Electroactive materials for metal-ion batteries

Abstract

The present invention relates to a particulate electroactive material composed of a plurality of composite particles, wherein the composite particles comprise: (a) a porous carbon framework comprising micropores and mesopores, wherein the total volume of the micropores and mesopores is 0.5 to 1.5 cm 3 and (b) a defined amount of silicon located at least within the micropores of the porous carbon framework relative to the volume of the micropores and mesopores, at least 20 weight percent of the silicon being characterized by thermogravimetric analysis as surface silicon.

Description

[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.

[0002] Rechargeable metal ion batteries are widely used in portable electronic devices, such as mobile phones and laptop computers, and are increasingly used in electric vehicles or hybrid vehicles. Rechargeable metal ion batteries generally include an anode in the form of a metal current collector having a layer of electroactive material, where the electroactive material is defined herein as a material that can insert and release metal ions during charging and discharging of the battery. The terms "cathode" and "anode" are used herein in the following sense: the battery is connected to a load so that the anode is the negative electrode. When the metal ion battery is charged, the metal ions are transported from the cathode layer containing the metal ions to the anode via the electrolyte and are inserted into the anode material. The term "battery" herein refers to both a device comprising a single anode and a single cathode and a device comprising multiple anodes and / or multiple cathodes.

[0003] It is of interest to improve the gravimetric and / or volumetric capacity of rechargeable metal ion batteries. To date, commercial lithium ion batteries have been largely limited by the use of graphite as the anode active material. When the graphite anode is charged, lithium is intercalated between the graphite layers to form a lithium ion battery with the empirical formula Li x C6 (where x is greater than 0 and less than or equal to 1). Consequently, the maximum theoretical capacity of graphite in lithium-ion batteries is 372 mAh / g, with actual capacities slightly 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 have not yet found widespread commercial use due to difficulties maintaining sufficient capacity over multiple charge / discharge cycles.

[0004] In particular, silicon is considered a promising graphite substitute for the production of rechargeable metal ion batteries with high gravimetric and volumetric capacities due to its very high lithium capacity (see, for example, Insertion Electrode Materials for Rechargeable Lithium Batteries, Winter, M et al., Adv. Mater. 1998, 10, No. 10). At room temperature, the theoretical maximum specific capacity of silicon in lithium ion batteries is about 3,600 mAh / g (based on Li 15Si4 is used as the basis). However, when silicon is lithiated to its maximum capacity, lithium is embedded in the bulk silicon, resulting in a large volume increase of the silicon material of up to 400% of its original volume. Repeated charge-discharge cycles cause significant mechanical stress in the silicon material, leading to the breakage and delamination of the silicon anode material. The volume shrinkage of the silicon particles during delithiation may lead to loss of electrical contact between the anode material and the current collector. Another difficulty is that the solid electrolyte interface (SEI) layer formed on the silicon surface does not have sufficient mechanical tolerance to accommodate the expansion and contraction of silicon. As a result, the newly exposed silicon surface leads to further electrolyte decomposition and increase in SEI layer thickness as well as irreversible lithium consumption. These destruction mechanisms together lead to unacceptable electrochemical capacity loss during continuous charge and discharge cycles.

[0005] Various approaches have been proposed to overcome the problems associated with the volume changes observed when silicon-containing anodes are charged. Fine silicon structures, such as silicon films and silicon nanoparticles, with cross-sections below approximately 150 nm have been reported to be more tolerant of volume changes during charge and discharge than silicon particles in the micrometer size range. However, none of these are suitable for commercial-scale applications in their unmodified form; nanometer-sized particles are difficult to prepare and handle, and silicon films do not provide sufficient bulk capacity.

[0006] WO 2007 / 083155 discloses that improved capacity retention can be achieved by using silicon particles with a high aspect ratio (i.e., the ratio of the largest dimension to the smallest dimension of the particle). The small cross-section of such particles reduces the structural stress on the material caused by volume changes during charge and discharge. However, such particles can be difficult and expensive to manufacture and can be fragile. In addition, the high surface area can lead to excessive SEI formation, resulting in excessive capacity loss during the first charge-discharge cycle.

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

[0008] JP 2003100284 discloses an active material comprising a carbon-based scaffold with small pores branching from some larger pores. Electroactive material (eg silicon) is randomly located on the walls of both the large and small pores, as well as on the outer surface of the carbon-based scaffold.

[0009] Silicon suboxide materials (such as SiO x , where 0<x<2) has been used for “hybrid” electrodes containing mainly graphite as active material. However, due to the x Due to the expansion upon lithiation and the relatively high irreversible lithium loss during the first charge cycle, SiO x The maximum loading of silicon oxide is generally about 10 wt % of the total electroactive material in the electrode. Therefore, there is a need for high capacity electrode materials that have comparable lithiation capacity to silicon oxides but with reduced expansion and reduced capacity loss during the first charge cycle.

[0010] The ideal expansion properties of electrode materials must be obtained together with other important properties. In particular, commercially available alternative electrode materials need to provide the benefits of high lithiation capacity and high capacity retention after a large number of charge-discharge cycles. In addition, it is important that any new electroactive material should be easily replaceable with known materials in conventional electrode manufacturing processes. These processes generally rely on rolling the electrode material onto the current collector to densify the electrode layer and improve the space utilization within the electrode design. Porous materials are prone to fracture during electrode manufacturing, resulting in impaired electrochemical performance. Therefore, it is particularly desirable that new electrochemical materials should have sufficient structural strength, as well as increased electrochemical storage capacity and reversible capacity retention. Summary of the Invention

[0011] The present inventors have determined that the properties of composite materials comprising silicon and porous carbon depend on the pore structure of the porous carbon framework as well as the amount of silicon and the manner in which it is distributed within the porous carbon framework. It has now been further determined that the properties of these composite materials depend on the location of the silicon, its characteristic length size and surface functionality.

[0012] In general, it is known that the atoms at the surface of a material have different binding interaction arrangements than the 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 infiltration (CVI), the free valences of the 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 not easily accessible to air remain in the form of hydride-terminated silicon.

[0013] It has been found that composite materials having a high proportion of hydride terminated surface silicon without a native oxide layer provide improved performance as electroactive materials.The amount of this hydride terminated surface silicon can be quantified using thermogravimetric analysis (TGA).

[0014] In a first aspect, the present invention provides a particulate material consisting of a plurality of composite particles, wherein the composite particles comprise:

[0015] (a) A porous carbon framework containing micropores and mesopores,

[0016] The total pore volume of the micropores and mesopores measured by gas adsorption is P 1 cm 3 / g, where P 1 Indicates a value between 0.5 and 1.5,

[0017] Among them PD 90 The pore size is at least 3 nm and less than 12 nm; and

[0018] Based on P 1 A micropore volume fraction of 0.43 to 0.85; and

[0019] (b) a plurality of nanometer-sized elemental silicon domains located within the pores of the porous carbon framework,

[0020] wherein the particulate material comprises from 25 wt% to 65 wt% silicon, and wherein at least 20 wt% of the silicon is surface silicon as determined by thermogravimetric analysis (TGA).

[0021] Due to this unique particle structure, the composite particles have the ability to improve the existing SiO x In particular, the particulate materials of the present invention have greater electrochemical capacity, lower overall expansion, and comparable reversible capacity retention, leading to the possibility of higher loadings of high-capacity electroactive materials than have been previously achieved.

[0022] The composite particles of the present invention have a structure in which a plurality of elemental nanosized silicon domains are located within the pore network of a porous carbon framework. As used herein, the term "nanosized silicon domains" refers to nanosized elemental silicon bodies having a defined maximum size by positioning silicon within the micropores and / or mesopores of a porous carbon framework.

[0023] Microporous carbon frameworks offer the following benefits: the electroactive material is localized within a microporous network as small domains, approximately a few nanometers in size. These fine electroactive structures have lower resistance to elastic deformation and higher fracture resistance than larger electroactive structures, enabling lithiation and delithiation without excessive structural stress. Consequently, the microporosity of the porous carbon framework ensures that the electroactive material itself possesses sufficient elasticity to withstand repeated volume changes over multiple charge and discharge cycles without significant capacity loss.

[0024] The granular material of the present invention is characterized in that the unoxidized surface silicon content is high as determined by TGA analysis. This analytical method relies on the following principle: when silicon is in air and oxidized to silicon dioxide (SiO2) at high temperatures, a weight increase is observed. The mechanism of silicon oxidation depends on temperature. Compared to silicon atoms in the bulk phase of silicon nanostructures, silicon atoms on the surface of silicon nanostructures are oxidized at lower temperatures (reference: Bardet et al., PHys.Chem.Chem.Phys. (2016), 18, 18201). TGA analysis enables the relative content of surface silicon to be quantified based on the weight increase observed when silicon is in air and oxidized to silicon dioxide (SiO2) at high temperatures. By plotting the weight increase versus temperature, the bulk silicon and surface silicon in the sample can be distinguished and quantified.

[0025] Figure 1 A TGA trace of a particulate material according to the present invention comprising high surface silicon levels and low bulk coarse silicon levels is shown.

[0026] Figure 2 A TGA trace is shown for a granular material comprising low surface silicon levels and high bulk coarse silicon levels.

[0027] like Figure 1 and 2 The amount of unoxidized surface silicon was determined from the characteristic TGA traces of these materials as shown. The initial mass loss upon reaching about 300°C (at Figure 1 and 2 After that, a significant mass increase starting at about 400 °C and peaking between 550 °C and 650 °C is observed (shown as a mass decrease from (a) to (b) in FIG). Figure 1 and 2The weight gain from (b) to (c) is shown in the figure. A mass decrease is then observed as the porous carbon framework is oxidized to CO₂ gas (mass decrease from (c)), followed by another mass increase above approximately 800°C corresponding to the continued conversion of silicon to SiO₂, which increases toward an asymptotic value above 1000°C where silicon oxidation is complete (mass increase from (d) to (e)). The temperature at which this weight gain occurs is related to the structure of the silicon, with surface silicon oxidizing at low temperatures and bulk silicon oxidizing at higher temperatures. Therefore, the coarser the silicon domains, the more oxidation is observed at higher temperatures.

[0028] Any native oxide that has formed on the silicon surface exposed to air does not affect the TGA analysis because already oxidized silicon does not result in an increase in mass in the TGA analysis. Therefore, the more silicon surface that is available to react with air to form native oxide, the less surface silicon is observed by TGA. For the avoidance of doubt, the calculation of "surface silicon" therefore only considers the silicon that is not oxidized at the start of the TGA analysis after the material has been passivated by air or other surface passivating agents as described herein (i.e., the particulate material is not kept under any special inert conditions prior to the TGA analysis).

[0029] As defined herein, "surface silicon" is determined by the initial mass increase in a TGA trace from a minimum value between 150°C and 500°C to a maximum mass measured in the temperature range of 550°C to 650°C, wherein the TGA is performed in air at a heating rate of 10°C / min. This mass increase is believed to be due to oxidation of the surface silicon, thus enabling the determination of the percentage of surface silicon as a proportion of the total amount of silicon according to the following formula:

[0030] Y=1.875×[(M max -M min ) / M f ]×100%

[0031] where Y is the percentage of surface silicon as a proportion of the total silicon in the sample, M max is the maximum mass of the sample measured in the temperature range of 550℃ to 650℃ ( Figure 1 and 2 The mass in (c)), M min is the minimum mass of the sample above 150℃ and below 500℃ ( Figure 1 and 2 The mass in (b)), and M f is the mass of the sample when oxidation is completed at 1400℃ ( Figure 1 and 2For completeness, it should be understood that 1.875 is the molar mass ratio of SiO2 to O2 (i.e., the mass ratio of SiO2 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.

[0032] It has been found that when surface silicon, as determined by the above-mentioned TGA method, is at least 20 wt % of the total amount of silicon in the material, the reversible capacity retention after multiple charge / discharge cycles is significantly improved. Preferably, at least 22 wt %, or at least 25 wt %, at least 30 wt % of the silicon, or at least 35 wt % of the silicon, or at least 40 wt % of the silicon, or at least 45 wt % of the silicon is surface silicon, as determined by thermogravimetric analysis (TGA).

[0033] Optionally, the amount of surface silicon measured by TGA is at most 80% by weight of the total amount of silicon in the granular material, or at most 75% by weight, or at most 70% by weight, or at most 65% by weight, or at most 60% by weight, or at most 55% by weight. For example, the amount of surface silicon measured by TGA can be 20% to 80% by weight, or 22% to 75% by weight, or 25% to 70% by weight, or 30% to 65% by weight, or 35% to 60% by weight, or 40% to 55% by weight of the total amount of silicon in the granular material. The amount of surface silicon measured by TGA can also be in the range of 20% to 55% by weight, or 22% to 60% by weight, or 25% to 65% by weight, or 30% to 70% by weight, or 35% to 75% by weight, or 40% to 80% by weight of the total amount of silicon in the granular material. Additional preferred ranges can be defined by combining the upper and lower limits of any of the aforementioned ranges.

[0034] The fact that a significant proportion of hydride-terminated surface silicon can be measured in the granular material even after passivation in air suggests that the composite particles contain internal silicon surfaces that are inaccessible to air. This suggests that the internal pore spaces of the porous carbon framework are first lined with silicon and then capped to form internal void spaces, with the hydride-terminated silicon surfaces oriented into the enclosed internal void spaces. This, in turn, suggests that the silicon domains have a characteristic length dimension much smaller than the pores themselves.

[0035] 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. Additional exposure of the electroactive material during subsequent charge-discharge cycles is also largely prevented, so that SEI formation is not a significant failure mechanism leading to capacity loss. At the same time, the silicon is hydrostatically constrained during lithiation, enabling the use of voids during lithiation-induced expansion.

[0036] The porous carbon framework comprises a three-dimensional interconnected open pore network including micropores and mesopores. The porous carbon framework may optionally also include a small volume of macropores. According to conventional IUPAC terminology, the term "micropore" is used herein to refer to pores with a diameter less than 2 nm, the term "mesopore" is used herein to refer to pores with a diameter of 2-50 nm, and the term "macroporous" is used to refer to pores with a diameter greater than 50 nm.

[0037] It has been found that the high surface silicon levels required by the present invention can only be obtained when the pore structure of the porous carbon framework is controlled within the specific ranges as defined above. References herein to the volumes of micropores, mesopores and macropores in the porous carbon framework and any reference to the distribution of pore volume within the porous carbon framework refer to the internal pore volume of the porous carbon framework alone (i.e. in the absence of any electroactive material or other material occupying some or all of the pore volume).

[0038] The total volume of micropores and mesopores (i.e., the total pore volume of pores with diameters in the range of 0 to 50 nm) is referred to herein as P 1 cm 3 / g, where P 1 represents a dimensionless number with a value between 0.5 and 1.5. For the avoidance of doubt, references herein to the pore volume of a porous carbon framework (in the absence of any indication to the contrary) relate to the pore volume of the porous carbon framework alone, i.e., the pore volume of the porous carbon framework measured in the absence of any electroactive material (or any other material) occupying the pores of the porous carbon framework.

[0039] P 1 The value of is preferably at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75. A higher porosity framework is advantageous because it enables a larger amount of silicon to be accommodated within the pore structure without compromising the porous carbon framework's resistance to cracking under compressive stress during electrode fabrication or under expansion stress due to lithiation of silicon. However, if P 1 Too high, and it is not possible to achieve the elevated surface silicon level that is a feature of the present invention. 1 The value of is preferably not more than 1.5, or not more than 1.4, or not more than 1.3, or not more than 1.2, or not more than 1.1, or not more than 1, or not more than 0.95.

[0040] For example, P 1 It can be in the range of 0.55 to 1.4, or 0.6 to 1.4, or 0.6 to 1.3, or 0.65 to 1.3, or 0.65 to 1.2, or 0.7 to 1.2, or 0.7 to 1.1, or 0.7 to 1, or 0.75 to 0.95.

[0041] The standard method described in ISO 15901-2 and ISO 15901-3 was used to determine the concentration of the ions at 77 K down to 10 -6 The relative pressure p / p0 of quenched solid density functional theory (QSDFT) is used to determine the total volume of micropores and mesopores and the pore size distribution of micropores and mesopores. Nitrogen adsorption is a technique for characterizing the porosity and pore size distribution of a material by condensing a gas in the pores of a solid. As the pressure increases, the gas first condenses in the pores with the smallest diameter, and the pressure increases until a saturation point is reached, at which all pores are filled with liquid. The nitrogen pressure is then gradually reduced to evaporate the liquid from the system. Analysis of the adsorption and desorption isotherms and the hysteresis between them enables the determination of pore volume and pore size distribution. Suitable instruments for measuring pore volume and pore size distribution by nitrogen adsorption include TriStar II and TriStar II Plus porosity analyzers (which can be obtained from Micromeritics Instrument Corporation in the United States), and Autosorb IQ porosity analyzer (which can be obtained from Quantachrome Instruments).

[0042] Nitrogen adsorption is effective for measuring the pore volume and pore size distribution of pores with a diameter of up to 50 nm, but is less reliable for pores with much larger diameters. For the purposes of the present invention, therefore, nitrogen adsorption is used only for pores with a diameter of up to 50 nm (inclusive) to determine the pore volume and pore size distribution. As described above, P 1 The value of is determined by considering only pores with diameters up to and including 50 nm (ie only micropores and mesopores).

[0043] The general term "PD n The term "pore size" as used herein refers to the volume nth percentile pore size based on the total volume of micropores and mesopores. For example, as used herein, the term "PD 90 The pore size is the total volume of micropores and mesopores (measured by P 1 The pore diameter is the pore diameter at which 90% of the pore diameters are lower than a certain pore diameter.

[0044] As mentioned above, the PD of the porous carbon framework 90 The pore size is at least 3 nm and less than 12 nm. It has been found that if the PD 90 If the value is too low, it is impossible to deposit silicon into the micropores, and silicon is instead deposited on the outer surface of the porous carbon framework. However, if PD 90 If the value is too high, there is excessive coarse silicon deposits and / or excessive native oxide formation leading to a low surface silicon content.

[0045] PD of porous carbon framework90 The pore size is preferably no more than 10 nm, or no more than 8 nm, or no more than 6 nm. 90 The pore size is at least 3.2 nm, or at least 3.5 nm, or at least 3.8 nm, or at least 4 nm. For example, the PD of the porous carbon framework 90 The pore diameter is preferably in the range of 3.5 to 10 nm, or 3.8 to 8 nm, or 4 to 6 nm.

[0046] PD of porous carbon framework 75 The pore size is preferably no more than 10 nm, or no more than 8 nm, or no more than 6 nm, or no more than 4 nm. 75 The pore diameter is preferably at least 1 nm.

[0047] PD of porous carbon framework 50 The pore size is preferably no more than 2 nm, or no more than 1.9 nm, or no more than 1.8 nm, or no more than 1.7 nm, or no more than 1.6 nm. 50 The pore size is at least 1 nm, or at least 1.1 nm, or at least 1.2 nm. For example, the PD of the porous carbon framework s0 The pore size is preferably in the range of 1 to 2 nm, or 1 to 1.9 nm, or 1.1 to 1.8 nm, or 1.1 to 1.7 nm, or 1.2 to 1.6 nm.

[0048] PD of porous carbon framework 30 The pore size is preferably no more than 1.6 nm, or no more than 1.5 nm, or no more than 1.4 nm, or no more than 1.3 nm, or no more than 1.2 nm, or no more than 1.1 nm, or no more than 1 nm. 30 The pore diameter is at least 0.6 nm, or at least 0.7 nm.

[0049] PD 90 Aperture and PD 30 The ratio of the pore sizes is preferably not more than 14, or not more than 12, or not more than 10, or not more than 8.

[0050] PD 90 Aperture and PD 10 The ratio of the pore sizes is preferably not more than 11, or not more than 10, or not more than 9, or not more than 8, or not more than 7.

[0051] As used herein, the micropore volume fraction refers to the volume of micropores expressed as a fraction of the total volume of micropores and mesopores, represented by P 1In 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 50 nm or less. As discussed above, the micropore volume fraction of the porous framework is selected within the range of 0.43 to 0.85 to achieve the desired high level of surface silicon content in the composite particles.

[0052] Preferably, the micropore volume fraction is at least 0.45, or at least 0.48, or at least 0.5, or at least 0.51, or at least 0.52, or at least 0.54, or at least 0.56, or 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, or no more than 0.79, or no more than 0.78, or no more than 0.76, or no more than 0.74, or no more than 0.72, or no more than 0.7, based on the total volume of micropores and mesopores.

[0053] The micropore volume fraction may optionally be in the range of 0.45 to 0.85, or 0.5 to 0.8, or 0.45 to 0.78, or 0.48 to 0.8, or 0.48 to 0.78, or 0.48 to 0.76, or 0.5 to 0.8, or 0.5 to 0.78, or 0.5 to 0.76, or 0.5 to 0.74, or 0.5 to 0.8, based on the total volume of the micropores and mesopores. 0.72, or 0.5 to 0.7, or 0.51 to 0.76, or 0.52 to 0.74, or 0.53 to 0.74, or 0.54 to 0.72, or 0.6 to less than 0.8, or 0.6 to 0.79, or 0.6 to 0.78, or 0.6 to 0.76, or 0.6 to 0.74, or 0.6 to 0.72, or 0.6 to 0.7.

[0054] The total volume of the micropores in the porous carbon framework (measured at 77 K using nitrogen adsorption as described herein) is preferably at least 0.36 cm 3 / g, or at least 0.38cm 3 / g, at least 0.40cm 3 / g, at least 0.42cm 3 Because the silicon located in the micropores has a smaller length dimension, a higher total micropore volume allows a higher proportion of surface silicon to be accommodated within the porous carbon framework, thereby allowing for higher gravimetric and volumetric capacities of the composite particles.

[0055] Any pore volume in the mesopore range is preferably substantially within the smaller mesopore range. Thus, the volume fraction of pores with a pore size of 5 nm or less is preferably at least 0.8, or at least 0.82, or at least 0.84, or at least 0.86, or at least 0.88, or at least 0.9, based on the total volume of micropores and mesopores. Preferably, the volume fraction of pores with a pore size of 10 nm or less is preferably at least 0.9, or at least 0.92, or at least 0.94, or at least 0.96, based on the total volume of micropores and mesopores. Preferably, the volume fraction of pores with a pore size of 20 nm or less is preferably at least 0.94, or at least 0.96, or at least 0.98, based on the total volume of micropores and mesopores.

[0056] A small fraction of pores with diameters in the larger mesopore range can advantageously facilitate access of the electrolyte to the silicon domains. Thus, pores with diameters in the range of 10 to 50 nm (i.e., larger mesopores) can optionally account for no more than 2%, or no more than 4%, or no more than 6% of the total micropore and mesopore volume of the porous carbon framework.

[0057] The pore size distribution of the porous carbon framework is preferably bimodal or multimodal. As used herein, the term "pore size distribution" refers to the distribution of pore sizes of the porous carbon framework relative to the cumulative total internal pore volume. A bimodal or multimodal pore size distribution may be preferred because the close proximity between micropores and pores with larger diameters provides the advantage of efficient ion transport from the porous network to the silicon. As a result, the particulate material has high ion diffusivity and, therefore, improved rate performance.

[0058] Given the limitations of available analytical techniques, it is not possible to measure the pore volume and pore size distribution over the entire range of micropores, mesopores, and macropores using a single technique. In the case of porous carbon frameworks that include macropores, the volume of pores in the range of greater than 50 nm to a maximum of 100 nm is considered herein to have a P value of 0. 2 cm 3 / g value, and is measured by mercury intrusion porosimetry. As mentioned above, P 2 The value of relates to the pore volume of the porous carbon framework when measured alone, ie in the absence of silicon or any other material occupying the pores of the porous carbon framework.

[0059] For the avoidance of doubt, P 2 The value of takes into account only pores with diameters from greater than 50 nm up to and including 100 nm, i.e. it includes only the volume of macropores with a diameter of at most 100 nm. 2The value of P is not taken into account for any pore volume below 50 nm as measured by mercury intrusion (as described above, nitrogen adsorption is used to characterize mesopores and micropores). For the purposes of this invention, the pore volume above 100 nm as measured by mercury intrusion is assumed to be the interparticle porosity and is not used in determining P. 2 The value of is not considered.

[0060] Mercury porosimetry (also known as mercury intrusion porosimetry) is a technique for characterizing the porosity and pore size 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. The values ​​reported herein obtained by mercury intrusion porosimetry were obtained according to ASTM UOP578-11, where for mercury at room temperature, the surface tension γ is 480 mN / m and the contact angle is The density of mercury at room temperature is 13.5462 g / cm 3 A variety of high-precision mercury porosimetry instruments are commercially available, such as the AutoPore IV series of automated mercury porosimeter, available from Micromeritics Instrument Corporation in the United States. For a complete overview of mercury porosimetry, reference can be made to P.A. Webb and C. Orr, "Analytical Methods in Fine Particle Technology," 1997, Micromeritics Instrument Corporation, ISBN 0-9656783-0.

[0061] and the volume of micropores and mesopores (and hence P 1 The volume of the macropores (and therefore P 2 Although a small number of macropores may be useful in promoting the entry of electrolyte into the pore network, the advantages of the present invention are essentially obtained by accommodating silicon in micropores and smaller mesopores.

[0062] Therefore, according to the present invention, the total volume of the macropores in the porous carbon framework measured by mercury intrusion porosimetry is P 2 cm 3 / g, where P 2 The value of is preferably at most 0.2×P 1 , or at most 0.1×P 1 , or at most 0.05×P 1 , or at most 0.02×P 1 , or at most 0.01×P 1 , or at most 0.005×P 1 .

[0063] It should be understood that intrusion techniques such as gas adsorption and mercury intrusion are only effective for determining the pore volume of pores accessible to nitrogen or mercury from outside the porous carbon framework. The porosity values ​​(P) as specified herein are 1 and P 2 ) should be understood to refer to the volume of open pores (i.e., pores accessible to fluids from outside the porous carbon framework). In this context, when specifying porosity values, completely enclosed pores that cannot be identified by nitrogen adsorption or mercury intrusion should not be taken into account. Similarly, for determining P 1 The value of ∝₄ does not take into account any pore volume located in pores so small that it is below the detection limit for nitrogen adsorption.

[0064] The BET surface area of ​​the porous carbon framework is preferably from 1200 to 3000 m 2 Preferably, the BET surface area of ​​the porous carbon skeleton is at least 1500 m 2 / g, or at least 1700m 2 / g. Preferably, the BET surface area of ​​the porous carbon skeleton does not exceed 2500m 2 / g, or not more than 2000m 2 The term "BET surface area" as used herein should be taken to mean the surface area per unit mass calculated from the measurement of the physical adsorption of gas molecules on a solid surface using the Brunauer-Emmett-Teller principle in accordance with ISO 9277.

[0065] The porous carbon skeleton can include crystalline carbon or amorphous carbon, or a mixture of amorphous carbon and crystalline carbon. The porous carbon skeleton can be a hard carbon or a soft carbon skeleton, and can be suitably obtained by known procedures involving the pyrolysis of carbonaceous materials (including organic materials, resins and polymers). Porous carbon materials can also be obtained by other methods, such as by obtaining from a precursor containing a carbide. Highly porous carbon materials are commercially available and are generally referred to as activated carbon.

[0066] 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 can be determined by conventional elemental analysis techniques performed in the absence of silicon.

[0067] As used herein, the term "hard carbon" refers to carbon atoms found primarily as sp in nanoscale polyaromatic domains. 2 The disordered carbon matrix is ​​in a hybrid state (triple bond). The polyaromatic hydrocarbon domains are cross-linked using chemical bonds such as C-O-C bonds.

[0068] Due to the chemical cross-linking between the polyaromatic domains, hard carbon cannot be converted into graphite at high temperatures. Hard carbon has graphite-like properties, which is reflected by the large G band (~1600 cm) in the Raman spectrum. -1 However, the carbon is not completely graphitic, as evidenced by the distinct D band (~1350 cm -1 ) proved.

[0069] As used herein, the term "soft carbon" also refers to polyaromatic hydrocarbons in which carbon atoms are found primarily in sp domains with sizes ranging from 5 to 200 nm. 2 A disordered carbon matrix in a hybrid state (triple bonds). Compared to hard carbon, the polyaromatic domains in soft carbon are associated by intermolecular forces rather than cross-linked by chemical bonds. This means that they will graphitize at high temperatures. The porous carbon skeleton preferably contains at least 50% sp 2 Hybridized carbon (measured by XPS). For example, the porous carbon framework may suitably comprise 50% to 98% sp 2 Hybridized carbon, 55% to 95% sp 2 Hybridized carbon, 60% to 90% sp 2 Hybridized carbon, or 70% to 85% sp 2 Hybridized carbon.

[0070] A wide variety of different materials can 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, wood, etc.), 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, asphalt, melamine, polyacrylates, polystyrene, polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), and various copolymers containing monomer units of acrylates, styrene, α-olefins, vinyl pyrrolidone and other ethylenically unsaturated monomers. A wide variety of hard carbon materials are available in the art, depending on the raw materials and conditions of the pyrolysis process.

[0071] The porous carbon framework can be subjected to a chemical or gas activation process to increase the volume of the mesopores and micropores. Suitable activation processes include contacting pyrolytic carbon with one or more of oxygen, water vapor, CO, CO2, and KOH at a temperature in the range of 600 to 1000°C. Preferably, the porous carbon framework is a steam-activated porous carbon framework.

[0072] Mesopores can also be obtained by known templating processes using removable pore formers such as MgO and other colloidal or polymeric templates that can be removed by thermal or chemical means after pyrolysis or activation.

[0073] The elemental composition in 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. Optionally, the amounts of hydrogen, nitrogen, and oxygen can also be determined by elemental analysis. Preferably, elemental analysis is also used to determine the weight percent of carbon (and optional hydrogen, nitrogen, and oxygen) in a separate porous carbon skeleton. Determining the weight percent of carbon in a separate porous carbon skeleton takes into account the possibility that the porous carbon skeleton contains a small amount of heteroatoms within its molecular skeleton. The two measurements performed together enable reliable determination of the weight percent of silicon relative to the entire porous carbon skeleton.

[0074] The silicon content is preferably determined by ICP-OES (Inductively Coupled Plasma-Optical Emission Spectroscopy). A variety of ICP-OES instruments are commercially available, such as The carbon content (and, if desired, the hydrogen content, nitrogen content, and oxygen content) of the composite particles and the individual porous carbon frameworks is preferably determined by combustion and infrared (IR) absorption techniques. Suitable instruments for determining the carbon content, hydrogen content, nitrogen content, and oxygen content are Micro Elemental Analyzer (available from LECO Corporation).

[0075] The granular material of the present invention contains from 25% to 65% silicon by weight, as determined by elemental analysis, and preferably from 30% to 65% silicon by weight. Preferably, the granular material of the present invention contains at least 26%, or at least 28%, or at least 30%, or at least 32%, or at least 34%, or at least 36%, or at least 38%, or at least 40%, or at least 42%, or at least 44% silicon by weight. Preferably, the granular material of the present invention contains no more than 60%, or no more than 58%, or no more than 56%, or no more than 54%, or no more than 52%, or no more than 50% silicon by weight.

[0076] For example, the particulate material of the invention may contain 26% to 65% by weight, or 28% to 65% by weight, or 30% to 65% by weight, or 32% to 60% by weight, or 34% to 60% by weight, or 36% to 60% by weight, or 38% to 58% by weight, or 40% to 58% by weight, or 42% to 56% by weight, or 44% to 54% by weight silicon.

[0077] A minimum amount of silicon is required to ensure that the particulate material has sufficient volume capacity for commercial use. However, excess silicon causes silicon to be deposited in larger pores and / or on the surface of the porous carbon framework, resulting in low surface silicon content and poor performance as an electroactive material.

[0078] The amount of silicon in the composite particles of the present invention is selected so that at least about 20% and at most about 78% of the internal pore volume (based on micropores and mesopores) of the porous carbon framework is occupied by silicon (in the uncharged state). Generally, the higher the micropore fraction of the porous carbon framework, the higher the amount of silicon that can be used without reducing the proportion of surface silicon.

[0079] Preferably, silicon occupies about 20% to about 78% of the internal pore volume of the porous carbon framework, for example, about 23% to 75%, or about 26% to 72%, or about 28% to 70%, or about 30% to 70%, or about 35% to 68%, or about 40% to 65%, or about 45% to 60% of the internal pore volume of the porous carbon framework. Within these preferred ranges, the pore volume of the porous carbon framework effectively accommodates the expansion of silicon during charge and discharge, but avoids excessive pore volume that is detrimental to the volumetric capacity of the particulate material. However, the amount of silicon is not so high as to hinder efficient lithiation due to insufficient metal ion diffusion rate or mechanical resistance to lithiation due to insufficient expansion volume.

[0080] By requiring the weight ratio of silicon to porous carbon framework to be between [0.50×P 1 to 1.9×P 1 The amount of silicon in the porous carbon framework can be related to the available pore volume in the range of [0.7×P]:1. This relationship takes into account the density of silicon and the pore volume of the porous carbon framework to define the weight ratio of silicon, and it is estimated that the occupied pore volume at the weight ratio is about 20% to 78%. Preferably, the weight ratio of silicon to the porous carbon framework is in the range of [0.7×P]:1. 1 to 1.8×P 1 ]∶1, which indicates that the occupied pore volume is about 30% to 78%.

[0081] Preferably, the weight ratio of silicon to porous carbon framework is at least 0.50×P 1 , or at least 0.55×P 1 , or at least 0.6×P 1 , or at least 0.65×P 1 , or at least 0.7×P 1 , or at least 0.75×P 1 , or at least 0.8×P 1 , or at least 0.85×P 1 , or at least 0.9×P 1 , or at least 0.95×P 1 , or at least 1×P1 Preferably, the weight ratio of silicon to porous carbon framework does not exceed 1.85×P 1 , or not more than 1.8×P 1 , or not more than 1.75×P 1 , or not more than 1.7×P 1 , or not more than 1.65×P 1 , or not more than 1.6×P 1 , or not more than 1.55×P 1 , or not more than 1.5×P 1 .

[0082] The composite particles preferably have a low total oxygen content (determined 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 any 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, such as less than 4% by weight, or less than 3% by weight, or less than 2% by weight, or less than 1% by weight, or less than 0.5% by weight. Preferably, silicon and carbon together comprise at least 90% by weight of the composite particles, more preferably at least 95% by weight of the composite particles.

[0083] The silicon may optionally contain a small amount of one or more dopants. Suitable dopants include boron and phosphorus, other n-type or p-type dopants, nitrogen or germanium. Preferably, the dopant is present in a total amount of no more than 2% by weight based on the total amount of silicon and the one or more dopants.

[0084] In addition to the surface silicon content, the particulate material of the present invention preferably has a low bulk silicon content as measured by TGA. Bulk silicon is defined herein as silicon that oxidizes above 800°C as measured by TGA conducted in air at a heating rate of 10°C / min. Figure 1 and 2 The mass increase from (d) to (e) is shown in FIG. Therefore, the silicon content of the coarse phase is determined according to the following formula:

[0085] Z=1.875×[(M f -M 800 ) / M f ]×100%

[0086] Where Z is the percentage of silicon that is not oxidized at 800°C, M 800 is the mass of the sample at 800℃ ( Figure 1 and 2 The mass in (d)), and M f is the mass of ash when oxidation is completed at 1400℃ ( Figure 1 and 2For the purposes of this analysis, it is assumed that any mass increase above 800°C corresponds to oxidation of silicon to SiO2, and that the total mass at completion of oxidation is SiO2.

[0087] Preferably, no more than 10 wt%, or no more than 8 wt%, or no more than 6 wt%, or no more than 5 wt%, or no more than 4 wt%, or no more than 3 wt%, or no more than 2 wt%, or no more than 1.5 wt% of the silicon is macrophase silicon as determined by TGA.

[0088] Preferably, at least 30 wt% of the silicon (e.g., 30 to 75 wt%, 30 to 70 wt%, or 30 to 65 wt% of silicon) is surface silicon and no more than 10 wt% of the silicon is gross phase silicon, both as determined by TGA. More preferably, at least 35 wt% of the silicon (e.g., 35 to 70 wt%, 35 to 65 wt%, or 35 to 60 wt% of silicon) is surface silicon and no more than 8 wt% of the silicon is gross phase silicon, both as determined by TGA. More preferably, at least 40 wt% of the silicon (e.g., 40 to 65 wt%, 40 to 60 wt%, or 40 to 55 wt% of silicon) is surface silicon and no more than 5 wt% of the silicon is gross phase silicon, both as determined by TGA. More preferably, at least 45 wt% of the silicon is surface silicon and no more than 2 wt% of the silicon is bulk phase silicon, both as determined by TGA.

[0089] Preferably, the total volume of micropores and mesopores in the composite particles (ie in the presence of silicon) as measured by nitrogen adsorption is at most 0.15 x P 1 , or at most 0.10×P 1 , or at most 0.05×P 1 , or at most 0.02×P 1 .

[0090] Preferably, the total volume of micropores and mesopores in the composite particles, as measured by nitrogen adsorption, is less than 0.2 cm 3 / g, preferably less than 0.15cm 3 / g, or less than 0.1cm 3 / g, or less than 0.08cm 3 / g, or less than 0.06cm 3 / g, or less than 0.04cm 3 / g, or less than 0.02cm 3 / g, or less than 0.015cm 3 / g, or less than 0.012cm 3 / g, or less than 0.010cm 3 / g, or less than 0.008cm3 / g.

[0091] As used herein, the term "particle size" refers to the equivalent spherical diameter (esd), which is the diameter of a sphere having the same volume as a given particle, wherein the particle volume is understood to include the volume of any intraparticle pores. As used herein, the term "D 50 ” and “D 50 The term "D" as used herein refers to the volume median particle size, i.e., the diameter below which 50% of the volume of the particle population is measured. 10 ” and “D 10 The term "D" as used herein refers to the 10th percentile volume median particle size, i.e., the diameter below which 10% of the volume of the particle population is measured. 90 ” and “D 90 The term "particle size" refers to the 90th percentile volume median particle size, i.e., the diameter below which 90% of the volume of the particle population is measured.

[0092] The term "D" used herein to define particle size distribution should be n ” is used in this document to define the pore size distribution as described above. n ” to distinguish.

[0093] Particle size and particle size distribution can be determined by conventional laser diffraction techniques according to ISO 13320: 2009. Unless otherwise stated, particle size distribution measurements indicated or reported herein are made by a conventional Malvern Mastersizer from Malvern Instruments. TM Measured by Malvern Mastersizer 3000 particle size analyzer. TM The 3000 particle size analyzer operates by projecting a helium-neon gas laser beam through a transparent cell containing particles of interest suspended in an aqueous solution. The light impinging on the particles is scattered through angles inversely proportional to the particle size, and an array of photodetectors measures the intensity of the light at a number of predetermined angles. The intensities measured at different angles are processed by a computer using standard theoretical principles to determine the particle size distribution. The laser diffraction values ​​reported herein were obtained using a solution containing 5% by volume of the surfactant SPAN. TM A wet dispersion of particles in 2-propanol was obtained using a sorbitan monopalmitate-40 (sorbitan monopalmitate). The refractive index of the porous carbon framework particles was found to be 2.68, the refractive index of the composite particles was found to be 3.50, and the refractive index of the dispersant was found to be 1.378. The particle size distribution was calculated using the Mie scattering model.

[0094] D of composite particles 50The particle size may be in the range of 1 to 30 μm. Optionally, D 50 The particle size may be at least 1 μm, or at least 2 μm, or at least 3 μm, or at least 4 μm, or at least 5 μm. Optionally, D 50 The particle size may be no greater than 20 μm, or no greater than 18 μm, or no greater than 16 μm, or no greater than 14 μm, or no greater than 12 μm, or no greater than 10 μm, or no greater than 8 μm.

[0095] For example, the D of a composite particle 50 The particle size may be in the range of 1 to 20 μm, or in the range of 1 to 18 μm, or in the range of 1 to 16 μm, or in the range of 2 to 16 μm, or in the range of 2 to 14 μm, or in the range of 2 to 12 μm, or in the range of 2 to 10 μm, or in the range of 2 to 8 μm. Particles within these size ranges and having the porosity and pore size distribution described herein are ideally suited for use in anodes of metal ion batteries due to their dispersibility in slurries, their structural robustness, their capacity retention after repeated charge-discharge cycles, and their suitability for forming dense electrode layers having a uniform thickness in the conventional range of 20 to 50 μm.

[0096] D of composite particles 10 The particle size is preferably at least 0.5 μm, or at least 0.8 μm, or at least 1 μm. 10 The particle size is maintained above 0.5 μm, reducing the possibility of undesirable agglomeration of submicron-sized particles, resulting in improved dispersion of the particulate material and improved capacity retention.

[0097] D of composite particles 90 The particle size is preferably not more than 50 μm, or not more than 40 μm, or not more than 30 μm, or not more than 25 μm, or not more than 20 μm, or not more than 15 μm. The presence of very large particles leads to uneven filling of particles in the electrode active layer, thereby disrupting the formation of a dense electrode layer, especially an electrode layer with a thickness in the range of 20 to 50 μm. Therefore, it is preferred that D 90 The particle size is at most 40 μm, and more preferably even smaller.

[0098] The composite particles preferably have a narrow size distribution span. For example, the particle size distribution span (defined as (D 90 -D 10 ) / D 50 ) is preferably 5 or less, more preferably 4 or less, more preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. By maintaining a narrow size distribution span, it is easier to effectively fill the particles into a dense electrode layer.

[0099] The composite particles preferably have a positive skew in the volume-based distribution, e.g., such that the volume-based distribution is asymmetric with a longer tail on the right-hand side. A positive skew in the volume-based particle size distribution is advantageous because it provides a denser electrode since the natural filling factor will be higher than if all particles were the same size, thereby reducing the need for calendaring or other physical densification processes. Preferably, D 50 The composite particle size diameter is smaller than the volume mean value (D[4.3]) of the particle size distribution. Preferably, the skewness of the composite particle size distribution (by Malvern Mastersizer TM 3000 analyzer measurement) does not exceed 5, or does not exceed 3.

[0100] The average sphericity (as defined herein) of the composite particles may be at least 0.5, or at least 0.55. Preferably, the average sphericity is at least 0.65, or at least 0.7, or at least 0.75, or at least 0.8.

[0101] Highly accurate two-dimensional projections of micrometer-scale particles can be obtained by scanning electron microscopy (SEM) or by dynamic image analysis, where a digital camera is used to record the shadows cast by the particles. The term "sphericity" as used herein is understood to be the ratio of the area of ​​the particle's projection (obtained by such imaging techniques) to the area of ​​a circle, where the particle projection and the circle have the same circumference. Thus, for an individual particle, sphericity S can be defined as:

[0102]

[0103] Among them A m is the measured area of ​​the particle projection, and C m is the measured circumference of the particle projection. As used herein, the average sphericity S of a plurality of particles av is defined as:

[0104]

[0105] wherein n represents the number of particles in the population. The average sphericity of a population of particles is preferably calculated from the two-dimensional projections of at least 50 particles.

[0106] The BET surface area of ​​the composite particles of the present invention is preferably not more than 200 m 2 / g. Preferably, the BET surface area of ​​the composite particles does not exceed 150m 2 / g, or not more than 100m 2 / g, or no more than 80m 2 / g, or no more than 60m 2 / g, or no more than 50m 2 / g, or no more than 40m 2 / g, or no more than 30m 2 / g, or no more than 25m 2 / g, or no more than 20m 2 / g, or not more than 15m 2 / g, or not more than 10m 2 / g.

[0107] Generally, a low BET surface area is preferred to minimize the formation of a solid electrolyte interface (SEI) layer at the surface of the composite particles during the first charge-discharge cycle of an anode comprising the particulate material of the present invention. However, too low a BET surface area leads to unacceptably low charge rates and capacity limitations due to the inaccessibility of the bulk of the electroactive material to the metal ions in the surrounding electrolyte. For example, the BET surface area is preferably at least 0.1 m 2 / g, or at least 1m 2 / g, or at least 2m 2 / g, or at least 5m 2 / g. For example, the BET surface area can be 2 / g to 25m 2 / g, more preferably in the range of 2 to 15 m 2 / g range.

[0108] The particle material of the present invention generally has a charge capacity of 900 to 2300 mAh / g upon initial lithiation. Preferably, the particle material of the present invention has a charge capacity of at least 1200 mAh / g, or at least 1400 mAh / g upon initial lithiation.

[0109] The particulate material of the present invention may optionally include a silicon surface that has been treated with a passivating agent. As discussed in more detail below, a passivating agent is defined herein as a compound capable of modifying the surface of an electroactive material so as to inhibit or prevent the formation of surface oxides.

[0110] The composite particles of the present invention may optionally include a coating that at least partially or completely covers the outer surface of the particle. The coating is preferably a lithium ion permeable coating. As used herein, the term "lithium ion permeable" refers to an ion conducting material that enables lithium ions to be transported from the exterior of the composite particle to the nano-sized electroactive material domains. Preferably, the lithium ion permeable coating is impermeable to liquids such as solvents of liquid electrolytes. Preferably, the lithium ion permeable filler material is impermeable to lithium ions at a voltage < 0.1 V (vs. Li / Li + ) is electrochemically stable.

[0111] Optionally, the coating may include a conductive carbon coating. Suitably, the conductive carbon coating may be obtained by chemical vapor deposition (CVD). CVD is a method well known in the art and includes thermally decomposing a volatile carbon-containing gas (e.g., ethylene) onto the surface of the particulate material. Alternatively, the carbon coating may be formed by depositing a solution of a carbon-containing compound onto the surface of the particulate material and then thermally decomposing it. The conductive carbon coating has sufficient permeability to allow lithium to approach the interior of the composite particles without excessive resistance, thereby not reducing the rate performance of the composite particles. For example, the thickness of the carbon coating may suitably be in the range of 2 to 30 nm. Optionally, the carbon coating may be porous and / or may only partially cover the surface of the composite particles.

[0112] Alternatively, the coating may comprise a lithium ion permeable solid electrolyte. Examples of suitable lithium permeable solid electrolytes include: garnet-type solid electrolytes (including "LLZO" electrolytes such as Li7La3Zr2O 12 He Li 6.5 La3Ti 0.5 Zr 1.5 O 12 ); Perovskite solid electrolytes (including "LLTO" electrolytes, such as Li 0.33 La 0.57 TiO3); LISICON type solid electrolyte, NaSICON type solid electrolyte (such as Li 1.3 Al 0.3 Ti 1.7 (PO4)3); lithium phosphorus oxynitride (LiPON) solid electrolyte; Li3N type solid electrolyte; lithium phosphate (Li3PO4) solid electrolyte, lithium titanate (Li4Ti5O 12 ) solid electrolyte; lithium tantalate (LiTaO3) solid electrolyte; sulfide-type solid electrolyte; argyrodite-type solid electrolyte; and antiperovskite-type solid electrolyte. Also included are variations (e.g., including dopants) and combinations of these electrolyte types.

[0113] The coating has the advantage that it further reduces the BET surface area of ​​the particle material by smoothing any surface defects and by filling any remaining surface micropores, thereby further reducing first cycle losses. The use of a conductive coating, such as a carbon coating, is particularly advantageous because it improves the conductivity of the surface of the composite particles, improves the rate performance of the particle material when used as an electroactive material in a lithium-ion battery, and / or reduces the need for conductive additives in the electrode composition, and also creates an improved surface for forming a stable SEI layer, resulting in improved capacity retention upon cycling. Where the composite particles include a coating, the silicon content of the particles (in wt %) is determined based on the weight of the particles including the coating.

[0114] A preferred particulate material according to the present invention is a particulate material wherein: 1 In the range of 0.65 to 1.2, the micropore volume fraction is in the range of 0.5 to 0.7, the particulate material comprises 38 wt% to 58 wt% silicon, and at least 30 wt% of the silicon (e.g., 30 wt% to 75 wt%, 30 wt% to 70 wt%, or 30 wt% to 65 wt% silicon) is surface silicon as determined by thermogravimetric analysis (TGA). Preferably, no more than 10 wt% of the silicon is bulk silicon as determined by TGA. Any of the features disclosed herein as preferred or optional may also apply to this embodiment.

[0115] A more preferred particulate material according to the present invention is one in which: 1 In the range of 0.7 to 1.1, the micropore volume fraction is in the range of 0.48 to 0.76, the particulate material comprises 40 wt% to 58 wt% silicon, and at least 35 wt% of the silicon (e.g., 35 wt% to 70 wt%, 35 wt% to 65 wt%, or 35 wt% to 60 wt% silicon) is surface silicon as determined by thermogravimetric analysis (TGA). Preferably, no more than 8 wt% of the silicon is bulk silicon as determined by TGA. Any of the features disclosed herein as preferred or optional may also apply to this embodiment.

[0116] A more preferred particulate material according to the present invention is one in which: 1 In the range of 0.75 to 1.1, the micropore volume fraction is in the range of 0.5 to 0.74, the particulate material comprises 42 wt% to 56 wt% silicon, and at least 40 wt% of the silicon (e.g., 40 wt% to 65 wt%, 40 wt% to 60 wt%, or 40 wt% to 55 wt% silicon) is surface silicon as determined by thermogravimetric analysis (TGA). Preferably, no more than 5 wt% of the silicon is bulk silicon as determined by TGA. Any of the features disclosed herein as preferred or optional may also apply to this embodiment.

[0117] A more preferred particulate material according to the present invention is one in which: 1 In the range of 0.8 to 1, the micropore volume fraction is in the range of 0.52 to 0.72, the particulate material comprises 44 wt% to 54 wt% silicon, and at least 45 wt% of the silicon (e.g., 45 wt% to 65 wt%, 45 wt% to 60 wt%, or 45 wt% to 55 wt% silicon) is surface silicon as determined by thermogravimetric analysis (TGA). Preferably, no more than 2 wt% of the silicon is bulk silicon as determined by TGA. Any of the features disclosed herein as preferred or optional may also apply to this embodiment.

[0118] 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 framework. As used herein, CVI refers to a process in which a gaseous silicon-containing gas is thermally decomposed on a surface to form elemental silicon and gaseous byproducts at the surface.

[0119] According to a second aspect of the present invention, there is provided a method for preparing silicon-containing composite particles, the method comprising the following steps:

[0120] (a) providing a plurality of porous carbon particles, wherein the porous carbon particles comprise micropores and / or mesopores, wherein:

[0121] (i) The total pore volume of the micropores and mesopores measured by gas adsorption is P 1 cm 3 / g, where P 1 represents a number with a value between 0.5 and 1.5,

[0122] (ii)PD 90 The pore size is at least 3 nm and less than 12 nm; and

[0123] (iii) Based on P 1 The micropore volume fraction is 0.43 to 0.85;

[0124] (b) contacting the plurality of porous carbon particles with a gas containing 0.5 to 20 volume % of a silicon precursor gas at a temperature of 400 to 700° C. to deposit silicon into pores of the porous carbon particles.

[0125] According to a third aspect of the present invention, there is provided a method for preparing silicon-containing composite particles, the method comprising the following steps:

[0126] (a) providing a plurality of porous carbon particles, wherein the porous carbon particles comprise micropores and / or mesopores, wherein:

[0127] (i) The total pore volume of the micropores and mesopores measured by gas adsorption is P 1

[0128] cm 3 / g, where P 1 represents a number with a value between 0.5 and 1.5,

[0129] (ii)PD 90 The pore size is at least 3 nm and less than 12 nm; and

[0130] (iii) Based on P 1 The micropore volume fraction is 0.43 to 0.85;

[0131] (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 into pores of the porous carbon particles, wherein the partial pressure of the silicon precursor gas is 0.5 to 20 kPa.

[0132] The methods of the second and third aspects of the invention may be used to prepare the particulate material of the first aspect of the invention.Unless otherwise stated, the following preferred features apply to the second and third aspects.

[0133] Suitable gaseous silicon-containing precursors include silane (SiH4), silane derivatives (eg, disilane, trisilane, and butasilane), and trichlorosilane (SiHCl3).

[0134] Optionally, the silicon-containing precursor is chlorine-free. Chlorine-free means 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.

[0135] The silicon-containing precursor may be used neat or, more typically, as a mixture diluted with an inert carrier gas such as nitrogen or argon.

[0136] Step (b) is suitably carried out at a total pressure of 101.3 kPa (ie 1 atm) or less with a low partial pressure of the silicon precursor, the remaining partial pressure being made up to atmospheric pressure using an inert filler gas such as hydrogen, nitrogen or argon.

[0137] According to the second aspect of the present invention, the silicon-containing precursor is used in an amount of 0.5 vol% to 20 vol%, for example 1 vol% to 15 vol%, or 1 vol% to 10 vol%, or 1 vol% to 5 vol%, preferably at least 3 vol%, based on the total volume of the silicon precursor gas and the inert carrier gas.

[0138] According to a third aspect of the present invention, the partial pressure of the silicon precursor gas is 0.5 to 20 kPa, or 1 to 15 kPa, or 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., assuming ideal gas behavior). If pure silicon precursor gas is used, the partial pressure of the silicon precursor gas is equal to the total pressure. Alternatively, the total pressure can be the sum of the partial pressures of the silicon precursor gas and an inert filler gas such as nitrogen or argon.

[0139] In step (b), a temperature in the range of 400 to 700° C. is used, preferably 425 to 550° C., or 425 to 500° C. Optionally, the porous carbon particles are contacted with the silicon precursor gas at an initial temperature below 400° C., and then the reaction temperature is increased to a range of 400 to 700° C.

[0140] Step (b) is optionally carried out using stirring or fluidisation of the porous carbon particles, which is particularly preferred when the process is carried out on a large scale. Suitable reactor types include rotary kilns or fluidised bed reactors (including spouted bed reactors).

[0141] In order to obtain the particulate material of the present invention having a high surface silicon content, the CVI process must be carefully controlled to ensure that the rate of silicon deposition is low relative to the diffusion rate of the silicon precursor gas into the pore structure of the porous carbon framework. Operation within the preferred temperature range of 425 to 500°C and the use of a low concentration of silicon precursor gas can also control the rate of silicon deposition, ensuring that the rate of silicon deposition is low relative to the penetration rate of the silicon precursor. The conditions within the CVI reactor should also be as uniform as possible. Agitation or fluidization of the porous carbon particles ensures that the silicon precursor gas can evenly penetrate the particles and that the temperature in the reactor is uniform throughout the particle bed.

[0142] Preferably, step (b) is carried out under a pressure lower than atmospheric pressure. For example, step (b) can be carried out under an absolute pressure lower than 100kPa, or lower than 90kPa, or lower than 80kPa, or lower than 70kPa, or lower than 60kPa. Preferably, step (b) is carried out under an absolute pressure of at least 5kPa, or at least 10kPa, or at least 15kPa, or at least 20kPa, or at least 25kPa, or at least 30kPa. For example, step b is preferably carried out under an absolute pressure within the range of 10 to 90kPa, or 20 to 80kPa, or 20 to 70kPa, or 30 to 60kPa.

[0143] It has been found that carrying out step (b) at a pressure below atmospheric pressure results in a significant improvement in the surface silicon content of the particulate material product.

[0144] Preferred operating conditions for forming a particulate material product comprising greater than 20% surface silicon in step (b) include using a gas comprising 0.5% to 20% by volume of a silicon precursor gas (preferably silane) at an absolute pressure of 10 to 90 kPa. More preferably, a gas comprising 2% to 15% by volume of a silicon precursor is used at an absolute pressure of 20 to 80 kPa. More preferably, a gas comprising 5% to 10% by volume of a silicon precursor is used at an absolute pressure of 30 to 60 kPa. With reference to the accompanying examples, operation within these preferred conditions reliably provides particulate materials having very high surface silicon contents of at least 30% or even at least 40%. The careful selection of the porous carbon particles described herein, together with the use of controlled CVI conditions, enables the production of particulate materials having very high surface silicon contents and low bulk silicon contents, indicating that a high proportion of the silicon is present in the form of ultrafine silicon nanostructures. Such materials have not been reported in the prior art.

[0145] The surface of the electroactive material deposited by CVI is reactive towards oxygen and forms a native oxide layer when exposed to atmospheric oxygen. In the case of silicon, an amorphous silicon dioxide film is formed immediately when the silicon surface is exposed to oxygen. The formation of the native oxide layer is exothermic and therefore requires careful process control to prevent overheating or even combustion of the particulate material during manufacture or storage. The presence of the native oxide layer is associated with irreversible capacity loss and shortened 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 optionally include the further step (c) of contacting the exposed surface of the deposited silicon with a passivating agent, wherein the silicon is not exposed to oxygen prior to contact with the passivating agent.

[0146] A passivating agent is defined herein as a compound capable of modifying the surface of an electroactive material so as to inhibit or prevent the formation of surface oxides.

[0147] Suitable deactivators include compounds containing an alkene, alkyne or carbonyl functional group, more preferably a terminal alkene, terminal alkyne or aldehyde group.

[0148] Preferred deactivators include one or more compounds having the formula:

[0149] (i) R-CH=CH-R;

[0150] (ii) RC ≡ CR; and

[0151] (iii) O=CH-R;

[0152] wherein R represents H or an unsubstituted or substituted aliphatic or aromatic hydrocarbon group having 1 to 20 carbon atoms, preferably 2 to 10 carbon atoms, or wherein the two R groups in formula (i) form an unsubstituted or substituted hydrocarbon ring structure containing 3 to 8 carbon atoms.

[0153] Particularly preferred deactivators include one or more compounds having the formula:

[0154] (i) CH2=CH-R; and

[0155] (ii) HC≡CR;

[0156] wherein R is as defined above. Preferably, R is unsubstituted.

[0157] 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 deactivators may also be used. A preferred deactivator is ethylene.

[0158] It is believed that the olefin, alkyne, or carbonyl groups of the passivating agent undergo an insertion reaction with the MH groups (wherein M represents an atom of the electroactive material) on the surface of the electroactive material to form a covalently passivated surface that is resistant to oxidation by air. When silicon is the electroactive material, the passivation reaction between the silicon surface and the passivating agent can be understood as a form of hydrosilation, as shown schematically below.

[0159]

[0160] Other suitable passivating agents include compounds containing active hydrogen atoms bonded to oxygen, nitrogen, sulfur, or phosphorus. For example, the passivating agent can be an alcohol, an amine, a thiol, or a phosphine. The reaction of the group -XH with the hydride group on the surface of the electroactive material is understood to result in the elimination of H2 and the formation of a direct bond between X and the surface of the electroactive material.

[0161] Suitable deactivators in this class include compounds of the formula:

[0162] (iv)HX-R,

[0163] Wherein X represents O, S, NR or PR, and wherein each R is independently as defined above.Two R groups in formula (iv) can also form substituted or unsubstituted alkyl ring structure comprising 3 to 8 carbon atoms.Preferably, X represents O or NH, and R represents an optionally substituted aliphatic or aromatic group with 2 to 10 carbon atoms.Also can amido be incorporated into 4-10 yuan aliphatic or aromatic ring structure, as the ring structure in pyrrolidine, pyrroles, imidazoles, piperazine, indole or purine.

[0164] In the case where the passivating agent is a carbon-containing compound, the contacting of the electroactive material with the passivating agent in step (c) can be carried out at a temperature above or below the pyrolysis temperature of the passivating agent. When the electroactive material is contacted with the passivating agent at a temperature below the pyrolysis temperature of the passivating agent, only a passivating layer is formed on the silicon surface. When the electroactive material is contacted with the passivating agent at a temperature above the pyrolysis temperature of the passivating agent, passivation of the silicon surface occurs together with the formation of a pyrolytic carbon coating.

[0165] 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 at a pressure in the range of 100 kPa to 50 MPa. For example, step (c) may be suitably carried out within the preferred temperature and pressure ranges as described herein for step (b).

[0166] Another suitable passivating agent is ammonia. Thus, step (c) may comprise contacting the surface of the deposited electroactive material with ammonia at a temperature in the range of 200-700°C, preferably 400-700°C. For example, where the passivating agent is ammonia, step (c) may be carried out at the same temperature as that used to deposit the electroactive material in step (b). The temperature is then raised, if necessary, to a range of 500 to 1,000°C to form a crystalline nitride surface (e.g., a silicon nitride surface of the formula SiNx, where x≤4 / 3). Thus, passivation with ammonia provides an alternative means of limiting oxidation of the electroactive material. Because stoichiometrically deficient silicon nitride is conductive, this step also results in the formation of a conductive network that will enable faster charging and discharging of the electroactive material.

[0167] The passivation in step (c) can optionally be carried out in the same reactor as step (b), for example by stopping the flow of silicon precursor gas to the reactor and starting the flow of passivating agent gas to the reactor. Optionally, the reactor can be flushed with an inert gas before step (c).

[0168] The method of the present invention may optionally include a further step (d) of forming a conductive carbon coating on the surface of the composite particles from step (b) or from step (c) (if a passivation step is performed). Step (d) suitably comprises contacting the electroactive material with the pyrolytic carbon precursor at a temperature above the pyrolysis temperature of the pyrolytic carbon precursor.

[0169] Suitable conditions for step (d) are discussed in detail in WO 2021 / 048556.

[0170] As an example of a fixed bed reactor method (experimental scale), 1.8 g of a granular porous carbon skeleton is placed on a stainless steel plate along its length with a constant thickness of 1 mm. The plate is then placed in a stainless steel tube with an outer diameter of 60 mm with a gas inlet and outlet line in the hot zone of a retort furnace. The furnace tube is purged with nitrogen for 30 minutes at room temperature, and the sample temperature is then raised to 450-500 ° C. The nitrogen flow rate is adjusted to ensure a gas residence time of at least 90 seconds in the furnace tube, and the nitrogen flow rate is maintained at this rate for 30 minutes. The gas supply is then switched from nitrogen to a mixture of monosilane in nitrogen at a concentration of 1.25% by volume. The feeding of monosilane is carried out over a period of 5 hours while the reactor pressure is maintained at 101.3 kPa (1 atm). After the feeding is completed, the gas flow rate is kept constant while purging silane from the furnace with nitrogen. The furnace is purged under nitrogen for 30 minutes. Optionally, a surface passivation step is then carried out by contacting the material with a passivating gas. The furnace was then cooled to room temperature over a period of several hours.The atmosphere was then gradually switched to air over a period of two hours by switching the gas flow from nitrogen to air from a compressed air supply.

[0171] As an example of a fluidized bed reactor process (production scale), 50 g of the particulate porous carbon framework was placed in a fluidized bed reactor fabricated with a 0.95 cm (3 / 8") stainless steel gas inlet, a 60 mm outer diameter (OD) tubular section with a length of 520 mm, and a stainless steel expansion head with an OD of 100 mm. The reactor was suspended from a frame, and a vertically oriented tube furnace was arranged so that the hot zone extended from the conical section to ¾ of the length of the cylindrical section (approximately 380 mm long). The minimum fluidization velocity was determined using a cold flow pressure drop test using nitrogen as the inert gas, with the gas flow rate varied between 1 and 2.5 L / min. Once the minimum fluidization velocity was determined, the inert gas flow rate was maintained constantly above the minimum fluidization velocity. The furnace was then heated to 150°C. The temperature is raised to the desired reaction temperature under a constant inert gas flow rate. After the target temperature between 435-500°C is stabilized, the fluidizing gas is switched from pure nitrogen to 1.25% by volume monosilane in nitrogen. The reaction progress is monitored by measuring the pressure drop and furnace temperature difference between the top and bottom. The gas flow rate is adjusted throughout the run to maintain a pressure drop consistent with continuous fluidization and to maintain a minimum temperature difference between the top and bottom of the bed of less than 40°C. After 12 hours, while maintaining fluidization, the fluidizing gas is switched to pure nitrogen, and this purge lasts for 30 minutes. Optionally, a surface passivation step is then performed by contacting the material with a passivating gas. The furnace is then cooled to ambient temperature over a period of several hours. Upon reaching ambient temperature, the furnace atmosphere is gradually switched to air over a period of several hours.

[0172] As an example of a reduced pressure fluidized bed reactor process (production scale), 250 g of particulate porous carbon skeletons were placed in a fluidized bed reactor that was fabricated with multiple nozzles designed for horizontal gas injection at a jet velocity of 0.5-2 m / s into an 89 mm outer diameter (OD) tubular reactor section with a length of 1100 mm and a stainless steel expansion head with an OD of 457 mm. The reactor was suspended on a frame, and a vertically oriented tube furnace was arranged so that the hot zone spanned the entire length of the cylindrical section (approximately 380 mm long) from the conical section. The reactor vessel was vibrated at a frequency of 5-140 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 an inert gas. The furnace was 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 monosilane (SiH 4 ) and 9 sL / min nitrogen. The rate of silicon deposition is monitored by measuring the hydrogen volume % in the effluent gas over time. Once about 200g of silicon (about 45 % by weight Si) has been deposited, gas flow is switched to a mixture of 0.5sL / min monosilane (SiH 4 ) and 9sL / min nitrogen, until about 250g of silicon (about 49.5 % by weight to 51.5 % by weight Si) has been deposited. Then, while maintaining fluidization, fluidizing gas is switched to pure nitrogen for about 30 minutes to purge the reactor. Optionally, the surface passivation step is then carried out by contacting the material with a passivating gas. Then, within a few hours, the furnace is cooled to ambient temperature. When ambient temperature is reached, furnace atmosphere is gradually switched to air within a few hours.

[0173] In a fourth aspect of the present invention, a composition is provided comprising the particulate material according to the first aspect of the present invention and at least one other component. In particular, a composition is provided comprising the particulate material according to the first aspect of the present invention and at least one other component selected from the group consisting of: (i) a binder; (ii) a conductive additive; and (iii) an additional particulate electroactive material. The composition according to the fourth aspect of the present invention can be used as an electrode composition and can therefore be used to form the active layer of an electrode.

[0174] 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.

[0175] The composition may be a hybrid electrode composition comprising the particulate material according to the first aspect of the invention and at least one additional particulate electroactive material. Examples of additional particulate electroactive materials include graphite, hard carbon, silicon, tin, germanium, aluminum, and lead. The at least one additional particulate electroactive material is preferably selected from graphite and hard carbon, and most preferably, the at least one additional particulate electroactive material is graphite.

[0176] In the case of a hybrid electrode composition, the composition preferably comprises 3 wt% to 60 wt%, 3 wt% to 50 wt%, 5 wt% to 50 wt%, or 10 wt% to 50 wt%, or 15 wt% to 50 wt% of the particulate material according to the first aspect of the invention, based on the total dry weight of the composition.

[0177] The at least one further particulate electroactive material is suitably present in an amount of from 20 wt% to 95 wt%, or from 25 wt% to 90 wt%, or from 30 wt% to 750 wt% of the at least one further particulate electroactive material.

[0178] At least one additional particulate electroactive material D 50 The particle size is preferably in the range of 10 to 50 μm, preferably in the range of 10 to 40 μm, more preferably in the range of 10 to 30 μm, and most preferably in the range of 10 to 25 μm, for example in the range of 15 to 25 μm.

[0179] At least one additional particulate electroactive material D 10 The particle size is preferably at least 5 μm, more preferably at least 6 μm, more preferably at least 7 μm, more preferably at least 8 μm, more preferably at least 9 μm, and still more preferably at least 10 μm.

[0180] At least one additional particulate electroactive material D 90 The particle size is preferably at most 100 μm, more preferably at most 80 μm, more preferably at most 60 μm, more preferably at most 50 μm, and most preferably at most 40 μm.

[0181] The at least one additional particulate electroactive material is preferably selected from particles comprising carbon, graphite particles and / or hard carbon particles, wherein the D of the graphite particles and the hard carbon particles is 50 The particle size is in the range of 10 to 50 μm. Still more preferably, the at least one additional particulate electroactive material is selected from graphite particles, wherein the graphite particles have a D 50 The particle size ranges from 10 to 50 μm.

[0182] The composition may also be a non-mixed (or "highly loaded") electrode composition that is substantially free of additional particulate electroactive materials. In this case, the term "substantially free of additional particulate electroactive materials" should be interpreted to mean that the composition contains less than 15 wt%, preferably less than 10 wt%, preferably less than 5 wt%, preferably less than 2 wt%, more preferably less than 1 wt%, more preferably less than 0.5 wt% of any additional electroactive material (i.e., additional material capable of intercalating and releasing metal ions during charge and discharge of the battery), based on the total dry weight of the composition.

[0183] This type of "highly loaded" electrode composition preferably comprises at least 50 wt%, or at least 60 wt%, or at least 70 wt%, or at least 80 wt%, or at least 90 wt% of the particulate material according to the first aspect of the invention, based on the total dry weight of the composition.

[0184] The composition may optionally include a binder. The binder serves to adhere the composition to the current collector and maintain the integrity of the composition. Examples of binders that can be used according to the present invention include polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, carboxymethyl cellulose (CMC), modified carboxymethyl cellulose (mCMC), sodium carboxymethyl cellulose (Na-CMC), polyvinyl alcohol (PVA), alginate and its alkali metal salts, styrene-butadiene rubber (SBR) and polyimide. The composition may include a mixture of multiple binders. Preferably, the binder includes a polymer selected from the following: polyacrylic acid (PAA) and its alkali metal salts, and modified polyacrylic acid (mPAA) and its alkali metal salts, SBR and CMC.

[0185] The binder may suitably be present in an amount of 0.5 to 20 wt%, preferably 1 to 15 wt%, preferably 2 to 10 wt% and most preferably 5 to 10 wt% based on the total dry weight of the composition.

[0186] The binder may optionally be present in combination with one or more additives that modify the properties of the binder, such as crosslinking accelerators, coupling agents and / or adhesion promoters.

[0187] The composition may optionally include one or more conductive additives. Preferred conductive additives are non-electroactive materials that are included to improve the conductivity between the electroactive components of the composition and the conductivity between the electroactive components of the composition and the current collector. The conductive additive can suitably be selected from carbon black, carbon fiber, carbon nanotubes, graphene, acetylene black, Ketjen black, metal fibers, metal powders, and conductive metal oxides. Preferred conductive additives include carbon black and carbon nanotubes.

[0188] One or more conductive additives may suitably be present in a total amount of 0,5 to 20 wt%, preferably 1 to 15 wt%, preferably 2 to 10 wt% and most preferably 5 to 10 wt%, based on the total dry weight of the composition.

[0189] In a fifth aspect, the present invention provides an electrode comprising a particulate material as defined in the first aspect of the present invention in electrical contact with a current collector. The particulate material used to prepare the electrode of the fifth aspect of the present invention may have any of the features described as preferred or optional in relation to the first aspect of the present invention.

[0190] As used herein, the term current collector refers to any conductive substrate capable of carrying an electric current to and from the electroactive particles in the composition. Examples of materials that can be used as current collectors include copper, aluminum, stainless steel, nickel, titanium, and sintered carbon. Copper is a preferred material. The current collector is generally in the form of a foil or mesh having a thickness of 3 to 500 μm. The granular material of the present invention can be applied to one or both surfaces of the current collector to a thickness preferably in the range of 10 μm to 1 mm, for example 20 to 500 μm, or 50 to 200 μm.

[0191] Preferably, the electrode comprises a composition as defined in accordance with the fourth aspect of the invention in electrical contact with a current collector.The composition may have any of the features described as preferred or optional in relation to the fourth aspect of the invention.

[0192] The electrode of the fifth aspect of the present invention can be suitably prepared in the following manner: the granular material of the present invention (optionally in the form of a composition of the present invention) is combined with a solvent and optionally one or more viscosity modifier additives to form a slurry. The slurry is then cast onto the surface of the current collector, and the solvent is removed to form an electrode layer on the surface of the current collector. Additional steps may be performed as appropriate, such as heat treatment for curing any binder and / or calendering of the electrode layer. The thickness of the electrode layer is suitably in the range of 20 μm to 2 mm, preferably 20 μm to 1 mm, preferably 20 μm to 500 μm, preferably 20 μm to 200 μm, preferably 20 μm to 100 μm, preferably 20 μm to 50 μm.

[0193] Alternatively, the slurry can be formed into a free-standing film or mat comprising the particulate material of the present invention, for example by casting the slurry onto a suitable casting template, removing the solvent, and then removing the casting template. The resulting film or mat is in the form of a cohesive, free-standing object that can then be combined with a current collector by known methods.

[0194] The electrode of the fifth aspect of the present invention can be used as an anode of a metal ion battery. Therefore, in a sixth aspect, the present invention provides a rechargeable metal ion battery comprising: an anode comprising an electrode as described above; a cathode comprising a cathode active material capable of releasing and reabsorbing metal ions; and an electrolyte between the anode and the cathode.

[0195] The metal ion is preferably a lithium ion. 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.

[0196] The cathode active material is preferably a composite material based on metal oxides. Examples of suitable cathode active materials include LiCoO2, LiCo 0.99 Al 0.01 O2, LiNiO2, LiMnO2, LiCo 0.5 Ni 0.5 O2、LiCo 0.7 Ni 0.3 O2、LiCo 0.8 Ni 0.2 O2、LiCo 0.82 Ni 0.18 O2、LiCo 0.8 Ni 0.15 Al 0.05 O2、LiNi 0.4 Co 0.3 Mn 0.3 O2 and LiNi 0.33 Co 0.33 Mn 0.34 O2. The cathode current collector generally has a thickness of 3 to 500 μm. Examples of materials that can be used as the cathode current collector include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0197] Electrolyte is suitably a non-aqueous electrolyte containing a metal salt (such as a lithium salt), and can include but is not limited to non-aqueous electrolytes, solid electrolytes and inorganic solid electrolytes. The example of operable non-aqueous electrolyte solution includes 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, triester phosphate, trimethoxymethane, sulfolane, methyl sulfolane and 1,3-dimethyl-2-imidazolidinone.

[0198] Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate polymers, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ion dissociative groups.

[0199] Examples of inorganic solid electrolytes include nitrides, halides, and sulfides of lithium salts (such as Li5NI2, Li3N, LiI, LiSiO4, Li2SiS3, Li4SiO4, LiOH, and Li3PO4).

[0200] The lithium salt is suitably soluble in the selected solvent or solvent mixture. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO4, LiBF4, LiBC4O8, LiPF6, LiCF3SO3, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li and CF3SO3Li.

[0201] In the case where the electrolyte is a non-aqueous organic solution, the metal ion battery preferably has a separator between the anode and cathode. The separator is generally formed of an insulating material with high ion permeability and high mechanical strength. The separator generally has a pore size of 0.01 to 100 μm and a thickness of 5 to 300 μm. Examples of suitable electrode separators include microporous polyethylene films.

[0202] The separator may be replaced by a polymer electrolyte material, and in such a 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. Example

[0203] The porous carbon frameworks C1 to C13 used in the following examples have the properties listed in Table 1.

[0204]

[0205] Example 1: Preparation of granular material in a stationary furnace

[0206] Silicon-carbon composite particles are prepared by placing 1.8 g of a porous skeleton of particles having the properties listed in Table 1 on a stainless steel plate at a constant thickness of 1 mm along the length of the stainless steel plate. The plate is then placed in a stainless steel tube with an outer diameter of 60 mm having a gas inlet and outlet line in the hot zone of a retort furnace. The furnace tube is purged with nitrogen for 30 minutes at room temperature, and the sample temperature is then raised to 450 to 475 ° C. The nitrogen flow rate is adjusted to ensure a gas residence time of at least 90 seconds in the furnace tube, and maintained at this rate for 30 minutes. The gas supply is then switched from nitrogen to a mixture of monosilane in nitrogen at a concentration of 1.25% by volume. The feeding of monosilane is carried out within a maximum of 5 hours while the reactor pressure is maintained at 101.3 kPa (1 atm). After the feeding is complete, the gas flow rate is kept constant while purging silane from the furnace with nitrogen. The furnace is purged under nitrogen for 30 minutes and then cooled to room temperature within a few hours. The atmosphere was then gradually switched to air over a two hour period by switching the gas flow from nitrogen to air from a compressed air supply.

[0207] Example 2: Determination of surface silicon content

[0208] Using the method of Example 1, a series of samples of composite particles having different amounts of deposited silicon (varying between 20 wt % and 60 wt %) were prepared using the various carbons mentioned in Table 1. Surface silicon was calculated from the TGA curves of each sample. Table 2 provides the average, maximum, and minimum values ​​of surface silicon for the sample group made with the various carbons. It can be seen that very small or negligible amounts of surface silicon can be achieved using carbons C1, C10, and C13, while good surface silicon levels can be consistently achieved in all samples using carbons C3, C4, C5, C7, C8, and C9. Different surface silicon levels were obtained using the other carbons.

[0209] Table 2

[0210]

[0211] *Comparison samples

[0212] Example 3: Preparation of granular material in a fluidized bed reactor

[0213] Silicon-carbon composite particles were prepared in a vertical bubbling fluidized bed reactor comprising a stainless steel cylindrical container of 83 mm inner diameter operating at atmospheric pressure. A 250 g quantity of carbon skeleton particle powder having the properties listed in Table 1 was placed in the reactor. A low flow rate of inert gas (nitrogen) was injected into the reactor to remove any oxygen. The reactor was then heated to a reaction temperature of 430 to 500° C., and 4% v / v of monosilane gas diluted in nitrogen was supplied to the bottom of the reactor at a flow rate sufficient to fluidize the carbon skeleton particles for a period of time sufficient to deposit the target mass of silicon. The reactor was purged under nitrogen for 30 minutes and then cooled to room temperature over a period of several hours. The atmosphere was then gradually switched to air over a two hour period by switching the gas flow from nitrogen to air from a compressed air supply.

[0214] The method of Example 3 was used to prepare the granular materials S1, S2 and S4 to S8 of Table 3.

[0215] Example 4: Preparation of granular material at low pressure in a fluidized bed reactor

[0216] Silicon-carbon composite particles were prepared in a vertical bubbling fluidized bed reactor comprising a stainless steel cylindrical container having an inner diameter of 83 mm. A 250 g amount of carbon skeleton particle powder having the properties listed in Table 1 was placed in the reactor. 10 sL / min (standard liters per minute) of nitrogen was used as an inert gas to fluidize the porous carbon particles at a pressure of 38 kPa (absolute). The furnace was heated to a temperature of 450° C. at a constant inert gas flow rate. The gas flow was then slowly switched to a mixture of 2 sL / min monosilane (SiH 4 ) and 9 sL / min nitrogen. The rate of silicon deposition was monitored by measuring the hydrogen volume % in the effluent gas over time. Once approximately 200 g of silicon (approximately 45 wt % Si) had been deposited, the gas flow was switched to a mixture of 0.5 sL / min monosilane (SiH 4 ) and 9 sL / min nitrogen until approximately 250 g of silicon (approximately 49.5 wt % to 51.5 wt % Si) had been deposited. The fluidizing gas was then switched to pure nitrogen at a rate of 10 sL / min for approximately 30 minutes while maintaining fluidization to purge the reactor. The fluidizing gas was then switched to a mixture of ethylene (C2H4) at 2 sL / min and nitrogen at 9 sL / min to passivate the silicon surface. The fluidizing gas was then switched to pure nitrogen at a rate of 4 sL / min. The furnace was then cooled to ambient temperature over a period of several hours. Upon reaching ambient temperature, the furnace atmosphere was gradually switched to air over a period of several hours.

[0217] The method of Example 4 was used to prepare the granular materials S9 to S11 of Table 3.

[0218] Example 5: Carbon coating:

[0219] A large amount of composite particles prepared using the method of Example 3 was placed in a stainless steel tube loaded into 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 raised to 675°C under a nitrogen flow. A measured amount of styrene was placed in a Dreschel bottle and heated to 75°C in a water bath. After the furnace temperature stabilized for 10 minutes, styrene was flowed into the reactor tube by bubbling 2 L / min of nitrogen into the Dreschel bottle for 90 minutes. The reactor was then purged with nitrogen and cooled to ambient temperature under nitrogen to obtain the carbon-coated material.

[0220] The granular material S3 in Table 3 was prepared according to the method of Example 3 and then carbon-coated using the method of Example 4.

[0221] Example 6: Calculation of surface silicon and bulk silicon:

[0222] The procedure used to calculate the surface silicon and bulk silicon content of the composite materials of the examples is as follows. A 10 mg (±2 mg) test sample was loaded into a 70 μL crucible. The sample was loaded into a Mettler Toledo TGA / DSC3+ instrument using 100 mL / min of Ar purge gas, N2 fill gas, and air reaction gas. The TGA chamber was heated from 25°C to 1400°C at a rate of 10°C / min. Data were collected at 1 s intervals. Figure 1 is the TGA graph of a sample of material S1 from Table 3, and Figure 2 is a graph of a sample of material S7 from Table 3. The values ​​of bulk silicon and surface silicon were extracted by finding the maximum mass (in mg) measured in the temperature range of 550° C. to 650° C. (labeled c), the final ash mass (labeled e), the minimum mass below 500° C. after loss of volatiles (labeled b), and the mass at 800° C. (labeled d). The values ​​of surface silicon (Y) and bulk gross silicon (Z) were calculated using the formula listed above.

[0223] Table 3

[0224]

[0225] *Comparison samples

[0226] Sample S3 was carbon coated according to the method of Example 5.

[0227] Comparative samples S7 and S8 demonstrate the importance of carefully controlled regulation in the FBR reaction. In comparative sample S7, the interruption of the fluidizing gas supply caused the particles in the reactor bed to defluidize and form overheated areas within the reactor, resulting in reduced silicon penetration and increased silicon deposition on the surface of the porous carbon skeleton (as indicated by the increase in crude silicon measurement results). In comparative example S8, the temperature of the FBR reaction was varied so that the reaction was partially carried out at less than 400°C. Without being bound by theory, it is believed that silicon deposition into the micropores is kinetically favorable at temperatures above 400°C and particularly above 425°C, but lower temperatures result in increased silicon deposition on the outer surface of the porous carbon support.

[0228] Samples S9 to S11 demonstrate the effect of performing step (b) at a pressure below atmospheric pressure. Samples S1 to S6 contained 22 to 40 wt% surface silicon after their preparation using the atmospheric pressure CVI process, while samples S9 to S11 prepared at 38 kPa contained approximately 50 wt% surface silicon.

[0229] Example 7: Preparation of test cells

[0230] The Si-C composite materials in Table 3 were used to prepare negative electrode coatings (anodes) and tested in full button cells. To make the electrodes, a dispersion of carbon black in a CMC binder was prepared in a Thinky TM The Si-C composite material was added to the mixture and mixed in a Thinky TM The mixture was mixed in a mixer for 30 minutes. Then, SBR binder was added to provide a CMC:SBR ratio of 1:1 to obtain a slurry with a weight ratio of Si-C composite material: CMC / SBR: carbon black of 70%:16%:14%. The slurry was placed in a Thinky TM The mixture was mixed in a mixer for another 30 minutes, and then coated onto a 10 μm thick copper substrate (current collector) and dried at 50°C for 10 minutes, followed by drying at 110°C for 12 hours to form a coating density of 0.7 ± 0.5 g / cm 3 of the negative electrode.

[0231] A full button cell was prepared using a circular negative electrode with a radius of 0.8 cm cut from the negative electrode, a porous polyethylene separator, and a nickel-manganese-cobalt (NMC532) positive electrode. The positive and negative electrodes were designed to form a balanced pair so that the capacity ratio of the positive electrode to the negative electrode was 0.9. An electrolyte comprising 1M LiPF6 in a solution of fluoroethylene carbonate, ethylene carbonate, and ethyl methyl carbonate containing 3% by weight of ethylene carbonate was then added to the cell before sealing.

[0232] The button cell was cycled as follows: a constant current was applied at a rate of C / 25 to lithiate the anode with a cutoff voltage of 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 left to rest in the lithiated state for 10 minutes. The anode was then delithiated at a constant current of C / 25 with a cutoff voltage of 2.75 V. The cell was then left to rest for 10 minutes. After this initial cycle, a constant current of C / 2 was applied to lithiate the anode with a cutoff voltage of 4.3 V, followed by a constant voltage of 4.3 V with a cutoff current of C / 40 and a rest time of 5 minutes. The anode was then delithiated at a constant current of C / 2 with a cutoff of 2.75 V. This process was then repeated for the desired number of cycles. The capacity retention ratio at the 100th cycle (CR100) and the capacity retention ratio at the 500th cycle (CR500) were calculated and given in Table 4 together with the 1st lithiation capacity, the 1st delithiation capacity and the first cycle loss (FCL).

[0233] The charge (lithiation) and discharge (delithiation) capacities per unit mass of the silicon-carbon composite were calculated for each cycle, and the capacity retention value for each discharge capacity was calculated as a percentage of the discharge capacity at the second cycle. The first cycle loss (FCL) is (1-(first delithiation capacity / first lithiation capacity))×100%. The values ​​in Table 4 are the averages of three button cells for each material.

[0234] Table 4: Electrochemical data

[0235]

[0236] *Compare samples.

Claims

1. A granular material consisting of a plurality of composite particles, wherein the composite particles comprise: (a) A porous carbon framework containing micropores and mesopores, The total pore volume of the micropores and mesopores measured by gas adsorption is P 1 cm 3 / g, where P 1 represents a number with a value between 0.5 and 1.5, Among them PD 90 The pore size is at least 3 nm and less than 12 nm; and Based on P 1 The micropore volume fraction is 0.43 to 0.85; and (b) a plurality of nanometer-sized elemental silicon domains located within the pores of the porous carbon framework, wherein the particulate material comprises from 25% to 65% by weight silicon, and wherein the particulate material comprises a percentage of surface silicon as a proportion of total silicon of at least 20 wt % as determined by thermogravimetric analysis (TGA) according to the formula: Y = 1.875 × [(M max – M min ) / M f ] ×100% where Y is the percentage of surface silicon as a proportion of total silicon, M max is the maximum mass of the granular material measured in the temperature range of 550 ºC to 650 ºC, M min is the minimum mass of the particulate material at a temperature above 150 ºC and below 500 ºC, and M f is the mass of the granular material when oxidation is complete at 1400 ºC.

2. The granular material according to claim 1, wherein P 1 In the range of 0.55 to 1.

4.

3. The granular material according to claim 1, wherein P 1 In the range of 0.6 to 1.

4.

4. The granular material according to claim 1, wherein P 1 In the range of 0.6 to 1.

3.

5. The granular material of claim 1, wherein P 1 In the range of 0.65 to 1.

3.

6. The granular material of claim 1, wherein P 1 In the range of 0.65 to 1.

2.

7. The granular material of claim 1, wherein P 1 In the range of 0.7 to 1.

2.

8. The granular material of claim 1, wherein P 1 In the range of 0.7 to 1.

1.

9. The granular material of claim 1, wherein P 1 In the range of 0.7 to 1.

10. The granular material of claim 1, wherein P 1 In the range of 0.75 to 0.

95.

11. The particulate material of claim 1, wherein the PD of the porous carbon skeleton is 90 The pore diameter is in the range of 3.5 to 10 nm.

12. The particulate material of claim 1, wherein the PD of the porous carbon skeleton is 90 The pore diameters range from 3.8 to 8 nm.

13. The particulate material of claim 1, wherein the PD of the porous carbon skeleton is 90 The pore diameter is in the range of 4 to 6 nm.

14. The particulate material of claim 1, wherein the PD of the porous carbon skeleton is 75 The pore size does not exceed 10 nm.

15. The particulate material of claim 1, wherein the PD of the porous carbon skeleton is 75 The pore diameter does not exceed 8 nm.

16. The particulate material of claim 1, wherein the PD of the porous carbon skeleton is 75 The pore diameter does not exceed 6 nm.

17. The particulate material of claim 1, wherein the PD of the porous carbon skeleton is 75 The pore diameter does not exceed 4 nm.

18. The particulate material of claim 1, wherein the PD of the porous carbon skeleton is 50 The pore diameter is in the range of 1 to 2 nm.

19. The particulate material of claim 1, wherein the PD of the porous carbon skeleton is 50 The pore diameter is in the range of 1 to 1.9 nm.

20. The particulate material of claim 1, wherein the PD of the porous carbon framework 50 The pore diameter is in the range of 1.1 to 1.8 nm.

21. The particulate material of claim 1, wherein the PD of the porous carbon framework 50 The pore diameter is in the range of 1.1 to 1.7 nm.

22. The particulate material of claim 1, wherein the PD of the porous carbon framework 50 The pore diameter is in the range of 1.2 to 1.6 nm.

23. The particulate material of claim 1, wherein the PD of the porous carbon framework 30 The pore diameter does not exceed 1.6 nm.

24. The particulate material of claim 1, wherein the PD of the porous carbon framework 30 The pore diameter does not exceed 1.5 nm.

25. The particulate material of claim 1, wherein the PD of the porous carbon framework 30 The pore diameter does not exceed 1.4 nm.

26. The particulate material of claim 1, wherein the PD of the porous carbon framework 30 The pore diameter does not exceed 1.3 nm.

27. The particulate material of claim 1, wherein the PD of the porous carbon framework 30 The pore diameter does not exceed 1.2 nm.

28. The particulate material of claim 1, wherein the PD of the porous carbon framework 30 The pore diameter does not exceed 1.1 nm.

29. The particulate material of claim 1, wherein the PD of the porous carbon framework 30 The pore size does not exceed 1 nm.

30. The particulate material of claim 1, wherein the PD of the porous carbon framework 30 The pore diameter is at least 0.6 nm.

31. The particulate material of claim 1, wherein the PD of the porous carbon framework 30 The pore diameter is at least 0.7 nm.

32. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.45 to 0.85 based on the total volume of micropores and mesopores.

33. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.48 to 0.8 based on the total volume of micropores and mesopores.

34. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.5 to 0.78 based on the total volume of micropores and mesopores.

35. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.51 to 0.76 based on the total volume of micropores and mesopores.

36. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.52 to 0.74 based on the total volume of micropores and mesopores.

37. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.54 to 0.72 based on the total volume of micropores and mesopores.

38. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.6 to 0.79 based on the total volume of micropores and mesopores.

39. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.6 to 0.78 based on the total volume of micropores and mesopores.

40. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.6 to 0.76 based on the total volume of micropores and mesopores.

41. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.6 to 0.74 based on the total volume of micropores and mesopores.

42. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in a range of 0.6 to 0.72 based on the total volume of micropores and mesopores.

43. The particulate material of claim 1, wherein the porous carbon framework has a micropore volume fraction in the range of 0.6 to 0.7 based on the total volume of micropores and mesopores.

44. The particulate material of claim 1, wherein the total volume of the micropores in the porous carbon framework is at least 0.36 cm 3 / g.

45. The particulate material of claim 1, wherein the total volume of the micropores in the porous carbon framework is at least 0.38 cm 3 / g.

46. ​​The particulate material of claim 1, wherein the total volume of the micropores in the porous carbon framework is at least 0.40 cm 3 / g.

47. The particulate material of claim 1, wherein the total volume of the micropores in the porous carbon framework is at least 0.42 cm 3 / g.

48. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 5 nm or less is at least 0.

8.

49. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 5 nm or less is at least 0.

82.

50. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 5 nm or less is at least 0.

84.

51. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 5 nm or less is at least 0.

86.

52. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 5 nm or less is at least 0.

88.

53. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 5 nm or less is at least 0.

9.

54. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 10 nm or less is at least 0.

9.

55. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 10 nm or less is at least 0.

92.

56. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 10 nm or less is at least 0.

94.

57. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 10 nm or less is at least 0.

96.

58. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 20 nm or less is at least 0.

94.

59. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 20 nm or less is at least 0.

96.

60. The particulate material of claim 1, wherein the volume fraction of pores having a pore size of 20 nm or less is at least 0.

98.

61. The particulate material of claim 1, wherein the porous carbon framework has a BET surface area of ​​1200 to 3000 m 2 / g.

62. The particulate material of claim 1 comprising 26% to 65% silicon by weight.

63. The particulate material of claim 1 comprising 28% to 65% silicon by weight.

64. The particulate material of claim 1 comprising 30% to 65% silicon by weight.

65. The particulate material of claim 1 comprising 32% to 60% silicon by weight.

66. The particulate material of claim 1 comprising 34% to 60% silicon by weight.

67. The particulate material of claim 1 comprising 36% to 60% silicon by weight.

68. The particulate material of claim 1 comprising 38% to 58% silicon by weight.

69. The particulate material of claim 1 comprising 40% to 58% silicon by weight.

70. The particulate material of claim 1 comprising 42% to 56% silicon by weight.

71. The particulate material of claim 1 comprising 44 to 54 weight percent silicon.

72. The particulate material of claim 1, wherein the porous carbon framework is a hard carbon framework.

73. The particulate material of claim 1, wherein the porous carbon framework is obtained by pyrolysis of a carbon-containing precursor.

74. The particulate material of claim 1, wherein the porous carbon framework comprises at least 80% carbon by weight.

75. The particulate material of claim 1, wherein the porous carbon framework comprises at least 90% carbon by weight.

76. The particulate material of claim 1, wherein the porous carbon framework comprises at least 95% carbon by weight.

77. The particulate material of claim 1, wherein the porous carbon framework comprises at least 98% carbon by weight.

78. The particulate material of claim 1, wherein the porous carbon framework comprises at least 99% carbon by weight.

79. The particulate material of claim 1, wherein the weight ratio of silicon to the porous carbon framework is between [0.50×P 1 to 1.9×P 1 ]:

1.

80. The particulate material of claim 1, wherein the weight ratio of silicon to the porous carbon framework is between [0.7×P 1 to 1.8×P 1 ]:

1.

81. The particulate material of claim 1, wherein the total oxygen content of the composite particles is less than 5% by weight.

82. The particulate material of claim 1, wherein the composite particles have a combined carbon and silicon content of at least 90% by weight.

83. The particulate material of claim 1, wherein the percentage of surface silicon as a proportion of total silicon is at least 22 weight percent as determined by thermogravimetric analysis (TGA).

84. The particulate material of claim 1, wherein the percentage of surface silicon as a proportion of total silicon is at least 25 weight percent as determined by thermogravimetric analysis (TGA).

85. The particulate material of claim 1, wherein the percentage of surface silicon as a proportion of total silicon is at least 30 weight percent as determined by thermogravimetric analysis (TGA).

86. The particulate material of claim 1, wherein the percentage of surface silicon as a proportion of total silicon is at least 35 weight percent as determined by thermogravimetric analysis (TGA).

87. The particulate material of claim 1, wherein the percentage of surface silicon as a proportion of total silicon is at least 40 weight percent as determined by thermogravimetric analysis (TGA).

88. The particulate material of claim 1, wherein the percentage of surface silicon as a proportion of total silicon is at least 45 weight percent as determined by thermogravimetric analysis (TGA).

89. The particulate material of claim 1, wherein no more than 10 weight percent of the silicon is macrophase silicon as determined by thermogravimetric analysis (TGA).

90. The particulate material of claim 1, wherein no more than 8 weight percent of the silicon is macrophase silicon as determined by thermogravimetric analysis (TGA).

91. The particulate material of claim 1, wherein no more than 6 weight percent of the silicon is macrophase silicon as determined by thermogravimetric analysis (TGA).

92. The particulate material of claim 1, wherein no more than 5 weight percent of the silicon is macrophase silicon as determined by thermogravimetric analysis (TGA).

93. The particulate material of claim 1, wherein no more than 4 weight percent of the silicon is macrophase silicon as determined by thermogravimetric analysis (TGA).

94. The particulate material of claim 1, wherein no more than 3 weight percent of the silicon is macrophase silicon as determined by thermogravimetric analysis (TGA).

95. The particulate material of claim 1, wherein no more than 2 weight percent of the silicon is macrophase silicon as determined by thermogravimetric analysis (TGA).

96. The particulate material of claim 1, wherein no more than 1.5 weight percent of the silicon is macrophase silicon as determined by thermogravimetric analysis (TGA).

97. The particulate material of claim 1, wherein the D of the composite particles 50 Particle sizes range from 1 to 30 µm.

98. The particulate material of claim 1, wherein the D of the composite particles 10 The particle size is at least 0.5 µm.

99. The particulate material of claim 1, wherein the D of the composite particles 10 The particle size is at least 0.8 µm.

100. The granular material of claim 1, wherein the D of the composite particles 10 The particle size is at least 1 µm.

101. The granular material of claim 1, wherein the D of the composite particles 10 The particle size is at least 1.5 µm.

102. The granular material of claim 1, wherein the D of the composite particles 10 The particle size is at least 2 µm.

103. The granular material of claim 1, wherein the D of the composite particles 90 Particle size does not exceed 50 µm.

104. The particulate material of claim 1, wherein the D of the composite particles 90 Particle size does not exceed 40 µm.

105. The granular material of claim 1, wherein the D of the composite particles 90 Particle size does not exceed 30 µm.

106. The granular material of claim 1, wherein the D of the composite particles 90 Particle size does not exceed 25 µm.

107. The particulate material of claim 1, wherein the D of the composite particles 90 Particle size does not exceed 20 µm.

108. The granular material of claim 1, wherein the D of the composite particles 90 Particle size does not exceed 15 µm.

109. The particulate material of claim 1, wherein the composite particles have a BET surface area of ​​no more than 100 m 2 / g.

110. The particulate material of claim 1, wherein the composite particles have a BET surface area of ​​no more than 80 m 2 / g.

111. The particulate material of claim 1 , wherein the composite particles have a BET surface area of ​​no more than 60 m 2 / g.

112. The particulate material of claim 1, wherein the composite particles have a BET surface area of ​​no more than 50 m 2 / g.

113. The particulate material of claim 1, wherein the composite particles have a BET surface area of ​​no more than 40 m 2 / g.

114. The particulate material of claim 1, wherein the composite particles have a BET surface area of ​​no more than 30 m 2 / g.

115. The particulate material of claim 1, wherein the composite particles have a BET surface area of ​​no more than 25 m 2 / g.

116. The particulate material of claim 1, wherein the composite particles have a BET surface area of ​​no more than 20 m 2 / g.

117. The particulate material of claim 1, wherein the composite particles have a BET surface area of ​​no more than 15 m 2 / g.

118. The particulate material of claim 1, wherein the composite particles have a BET surface area of ​​no more than 10 m 2 / g.

119. The particulate material of claim 1 , wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.2 cm 3 / g.

120. The particulate material of claim 1, wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.15 cm 3 / g.

121. The particulate material of claim 1, wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.1 cm 3 / g.

122. The particulate material of claim 1 , wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.08 cm 3 / g.

123. The particulate material of claim 1, wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.06 cm 3 / g.

124. The particulate material of claim 1, wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.04 cm 3 / g.

125. The particulate material of claim 1 , wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.02 cm 3 / g.

126. The particulate material of claim 1 , wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.015 cm 3 / g.

127. The particulate material of claim 1 , wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.012 cm 3 / g.

128. The particulate material of claim 1, wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.010 cm 3 / g.

129. The particulate material of claim 1 , wherein the volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen adsorption, is less than 0.008 cm 3 / g.

130. The particulate material of claim 1, wherein the composite particles comprise a lithium ion permeable coating at least partially covering an outer surface of the particles.

131. The particulate material of claim 1, wherein the composite particle comprises a lithium ion permeable coating completely covering the outer surface of the particle.

132. The particulate material of claim 1, comprising a passivated silicon surface.

133. The particulate material of any one of claims 1 to 132, wherein at least 30 weight percent of the silicon is surface silicon as determined by thermogravimetric analysis (TGA); wherein no more than 5 weight percent of the silicon is macrophase silicon as determined by thermogravimetric analysis (TGA); and wherein the BET surface area of ​​the composite particles is no more than 30 m 2 / g.

134. A composition comprising the particulate material defined in any one of claims 1 to 133 and at least one other component selected from: (i) a binder; (ii) a conductive additive; and (iii) a further particulate electroactive material.

135. The composition of claim 134 comprising at least one additional particulate electroactive material.

136. The composition of claim 135 comprising 20% ​​to 70% by weight of the at least one additional particulate electroactive material.

137. The composition of claim 135 comprising 25% to 65% by weight of the at least one additional particulate electroactive material.

138. The composition of claim 135 comprising 30% to 60% by weight of the at least one additional particulate electroactive material.

139. The composition of claim 135, comprising 15 to 60 weight percent of the particulate material, based on the total dry weight of the composition.

140. The composition of claim 135, comprising 20% ​​to 50% by weight of the particulate material, based on the total dry weight of the composition.

141. The composition of claim 135, comprising 30% to 50% by weight of the particulate material, based on the total dry weight of the composition.

142. The composition of claim 135, wherein the at least one additional particulate electroactive material is selected from the group consisting of graphite, hard carbon, silicon, tin, germanium, aluminum, and lead.

143. The composition of claim 134, wherein the composition is free of additional particulate electroactive material.

144. The composition of claim 143, comprising at least 50% by weight of the particulate material, based on the total dry weight of the composition.

145. The composition of claim 143, comprising at least 60% by weight of the particulate material, based on the total dry weight of the composition.

146. The composition of claim 143, comprising at least 70% by weight of the particulate material, based on the total dry weight of the composition.

147. The composition of claim 143, comprising at least 80% by weight of the particulate material, based on the total dry weight of the composition.

148. The composition of claim 143, comprising at least 90% by weight of the particulate material, based on the total dry weight of the composition.

149. The composition of any one of claims 134 to 148, comprising a binder.

150. The composition of any one of claims 134 to 148, comprising one or more conductive additives.

151. An electrode comprising the particulate material defined in any one of claims 1 to 133 in electrical contact with a current collector.

152. An electrode according to claim 151, wherein the particulate material is in the form of a composition as defined in any one of claims 134 to 150.

153. A rechargeable metal ion battery, comprising: (i) an anode, wherein the anode comprises the electrode of claim 151 or claim 152; (ii) a cathode comprising a cathode active material capable of releasing and reabsorbing metal ions; as well as (iii) an electrolyte between the anode and the cathode.

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