Electroactive materials for metal-ion batteries

Abstract

To provide a method for preparing composite particles having a high electrochemical capacity suitable for use as an anode active material in a rechargeable metal ion battery.SOLUTION: (a) providing a plurality of porous carbon particles comprising micropores and / or mesopores, (b) contacting the plurality of porous carbon particles with a gas comprising a silicon precursor gas at a temperature of from 400 to 700 °C to deposit silicon in the pores of the porous carbon particles, and (c) contacting exposed surfaces of the deposited silicon with a passivating agent, wherein the silicon is not exposed to oxygen prior to being contacted with the passivating agent; and wherein step (b) is performed with agitation or fluidization of the porous carbon particles.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates generally to electroactive materials suitable for use in electrodes of 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 finding application in electric or hybrid vehicles. Rechargeable metal-ion batteries generally have an anode in the form of a metal current collector with a layer of electroactive material. Here, the anode is defined as a material capable of inserting and releasing metal ions during charging and discharging of the battery. The terms "cathode" and "anode" are used to mean that the anode becomes the negative electrode when the battery is placed across a load. 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 to refer to both devices containing a single anode and a single cathode, as well as devices containing multiple anodes and / or multiple cathodes.

[0003] There is interest in improving the gravimetric and / or volumetric capacity of rechargeable metal-ion batteries. To date, commercially available lithium-ion batteries have been primarily limited to using graphite as the anode active material. When a graphite anode is charged, lithium is intercalated between the graphite layers, forming a charge carrier, which is expressed by the empirical formula Li xMaterials with C6 are formed (where 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, although practical capacities are somewhat lower (approximately 340 to 360 mAh / g). Other materials, such as silicon, tin, and germanium, can intercalate lithium at significantly higher capacities than graphite, but are not widely used commercially due to the difficulty of maintaining sufficient capacity over numerous charge / discharge cycles.

[0004] In particular, silicon has been identified as a promising alternative to graphite for the production of rechargeable metal-ion batteries with high gravimetric and volumetric capacities due to its extremely high lithium capacity (see, for example, Winter, M. et al., "Intercalation Electrode Materials for Rechargeable Lithium Batteries," in Adv. Mater. 1998, 10, No. 10). At room temperature, silicon has a capacity of about 3,600 mAh / g (Li 15 The silicon anode has the theoretical maximum specific capacity for lithium-ion batteries (Si4-based). However, when lithium is intercalated into bulk silicon, the volume of the silicon material increases dramatically, up to 400% of its original volume, when the silicon is lithiated to its maximum capacity. Repeated charge-discharge cycles create significant mechanical stresses on the silicon material, resulting in fracture and delamination of the silicon anode material. The volumetric shrinkage of silicon particles during delithiation results in loss of electrical contact between the anode material and the current collector. A further problem is that the solid electrolyte interfacial (SEI) layer formed on the silicon surface does not have sufficient mechanical tolerance to accommodate the expansion and contraction of the silicon. As a result, the newly exposed silicon surface causes further electrolyte decomposition, leading to an increase in the thickness of the SEI layer and irreversible consumption of lithium. These failure mechanisms collectively lead to unacceptable electrochemical capacity loss over a series of charge-discharge cycles.

[0005] Many approaches have been proposed to overcome the problems associated with the volume changes observed during charging of silicon-containing anodes. Microstructures of silicon with cross sections of approximately 150 nm or less, such as silicon films and silicon nanoparticles, have been reported to be more resistant to volume changes during charging and discharging than micron-sized silicon particles. 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] WO 2007 / 083155 discloses that silicon particles with a high aspect ratio, i.e., a high ratio of the particle's maximum dimension to its minimum dimension, can provide improved capacity retention. The small cross-section of such particles reduces structural stress on the material due to volume changes during charge and discharge. However, such particles are difficult, costly, and fragile to manufacture. Furthermore, a large surface area can lead to excessive SEI formation, resulting in excessive capacity loss during the first charge and discharge cycle.

[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. Guo et al. (Journal of Materials Chemistry A, 2013, pp. 14075-14079) discloses silicon-carbon composite materials in which a porous carbon substrate provides a conductive framework and silicon nanoparticles are deposited within the pore structure of the substrate with a uniform distribution. The composite materials have improved capacity retention over multiple charging cycles, but the initial capacity of the composites in mAh / g is shown to be lower in the case of silicon nanoparticles.

[0008] JP 2003100284 discloses an active material having a carbon-based scaffold with small pores branching from a small number of large pores. The electrically active material (e.g., silicon) is randomly arranged on the walls of both the large and small pores and on the outer surface of the carbon-based scaffold.

[0009] Silicon suboxide materials (e.g., 0 <x<2のSiO x ) is used in "hybrid" electrodes containing primarily graphite as the active material. However, upon lithiation during the first charging cycle, SiO x Because of the expansion of SiO and the relatively high irreversible lithium loss x The maximum loading of silicon dioxide is typically about 10% by weight 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 that of silicon oxide, while reducing swelling and capacity loss during the first charging cycle.

[0010] The desirable expansion characteristics of electrode materials must be achieved along with other important properties. In particular, commercially viable alternative electrode materials must offer the benefits of high lithiation capacity along with high capacity retention over multiple charge-discharge cycles. It is also important that any new electroactive material be easily substituted for known materials in conventional electrode fabrication processes. These processes typically rely on calendering the electrode material onto the current collector to densify the electrode layer and improve space utilization within the battery design. Porous materials are prone to fracture during electrode fabrication, resulting in impaired electrochemical properties. Therefore, new electrochemicals are particularly required to possess sufficient structural strength along with increased electrochemical storage capacity and reversible capacity retention. Summary of the Invention [Problem to be solved by the invention]

[0011] The inventors have found that the properties of composites containing silicon and porous carbon depend on the pore structure of the porous carbon skeleton, the amount of silicon, and how it is distributed throughout the porous carbon skeleton. Furthermore, the properties of these composites have been determined to depend on the location of the silicon, its characteristic length scale, and surface functionality.

[0012] In general terms, atoms at the surface of a material are known to have a different set of bonding interactions than 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 usually 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 inaccessible to air remain in the hydride-terminated form.

[0013] Composites with a high proportion of hydride-terminated surface silicon, free of a native oxide layer, have been found to offer improved properties as electroactive materials, and the amount of hydride-terminated surface silicon can be quantified using thermogravimetric analysis (TGA). [Means for solving the problem]

[0014] In a first aspect, the present invention provides a method for producing a medicament for the treatment of a medicament comprising: A particulate material consisting of a plurality of composite particles, The composite particles are (a) a porous carbon skeleton containing micropores and mesopores, The micropores and mesopores are divided into a total pore volume P 1 cm 3 / g, where P 1 represents a number having a value between 0.5 and 1.5, PD 90 The pore diameter is at least 3 nm and less than 12 nm; P 1 a porous carbon skeleton having a micropore volume fraction based on the above formula of 0.43 to 0.85; (b) a plurality of nanoscale elemental silicon domains disposed within the pores of the porous carbon framework; and and the particulate material comprises 25 to 65% by weight silicon; A particulate material is provided, wherein at least 20% by weight of the silicon is surface silicon as measured by thermogravimetric analysis (TGA) methods.

[0015] As a result of this unique particle structure, the composite particles are x The particulate materials of the present invention have electrochemical properties that improve the technology. In particular, the particulate materials of the present invention have higher electrochemical capacity, lower overall expansion, and comparable reversible capacity retention than previously achieved, thereby enabling high loading of electroactive materials with high capacity.

[0016] The composite particles of the present invention have a structure in which a plurality of elemental nanoscale silicon domains are arranged within the pore network of a porous carbon skeleton. As used herein, the term "nanoscale silicon domain" refers to a nanoscale body of elemental silicon having a largest dimension, which is defined by the arrangement of silicon within the micropores and / or mesopores of the porous carbon skeleton.

[0017] Microporous carbon frameworks offer the advantage that the electroactive material is arranged within a micropore network in the form of small domains with dimensions of a few nanometers or less. These fine electroactive structures have lower resistance to elastic deformation and higher fracture resistance than larger electroactive structures, allowing for lithiation and delithiation without excessive structural stress. Thus, the microporosity of the porous carbon framework ensures that the electroactive material itself is sufficiently resilient to withstand repeated volume changes over multiple charge / discharge cycles without significant capacity loss.

[0018] The particulate material of the present invention is characterized by a high content of unoxidized surface silicon, as quantified by TGA analysis. This analysis is based on the principle that weight gain is observed when silicon oxidizes to silicon dioxide (SiO2) at high temperatures in air. The mechanism by which Si is oxidized is temperature dependent. Silicon atoms at the surface of silicon nanostructures oxidize at lower temperatures than silicon atoms in the bulk of the silicon nanostructures (Reference: Bardet et al., Phys. Chem. Chem. Phys. (2016), 18, 18201). TGA analysis can quantify the relative amount of surface silicon based on the weight gain observed when silicon oxidizes to silicon dioxide (SiO2) at high temperatures in air. By plotting the weight gain versus temperature, bulk and surface silicon in a sample can be distinguished and quantified. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 shows a TGA trace of a particulate material according to the present invention containing high levels of surface silicon and low levels of bulk coarse silicon. [Figure 2] FIG. 1 shows a TGA trace of a particulate material containing low levels of surface silicon and high levels of bulk coarse silicon. DETAILED DESCRIPTION OF THE INVENTION

[0020] As shown in Figures 1 and 2, determination of the amount of unoxidized surface silicon can be obtained from the characteristic TGA traces of these materials. Following an initial mass loss up to approximately 300 °C (shown as a mass loss from (a) to (b) in Figures 1 and 2), a significant mass increase is observed beginning at approximately 400 °C, peaking between 550 and 650 °C (shown as a mass increase from (b) to (c) in Figures 1 and 2). Next, as the porous carbon skeleton is oxidized by CO gas, a mass loss is observed (mass loss from (c)). Then, above approximately 800 °C, a mass increase corresponding to the continued conversion of silicon to SiO is observed again, increasing toward an asymptotic value above 1000 °C as silicon oxidation is complete (mass increase from (d) to (e)). 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.

[0021] Native oxide already formed on air-exposed silicon surfaces does not affect TGA analysis because already oxidized silicon does not result in a mass increase in TGA analysis. Thus, the more the silicon surface reacts with air to form native oxide, the less surface silicon will be observed by TGA. Therefore, for the avoidance of doubt, the calculation of "surface silicon" only considers unoxidized silicon at the start of TGA analysis after the material has been passivated with air or other surface passivating agent (i.e., the particulate material is not maintained under any special inert conditions prior to TGA analysis).

[0022] "Surface silicon," as defined herein, is calculated from the initial mass increase in a TGA trace from a minimum between 150°C and 500°C to a maximum measured in the temperature range between 550°C and 650°C. The TGA is performed in air at a temperature ramp rate of 10°C / min. This mass increase is assumed to be due to oxidation of surface silicon, and therefore the percentage of surface silicon relative to the total amount of silicon is determined by the following formula: Y=1.875×[(M max -M min ) / M f ]×100% where Y is the percentage of surface silicon relative to the total silicon in the sample, and M max is the maximum mass of the sample measured in the temperature range between 550 and 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 end of oxidation at 1400°C (mass (e) in Figures 1 and 2). For completeness, it is 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.

[0023] It has been found that reversible capacity retention over multiple charge-discharge cycles is significantly improved when the surface silicon, as measured by the aforementioned TGA method, is at least 20% by weight of the total amount of silicon in the material. Preferably, at least 22%, at least 25%, at least 30%, or at least 35%, or at least 40%, or at least 45% by weight of the silicon is surface silicon as determined by thermogravimetric analysis (TGA).

[0024] Where desired, 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 be in 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 may be defined by combining the upper and lower limits of any of the foregoing ranges.

[0025] The fact that a significant proportion of hydride-terminated surface silicon is measurable in the particle material even after passivation in air indicates that the composite particles have interior silicon surfaces that are inaccessible to air. This suggests that the interior pore space of the porous carbon framework is first surrounded by silicon before being capped, forming interior void spaces, and that the hydride-terminated silicon surfaces are oriented within the closed interior void spaces. This indicates that the silicon domains have a characteristic length scale that is much smaller than that of the pores themselves.

[0026] 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 substantially prevented, making SEI formation a less significant failure mechanism leading to capacity loss. At the same time, the silicon is hydrostatically constrained during lithiation, allowing the voids to be utilized during the lithiation-induced expansion.

[0027] The porous carbon skeleton has a three-dimensionally interconnected open pore network including micropores and mesopores. The porous carbon skeleton may also have a small number of macropores, if desired. Following conventional IUPAC terminology, the term "micropore" is used to refer to pores with a diameter of less than 2 nm, the term "mesopore" is used to refer to pores with a diameter of 2 to 50 nm, and the term "macropore" is used to refer to pores with a diameter of more than 50 nm.

[0028] It has been recognized that the high levels of surface silicon required by the present invention can only be obtained when the pore structure of the porous carbon skeleton is controlled within specific ranges as described above, which represent the micropore, mesopore, and macropore volumes within the porous carbon skeleton, represent the distribution of volumes within the porous carbon skeleton, and represent the internal pore volume of the isolated porous carbon skeleton (i.e., in the absence of electroactive or other materials occupying some or all of the pore volume).

[0029] The total volume of micropores and mesopores (i.e., the total pore volume of pores with diameters ranging from 0 to 50 nm) is P 1 cm 3 / g, where P 1 represents a dimensionless number having a value between 0.5 and 1.5. For the avoidance of doubt, when reference is made to the pore volume of a porous carbon skeleton, it relates to the pore volume of the porous carbon skeleton measured alone (unless indicated to the contrary), i.e., in the absence of any electroactive material (or other material) occupying the pores of the porous carbon skeleton.

[0030] 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 higher porosity skeleton is significant because it allows a greater amount of silicon to be accommodated within the pore structure while maintaining the porous carbon skeleton's resistance to fracture under compressive stresses during electrode fabrication or under expansion stresses due to silicon lithiation. However, P 1If P is too high, the elevated level of surface silicon that is a feature of the present invention cannot be achieved. 1 is preferably 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.

[0031] For example, P1 may 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 1.3, 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.

[0032] According to the standardized method described in ISO15901-2 and ISO15901-3, the relative pressure is p / p0=10 using quenched solid density functional theory (QSDFT). -6 Nitrogen gas adsorption at 77 K, reduced to 77 °C, is used to determine the total volume of micropores and mesopores, as well as the pore size distribution of micropores and mesopores. Nitrogen gas adsorption is a technique for characterizing the porosity and pore size distribution of a material by condensing a gas into the pores of a solid. As pressure is increased, the gas condenses first in the smallest diameter pores, and the pressure is increased until a saturation point is reached where all pores are filled with liquid. The nitrogen gas pressure is then gradually reduced, and the liquid is evaporated from the system. Analysis of the adsorption and desorption isotherms and the hysteresis between them allows the pore volume and pore size distribution to be determined. Instruments suitable for measuring pore volume and pore size distribution by nitrogen gas adsorption include the TriStar II and TriStar II Plus Porosity Analyzers available from Micromeritics Instruments, Inc., USA, and the AutosorbIQ Porosity Analyzer available from Quantachrom Instruments, Inc.

[0033] Nitrogen gas adsorption is effective for measuring pore volume and pore size distribution for pores with diameters up to 50 nm, but is less reliable for larger diameter pores. Therefore, for the purposes of this invention, nitrogen adsorption is used to measure pore volume and pore size distribution only for pores with diameters up to 50 nm. As previously mentioned, P 1 The value of is determined by considering only pores up to 50 nm in diameter (i.e., only micropores and mesopores).

[0034] General term “PD n "Pore diameter" refers to the n-percentage pore diameter based on volume, based on the total volume of micropores and mesopores. For example, the term "PD 90 "Pore diameter" is P 1 represents the pore diameter at which 90% or less of the total micropore and mesopore volume is obtained.

[0035] As mentioned above, the PD of the porous carbon framework 90 The pore diameter is at least 3 nm and less than 12 nm. 90 It has been observed that if the value is too low, it becomes difficult to deposit silicon in the micropores, and instead silicon is deposited on the outer surface of the porous carbon skeleton. 90 Too high a value will result in too much rough silicon deposition and / or too much native oxide formation, resulting in low amounts of surface silicon.

[0036] PD of porous carbon frameworks 90 The pore diameter is preferably 10 nm or less, 8 nm or less, or 6 nm or less. 90 The pore diameter is at least 3.2 nm, at least 3.5 nm, at least 3.8 nm, or at least 4 nm. For example, the PD of the porous carbon skeleton 90 The pore diameter is preferably in the range of 3.5 to 10 nm, 3.8 to 8 nm, or 4 to 6 nm.

[0037] PD of porous carbon frameworks 75The pore diameter is preferably 10 nm or less, 8 nm or less, 6 nm or less, or 4 nm or less. 75 The pore diameter is preferably at least 1 nm.

[0038] PD of porous carbon frameworks 50 The pore diameter is preferably 2 nm or less, 1.9 nm or less, 1.8 nm or less, 1.7 nm or less, or 1.6 nm or less. 50 The pore diameter is at least 1 nm, at least 1.1 nm, or at least 1.2 nm. For example, the PD of the porous carbon skeleton 50 The pore diameter is preferably in the range of 1 to 2 nm, 1 to 1.9 nm, 1.1 to 1.8 nm, 1.1 to 1.7 nm, 1.2 to 1.6 nm.

[0039] PD of porous carbon frameworks 30 The pore diameter is preferably 1.6 nm or less, 1.5 nm or less, 1.4 nm or less, 1.3 nm or less, 1.2 nm or less, 1.1 nm or less, or 1 nm or less. 30 The pore diameter is at least 0.6 nm, or at least 0.7 nm.

[0040] PD 30 PD relative to pore diameter 90 The pore diameter ratio is preferably 14 or less, 12 or less, 10 or less, or 8 or less.

[0041] PD 10 PD relative to pore diameter 90 The pore diameter ratio is preferably 11 or less, 10 or less, 9 or less, 8 or less, 7 or less.

[0042] The micropore volume fraction represents the volume of micropores expressed as a fraction of the total volume of micropores and mesopores, denoted as P1. In other words, the micropore volume fraction 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. As mentioned above, the micropore volume fraction of the porous scaffold is selected in the range of 0.43 to 0.85 to obtain the required high level of surface silicon content in the composite particles.

[0043] Preferably, the micropore volume fraction 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 micropore volume fraction 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.

[0044] The micropore volume fraction may be 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, 0.6 to 0.72, or 0.6 to 0.7, if desired, based on the total volume of micropores and mesopores.

[0045] The total volume of the micropores within the porous carbon skeleton (determined using nitrogen gas adsorption at 77 K) is preferably at least 0.36 cm 3 / g, at least 0.38 cm 3 / g, at least 0.40 cm 3 / g, at least 0.42 cm 3 / g. Because the silicon located within the micropores has a smaller length scale, a higher total micropore volume allows a higher fraction of the surface silicon to be accommodated within the porous carbon skeleton, thus allowing for higher gravimetric and volumetric capacities of the composite particles.

[0046] It is preferred that any pore volume within the mesopore range be substantially within the smaller mesopore range. Thus, the fractional volume of pores with a pore size of 5 nm or less is preferably at least 0.8, at least 0.82, at least 0.84, at least 0.86, at least 0.88, or at least 0.9, based on the total volume of micropores and mesopores. Preferably, the fractional volume of pores with a pore size of 10 nm or less is preferably at least 0.9, at least 0.92, at least 0.94, or at least 0.96, based on the total volume of micropores and mesopores. Preferably, the fractional volume of pores with a pore size of 20 nm or less is preferably at least 0.94, at least 0.96, or at least 0.98, based on the total volume of micropores and mesopores.

[0047] The proportion of pores with diameters in the larger mesopore range is significant in facilitating electrolyte access to the silicon domains. Thus, pores with diameters in the 10 to 50 nm range (i.e., larger mesopores) may comprise up to 2%, 4%, or 6% of the total micropore and mesopore volume of the porous carbon skeleton, if desired.

[0048] The pore size distribution of the porous carbon skeleton is preferably bimodal or multimodal. The term "pore size distribution" refers to the distribution of pore sizes relative to the cumulative total internal pore volume of the porous carbon skeleton. A bimodal or multimodal pore size distribution is preferred, as the close proximity between micropores and larger diameter pores provides the advantage of efficient ion transport through the porous network to the silicon. Thus, the particulate material has a high ion diffusivity and therefore improved kinetic properties.

[0049] Given the limitations of available analytical techniques, it is not possible to measure the pore volume and pore size distribution across the entire range of micropores, mesopores, and macropores using a single technique. When a porous carbon skeleton contains macropores, the volume of pores in the range greater than 50 nm to 100 nm is determined by P 2 cm 3 It is defined as a value of / g and is measured by mercury pore measurement. 2 The value of relates to the pore volume of the porous carbon skeleton when measured alone, i.e., in the absence of silicon or other materials occupying the pores of the porous carbon skeleton.

[0050] For the avoidance of doubt, P 2 The value of P considers only pores with diameters greater than 50 nm up to 100 nm, i.e., only the volume of macropores with diameters up to 100 nm. The pore volume measured by mercury porosimetry for pore sizes below 50 nm is 2 (As mentioned above, nitrogen adsorption techniques are 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 is therefore ignored for the purposes of determining the value of P 2 is not taken into account when determining the value of

[0051] Mercury porosimetry is a technique for characterizing the porosity and pore diameter distribution of a material by applying varying 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. Reported values ​​obtained by mercury porosimetry, obtained according to ASTM UOP578-11, are 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. 3Many high-precision mercury porosimeters are commercially available, such as the AutoPore IV series of automated mercury porosimeters available from Micromeritics Instrument, Inc., USA. For a complete review of mercury porosimetry, see PA Webb and C. Orr, "Analytical Methods in Fine Particle Technology," 1997, Micromeritics Instrument, Inc., ISBN 0-9656783-0.

[0052] The volume of the macropores (hence P 2 The value of ) is the volume of micropores and mesopores (hence P 1 Although a small portion of the macropores may be used 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.

[0053] Therefore, in the present invention, the total volume of macropores in the porous carbon skeleton, as measured by mercury porosimetry, is P 2 cm 3 / g, where P 2 is preferably up to 0.2 x P 1 , max. 0.1×P 1 , max. 0.05×P 1 , max. 0.02×P 1 , max. 0.01×P 1 , or up to 0.005 × P 1 It has a value of

[0054] It is understood that intrusion techniques such as gas adsorption and mercury porosimetry are only effective in determining the pore volume of the pores accessible to nitrogen or mercury from the exterior of the porous carbon skeleton. 1 and P 2) is understood to represent the volume of open pores, i.e., pores accessible to fluids from outside the porous carbon skeleton. Completely closed pores that cannot be identified by nitrogen adsorption or mercury porosimetry measurements are not considered when determining the porosity value. Similarly, any pore volume located within pores small enough to be below the detection limit by nitrogen adsorption is considered to be P 1 is not taken into account when determining the value of

[0055] The porous carbon skeleton is preferably 1200 to 3000 m 2 / g. Preferably, the porous carbon skeleton has a BET surface area of ​​at least 1500 m 2 / g, or at least 1700m 2 / g. Preferably, the porous carbon skeleton has a BET surface area of ​​2500 m 2 / g or less, or 2000m 2 / g or less. The term "BET surface area" is considered to represent 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 according to ISO 9277.

[0056] The porous carbon skeleton may comprise crystalline or amorphous carbon, or a mixture of amorphous and crystalline carbon. The porous carbon skeleton may be either a rigid or flexible carbon skeleton and may be suitably obtained by known processes, including pyrolysis of carbon-containing materials, including organic materials, resins, and polymers. Porous carbon materials may also be obtained by other processes, for example, from carbide-containing precursors. Highly porous carbon materials are commercially available and are commonly referred to as activated carbons.

[0057] The porous carbon skeleton preferably has an elemental composition comprising at least 90% by weight carbon, preferably at least 95% by weight carbon, more preferably at least 98% by weight carbon, or at least 99% by weight carbon. The porous carbon skeleton may optionally contain small amounts of other elements such as oxygen, nitrogen, sulfur, and hydrogen. The elemental composition of the porous carbon skeleton may be determined by conventional elemental analysis techniques performed in the absence of silicon.

[0058] As used herein, the term "hard carbon" refers to carbon atoms primarily composed of sp 2 atoms in nanoscale polyaromatic domains. 2 It represents a disordered carbon matrix found in a hybridized state (trigonal bonding). The polyaromatic domains are cross-linked by chemical bonds, e.g., C-O-C bonds.

[0059] Due to chemical cross-linking between polyaromatic domains, hard carbons do not convert to graphite at high temperatures. Hard carbons are characterized by a large G-band (~1600 cm) in the Raman spectrum. -1 ), it has graphitic properties. However, it has a prominent D-band (~1350 cm) in the Raman spectrum. -1 ), the carbon is not completely graphitized.

[0060] Also, as used herein, the term "soft carbon" refers to carbon atoms primarily in polyaromatic domains with dimensions ranging from 5 to 200 nm. 2 It represents a disordered carbon matrix found in a hybridized state (trigonal bonding). In contrast to hard carbon, the polyaromatic domains of soft carbon are held together by intermolecular forces but are not cross-linked by chemical bonds. This means that they graphitize at high temperatures. The porous carbon skeleton preferably has at least 50% sp as measured by XPS. 2 It contains hybrid carbon. For example, the porous carbon skeleton contains 50% to 98% sp 2 Hybrid carbon, 55% to 95% sp 2 Hybrid carbon, 60% to 90% sp 2 Hybrid carbon, or 70% to 85% sp2 It may preferably have carbon.

[0061] A variety of different materials may be used to prepare suitable porous carbon skeletons. Examples of organic materials that can be used include plant biomass, including lignocellulosic materials (such as coconut shells, rice husks, and wood), and fossil carbon sources such as coal. Examples of resins and polymeric materials that form porous carbon skeletons upon pyrolysis include phenolic resins, novolac resins, pitch, melamine, polyacrylates, polystyrene, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers having monomer units of acrylates, styrenes, α-olefins, vinylpyrrolidone, and other ethylenically unsaturated monomers. Depending on the starting materials and the conditions of the pyrolysis process, a variety of different hard carbon materials are available in the art.

[0062] The porous carbon skeleton may be subjected to a chemical or gas activation process to enhance the mesopore and micropore volume. A suitable activation process comprises contacting the pyrolytic carbon with one or more of oxygen, steam, CO, CO2, and KOH at a temperature in the range of 600 to 1000°C. Preferably, the porous carbon skeleton is a steam-activated porous carbon skeleton.

[0063] Mesopores can also be obtained by known templating processes using extractable pore formers, such as MgO and other colloidal or polymeric templates, which can be removed by thermal or chemical means after pyrolysis or activation.

[0064] The elemental composition of the composite particles can be determined by elemental analysis. Elemental analysis is used to determine the weight percent of both silicon and carbon in the composite particles. If necessary, the amounts of hydrogen, nitrogen, and oxygen may also be determined by elemental analysis. Preferably, elemental analysis is used to determine the weight percent of carbon (and hydrogen, nitrogen, and oxygen, if necessary) in the porous carbon skeleton alone. Simply determining the weight percent of carbon in the porous carbon skeleton takes into account the possibility that the porous carbon skeleton may contain small amounts of heteroatoms within its molecular framework. By performing both measurements together, the weight percent of silicon relative to the total porous carbon skeleton can be determined with high confidence.

[0065] The silicon content is preferably measured 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 skeleton alone (and, if necessary, 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.

[0066] The particulate material of the present invention contains 25 to 65% silicon by weight, preferably 30 to 65% silicon by weight, as determined by elemental analysis. Preferably, the particulate material of the present invention contains at least 26%, at least 28%, at least 30%, at least 32%, at least 34%, at least 36%, at least 38%, at least 40%, at least 42%, or at least 44% silicon by weight. The particulate material of the present invention contains no more than 60%, no more than 58%, no more than 56%, no more than 54%, no more than 52%, or no more than 50% silicon by weight.

[0067] For example, the particulate material of the present invention may comprise 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.

[0068] For commercial use, a minimum amount of silicon is required to ensure that the particulate material has sufficient deposition capacity, however, excessive amounts of silicon can result in large pores and / or deposition on the surface of the porous carbon skeleton, resulting in low surface silicon content and reduced properties as an electroactive material.

[0069] The amount of silicon in the composite particles of the present invention is selected so that at least about 20% and up to about 78% of the interior pore volume of the porous carbon skeleton (based on micropores and mesopores) is occupied by silicon (uncharged). Generally, the higher the micropore fraction of the porous carbon skeleton, the greater the amount of silicon that can be used without reducing the percentage of surface silicon.

[0070] Preferably, silicon occupies about 20% to about 78% of the internal pore volume of the porous carbon skeleton, 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 skeleton. Within these preferred ranges, the pore volume of the porous carbon skeleton 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 high as to prevent effective lithiation due to insufficient metal ion diffusion rates or insufficient expansion volume that creates mechanical resistance to lithiation.

[0071] The amount of silicon in the porous carbon skeleton is determined by the weight ratio of silicon to the porous carbon skeleton being [0.50 × P 1 From 1.9 x P 1]:1, which can be correlated to the available pore volume. This relationship takes into account the density of silicon and the pore volume of the porous carbon scaffold, and determines the weight ratio of silicon when the pore volume is estimated to be about 20% to 78% occupied. Preferably, the weight ratio of silicon to porous carbon scaffold is in the range of [0.7×P 1 From 1.8 x P 1 ]:1, which indicates that the pore volume is approximately 30% to 78% occupied.

[0072] Preferably, the weight ratio of silicon to porous carbon skeleton 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 , at least 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 Preferably, the weight ratio of silicon to porous carbon skeleton 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.

[0073] The composite particles preferably have a low total oxygen content, as measured by elemental analysis. Oxygen may be present in the composite particles, for example, as part of the porous carbon skeleton or as an oxide layer on the exposed silicon surface. Preferably, the total oxygen content of the composite particles is less than 15% by weight, more preferably less than 12% by weight, more preferably less than 10% by weight, more preferably less than 5% by weight, for example, less than 4% by weight, less than 3% by weight, less than 2% by weight, less than 1% by weight, or less than 0.5% by weight. Preferably, silicon and carbon together constitute at least 90% by weight of the composite particles, more preferably at least 95% by weight of the composite particles.

[0074] 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 dopants.

[0075] In addition to the surface silicon content, the particulate material of the present invention preferably has a low content of coarse bulk silicon, as measured by TGA. Coarse bulk silicon is defined as silicon that undergoes oxidation above 800°C, as measured by TGA, performed in air at a temperature ramp rate of 10°C / min. In Figures 1 and 2, this is shown as increasing in mass from (d) to (e). The content of coarse bulk silicon is therefore determined according to the following formula: Z = 1.875 × [(M f -M 800 ) / M f ]×100% where Z is the percentage of unoxidized silicon at 800°C and M 800 is the mass of the sample at 800°C (mass (d) in Figures 1 and 2), and M fis the ash mass at the end of oxidation at 1400°C (mass (e) in Figures 1 and 2). In this analysis, any mass increase above 800°C corresponds to the oxidation of silicon to SiO2, and it is assumed that the total mass at the end of oxidation is SiO2.

[0076] Preferably, no more than 10 wt%, no more than 8 wt%, no more than 6 wt%, 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 measured by TGA.

[0077] 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) is surface silicon and 10 wt% or less of the silicon is coarse bulk silicon, both as measured 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) is surface silicon and 8 wt% or less of the silicon is coarse bulk silicon, both as measured 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) is surface silicon and 5 wt% or less of the silicon is coarse bulk silicon, both as measured by TGA. More preferably, at least 45 wt% of the silicon is surface silicon and no more than 2 wt% of the silicon is coarse bulk silicon, both as measured by TGA.

[0078] Preferably, the total volume of micropores and mesopores in the composite particles (i.e., in the presence of silicon) is at most 0.15×P as measured by nitrogen gas adsorption. 1 , max. 0.10×P 1 Up to 0.05 x P 1 , or up to 0.02 × P 1 is.

[0079] Preferably, the total volume of micropores and mesopores in the composite particles, as measured by nitrogen gas adsorption, is less than 0.2 cm3 / 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.

[0080] The term "particle diameter" refers to the equivalent spherical diameter (esd), i.e., the diameter of a sphere having the same volume as a given particle, where it is understood that the particle volume (volume) includes the volume of any intra-particle pores. 50 " and "D 50 The term "particle diameter" refers to the volume-based median particle diameter, i.e., the diameter at which less than 50% by volume of the particle population is found. 10 " and "D 10 The term "particle diameter" refers to the median particle diameter on a 10% volume basis, i.e., the diameter at which less than 10% by volume of the particle population is found. 90 " and "D 90 The term "particle diameter" refers to the 90% volume median particle diameter, i.e., the diameter at which less than 90% by volume of the particle population is found.

[0081] The "D" used to define particle diameter distribution n The term "PD" is used to define the pore diameter distribution, as mentioned above. n " is distinguished from the term "

[0082] Particle diameter and particle size distribution can be measured by conventional laser diffraction techniques according to ISO 13320:2009. Unless otherwise noted, particle size distribution measurements specified and reported herein are measured using a conventional Malvern Mastersizer™ 3000 particle size analyzer. The Malvern Mastersizer™ 3000 particle size analyzer operates by illuminating a transparent cell containing particles of interest suspended in an aqueous solution with a helium-neon gas laser beam. Light striking the particles is scattered through an angle inversely proportional to 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 define the particle size distribution. Laser diffraction values ​​are obtained using a wet dispersion of particles in 2-propanol with 5 vol% of the surfactant SPAN™-40 (sorbitan monopalmitate). The particle refractive index is taken to be 2.68 for the porous carbon skeleton particles and 3.50 for the composite particles, and the dispersant index is taken to be 1.378. The particle size distribution is calculated using the Mie scattering model.

[0083] The composite particles have a D in the range of 1 to 30 μm. 50 If necessary, the particle diameter may be 50 The particle diameter 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 diameter 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.

[0084] 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. 50Particles within these size ranges and having the aforementioned porosity and pore diameter distributions are ideally suited for use in anodes for metal-ion batteries due to their dispersibility in slurries, their structural robustness, their capacity retention over repeated charge-discharge cycles, and their suitability for forming dense electrode layers of uniform thickness in the conventional 20 to 50 μm range.

[0085] D of composite particles 10 The particle diameter is preferably at least 0.5 μm, at least 0.8 μm, or at least 1 μm. 10 Maintaining particle diameters 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.

[0086] D of composite particles 90 The particle diameter 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 packing of particles in the electrode active layer, thus inhibiting the formation of a dense electrode layer, particularly an electrode layer having a thickness in the range of 20 to 50 μm. Therefore, D 90 Preferably the particle diameter is up to 40 μm, more preferably even smaller.

[0087] The composite particles preferably have a narrow 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 size distribution span, efficient packing of particles into a dense electrode layer can be more easily achieved.

[0088] The composite particles preferably have a positive skew, e.g., the volume-based distribution may be asymmetric with a longer tail on the right. A positive skew in the volume-based particle size distribution is significant because it provides a denser electrode due to a higher natural packing than if all particles were the same size, thereby reducing the need for calendering or other physical densification processes. 50 The composite particle diameter is preferably smaller than the volume-based mean value (D[4.3]) of the particle diameter distribution. The skewness of the composite particle size distribution (as measured with a Malvern Mastersizer™ 3000 analyzer) is preferably 5 or less, or 3 or less.

[0089] The composite particles may have an average sphericity (as defined herein) of at least 0.5, or at least 0.55. Preferably, the average sphericity is at least 0.65, at least 0.7, at least 0.75, or at least 0.8.

[0090] Highly accurate two-dimensional projections of micron-scale particles can be obtained by scanning electron microscopy (SEM) or dynamic image analysis, which uses a digital camera to record the shadows cast by the particles. The term "sphericity" is understood as the ratio of the area of ​​the particle projection (obtained from such imaging techniques) to the area of ​​a circle, where the particle projection and the circle have the same circumference. Therefore, for an individual particle, the sphericity S is defined as:

[0091]

number

[0092]

number

[0093] 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.

[0094] Generally, a low BET surface area is preferred because it minimizes the formation of a solid electrolyte interfacial layer (SEI) 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 low BET surface area can result in unacceptably low charge rates and capacity limitations due to the inaccessibility of the bulk of the electroactive material to metal ions in the surrounding electrolyte. 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.

[0095] The particulate material of the present invention typically has a specific charge capacity of 900 to 2300 mAh / g upon first lithiation. Preferably, the particulate material of the present invention has a specific charge capacity of at least 1200 mAh / g, or at least 1400 mAh / g upon first lithiation.

[0096] The particulate material of the present invention may, if desired, have its silicon surface treated with a passivating agent, which, as described in more detail below, is defined 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.

[0097] The composite particles of the present invention may, if necessary, 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. 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. The lithium-ion permeable filler material has a resistance of <0.1V Li / Li + It is preferable that the material is electrochemically stable to a certain extent.

[0098] If desired, the coating may include a conductive carbon coating. Suitable conductive carbon coatings may be obtained by chemical vapor deposition (CVD). CVD is a method well known in the art and involves the thermal decomposition of a volatile carbon-containing gas (e.g., ethylene) on the surface of the particulate material. Alternatively, the carbon coating may be formed by depositing a solution of a carbon-containing compound on the surface of the particulate material and then thermally decomposing it. The conductive carbon coating has sufficient permeability to allow lithium access to the interior of the composite particle without excessive resistance and without degrading the kinetic properties of the composite particle. For example, the thickness of the carbon coating may suitably be in the range of 2 to 30 nm. If desired, the carbon coating may be porous and / or cover only a portion of the surface of the composite particle.

[0099] 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 perovskite-type solid electrolytes (including "LLZO" electrolytes such as Li 0.33 La 0.57 including "LLTO" electrolytes such as TiO3); LISICON-type solid electrolytes, NaSICON-type solid electrolytes (Li 1.3 Al 0.3 Ti 1.7 (PO4)3, etc.); lithium phosphate nitride (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.

[0100] 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 losses. The use of an electrically conductive coating, such as a carbon coating, is particularly advantageous because it improves the conductivity of the composite particle's surface, improves the rate characteristics 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 provides 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 of the particle is determined in weight percent based on the weight of the particle including the coating.

[0101] A preferred particulate material according to the present invention is P 1The particle material may have a pore volume fraction of 0.65 to 1.2, a micropore volume fraction of 0.5 to 0.7, and the particle material may comprise 38 to 58 wt. % silicon, with at least 30 wt. % of the silicon being surface silicon as measured by thermogravimetric analysis (TGA) (e.g., 30 to 75 wt. %, 30 to 70 wt. %, or 30 to 65 wt. % of the silicon being surface silicon). Preferably, 10 wt. % or less of the silicon being coarse bulk silicon as measured by TGA. Additionally, any of the features disclosed herein may be applied to this embodiment as appropriate or required.

[0102] A more preferred particulate material according to the present invention is P 1 ranges from 0.7 to 1.1, the micropore volume fraction ranges from 0.48 to 0.76, the particulate material comprises 40 to 58 wt. % silicon, and 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) is surface silicon as measured by thermogravimetric analysis (TGA). Preferably, 8 wt. % or less of the silicon is coarse bulk silicon as measured by TGA. Additionally, any of the features disclosed herein may be applied to this embodiment as appropriate or required.

[0103] A more preferred particulate material according to the present invention is P 1 The particle material preferably comprises 42 to 56 wt. % silicon, and at least 40 wt. % of the silicon is surface silicon as measured by thermogravimetric analysis (TGA) (e.g., 40 to 65 wt. %, 40 to 60 wt. %, or 40 to 55 wt. % of the silicon is surface silicon as measured by TGA). Preferably, 5 wt. % or less of the silicon is coarse bulk silicon as measured by TGA. Additionally, any of the features disclosed herein may be applied to this embodiment as appropriate or required.

[0104] A more preferred particulate material according to the present invention is P 1ranges from 0.8 to 1, the micropore volume fraction ranges from 0.52 to 0.72, the particulate material comprises 44 to 54 wt% silicon, and at least 45 wt% of the silicon is surface silicon as measured by thermogravimetric analysis (TGA) (e.g., 45 to 65 wt%, 45 to 60 wt%, or 45 to 55 wt% of the silicon). Preferably, 2 wt% or less of the silicon is coarse bulk silicon as measured by TGA. Additionally, any of the features disclosed herein may be applied to this embodiment as appropriate or required.

[0105] The composite particles of the present invention are suitably prepared by chemical vapor infiltration (CVI) of a silicon-containing precursor into the pore structure of a porous carbon skeleton. CVI describes a process in which a gaseous silicon-containing precursor is thermally decomposed on a surface to form elemental silicon on the surface and gaseous by-products.

[0106] In a second aspect of the present invention, there is provided a method for preparing silicon-containing composite particles, comprising the steps of: (a) providing a plurality of porous carbon particles comprising micropores and / or mesopores; (i) Micropores and mesopores are the total pore volume P measured by gas adsorption method. 1 cm 3 / g, where P 1 represents a value between 0.5 and 1.5, (ii)PD 90 The pore diameter is at least 3 nm or less and less than 12 nm, (iii)P 1 The micropore volume fraction based on the step is 0.43 to 0.85; (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 in the pores of the porous carbon particles; A method is provided, comprising:

[0107] In a third aspect of the present invention, there is provided a method for preparing silicon-containing composite particles, comprising the steps of: (a) providing a plurality of porous carbon particles comprising micropores and / or mesopores; (i) Micropores and mesopores are the total pore volume P measured by gas adsorption method. 1 cm 3 / g, where P 1 represents a value between 0.5 and 1.5, (ii)PD 90 The pore diameter is at least 3 nm or less and less than 12 nm, (iii)P 1 The micropore volume fraction based on the step is 0.43 to 0.85; (b) contacting the plurality of porous carbon particles with a gas containing a silicon precursor gas at a temperature of 400 to 700°C to deposit silicon in the pores of the porous carbon particles, wherein the partial pressure of the silicon precursor gas is 0.5 to 20 kPa; A method is provided, comprising:

[0108] The processes of the second and third aspects of the invention may be used to prepare the particulate material of the first aspect of the invention. The following preferred features apply to both the second and third aspects unless otherwise stated.

[0109] Suitable gaseous silicon-containing precursors include silane (SiH4), silane derivatives (e.g., disilane, trisilane, and tetrasilane), and trichlorosilane (SiHCl3).

[0110] If necessary, 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.

[0111] The silicon-containing precursors can be used in pure form or, more commonly, as a dilute mixture with an inert carrier gas such as nitrogen or argon.

[0112] Step (b) is preferably carried out at a low partial pressure of silicon precursor, with a total pressure of 101.3 kPa (i.e., 1 atmosphere) or less, with the remaining partial pressure being increased to atmospheric pressure using an inert pad gas such as hydrogen, nitrogen, or argon.

[0113] In a second aspect of the present invention, the silicon-containing precursor is used in an amount ranging from 0.5 to 20 vol%, for example 1 to 15 vol%, 1 to 10 vol%, 1 to 5 vol%, preferably at least 3 vol%, based on the total volume of the silicon precursor gas and the inert carrier gas.

[0114] In a third aspect of the present invention, the partial pressure of the silicon precursor gas 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 pure silicon precursor gas is used, 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 the partial pressure of an inert pad gas such as nitrogen or argon.

[0115] Step (b) uses a temperature in the range of 400 to 700° C., preferably 425 to 550° C., or 425 to 500° C. If necessary, the porous carbon particles are contacted with the silicon precursor gas at an initial temperature below 400° C., after which the reaction temperature is increased to a range of 400 to 700° C.

[0116] Step (b) is carried out with stirring or fluidization of the porous carbon particles, if necessary, 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 entrained bed reactors).

[0117] 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 compared to the diffusion rate of the silicon precursor gas into the pore structure of the porous carbon skeleton. Furthermore, operation in the preferred temperature range of 425-500°C and the use of low concentrations of silicon precursor gas allow for control of the silicon deposition rate, which can be low compared to the silicon precursor infiltration rate. Additionally, conditions within the CVI reactor should be as uniform as possible: agitation or flow of the porous carbon particles ensures uniform penetration of the silicon precursor gas into the particles and also ensures a uniform temperature within the reactor throughout the particle bed.

[0118] 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.

[0119] When step (b) is carried out at sub-atmospheric absolute pressure, it results in significantly improved surface silicon content of the particulate material product.

[0120] Preferred operating conditions for step (b) to form a particulate material product containing greater than 20% surface silicon include using 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. Referring to the accompanying examples, operation within these preferred conditions reliably provides particulate materials having extremely high surface silicon contents of at least 30% or at least 40%. By carefully selecting porous carbon particles in conjunction with the use of controlled CVI conditions described herein, particulate materials with extremely high surface silicon content and low coarse bulk silicon content can be obtained, indicating the presence of a high proportion of silicon in the form of ultrafine silicon nanostructures. Such materials have not previously been reported in the art.

[0121] When exposed to atmospheric oxygen, the surface of an electroactive material deposited by CVI reacts with the oxygen to form a native oxide layer. In the case of silicon, an amorphous silicon dioxide film is rapidly formed when the silicon surface is exposed to oxygen. The formation of the native oxide layer is an exothermic reaction, and therefore careful process control is required to prevent overheating or combustion of the particulate material during manufacturing or storage. The presence of the native oxide layer is associated with irreversible capacity loss and reduced cycle life, and therefore may be detrimental to the performance of the electroactive material in lithium-ion batteries. Therefore, the method of the present invention may, if necessary, include an additional step (c) of contacting the exposed surface of the deposited silicon with a passivating agent, where the silicon is not exposed to oxygen before contacting the passivating agent.

[0122] A passivator is defined 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.

[0123] Suitable passivating agents include compounds containing an alkene, alkyne, or carbonyl functional group, more preferably a terminated alkene, terminated alkyne, or aldehyde group.

[0124] Suitable passivating agents include one or more compounds of the following formula: (i) R-CH=CH-R; (ii) RC≡CR; (iii) O=CH-R; wherein R represents H or an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, preferably 2 to 10 carbon atoms, or two R groups in formula (i) form an unsubstituted or substituted hydrocarbyl ring structure containing 3 to 8 carbon atoms.

[0125] Particularly preferred passivators include compounds of one or more of the following formulae: (i) CH2=CH-R; (ii) HC≡CR; wherein R is as defined above. Preferably, R is unsubstituted.

[0126] 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 passivating agents can also be used. The preferred passivating agent is ethylene.

[0127] 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:

[0128] [ka] Other suitable passivating agents include compounds containing an active hydrogen atom 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 an -XH group with a hydride 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.

[0129] Suitable passivators in this category include compounds 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) may 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 may also be incorporated into a 4- to 10-membered aliphatic or aromatic ring structure, such as in pyrrolidine, pyrrole, imidazole, piperazine, indole, or purine.

[0130] When the passivation agent is a carbon-containing compound, the contact of the electroactive material with the passivation agent in step (c) may be carried out at a temperature higher or lower than the thermal decomposition temperature of the passivation agent. When the electroactive material is contacted with the passivation agent at a temperature lower than the thermal decomposition temperature of the passivation agent, only a passivation layer is formed on the silicon surface. When the electroactive material is contacted with the passivation agent at a temperature higher than the thermal decomposition temperature of the passivation agent, passivation of the silicon surface occurs with the formation of a pyrolytic carbon coating.

[0131] 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 suitable temperature and pressure ranges for step (b) described herein.

[0132] Another suitable passivating agent is ammonia. Step (c) may therefore comprise contacting the surface of the deposited electroactive material with ammonia at a temperature in the range of 200 to 700°C, preferably 400 to 700°C. For example, when the passivating agent is ammonia, step (c) may be carried out at the same temperature as that used for depositing the electroactive material in step (b). The temperature may then be increased, if necessary, to a range of 500 to 1,000°C to form a crystalline nitride surface (e.g., a nitride of the general formula SiN x (where x≦4 / 3) is formed. Ammonia passivation therefore provides an alternative means of inhibiting oxidation of electroactive materials. Because substoichiometric silicon nitride is electrically conductive, this process leads to the formation of a conductive network, allowing for faster charging and discharging of the electroactive material.

[0133] The passivation in step (c) may, if necessary, 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. If necessary, the reactor may be flushed with an inert gas prior to step (c).

[0134] The method of the present invention may optionally have the additional 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.

[0135] Suitable conditions for step (d) are described in detail in WO 2021 / 048556.

[0136] As an example of a fixed-bed reactor (laboratory scale), 1.8 g of granular porous carbon skeleton was placed on a stainless steel plate with a uniform thickness of 1 mm along its entire length. The plate was then placed in a 60 mm outer diameter stainless steel tube with gas inlet and outlet lines located in the hot zone of a retort furnace. After purging the furnace tube with nitrogen gas at room temperature for 30 minutes, 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 rate for 30 minutes. Next, the gas supply was switched from nitrogen to a mixture containing 1.25 vol% monosilane in nitrogen. The monosilane dosing was carried out over a 5-hour period while maintaining the reactor pressure at 101.3 kPa (1 atm). After dosing, the silane was purged from the furnace with nitrogen while maintaining the gas flow rate constant. If necessary, a surface passivation step is then performed by exposing the material to a passivating gas. The furnace is then cooled to room temperature over several hours. The atmosphere is then gradually switched to air over a two-hour period by switching the gas flow from nitrogen to air from a compressed air source.

[0137] As an example of a fluidized-bed reactor method (production scale), 50 g of granular porous carbon skeleton was placed in a fluidized-bed reactor constructed with a 0.95 cm (3 / 8 inch) stainless steel gas inlet, a 520 mm total length, a 60 mm outer diameter (OD) tubular section, and a 100 mm OD stainless steel expansion head. The reactor was suspended from a frame, and a vertically oriented tube furnace was positioned so that the hot zone extended from the conical section to 3 / 4 of the total length of the cylindrical section (approximately 380 mm long). The minimum fluidization velocity was determined by cold-flow pressure drop tests using nitrogen as the inert gas at a ramped gas flow rate from 1 to 2.5 L / min. Once the minimum fluidization velocity was determined, the inert gas flow rate was maintained constant at a value equal to or greater than the minimum fluidization velocity. The furnace was then ramped to the desired reaction temperature under constant inert gas flow. After stabilization at the target temperature of 435-500°C, the fluidization gas was switched from pure nitrogen to 1.25 vol% monosilane in nitrogen. The reaction progress was monitored by measuring the pressure drop between the top and bottom and the temperature difference in the furnace. The gas flow rate was adjusted throughout the run to maintain a pressure drop consistent with continuous fluidization and a minimum temperature difference of less than 40°C between the top and bottom of the bed. After 12 hours, the fluidization gas was switched to pure nitrogen while maintaining fluidization, and this purge continued for 30 minutes. If necessary, a surface passivation step was performed by contacting the material with a passivation gas. The furnace was then cooled to ambient temperature over several hours. After reaching ambient temperature, the furnace atmosphere was gradually switched to air over several hours.

[0138] As an example of a reduced-pressure fluidized-bed reactor method (production scale), 250 g of particulate porous carbon skeleton was placed in a fluidized-bed reactor fabricated with multiple nozzles designed for horizontal gas injection at jet velocities of 0.5 to 2 m / s into a tubular reactor section with a total length of 1100 mm and an outer diameter (OD) of 89 mm, and a stainless steel expanded head with an OD of 457 mm. The reactor was suspended from a frame, and a vertically oriented tube furnace was positioned so that the hot zone extended from the conical section along the entire length of the cylindrical section (total length approximately 380 mm). The reactor vessel was vibrated at frequencies of 5 to 140 Hz. The porous carbon particles were fluidized at a pressure of 38 kPa (absolute) using 10 sL / min (standard liters per minute) of nitrogen as the inert gas. The furnace was raised 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 is monitored by measuring the volume percent of hydrogen in the effluent 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 of monosilane (SiH4) and 9 sL / min of 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 pure nitrogen, maintaining fluidization for approximately 30 minutes, and the reactor is purged. If necessary, a surface passivation step is then performed by contacting the material with a passivation gas. The furnace is then cooled to ambient temperature over several hours. Once ambient temperature is reached, the furnace atmosphere is gradually switched to air over several hours.

[0139] In a fourth aspect of the present invention, there is provided a composition comprising a particulate material according to the first aspect of the present invention and at least one other component. In particular, there is provided a composition having 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) an additional particulate electroactive material. The composition of the fourth aspect of the present invention is useful as an electrode composition and may therefore be used to form the active layer of an electrode.

[0140] The particulate material used to prepare the composition of the fourth aspect of the invention may have any of the features described as preferred or optional in relation to the first aspect of the invention.

[0141] The composition may be a hybrid electrode composition comprising the particulate material according to the first aspect of the present invention and at least one additional particulate electroactive material. Examples of the additional particulate electroactive material include graphite, hard carbon, silicon, tin, germanium, aluminum, and lead. The at least one additional particulate electroactive material is preferably selected from graphite and hard carbon, and most preferably, the at least one additional particulate electroactive material is graphite.

[0142] In the case of a hybrid electrode composition, the composition preferably comprises from 3 to 60%, 3 to 50%, 5 to 50%, 10 to 50%, or 15 to 50% by weight of particulate material according to the first aspect of the invention, based on the total dry weight of the composition.

[0143] The at least one additional particulate electroactive material is suitably present in an amount of from 20 to 95%, from 25 to 90%, or from 30 to 750% by weight of the at least one additional particulate electroactive material.

[0144] The at least one additional 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 to have a particle diameter.

[0145] D of at least one additional particulate electroactive material 10 The particle diameter is preferably at least 5 μm, more preferably at least 6 μm, more preferably at least 7 μm, more preferably at least 8 μm, more preferably at least 9 μm, and even more preferably at least 10 μm.

[0146] D of at least one additional particulate electroactive material 90 The particle diameter 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.

[0147] The at least one additional particulate electroactive material is preferably selected from carbon-containing particles, graphite particles, and / or hard carbon particles, the graphite and hard carbon particles having a D in the range of 10 to 50 μm. 50 Even more preferably, the at least one additional particulate electroactive material is selected from graphite particles, the graphite particles having a particle diameter D in the range of 10 to 50 μm. 50 It has a particle diameter.

[0148] The composition may also be a non-hybrid (or "highly filled") electrode composition that is substantially free of additional particulate electroactive material. In this context, the term "substantially free of additional particulate electroactive material" should be understood 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. %, based on the total dry weight of the composition, of any additional electroactive material (i.e., additional material that can insert and release metal ions during charging and discharging of the battery).

[0149] "Highly loaded" electrode compositions of this type preferably comprise at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% by weight of particulate material according to the first aspect of the invention, based on the total dry weight of the composition.

[0150] The composition may contain a binder, if necessary. 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 the present invention include polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, carboxymethyl cellulose (CMC), modified carboxymethyl cellulose (mCMC), sodium carboxymethyl cellulose (Na-CMC), polyvinyl alcohol (PVA), alginates and their alkali metal salts, styrene-butadiene rubber (SBR), and polyimides. The composition may contain a mixture of binders. Preferably, the binder contains a polymer selected from polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0151] The binder may suitably be present in an amount of from 0.5 to 20% by weight, preferably from 1 to 15% by weight, preferably from 2 to 10% by weight, most preferably from 5 to 10% by weight, based on the total dry weight of the composition.

[0152] The binder may, if desired, 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.

[0153] The composition may optionally contain one or more conductive additives. Preferred conductive additives are non-electroactive materials introduced 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 additive may be suitably selected from carbon black, carbon fiber, carbon nanotubes, graphene, acetylene black, ketjen black, metal fiber, metal powder, and conductive metal oxide. Preferred conductive additives include carbon black and carbon nanotubes.

[0154] 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.

[0155] In a fifth aspect, the present invention provides an electrode comprising a particulate material as defined in relation to the first aspect of the invention in electrical contact with a current collector. The particulate material used in preparing the electrode of the fifth aspect of the invention may have any of the features preferably or optionally described in relation to the first aspect of the invention.

[0156] The term "current collector" as used herein refers to any conductive substrate capable of carrying electrical current to or from the electroactive particles in the composition. Examples of materials that can be used as current collectors include copper, aluminum, stainless steel, nickel, titanium, and sintered carbon. Copper is a preferred material. 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 may be applied to one or both surfaces of the current collector, preferably to a thickness ranging from 10 μm to 1 mm, e.g., 20 to 500 μm, or 50 to 200 μm.

[0157] The electrode preferably comprises a composition as defined in relation to the fourth aspect of the invention in electrical contact with a current collector. The composition may have any of the preferred or any of the described features in relation to the fourth aspect of the invention.

[0158] The electrode of the fifth aspect of the present invention may be suitably prepared by combining the particulate material of the present invention (if necessary 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. Optionally, additional steps may be performed, such as heat treatment to cure any binder and / or calendering the electrode layer. The electrode layer suitably has a thickness of 20 μm to 2 mm, preferably 20 μm to 1 mm, preferably 20 μm to 500 μm, preferably 20 μm to 200 μm, preferably 20 μm to 100 μm, preferably 20 μm to 50 μm.

[0159] Alternatively, the slurry may 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 forming template, removing the solvent, and then removing the forming template. The resulting film or mat is in the form of a coherent, free-standing mass, which may then be bonded to a current collector by conventional methods.

[0160] The electrode of the fifth aspect of the invention may be used as the anode of a metal-ion battery. Accordingly, in a sixth aspect, the invention provides a rechargeable metal-ion battery comprising an anode having an electrode as described above, a cathode comprising a cathode active material capable of releasing and reabsorbing metal ions, and an electrolyte between the anode and the cathode.

[0161] The metal ions are preferably lithium ions. More preferably, the rechargeable metal ion battery of the present invention is a lithium ion battery, and the cathode active material is capable of releasing and accepting lithium ions.

[0162] The cathode active material is preferably a metal oxide-based composite material. Examples of suitable cathode active materials include LiCoO, LiCo 0.99 Al 0.01 O2, LiNiO2, LiMnO2, LiCo 0.5 Ni0.5 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.

[0163] The electrolyte is preferably a non-aqueous electrolyte containing a metal salt, such as a lithium salt, and may include, but is not limited to, a non-aqueous electrolyte 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, gamma butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, sulfolane, methyl sulfolane, and 1,3-dimethyl-2-imidazolidinone.

[0164] 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.

[0165] Examples of inorganic solid electrolytes include nitrides, halides and sulfides of lithium salts, such as Li5NI2, Li3N, LiI, LiSiO4, Li2SiS3, Li4SiO4, LiOH and Li3PO4.

[0166] The lithium salt is suitably soluble in the selected solvent or mixture of solvents. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO4, LiBF4, LiBC4O8, LiPF6, LiCF3SO3, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, and CF3SO3Li.

[0167] 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 pore diameter between 0.01 and 100 μm and a thickness between 5 and 300 μm. Examples of suitable electrode separators include microporous polyethylene membranes.

[0168] The separator may be replaced with a polymer electrolyte material, in which case the polymer electrolyte material is present in both the composite anode layer and the composite cathode layer. The polymer electrolyte material may be a solid polymer electrolyte or a gel-type polymer electrolyte.

[0169] (example) The porous carbon skeletons C1 to C13 used in the following examples have the characteristics shown in Table 1.

[0170] [Table 1] (Example 1: Preparation of particle material in a static furnace) Silicon-carbon composite particles were prepared by depositing 1.8 g of a particulate porous scaffold with the properties listed in Table 1 onto a stainless steel plate at a uniform thickness of 1 mm along its entire 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. After purging the furnace tube with nitrogen gas at room temperature for 30 minutes, the sample temperature was increased to between 450 and 475 °C. The nitrogen gas flow rate was adjusted to ensure a gas residence time of at least 90 seconds within the furnace tube and maintained at that rate for 30 minutes. The gas supply was then switched from nitrogen to a mixture of monosilane at a concentration of 1.25 vol% in nitrogen. The monosilane dosing was carried out for a period of up to 5 hours while maintaining the reactor pressure at 101.3 kPa (1 atm). After dosing, the silane was purged from the furnace with nitrogen while the gas flow rate remained constant. The furnace is purged under nitrogen for 30 minutes, then allowed to cool to room temperature over several hours. The atmosphere is then gradually switched to air over a 2-hour period by switching the gas flow from nitrogen to air from a compressed air source.

[0171] (Example 2: Determination of surface silicon content) Using the method of Example 1, a series of samples of composite particles with varying amounts of deposited silicon (varying between 20 and 60 wt%) were prepared using each of the carbons listed in Table 1. Surface silicon was calculated from the TGA curves of each sample. Table 2 shows the average, maximum, and minimum surface silicon for the group of samples prepared with each carbon. It can be seen that carbons C1, C10, and C13 yield very little or negligible amounts of surface silicon, while all samples, including carbons C3, C4, C5, C7, C8, and C9, consistently yield good levels of surface silicon. The other carbons yielded varying levels of surface silicon.

[0172] [Table 2] Example 3: Preparation of particulate material 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 operated at atmospheric pressure. 250 g of powdered carbon skeleton particles with the properties listed in Table 1 were placed in the reactor. An inert gas (nitrogen) was injected into the reactor at a low flow rate to remove oxygen. The reactor was then heated to a reaction temperature between 430 and 500 °C, and 4% by volume monosilane gas diluted with nitrogen was fed into the bottom of the reactor at a flow rate sufficient to fluidize the carbon skeleton particles for a period long enough 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 switched from nitrogen to air over a 2-hour period by switching the gas flow from nitrogen to air from a compressed air supply.

[0173] Using the method of Example 3, particulate materials S1, S2, and S4 to S8 in Table 3 were prepared.

[0174] Example 4: Preparation of particulate material 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. 250 g of powder of carbon skeleton particles with the properties listed in Table 1 was placed in the reactor. The porous carbon particles were fluidized at a pressure of 38 kPa (absolute) using 10 sL / min (standard liters per minute) of nitrogen as the inert gas. The furnace was then heated 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 volume percent of hydrogen in the effluent gas over time. Once approximately 200 g of silicon (approximately 45 wt% Si) has been deposited, the gas flow rate 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 and the reactor is purged while 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.

[0175] Using the method of Example 4, particulate materials S9 to S11 in Table 3 were prepared.

[0176] (Example 5: Carbon coating) A mass of composite particles prepared using the method of Example 3 was placed in a stainless steel tube mounted in a rotary furnace tube and sealed. The reactor space was purged with nitrogen at 0.2 L / min for 30 minutes. The furnace temperature was heated to 675°C under nitrogen flow. A measured amount of styrene was placed in a Dressel bottle and heated to 75°C in a water bath. Ten minutes after the furnace temperature stabilized, styrene was flowed into the reactor tube by bubbling nitrogen through the Dressel bottle at 2 L / min for 90 minutes. The reactor was then purged with nitrogen and cooled to ambient temperature under nitrogen. This resulted in a carbon-coated material.

[0177] Particulate material S3 in Table 3 was prepared by the method of Example 3 and then coated with carbon using the method of Example 4.

[0178] (Example 6: Calculation of surface silicon and bulk silicon) The following procedure was used to calculate the surface silicon and coarse bulk silicon of the example composites. 10 mg (±2 mg) of the test sample was placed in a 70 μL crucible. The sample was loaded into a Mettler Toledo TGA / DSC 3+ instrument with 100 mL / min of Ar purge gas, N2 pad gas, and air reaction gas. The TGA furnace chamber was heated from 25°C to 1400°C at a rate of 10°C / min. Data were collected at 1-second intervals. Figure 1 shows the TGA plot for a sample of Material S1 from Table 3, and Figure 2 shows the plot for a sample of Material S7 from Table 3. Values ​​for coarse bulk silicon and surface silicon were extracted by determining the maximum mass (mg) measured in the temperature range of 550 to 650°C (label c), the final ash mass (label e), the minimum mass below 500°C after volatile loss (label b), and the mass at 800°C (label d). Using the above formulas, the values ​​of surface silicon (Y) and bulk coarse silicon (Z) are calculated.

[0179] [Table 3] Comparative Samples S7 and S8 demonstrate the importance of carefully controlled conditions in FBR reactions. In Comparative Sample S7, interruption of the fluidization gas supply caused defluidization of particles in the reactor bed and the formation of an excess temperature zone within the reactor, resulting in reduced silicon penetration and increased silicon deposition on the surface of the porous carbon skeleton (as indicated by an increase in coarse silicon measurements). In Comparative Sample S8, the temperature of the FBR reaction was changed so that the reaction was partially carried out below 400°C. Without being bound by theory, it is believed that silicon deposition in micropores is kinetically significant at temperatures above 400°C, especially above 425°C, while at lower temperatures silicon deposition on the outer surface of the porous carbon skeleton increases.

[0180] Samples S9 to S11 demonstrate the effect of performing step (b) at subatmospheric pressure: Samples S1 to S6 contain 22 wt % to 40 wt % surface silicon after preparation in the atmospheric pressure CVI process, while Samples S9 to S11, prepared at 38 kPa, contain approximately 50 wt % surface silicon.

[0181] Example 7: Preparation of test cells Negative electrode coatings (anodes) were prepared using the Si-C composites listed in Table 3, and full-coin cell tests were conducted. To fabricate the electrodes, a dispersion of carbon black in a CMC binder was mixed in a Thinky™ mixer. The Si-C composite was added to the mixture and mixed in the Thinky™ mixer for 30 minutes. Next, SBR binder was added to achieve a 1:1 CMC:SBR ratio to prepare a slurry with a Si-C composite:CMC / SBR:carbon black weight ratio of 70%:16%:14%. After mixing the slurry in the Thinky™ mixer for an additional 30 minutes, it was coated onto a 10 μm-thick copper substrate (current collector), dried at 50°C for 10 minutes, and then further dried at 110°C for 12 hours, resulting in a coating density of 0.7±0.5 g / cm. 3 A negative electrode of 1000 kJ / cm2 was formed.

[0182] A full coin cell was fabricated using a porous polyethylene separator, a nickel manganese cobalt (NMC532) positive electrode, and a circular negative electrode with a radius of 0.8 cm cut from the negative electrode. The positive and negative electrodes were designed to form a balanced pair, with a capacity ratio of the positive electrode to the negative electrode of 0.9. An electrolyte containing 1 M LiPF6 in a solution of fluoroethylene carbonate, ethylene carbonate, and 3 wt% vinylene carbonate in ethyl methyl carbonate was then added to the cell and sealed.

[0183] The coin cells were cycled as follows: a constant current was applied at a rate of C / 25 to lithiate the anode. The cutoff voltage was 4.3 V. When the cutoff was reached, a constant voltage of 4.3 V was applied until a cutoff current of C / 100 was reached. The cell was then allowed to rest in the lithiation 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 cell was then allowed to rest for 10 minutes. After this initial cycle, a constant current of C / 2 was applied to lithiate the anode at a cutoff voltage of 4.3 V, followed by a 5-minute rest period and a constant voltage of 4.3 V with a cutoff current of C / 40. The anode was then delithiated at a constant current of C / 2 with a cutoff voltage 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).

[0184] The charge (lithiation) and discharge (delithiation) capacities for each 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 discharge capacity at the second cycle. The first cycle loss (FCL) is (1 - (1st delithiation capacity / 1st lithiation capacity)) × 100%. The values ​​in Table 4 are averaged across three coin cells for each material.

[0185] [Table 4]

Claims

1. A particulate material consisting of a plurality of composite particles, The composite particles are (a) a porous carbon skeleton containing micropores and mesopores, The micropores and mesopores are divided into two parts by the total pore volume P 1 cm 3 / g, where P 1 represents a number having a value between 0.5 and 1.5, PD 90 The pore diameter is at least 3 nm and less than 12 nm; P 1 a porous carbon skeleton having a micropore volume fraction based on the micropore volume fraction of 0.43 to 0.85; (b) a plurality of nanoscale elemental silicon domains disposed within the pores of the porous carbon skeleton; and the particulate material comprises 25 to 65% by weight of silicon; A particulate material, wherein at least 20% by weight of said silicon is surface silicon as measured by thermogravimetric analysis (TGA).

2. P 1 2. 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.

3. P 1 3. The particulate material of claim 1, wherein σ has a value of 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1 or less, or 0.95 or less.

4. PD of the porous carbon skeleton 90 4. A particulate material according to claim 1, wherein the pore diameter is 10 nm or less, 8 nm or less, or 6 nm or less.

5. PD of the porous carbon skeleton 90 5. A particulate material according to claim 1, wherein the pore diameter is at least 3.2 nm, at least 3.5 nm, at least 3.8 nm, or at least 4 nm.

6. PD of the porous carbon skeleton 75 6. A particulate material according to claim 1, wherein the pore diameter is 10 nm or less, 8 nm or less, 6 nm or less, or 4 nm or less.

7. PD of the porous carbon skeleton 50 7. A particulate material according to claim 1, wherein the pore diameter is 2 nm or less, 1.9 nm or less, 1.8 nm or less, 1.7 nm or less, or 1.6 nm or less.

8. PD of the porous carbon skeleton 50 8. A particulate material according to claim 1, wherein the pore diameter is at least 1 nm, at least 1.1 nm, or at least 1.2 nm.

9. PD of the porous carbon skeleton 30 9. A particulate material according to any one of claims 1 to 8, wherein the pore diameter is 1.6 nm or less, 1.5 nm or less, 1.4 nm or less, 1.3 nm or less, 1.2 nm or less, 1.1 nm or less, or 1 nm or less.

10. PD of the porous carbon skeleton 30 10. A particulate material according to any one of claims 1 to 9, wherein the pore diameter is at least 0.6 nm, or at least 0.7 nm.

11. 11. A particulate material according to any one of claims 1 to 10, wherein the micropore volume fraction of the porous carbon skeleton is at least 0.45, at least 0.48, at least 0.5, 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 the micropores and mesopores.

12. 12. A particulate material according to any one of claims 1 to 11, wherein the micropore volume fraction of the porous carbon skeleton is 0.8 or less, 0.79 or less, 0.78 or less, 0.76 or less, 0.74 or less, 0.72 or less, or 0.7 or less, based on the total volume of the micropores and mesopores.

13. The total volume of the micropores within the porous carbon skeleton is at least 0.36 cm 3 / g, at least 0.38 cm 3 / g, at least 0.40 cm 3 / g, or at least 0.42 cm 3 13. The particulate material according to claim 1, wherein the pore size is 1 / g.

14. 14. A particulate material according to any one of claims 1 to 13, wherein the volume fraction of pores having a pore size of 5 nm or less is at least 0.8, at least 0.82, at least 0.84, at least 0.86, at least 0.88, or at least 0.

9.

15. 15. A particulate material according to any one of claims 1 to 14, wherein the volume fraction of pores having a pore diameter of 10 nm or less is at least 0.9, at least 0.92, at least 0.94, or at least 0.

96.

16. 16. A particulate material according to any one of claims 1 to 15, wherein the volume fraction of pores having a pore size of 20 nm or less is at least 0.94, at least 0.96, or at least 0.

98.

17. 17. A particulate material according to any one of claims 1 to 16, wherein the porous carbon skeleton has a bimodal or multimodal pore size distribution.

18. The total volume of pores with diameters in the range of >50 nm to 100 nm is P 2 cm 3 / g, where P 2 is 0.2×P 1 Below, 0.1×P 1 Below, 0.05 x P 1 Below, 0.02 x P 1 Below, 0.01 x P 1 or less, or 0.005 x P 1 18. A particulate material according to any one of claims 1 to 17, wherein:

19. The porous carbon skeleton has a thickness of 1200 to 3000 m 2 19. The particulate material according to claim 1, having a BET surface area of ​​1 / g.

20. 20. The particulate material of any one of claims 1 to 19, comprising at least 26% by weight, at least 28% by weight, at least 30% by weight, at least 32% by weight, at least 34% by weight, at least 36% by weight, at least 38% by weight, at least 40% by weight, at least 42% by weight, or at least 44% by weight silicon.

21. 21. A particulate material according to any one of claims 1 to 20, comprising up to 60% by weight silicon, up to 58% by weight silicon, up to 56% by weight silicon, up to 54% by weight silicon, up to 52% by weight silicon, or up to 50% by weight silicon.

22. 22. A particulate material according to any one of claims 1 to 21, wherein the porous carbon skeleton is a steam-activated porous carbon skeleton.

23. 23. The particulate material of claim 1, wherein the porous carbon skeleton comprises at least 80% by weight carbon, at least 90% by weight carbon, at least 95% by weight carbon, at least 98% by weight carbon, or at least 99% by weight carbon.

24. The weight ratio of silicon to the porous carbon skeleton 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 , at least 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 24. The particulate material according to any one of claims 1 to 23, wherein

25. The weight ratio of silicon to the porous carbon skeleton 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 25. A particulate material according to any one of claims 1 to 24, wherein:

26. 26. A particulate material according to any one of claims 1 to 25, wherein at least 22%, at least 25%, at least 30%, at least 35%, at least 40%, or at least 45% by weight of the silicon is surface silicon as measured by thermogravimetric analysis (TGA).

27. 27. The particulate material of any one of claims 1 to 26, wherein up to 10% by weight of the silicon, up to 8% by weight of the silicon, up to 6%, up to 5%, up to 4%, up to 3%, up to 2%, or up to 1.5% by weight of the silicon is coarse bulk silicon as measured by thermogravimetric analysis (TGA).

28. 28. A particulate material according to any one of claims 1 to 27, wherein at least some of the micropores and / or mesopores have void spaces completely sealed by the silicon.

29. The composite particles have a D in the range of 1 to 30 μm. 50 29. A particulate material according to any one of claims 1 to 28, having a particle diameter of 1000 mm.

30. 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 30. A particulate material according to any one of claims 1 to 29, having a particle diameter of 1000 mm.

31. The composite particles may 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 31. A particulate material according to any one of claims 1 to 30, having a particle diameter of 1000 mm.

32. The composite particles are 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 32. The particulate material according to claim 1, having a BET surface area of ​​less than or equal to 1 / g.

33. The composite particles have a diameter of at least 0.1 m 2 / g, at least 1m 2 / g, at least 2m 2 / g, or at least 5m 2 33. The particulate material according to claim 1, having a BET surface area of ​​1 / g.

34. In the presence of silicon, the volume of the micropores and mesopores of the composite particles is 0.15×P 1 Below, 0.10 x P 1 Below, 0.05 x P 1 or less, or 0.02 x P 1 34. A particulate material according to any one of claims 1 to 33, wherein:

35. 35. A particulate material according to any one of claims 1 to 34, wherein the composite particles are obtained by chemical vapor infiltration (CVI) of a silicon-containing precursor into the pore structure of a porous carbon skeleton.

36. 36. A composition comprising the particulate material of any one of claims 1 to 35 and at least one other ingredient.

37. 37. The composition of claim 36, comprising at least one additional particulate electroactive material.

38. 38. The composition of claim 37, comprising 20 to 70 wt%, 25 to 65 wt%, or 30 to 60 wt% of the at least one additional particulate electroactive material.

39. 39. The composition of claim 37 or 38, 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 35, based on the total dry weight of the composition.

40. 40. The composition of any one of claims 37 to 39, wherein the at least one additional particulate electroactive material is selected from graphite, hard carbon, silicon, tin, germanium, aluminum, and lead.

41. 37. The composition of claim 36, wherein the composition is substantially free of additional particulate electroactive material.

42. 42. The composition of claim 41, 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 35, based on the total dry weight of the composition.

43. 43. The composition of any one of claims 36 to 42, comprising a binder.

44. 44. The composition of claim 43, 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.

45. 45. The composition of any one of claims 36 to 44, comprising one or more conductive additives.

46. 46. ​​The composition of claim 45, 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.

47. 36. An electrode comprising the particulate material of any one of claims 1 to 35 in electrical contact with a current collector.

48. 48. An electrode as claimed in claim 47, wherein the particulate material is in the form of a composition as claimed in any one of claims 36 to 46.

49. 1. A rechargeable metal-ion battery comprising: (i) an anode having the electrode of claim 47 or 48; (ii) a cathode comprising a cathode active material capable of releasing and resorbing metal ions; (iii) an electrolyte between the anode and the cathode; A metal-ion battery comprising:

50. 1. A method for preparing composite particles, comprising: (a) providing a plurality of porous carbon particles comprising micropores and / or mesopores; (i) The micropores and mesopores are determined by the total pore volume P measured by gas adsorption method. 1 cm 3 / g, where P 1 represents a number having a value between 0.5 and 1.5, (ii) PD 90 The pore diameter is at least 3 nm and less than 12 nm; (iii) P 1 The micropore volume fraction based on the step is 0.43 to 0.85; (b) contacting the plurality of porous carbon particles with a gas containing 0.5 to 20 vol% silicon precursor gas at a temperature of 400 to 700°C to deposit silicon in the pores of the porous carbon particles; A method comprising:

51. 1. A method for preparing composite particles, comprising: (a) providing a plurality of porous carbon particles comprising micropores and / or mesopores; (i) The micropores and mesopores are determined by the total pore volume P measured by gas adsorption method. 1 cm 3 / g, where P 1 represents a number having a value between 0.5 and 1.5, (ii) PD 90 The pore diameter is at least 3 nm and less than 12 nm; (iii) P 1 The micropore volume fraction based on the step is 0.43 to 0.85; (b) contacting the plurality of porous carbon particles with a gas containing a silicon precursor gas at a temperature of 400 to 700°C to deposit silicon in the pores of the porous carbon particles, wherein the partial pressure of the silicon precursor gas is 0.5 to 20 kPa; A method comprising:

52. 52. The method of claim 50 or 51, wherein the composite particles are as defined in any one of claims 1 to 35.

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