Electroactive materials for metal-ion batteries

Abstract

A particulate electroactive material comprising a plurality of composite particles is provided.SOLUTION: The present invention relates to a particulate electroactive material comprising a plurality of composite particles, the composite particles comprising: (a) a porous-carbon framework comprising micropores and mesopores, wherein the micropores and mesopores have a total volume of from 0.5 to 1. 5cm3 / g; and (b) silicon located at least within the micropores of the porous-carbon framework. It is an active carbon material obtained by pyrolysis of a plant source comprising at least 25wt% lignin on a dry basis followed by activation with steam or carbon dioxide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates generally to 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 cell phones and laptops, and are increasingly being applied to 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 to mean that the battery is placed across a load, such that the anode is the negative electrode. When a metal-ion battery is charged, metal ions are transported from the metal-ion-containing cathode layer through the electrolyte to the anode and inserted into the anode material. The term "battery" is used herein to refer to both devices with a single anode and a single cathode, as well as devices with 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. When a graphite anode is charged, lithium intercalates between the graphite layers, forming a charge-discharge charge according to the empirical formula L ixC6 (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 a somewhat lower practical capacity (approximately 340 to 360 mAh / g). Other materials, such as silicon, tin, and germanium, can intercalate lithium at significantly higher capacities than graphite, but have difficulty maintaining sufficient capacity over many charge-discharge cycles, preventing their widespread commercial use.

[0004] In particular, silicon has a very high capacity for lithium and has therefore been identified as a promising alternative to graphite for the fabrication of rechargeable metal-ion batteries with high gravimetric and volumetric capacities (see, for example, Non-Patent Document 1). At room temperature, silicon has a (Li 15 Silicon has a theoretical maximum specific capacity of approximately 3,600 mAh / g (based on Si4). However, the intercalation of lithium into bulk silicon significantly increases the volume of the silicon material, up to 400% of its original volume, once the silicon is lithiated to its maximum capacity. Repeated charge-discharge cycles induce significant mechanical stress in the silicon material, resulting in fracture and delamination of the silicon anode material. The volumetric shrinkage of silicon particles during delithiation can lead to loss of electrical contact between the anode material and the current collector. To make matters worse, the solid electrolyte interfacial (SEI) layer that forms on the silicon surface lacks sufficient mechanical resistance to accommodate the expansion and contraction of the silicon. As a result, the newly exposed silicon surface leads to further electrolyte decomposition, an increase in the thickness of the SEI layer, and irreversible lithium consumption. These failure mechanisms collectively result in an unacceptable loss of electrochemical capacity over successive charge-discharge cycles.

[0005] Many approaches have been proposed to overcome the problems associated with the volume changes observed when charging silicon-containing anodes. It has been reported that fine silicon structures with cross-sectional areas of approximately 150 nm or less, such as silicon films and silicon nanoparticles, are more resistant to volume changes during charging and discharging than silicon particles in the micron size range. However, none of these are suitable for commercial-scale applications in their unmodified form; nanoscale particles are difficult to prepare and handle, and silicon films do not provide sufficient bulk capacitance.

[0006] U.S. Patent No. 5,999,623 discloses that improved capacity retention can be achieved with silicon particles having a high aspect ratio, i.e., the ratio between the largest and smallest dimensions of the particle. The small cross-section of such particles reduces structural stress on the material due to volume changes during charge and discharge. However, such particles can be difficult and costly to manufacture and can be fragile. In addition, the large surface area can lead to excessive SEI formation, resulting in excessive capacity loss during the first charge and discharge cycles.

[0007] It is also generally known that electroactive materials such as silicon can be deposited within the pores of porous carrier materials, such as activated carbon materials. These composite materials offer some of the beneficial charge-discharge properties of nanoscale silicon particles while avoiding the difficulties of handling nanoparticles. Non-Patent Document 2 discloses silicon-carbon composite materials in which a porous carbon substrate provides a conductive framework with silicon nanoparticles uniformly distributed and deposited within the pore structure of the substrate. While this composite material has improved capacity retention over multiple charging cycles, the initial capacity of the composite in mAh / g is shown to be significantly lower than that of silicon nanoparticles.

[0008] Patent Document 2 discloses an active material comprising a carbon-based scaffold with small pores branching off from several large pores, where an electroactive material (such as silicon) is indiscriminately located in the walls of both the large and small pores, as well as on the outer surface of the carbon-based scaffold.

[0009] Silicon suboxide materials (e.g., SiOx where 0 < x < 2) have been used in “hybrid” electrodes that mainly contain graphite as the active material. However, due to the expansion of SiO during lithiation, and the relatively high irreversible lithium loss during the first charge cycle, the maximum loading of SiO x is typically about 10 wt% of the total electroactive material in the electrode. Therefore, there is a need for a high-capacity electrode material that has a lithiation capacity comparable to silicon oxide, but reduces the expansion and capacity loss during the first charge cycle. x The desirable expansion characteristics of the electrode material must be obtained along with other important characteristics. In particular, a commercially viable alternative electrode material needs to provide the advantages of high lithiation capacity along with high capacity retention over a number of charge-discharge cycles. Additionally, it is important that any new electroactive material be easily substitutable for known materials in conventional electrode fabrication processes. These processes typically rely on calendaring of the electrode material on the current collector to increase the density of the electrode layer and improve the space utilization within the battery design. Porous materials are weak against crushing during electrode fabrication, resulting in impaired electrochemical performance. Therefore, it is particularly desired that new electrochemical materials have sufficient structural strength along with increased electrochemical storage capacity and reversible capacity retention.

[0010] The 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 very porous conductive particulate material such as a porous carbon material.

[0011]

[0012] ​For example, Patent Documents 3 and 4 report that the improved electrochemical performance of these materials can be attributed to the way in which the electroactive material is placed within the porous material in the form of small domains with dimensions of approximately a few nanometers or less. It is believed that these fine electroactive structures 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 materials exhibit good reversible capacity retention over multiple charge-discharge cycles. Second, by controlling the silicon loading within the porous carbon framework so 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 within it. Furthermore, as mentioned above, by placing nanoscale silicon domains within small mesopores and / or micropores, the electrolyte can only access a small area of ​​the silicon surface, thus limiting SEI formation. Further exposure of the silicon during subsequent charge-discharge cycles is substantially prevented, preventing SEI formation from being a significant failure mechanism leading to capacity loss. This is in clear contrast to the excessive SEI formation that characterizes the materials disclosed, for example, by [2] (see above).

[0013] It has been determined herein that improved electrochemical performance of composite materials comprising silicon and porous carbon can be obtained when the porous carbon material is an activated carbon material derived from certain plant sources. Specifically, it has been determined that improved electrochemical performance can be obtained when the porous carbon material is an activated carbon material formed by pyrolysis of lignin-rich plant sources. Furthermore, it has been determined that the performance of these composite materials depends on the method by which the porous carbon material is activated, with activation with water vapor or CO2 providing additional benefits. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] WO2007 / 083155 [Patent Document 2] JP2003-100284 [Patent Document 3] WO2020 / 095067 [Patent Document 4] WO2020 / 128495 [Patent Document 5] WO2021 / 048556 [Non-patent literature]

[0015] [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] Guo et al., Journal of Materials Chemistry A, 2013, pp.14075-14079 [Non-patent document 3] PA Webb and C. Orr in “Analytical Methods in Fine Particle Technology”, 1997, Micromeritics Instrument Corporation, ISBN 0-9656783-0 [Non-patent document 4] Bardet et al., Phys. Chem. Chem. Phys. (2016), 18, 18201 Summary of the Invention

[0016] In a first aspect, the present invention provides a particulate material comprising a plurality of composite particles, the composite particles comprising: (a) a porous carbon framework comprising micropores and / or mesopores, the micropores and mesopores being 1 cm 3 / g of total pore volume measured by gas adsorption, P 1 represents a number having a value between 0.5 and 1.5, porous carbon framework; (b) multiple elemental nanoscale silicon domains located within the micropores and / or mesopores of the porous carbon framework; wherein the porous carbon framework is an activated carbon material obtained by pyrolysis of a plant source containing at least 25 wt% lignin on a dry weight basis, followed by activation with water vapor or carbon dioxide.

[0017] Thus, the present invention generally relates to particulate materials in which silicon partially occupies the pore volume of a highly porous carbon framework. As used herein, the term "nanoscale silicon domains" refers to nanoscale bodies of elemental silicon having maximum dimensions determined by the location of the silicon within the micropores and / or mesopores of the porous carbon framework.

[0018] The porous carbon framework used in accordance with the present invention is a form of activated carbon. As used herein, the term "activated carbon" refers to a carbonaceous material that has been physically or chemically treated to increase its porosity and surface area. Chemical activation or physical activation (i.e., high-temperature steam or CO2) mechanisms are among the most common methods used to produce activated carbon.

[0019] The present invention is based on the discovery that activated carbon produced by pyrolysis and physical activation (steam or CO2) of plant sources containing at least 25 wt% lignin (dry weight basis) provides superior electrochemical performance when compared to porous carbon materials derived from other plant or non-plant sources (such as, for example, pyrolysis of polymeric or resinous materials) and / or when chemical (i.e., not steam or CO2) activation methods are used to prepare the porous carbon material.

[0020] Previous research in this field has primarily focused on the pore volume and pore size distribution of porous carbon frameworks as key factors in determining the electrochemical performance of similar materials. For example, it is generally known that electroactive materials, such as silicon, can be deposited within the pores of porous carbon frameworks by chemical vapor impregnation (CVI), and that a wide variety of composite particle structures can be obtained through variation of the pore volume and pore size distribution of the porous carbon framework. However, there are other properties of porous carbon materials that can significantly affect the morphology and structure of nanoscale silicon domains. These include factors such as pore shape and the tortuosity and contractility of the pore structure, i.e., pore structural features that characterize how the pore volume is interconnected. In porous carbon materials derived from pyrolysis of plant sources with high lignin content, these additional features of the pore structure have been found to be optimized for the formation of composite particles with high gravimetric and volumetric capacities as well as high capacity retention over multiple charge / discharge cycles.

[0021] Without being bound by theory, it is believed that pyrolysis of plant sources with high lignin content results in carbonized materials with more closely spaced graphite platelets than those obtained from other carbon-containing precursor materials (e.g., plant- or polymer-based materials). This results in the formation of a higher proportion of micropores in the pyrolyzed material. Furthermore, due to the higher density of lignin in the plant precursor, the pore network structure is believed to have a higher degree of tortuosity and contractility. Physical activation of the pyrolyzed material (using steam or CO2) then increases the pore volume by removing nanoscale carbon regions within the pore walls. This allows for a larger total pore volume to be achieved while maintaining a moderate level of micropore-sized space accessible to connecting channels.

[0022] It should be further appreciated that the combination of higher density lignin in the plant precursor and activation with water vapor or CO2 provides a relatively high proportion of "ink-bottle-shaped" pores, or more generally, a proportion of mesopore space (sub-10 nm) accessible only through one or more narrow openings having widths smaller than the mesopores. Ink-bottle-shaped pores are those where larger dimensional pore space is accessible only through much smaller openings. Such pore structures are believed to promote the formation of partially filled pore space (e.g., pore walls with deposited Si coatings less than 2 nm deep) and subsequent blocking (capping) of the openings, preventing the pore space from being completely filled with silicon.

[0023] In the chemical activation method, plant-source materials are impregnated with a chemical activator (e.g., KOH, H3PO4, ZnCl2). The plant source is typically impregnated before pyrolysis, which occurs simultaneously with activation; however, the plant source may also be carbonized before chemical impregnation. When porous carbon is instead formed using a chemical activation process, instead of creating pores by carbon removal, the activation mechanism works by widening existing pores or pushing apart (exfoliating) graphene sheets, which does not contribute to maintaining a high percentage of micropore space accessible through narrow channels / openings. This is believed to explain the relatively poor electrochemical performance of composites prepared from chemically activated porous carbon materials.

[0024] Thus, the porous carbon framework comprises a network of three-dimensionally interconnected open pores, including a combination of micropores and / or mesopores, and optionally a small amount of macropores. In accordance with IUPAC terminology, the term "micropore" is used herein to refer to pores less than 2 nm in diameter, the term "mesopore" is used herein to refer to pores between 2 and 50 nm in diameter, and the term "macropore" is used herein to refer to pores greater than 50 nm in diameter.

[0025] Any reference herein to the volume of micropores, mesopores, and / or macropores within a porous carbon framework, as well as to the distribution of pore volume within the porous carbon framework, refers to the internal pore volume of the porous carbon framework taken alone (i.e., in the absence of any silicon or other material occupying some or all of the pore volume).

[0026] The porous carbon framework is preferably derived from a plant source containing at least 28 wt% lignin, at least 30 wt% lignin, or at least 35 wt% lignin on a dry weight basis. As noted above, higher lignin content is believed to increase the tortuosity and contractibility of the pore volume and the proportion of "ink bottle shaped" pores.

[0027] The plant source is preferably a lignocellulosic material, i.e., a material containing both cellulose and / or hemicellulose. Preferably, the plant source contains at least 40 wt%, at least 45 wt%, at least 50 wt%, at least 55 wt%, at least 60 wt%, at least 65 wt%, or at least 70 wt% cellulose and / or hemicellulose on a dry weight basis.

[0028] More preferably, the plant source is a lignocellulosic material comprising at least 25 wt% lignin and at least 40 wt% cellulose and / or hemicellulose, at least 25 wt% lignin and at least 45 wt% cellulose and / or hemicellulose, at least 25 wt% lignin and at least 50 wt% cellulose and / or hemicellulose, at least 25 wt% lignin and at least 55 wt% cellulose and / or hemicellulose, at least 25 wt% lignin and at least 60 wt% cellulose and / or hemicellulose, at least 30 wt% lignin and at least 50 wt% cellulose and / or hemicellulose, at least 30 wt% lignin and at least 55 wt% cellulose and / or hemicellulose, or at least 30 wt% lignin and at least 60 wt% cellulose and / or hemicellulose.

[0029] A variety of different plant-based materials may be used to prepare the porous carbon framework. Examples of plant sources that can be used include the husks and shells of seeds, nuts, and fruits (including drupes, kernels, and pits). Examples of these plant sources include the husks and shells of coconuts (including coir), peanuts, walnuts, apricots, almonds, palm kernels, peaches, olives, and hazelnuts. Other plant sources with high lignin content include bamboo and bark (e.g., the bark of conifers including pine, spruce, larch, and poplar, and hardwoods including oak). A preferred plant source is coconut shell.

[0030] The plant source preferably has an elemental composition comprising at least 40 wt% carbon, at least 3 wt% hydrogen, and at least 30 wt% oxygen. Trace amounts of nitrogen, sulfur, and chlorine may also be present. More preferably, the plant source has an elemental composition comprising about 50 wt% carbon, 5 wt% hydrogen, and 40 wt% oxygen, with smaller amounts of nitrogen, sulfur, and chlorine present.

[0031] Porous carbon frameworks are obtained from plant sources in a two-step process. First, carbonaceous plant material is pyrolyzed by heating the plant material in an inert atmosphere. Pyrolysis is typically carried out at temperatures of about 400 to 900°C, about 500 to 700°C, or about 550 to 700°C, such that dehydration and devolatilization of carbon occurs. Preferably, the temperature does not exceed about 700°C. Optionally, the carbonaceous material is pretreated to remove impurities prior to heating. Optionally, the carbonaceous material is purified and / or washed and dried prior to heating. Optionally, the carbonaceous material is sieved, crushed, or milled to obtain uniformly sized particles prior to heating. Optionally, the carbonaceous material is pelletized prior to heating.

[0032] Second, the pyrolyzed material is activated by heating in a stream of steam or CO2 at temperatures between 600°C and 1200°C. This allows a chemical reaction between the carbon and the steam or CO2 to occur on the interior surface of the carbon, removing carbon from the pore walls and thereby increasing the pore volume. The steam or CO2 activation process allows the pore size to be easily modified, producing activated carbon with the desired porosity. Preferably, the pyrolyzed material is activated with steam.

[0033] Steam or CO activation can be suitably carried out in a rotary kiln, fixed bed reactor, or fluidized bed reactor. Optionally, activation can be followed by further flushing, washing, or purification steps. Optionally, the pyrolysis and activation steps can be combined into a continuous process. Optionally, the activated material can be powdered (e.g., milled) and / or sieved after the activation step to obtain particles of a desired size.

[0034] Burn-off of pyrolyzed material during activation is preferably at least 30%, or at least 40%. Burn-off is preferably no more than 80%, no more than 75%, or no more than 70%. Burn-off is the mass fraction of pyrolyzed material removed during the physical activation step as a percentage of the mass of material before physical activation begins.

[0035] Preferably, the D of the porous carbon framework 50 The particle size is 30 μm or less. Optionally, D 50 The particle size may be 25 μm or less, 20 μm or less, 18 μm or less, 16 μm or less, 14 μm or less, 12 μm or less, 10 μm or less, or 8 μm or less. 50 The particle size may be at least 0.5 μm, at least 1 μm, at least 1.5 μm, or at least 2 μm.

[0036] For example, the particles of the porous carbon framework may have a D in the range of 0.5 to 30 μm, 0.5 to 25 μm, 1 to 20 μm, 1 to 15 μm, 1 to 12 μm, 1 to 10 μm, or 1 to 8 μm. 50 It may have a particle size.

[0037] D of the porous carbon framework particles 10 The particle size is preferably at least 0.1 μm, at least 0.3 μm, or at least 0.5 μm. 90 The particle size is preferably 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less.

[0038] The particles of the porous carbon framework preferably have a narrow particle size distribution span. For example, the particle size distribution span (D 90- D 10 ) / D 50) is preferably not more than 5, more preferably not more than 4, more preferably not more than 3, more preferably not more than 2, and most preferably not more than 1.5. Preferably, the particle size distribution of the particles of the porous carbon framework has a positive skew.

[0039] By forming porous carbon framework particles with the particle size distribution presented herein, it is believed that the presence of large micron-sized pore voids / channels and the majority of macro-sized pores remaining after activation from the original cellular structure of the plant-source material are eliminated prior to chemical impregnation of the carbon framework with silicon. A narrow particle size distribution span with positive skewness and an average sphericity greater than 0.50 will also promote uniform deposition of silicon across the entire particle size range in the CVI reactor.

[0040] 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 particle volume is understood to include the volume of any intra-particle pores. 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 volume-based median particle size, 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 90th percentile volume-based median particle size, i.e., the diameter below which 90% by volume of the particle population lies.

[0041] Particle size and particle size distribution can be determined by conventional laser diffraction techniques according to ISO 13320:2009. Unless otherwise specified, particle size distribution measurements specified or reported herein were measured using a conventional Malvern Mastersizer™ 3000 particle size analyzer from Malvern Instruments. The Malvern Mastersizer™ 3000 particle size analyzer operates by projecting a helium-neon gas laser beam through a transparent cell containing particles of interest suspended in an aqueous solution. Light striking the particles is scattered through an angle inversely proportional to the particle size, and a photodetector array measures the light intensity at several predetermined angles. The measured intensities at different angles are processed by a computer using standard theoretical principles to determine the particle size distribution. The laser diffraction values ​​reported herein are obtained using a wet dispersion of particles in 2-propanol with 5 vol% of the surfactant SPAN™-40 (sorbitan monopalmitate). The refractive index of the particles is taken to be 2.68 for the porous carbon framework particles and 3.50 for the composite particles, with a dispersant index of 1.378. The particle size distribution is calculated using the Mie scattering model.

[0042] The particles of the porous carbon framework may have an average sphericity (as defined herein) of greater than 0.2, or greater than 0.3. Preferably, the particles of the porous carbon framework have an average sphericity of at least 0.4, at least 0.5, at least 0.55, at least 0.65, or at least 0.7.

[0043] It is possible to obtain very accurate two-dimensional projections of micron-scale particles by dynamic image analysis, in which a digital camera is used to record the shadow cast by the particle, or by scanning electron microscopy (SEM). As used herein, the term "sphericity" should be understood as the ratio of the area of ​​the particle projection (obtained from such image processing techniques) 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 is:

[0044]

number

[0045]

number

[0046] The porous carbon framework preferably has an elemental composition comprising at least 90 wt% carbon (measured using infrared absorption analysis of combustion products), preferably at least 95 wt% carbon, more preferably at least 97 wt% carbon, or at least 98 wt% carbon. Optionally, the porous carbon framework may contain small amounts of other elements, such as oxygen, nitrogen, sulfur, and hydrogen. The elemental composition of the porous carbon framework can be determined by conventional elemental analysis techniques described herein, performed in the absence of silicon. The carbon, hydrogen, and nitrogen contents are measured according to ISO 29541. Preferably, the porous carbon framework contains no more than 7 wt% oxygen, more preferably no more than 6 wt%, no more than 5 wt%, or no more than 3 wt% oxygen. Preferably, the carbon framework contains less than 0.1 wt% iron, more preferably no more than 0.05 wt% iron.

[0047] Preferably, the porous carbon framework has an ash content of 10 wt% or less, more preferably 5 wt% or less, 3 wt% or less, 1.5 wt% or less, 1 wt% or less, or 0.5 wt% or less, where ash content is the mass of the residue remaining after complete combustion of the porous carbon framework as a percentage of its initial mass, calculated according to ISO 1171.

[0048] It is believed that porous carbon frameworks containing high levels of oxygen or other contaminants degrade the performance of the composite product due to interactions with other elements during the manufacture of silicon-carbon composite particles and / or their use in cell electrodes. Ash content provides a measure of the amount of mineral oxides, such as silica and alumina, that remain after combustion of the carbon.

[0049] The total volume of micropores and mesopores (i.e., the total pore volume of pores with diameters in the range of 0 to 50 nm) is herein referred to as P 1 cm 3 / g, and P 1 represents a dimensionless number having a value between 0.5 and 1.5. For the avoidance of doubt, references herein to the pore volume of a porous carbon framework (unless stated to the contrary) relate to the pore volume of the porous carbon framework alone, i.e., as measured in the absence of any electroactive material (or any other material) occupying the pores of the porous carbon framework.

[0050] P 1 The value of P is preferably at least 0.55, at least 0.6, at least 0.65, at least 0.7, or at least 0.75. A more porous framework is advantageous because it allows a greater amount of silicon to be accommodated within the pore structure without compromising the resistance of the porous carbon framework to fracture under compressive stresses during electrode fabrication or expansion stresses due to silicon lithiation. However, P 1 If P is too high, it is not possible to achieve the high levels of surface silicon discussed below. 1 is 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1 or less, or 0.95 or less.

[0051] For example, P 1may be in the range of 0.55 to 1.4, 0.6 to 1.4, 0.6 to 1.3, 0.65 to 1.3, 0.65 to 1.2, 0.7 to 1.2, 0.7 to 1.1, 0.7 to 1, or 0.75 to 0.95.

[0052] As used herein, the volume fraction of micropores is P 1 The term "micropore volume fraction" refers to the volume of micropores expressed as a percentage of the total volume of micropores and mesopores, expressed as: (where ρ is the volume fraction of pores with a diameter of 2 nm or less relative to the total volume of pores with a diameter of up to 50 nm. The micropore volume fraction of the porous framework is preferably selected within the range of 0.43 to 0.85 (see below) in order to obtain a high level of surface silicon content in the composite particles.

[0053] Preferably, the volume fraction of micropores is at least 0.45, at least 0.48, at least 0.5, at least 0.51, at least 0.52, at least 0.54, at least 0.56, at least 0.58, or at least 0.6, based on the total volume of micropores and mesopores. Preferably, the volume fraction of micropores is no more than 0.8, no more than 0.79, no more than 0.78, no more than 0.76, no more than 0.74, no more than 0.72, or no more than 0.7, based on the total volume of micropores and mesopores.

[0054] The volume fraction of micropores may optionally be in the range of 0.45 to 0.85, 0.5 to 0.8, 0.45 to 0.78, 0.48 to 0.8, 0.48 to 0.78, 0.48 to 0.76, 0.5 to 0.8, 0.5 to 0.78, 0.5 to 0.76, 0.5 to 0.74, 0.5 to 0.72, 0.5 to 0.7, 0.51 to 0.76, 0.52 to 0.74, 0.53 to 0.74, 0.54 to 0.72, 0.6 to less than 0.8, 0.6 to 0.79, 0.6 to 0.78, 0.6 to 0.76, 0.6 to 0.74, 0.6 to 0.72, or 0.6 to 0.7, based on the total volume of micropores and mesopores.

[0055] The total volume of micropores and mesopores was determined using quenched solid-state density functional theory (QSDFT) at 77 K using 10 sq. m. according to the standard methodology presented in ISO 15901-2 and ISO 15901-3. -6 The porosity is determined using nitrogen gas adsorption up to a relative pressure of p / p0. Nitrogen gas adsorption is a technique that characterizes the porosity of a material by allowing a gas to condense in the pores of a solid. As the pressure increases, the gas condenses first in the smallest diameter pores, and the pressure is increased until a saturation point is reached where all of the pores are filled with liquid. The nitrogen gas pressure is then gradually reduced, allowing the liquid to evaporate from the system. Analysis of the adsorption and desorption isotherms, as well as the hysteresis between them, allows the pore volume and particle size distribution to be determined. Instruments suitable for measuring pore volume and particle 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 analyzers available from Quantachrome Instruments.

[0056] Given the limitations of available analytical techniques, it is not possible to measure pore volume across the entire range of micropores, mesopores, and macropores using a single technique. When a porous carbon framework contains macropores, the volume of pores in the range of greater than 50 nm to 100 nm is referred to herein as P. 2 cm 3 / g and is measured by mercury porosimetry. 2 The value of relates to the pore volume of the porous carbon framework when measured alone, i.e., in the absence of silicon or any other material occupying the pores of the porous carbon framework.

[0057] To avoid any misunderstanding, P 2The value of P takes into account only pores with diameters greater than 50 nm up to and including 100 nm, i.e., it includes only the volume of macropores up to 100 nm in diameter. Any pore volume measured by mercury porosimetry at particle sizes below 50 nm is also included in the P 2 (As noted above, nitrogen adsorption is used to characterize mesopores and micropores.) The pore volume measured by mercury porosimetry above 100 nm is assumed to be interparticle porosity for the purposes of this invention, and P 2 is not taken into account when determining the value of

[0058] Mercury porosimetry is a technique for characterizing the porosity 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 size of the pores. The values ​​obtained by mercury porosimetry reported herein were obtained according to ASTM UOP 578-11, and assume a surface tension γ of 480 mN / m and a contact angle φ of 140° for mercury at room temperature. The density of mercury is 13.5462 g / cm at room temperature. 3 Many high-precision mercury porosimetry instruments are commercially available, such as the AutoPore IV series of automated mercury porosimeters available from Micromeritics Instrument Corporation, USA. For a complete review of mercury porosimetry, reference may be made to [3].

[0059] The volume of the macropores (hence, P 2 The value of ) is preferably determined by the volume of the micropores and mesopores (hence, P 1 Although only a few macropores may be useful to facilitate electrolyte access to the pore network, the benefits of the present invention are substantially achieved by accommodating silicon in the micropores and smaller mesopores.

[0060] Therefore, according to the present invention, the total volume of macropores in the porous carbon framework is determined by P as measured by mercury porosimetry. 2 cm 3 / g, and P 2 is preferably 0.2 x P 1 Up to 0.1 x P 1 Up to 0.05 x P 1 Up to 0.02 x P 1 Up to 0.01 x P 1 Up to 0.005 x P 1 It has a value up to

[0061] It will be appreciated 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 outside the porous carbon framework. 1 and P 2 ) should be understood to refer to the volume of open pores, i.e., pores accessible to fluids from outside the porous carbon framework. Completely enclosed pores that cannot be identified by nitrogen adsorption or mercury porosimetry shall not be considered herein when specifying porosity. Similarly, any pore volume located in pores small enough to be below the detection limit by nitrogen adsorption shall not be considered in the P 1 is not taken into account when determining the value of

[0062] The porous carbon framework is preferably 1200 to 3000 m 2 / g. Preferably, the porous carbon framework has a BET surface area of ​​at least 1500 m 2 / g, or at least 1700m 2 / g. Preferably, the porous carbon framework has a BET surface area of ​​2500 m 2 / g or less, or 2000m 2 / g or less. As used herein, the term "BET surface area" should be understood 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 in accordance with ISO 9277.

[0063] The elemental composition of the composite particles can be determined by elemental analysis. Elemental analysis is used to determine the weight percentages of both silicon and carbon in the composite particles. Optionally, the amounts of hydrogen, nitrogen, and oxygen can also be determined by elemental analysis. Preferably, elemental analysis is also used to determine the weight percentage of carbon (and optionally hydrogen, nitrogen, and oxygen) in the porous carbon framework alone. Determining the weight percentage of carbon in the porous carbon framework alone takes into account the possibility that the porous carbon framework may have small amounts of heteroatoms within its molecular framework. Both measurements taken together allow for a reliable determination of the weight percentage of silicon relative to the entire porous carbon framework.

[0064] 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 of the composite particles and the carbon content of the porous carbon framework alone (and optionally the hydrogen, nitrogen, and oxygen contents) are preferably determined by combustion and infrared (IR) absorption techniques. A suitable instrument for determining the carbon, hydrogen, nitrogen, and oxygen contents is the TruSpec® Micro elemental analyzer available from LECO Corporation.

[0065] The particulate material of the present invention preferably contains 25 to 65 wt% silicon, more preferably 30 to 65 wt% silicon, as determined by elemental analysis. Preferably, the particulate material of the present invention contains at least 26 wt%, at least 28 wt%, at least 30 wt%, at least 32 wt%, at least 34 wt%, at least 36 wt%, at least 38 wt%, at least 40 wt%, at least 42 wt%, or at least 44 wt% silicon. Preferably, the particulate material of the present invention has no more than 60 wt%, no more than 58 wt%, no more than 56 wt%, no more than 54 wt%, no more than 52 wt%, or no more than 50 wt% silicon.

[0066] For example, the particulate material of the present invention may contain 26 to 65 wt%, 28 to 65 wt%, 30 to 65 wt%, 32 to 60 wt%, 34 to 60 wt%, 36 to 60 wt%, 38 to 58 wt%, 40 to 58 wt%, 42 to 56 wt%, or 44 to 54 wt% silicon.

[0067] A minimum amount of silicon is required to ensure that the particulate material has sufficient volumetric capacity for commercial use, but excessive amounts of silicon can deposit silicon in larger pores and / or on the surface of the porous carbon framework, resulting in lower surface silicon content and reduced performance as an electroactive material.

[0068] The amount of silicon in the composite particles of the present invention is selected so that at least about 20% and at most about 78% of the interior pore volume of the porous carbon framework (based on micropores and mesopores) is occupied by silicon (in an uncharged state). Generally, the higher the proportion of micropores in the porous carbon framework, the greater the amount of silicon that can be used without reducing the proportion of surface silicon.

[0069] Preferably, silicon occupies about 20% to about 78% of the internal pore volume of the porous carbon framework, e.g., about 23% to 75%, about 26% to 72%, about 28% to 70%, about 30% to 70%, about 35% to 68%, about 40% to 65%, or about 45% to 60% of the internal pore volume of the porous carbon framework. Within these preferred ranges, the pore volume of the porous carbon framework is effective to accommodate the expansion of silicon during charging and discharging, while avoiding excess pore volume that does not contribute to the volumetric capacity of the particulate material. However, the amount of silicon is not so great as to prevent effective lithiation due to insufficient metal ion diffusion rates or insufficient expansion volume to provide mechanical resistance to lithiation.

[0070] The amount of silicon in the porous carbon framework is determined by the weight ratio of silicon to porous carbon framework [0.50 × P 1 This can be correlated to the available pore volume by the requirement that the silicon weight ratio be in the range [0.7×P to 1.9×P]:1. This relationship defines the silicon weight ratio at which the pore volume is estimated to be about 20% to 78% occupied, taking into account the density of silicon and the pore volume of the porous carbon framework. Preferably, the silicon to porous carbon framework weight ratio is in the range [0.7×P]:1. 1 From 1.8 x P 1 ]:1, which indicates that the pore volume is approximately 30% to 78% occupied.

[0071] Preferably, the weight ratio of silicon to porous carbon framework is at least 0.50×P 1 , at least 0.55 × P 1 , at least 0.6 × P 1 , at least 0.65 × P 1 , 0.7×P 1 , at least 0.75 × P 1 , at least 0.8 × P 1 , at least 0.85 × P 1 , at least 0.9 × P 1 , at least 0.95 × P 1 , or at least 1×P 1Preferably, the weight ratio of silicon to porous carbon framework is 1.85×P 1 Below, 1.8 x P 1 Below, 1.75 x P 1 Below, 1.7 x P 1 Below, 1.65 x P 1 Below, 1.6 x P 1 Below, 1.55 x P 1 or less, or 1.5 x P 1 The following is the result.

[0072] The composite particles preferably have a low total oxygen content, as determined by elemental analysis. Oxygen may be present within the composite particles, for example, as part of the porous carbon framework or as an oxide layer on any exposed silicon surfaces. Preferably, the total oxygen content of the composite particles is less than 15 wt%, more preferably less than 12 wt%, more preferably less than 10 wt%, more preferably less than 5 wt%, e.g., less than 4 wt%, less than 3 wt%, less than 2 wt%, less than 1 wt%, or less than 0.5 wt%. Preferably, silicon and carbon together constitute at least 90 wt% of the composite particles, more preferably at least 95 wt% of the composite particles.

[0073] The silicon may optionally contain small amounts of one or more dopants. Suitable dopants include boron and phosphorus, other n-type or p-type dopants, nitrogen, or germanium. Preferably, the dopants are present in a total amount of 2 wt% or less, based on the total amount of silicon and the one or more dopants.

[0074] Atoms at the surface of a material have a different set of bonding interactions relative to atoms in the bulk of the material, and this difference is usually described in terms of the surface energy of the material. In the case of silicon deposited by chemical vapor impregnation (CVI), the free valences of silicon atoms at the surface typically carry hydride groups. If this hydride-terminated silicon surface is accessible to air, it reacts with oxygen to form a native oxide surface. However, surfaces that are not accessible to air remain in the hydride-terminated form. The amount of this surface silicon can be quantified using thermogravimetric analysis (TGA). Silicon atoms at the surface of silicon nanostructures oxidize at lower temperatures than silicon atoms in the bulk of the silicon nanostructure (see Non-Patent Document 4). TGA analysis allows the relative content of surface silicon to be quantified based on the weight gain observed when silicon is oxidized to silicon dioxide (SiO2) in air and at high temperatures. By plotting the weight gain versus temperature, it is possible to distinguish and quantify bulk and surface silicon in a sample. [Brief explanation of the drawings]

[0075] [Figure 1] FIG. 1 shows a TGA trace for a particulate material according to the present invention containing high levels of surface silicon and low levels of bulk rough silicon. [Figure 2] FIG. 1 shows a TGA trace for a particulate material containing low levels of surface silicon and high levels of bulk rough silicon. [Figure 3] FIG. 1 is a diagram showing the relationship between surface silicon and silicon content. DETAILED DESCRIPTION OF THE INVENTION

[0076] A determination of the amount of unoxidized surface silicon is obtained from characteristic TGA traces for these materials, as shown in Figures 1 and 2. Following an initial mass loss up to approximately 300 °C (shown in Figures 1 and 2 as a mass decrease from (a) to (b)), a significant mass increase is observed beginning at approximately 400 °C and peaking between 550 and 650 °C (shown in Figures 1 and 2 as a mass increase from (b) to (c)). Next, a mass decrease (mass decrease from (c)) is observed as the porous carbon framework oxidizes to CO gas. Then, above approximately 800 °C, a mass increase is observed again, corresponding to the continued conversion of silicon to SiO, and increases toward an asymptotic value above 1000 °C (mass increase from (d) to (e)) as the silicon oxidation progresses toward completion. The temperature at which weight gain occurs is related to the structure of the silicon: surface silicon oxidizes at lower temperatures, while bulk silicon oxidizes at higher temperatures. Thus, the coarser the silicon domains, the more oxidation is observed at higher temperatures.

[0077] Any native oxide already formed on the air-exposed silicon surface does not affect the TGA analysis because the already oxidized silicon does not result in a mass increase in the TGA analysis. Thus, the more silicon surface is able to react with air to form native oxide, the less surface silicon will be observed by TGA. Therefore, to avoid any doubt, the calculation of "surface silicon" only considers silicon that is not oxidized at the start of the TGA analysis after the material has been passivated with air or another surface passivating agent described herein (i.e., the particulate material is not maintained under any special inert conditions prior to the TGA analysis).

[0078] 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, with the TGA performed in air at a temperature ramp 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 percentage of the total silicon in the sample, and M max is the maximum mass of the sample measured in the temperature range from 550 to 650 °C (mass (c) in Figures 1 and 2), and M min is the minimum mass of the sample at temperatures above 150°C and below 500°C (mass (b) in Figures 1 and 2), and M f is the mass of the sample at the completion of oxidation at 1400°C (mass (e) in Figures 1 and 2). For completeness, it will be understood that 1.875 is the molar mass ratio of SiO to O (i.e., the mass ratio of SiO formed to the mass increase due to the addition of oxygen). Typically, TGA analysis is performed using a sample size of 10 mg ± 2 mg.

[0079] It has been found that reversible capacity retention over multiple charge-discharge cycles is significantly improved when the surface silicon, as determined by the TGA method described above, is at least 20 wt% of the total amount of silicon in the material, preferably at least 22 wt%, at least 25 wt%, at least 30 wt%, at least 35 wt% of the silicon, at least 40 wt% of the silicon, or at least 45 wt% of the silicon is surface silicon as determined by thermogravimetric analysis (TGA).

[0080] Optionally, the amount of surface silicon as determined by TGA is up to 80 wt%, up to 75 wt%, up to 70 wt%, up to 65 wt%, up to 60 wt%, or up to 55 wt% of the total amount of silicon in the particulate material. For example, the amount of surface silicon as determined by TGA may be 20 to 80 wt%, 22 to 75 wt%, 25 to 70 wt%, 30 to 65 wt%, 35 to 60 wt%, or 40 to 55 wt% of the total amount of silicon in the particulate material. The amount of surface silicon as determined by TGA may also be within the range of 20 to 55 wt%, 22 to 60 wt%, 25 to 65 wt%, 30 to 70 wt%, 35 to 75 wt%, or 40 to 80 wt% of the total amount of silicon in the particulate material. Further preferred ranges can be defined by combining the upper and lower limits of any of the above ranges.

[0081] The fact that a significant fraction of hydride-terminated surface silicon is measurable in the particulate material even after passivation in air indicates that the composite particles have interior silicon surfaces that are not accessible to air. This indicates that the interior pore space of the porous carbon framework is first attached with silicon and then capped to form interior void spaces, and that the hydride-terminated silicon surfaces are oriented toward the closed interior void spaces. This, in turn, indicates that the silicon domains have characteristic length scales that are much smaller than the pores themselves.

[0082] Because the internal voids are inaccessible to the electrolyte, the silicon surface is protected from SEI formation, thereby minimizing irreversible lithium loss during the first charge cycle. Further exposure of the electroactive material during subsequent charge-discharge cycles is also substantially prevented, making SEI formation a non-critical failure mechanism leading to capacity loss. At the same time, the silicon is hydrostatically confined during lithiation, allowing for utilization of the voids during lithiation-induced expansion.

[0083] In addition to the surface silicon content, the particulate material of the present invention preferably has 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 temperature ramp rate of 10°C / min. This is shown in Figures 1 and 2 as the mass increase from (d) to (e). The coarse bulk silicon content is therefore given by the following formula: Z = 1.875 × [(M f -M 800 ) / M f ]×100% where Z is the percentage of unoxidized silicon at 800°C and M 800 is the mass of the sample at 800 °C (mass (d) in Figures 1 and 2), and M f is the mass of ash at the completion of oxidation at 1400°C (mass (e) in Figures 1 and 2). For the purposes of this analysis, any mass increase above 800°C corresponds to the oxidation of silicon to SiO2, and the total mass at the completion of oxidation is assumed to be SiO2.

[0084] Preferably, no more than 10 wt% of the silicon, no more than 8 wt% of the silicon, no more than 6 wt% of the silicon, no more than 5 wt%, no more than 4 wt%, no more than 3 wt%, no more than 2 wt%, or no more than 1.5 wt% of the silicon is coarse bulk silicon as determined by TGA.

[0085] Preferably, at least 30 wt% of the silicon (e.g., 30 to 75 wt%, 30 to 70 wt%, or 30 to 65 wt% of the silicon, etc.) is surface silicon and not more than 10 wt% of the silicon is rough bulk silicon, both determined by TGA. More preferably, at least 35 wt% of the silicon (e.g., 35 to 70 wt%, 35 to 65 wt%, or 35 to 60 wt% of the silicon, etc.) is surface silicon and not more than 8 wt% of the silicon is rough bulk silicon, both determined by TGA. More preferably, at least 40 wt% of the silicon (e.g., 40 to 65 wt%, 40 to 60 wt%, or 40 to 55 wt% of the silicon, etc.) is surface silicon and not more than 5 wt% of the silicon is rough bulk silicon, both determined by TGA. More preferably, at least 45 wt% of the silicon is surface silicon (e.g., 45 to 65 wt%, 45 to 60 wt%, or 45 to 55 wt%, etc.) and no more than 2 wt% of the silicon is rough bulk silicon, both as determined by TGA.

[0086] Preferably, the total volume of micropores and mesopores in the composite particles (i.e., in the presence of silicon) as measured by nitrogen gas adsorption is less than 0.15×P 1 Up to 0.10 x P 1 Up to 0.05 x P 1 Up to 0.02 x P 1 That's it.

[0087] Preferably, the total volume of micropores and mesopores in the composite particles as measured by nitrogen gas adsorption is less than 0.2 cm 3 / g, preferably less than 0.15 cm 3 / g or less, 0.1cm 3 / g or less, 0.08cm 3 / g or less, 0.06cm 3 / g or less, 0.04cm 3 / g or less, 0.02cm 3 / g or less, 0.015cm 3 / g or less, 0.012cm 3 / g or less, 0.010cm 3 / g or less than 0.008cm 3 / g.

[0088] The composite particles have a D in the range of 1 to 30 μm. 50 Optionally, D 50 The particle size may be at least 1 μm, at least 2 μm, at least 3 μm, at least 4 μm, or at least 5 μm. 50 The particle size may be 20 μm or less, 18 μm or less, 16 μm or less, 14 μm or less, 12 μm or less, 10 μm or less, or 8 μm or less.

[0089] For example, the composite particles may have a D in the range of 1 to 20 μm, 1 to 18 μm, 1 to 16 μm, 2 to 16 μm, 2 to 14 μm, 2 to 12 μm, 2 to 10 μm, or 2 to 8 μm. 50 Within these size ranges, particles with the porosity and particle size distribution presented herein are ideally suited for use in anodes for metal-ion batteries due to their dispersibility in slurries, structural robustness, capacity retention over repeated charge-discharge cycles, and suitability for forming dense electrode layers of uniform thickness within the conventional range of 20 to 50 μm.

[0090] D of composite particles 10 The particle size is preferably at least 0.5 μm, at least 0.8 μm, or at least 1 μm. 10 Maintaining particle size above 0.5 μm reduces the likelihood of undesired agglomeration of submicron-sized particles, resulting in improved dispersibility of the particulate material and improved volume retention.

[0091] D of composite particles 90 The particle size is preferably 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less. The presence of very large particles leads to uneven particle packing in the electrode active layer, thus hindering the formation of a dense electrode layer, especially an electrode layer having a thickness in the range of 20 to 50 μm. Therefore, D90 Preferably the particle size is up to 40 μm, more preferably even lower.

[0092] The composite 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 high-density electrode layer can be more easily achieved.

[0093] The composite particles preferably have a positive skewness in the volume-based distribution, e.g., the volume-based distribution is asymmetric with a long right tail. A positive skewness in the volume-based particle size distribution is advantageous because it provides a denser electrode due to a higher natural packing than if all the particles were the same size, thereby reducing the need for calendering or other physical densification processes. Preferably, D 50 The composite particle size diameter is smaller than the volume-based mean of the particle size diameter distribution (D[4.3]). Preferably, the skewness of the composite particle size distribution (as measured by a Malvern Mastersizer™ 3000 analyzer) is 5 or less, or 3 or less.

[0094] The composite particles of the present invention are preferably 200 ml 2 / g or less. Preferably, the BET surface area of ​​the composite particles is 150 m 2 / g or less, 100m 2 / g or less, 80m 2 / g or less, 60m 2 / g or less, 50m 2 / g or less, 40m 2 / g or less, 30m 2 / g or less, 25m 2 / g or less, 20m 2 / g or less, 15m 2 / g or less, or 10m 2 / g or less.

[0095] 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 cycle of an anode comprising the particulate material of the present invention. However, an excessively small BET surface area results in unacceptably low charge rates and capacity limitations due to the inaccessibility of metal ions in the surrounding electrolyte to the bulk of the electroactive material. For example, the BET surface area is preferably at least 0.1 m 2 / g, at least 1m 2 / g, at least 2m 2 / g, or at least 5m 2 / g. For example, the BET surface area is 2 / g to 25m 2 / g, more preferably in the range of 2 to 15m 2 / g.

[0096] The particulate material of the present invention typically has a specific charge capacity at first lithiation of 900 to 2300 mAh / g. Preferably, the particulate material of the present invention has a specific charge capacity at first lithiation of at least 1200 mAh / g or at least 1400 mAh / g.

[0097] The particulate material of the present invention may optionally include a silicon surface that has been treated with a passivating agent. As discussed in more detail below, a passivating agent is defined herein as a compound that can modify the surface of an electroactive material in such a way as to inhibit or prevent the formation of surface oxides.

[0098] The composite particles of the present invention may optionally include a coating that at least partially or completely covers the outer surface of the particle. The coating is preferably a lithium-ion permeable coating. As used herein, the term "lithium-ion permeable" refers to an ion-conducting material that allows the transport of lithium ions from the exterior of the composite particle to the nanoscale electroactive material domains. Preferably, the lithium-ion permeable coating is impermeable to liquids, such as the solvent of a liquid electrolyte. Preferably, the lithium-ion permeable filler material is electrochemically stable at <0.1 V vs. Li / Li+.

[0099] Optionally, the coating may comprise a conductive carbon coating. Suitably, the conductive carbon coating may be obtained by chemical vapor deposition (CVD). CVD is a methodology well known in the art and involves the thermal decomposition of a volatile carbon-containing gas (e.g., ethylene) onto the surface of the particulate material. Alternatively, the carbon coating may be formed by depositing a solution of a carbon-containing compound onto the surface of the particulate material, followed by thermal decomposition. The conductive carbon coating is sufficiently permeable to allow lithium to reach the interior of the composite particle without excessive resistance, so as not to degrade the rate performance of the composite particle. For example, the thickness of the carbon coating may be in the range of 2 to 30 nm. Optionally, the carbon coating may be porous and / or only partially cover the surface of the composite particle.

[0100] Alternatively, the coating may comprise a lithium ion permeable solid electrolyte. Examples of suitable lithium permeable solid electrolytes include: garnet-type solid electrolytes (LiLaZrO 12 and Li 6.5 La3Ti 0.5 Zr 1.5 O 12 "LLZO" electrolytes such as; perovskite-type solid electrolytes (Li 0.33 La 0.57 including "LLTO" electrolytes such as TiO3); LISICON-type solid electrolytes, NaSICON-type solid electrolytes (Li 1.3Al 0.3 Ti 1.7 (PO4)3, etc.); lithium phosphate oxynitride (LiPON) solid electrolyte; Li3N type solid electrolyte; lithium phosphate (Li3PO4) solid electrolyte, lithium titanate (Li4Ti5O 12 ) solid electrolytes; lithium tantalate (LiTaO) solid electrolytes; sulfide-type solid electrolytes; argyrodite-type solid electrolytes; and antiperovskite-type solid electrolytes. Variations (e.g., containing dopants) and combinations of these electrolyte types are also included.

[0101] The coating has the advantage of further reducing the BET surface area of ​​the particulate material by smoothing any surface defects and filling any remaining surface micropores, thereby further reducing first cycle loss. The use of a conductive coating, such as a carbon coating, is particularly advantageous because it improves the conductivity of the surface of the composite particle, improves the rate performance of the particulate material when used as an electroactive material in a lithium-ion battery, and / or reduces the need for conductive additives in the electrode composition, and also creates an improved surface for the formation of a stable SEI layer, resulting in improved capacity retention during cycling. When the composite particle includes a coating, the silicon content (wt%) of the particle is determined based on the weight of the particle including the coating.

[0102] The composite particles of the present invention are suitably prepared via chemical vapor infiltration (CVI) of a silicon-containing precursor into the pore structure of a porous carbon framework. As used herein, CVI refers to a process in which a gaseous silicon-containing precursor is thermally decomposed at a surface to form elemental silicon and gaseous by-products at the surface.

[0103] According to a second aspect of the present invention, there is provided a particulate material comprising a plurality of composite particles, the composite particles comprising: (a) a porous carbon framework comprising micropores and / or mesopores, the micropores and mesopores being 1 cm 3 / g of total pore volume measured by gas adsorption, P 1 represents a number having a value between 0.5 and 1.5, porous carbon framework; (b) multiple elemental nanoscale silicon domains located within the micropores and / or mesopores of the porous carbon framework; wherein the porous carbon framework is an activated carbon material obtained by pyrolysis of coconut shells followed by activation with water vapor or carbon dioxide, preferably with water vapor.

[0104] The particulate material of the second aspect of the invention may have any of the features described as preferred or optional in relation to the first aspect of the invention.

[0105] In a third aspect of the present invention, there is provided a composition comprising a particulate material according to the first or second aspect of the present invention and at least one other component. In particular, there is provided a composition comprising a particulate material according to the first aspect of the present invention and at least one other component selected from (i) a binder; (ii) a conductive additive; and (iii) a further particulate electroactive material. The composition according to the third aspect of the present invention is useful as an electrode composition and can therefore be used to form the active layer of an electrode.

[0106] The particulate material used to prepare the composition of the third aspect of the invention may have any of the features described as preferred or optional in relation to the first and second aspects of the invention.

[0107] The composition may be a hybrid electrode composition comprising a particulate material according to the first aspect of the present invention and at least one further particulate electroactive material. Examples of the further particulate electroactive material include graphite, hard carbon, silicon, tin, germanium, aluminum, and lead. The at least one further particulate electroactive material is preferably selected from graphite and hard carbon, and most preferably the at least one further particulate electroactive material is graphite.

[0108] In the case of a hybrid electrode composition, the composition preferably comprises from 3 to 60 wt%, 3 to 50 wt%, 5 to 50 wt%, 10 to 50 wt%, or 15 to 50 wt% of particulate material according to the first aspect of the invention, based on the total dry weight of the composition.

[0109] The at least one further particulate electroactive material is suitably present in an amount of from 20 to 95 wt%, from 25 to 90 wt%, or from 30 to 750 wt% of the at least one further particulate electroactive material.

[0110] The at least one further particulate electroactive material has a D in the range of 10 to 50 μm, preferably 10 to 40 μm, more preferably 10 to 30 μm, most preferably 10 to 25 μm, for example 15 to 25 μm. 50 It is preferred that the particle size is large.

[0111] D of at least one further particulate electroactive material 10 The particle size is preferably at least 5 μm, more preferably at least 6 μm, more preferably at least 7 μm, more preferably at least 8 μm, more preferably at least 9 μm, even more preferably at least 10 μm.

[0112] D of at least one further 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.

[0113] The at least one further particulate electroactive material is preferably selected from carbon-containing particles, graphite particles, and / or hard carbon particles, the graphite particles and hard carbon particles having a D in the range of 10 to 50 μm. 50 Even more preferably, the at least one further particulate electroactive material is selected from graphite particles, the graphite particles having a D in the range of 10 to 50 μm. 50It has a particle size.

[0114] The composition may also be a non-hybrid (or "highly loaded") electrode composition that is substantially free of additional particulate electroactive materials. In this context, the term "substantially free of additional particulate electroactive materials" 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 of the battery), based on the total dry weight of the composition.

[0115] "Highly loaded" electrode compositions of this type preferably comprise at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, or at least 90 wt% of particulate material according to the first aspect of the invention, based on the total dry weight of the composition.

[0116] The composition may optionally contain a binder. The binder functions to adhere the composition to the current collector and maintain the integrity of the composition. Examples of binders that can be used in accordance with 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), its alginate salts and alkali metal salts, styrene-butadiene rubber (SBR), and polyimide. The composition may also contain a mixture of binders. Preferably, the binder comprises a polymer selected from polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0117] The binder may suitably be present in an amount of from 0.5 to 20 wt%, preferably from 1 to 15 wt%, preferably from 2 to 10 wt%, most preferably from 5 to 10 wt%, based on the total dry weight of the composition.

[0118] 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.

[0119] The composition may optionally contain 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 can be selected from carbon black, carbon fiber, carbon nanotubes, graphene, acetylene black, ketjen black, metal fibers, metal powders, and conductive metal oxides. Preferred conductive additives include carbon black and carbon nanotubes.

[0120] The one or more conductive additives may suitably be present in a total amount of from 0.5 to 20 wt%, preferably from 1 to 15 wt%, preferably from 2 to 10 wt%, most preferably from 5 to 10 wt%, based on the total dry weight of the composition.

[0121] In a fourth aspect, the present invention provides an electrode comprising a particulate material as defined with reference to the first or second aspect of the invention in electrical contact with a current collector. The particulate material used to prepare the electrode of the fourth aspect of the invention may have any of the features described as preferred or optional in relation to the first and second aspects of the invention.

[0122] As used herein, the term current collector refers to any conductive substrate capable of carrying current between 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. The current collector is typically in the form of a foil or mesh having a thickness of 3 to 500 μm. The particulate material of the present invention can be applied to one or both surfaces of the current collector to a thickness preferably ranging from 10 μm to 1 mm, for example, from 20 to 500 μm, or from 50 to 200 μm.

[0123] Preferably, the electrode comprises a composition as defined with reference to the third aspect of the invention in electrical contact with a current collector, which composition may have any of the features described as preferred or optional in relation to the third aspect of the invention.

[0124] The electrode of the fourth aspect of the present invention can be made by combining the particulate material of the present invention (optionally in the form of a composition of the present invention) with a solvent and, optionally, one or more viscosity-modifying additives to form a slurry. The slurry is then cast onto the surface of a current collector and the solvent is removed, thereby forming an electrode layer on the surface of the current collector. Further steps, such as heat treatment to cure any binder and / or calendaring the electrode layer, can be performed as needed. The electrode layer suitably has a thickness within the range of 20 μm to 2 mm, preferably 20 μm to 1 mm, preferably 20 μm to 500 μm, preferably 20 μm to 200 μm, preferably 20 μm to 100 μm, and preferably 20 μm to 50 μm.

[0125] 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 is in the form of a coherent, free-standing mass, which can then be bonded to a current collector by known methods.

[0126] The electrode of the fourth aspect of the invention can be used as an anode in a metal-ion battery. Accordingly, in a fifth aspect, the invention provides a rechargeable metal-ion battery comprising an anode comprising the electrode 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.

[0127] 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.

[0128] 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、 LiMnO2, LiCo 0.5 Ni 0.5 O2, LiCo 0.7 Ni 0.3 O2, LiCo 0.8 Ni 0.2 O2, LiCo 0.82 Ni 0.18 O2, LiCo 0.8 Ni 0.15 Al 0.05 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2 and LiNi 0.33 Co 0.33 Mn 0.34 O2. The cathode current collector is generally 3 to 500 μm thick. Examples of materials that can be used as the cathode current collector include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0129] The electrolyte is suitably 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 solution, a solid electrolyte, and an inorganic solid electrolyte. Examples of usable non-aqueous electrolyte solutions include aprotic organic solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, sulfolane, methyl sulfolane, and 1,3-dimethyl-2-imidazolidinone.

[0130] Examples of organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyester sulfides, polyvinyl alcohol, polyvinylidine fluoride, and polymers containing ion-dissociating groups.

[0131] An example of an inorganic solid electrolyte is Li5NI 2、 Li3N, LiI, LiSiO4, Li2SiS 3、 These include nitrides, halides, and sulfides of lithium salts such as Li4SiO4, LiOH, and Li3PO4.

[0132] The lithium salt is suitably soluble in the selected solvent or mixture of solvents. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO, LiBF, LiBCO, LiPF, LiCFSO, LiAsF, LiSbF, LiAlCl, CHSOLi, and CFSOLi.

[0133] When the electrolyte is a non-aqueous organic solution, the metal-ion battery is preferably provided with a separator interposed between the anode and the cathode. The separator is typically formed of an insulating material with high ion permeability and high mechanical strength. The separator typically has a particle size of 0.01 to 100 μm and a thickness of 5 to 300 μm. An example of a suitable electrode separator is a microporous polyethylene film.

[0134] The separator may be replaced by 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.

[0135] According to a sixth aspect of the present invention there is provided a process for preparing a particulate material according to the first aspect of the present invention, the process comprising: (a) providing a plurality of porous carbon particles comprising micropores and / or mesopores; (i) the porous carbon particles are activated carbon material obtained by pyrolysis of a plant source containing at least 25 wt. % lignin on a dry weight basis, followed by activation with water vapor or carbon dioxide; and (ii) Micropores and mesopores are P 1 cm 3 / g of total pore volume measured by gas adsorption, P 1 represents a number with a value between 0.5 and 1.5: Steps and (b) contacting the plurality of porous carbon particles with a gas comprising 0.5 to 20 vol% silicon precursor gas at a temperature of 400 to 700°C to deposit silicon within the pores of the porous carbon particles; Includes.

[0136] According to a seventh aspect of the present invention, there is provided a process for preparing a particulate material according to the first aspect of the present invention, the process comprising: (a) providing a plurality of porous carbon particles comprising micropores and / or mesopores; (i) the porous carbon particles are activated carbon material obtained by pyrolysis of a plant source containing at least 25 wt. % lignin on a dry weight basis, followed by activation with water vapor or carbon dioxide; and (ii) Micropores and mesopores are P 1 cm 3 / g of total pore volume measured by gas adsorption, P 1 represents a number having a value between 0.5 and 1.5; Steps and (b) contacting the plurality of porous carbon particles with a silicon precursor gas having a partial pressure of 0.5 to 20 kPa at a temperature of 400 to 700°C to deposit silicon within the pores of the porous carbon particles; Includes.

[0137] The particulate materials prepared according to the sixth and seventh aspects of the invention may have any of the features described above as preferred or optional in relation to the first aspect of the invention. In particular, the porous carbon particles may have any of the features of the porous carbon framework described in relation to the first aspect of the invention. In particular, the porous carbon particles are preferably activated by water vapor.

[0138] According to an eighth aspect of the present invention, there is provided a process for preparing a particulate material according to the second aspect of the present invention, the process comprising: (a) providing a plurality of porous carbon particles comprising micropores and / or mesopores; (i) the porous carbon particles are activated carbon materials obtained by pyrolysis of coconut shells followed by activation with water vapor or carbon dioxide; and (ii) Micropores and mesopores are P 1 cm 3 / g of total pore volume measured by gas adsorption, P 1 represents a number having a value between 0.5 and 1.5; Steps and (b) contacting the plurality of porous carbon particles with a gas comprising 0.5 to 20 vol% silicon precursor gas at a temperature of 400 to 700°C to deposit silicon within the pores of the porous carbon particles; Includes.

[0139] The particulate material prepared according to the eighth aspect of the invention may have any of the features described above as preferred or optional in relation to the second aspect of the invention. The porous carbon particles may have any of the features of the porous carbon framework described in relation to the first aspect of the invention. In particular, the porous carbon particles are preferably activated by water vapor.

[0140] The following preferred features apply to all of the sixth, seventh and eighth aspects unless otherwise indicated.

[0141] Suitable gaseous silicon-containing precursors for use in the sixth through eighth aspects of the present invention include silane (SiH), silane derivatives (e.g., disilane, trisilane, and tetrasilane), and trichlorosilane (SiHCl).

[0142] Optionally, the silicon-containing precursor is chlorine-free, meaning that the silicon-containing precursor contains less than 1 wt%, preferably less than 0.1 wt%, preferably less than 0.01 wt% of chlorine-containing compounds.

[0143] The silicon-containing precursor may be used in pure form or, more usually, as a diluted mixture with an inert carrier gas such as nitrogen or argon.

[0144] Step (b) is suitably carried out at a low partial pressure of silicon precursor, with the remaining partial pressure being below 101.3 kPa (i.e., 1 atmosphere) total pressure, using an inert padding gas such as hydrogen, nitrogen, or argon.

[0145] According to the sixth and eighth aspects of the present invention, the silicon-containing precursor is used in an amount in the range of 0.5 to 20 vol%, for example 1 to 10 vol%, or 1 to 5 vol%, preferably at least 3 vol%, based on the total volume of the silicon-containing precursor and the inert carrier gas.

[0146] According to a seventh aspect of the present invention, the partial pressure of the silicon-containing precursor is 0.5 to 20 kPa, 1 to 15 kPa, 1 to 10 kPa, or 1 to 5 kPa. As used herein, the partial pressure of the silicon precursor gas is defined as the total pressure multiplied by the volume fraction of the silicon precursor gas (i.e., ideal gas behavior is assumed). When the silicon precursor gas is used directly, the partial pressure of the silicon precursor gas is equal to the total pressure. Alternatively, the total pressure may be the sum of the partial pressure of the silicon precursor gas and an inert padding gas such as nitrogen or argon.

[0147] A temperature ranging from 400 to 700°C, preferably 425 to 550°C, or 425 to 500°C, is used in step (b). Optionally, the porous carbon particles are contacted with the silicon precursor gas at an initial temperature below 400°C, and then the reaction temperature is increased to the range of 400 to 700°C.

[0148] Step (b) is preferably carried out optionally with agitation or fluidization of the porous carbon particles, which is particularly preferred when the process is carried out on a large scale. Suitable reactor types include rotary kilns or fluidized bed reactors (including spouted bed reactors).

[0149] To obtain the particulate materials of the present invention with high surface silicon content, the CVI process must be carefully controlled to ensure that the silicon deposition rate is low relative to the diffusion rate of the silicon precursor gas into the pore structure of the porous carbon framework. Operating in the preferred temperature range of 425-500°C and using low concentrations of silicon precursor gas also control the silicon deposition rate, ensuring that the silicon deposition rate is low relative to the silicon precursor impregnation rate. Conditions within the CVI reactor should also be as uniform as possible. Agitation or fluidization of the porous carbon particles ensures that the silicon precursor gas can uniformly impregnate the particles and also ensures that the temperature within the reactor is uniform throughout the particle bed.

[0150] Preferably, step (b) is carried out at a pressure below atmospheric pressure. For example, step (b) can be carried out at an absolute pressure of less than 100 kPa, less than 90 kPa, less than 80 kPa, less than 70 kPa, or less than 60 kPa. Preferably, step (b) is carried out at an absolute pressure of at least 5 kPa, at least 10 kPa, at least 15 kPa, at least 20 kPa, at least 25 kPa, or at least 30 kPa. For example, step (b) is preferably carried out at an absolute pressure in the range of 10 to 90 kPa, 20 to 80 kPa, 20 to 70 kPa, or 30 to 60 kPa.

[0151] It has been found that carrying out step (b) at an absolute pressure below atmospheric pressure significantly improves the surface silicon content of the particulate material product.

[0152] Preferred operating conditions for step (b) to form a particulate material product containing greater than 20% surface silicon include the use of a gas containing 0.5 to 20 vol% silicon precursor gas (preferably silane) at an absolute pressure of 10 to 90 kPa. More preferably, a gas containing 2 to 15 vol% silicon precursor is used at an absolute pressure of 20 to 80 kPa. More preferably, a gas containing 5 to 10 vol% silicon precursor is used at an absolute pressure of 30 to 60 kPa. With reference to the accompanying examples, operation within these preferred conditions reliably provides particulate materials with very high surface silicon content, at least 30% or at least 40%. Careful selection of porous carbon particles, along with the use of controlled CVI conditions described herein, allows for the production of particulate materials with very high surface silicon content and low coarse bulk silicon content, indicating that a high proportion of silicon is present in the form of ultrafine silicon nanostructures. Such materials have not previously been reported in the art.

[0153] The surface of electroactive materials deposited by CVI is reactive to oxygen and forms a native oxide layer when exposed to atmospheric oxygen. In the case of silicon, an amorphous silicon dioxide film forms immediately upon exposure of the silicon surface to oxygen, and in certain circumstances, oxidation can continue with prolonged exposure during storage. The formation of the native oxide layer is exothermic and therefore requires careful process control to prevent overheating or even combustion of the particulate material during manufacturing or storage. The presence of the native oxide layer can be detrimental to the performance of electroactive materials in lithium-ion batteries, as it is associated with irreversible capacity loss and reduced cycle life. Therefore, the process of the present invention may optionally include a further step (c) of contacting the exposed surface of the deposited silicon with a passivating agent, where the silicon has not been exposed to oxygen prior to contact with the passivating agent.

[0154] A passivator is defined herein as a compound capable of modifying the surface of an electroactive material in such a way as to inhibit or prevent the formation of surface oxides.

[0155] Suitable passivating agents include compounds containing an alkene, alkyne, or carbonyl functional group, more preferably a terminal alkene, terminal alkyne, or aldehyde group.

[0156] Preferred passivators have the following formula: (i) R-CH=CH-R; (ii) RC≡CR; and (iii) O=CH-R; wherein R represents H or an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having from 1 to 20 carbon atoms, preferably from 2 to 10 carbon atoms, or two R groups in formula (i) form an unsubstituted or substituted hydrocarbyl ring structure containing from 3 to 8 carbon atoms.

[0157] Particularly preferred passivators have the following formula: (i) CH═CH—R; and (ii) HC≡CR; wherein R is as defined above. Preferably, R is unsubstituted.

[0158] Examples of suitable compounds 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. Mixtures of different passivators can also be used. The preferred passivator is ethylene.

[0159] The alkene, alkyne, or carbonyl groups of the passivating agent are believed to undergo an insertion reaction with M-H groups on the surface of the electroactive material (where M represents an atom of the electroactive material) to form a covalently passivated surface that is resistant to oxidation by air. When silicon is the electroactive material, the passivation reaction between the silicon surface and the passivating agent can be understood as a form of hydrosilylation, as shown schematically below:

[0160] [ka] Other suitable passivating agents include compounds containing active hydrogen atoms bonded to oxygen, nitrogen, sulfur, or phosphorus. For example, the passivating agent may be an alcohol, amine, thiol, or phosphine. It is understood that the reaction of a hydride group with an -XH group on the surface of the electroactive material results in the elimination of H and the formation of a direct bond between X and the surface of the electroactive material.

[0161] Suitable passivators in this category include those of the formula: (iv) HX-R wherein X represents O, S, NR, or PR, and each R is independently as defined above. The two R groups in formula (iv) can also form an unsubstituted or substituted hydrocarbyl ring structure containing 3 to 8 carbon atoms. Preferably, X represents O or NH, and R represents an optionally substituted aliphatic or aromatic group having 2 to 10 carbon atoms. The amine group can also be incorporated into a 4- to 10-membered aliphatic or aromatic ring structure, such as pyrrolidine, pyrrole, imidazole, piperazine, indole, or purine.

[0162] When the passivating agent is a carbon-containing compound, the contacting of the electroactive material with the passivating agent in step (c) can be carried out above or below the thermal decomposition temperature of the passivating agent. When the electroactive material is contacted with the passivating agent at a temperature below the thermal decomposition temperature of the passivating agent, only a passivation layer is formed on the silicon surface. When the electroactive material is contacted with the passivating agent at a temperature above the thermal decomposition temperature of the passivating agent, passivation of the silicon surface occurs with the formation of a pyrolytic carbon coating.

[0163] The contacting of the electroactive material with the passivating agent in step (c) may be carried out at a temperature in the range of 25 to 700° C. and a pressure in the range of 100 kPa to 50 MPa. For example, step (c) may be suitably carried out within the preferred temperature and pressure ranges for step (b) presented herein.

[0164] A further suitable passivating agent is ammonia. Thus, step (c) may involve contacting the surface of the deposited electroactive material with ammonia at a temperature in the range of 200-700°C, preferably 400-700°C. For example, if the passivating agent is ammonia, step (c) can be carried out at the same temperature used to deposit the electroactive material in step (b). The temperature is then optionally raised to a range of 500-1,000°C to form a crystalline nitride surface (e.g., a silicon nitride surface of formula SiNx, where x≦4 / 3). Thus, ammonia passivation provides an alternative means of limiting oxidation of the electroactive material. Because substoichiometric silicon nitride is electrically conductive, this step also results in the formation of a conductive network that allows for faster charging and discharging of the electroactive material.

[0165] The passivation in step (c) can optionally be carried out in the same reactor as step (b), for example, by stopping the flow of silicon precursor gas to the reactor and starting the flow of passivator gas to the reactor. Optionally, the reactor can be flushed with an inert gas prior to step (c).

[0166] The process of the present invention may optionally comprise the further step (d) of forming a conductive carbon coating on the surface of the composite particles from step (b), or from step (c) if a passivation step is performed. Step (d) suitably comprises contacting the electroactive material with a pyrolytic carbon precursor at a temperature above the pyrolysis temperature of the pyrolytic carbon precursor.

[0167] Suitable conditions for step (d) are discussed in detail in US Pat. No. 6,233,999.

[0168] As an example of a fixed-bed reactor (laboratory scale), 1.8 g of particulate porous carbon framework was placed on a stainless steel plate at a constant thickness of 1 mm along its length. The plate was then placed inside a 60 mm outer diameter stainless steel tube with gas inlet and outlet lines located in the hot zone of a retort furnace. The furnace tube was purged with nitrogen gas for 30 minutes at room temperature, and then the sample temperature was increased to 450-500 °C. The nitrogen gas flow rate was adjusted to ensure a gas residence time of at least 90 seconds in the furnace tube and maintained at that flow rate for 30 minutes. Next, the gas supply was switched from nitrogen to a 1.25 vol.% monosilane-in-nitrogen mixture. The monosilane dosing was carried out over a 5-hour period while maintaining the reactor pressure at 101.3 kPa (1 atm). After dosing was completed, the gas flow rate was kept constant while the silane was purged from the furnace using nitrogen. The furnace was then purged under nitrogen for 30 minutes. Optionally, a surface passivation step is then performed by contacting the material with a passivating gas. The furnace is then cooled to room temperature over several hours. The atmosphere is then gradually replaced with air over a two-hour period by switching the gas flow from nitrogen to air from a compressed air source.

[0169] As an example of a fluidized-bed reactor method (production scale), 50 g of granular porous carbon framework was placed in a fluidized-bed reactor constructed with a 0.95 cm (3 / 8 inch) stainless steel gas inlet, a 520 mm long tubular section with an outer diameter (OD) of 60 mm, and a 100 mm OD stainless steel expansion head. The reactor was suspended from the frame, and a vertical tube furnace was positioned so that the hot zone extended from the conical section to three-quarters of the length of the cylindrical section (approximately 380 mm long). Using nitrogen as the inert gas, a cold-flow pressure drop test was used to determine the minimum fluidization velocity, ramping the gas flow rate between 1 and 2.5 L / min. Once the minimum fluidization velocity was determined, the inert gas flow rate was held constant above the minimum fluidization velocity. The furnace was ramped to the desired reaction temperature under a constant inert gas flow rate. After stabilizing at the target temperature between 435 and 500 °C, the fluidization gas was switched from pure nitrogen to monosilane in 1.25 vol% nitrogen. The progress of the reaction was monitored by measuring the pressure drop and the temperature difference above and below the furnace. The gas flow rate was adjusted throughout the run to maintain a pressure drop consistent with continued fluidization, and a minimum temperature difference above and below the bed of less than 40°C was maintained. After 12 hours, the fluidization gas was then switched to pure nitrogen while maintaining fluidization; this purge lasted for 30 minutes. Optionally, a surface passivation step was then performed by contacting the material with a passivation gas. The furnace was then ramped to ambient temperature over several hours. Once ambient temperature was reached, the furnace atmosphere was gradually switched to air over several hours.

[0170] In one example of a reduced-pressure fluidized-bed reactor (production scale) method, 250 g of granular porous carbon framework was placed in a fluidized-bed reactor equipped with multiple nozzles designed for horizontal gas injection at jet velocities of 0.5–2 m / s into a 1100 mm long, 89 mm outer diameter (OD) tubular reactor section and a 457 mm OD stainless steel expansion head. The reactor was suspended from the frame, and a vertical tube furnace was positioned so that the hot zone extended from the conical section through the full length of the cylindrical section (approximately 380 mm long). The reactor vessel was vibrated at frequencies between 5 and 140 Hz. The porous carbon particles were fluidized at 38 kPa (absolute) pressure using 10 sL / min (standard liters per minute) of nitrogen as the inert gas. The furnace was ramped to a temperature of 450 °C under a constant inert gas flow rate. The gas flow was then slowly switched to a mixture of 2 sL / min monosilane (SiH4) and 9 sL / min nitrogen. The silicon deposition rate is monitored by measuring the hydrogen vol% in the off-gas over time. Once approximately 200 g of silicon (approximately 45 wt% Si) has been deposited, the gas flow is switched to a mixture of monosilane (SiH4) at 0.5 sL / min and nitrogen at 9 sL / min until approximately 250 g of silicon (approximately 49.5 to 51.5 wt% Si) has been deposited. The fluidization gas is then switched to pure nitrogen, maintaining fluidization for approximately 30 minutes, to purge the reactor. Optionally, a surface passivation step is then performed by contacting the material with a passivation gas. The furnace is then ramped to ambient temperature over several hours. Once ambient temperature is reached, the furnace atmosphere is gradually switched to air over several hours.

[0171] example The porous carbon frameworks C1 to C7 used in the following examples have the characteristics presented in Table 1.

[0172] [Table 1] [Example]

[0173] Preparation of particulate materials in fixed-bed reactors Silicon-carbon composite particles were prepared by placing 1.8 g of a particulate porous framework with the properties listed in Table 1 on a stainless steel plate at a constant thickness of 1 mm along its length. The plate was then placed inside a 60 mm outer diameter stainless steel tube with gas inlet and outlet lines located in the hot zone of a retort furnace. The furnace tube was purged with nitrogen gas for 30 minutes at room temperature, and then the sample temperature was increased to 450-475 °C. The nitrogen gas flow rate was adjusted to ensure a gas residence time of at least 90 seconds in the furnace tube and maintained at that flow rate for 30 minutes. The gas supply was then switched from nitrogen to a 1.25 vol.% monosilane-in-nitrogen mixture. Dosing of the monosilane was carried out over a period of up to 5 hours while maintaining the reactor pressure at 101.3 kPa (1 atm). After dosing was completed, the gas flow rate was kept constant while the silane was purged from the furnace using nitrogen. The furnace is purged under nitrogen for 30 minutes before being cooled to room temperature over several hours. The atmosphere is then gradually replaced by air over a 2-hour period by switching the gas flow from nitrogen to air from a compressed air source. [Example]

[0174] Determination of surface silicon content A series of samples of composite particles with various amounts of deposited silicon (varying between 20 and 60 wt%) were made using the method of Example 1 using each of the carbons in Table 1. Surface silicon was calculated from the TGA curve for each sample. Table 2 provides the average, maximum, and minimum surface silicon for the group of samples made with each carbon. It can be seen that while very low or inconsistent amounts of surface silicon can be achieved using carbons C1, C2, and C7, good levels of surface silicon can be consistently achieved across all samples using carbons C3, C5, and C6.

[0175] Data from these experiments are shown in FIG.

[0176] [Table 2] [Example]

[0177] Preparation of particulate materials in a fluidized bed reactor Silicon-carbon composite particles were prepared in a vertical bubbling fluidized-bed reactor containing an 83 mm inner diameter stainless steel cylindrical vessel operating at atmospheric pressure. A 250 g quantity of powder of carbon framework particles having the properties listed in Table 1 was placed in the reactor. An inert gas (nitrogen) was injected into the reactor at a low flow rate to remove any oxygen. The reactor was then heated to a reaction temperature of 430 to 500 °C, and 4% v / v monosilane gas diluted in nitrogen was fed into the bottom of the reactor at a flow rate sufficient to fluidize the carbon framework particles for a time sufficient to deposit the target mass of silicon. The reactor was purged under nitrogen for 30 minutes and then cooled to room temperature over several hours. The atmosphere was then gradually replaced by air over a 2-hour period by switching the gas flow from nitrogen to air from a compressed air source. [Example]

[0178] Preparation of particulate materials in a fluidized bed reactor at low pressure. Silicon-carbon composite particles were prepared in a vertical bubbling fluidized-bed reactor containing a stainless steel cylindrical vessel with an inner diameter of 83 mm. A 250 g quantity of powder of carbon framework particles having the properties listed in Table 1 was placed in the reactor. The porous carbon particles were fluidized at 38 kPa (absolute) pressure using 10 sL / min (standard liters per minute) of nitrogen as the inert gas. The furnace was ramped to a temperature of 450 °C under a constant inert gas flow rate. The gas flow was then slowly switched to a mixture of 2 sL / min of monosilane (SiH4) and 9 sL / min of nitrogen. The silicon deposition rate was monitored by measuring the hydrogen vol% in the off-gas over time. Once approximately 200 g of silicon (approximately 45 wt% Si) has been deposited, the gas flow is switched to a mixture of 0.5 sL / min monosilane (SiH4) and 9 sL / min nitrogen until approximately 250 g of silicon (approximately 49.5 to 51.5 wt% Si) has been deposited. The fluidization gas is then switched to 10 sL / min pure nitrogen to purge the reactor, maintaining fluidization for approximately 30 minutes. The fluidization gas is then switched to a mixture of 2 sL / min ethylene (C2H4) and 9 sL / min nitrogen to passivate the silicon surface. The fluidization gas is then switched to 4 sL / min pure nitrogen. The furnace is then allowed to cool to ambient temperature over several hours. Once ambient temperature is reached, the furnace atmosphere is gradually switched to air over several hours. [Example]

[0179] Carbon Coating: A mass of composite particles prepared using the method of Example 3 was placed in a stainless steel tube that was loaded into a rotary kiln tube and sealed. The reactor space was purged with nitrogen at 0.2 L / min for 30 minutes. The furnace temperature was increased to 675°C under the nitrogen flow. A measured amount of styrene was placed in a Dreschel bottle and heated to 75°C in a water bath. After allowing the furnace temperature to stabilize for 10 minutes, styrene was allowed to flow into the reactor tube for 90 minutes by bubbling nitrogen into the Dreschel bottle at 2 L / min. The reactor was then purged with nitrogen and cooled to ambient temperature under nitrogen, resulting in a carbon-coated material. [Example]

[0180] Calculations for surface silicon and rough bulk silicon: The procedure used to calculate the surface silicon and rough bulk silicon for the example composites was as follows: 10 mg (±2 mg) of the sample under investigation was placed in a 70 μL crucible. This sample was loaded into a Mettler Toledo TGA / DSC3+ instrument with Ar purge gas, N2 padding gas, and air reaction gas at 100 mL / min. The TGA furnace chamber was ramped from 25 to 1400 °C at a rate of 10 °C / min. Data were collected at 1 s intervals. Referring to Figures 1 and 2, values ​​for rough bulk silicon and surface silicon were extracted by determining the maximum mass (mg) measured in the temperature range from 550 °C to 650 °C (labeled c), the final ash mass (labeled e), the minimum point below 500 °C after volatile loss (labeled b), and the mass at 800 °C (labeled d). Using the above equations, the values ​​for surface silicon (Y) and rough bulk silicon (Z) were calculated.

[0181] [Table 3] [Example]

[0182] Preparation of the test cell Negative electrode coatings (anodes) were prepared using the Si-C composites in Table 3 and tested in full-coin cells. To make the electrode, a dispersion of carbon black in a CMC binder was mixed in a Thinky™ mixer. The Si-C composite was added to this mixture and mixed in the Thinky™ mixer for 30 minutes. Next, an SBR binder was added to achieve a 1:1 CMC:SBR ratio, resulting in a slurry with a Si-C composite:CMC / SBR:carbon black weight ratio of 70%:16%:14%. The slurry was mixed in the Thinky™ mixer for an additional 30 minutes, then coated onto a 10 μm-thick copper substrate (current collector) and dried at 50° C. for 10 minutes, followed by an additional 12 hours at 110° C., resulting in a coating density of 0.7±0.5 g / cm. 3 A negative electrode of 1000 kJ / cm2 was formed.

[0183] A full coin cell was fabricated using a circular negative electrode with a radius of 0.8 cm cut from the negative electrode with a porous polyethylene separator and a nickel manganese cobalt (NMC532) positive electrode. The positive and negative electrodes were designed to form a balanced pair so that the capacity ratio of the positive electrode to the negative electrode was 0.9. An electrolyte containing 1 M LiPF6 in a solution of fluoroethylene carbonate, ethylene carbonate, and ethyl methyl carbonate containing 3 wt% vinylene carbonate was then added to the cell before sealing.

[0184] The coin cells were cycled as follows: a constant current of C / 25 was applied to lithiate the anode, resulting in a cutoff voltage of 4.3 V. When the cutoff voltage was reached, a constant voltage of 4.3 V was applied until a cutoff current of C / 100 was reached. The cells were then left in the lithiated state for 10 minutes. The anode was then delithiated at a constant current of C / 25 with a cutoff voltage of 2.75 V. The cells were then left for 10 minutes. After this first cycle, a constant current of C / 2 was applied to lithiate the anode to a cutoff voltage of 4.3 V, followed by a constant voltage of 4.3 V with a cutoff current of C / 40 for 5 minutes. The anode was then delithiated at a constant current of C / 2 with a cutoff current of 2.75 V. This was then repeated for the desired number of cycles. The capacity retention at 100 cycles (CR100) and 500 cycles (CR500) was calculated and is shown in Table 4 along with the first lithiation capacity, first delithiation capacity, and first cycle loss (FCL).

[0185] The charge (lithiation) and discharge (delithiation) capacities per cycle are calculated per unit mass of silicon-carbon composite material, and the capacity retention is calculated for each discharge capacity as a percentage of the second cycle discharge capacity. The first cycle loss (FCL) is (1 - (first delithiation capacity / first lithiation capacity)) x 100%. The values ​​in Table 4 are averaged over three coin cells for each material.

[0186] [Table 4]

Claims

1. 1. A particulate material comprising a plurality of composite particles, the composite particles comprising: (a) a porous carbon framework comprising micropores and / or mesopores, the micropores and mesopores being １ cm ３ / g of total pore volume measured by gas adsorption, １ represents a number having a value between 0.5 and 1.5, and a porous carbon framework; (b) a plurality of nanoscale silicon domains located within the micropores and / or mesopores of the porous carbon framework; and wherein the porous carbon framework is an activated carbon material obtained by pyrolysis of a plant source containing at least 25 wt. % lignin on a dry weight basis, followed by activation with water vapor or carbon dioxide; The composite particles are 100 m ２ / g or less BET surface area, A particulate material, wherein the composite particle comprises a lithium ion permeable coating at least partially or completely covering an exterior surface of the particle.

2. The particulate material of claim 1 , wherein the porous carbon framework is activated with water vapor.

3. 3. The particulate material of claim 1 or claim 2, wherein the plant source comprises at least 28 wt%, at least 30 wt%, or at least 35 wt% lignin on a dry weight basis.

4. 4. The particulate material according to any one of claims 1 to 3, wherein the plant source is lignocellulosic material.

5. 5. The particulate material of claim 4, wherein the plant source comprises at least 40 wt%, at least 45 wt%, at least 50 wt%, at least 55 wt%, or at least 60 wt% cellulose and / or hemicellulose on a dry weight basis.

6. 6. The particulate material of claim 5, wherein the lignocellulosic material comprises, on a dry weight basis, at least 30 wt% lignin and at least 50 wt% cellulose and / or hemicellulose.

7. 7. The particulate material of claim 1, wherein the plant source is selected from coconut shells, nut shells, fruit seed shells, coniferous bark, hardwood bark, and bamboo.

8. 8. The particulate material of claim 7, wherein the plant source is coconut shell.

9. 9. The particulate material of claim 1, wherein the porous carbon framework comprises at least 80 wt% carbon, at least 90 wt% carbon, at least 95 wt% carbon, or at least 98 wt% carbon.

10. P １ 10. The particulate material of claim 1, wherein σ has a value of at least 0.55, at least 0.6, at least 0.65, at least 0.7, or at least 0.

75.

11. P １ 11. The particulate material of claim 1, wherein σ has a value of 1.8 or less, 1.6 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1 or less, or 0.95 or less.

12. 12. A particulate material according to any one of claims 1 to 11, wherein the volume fraction of micropores in the porous carbon framework is from 0.43 to 0.

85.

13. The porous carbon framework has a thickness of 1200 to 3000 m ２ 13. A particulate material according to any one of claims 1 to 12, having a BET surface area of ​​1 / g.

14. The porous carbon framework may have a D in the range of 0.5 to 30 μm, 0.5 to 25 μm, 1 to 20 μm, 1 to 15 μm, 1 to 12 μm, 1 to 10 μm, or 1 to 8 μm. ５０ 14. A particulate material according to any one of claims 1 to 13, having a particle size.

15. 15. A particulate material according to any preceding claim, comprising 25 to 65 wt% silicon, or 30 to 65 wt% silicon.

16. 16. The particulate material of claim 15, comprising at least 26 wt%, at least 28 wt%, at least 30 wt%, at least 32 wt%, at least 34 wt%, at least 36 wt%, at least 38 wt%, at least 40 wt%, at least 42 wt%, or at least 44 wt% silicon.

17. 17. The particulate material of claim 15 or claim 16, comprising up to 60 wt%, up to 58 wt%, up to 56 wt%, up to 54 wt%, up to 52 wt%, or up to 50 wt% silicon.

18. The weight ratio of silicon to the porous carbon framework is at least 0.50×P １ , at least 0.55×P １ , at least 0.6×P １ , at least 0.65×P １ , 0.7×P １ , at least 0.75×P １ , at least 0.8×P １ , at least 0.85×P １ , at least 0.9×P １ , at least 0.95×P １ , or at least 1×P １ 18. A particulate material according to any one of claims 1 to 17, wherein

19. The weight ratio of silicon to the porous carbon framework is 1.9×P １ Below, 1.85 x P １ Below, 1.8 x P １ Below, 1.75 x P １ Below, 1.7 x P １ Below, 1.65 x P １ Below, 1.6 x P １ Below, 1.55 x P １ or less, or 1.5 x P １ 19. A particulate material according to any one of claims 1 to 18, wherein:

20. 20. A particulate material according to any one of claims 15 to 19, wherein at least 20 wt%, at least 22 wt%, at least 25 wt%, at least 30 wt%, at least 35 wt%, at least 40 wt%, or at least 45 wt% of the silicon is surface silicon as determined by thermogravimetric analysis (TGA).

21. 21. The particulate material of any one of claims 15 to 20, wherein up to 10 wt% of the silicon, up to 8 wt% of the silicon, up to 6 wt% of the silicon, up to 5 wt%, up to 4 wt%, up to 3 wt%, up to 2 wt%, or up to 1.5 wt% of the silicon is coarse bulk silicon as determined by thermogravimetric analysis (TGA).

22. 22. A particulate material according to any one of claims 15 to 21, wherein at least some of the micropores and / or mesopores comprise voids completely surrounded by the silicon.

23. The composite particles have a D in the range of 1 to 30 μm. ５０ 23. A particulate material according to any one of claims 1 to 22, having a particle size.

24. The composite particles may have a D of at least 0.5 μm, at least 0.8 μm, at least 1 μm, at least 1.5 μm, or at least 2 μm. １０ 24. A particulate material according to any one of claims 1 to 23, having a particle size.

25. The composite particles have a D of 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less. ９０ 25. A particulate material according to any one of claims 1 to 24, having a particle size.

26. The composite particles are 80 m ２ / g or less, 60m ２ / g or less, 50m ２ / g or less, 40m ２ / g or less, 30m ２ / g or less, 25m ２ / g or less, 20m ２ / g or less, 15m ２ / g or less, or 10m ２ 26. A particulate material according to any preceding claim, having a BET surface area of ​​less than or equal to 1 / g.

27. The composite particles have a diameter of at least 0.1 m ２ / g, at least 1 m ２ / g, at least 2m ２ / g, or at least 5m ２ 27. A particulate material according to any one of claims 1 to 26, having a BET surface area of ​​1 / g.

28. The volume of the micropores and mesopores of the composite particles in the presence of silicon, as measured by nitrogen gas adsorption, is 0.15 x P １ Below, 0.10 x P １ Below, 0.05 x P １ or less, or 0.02 x P １ 28. A particulate material according to any one of claims 1 to 27, wherein:

29. 29. A particulate material according to any one of claims 1 to 28, wherein the composite particles are obtained by chemical vapor impregnation (CVI) of a silicon-containing precursor into the pore structure of the porous carbon framework.

30. 30. A particulate material according to any one of claims 1 to 29, wherein the coating completely covers the outer surface of the particle.

31. 31. A particulate material according to any one of claims 1 to 30, wherein the lithium ion permeable coating is impermeable to liquids.

32. 32. A particulate material according to any one of claims 1 to 31, wherein the lithium ion permeable coating comprises a filler material that is electrochemically stable at <0.1 V vs. Li / Li+.

33. 33. A particulate material according to any one of claims 1 to 32, wherein the coating comprises a conductive carbon coating.

34. 33. A particulate material according to any one of claims 1 to 32, wherein the coating comprises a lithium ion permeable solid electrolyte.

35. 1. A particulate material comprising a plurality of composite particles, the composite particles comprising: (a) a porous carbon framework comprising micropores and / or mesopores, the micropores and mesopores being １ cm ３ / g of total pore volume measured by gas adsorption, １ represents a number having a value between 0.5 and 1.5, and a porous carbon framework; (b) a plurality of nanoscale silicon domains located within the micropores and / or mesopores of the porous carbon framework; and wherein the porous carbon framework is an activated carbon material obtained by pyrolysis of coconut shells followed by activation with water vapor or carbon dioxide; The composite particles are 100 m ２ / g or less BET surface area, A particulate material, wherein the composite particle comprises a lithium ion permeable coating at least partially or completely covering an exterior surface of the particle.

36. 36. The particulate material of claim 35, further comprising any of the features of claims 2 and 9 to 34.

37. 37. A composition comprising a particulate material according to any one of claims 1 to 36 and at least one other ingredient.

38. 38. The composition of claim 37, comprising at least one additional particulate electroactive material.

39. 40. The composition of claim 38, comprising 20 to 70 wt%, 25 to 65 wt%, or 30 to 60 wt% of the at least one additional particulate electroactive material.

40. 40. The composition of claim 38 or claim 39, comprising 15 to 60 wt%, 20 to 50 wt%, or 30 to 50 wt% of the particulate material of any one of claims 1 to 31, based on the total dry weight of the composition.

41. 41. The composition of any one of claims 38 to 40, wherein the at least one further particulate electroactive material is selected from graphite, hard carbon, silicon, tin, germanium, aluminum, and lead.

42. 38. The composition of claim 37, which is substantially free of additional particulate electroactive materials.

43. 43. The composition of claim 42, comprising at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, or at least 90 wt% of the particulate material of any one of claims 1 to 31, based on the total dry weight of the composition.

44. 44. The composition of any one of claims 37 to 43, comprising a binder.

45. 45. The composition of claim 44, comprising 0.5 to 20 wt%, 1 to 15 wt%, 2 to 10 wt%, or 5 to 10 wt% of the binder, based on the total dry weight of the composition.

46. 46. ​​The composition of any one of claims 37 to 45, comprising one or more conductive additives.

47. 47. The composition of claim 46, comprising 0.5 to 20 wt%, 1 to 15 wt%, 2 to 10 wt%, or 5 to 10 wt% of the one or more conductive additives, based on the total dry weight of the composition.

48. 37. An electrode comprising the particulate material of any one of claims 1 to 36 in electrical contact with a current collector.

49. 49. An electrode as claimed in claim 48, wherein the particulate material is in the form of a composition as claimed in any one of claims 37 to 47.

50. (i) an anode comprising the electrode of claim 48 or claim 49; (ii) a cathode comprising a cathode active material capable of releasing and reabsorbing metal ions; (iii) an electrolyte between the anode and the cathode; Rechargeable metal ion batteries including:

51. (a) providing a plurality of porous carbon particles comprising micropores and / or mesopores; (i) the porous carbon particles are activated carbon material obtained by pyrolysis of a plant source containing at least 25 wt. % lignin on a dry weight basis, followed by activation with water vapor or carbon dioxide; (ii) The micropores and mesopores are P １ cm ３ / g of total pore volume measured by gas adsorption, １ represents a number having a value between 0.5 and 1.5, Steps and (b) contacting the plurality of porous carbon particles with a silicon precursor gas to deposit silicon within the pores of the porous carbon particles to form composite particles; (c) applying a lithium ion permeable coating to at least partially or completely cover the exterior surface of the composite particles; 35. A method for preparing a particulate material according to any one of claims 1 to 34, comprising:

52. (a) providing a plurality of porous carbon particles comprising micropores and / or mesopores; (i) the porous carbon particles are activated carbon materials obtained by pyrolysis of coconut shells followed by activation with water vapor or carbon dioxide; (ii) The micropores and mesopores are P １ cm ３ / g of total pore volume measured by gas adsorption, １ represents a number having a value between 0.5 and 1.5, Steps and (b) contacting the plurality of porous carbon particles with a silicon precursor gas to deposit silicon within the pores of the porous carbon particles to form composite particles; (c) applying a lithium ion permeable coating to at least partially or completely cover the exterior surface of the composite particles; 37. A method for preparing a particulate material according to claim 35 or claim 36, comprising:

53. 53. The method of claim 51 or claim 52, wherein contacting the plurality of porous carbon particles with a silicon precursor gas occurs at a temperature of 400 to 700°C to deposit silicon within the pores of the porous carbon particles.

54. 53. The method of claim 51 or claim 52, wherein the porous carbon particles are contacted with the silicon precursor gas at an initial temperature below 400°C, and then the reaction temperature is increased to a range of 400-700°C.

55. 55. The method of any one of claims 51 to 54, wherein step (b) is carried out with stirring or fluidizing the porous carbon particles.

56. 56. The method of any one of claims 51 to 55, wherein the coating comprises a conductive carbon coating, the coating being applied by a chemical vapor deposition (CVD) process.

57. The silicon precursor gas is silane (SiH ４ ), silane derivatives, and trichlorosilane (SiHCl ３ 57. The method of any one of claims 51 to 56, wherein the compound is selected from the group consisting of:

58. 58. The method of claim 57, wherein the silane derivative is selected from disilane, trisilane, tetrasilane, and mixtures thereof.

59. 59. The method of any one of claims 51 to 58, wherein the silicon precursor gas is used in pure form or as a diluted mixture with an inert carrier gas.

60. including a further step between step (b) and step (c), 60. The method of any one of claims 51 to 59, wherein the further step comprises contacting an exposed surface of the deposited silicon with a passivating agent, the silicon not being exposed to oxygen prior to contacting with the passivating agent.

61. 61. The method of claim 60, wherein the passivating agent is selected from the group comprising an alkene, alkyne, or carbonyl functional group, more preferably a terminal alkene, terminal alkyne, or aldehyde group.

62. 62. The method of claim 61, wherein the passivating agent is selected from the group comprising ethylene, propylene, 1-butene, butadiene, 1-pentene, 1,4-pentadiene, 1-hexene, 1-octene, styrene, divinylbenzene, acetylene, phenylacetylene, norbornene, norbornadiene, bicyclo[2.2.2]oct-2-ene, and mixtures thereof.

63. 61. The method of claim 60, wherein the passivation agent is a carbon-containing compound, and wherein contacting the exposed surface of the deposited silicon with the passivation agent is carried out at a temperature below a thermal decomposition temperature of the passivation agent.

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