Method for preparing electroactive materials for metal ion batteries - Patents.com

Abstract

The present invention relates to a method for preparing composite particles, the method comprising the steps of: 3 / g~2.2cm 3 The method includes a first step of providing a plurality of porous particles comprising micropores and / or mesopores, the micropores and / or mesopores being in the range of 0.1 μm / g. The porous particles are contacted with a precursor of an electroactive material at a temperature effective to cause deposition of an electroactive material in the pores of the porous particles to form intermediate particles. The deposition of the electroactive material is interrupted and, optionally, by-products are separated from the intermediate particles. The intermediate particles are then contacted with a precursor of an electroactive material at a temperature effective to cause further deposition of an electroactive material in the pores of the intermediate particles to form composite particles. During at least one of the deposition steps, the reactor pressure is maintained below 200 kPa.

Description

[Technical field]

[0001] The present invention relates generally to methods for preparing electroactive materials suitable for use in electrodes for rechargeable metal-ion batteries, and more particularly to particulate materials having high electrochemical capacity suitable for use as anode active materials in rechargeable metal-ion batteries. [Background technology]

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

[0003] There is interest in improving the gravimetric and / or volumetric capacity of rechargeable metal-ion batteries. To date, commercially available lithium-ion batteries have been primarily limited to the use of graphite as the anode active material. Upon charging a graphite anode, lithium is inserted between the graphite layers, with the empirical formula Li x C 6where x is greater than 0 and less than or equal to 1. As a result, graphite has a maximum theoretical capacity of 372 mAh / g in lithium-ion batteries, with practical capacities somewhat lower (approximately 340 mAh / g to 360 mAh / g). Other materials, such as silicon, tin, and germanium, can intercalate lithium at significantly higher capacities than graphite, but are not yet in widespread commercial use due to the difficulty of maintaining sufficient capacity over many charge-discharge cycles.

[0004] In particular, silicon has been recognized as a promising alternative to graphite in the manufacture of rechargeable metal-ion batteries with high gravimetric and volumetric capacities due to its extremely high capacity relative to lithium (see, for example, Non-Patent Document 1). Silicon has a theoretical maximum specific capacity of about 3600 mAh / g (Li ion battery) at room temperature. 15 S 4 (based on the theory of lithium intercalation in silicon). However, when lithium is intercalated into bulk silicon, the volume of the silicon material increases significantly, up to 400% of its original volume when silicon is lithiated to its maximum capacity. Repeated charge-discharge cycles induce significant mechanical stresses in the silicon material, leading to fracture and delamination of the silicon anode material. The volumetric shrinkage of silicon particles upon delithiation can result in loss of electrical contact between the anode material and the current collector. To make matters even more difficult, the solid electrolyte interface (SEI) layer that forms on the silicon surface is not mechanically durable enough to accommodate the expansion and contraction of silicon. As a result, the newly exposed silicon surface leads to further decomposition of the electrolyte, an increase in the thickness of the SEI layer, and irreversible consumption of lithium. Collectively, these failure mechanisms result in unacceptable electrochemical capacity loss over successive charge-discharge cycles.

[0005] Numerous approaches have been proposed to overcome the problems associated with the volume changes observed during charging of silicon-containing anodes. Fine silicon structures with cross sections less than about 150 nm, such as silicon films and silicon nanoparticles, have been reported to be more resistant to volume changes during charging and discharging compared to silicon particles in the micron size range. However, none of these are suitable for commercial-scale application without morphology modification. Nanoscale particles are difficult to manufacture and handle, and silicon films do not provide sufficient bulk capacitance.

[0006] US Patent Publication 2007 / 0133963 discloses that capacity retention can be improved by using silicon particles with a high aspect ratio, i.e., the ratio of the maximum dimension to the minimum dimension of the particle. The small cross-section of such particles reduces the structural stress on the material due to volume changes during charging and discharging. However, such particles can be difficult and expensive to manufacture, and can be fragile. Also, the large surface area can lead to the formation of excessive SEI, leading to excessive capacity loss during the first charge-discharge cycle.

[0007] It is also commonly known that electroactive materials such as silicon can be deposited within the pores of porous support materials such as activated carbon materials. These composites offer some of the beneficial charge-discharge properties of nanoscale silicon particles while avoiding the difficulties of handling nanoparticles. Guo et al. (Non-Patent Document 2) disclose a silicon-carbon composite in which a porous carbon substrate provides a conductive scaffold with silicon nanoparticles deposited uniformly distributed within the substrate's pore structure. The composite has been shown to improve capacity retention over multiple charging cycles, but the initial capacity of the composite in mAh / g is significantly lower than that for silicon nanoparticles.

[0008] The present inventors have previously reported the development of a class of electroactive materials having a composite structure in which a nanoscale electroactive material, such as silicon, is deposited within the pore network of a highly porous particulate material, such as a porous carbon material.

[0009] For example, US Pat. No. 5,999,333 and US Pat. No. 5,999,366 report that the improved electrochemical performance of these materials can be attributed to the manner in which the electroactive material is located in the porous material in the form of small domains with dimensions on the order of a few nanometers or less. These fine electroactive structures are believed to have lower resistance to elastic deformation and higher fracture resistance than larger electroactive structures, and therefore can be lithiated and delithiated without excessive structural stress. As a result, the electroactive material exhibits excellent reversible capacity retention over multiple charge-discharge cycles. Second, by controlling the loading of silicon in the porous carbon framework such that only a portion of the pore volume is occupied by uncharged silicon, the unoccupied pore volume of the porous carbon framework can accommodate a significant amount of silicon expansion therein. Furthermore, as mentioned above, by locating nanoscale silicon domains in small mesopores and / or micropores, only a small area at the silicon surface is accessible to the electrolyte, thus limiting SEI formation. Further exposure of silicon during subsequent charge-discharge cycles is substantially prevented so that SEI formation does not become a significant failure mechanism leading to capacity loss. This is in stark contrast to the excessive SEI formation that characterizes the materials disclosed by, for example, Guo (see above).

[0010] The materials described in US Pat. No. 5,993,336 and US Pat. No. 5,993,336 have been synthesized by chemical vapor infiltration (CVI) in different reactor systems (static, rotating and FBR). Porous particles are contacted with a stream of silicon-containing precursor (CVI), typically silane gas, at atmospheric pressure and temperatures between 400° C. and 700° C. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2007 / 083155 [Patent Document 2] International Publication No. 2020 / 095067 [Patent Document 3] International Publication No. 2020 / 128495 [Non-patent literature]

[0012] [Non-Patent Document 1] Insertion Electrode Materials for Rechargeable Lithium Batteries, Winter, M. et al. in Adv. Mater. 1998, 10, No. 10 [Non-Patent Document 2] Journal of Materials Chemistry A, 2013, pp. 14075-14079 Summary of the Invention [Problem to be solved by the invention]

[0013] There remains a need in the art for improved methods of making electroactive materials with improved performance. [Means for solving the problem]

[0014] In a first aspect, the present invention provides a method for preparing a composite particle, comprising the steps of: (a) The total pore volume of micropores and mesopores as measured by nitrogen gas adsorption is 0.4 cm 3 / g~2.2cm 3 providing a plurality of porous particles comprising micropores and / or mesopores, the micropores and / or mesopores being in the range of 0.1 μm / g; (b) contacting the porous particles with a precursor of an electroactive material at a temperature effective to cause deposition of an electroactive material in the pores of the porous particles to form intermediate particles; (c) interrupting the deposition of the electroactive material and optionally separating by-products from the intermediate particles; (d) contacting the intermediate particles from step (c) with a precursor of an electroactive material at a temperature effective to cause further deposition of the electroactive material in the pores of the intermediate particles to form composite particles; Including, The reactor pressure of at least one of steps (b) and (d) is maintained below 200 kPa; A method is provided.

[0015] The invention therefore generally relates to a method for preparing a composite particulate material in which an electroactive material is deposited in the pores of a porous particulate material in at least two separate steps. An initial deposition of electroactive material is performed in step (b) and a further deposition of electroactive material is performed in step (d). Optionally, steps (c) and (d) may be repeated multiple times such that the method of the invention comprises depositing electroactive material over three or more steps.

[0016] Steps (b) and (d) deposit the first and second electroactive material layers on the pore surfaces of the porous particles using chemical vapor infiltration (CVI) of precursors of the electroactive materials. Chemical vapor infiltration (CVI) is a process in which a porous material is infiltrated with an additional phase, typically by contacting the porous material with reactive gaseous precursors at elevated temperatures. Decomposition / reaction of the reactive gaseous precursors on the pore surfaces results in the deposition of a solid phase within the pores.

[0017] With multi-step deposition of the electroactive material, the deposition of the electroactive material is interrupted by one or more steps (step (c)) that interrupt the deposition of the electroactive material. Interrupting the electroactive material deposition at an intermediate stage throughout the deposition allows for several improvements when compared to processes that deposit all of the electroactive material in a single step.

[0018] First, depositing the electroactive material in at least two separate steps allows for different deposition conditions to be used in each step, which allows for greater control over the CVI process at different stages of the overall deposition. The deposition of the electroactive material in the CVI process occurs at the porous particle surface. Given that the internal surface area of ​​the porous particles is very high, the reaction kinetics favor the deposition of the electroactive material almost entirely within the pores of the porous particles.

[0019] However, a key factor in controlling the deposition of electroactive material is the mass transport of precursors from the outside of the particle to the site where deposition occurs. If mass transport becomes a limiting factor in the CVI process, the electroactive material may be deposited in larger pores or on the outer surface of the electroactive material. Furthermore, the deposited electroactive material may then block access to the smaller pore spaces where it is desired to deposit the electroactive material. Carrying out at least one of steps (b) and (d) at a pressure of less than 200 kPa results in increased diffusivity of the precursors of the electroactive material, allowing access to the micropores and / or smallest mesopores before pyrolysis. Thus, the control of the pressure of at least one of steps (b) and (d) as shown herein allows for improved control of electroactive material deposition.

[0020] Secondly, interrupting the electroactive material deposition at an intermediate stage allows for further process steps to be performed between the continued deposition of the electroactive material. One suitable process step includes separating the by-products from the intermediate particles formed in step (b). If the deposition of the electroactive material is performed in a single step, the precursors of the electroactive material need to diffuse into the pore volume and at the same time the by-products need to diffuse out of the pore volume of the porous particles. This results in inefficient removal of the by-products, which can become entrapped in the deposited electroactive material and thus impair electrochemical performance. Interrupting the electroactive material deposition provides an opportunity for the by-products to diffuse out of the porous particles and be removed before continuing the deposition. This results in improved quality of the deposited material, which results in improved electrochemical performance when the composite particles are incorporated into an electrode.

[0021] Interrupting the electroactive material deposition at an intermediate stage also allows other materials to form on the surface of the electroactive material deposited in step (b). These materials are generally referred to herein as "modifier materials". Suitable modifier materials may include materials formed by chemical modification of the surface of the electroactive material deposited in step (b). Another suitable modifier material may include another deposition material, where the deposition material is non-electroactive. The modifier material 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 domain of electroactive material can be limited by the intervening domains of the modifier material. Larger electroactive material domains have been found to result in poor electrochemical performance. Thus, using modifier materials to interrupt the electroactive material domains allows the length scale of the individual electroactive material domains to be controlled while still allowing the overall electroactive material in the composite particle to have a high capacity.

[0022] The porous particles function as a skeleton of electroactive material that is typically deposited in the form of a plurality of electroactive material domains. The term "electroactive material domains" refers to bodies of electroactive material, such as elemental silicon, with a maximum dimension determined by the dimensions of the micropores and / or mesopores of the porous particles in which they are located. The electroactive domains can therefore also be described as nanoscale electroactive domains, where the term "nanoscale" is generally understood to refer to dimensions less than 100 nm. However, due to the dimensions of the micropores and mesopores, the electroactive material domains typically have a maximum dimension in any direction that is less than, and usually significantly less than, 50 nm. The domains can take the form of, for example, regular or irregular particles or bounded layers or coated regions.

[0023] The porous particles preferably comprise an electrically conductive material. The use of electrically conductive porous particles is preferred because the porous particles form a conductive framework within the composite particle, which facilitates the flow of electrons between the lithium atoms / ions intercalated within the electroactive material and the current collector.

[0024] A preferred type of conductive porous particle is a particle that includes or consists of a conductive carbon material, referred to herein as a conductive porous carbon particle.

[0025] The conductive porous carbon particles preferably comprise at least 80% by weight carbon, more preferably at least 90% by weight carbon, more preferably at least 95% by weight carbon, optionally at least 98% by weight or at least 99% by weight carbon. The carbon may be crystalline or amorphous carbon, or a mixture of amorphous and crystalline carbon. The porous carbon particles may be either hard or soft carbon particles.

[0026] As used herein, the term "hard carbon" refers to carbon atoms that are primarily distributed in nanoscale polyaromatic domains. 2 It refers to a disordered carbon matrix that adopts a hybridized (three-way bond) state. The polyaromatic domains are cross-linked by chemical bonds, e.g., COC bonds. Because the polyaromatic domains are chemically cross-linked, the hard carbon cannot be converted to graphite at high temperatures. The high G band (approx. 1600 cm) in the Raman spectrum -1 ), hard carbon has graphite-like properties. However, the high D band in the Raman spectrum (approximately 1350 cm -1 ), carbon is not entirely graphite-like.

[0027] The term "soft carbon" as used herein also refers to carbon atoms that are primarily dispersed in polyaromatic domains having dimensions in the range of 5 nm to 200 nm. 2It refers to a disordered carbon matrix that adopts a hybridized (three-way bond) state. In contrast to hard carbon, the polyaromatic domains in soft carbon are not cross-linked by chemical bonds but are held together by intermolecular forces; that is, at high temperatures, soft carbon can be graphitized. The porous carbon particles preferably have at least 50% sp 2 For example, the porous carbon particles preferably contain 50% to 98% sp 2 Hybrid carbon, 55%-95% sp 2 Hybrid carbon, 60%-90% sp 2 Hybrid carbon, or 70% to 85% sp 2 It may contain hybridized carbon.

[0028] A variety of different materials can be used to prepare suitable porous carbon particles through pyrolysis. Examples of organic materials that can be used include plant biomass, including lignocellulosic materials (coconut shells, rice husks, wood, etc.), and fossil carbon sources such as coal. Examples of resins and polymeric materials that form porous carbon particles upon pyrolysis include phenolic resins, novolac resins, pitch, melamine, polyacrylates, polystyrene, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers that contain monomer units of acrylates, styrene, α-olefins, vinylpyrrolidone, and other ethylenically unsaturated monomers. Depending on the starting materials and the conditions of the pyrolysis process, a variety of different carbon materials are available in the art. A variety of different specifications of porous carbon particles are available from suppliers.

[0029] To increase the volume of mesopores and micropores, the porous carbon particles can be subjected to a chemical or gas activation process. A suitable activation process is to oxidize the pyrolyzed carbon with oxygen, steam, CO, CO at temperatures ranging from 600°C to 1000°C. 2 and KOH.

[0030] Mesopores can also be obtained by known templating processes using extractable pore formers such as MgO and other colloidal or polymeric templates, which can be removed by thermal or chemical means after pyrolysis or activation.

[0031] Alternatives to carbon-based conductive particles include titanium nitride (TiN), titanium carbide (TiC), silicon carbide (SiC), and nickel oxide (NiO x ), titanium silicon nitride (TiSiN), nickel nitride (Ni 3 N), molybdenum nitride (MoN), titanium oxynitride (TiO x N 1-x The porous particles include those comprising titanium nitride (TiN), silicon oxycarbide (SiOC), boron nitride (BN), or vanadium nitride (VN). Preferably, the porous particles comprise titanium nitride (TiN), silicon oxycarbide (SiOC), or boron nitride (BN).

[0032] Porous particles contain a three-dimensionally interconnected open pore network that includes micropores and / or mesopores, and optionally a small amount of macropores. In accordance with conventional IUPAC terminology, the term "micropores" is used herein to refer to pores with a diameter of less than 2 nm, the term "mesopores" is used herein to refer to pores with a diameter of 2 nm to 50 nm, and the term "macropores" is used herein to refer to pores with a diameter of more than 50 nm.

[0033] References herein to the volume of micropores, mesopores and macropores in a porous particle, and also to the pore volume distribution within the porous particle, refer to the internal pore volume of the porous particle used as starting material in step (a) of the claimed method, i.e. prior to deposition of the electroactive material within the pore volume in step (b).

[0034] The porous particles are 0.4 cm 3 / g~2.2cm 3 / g range (i.e., total pore volume in the pore size range of 0 nm to 50 nm). Typically, the porous particles contain both micropores and mesopores. However, it is not excluded that porous particles containing micropores and no mesopores, or mesopores and no micropores, can be used.

[0035] More preferably, the total volume of the micropores and mesopores in the porous particles is at least 0.45 cm 3 / g, or at least 0.5 cm 3 / g, at least 0.55 cm 3 / g, or at least 0.6 cm 3 / g, or at least 0.65 cm 3 / g, or at least 0.7 cm 3 / g, or at least 0.75 cm 3 / g, or at least 0.8 cm 3 / g, at least 0.85 cm 3 / g, or at least 0.9 cm 3 / g, or at least 0.95 cm 3 / g, or at least 1 cm 3 / g. The use of high porosity may be advantageous as it allows for a greater amount of electroactive material to be accommodated within the pore volume.

[0036] The internal pore volume of the porous particles is suitably limited such that the increased fragility of the particle structure outweighs the benefit of increased pore volume to accommodate a larger amount of electroactive material. Preferably, the total volume of micropores and mesopores in the porous particles is less than 2 cm 3 / g or less, or 1.8 cm 3 / g or less, or 1.6 cm 3 / g or less, or 1.5cm 3 / g or less, or 1.45 cm 3 / g or less, or 1.4cm 3 / g or less, or 1.35 cm 3 / g or less, or 1.3 cm 3 / g or less, or 1.25 cm 3 / g or less, or 1.2 cm 3 / g or less, or 1.1cm 3 / g or less, or 1cm 3 / g or less, or 0.95 cm 3 / g or less.

[0037] Preferably, the total volume of the micropores and mesopores in the porous particles is less than 0.45 cm 3 / g~2.2cm 3 / g, or 0.5 cm 3 / g~2cm 3 / g, or 0.55 cm 3 / g~2cm 3 / g, or 0.6 cm 3 / g~1.8cm 3 / g, or 0.65 cm 3 / g~1.8cm 3 / g, or 0.7 cm 3 / g~1.6cm 3 / g, or 0.7 cm 3 / g~1.5cm 3 / g, or 0.7 cm 3 / g~1.4cm 3 / g range.

[0038] The total volume of micropores and mesopores in the porous particle is also 0.55 cm 3 / g~1.4cm 3 / g, or 0.6 cm 3 / g~1.4cm 3 / g, or 0.6 cm 3 / g~1.3cm 3 / g, or 0.65 cm 3 / g~1.3cm 3 / g, or 0.65 cm 3 / g~1.2cm 3 / g, or 0.7 cm 3 / g~1.2cm 3 / g, or 0.7 cm 3 / g~1.1cm 3 / g, or 0.7 cm 3 / g~1cm 3 / g, or 0.75 cm 3 / g~0.95cm 3 / g.

[0039] The total volume of micropores and mesopores in the porous particle is also 0.4 cm 3 / g~0.75cm 3 / g, or 0.4 cm 3 / g~0.7cm 3 / g, or 0.4 cm 3 / g~0.65cm 3 / g, or 0.45 cm 3 / g~0.75cm 3 / g, or 0.45 cm 3 / g~0.7cm 3 / g, or 0.45 cm 3 / g~0.65cm 3 / g, or 0.45 cm 3 / g~0.6cm 3 / g.

[0040] The total volume of micropores and mesopores in the porous particle is also 0.6 cm 3 / g~2cm 3 / g, or 0.6 cm 3 / g~1.8cm 3 / g, or 0.7 cm 3 / g~1.8cm 3 / g, or 0.7 cm 3 / g~1.6cm 3 / g, or 0.8 cm 3 / g~1.6cm 3 / g, or 0.8 cm 3 / g~1.5cm 3 / g, or 0.8 cm 3 / g~1.4cm 3 / g, or 0.9 cm 3 / g~1.5cm 3 / g, or 0.9 cm 3 / g~1.4cm 3 / g or 1cm 3 / g~1.4cm 3 / g.

[0041] "P.D. nThe collective term "pore size" as used herein refers to the n-th percentile pore size on a volume basis relative to the total volume of micropores and mesopores. For example, "PD 50 The term "pore size" refers to the pore size below which 50% of the total micropore and mesopore volume is found.

[0042] PD of porous particles 50 The pore size is preferably 30 nm or less, and optionally 25 nm or less, or 20 nm or less, or 15 nm or less, or 12 nm or less. More preferably, the PD of the porous particles is 50 The pore size is 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less, or 1.5 nm or less. 50 The term "pore size" refers to the median pore size on a volume basis relative to the total volume of the micropores and mesopores. Thus, according to the present invention, at least 50% of the total volume of the micropores and mesopores is preferably in the form of pores having a diameter of less than 30 nm.

[0043] PD of porous particles 30 The pore size may be 25 nm or less, or 20 nm or less, or 15 nm or less, or 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less, or 1 nm or less.

[0044] PD of porous particles 90 The pore size may be 35 nm or less, or 30 nm or less, or 25 nm or less, or 20 nm or less, or 15 nm or less, or 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less. 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 the porous particles 90The pore diameter is preferably in the range of 2.5 nm to 20 nm, or 3 nm to 15 nm, or 3.5 nm to 10 nm, or 4 nm to 8 nm.

[0045] PD of porous particles 10 The pore size may be 10 nm or less, or 9 nm or less, or 8 nm or less, or 7 nm or less, or 6 nm or less, or 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less, or 1.5 nm or less, or 1 nm or less. 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 the porous particles 10 The pore diameter is preferably in the range of 0.3 nm to 10 nm, or 0.3 nm to 5 nm, or 0.3 nm to 1 nm, or 0.4 nm to 1 nm, or 0.5 nm to 1 nm.

[0046] To avoid any misunderstanding, P.D. n For purposes of determining the value, any macropore volume (pore diameters greater than 50 nm) is not taken into account.

[0047] The volume ratio of micropores to mesopores in the porous particles can in principle 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.

[0048] The pore size distribution of the porous particles may be unimodal, bimodal or multimodal. The term "pore size distribution" as used herein refers to the pore size distribution relative to the cumulative total internal pore volume of the porous particle. A bimodal or multimodal pore size distribution may be preferred, since the proximity of the micropores and larger diameter pores provides the advantage of efficient transport of ions through the porous network to the electroactive material.

[0049] The total volume of micropores and mesopores, as well as the pore size distribution of micropores and mesopores, were determined using quenched solid-state density functional theory (QSDFT) at 77 K for 10°C according to standard methodologies specified in ISO 15901-2 and ISO 15901-3. -6 Relative pressure p / p 0 The pore volume and pore size distribution are determined using nitrogen gas adsorption up to 1000 MPa. Nitrogen gas adsorption is a technique for characterizing the porosity and pore size distribution of a material by condensing a gas in the pores of a solid. As the pressure is increased, the gas condenses initially in the pores with the smallest diameter, and the pressure is increased until a saturation point is reached where all pores are filled with liquid. The nitrogen gas pressure is then reduced in stages to allow the liquid to evaporate from the system. The pore volume and pore size distribution can be determined by analysis of the adsorption and desorption isotherms and the hysteresis between them. Suitable devices for measuring the pore volume and pore size distribution by nitrogen gas adsorption include the TriStar II and TriStar II Plus porosity analyzers available from Micromeritics Instrument Corporation, USA, and the Autosorb IQ porosity analyzer available from Quantachrome Instruments.

[0050] Nitrogen gas adsorption is effective for measuring the pore volume and pore size distribution of pores with diameters up to 50 nm, but is less reliable for pores with much larger diameters. Therefore, for the purposes of the present invention, nitrogen adsorption is used to determine the pore volume and pore size distribution of only pores with diameters up to 50 nm (i.e., only micropores and mesopores). Similarly, PD 50 The value of is determined for the total volume of micropores and mesopores only.

[0051] Given the limitations of available analytical techniques, it is not possible to measure the pore volume and pore size distribution over the full range of micropores, mesopores, and macropores using a single technique. When the porous particles contain macropores, the volume of pores with diameters greater than 50 nm and ranging up to 100 nm can be measured by mercury intrusion porosimetry, preferably at 0.3 cm.3 / g or less, or 0.2 cm 3 / g or less, or 0.1cm 3 / g or less, or 0.05 cm 3 / g or less. Although a small proportion of macropores can be useful to facilitate electrolyte access into the pore network, the advantages of the present invention are substantially obtained by containing the electroactive material in the micropores and smaller mesopores.

[0052] Any pore volume measured by mercury porosimetry at pore diameters of 50 nm or less is disregarded (as described above, nitrogen adsorption is used to characterize mesopores and micropores). Pore volume measured by mercury porosimetry above 100 nm is assumed to be interparticle porosity for purposes of this invention, and this pore volume is also disregarded.

[0053] Mercury porosimetry is a technique for characterizing the porosity and pore size distribution of a material by applying various levels of pressure to a sample of the material immersed in mercury. The pressure required to force mercury into the pores of the sample is inversely proportional to the pore size. Mercury porosimetry values ​​reported herein were obtained according to ASTM UOP578-11, with a surface tension of mercury at room temperature, γ, of 480 mN / m and a contact angle, φ, of 140°. The density of mercury at room temperature is 13.5462 g / cm 3 There are many high-precision mercury intrusion instruments available commercially, such as the AutoPore IV series of automated mercury intrusion meters available from Micromeritics Instrument Corporation, USA. For a complete review of mercury intrusion methods, refer to "Analytical Methods in Fine Particle Technology, 1997, Micromeritics Instrument Corporation" by PA Webb and C. Orr (ISBN 0-9656783-0).

[0054] It will 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 exterior of the porous particle. The porosity values ​​defined herein should be understood to refer to the open pores, i.e., the volume of pores accessible to fluids from the exterior of the porous particle. Completely enclosed pores that cannot be identified by nitrogen adsorption or mercury porosimetry shall not be considered in determining the porosity values ​​herein. Similarly, any pore volume located within pores that are small enough to be below the detection limit by nitrogen adsorption shall not be considered.

[0055] As used herein, the term "particle size" refers to the equivalent spherical diameter (esd), i.e., the diameter of a sphere having the same volume as a given particle, where the volume of the particle is understood to include the volume of the pores within the particle. 50 " and "D 50 The term "particle size" refers to the median particle size on a volume basis, i.e., the diameter below which 50% by volume of the particle population lies. 10 " and "D 10 The term "particle size" refers to the 10th percentile median particle size on a volume basis, i.e., the diameter below which 10% by volume of the particle population lies. 90 " and "D 90 The term "particle size" refers to the volume-based 90th percentile median particle size, i.e., the diameter below which 90% of the particle population falls, by volume.

[0056] Particle size and size distribution can be determined by standard laser diffraction techniques according to ISO 13320:2009. Laser diffraction is based on the principle that particles scatter light at angles that vary with the size of the particle, and a collection of particles produces a scattered light pattern defined by intensity and angle that can be correlated to particle size distribution. Many laser diffraction instruments are commercially available for quickly and reliably determining particle size distribution. Unless otherwise stated, particle size distribution measurements specified or reported herein are measured by a conventional Malvern Mastersizer™ 3000 particle size analyzer manufactured by Malvern Instruments™. The Malvern Mastersizer™ 3000 particle size analyzer works by projecting a helium neon gas laser beam through a transparent cell containing particles of interest suspended in an aqueous solution. The light that strikes the particles is scattered at angles that are inversely proportional to the particle size, and a photodetector array measures the light intensity at several predetermined angles, and the intensities measured at the various angles are processed by a computer using standard theoretical principles to determine the particle size distribution. Laser diffraction values ​​as reported herein are obtained using a wet dispersion of particles in 2-propanol with the addition of 5% by volume of the surfactant SPAN™-40 (sorbitan monopalmitate). The particle refractive index is taken to be 2.68 for porous particles and 3.50 for composite particles, and the dispersant refractive index is taken to be 1.378. The Mie scattering model is used to calculate the particle size distribution.

[0057] Generally, porous particles have a D in the range of 0.5 μm to 200 μm. 50 Optionally, the porous particles have a D 50 The particle size may be at least 1 μm, or at least 1.5 μm, or at least 2 μm, or at least 2.5 μm, or at least 3 μm, or at least 4 μm, or at least 5 μm. Optionally, the D of the porous particles 50The particle size may be 150 μm or less, or 100 μm or less, or 70 μm or less, or 50 μm or less, or 40 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less, or 18 μm or less, or 15 μm or less, or 12 μm or less, or 10 μm or less, or 8 μm or less.

[0058] For example, the porous particles may have a diameter of 0.5 μm to 150 μm, or 0.5 μm to 100 μm, or 0.5 μm to 50 μm, or 0.5 μm to 30 μm, or 1 μm to 25 μm, or 1 μm to 20 μm, or 2 μm to 25 μm, or 2 μm to 20 μm, or 2 μm to 18 μm, or 2 μm to 15 μm, or 2 μm to 12 μm, or 2.5 D in the range of μm to 15 μm, or 2.5 μm to 12 μm, or 2 μm to 10 μm, or 3 μm to 20 μm, or 3 μm to 18 μm, or 3 μm to 15 μm, or 4 μm to 18 μm, or 4 μm to 15 μm, or 4 μm to 12 μm, or 5 μm to 15 μm, or 5 μm to 12 μm, or 5 μm to 10 μm, or 5 μm to 8 μm 50 Particles within these size ranges and having porosities and pore size distributions as set forth herein are ideally suited for the preparation of composite particles for use in anodes for metal ion batteries by the CVI process.

[0059] 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. 10 Maintaining particle size above 0.2 μm reduces the potential for undesirable agglomeration of submicron sized particles and improves dispersibility of the composite particles.

[0060] D of porous particles 90 The particle size is preferably 300 μm or less, or 250 μm or less, or 200 μm or less, or 150 μm or less, or 100 μm or less, or 80 μm or less, or 60 μm or less, or 40 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less.

[0061] The porous particles preferably have a narrow particle size distribution span. For example, the particle size distribution span (D 90 -D 10 ) / D 50 (defined as) is preferably 5 or less, more preferably 4 or less, more preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. By maintaining a narrow particle size distribution span, efficient packing of particles into a dense powder bed is more easily achievable.

[0062] The porous particles may have an average sphericity (as defined above) of greater than 0.5. Preferably, the porous particles have an average sphericity of at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, or at least 0.8, or at least 0.85. Preferably, the porous particles have an average sphericity of at least 0.90, or at least 0.92, or at least 0.93, or at least 0.94, or at least 0.95. It is believed that spherical particles aid in the uniformity of deposition and promote denser packing of the final product when incorporated into batch pressure reactors and electrodes.

[0063] Highly accurate two-dimensional projections of micron-scale particles can be obtained by scanning electron microscopy (SEM) or dynamic image analysis, where the shadows cast by the particles are recorded using a digital camera. The term "sphericity" as used herein is to be understood as the ratio of the area of ​​the particle projection (obtained from such imaging technique) to the area of ​​a circle, where the particle projection and the circle have the same circumference. Thus, for an individual particle, the sphericity S can be defined as:

number

number

[0064] The porous particles preferably have a diameter of at least 100 mm. 2 / g, or at least 500m 2 / g, or at least 750m 2 / g, or at least 1000m 2 / g, or at least 1250m 2 / g, or at least 1500m 2 The term "BET surface area" as used herein should be taken to refer to the surface area per unit mass calculated from measurements of the physical adsorption of gas molecules on a solid surface using the Brunauer-Emmett-Teller theory and in accordance with ISO 9277. Preferably, the BET surface area of ​​the porous particles is greater than 4000 m 2 / g or less, or 3500m 2 / g or less, or 3250m 2 / g or less, or 3000m 2 / g or less, or 2500m 2 / g or less, or 2000m 2 For example, the porous particles have a particle size of 100 m 2 / g~4000m 2 / g, or 500m 2 / g~4000m 2 / g, or 750m 2 / g~3500m 2 / g, or 1000m 2 / g~3250m 2 / g, or 1000m 2 / g~3000m 2 / g, or 1000m 2 / g~2500m 2 / g, or 1000m 2 / g~2000m 2 / g.

[0065] The porous particles preferably have a density of at least 0.35 g / cm 3 and preferably 3 g / cm 3 less than 2 g / cm 3 less than 1.5 g / cm 3 less than 0.35 g / cm 3 ~1.2g / cm 3 The term "particle density" as used herein refers to the "apparent particle density" as measured by mercury intrusion (i.e., particle mass divided by particle volume, where particle volume is taken to be the sum of the volume of the solid material and any closed or blind pores ("blind pores" are pores that are too small to be measured by mercury intrusion). Preferably, the porous particles have a particle density of at least 0.4 g / cm. 3 , or at least 0.45 g / cm 3 , or at least 0.5 g / cm 3 , or at least 0.55 g / cm 3 , or at least 0.6 g / cm 3 , or at least 0.65 g / cm 3 , or at least 0.7 g / cm 3 Preferably, the porous particles have a particle density of 1.15 g / cm 3 or less than 1.1g / cm 3 or less than 1.05g / cm 3 or less than 1g / cm 3 or less than 0.95g / cm 3 or less than 0.9g / cm 3 It has the following particle density:

[0066] Preferably, the porous particles are (i) 0.4 cm 3 / g~2.2cm 3 the total pore volume of micropores and mesopores as measured by nitrogen gas adsorption in the range of 1 / g; (ii) PD less than 20 nm 50 Pore ​​diameter, preferably PD of 30 nm or less 90Pore ​​size, preferably PD of 15 nm or less 30 Pore ​​size, and (iii) D in the range of 0.5 μm to 30 μm 50 Particle size, has.

[0067] More preferably, the porous particles are (i) 0.6 cm 3 / g~1.8cm 3 the total pore volume of micropores and mesopores as measured by nitrogen gas adsorption in the range of 1 / g; (ii) PD less than 10 nm 50 Pore ​​diameter, preferably PD of 20 nm or less 90 Pore ​​size, preferably 8 nm or less PD 30 Pore ​​size, and (iii) D in the range of 1 μm to 25 μm 50 Particle size, has.

[0068] More preferably, the porous particles are (i) 0.7 cm 3 / g~1.6cm 3 the total pore volume of micropores and mesopores as measured by nitrogen gas adsorption in the range of 1 / g; (ii) PD less than 10 nm 50 Pore ​​diameter, preferably PD of 20 nm or less 90 Pore ​​size, preferably 8 nm or less PD 30 Pore ​​size, and (iii) D in the range of 1 μm to 20 μm 50 Particle size, has.

[0069] More preferably, the porous particles are (i) 0.7 cm 3 / g~1.5cm 3 the total pore volume of micropores and mesopores as measured by nitrogen gas adsorption in the range of 1 / g; (ii) PD less than 5 nm 50 Pore ​​diameter, preferably PD of 10 nm or less 90 Pore ​​size, preferably 3 nm or less PD30 Pore ​​size, and (iii) D in the range of 2 μm to 20 μm 50 Particle size, has.

[0070] More preferably, the porous particles are (i) 0.7 cm 3 / g~1.4cm 3 the total pore volume of micropores and mesopores as measured by nitrogen gas adsorption in the range of 1 / g; (ii) PD less than 5 nm 50 Pore ​​diameter, preferably PD of 10 nm or less 90 Pore ​​size, preferably 3 nm or less PD 30 Pore ​​size, and (iii) D in the range of 2 μm to 20 μm 50 Particle size, has.

[0071] More preferably, the porous particles are (i) 0.7 cm 3 / g~1.4cm 3 the total pore volume of micropores and mesopores as measured by nitrogen gas adsorption in the range of 1 / g; (ii) PD less than 5 nm 50 Pore ​​diameter, preferably PD of 10 nm or less 90 Pore ​​size, preferably 3 nm or less PD 30 Pore ​​size, and (iii) D in the range of 2 μm to 18 μm 50 Particle size, has.

[0072] More preferably, the porous particles are (i) 0.7 cm 3 / g~1.4cm 3 the total pore volume of micropores and mesopores as measured by nitrogen gas adsorption in the range of 1 / g; (ii) PD less than 2 nm 50 Pore ​​size, preferably 5 nm or less PD 90 Pore ​​diameter, preferably PD of 1 nm or less 30 Pore ​​size, and (iii) D in the range of 2 μm to 15 μm 50 Particle size, has.

[0073] 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. A preferred electroactive material is silicon. Preferably, the electroactive material deposited in at least one of steps (b) and (d) is silicon. More preferably, both electroactive materials deposited in each of steps (b) and (d) are silicon.

[0074] Suitable precursors for silicon include silane (SiH 4 ), disilane (Si 2 H 6 ), trisilane (Si 3 H 8 ), tetrasilane (Si 4 H 10 ), methylsilane (CH 3 SiH 3 ), dimethylsilane ((CH 3 ) 2 SiH 2 ), or chlorosilanes, such as trichlorosilane (HSiCl 3 ) or methylchlorosilanes, such as methyltrichlorosilane (CH 3 SiCl 3 ) or dimethyldichlorosilane ((CH 3 ) 2 SiCl 2 The preferred precursors of silicon are silanes.

[0075] Suitable precursors of tin include bis[bis(trimethylsilyl)amino]tin(II) ([[(CH 3 ) 3 Si] 2 N] 2 Sn), tetraallyl tin ((H 2 C=CHCH 2 ) 4Sn), tetrakis(diethylamido)tin(IV) ([(C 2 H 5 ) 2 N] 4 Sn), tetrakis(dimethylamido)tin(IV) ([(CH 3 ) 2 N] 4 Sn, tetramethyltin (Sn(CH 3 ) 4 ), tetravinyltin (Sn(CH=CH 2 ) 4 ), tin(II) acetylacetonate (C 10 H 14 O 4 Sn), trimethyl(phenylethynyl)tin (C 6 H 5 C≡CSn(CH 3 ) 3 ), and trimethyl(phenyl)tin (C 6 H 5 Sn(CH 3 ) 3 The preferred precursor of tin is tetramethyltin.

[0076] Suitable precursors of aluminum include aluminum tris(2,2,6,6-tetramethyl-3,5-heptanedionate) (Al(OCC(CH 3 ) 3 CHCOC(CH 3 ) 3 ) 3 ), trimethylaluminum ((CH 3 ) 3 Al), and tris(dimethylamido)aluminum(III) (Al(N(CH 3 ) 2 ) 3 The preferred precursor of aluminum is trimethylaluminum.

[0077] Suitable precursors of germanium include germane (GeH 4 ), hexamethyldigermanium ((CH 3 ) 3 GeGe(CH 3 ) 3), tetramethylgermanium ((CH 3 ) 4 Ge), tributylgermanium hydride ([CH 3 (CH 2 ) 3 ] 3 GeH), triethylgermanium hydride ((C 2 H 5 ) 3 GeH), and triphenylgermanium hydride ((C 6 H 5 ) 3 The preferred precursor of germanium is germane.

[0078] When the precursor is a chlorinated compound, such as a chlorosilane, the precursor is used in a mixture with hydrogen gas, preferably in at least a 1:1 atomic ratio of hydrogen to chlorine.

[0079] Optionally, the precursor is chlorine-free. By chlorine-free, it is meant that the precursor contains less than 1% by weight, preferably less than 0.1% by weight, preferably less than 0.01% by weight of chlorine-containing compounds.

[0080] In steps (b) and (d), the precursors may be used either in pure form (or substantially pure form) or as a dilute mixture with an inert carrier gas, such as nitrogen or argon. When in a dilute mixture with an inert carrier gas, the precursors are preferably used in an amount ranging from 1% to 95% by volume, or from 1% to 85% by volume, or from 1% to 70% by volume, or from 1% to 50% by volume, or from 2% to 40% by volume, or from 5% to 30% by volume, or from 5% to 25% by volume, based on the total gas volume of the precursors and the inert carrier gas. In accordance with conventional practice for working in an inert atmosphere, the presence of oxygen should be minimal to prevent undesired oxidation of the deposited electroactive material. Preferably, the oxygen content is less than 0.01% by volume, more preferably less than 0.001% by volume, based on the total volume of the gases used in steps (b) and (d).

[0081] The temperatures in steps (b) and (d) are any temperature effective to decompose the precursor to form the electroactive material. Preferably, the temperatures in steps (b) and (d) are independently in the range of 300°C to 800°C, or 350°C to 800°C, or 380°C to 700°C, or 380°C to 650°C, or 380°C to 600°C, or 380°C to 550°C, or 380°C to 500°C, or 400°C to 450°C, or 450°C to 500°C, or 350°C to 500°C, or 350°C to 450°C, or 380°C to 450°C. More preferably, the temperatures in steps (b) and (d) are each independently in the range of 380°C to 500°C, preferably 380°C to 450°C.

[0082] 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 150 kPa or less, or 120 kPa or less, or 110 kPa or less, or 100 kPa or less, or 90 kPa or less, or 80 kPa or less, or 70 kPa or less, or 60 kPa or less, or 50 kPa or less.

[0083] Preferably, the pressure in at least step (b) is maintained below 200 kPa. Preferably, the pressure in at least step (b) is maintained at 150 kPa or less, or 120 kPa or less, or 110 kPa or less, or 100 kPa or less, or 90 kPa or less, or 80 kPa or less, or 70 kPa or less, or 60 kPa or less, or 50 kPa or less.

[0084] Optionally, the pressure in both steps (b) and (d) may be maintained below 200 kPa. Optionally, the pressure in both steps (b) and (d) may be maintained at 150 kPa or less, or 120 kPa or less, or 110 kPa or less, or 100 kPa or less, or 90 kPa or less, or 80 kPa or less, or 70 kPa or less, or 60 kPa or less, or 50 kPa or less.

[0085] The pressure in step (b) may be lower than the pressure in step (d). For example, the pressure in step (b) may be maintained below 200 kPa, the pressure in step (d) may be greater than 200 kPa, or the pressure in step (b) may be maintained below 150 kPa, the pressure in step (d) may be greater than 150 kPa, or the pressure in step (b) may be maintained below 120 kPa, the pressure in step (d) may be greater than 120 kPa, or the pressure in step (b) may be maintained below 110 kPa, the pressure in step (d) may be greater than 110 kPa, or the pressure in step (b) may be maintained below 100 kPa and the pressure in step (d) may be greater than 100 kPa.

[0086] The reduction in pressure of step (b) compared to step (d) may be advantageous in situations where more control over deposition is required in the early stages of deposition, particularly when infiltrating particles that are highly microporous. As shown above, carrying out step (b) at a lower pressure results in increased diffusion of the precursors of the electroactive material, allowing access to the micropores and / or smallest mesopores prior to pyrolysis.

[0087] Alternatively, the pressure in step (d) may be lower than the pressure in step (b). For example, the pressure in step (b) may be greater than 200 kPa and the pressure in step (d) may be maintained below 200 kPa, or the pressure in step (b) may be greater than 150 kPa and the pressure in step (d) may be maintained below 150 kPa, or the pressure in step (b) may be greater than 120 kPa and the pressure in step (d) may be maintained below 120 kPa, or the pressure in step (b) may be greater than 110 kPa and the pressure in step (d) may be maintained below 110 kPa, or the pressure in step (b) may be greater than 100 kPa and the pressure in step (d) may be maintained below 100 kPa.

[0088] The reduction in pressure in step (d) compared to step (b) may be preferred in situations where more control over deposition is required at later stages of deposition, for example if the electroactive material occupies a high proportion of the pore volume of the porous particle, more control may be required at later stages to ensure that the precursor gas penetrates the remaining pore volume and therefore that the electroactive material is preferentially deposited within the interior pore volume and not on the exterior surface of the porous particle.

[0089] References to pressure in any step of the claimed processes refer to the absolute pressure in the reaction zone, which may include any suitable type of reactor vessel.

[0090] Deposition of the electroactive material by CVI results in the removal of by-products, especially by-product gases such as hydrogen. Step (c) preferably includes at least separation of the by-products from the intermediate particles formed in step (b). Separation of the by-products from the intermediate particles formed in step (b) can be achieved by flushing the reactor with an inert gas and / or by evacuating the reactor by reducing the pressure. For example, separation of the by-products from the intermediate particles formed in step (b) can be achieved by evacuating the reactor to a pressure of less than 100 kPa, or less than 80 kPa, or less than 60 kPa, or less than 40 kPa, or less than 20 kPa, or less than 10 kPa, or less than 5 kPa, or less than 2 kPa, or less than 1 kPa. Evacuating the reactor to low pressure can be effective not only to remove gas phase by-products, but also to desorb any by-products that may be adsorbed on the deposited electroactive material surface.

[0091] As discussed above, step (c) may optionally include forming a modifier material on the surface of the electroactive material deposited in step (b).

[0092] The modifier material formed in step (c) may optionally be a passivation layer formed on the surface of the electroactive material deposited in step (b). Thus, step (c) may further 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.

[0093] The passivation layer may be a native oxide layer. For example, a native oxide layer may be formed by exposing the surface of the electroactive material to a passivating agent selected from air or another oxygen-containing gas. When the first electroactive material is silicon, the passivation layer may include silicon oxide of the formula SiO x (where 0 < x ≦ 2). The silicon oxide is preferably amorphous silicon oxide. The formation of the native oxide layer is exothermic and thus requires careful process control to prevent overheating or even combustion of the particulate material. When the modifier material formed in step (c) is a native oxide layer, step (c) may include cooling the material formed in step (b) to less than 300 °C, preferably less than 200 °C, optionally less than 100 °C, before contacting the surface of the electroactive material domain with an oxygen-containing gas.

[0094] The passivation layer may be, for example, a nitride layer formed by exposing the surface of the electroactive material to a passivating agent selected from ammonia or another nitrogen-containing molecule, for example, prior to deposition of a second electroactive material layer. When the electroactive material is silicon, the passivation layer may include 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 °C to 700 °C, preferably 400 °C to 700 °C, more preferably 400 °C to 600 °C. The temperature can then be raised to the range of 500 °C to 1000 °C if necessary to nitride the surface (e.g., the formula SiN x(In the formula, x ≤ 4 / 3) a silicon nitride surface) may be formed. For example, when using ammonia, step (c) may be carried out at the same or a similar temperature as that used for depositing the electroactive material domains in step (b). Nitride passivation may sometimes be more preferable than oxide passivation. Stoichiometric nitrides (e.g., SiN x (In the formula, 0 < x ≤ 4 / 3)) are conductive, so the nitride intermediate layer functions as a conductive network that enables more rapid charging and discharging of the electroactive material. The nitride modifier material domains may also be thought to improve the capacity retention rate. Phosphine may also be used as a passivating agent as a phosphorus analog of ammonia.

[0095] The passivation layer may be, for example, a oxynitride layer formed by exposing the surface of the first electroactive material layer to a passivating agent containing ammonia (or another nitrogen-containing molecule) and oxygen gas before depositing the second electroactive material layer. When the first electroactive material layer is silicon, the first intermediate layer material has the formula SiO x N y (In the formula, 0 < x < 2, 0 < y < 4 / 3, and 0 < (2x + 3y) ≤ 4) may include silicon oxynitride. The silicon nitride is preferably amorphous silicon oxynitride.

[0096] The passivation layer may be a carbide layer. When the first electroactive material layer is silicon, the first intermediate layer may include silicon carbide of the formula SiC x (In the formula, 0 < x ≤ 1). The silicon carbide is preferably amorphous silicon carbide. The carbide layer may 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 an elevated temperature, for example, in the range of 250°C to 700°C. At lower temperatures, covalent bonds are formed between the electroactive material surface and the carbon-containing precursor, which is converted to a single layer of crystalline silicon carbide as the temperature rises. When the electroactive material domains contain silicon, the modifier material domains may include silicon carbide of the formula SiC x (In the formula, 0 < x ≤ 1).

[0097] The passivation layer may include an organic moiety covalently bonded to at least a portion of the electroactive material surface. For example, the modifier material domain may include a carbon-containing organic moiety covalently bonded to at least a portion of the electroactive material domain surface. For example, the modifier material domain may include a hydrocarbyl group covalently bonded to the electroactive material domain surface.

[0098] Suitable passivation agents 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 that contain an alkene, alkyne or carbonyl functional group, more preferably a terminal alkene, terminal alkyne, aldehyde or ketone group.

[0099] Preferred passivating agents include those having the following formula: (i)R 1 -CH=CH-R 1 , (ii)R 1 -C≡CR 1 , and (iii) O=CR 1 R 1 (In the formula, each R 1 independently represent H, an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, or two R 1 The group includes one or more compounds that form an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring.

[0100] Particularly preferred passivators include those having the formula: (i)CH 2 =CH-R 1 , and (ii) HC≡CR 1 (In the formula, R 1 is as defined above. 1 is non-substitutive.

[0101] Examples of suitable passivators include ethylene, propylene, 1-butene, butadiene, 1-pentene, 1,4-pentadiene, 1-hexene, 1-octene, styrene, divinylbenzene, acetylene, phenylacetylene, norbornene, norbornadiene and bicyclo[2.2.2]oct-2-ene. Optionally, mixtures of different passivators can also be used.

[0102] Passivating agents containing an alkene, alkyne or carbonyl group are believed to undergo an insertion reaction with M-H groups (where M represents an atom of the electroactive material) on the surface of the electroactive material to form a covalently passivated surface that is resistant to oxidation by air. When silicon is the electroactive material, the passivating reaction between the silicon surface and the passivating agent can be understood as a form of hydrosilylation as shown diagrammatically below. [ka]

[0103] Because hydride terminations can decompose to produce hydrogen gas, which can be detrimental to the electrode topography, it is preferred to replace the hydride terminations at the surface of the electroactive material domains with covalently bonded organic modifier material domains, such as carbon-containing organic moieties. Additionally, the Si-C bonds are believed to improve electrical conductivity.

[0104] Other suitable passivation agents include compounds that contain an active hydrogen atom bonded to oxygen, nitrogen, sulfur, or phosphorus. For example, the passivation agent may be an alcohol, an amine, a thiol, or a phosphine. The reaction of the -XH group with a hydride group on the surface of the electroactive material produces H 2 and the formation of a direct bond between X and the electroactive material surface.

[0105] Suitable passivators in this category include those having the following formula: (iv) HX-R 2 , and (v) HX-C(O)-R 1 (wherein X is O, S, NR 1 Or PR 1 Each R 1 are independently as defined above, and R 2 represents an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, or R 1 and R 2 taken together form an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring.

[0106] Preferably, X represents O or NH.

[0107] Preferably, R 2 represents an optionally substituted aliphatic or aromatic group having 2 to 10 carbon atoms. Amine groups may also be incorporated into 4- to 10-membered aliphatic or aromatic ring structures, such as in pyrrolidine, pyrrole, imidazole, piperazine, indole, or purine.

[0108] In step (c), contacting the electroactive material with the passivating agent may be carried out at a temperature in the range of 25°C to 700°C, preferably in the range of 50°C to 500°C, more preferably in the range of 100°C to 300°C.

[0109] The modifier material formed in step (c) may optionally comprise a pyrolytic carbon material deposited on the electroactive material surface by pyrolysis of a carbon-containing precursor, i.e., by chemical vapor infiltration (CVI). The deposition of pyrolytic carbon material in step (c) may be advantageous because it forms a conductive network between electroactive material domains that may facilitate electron transport within the composite particles. Step (c) may thus comprise contacting the intermediate particles from step (b) with a carbon-containing precursor, preferably a hydrocarbon, at a temperature effective to cause deposition of the pyrolytic carbon material in the pores of the intermediate particles.

[0110] Suitable hydrocarbons include polycyclic hydrocarbons containing 10 to 25 carbon atoms and optionally 1 to 3 heteroatoms, optionally the polycyclic aromatic hydrocarbons being selected from naphthalene, substituted naphthalenes such as dihydroxynaphthalene, anthracene, tetracene, pentacene, fluorene, acenaphthene, phenanthrene, fluoranthene, pyrene, chrysene, perylene, coronene, fluorenone, anthraquinone, anthrone and alkyl-substituted derivatives thereof. Suitable pyrolytic carbon precursors also include bicyclic monoterpenoids, optionally the bicyclic monoterpenoids being selected from camphor, borneol, eucalyptol, camphene, careen, sabinene, thujene and pinene. Further suitable pyrolytic carbon precursors include C 2 ~C 10 Included are hydrocarbons, optionally selected from alkanes, alkenes, alkynes, cycloalkanes, cycloalkenes, and arenes, such as methane, ethylene, propylene, limonene, styrene, cyclohexane, cyclohexene, α-terpinene, and acetylene. Other suitable pyrolytic carbon precursors include phthalocyanine, sucrose, starch, graphene oxide, reduced graphene oxide, pyrene, perhydropyrene, triphenylene, tetracene, benzopyrene, perylene, coronene, and chrysene. A preferred carbon precursor is acetylene.

[0111] Suitable temperatures for the deposition of the pyrolytic carbon material in step (c) range from 300°C to 800°C, or from 400°C to 700°C. For example, the temperature may be 680°C or less, or 660°C or less, or 640°C or less, or 620°C or less, or 600°C or less, or 580°C or less, or 560°C or less, or 540°C or less, or 520°C or less, or 500°C or less. The minimum temperature varies depending on the type of carbon precursor used. Preferably, the temperature is at least 300°C, or at least 350°C, or at least 400°C, or at least 450°C, or at least 500°C.

[0112] The carbon-containing precursor used in step (c) may be used in pure form or in a mixture diluted with an inert carrier gas such as nitrogen or argon. For example, the carbon-containing precursor may be used in an amount ranging from 0.1% to 100% by volume, or from 0.5% to 20% by volume, or from 1% to 10% by volume, or from 1% to 5% by volume, based on the total volume of the precursor and the inert carrier gas. The presence of oxygen should be minimal to prevent undesired oxidation of the deposited electroactive material. Preferably, the oxygen content is less than 0.01% by volume, more preferably less than 0.001% by volume, based on the total volume of the gas.

[0113] If a pyrolytic carbon material is deposited in step (c), the same compound can function as both the passivator and the pyrolytic carbon precursor. For example, if styrene is selected as the pyrolytic carbon precursor, it will also function as the passivator, provided that the intermediate particles from step (b) are not exposed to oxygen prior to contact with the styrene. In this case, the passivation and deposition of the conductive carbon material in the process can be carried out simultaneously, for example at a temperature in the range of 300°C to 700°C. Alternatively, the passivation and deposition of the conductive carbon material can be carried out sequentially, if the passivator and the pyrolytic carbon precursor are the same material, but the deposition of the pyrolytic carbon precursor is carried out at a higher temperature than the passivation. For example, the passivation can be carried out at a temperature in the range of 25°C to less than 300°C, and the deposition of the pyrolytic carbon can be carried out at a temperature in the range of 300°C to 700°C. These two steps can be suitably carried out sequentially by increasing the temperature while maintaining contact with the compound that functions as both the passivator and the pyrolytic carbon precursor. At lower temperatures (e.g., in the range of 25°C to less than 300°C), passivation would be the predominant process. As the temperature increases (e.g., to 300°C to 700°C), deposition of pyrolytic carbon would likely ensue.

[0114] Depending on the amount of electroactive material to be deposited in each step, the method of the present invention may be operated as a multi-pass process in which steps (c) and (d) are repeated as many times as necessary to deposit the target amount of electroactive material. For example, steps (c) and (d) may be performed 2-15 times, resulting in a total of 3-16 deposition steps of electroactive material, including repetitions of steps (b) and (d).

[0115] When repeating steps (c) and (d), the requirement that the pressure of at least one of steps (b) and (d) be maintained below 200 kPa should be interpreted as referring to step (b) or any one of steps (d). Preferably, the pressure of at least step (b) is maintained below 200 kPa.

[0116] Optionally, the pressure in step (b) and two or more of the repeated steps (d) may be maintained below 200 kPa. For example, the pressure in at least step (b) and at least one of steps (d) may be maintained below 200 kPa. Optionally, the pressure in all of step (b) and the repeated steps (d) may be maintained below 200 kPa.

[0117] When repeating steps (c) and (d), each process of step (c) and step (d) is independently as described above. For example, each repetition of step (c) may include the formation of the same or different modifier material, or modifier material may be optionally not formed at all in one or more steps. Similarly, the electroactive material deposited in each repetition of step (d) may be the same or different, and may also 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 repeated step (d) is silicon. More preferably, the electroactive material deposited in each of step (b) and repeated step (d) is silicon.

[0118] When steps (c) and (d) are repeated, the particles used during the repetition of step (c) are intermediate particles obtained from the preceding step (d). Thus, any reference herein to "particles from step (b)" in the description of step (c) should be interpreted as "particles from the preceding step (d)" when step (c) is optionally repeated.

[0119] A range of different electroactive material loadings in the composite particles may be obtained using the method of the present invention. For example, the amount of electroactive material (e.g. silicon) in the composite particles may range from 5% to 85% by weight, based on the total mass of the composite particle. Preferably, the amount of electroactive material in the composite particles is 10% to 85% by weight, or 15% to 85% by weight, or 20% to 80% by weight, or 25% to 80% by weight, or 30% to 75% by weight, or 35% to 75% by weight, or 40% to 70% by weight, or 45% to 65% by weight, based on the total mass of the composite particle. The total electroactive material loading in the composite particles is the sum of the electroactive material deposited in steps (b) and (d) (including repetitions of step (d)).

[0120] The amount of electroactive material (e.g., silicon) in the composite particles is preferably selected such that at least 20% and up 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%-80%, or 25%-75%, or 30%-70%, or 35%-65%, or 40%-60%, or 45%-55% of the internal pore volume of the porous particles. Within these preferred ranges, the remaining pore volume of the porous particles is effective to accommodate the expansion of the electroactive material during charging and discharging, without excess pore volume that does not contribute to the volumetric capacity of the particulate particles. However, the amount of electroactive material is also not so high as to prevent effective lithiation due to inadequate metal ion diffusion rates or due to inadequate expansion volume resulting in mechanical resistance to lithiation.

[0121] When the electroactive material is silicon, the amount of silicon in the composite particles is determined by the mass ratio of silicon to porous particles being [0.5 × P 1 ~1.9×P 1 ]:1, where P 1 is cm 3 Pore ​​volume is a dimensionless quantity that has a measure of the total pore volume of micropores and mesopores in a porous particle, expressed as g / g (for example, if a porous particle has a volume of 1.2 cm 3 / g, then P 1 = 1.2). This relationship takes into account the density of silicon and the pore volume of the porous particles and defines the weight ratio of silicon at which the pore volume is approximately 20% to 82% occupied.

[0122] 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 only the porous particles, and the composition of the composite particles.

[0123] The silicon content is preferably determined by ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy). Many ICP-OES instruments are commercially available, such as the iCAP™ 7000 series of ICP-OES analyzers available from ThermoFisher Scientific. The carbon content (and optionally the hydrogen, nitrogen and oxygen content) in the composite particles and in the porous carbon particles alone is preferably determined by IR absorption. A suitable instrument for determining the carbon, hydrogen, nitrogen and oxygen content is the TruSpec™ Micro elemental analyzer available from Leco Corporation.

[0124] Preferably, at least 90% by weight, more preferably at least 95% by weight, even more preferably at least 98% by weight of the electroactive material in the composite particles is located within the internal pore volume of the porous particles, such that none or almost none of the electroactive material is located on the external surface of the composite particles. As discussed above, deposition of the electroactive material during the CVI process occurs on the porous particle surface. Given that the internal surface area of ​​the porous particles is very high, the reaction kinetics of the CVI process ensure that 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 the requirement that the pressure in at least one of steps (b) and (d) is maintained below 200 kPa or within the preferred pressure range discussed above.

[0125] The method of the invention optionally further comprises: (e) forming a plurality of modifier material domains in the pores and / or on the exterior surface of the composite particles from step (d); Further includes:

[0126] Step (e) is performed immediately after the last electroactive material deposition step (i.e., step (d) or the last iteration of step (d) if steps (c) and (d) are repeated). The formation of the modifier material domains in step (e) is similar to step (c) described above, except that step (e) is performed after the last electroactive material deposition step (the last step (d)), whereas step (c) is performed between successive electroactive material deposition steps. Any modifier materials and deposition conditions disclosed herein with respect to step (c) also apply to step (e).

[0127] The modifier material domains formed in step (e) may comprise the same or a different modifier material as the modifier material domains formed in step (c).

[0128] Optionally, step (e) includes contacting the composite particles from step (d) with a passivation agent. The preferred passivation agents and passivation conditions set forth above in relation to step (c) also apply to the passivation in step (e).

[0129] Optionally, step (e) includes depositing a lithium-ion permeable material within the pores and / or on the outer surface of the composite particles from step (d), which provides further improvement in the performance of the composite particles when used as an electroactive material for lithium-ion batteries by reducing the surface area of ​​the composite particles and by blocking electroactive material domains from access to electrolyte.

[0130] The lithium ion permeable material may be deposited immediately after the last electroactive material deposition step (i.e., step (d), or after the last step (d) if steps (c) and (d) are repeated one or more times). Alternatively, the lithium ion permeable material may be deposited after first carrying out a passivation step in step (e), as discussed above.

[0131] A suitable lithium ion permeable material is a pyrolytic carbon material, which can be obtained by chemical vapor infiltration (CVI) method, i.e. by pyrolysis of a volatile carbon-containing gas (e.g. ethylene) on the surface of the composite particles.

[0132] A suitable process for depositing a pyrolyzable carbon material includes combining the composite particles from step (d) with a pyrolyzable carbon precursor and heating the pyrolyzable carbon precursor to a temperature effective to cause deposition of a pyrolyzable conductive carbon material within the pores and / or on the exterior surfaces of the composite particles.

[0133] The preferred pyrolyzable carbon precursors and pyrolysis conditions set forth above in relation to step (c) also apply to the formation of the pyrolyzable carbon material in step (e).

[0134] When the lithium ion permeable material is a pyrolytic carbon material, the same compound may function as both the passivator and the pyrolytic carbon precursor in step (e). Suitable conditions for passivating and forming a pyrolytic carbon material using the same compound as the passivator and the pyrolytic carbon precursor in step (e) are the same as those set forth above in connection with step (c).

[0135] Alternatively, different compounds may be used as the passivating agent and as the pyrolyzable carbon precursor in step (e), for example the passivating agent may be styrene and the pyrolyzable carbon precursor may be a compound such as cyclohexane that is capable of forming a pyrolyzable carbon material but is unable to passivate the electroactive material surface.

[0136] The composite particles obtained by the method of the present invention may be characterized by their performance under thermogravimetric analysis (TGA) in air, which is based on the principle that when an electroactive material is oxidized in air and at elevated temperature, a weight gain is observed.

[0137] As defined herein, "surface silicon" is calculated from the initial mass increase in a TGA trace from a minimum between 150°C and 500°C to a maximum mass measured in the temperature range between 550°C and 650°C, the TGA being performed in air at a heating rate of 10°C / min. This mass increase is assumed to result from oxidation of the surface silicon and is therefore calculated according to the following formula: Y = 1.875 × [(M max -M min ) / M f ]×100% where Y is the percentage of surface silicon as a proportion of the total silicon in the sample, and M max is the maximum mass of the sample measured in the temperature range between 550°C and 650°C, and M min is the minimum mass of the sample at temperatures greater than 150°C and less than 500°C, and M fThe percentage of surface silicon as a proportion of the total amount of silicon can be determined according to the mass of the sample at the completion of oxidation at 1400 °C. For completeness, 1.875 is the mass of the sample at 1400 °C. 2 SiO 2 (i.e., the molar mass ratio of the SiO formed to the mass increase due to the addition of oxygen) 2 It will be understood that the mass ratio of the cation exchange ratio (A) to the cation exchange ratio (C) is the mass ratio of the cation exchange ratio (C). Typically, TGA analysis is performed using a sample size of 10 mg ± 2 mg.

[0138] One advantage of the method of the present invention is that the low pressure CVI process produces composite particles with 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 amount of silicon in the composite particles, and may be at least 22% by weight, or at least 25% by weight, at least 30% by weight of silicon, or at least 35% by weight of silicon, or at least 40% by weight of silicon, or at least 45% by weight of the total amount of silicon in the composite particles.

[0139] In addition to surface silicon content, the silicon-containing composite particles obtained by the method of the present invention have a low content of coarse bulk silicon as determined by TGA. Coarse bulk silicon is defined herein as silicon that undergoes oxidation above 800°C as determined by TGA, where the TGA is performed in air at a heating rate of 10°C / min. Thus, the coarse bulk silicon content is calculated according to the following formula: Z = 1.875 × [(M f -M 800 ) / M f ]×100% (where Z is the percentage of unoxidized silicon at 800°C, M 800 is the mass of the sample at 800 °C, M fis the mass of ash at the completion of oxidation at 1400 °C). For the purposes of this analysis, any mass increase above 800 °C is determined as the conversion of silicon to SiO 2 The total mass at the end of oxidation is SiO 2 Assume that.

[0140] Silicon that undergoes oxidation above 800° C. is less desirable. In the composite particles prepared according to the methods of the present invention, the coarse bulk silicon content is typically 10% or less by weight of the total amount of silicon in the composite particle, and may be 8% or less, or 6% or less, or 5% or less, or 4% or less, or 3% or less, or 2% or less, or 1.5% or less by weight of the total amount of silicon in the composite particle.

[0141] Preferably, at least 30% by weight of the silicon is surface silicon and not more than 10% by weight of the silicon is crude bulk silicon, both as determined by TGA. More preferably, at least 35% by weight of the silicon is surface silicon and not more than 8% by weight of the silicon is crude bulk silicon, both as determined by TGA. More preferably, at least 40% by weight of the silicon is surface silicon and not more than 5% by weight of the silicon is crude bulk silicon, both as determined by TGA. More preferably, at least 45% by weight of the silicon is surface silicon and not more than 2% by weight of the silicon is crude bulk silicon, both as determined by TGA.

[0142] The composite particles obtained according to the method of the present invention are preferably 2 / g or less, or 250m 2 / g or less, or 200m 2 / g or less, or 150m 2 / g or less. More preferably, it has a BET surface area of ​​100 m 2 / g or less, or 80m 2 / g or less, or 60m 2 / g or less, or 40m 2 / g or less, or 30m 2 / g or less, or 25m 2 / g or less, or 20m2 / g or less, or 15m 2 / g or less, or 10m 2 / g or less, or 5m 2 / g or less. Generally, a low BET surface area is preferred to minimize the formation of a solid electrolyte interfacial (SEI) layer on the surface of the composite particles during the first charge-discharge cycles of the anode. However, an excessively low BET surface area can result in unacceptably low charge rates and capacities due to the inaccessibility of the metal ions to the bulk of the electroactive material in the surrounding electrolyte. The BET surface area is preferably at least 0.1 m 2 / g, or at least 1m 2 / g, or at least 2m 2 / g, or at least 5m 2 For example, the BET surface area of ​​a composite particle is 0.1 m 2 / g~100m 2 / g, or 0.1m 2 / g~80m 2 / g, or 0.5m 2 / g~60m 2 / g, or 0.5m 2 / g~40m 2 / g, or 1m 2 / g~30m 2 / g, or 1m 2 / g~25m 2 / g, or 2m 2 / g~20m 2 / g.

[0143] The reaction process may be carried out using any reactor capable of contacting solids and gases at elevated temperatures. The porous particles and the resulting composite particles may be present in the reactor in the form of a fixed bed of particles or in the form of a moving or stirred bed of particles.

[0144] In a second aspect, the present invention provides composite particles obtainable according to the method of the first aspect of the invention.

[0145] In a third aspect of the invention, there is provided a composition comprising a composite particle according to the second aspect of the invention and at least one other component. In particular, there is provided a composition comprising a composite particle according to the second aspect of the invention and at least one other component selected from (i) a binder, (ii) a conductive additive, and (iii) an additional particulate electroactive material. The composition according to the third aspect of the invention is useful as an electrode composition and can thus be used to form the active layer of an electrode.

[0146] The composition may be a hybrid electrode composition comprising the composite particles and at least one additional particulate electroactive material. Examples of the additional particulate electroactive material include graphite, hard carbon, silicon, tin, germanium, aluminum, and lead. The at least one additional particulate electroactive material is preferably selected from graphite and hard carbon. The at least one additional particulate electroactive material is most preferably graphite.

[0147] In the case of a hybrid electrode composition, the composition preferably comprises from 3% to 60% by weight, or from 3% to 50% by weight, or from 5% to 50% by weight, or from 10% to 50% by weight, or from 15% to 50% by weight of composite particles according to the second aspect of the present invention, based on the total dry weight of the composition.

[0148] The at least one additional particulate electroactive material is suitably present in an amount of from 20% to 95% by weight, or from 25% to 90% by weight, or from 30% to 750% by weight of the at least one additional particulate electroactive material.

[0149] The at least one additional particulate electroactive material preferably has a diameter in the range of 10 μm to 50 μm, preferably 10 μm to 40 μm, more preferably 10 μm to 30 μm, most preferably 10 μm to 25 μm, for example 15 μm to 25 μm. 50 It has a particle size.

[0150] D of at least one additional particulate electroactive material 10The particle size is preferably at least 5 μm, more preferably at least 6 μm, more preferably at least 7 μm, more preferably at least 8 μm, more preferably at least 9 μm, and even more preferably at least 10 μm.

[0151] D of at least one additional particulate electroactive material 90 The particle size is preferably at most 100 μm, more preferably at most 80 μm, more preferably at most 60 μm, more preferably at most 50 μm, most preferably at most 40 μm.

[0152] The at least one additional particulate electroactive material is preferably selected from carbon-containing particles, graphite particles, and / or hard carbon particles, where the graphite particles and hard carbon particles have a D in the range of 10 μm to 50 μm. 50 More preferably, the at least one additional particulate electroactive material is selected from graphite particles, wherein the graphite particles have a D in the range of 10 μm to 50 μm. 50 It has a particle size.

[0153] The composition may be a non-hybrid (i.e., "highly loaded") electrode composition that is substantially free of additional particulate electroactive material. In this context, the term "substantially free of additional particulate electroactive material" should be interpreted to mean that the composition contains less than 15 wt. %, preferably less than 10 wt. %, preferably less than 5 wt. %, preferably less than 2 wt. %, more preferably less than 1 wt. %, more preferably less than 0.5 wt. %, of any additional electroactive material (i.e., additional material capable of inserting and releasing metal ions during charging and discharging the battery), based on the total dry weight of the composition.

[0154] A "highly loaded" electrode composition of this type preferably comprises at least 50% by weight, or at least 60% by weight, or at least 70% by weight, or at least 80% by weight, or at least 90% by weight of the composite particles of the second aspect of the invention, based on the total dry weight of the composition.

[0155] The composition may optionally include a binder. The binder functions to adhere the composition to the current collector and maintain the integrity of the composition. Examples of binders that may be used according to the present invention include polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, carboxymethyl cellulose (CMC), modified carboxymethyl cellulose (mCMC), sodium carboxymethyl cellulose (Na-CMC), polyvinyl alcohol (PVA), alginates and their alkali metal salts, styrene-butadiene rubber (SBR), and polyimides. The composition may include a mixture of binders. Preferably, the binder includes a polymer selected from polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0156] The binder may suitably be present in an amount of from 0.5% to 20% by weight, preferably from 1% to 15% by weight, preferably from 2% to 10% by weight, most preferably from 5% to 10% by weight, based on the total dry weight of the composition.

[0157] The binder may optionally be present in combination with one or more additives that modify the properties of the binder, such as crosslinking promoters, coupling agents, and / or adhesion promoters.

[0158] The composition may optionally include one or more conductive additives. Preferred conductive additives are non-electroactive materials that are included to improve electrical conductivity between the electroactive components of the composition and between the electroactive components of the composition and the current collector. The 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.

[0159] The one or more conductive additives may suitably be present in a total amount of from 0.5% to 20% by weight, preferably from 1% to 15% by weight, preferably from 2% to 10% by weight, most preferably from 5% to 10% by weight, based on the total dry weight of the composition.

[0160] In a fourth aspect, the present invention provides an electrode comprising composite particles according to the second aspect of the invention in electrical contact with a current collector. The particulate material used to manufacture the electrode of the fourth aspect of the invention may be in the form of a composition according to the third aspect of the invention.

[0161] The term current collector as used herein refers to any conductive substrate capable of conducting electrical 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 typically have the form of a foil or mesh having a thickness of 3 μm to 500 μm. The particulate material of the present invention can be applied to one or both sides of the current collector, preferably to a thickness ranging from 10 μm to 1 mm, for example, from 20 μm to 500 μm, or from 50 μm to 200 μm.

[0162] The electrode of the fourth aspect of the invention may be prepared by combining the particulate material of the 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 to form an electrode layer on the surface of the current collector. Further steps such as heat treatment to harden any binder and / or calendaring the electrode layer may optionally be carried out. The electrode layer suitably has a thickness in the range of 20 μm to 2 mm, preferably 20 μm to 1 mm, preferably 20 μm to 500 μm, preferably 20 μm to 200 μm, preferably 20 μm to 100 μm, preferably 20 μm to 50 μm.

[0163] Alternatively, the slurry can be formed into a free-standing film or mat comprising the particulate material of the present invention, for example, by casting the slurry onto a suitable casting template, removing the solvent, and then removing the casting template. The resulting film or mat has the form of a free-standing agglomerate, which can then be adhered to a current collector by known methods.

[0164] The electrode of the fourth aspect of the invention may be used as the anode of a metal-ion battery.Thus, in a fifth aspect, the invention provides a rechargeable metal-ion battery comprising an anode comprising an 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.

[0165] The metal ions are preferably lithium ions. More preferably, the rechargeable metal ion batteries of the present invention are lithium ion batteries, and the cathode active material is capable of releasing and accepting lithium ions.

[0166] The cathode active material is preferably a metal oxide-based composite. Examples of suitable cathode active materials include LiCoO 2 , LiCo 0.99 Al 0.01 O 2 , LiNiO 2 , LiMnO 2 , LiCo 0.5 Ni 0.5 O 2 , LiCo 0.7 Ni 0.3 O 2 , LiCo 0.8 Ni 0.2 O 2 , LiCo 0.82 Ni 0.18 O 2 , LiCo 0.8 Ni 0.15 Al 0.05 O 2 , LiNi 0.4 Co 0.3 Mn 0.3 O 2 , and LiNi 0.33Co 0.33 Mn 0.34 O 2 The cathode current collector typically has a thickness of 3 μm to 500 μm. Examples of materials that can be used as the cathode current collector include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0167] The electrolyte is preferably a non-aqueous electrolyte containing a metal salt, such as a lithium salt, and may include, but is not limited to, a non-aqueous electrolyte, a solid electrolyte, and an inorganic solid electrolyte. Examples of non-aqueous electrolytes that may be used include aprotic organic solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, sulfolane, methylsulfolane, and 1,3-dimethyl-2-imidazolidinone.

[0168] Examples of organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionically dissociable groups.

[0169] Examples of inorganic solid electrolytes include Li 5 NI 2 , Li 3 N, LiI, LiSiO 4 , Li 2 SiS 3 , Li 4 SiO 4 , LiOH, and Li 3 PO 4 and the like.

[0170] The lithium salt is preferably soluble in the selected solvent or mixture of solvents. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiBC 4 O 8 , LiPF 6 , LiCF 3 SO 3 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , C.H. 3 SO 3 Li, and CF 3 SO 3 Li is one example.

[0171] When the electrolyte is a non-aqueous organic solution, the metal ion battery preferably includes a separator inserted between the anode and the cathode. The separator is typically formed of an insulating material having high ion permeability and high mechanical strength. The separator typically has a pore size of 0.01 μm to 100 μm and a thickness of 5 μm to 300 μm. An example of a suitable electrode separator is a microporous polyethylene film.

[0172] The separator may be replaced with a polymer electrolyte material, in which case the polymer electrolyte material is present in both the composite anode layer and the composite cathode layer. The polymer electrolyte material may be a solid polymer electrolyte or a gel-type polymer electrolyte.

Claims

1. 1. A method for preparing composite particles, comprising: (a) The total pore volume of micropores and mesopores measured by nitrogen gas adsorption is 0.4 cm ３ / g ~ 2.2 cm ３ providing a plurality of porous particles comprising micropores and / or mesopores, wherein the micropores and / or mesopores are in the range of .mu.m / g; (b) contacting the porous particles with a precursor of an electroactive material at a temperature effective to cause deposition of an electroactive material in the pores of the porous particles to form intermediate particles; (c) interrupting the deposition of the electroactive material and separating by-products from the intermediate particles; (d) contacting the intermediate particles from step (c) with a precursor of an electroactive material at a temperature effective to cause further deposition of the electroactive material in the pores of the intermediate particles; Including, The pressure in at least one of steps (b) and (d) is maintained at less than 200 kPa; method.

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

3. The method of claim 1 or claim 2, wherein the porous particles comprise a conductive carbon material.

4. The porous particles are 0.45 cm ３ / g ~ 2.2 cm ３ / g, or 0.5 cm ３ / g to 2cm ３ / g, or 0.55 cm ３ / g to 2cm ３ / g, or 0.6 cm ３ / g ~ 1.8 cm ３ / g, or 0.65 cm ３ / g ~ 1.8 cm ３ / g, or 0.7 cm ３ / g ~ 1.6 cm ３ / g, or 0.7 cm ３ / g to 1.5 cm ３ / g, or 0.7 cm ３ / g ~ 1.4 cm ３ 10. The method of claim 1, wherein the SiO2 has a total volume of micropores and mesopores in the range of 1 / g.

5. PD of the porous particles ５０ 2. The method of claim 1, wherein the pore size is 30 nm or less, or 25 nm or less, or 20 nm or less, or 15 nm or less, or 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less, or 1.5 nm or less.

6. PD of the porous particle skeleton ３０ 2. The method of claim 1, wherein the pore size is 25 nm or less, or 20 nm or less, or 15 nm or less, or 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less, or 1 nm or less.

7. The porous particles have a D in the range of 0.5 μm to 30 μm, or 1 μm to 25 μm, or 1 μm to 20 μm, or 2 μm to 25 μm, or 2 μm to 20 μm, or 2 μm to 18 μm, or 2 μm to 15 μm, or 2 μm to 12 μm, or 2.5 μm to 15 μm, or 2.5 μm to 12 μm, or 2 μm to 10 μm. ５０ The method of claim 1 , wherein the particle size is 0.05 μm or less.

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

35.

9. The porous particles are 100 mm ２ / g to 4000m ２ / g, or 500m ２ / g to 4000m ２ / g, or 750m ２ / g~3500m ２ / g, or 1000m ２ / g~3250m ２ / g, or 1000m ２ / g to 3000m ２ / g, or 1000m ２ / g~2500m ２ / g, or 1000m ２ / g to 2000m ２ 10. The method of claim 1, wherein the sintered body has a BET surface area in the range of 1 / g.

10. 10. The method of claim 1, wherein the electroactive material deposited in at least one of steps (b) and (d) is silicon.

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

12. The silicon-containing precursor is silane (SiH ４ ), disilane (Si ２ H ６ ), trisilane (Si ３ H ８ ), tetrasilane (Si ４ H １０ ), methylsilane, dimethylsilane, and chlorosilane.

13. 2. The method of claim 1, wherein the temperatures of steps (b) and (d) are independently in the range of from 300°C to 800°C, or from 350°C to 800°C, or from 400°C to 700°C, or from 400°C to 650°C, or from 400°C to 600°C, or from 400°C to 550°C, or from 400°C to 500°C, or from 400°C to 450°C, or from 450°C to 500°C, or from 350°C to 500°C, or from 350°C to 450°C, or from 380°C to 450°C.

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

15. 15. The method of claim 14, wherein the pressure of at least step (b) is maintained at 150 kPa or less, or 120 kPa or less, or 110 kPa or less, or 100 kPa or less, or 90 kPa or less, or 80 kPa or less, or 70 kPa or less, or 60 kPa or less, or 50 kPa or less.

16. 10. The method of claim 1, wherein step (c) comprises separating by-products from the intermediate particles.

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

18. 20. The method of claim 17, wherein step (c) comprises contacting the intermediate particles from step (b) with a passivating agent.

19. 20. The method of claim 18, wherein the passivating agent is selected from (i) an oxygen-containing gas, (ii) ammonia, (iii) a gas comprising ammonia and oxygen, and (iv) phosphine.

20. The passivation agent is (i)R １ -CH=CH-R １ 、 ())) １ .≡.!R １ 、 (iii)O=CR １ R １ 、 (iv) HX-R ２ , and (v)HX-C(O)-R １ (Wherein, X is O, S, NR １ or PR １ indicates, Each R １ independently represent H or an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, or two R １ The group forms an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring; R ２ represents an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, or R １ and R ２ together form an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring; 18. The method of claim 17.

21. 21. The method of any one of claims 17 to 20, wherein step (c) comprises contacting the intermediate particles from step (b) with a carbon-containing precursor at a temperature effective to cause deposition of a pyrolyzable carbon material in the pores of the intermediate particles.

22. 10. The method of claim 1, wherein steps (c) and (d) are repeated one or more times.

23. (e) forming a plurality of modifier material domains in the pores and / or on the exterior surface of the composite particles from step (d); The method of claim 1 further comprising:

24. 24. The method of claim 23, wherein step (e) comprises contacting the surfaces of the composite particles from the last step (d) with a passivating agent.

25. 25. The method of claim 23 or 24, wherein step (e) comprises combining the composite particles from step (d) with a pyrolytic carbon precursor and heating the pyrolytic carbon precursor to a temperature effective to cause deposition of a pyrolytic conductive carbon material within the pores and / or on the exterior surfaces of the composite particles.

26. Composite particles obtainable by the method of claim 1.

27. 27. A composition comprising the composite particles of claim 26 and at least one other component.

28. 28. An electrode comprising the composite particle of claim 26 or the composition of claim 27.

29. 29. A rechargeable metal-ion battery comprising the electrode of claim 28.