasing metal ions during battery charging and discharging).

[0198] Based on the total dry weight of the composition, this type of "high loading" 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 according to the second aspect of the invention.

[0199] 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 that can be used according to the invention 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 a mixture of various adhesives. Preferably, the adhesive comprises polymers selected from: polyacrylic acid (PAA) and its alkali metal salts, and modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0200] The adhesive may suitably be present in an amount of 0.5% to 20% by weight, preferably 1% to 15% by weight, preferably 2% to 10% by weight, and most preferably 5% to 10% by weight, based on the total dry weight of the composition.

[0201] The adhesive may optionally be present in combination with one or more additives that alter the properties of the adhesive, such as crosslinking accelerators, coupling agents, and / or adhesion promoters.

[0202] The composition may optionally include one or more conductive additives. Preferred conductive additives are non-electroactive materials included to improve the conductivity between the electroactive components of the composition and the conductivity between the electroactive components 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.

[0203] One or more conductive additives may suitably be present in a total amount of 0.5% to 20% by weight, preferably 1% to 15% by weight, preferably 2% to 10% by weight, and most preferably 5% to 10% by weight, based on the total dry weight of the composition.

[0204] In a fourth aspect, the present invention provides an electrode comprising composite particles according to a second aspect of the invention in electrical contact with a current collector. The particulate material used to prepare the electrode according to the fourth aspect of the invention may be in the form of a composition according to a third aspect of the invention.

[0205] As used herein, the term current collector refers to any conductive substrate capable of carrying current to and from the electroactive particles in the composition. Examples of materials that can be used as current collectors include copper, aluminum, stainless steel, nickel, titanium, and sintered carbon. Copper is a preferred material. Current collectors are typically in the form of foils or meshes with a thickness of 3 to 500 μm. The particulate material of the present invention can be applied to one or both surfaces of the current collector to achieve a thickness preferably in the range of 10 μm to 1 mm, for example, 20 to 500 μm, or 50 to 200 μm.

[0206] The electrode of the fourth aspect of the present invention can be prepared by combining the particulate material of the present invention with a solvent and optionally one or more viscosity-modifying additives to form a slurry. The slurry is then cast onto the surface of a current collector, and the solvent is removed, thereby forming an electrode layer on the surface of the current collector. Additional steps may be performed as appropriate, such as heat treatment for curing any binder and / or calendering of the electrode layer. 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.

[0207] Alternatively, the slurry can be formed into a self-standing film or pad containing the particulate material of the present invention, for example, by casting the slurry onto a suitable casting stencil, removing the solvent, and then removing the casting stencil. The resulting film or pad is in the form of a viscous, self-standing object, which can then be bonded to a current collector by known methods.

[0208] The electrode of the fourth aspect of the present invention can be used as the anode of a metal-ion battery. Therefore, in a fifth aspect, the present invention provides a rechargeable metal-ion battery comprising: an anode including the electrode as described above; a cathode comprising a cathode active material capable of releasing and reabsorbing metal ions; and an electrolyte between the anode and the cathode.

[0209] The metal ions are preferably lithium ions. More preferably, the rechargeable metal ion battery of the present invention is a lithium ion battery, and the cathode active material is capable of releasing and accepting lithium ions.

[0210] The cathode active material is preferably a composite material based on metal oxides. Examples of suitable cathode active materials include LiCoO2 and LiCo. 0.99 Al 0.01 O2, LiNiO2, LiMnO2, LiCo 0.5 Ni 0.5 O2, LiCo 0.7 Ni 0.3 O2, LiCo 0.8 Ni 0.2 O2, LiCo 0.82 Ni 0.18 O2, LiCo 0.8 Ni 0.15 Al 0.05 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2 and LiNi 0.33 Co 0.33 Mn 0.34 O2. Cathode current collectors typically have a thickness of 3 to 500 μm. Examples of materials that can be used as cathode current collectors include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0211] Electrolytes are suitably non-aqueous electrolytes containing metal salts (e.g., lithium salts), and may include, but are not limited to, non-aqueous electrolytes, solid electrolytes, and inorganic solid electrolytes. Examples of non-aqueous electrolyte solutions that can be used include aprotic organic solvents such as propylene carbonate, ethylene carbonate, butyl 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.

[0212] 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 ion-dissociating groups.

[0213] Examples of inorganic solid electrolytes include lithium salt nitrides, halides, and sulfides (such as Li5NI2, Li3N, LiI, LiSiO4, Li2SiS3, Li4SiO4, LiOH, and Li3PO4).

[0214] Lithium salts are suitably soluble in a solvent or mixture of solvents of choice. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO4, LiBF4, LiBC4O8, LiPF6, LiCF3SO3, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, and CF3SO3Li.

[0215] When the electrolyte is a non-aqueous organic solution, the metal-ion battery preferably has a separator between the anode and cathode. The separator is typically formed of an insulating material with high ion permeability and high mechanical strength. The separator typically has a pore size of 0.01 to 100 μm and a thickness of 5 to 300 μm. Examples of suitable electrode separators include microporous polyethylene membranes.

[0216] A polymer electrolyte material can be used instead of the diaphragm, and in this case, the polymer electrolyte material exists within 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.

Claims

1. A method for preparing composite particles, the method comprising the following steps: (a) Provides multiple porous particles comprising micropores and / or mesopores, wherein the total pore volume of micropores and mesopores, as measured by nitrogen adsorption, is between 0.4 and 2.2 cm³. 3 Within the range of / g; (b) The porous particles are brought into contact with the precursor of the electroactive material at a temperature that effectively causes the electroactive material to deposit in the pores of the porous particles to form intermediate particles; (c) Interrupt the deposition of the electroactive material and separate the byproducts from the intermediate particles; (d) The intermediate particles from step (c) are brought into contact with the precursor of the electroactive material at a temperature that effectively induces further deposition of the electroactive material in the pores of the intermediate particles. In at least one of steps (b) and (d), the pressure is kept below 200 kPa.

2. The method according to claim 1, wherein the porous particles comprise a conductive material.

3. The method according to claim 1, wherein the porous particles comprise a conductive carbon material.

4. The method according to claim 1, wherein the total volume of the micropores and mesopores of the porous particles is between 0.45 and 2.2 cm³. 3 / g, or 0.5 to 2 cm 3 / g, or 0.55 to 2 cm 3 / g, or 0.6 to 1.8 cm 3 / g, or 0.65 to 1.8 cm 3 / g, or 0.7 to 1.6 cm 3 / g, or 0.7 to 1.5 cm 3 / g, or 0.7 to 1.4 cm 3 Within the range of / g.

5. The method according to claim 1, wherein the porous particles have PD 50 The aperture is not more than 30 nm, or not more than 25 nm, or not more than 20 nm, or not more than 15 nm, or not more than 12 nm, or not more than 10 nm, or not more than 8 nm, or not more than 6 nm, or not more than 5 nm, or not more than 4 nm, or not more than 3 nm, or not more than 2.5 nm, or not more than 2 nm, or not more than 1.5 nm.

6. The method according to claim 1, wherein the porous particle framework PD 30 The aperture is no more than 25 nm, or no more than 20 nm, or no more than 15 nm, or no more than 12 nm, or no more than 10 nm, or no more than 8 nm, or no more than 6 nm, or no more than 5 nm, or no more than 4 nm, or no more than 3 nm, or no more than 2.5 nm, or no more than 2 nm, or no more than 1 nm.

7. The method according to claim 1, wherein the D of the porous particles 50 The particle size is in the range of 0.5 to 30 µm, or 1 to 25 µm, or 1 to 20 µm, or 2 to 25 µm, or 2 to 20 µm, or 2 to 18 µm, or 2 to 15 µm, or 2 to 12 µm, or 2.5 to 15 µm, or 2.5 to 12 µm, or 2 to 10 µm.

8. The method according to claim 1, wherein the volume ratio of micropores to mesopores in the porous particles is 90:10 to 55:45, or 90:10 to 60:40, or 85:15 to 65:

35.

9. The method according to claim 1, wherein the BET surface area of ​​the porous particles is 100 m². 2 / g 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 1,000 m 2 / g to 2,000 m 2 Within the range of / g.

10. The method of claim 1, wherein the electroactive material deposited in steps (b) and (d) is independently selected from silicon, tin, germanium, aluminum, and mixtures and alloys thereof.

11. The method of claim 10, wherein the electroactive material deposited in at least one of steps (b) and (d) is silicon.

12. The method of claim 1, wherein the electroactive material deposited in each of steps (b) and (d) is the same electroactive material.

13. The method of claim 12, wherein the electroactive material deposited in each of steps (b) and (d) is silicon.

14. The method according to claim 11 or claim 13, wherein the silicon-containing precursor is selected from silane (SiH4), silane (Si2H6), propane (Si3H8), and butane (Si4H). 10 ), methylsilane, dimethylsilane and chlorosilane.

15. The method of claim 1, wherein the temperature in steps (b) and (d) is independently within the range of 300 to 800 ºC, or 350 to 800 ºC, or 400 to 700 ºC, or 400 to 650 ºC, or 400 to 600 ºC, or 400 to 550 ºC, or 400 to 500 ºC, or 400 to 450 ºC, or 450 to 500 ºC, or 350 to 500 ºC, or 350 to 450 ºC, or 380 to 450 ºC.

16. The method of claim 1, wherein the pressure in at least one of steps (b) and (d) is maintained at or below 150 kPa, or at or below 120 kPa, or at or below 110 kPa, or at or below 100 kPa, or at or below 90 kPa, or at or below 80 kPa, or at or below 70 kPa, or at or below 60 kPa, or at or below 50 kPa.

17. The method of claim 16, wherein at least the pressure in step (b) is maintained at or below 150 kPa, or at or below 120 kPa, or at or below 110 kPa, or at or below 100 kPa, or at or below 90 kPa, or at or below 80 kPa, or at or below 70 kPa, or at or below 60 kPa, or at or below 50 kPa.

18. The method of claim 1, wherein step (c) comprises separating the byproduct from the intermediate particle.

19. The method of claim 1, wherein step (c) further comprises forming a modified material on the surface of the electroactive material deposited in step (b).

20. The method of claim 19, wherein step (c) comprises contacting the intermediate particles from step (b) with a passivating agent.

21. The method of claim 20, wherein the passivating agent is selected from: (i) an oxygen-containing gas; (ii) ammonia; (iii) a gas containing ammonia and oxygen; and (iv) phosphine.

22. The method of claim 20, wherein the passivating agent is selected from: (i)R 1 -CH=CH-R 1 ; (ii) R 1 -C≡CR 1 4 (iii)O=CR 1 R 1 ; (iv)HX-R 2 ,and (v)HX-C(O)-R 1 , Where X represents O, S, NR 1 or PR 1 ;and 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 group forms an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms; Where R 2 It represents an unsubstituted or substituted aliphatic or aromatic hydrocarbon group having 1 to 20 carbon atoms, or wherein R 1 and R 2 Together they form an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms.

23. The method according to any one of claims 19 to 22, wherein step (c) comprises contacting the intermediate particles from step (b) with the carbon-containing precursor at a temperature that effectively induces the deposition of pyrolytic carbon material in the pores of the intermediate particles.

24. The method of claim 1, wherein steps (c) and (d) are repeated more than once.

25. The method according to claim 1, further comprising the following steps: (e) A plurality of modified material structural domains are formed in the pores and / or on the outer surface of the composite particles from step (d).

26. The method of claim 25, wherein step (e) comprises contacting the surface of the composite particles from the final step (d) with a passivating agent, optionally wherein the passivating agent is defined as in claim 21 or claim 22.

27. The method of claim 25 or claim 26, wherein step (e) comprises: The composite particles from step (d) are combined with the pyrolytic carbon precursor; And heating the pyrolytic carbon precursor to a temperature that effectively induces the deposition of pyrolytic conductive carbon material into the pores and / or outer surface of the composite particles.

28. A composite particle that can be obtained by any one of claims 1 to 27.

29. A composition comprising the composite particles of claim 28 and at least one other component.

30. An electrode comprising the composite particles of claim 28 or the composition of claim 29.

31. A rechargeable metal-ion battery, the rechargeable metal-ion battery comprising the electrode of claim 30.

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