Method for preparing electroactive materials for metal ion batteries

Abstract

This invention provides a method for producing particulate materials with high electrochemical capacity suitable for use as anode active materials in rechargeable metal-ion batteries. [Solution] In one embodiment, the present disclosure provides a method for producing a particulate material comprising a plurality of composite particles. The method comprises micropores and / or mesopores, and at least 20 μm in diameter. 50 The method comprises preparing a particulate porous carbon skeleton with a particle size, depositing an electroactive material selected from silicon and its alloys into the micropores and / or mesopores of the porous carbon skeleton using a chemical vapor impregnation process in a fluidized bed reactor to obtain intermediate particles, and grinding the intermediate particles to obtain composite particles. This method treats individual micron-scale powders as mini-impregnation substrates, reduces the length scale characteristic of precursor diffusion and reaction, and facilitates the transition to continuous processing for mass production.

Description

[Technical Field]

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

[0002] Rechargeable metal-ion batteries are widely used in portable electronic devices such as mobile phones and laptop computers, and their application in electric or hybrid vehicles is increasing. A rechargeable metal-ion battery generally includes an anode layer, a cathode layer, an electrolyte for transporting metal ions between the anode and cathode layers, and an electrically insulating porous separator positioned between the anode and cathode. The cathode typically includes a metal current collector comprising a layer of metal ions containing a metal oxide composite material, and the anode typically includes a metal current collector comprising a layer of electroactive material defined herein as a material capable of inserting and releasing metal ions during charging and discharging of the battery. To avoid misunderstanding, the terms “cathode” and “anode” are used herein in the sense that the battery is loaded such that the cathode becomes the positive electrode and the anode becomes the negative electrode. When a metal-ion battery is charged, metal ions are transported from the metal-ion-containing cathode layer through the electrolyte to the anode and inserted into the anode material. In this specification, the term “battery” is used to refer to both a device containing a single anode and a single cathode, and a device containing multiple anodes and / or multiple cathodes.

[0003] We are interested in improving the gravimetric and / or volumetric capacity of rechargeable metal-ion batteries. While the use of lithium-ion batteries has already brought about considerable improvements compared to other battery technologies, there is still room for further development. To date, commercially available lithium-ion batteries have been primarily limited to the use of graphite as the anode active material. When a graphite anode is charged, lithium is inserted between the graphite layers, and empirically, Li... xThis forms a C6 material (where x is greater than 0 and less than or equal to 1). As a result, graphite has a maximum theoretical capacity of 372 mAh / g in lithium-ion batteries, with practical capacities being slightly lower (approximately 340 mAh / g to 360 mAh / g). Other materials such as silicon, tin, and germanium can insert lithium at significantly higher capacities than graphite, but they are not yet widely used commercially because it is difficult to maintain sufficient capacity over many charge-discharge cycles.

[0004] In particular, silicon has been recognized as a promising substitute for graphite in the manufacture of rechargeable metal-ion batteries with high gravimetric and volumetric capacities due to its very high capacity relative to lithium (see, for example, Non-Patent Document 1). At room temperature, silicon has a theoretical maximum specific capacity of approximately 3600 mAh / g in lithium-ion batteries. 15 (Based on Si4). However, the use of silicon as an anode material is complicated due to the large volume change during charging and discharging.

[0005] When lithium is inserted into bulk silicon, the volume of the silicon material increases significantly, and when the silicon is lithified to its maximum capacity, it increases to 400% of its original volume. Then, as charge-discharge cycles are repeated, large mechanical stresses are generated in the silicon material, leading to fracture and delamination of the silicon anode material. The volume contraction of silicon particles during delithiation can result in a loss of electrical contact between the anode material and the current collector. Further complicating matters is that the solid electrolyte interface (SEI) layer formed on the silicon surface does not possess sufficient mechanical durability to accommodate the expansion and contraction of the silicon. As a result, the newly exposed silicon surface further decomposes the electrolyte, increasing the thickness of the SEI layer, and... Lithium will be consumed irreversibly. Collectively, these defect mechanisms result in an unacceptable loss of electrochemical capacity over consecutive charge-discharge cycles.

[0006] Numerous approaches have been proposed to overcome the volume changes and related problems observed when charging silicon-containing anodes. The most widespread approach to address irreversible capacity loss in silicon-containing anodes is to use silicon microstructured in some form as an electroactive material. Micro-silicon structures with cross-sections of less than approximately 150 nm, such as silicon films and silicon nanoparticles, have been reported to be more tolerant of volume changes during charging and discharging compared to silicon particles in the micron size range. However, none of these are particularly suitable for commercial-scale application without modification of their form. Nanoscale particles are difficult to manufacture and handle, and silicon films do not provide sufficient bulk capacity. For example, nanoscale particles tend to form aggregates, making it difficult to effectively disperse them within the anode material matrix. Furthermore, the formation of nanoscale particle aggregates results in unacceptable capacity loss during repeated charge-discharge cycles.

[0007] It is also generally known that electroactive materials such as silicon can be deposited within the pores of porous carrier materials such as activated carbon. These composite materials offer some of the beneficial charge-discharge properties of nanoscale silicon particles while avoiding the difficulties in handling nanoparticles. For example, Guo et al. (Non-Patent Literature 2) have shown that a porous carbon substrate can be uniformly distributed and deposited within the pore structure of the substrate. We disclose a silicon-carbon composite material that provides a conductive framework with deposited silicon nanoparticles. The formation of SEI during the initial charge cycle is limited to the remaining pore volume so that the remaining silicon is not exposed to the electrolyte in subsequent charge cycles. This composite material shows improved capacity retention over multiple charge cycles, although the initial capacity in mAh / g of the composite material has been shown to be significantly lower than that of silicon nanoparticles alone.

[0008] Patent Document 1 discloses an active material comprising a carbon-based scaffold having smaller pores branching from a number of larger pores. The electroactive material (e.g., 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] It has been found that the performance of composite materials containing a porous carbon skeleton and an electroactive material such as silicon located within the porous carbon skeleton can be optimized by using a porous carbon skeleton with a specific pore structure and a controlled ratio of electroactive material to effective pore volume. For the desired end applications of these composite materials in metal-ion batteries, a small particle size (e.g., less than 20 μm) is required. 50 These composite materials are considered beneficial. However, it is difficult to manufacture these composite materials efficiently and steadily, especially on a large scale for commercial use. It is difficult to control the deposition of electroactive materials so that they are deposited at desired locations within the pores of a porous carbon skeleton. It is also difficult to control deposition when manufacturing products with a desired small particle size. The present invention aims to solve this problem.

[0010] Chemical vapor infiltration (CVI) is a process that uses a reactive gaseous precursor to infiltrate an additional phase into a porous substrate material. The porous substrate is placed on a perforated metal plate, and a mixture of a carrier gas and a gaseous precursor is passed through the porous substrate, which is held at a high temperature. The gaseous precursor chemically reacts at high temperatures within the pore structure of the substrate material and deposits on the inner surface of the pore spaces. The CVI process increases the density of the porous substrate material. CVI is particularly useful because the shape of the porous substrate is hardly altered. Furthermore, by controlling the purity of the reactive gaseous precursor, as well as the infiltration pressure and temperature, a high degree of uniformity can be achieved within the substrate.

[0011] Chemical vapor infiltration (CVI) has been found to be usable for depositing electroactive materials within microporous and / or mesoporous carbon materials having particle sizes of less than 20 μm to produce composite materials with desired electrochemical properties. In this invention, CVI specifically refers to a process in which a gaseous precursor of an electroactive material, such as silicon, is thermally decomposed on a surface, and the electroactive material is deposited on this surface in elemental form to form a gaseous byproduct. This gaseous byproduct can be deposited on the inner surface, in particular on the surface of the pore walls.

[0012] Typically, the low diffusivity of gaseous silicon precursors used in CVI of silicon compounds into micro and / or mesopore systems, or other gaseous precursors for other electroactive materials, means that a kinetically limited (surface reaction limited) deposition regime must be used. However, this presents many problems from a processing standpoint. The main problem is that in high-capacity / high-volume, continuous processing of large volumes of samples and reactor systems, it is difficult to ensure the high thermal and mass transfer uniformity necessary to maintain a uniform deposition rate with respect to reactor position, processing time, and particle pore system position. Therefore, it is difficult to use CVI to deposit electroactive materials into the pores of porous carbon skeletons on a commercially useful scale. There are no widespread commercial production routes using CVI as a deposition technique, particularly for processing powders in the size range of less than 20 μm.

[0013] Fluidized bed reactors (FBRs) can be used to perform chemically coupled material (CVI). FBRs have a wide range of applications in this industry. FBRs provide a means of highly efficient gas-solid contact while providing a uniform temperature distribution across the bed. This is mainly achieved by using a gas flow to fluidize the particles and bring all surfaces into contact with the reactive gas. FBRs address many of the aforementioned problems of mass transfer and heat transfer. Once fluidization is achieved, superior solid-solid and gas-solid mixing is observed, especially when compared to alternative powder processing solutions for CVI, such as fixed bed and rotary furnaces.

[0014] Particles can be classified into groups based on their size and density in relation to their fluidization behavior. These groups are known as Geldart's Group A, Group B, Group C, and Group D materials. Group A, Group B, and Group D materials can be fluidized with or without the presence of bubbles and slugging behavior, but Geldart's Group C includes materials with small size and low density, and due to the cohesive forces resulting from their small size, fluidization can be difficult. Carbon powders with small particle sizes can be considered Geldart's Group C materials.

[0015] As described in Non-Patent Document 3 by Vahlas et al., FBR-chemical vapor deposition (CVD), including CVI, has been used to deposit various catalytic metals and catalytic nonmetals onto porous and non-porous materials.

[0016] However, carbon powders smaller than 20 μm tend to form large aggregates when used in FBRs due to strong interparticle cohesive forces at this length scale. This is problematic because it can lead to fluidization as large, millimeter-sized aggregates rather than individual particles, resulting in issues related to mass transfer rates within the aggregates. Furthermore, the carbon powder may not fluidize at all; instead, channeling (rat-holes) may occur due to locally applied shear forces on the gas flow that are insufficient to break the interparticle cohesive forces (i.e., the gas does not pass through the powder bed but rather around it). For these reasons, FBRs have been considered unsuitable for use in processes involving carbon powders smaller than 20 μm. [Prior art documents] [Patent Documents]

[0017] [Patent Document 1] Japanese Patent Publication No. 2003-100284 [Non-patent literature]

[0018] [Non-Patent Document 1] Insertion Electrode Materials for Rechargeable Lithium Batteries, Winter, M. et al. in Adv. Mater. 1998, 10, No. 10 [Non-Patent Document 2] Journal of Materials Chemistry A, 2013, pp. 14075-14079 [Non-Patent Document 3] Principles and applications of CVD powder technology, Materials Science and Engineering R53 (2006) 1-72 [Overview of the Initiative] [Problems that the invention aims to solve]

[0019] This invention utilizes chemical vapor phase infiltration into a fluidized porous carbon powder to enable control of the kinetic and thermodynamic conditions of the infiltration reaction, ensuring that each porous carbon particle is exposed to a similar chemical and thermal environment. Essentially, this invention treats individual micron-scale powders as mini-infiltration substrates, reducing the length scales characteristic of precursor diffusion and reaction, and facilitating a transition to continuous processing for mass production. [Means for solving the problem]

[0020] In the first embodiment, the present invention is (a) containing micropores and / or mesopores, with at least 20 μm of D 50 To prepare a particulate porous carbon skeleton having a particle size, (b) In a fluidized bed reactor, an electroactive material selected from silicon, tin, aluminum, germanium, and their alloys is deposited in the micropores and / or mesopores of a porous carbon skeleton using a chemical vapor impregnation process to obtain intermediate particles. (c) Crushing intermediate particles to obtain composite particles, The present invention provides a method for producing particulate material containing multiple composite particles, including [specific particle name].

[0021] Therefore, the present invention provides a functional nanostructure containing an electroactive material by utilizing the advantages of CVI to deposit the electroactive material within the pores of a porous carbon skeleton. This method also utilizes the advantages of using FBR to perform CVI. In this method, at least 20 μm of D 50 Since a particulate porous carbon skeleton with a particle size is used as the starting material, the difficulty of using FBR with carbon powder having a small particle size is also avoided. The grinding step means that this method can be used to provide composite particles with a reduced particle size compared to the starting material, which is considered useful for desired end applications in metal-ion batteries. In particular, composite particles in these size ranges are ideally suited for use in composite film negative electrodes (i.e., "anodes") for metal-ion batteries because they are dispersible in slurries, structurally robust, and retain their capacity over repeated charge-discharge cycles. Such composite films typically have a thickness of less than 100 μm or less than 50 μm, and smaller particle sizes also help to achieve denser films with uniform thickness. Thus, the method of the present invention provides an effective method for producing composite particles suitable for large-scale commercial use.

[0022] It may seem counterintuitive to use CVI to fabricate intermediate composite particles in FBR and then grind these intermediate particles. In particular, it has been thought that the grinding process could damage the functional nanostructure of the intermediate particles obtained by the CVI process, i.e., the electroactive material deposited within the pores of the carbon skeleton. However, we have shown that because the damage is on a relatively micrometer scale compared to the nanometer scale of the functional units of the composite particles, grinding can occur without causing a significant level of damage. We discovered that because the carbon skeleton contains micropores and / or mesopores, the desired properties are retained in the product even after grinding.

[0023] In the method of the present invention, the properties of the porous carbon skeleton starting material can be selected to impart a desired set of properties to the final product. For example, by selecting a porous carbon skeleton to have a specific pore structure, the grinding process can be carried out without causing significant damage to the pore structure, thus enabling the production of products having a specific micropore and / or mesopore structure.

[0024] The electroactive material can be silicon or tin. The electroactive material is preferably silicon. The electroactive material may optionally contain small amounts of one or more dopants. Suitable dopants include boron and phosphorus, other n-type or p-type dopants, or nitrogen. When silicon is the electroactive material, it can also be doped with small amounts of one or more other electroactive materials, such as tin, aluminum, and germanium. The dopants are preferably present in a total amount of 2% by weight or less relative to the total amount of the electroactive material and dopants (there may be more than one).

[0025] To avoid misunderstanding, the term “particle size” as used herein refers to the equivalent diameter (ESD), i.e., the diameter of a sphere having the same volume as a given particle, where the particle volume is understood to include the volume of pores within the particle. 50 " and "D 50The term "particle diameter" refers to the volume-based median particle diameter, i.e., the diameter below which 50% by volume of the particle population is present. As used herein, "D 10 " and "D 10 The term "particle diameter" refers to the volume-based 10th percentile median particle diameter, i.e., the diameter below which 10% by volume of the particle population is present. As used herein, "D 90 " and "D 90 The term "particle diameter" refers to the volume-based 90th percentile median particle diameter, i.e., the diameter below which 90% by volume of the particle population is present.

[0026] The term "D n " used herein to define the particle size distribution is distinguished from the term "PD n " used herein to define the pore size distribution. The general term "PD n pore diameter" used herein refers to the volume-based nth percentile pore diameter with respect to the total volume of micropores and mesopores. For example, the term "D 50 pore diameter" used herein refers to the pore diameter below which 50% of the total micropore and mesopore volume represented by P1 is present).

[0027] To avoid misunderstanding, any macropore volume (pore diameter greater than 50 nm) is not considered for the purpose of determining the PD n value.

[0028] The particle diameter and particle size distribution can be determined by a conventional laser diffraction method in accordance with ISO 13320:2009. Laser diffraction is based on the principle that particles scatter light at angles that vary according to the size of the particles, and a collection of particles generates a scattered light pattern defined by the intensity and angle that can be correlated to the particle size distribution. To determine the particle size distribution quickly and reliably, many laser diffraction devices are commercially available. Unless otherwise specified, the particle size distribution measurement values defined or reported herein are the conventional Mal The particle size distribution was measured using a Malvern Mastersizer® 3000 particle size analyzer. This Malvern Mastersizer® 3000 analyzer operates by projecting a helium-neon gas laser beam through a transparent cell containing target particles suspended in an aqueous solution. The light beam striking the particles is scattered at an angle inversely proportional to the particle diameter. A photodetector array measures the intensity of the light at several predetermined angles, and the intensities measured at various angles are processed by a computer using standard theoretical principles to determine the particle size distribution. The laser diffraction values ​​reported herein are obtained using a wet dispersion of particles in distilled water. The refractive index of the particles is 3.50, and the refractive index of the dispersant is 1.33. Assume it is 0. The particle size distribution is calculated using the Mie scattering model.

[0029] Porous metallic skeleton The porous carbon skeleton has at least 20 μm of D 50 It has a particle size. Therefore, the porous carbon skeleton can be easily used in FBR. The porous carbon skeleton can optionally have a particle size in the range of 20 μm to 1000 μm, or 30 μm to 500 μm, or 60 μm to 150 μm. 50 The particle size is as follows: The porous carbon skeleton is optionally D, with a diameter of at least 30 μm, at least 40 μm, or at least 50 μm, or at least 60 μm, or at least 70 μm, or at least 80 μm. 50 The particle size is determined by the porous carbon skeleton, which may be 1000 μm or less, or 500 μm or less, or 250 μm or less, or 150 μm or less. 50 It has a particle size.

[0030] The porous carbon skeleton may optionally have a diameter of at least 5 μm, at least 15 μm, at least 40 μm, or at least 50 μm, or at least 60 μm, or at least 70 μm. 10 It has a particle size. D 10 By maintaining particle sizes above these values, the presence of numerous carbon skeletons with small particle sizes that might be unsuitable for FBRs is advantageously avoided.

[0031] The porous carbon skeleton may optionally have a diameter of 1500 μm or less, or 1000 μm or less, or 750 μm or less, or 500 μm or less, or 200 μm or less. 90 The particle size is determined as follows: The porous carbon skeleton is optionally 1550 μm or less, or 1050 μm or less, or 800 μm or less, or 550 μm or less, or 250 μm or less. 98 It has a particle size. D 90 Particle size and / or D 98 By maintaining particle sizes below these values, the presence of numerous carbon skeletons with larger particle sizes that may be unsuitable for CVI is advantageously avoided.

[0032] For example, the porous carbon skeleton has at least 15 μm of D 10 Particle size, D of at least 20 μm 50 Particle size, and D of 200 μm or less 90 It can have a particle size. The porous carbon skeleton has at least 5 μm of D 10 Particle size, D in the range of 20 μm to 250 μm 50 D particles with a diameter of 750 μm or less 90 Particle size, and D of particles smaller than 1000 μm 98 It can have a particle size. The porous carbon skeleton has at least 5 μm of D 10 Particle size, D in the range of 20 μm to 200 μm 50 D particles with a diameter of 500 μm or less 90 Particle size, and D of 800 μm or less 98 It can have a particle size. The porous carbon skeleton has at least 40 μm of D 10 Particle size, D in the range of 60 μm to 150 μm 50 Particle size, and D of 200 μm or less 90 Particle size, and D250μm or less 98 It can have a particle size.

[0033] The porous carbon skeleton preferably has a narrow particle size distribution span. For example, a particle size distribution span ((D 90 -D 10 ) / D 50The (defined as) is preferably 5 or less, more preferably 4 or less, more preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. Maintaining a narrow particle size distribution span makes it easier to achieve the steady deposition of electroactive material into the pores of the carbon skeleton.

[0034] The porous carbon skeleton preferably comprises a three-dimensionally interconnected network of pores, including a combination of micropores and / or mesopores, and optionally a small amount of macropores. In accordance with IUPAC terminology, the term "micropore" herein refers to pores with a diameter of less than 2 nm, the term "mesopore" herein refers to pores with a diameter of 2 nm to 50 nm, and the term "macropore" herein refers to pores with a diameter greater than 50 nm.

[0035] Any references in this specification to the volumes of micropores, mesopores, and macropores within a porous carbon skeleton, as well as any references to the pore volume distribution within a porous carbon skeleton, are not to be used alone (i.e., This refers to the internal pore volume of a porous carbon skeleton (in the absence of electroactive materials or other materials that occupy part or all of the pore volume).

[0036] In this specification, the volume ratio of micropores (relative to the total volume of micropores and mesopores) is denoted by φ. a The volume ratio of mesopores (relative to the total volume of micropores and mesopores) is represented by the sign φ. b Since it is represented as φ a +φ b It will be understood that this equals 1.

[0037] Porous carbon skeletons are characterized by pore volumes in the form of micropores and / or mesopores. In this specification, the total volume of micropores and mesopores (i.e., the total pore volume in the range of 0 nm to 50 nm) is defined as P1 cm 3 This can be expressed as / g, where P1 represents a dimensionless natural number. The value of P1 is also used to correlate the effective pore volume in the porous carbon skeleton with the weight ratio of the electroactive material to the porous carbon skeleton in the final product.

[0038] To avoid misunderstanding, as used herein, P1 refers to the pore volume of the porous carbon skeleton measured alone, i.e., in the absence of silicon or other materials occupying the pores of the porous carbon skeleton. Similarly, any reference herein to the volumes of micropores, mesopores, and macropores in the porous carbon skeleton, as well as any reference to the distribution of pore volumes within the porous carbon skeleton, refers to the internal pore volume of the porous carbon skeleton alone (i.e., in the absence of silicon or other materials occupying the pore volume).

[0039] P1 can have a value in the range of 0.4 to 2.5. Therefore, the porous carbon skeleton is at least 0.4 cm 3 / g, and a maximum of 2.5cm 3 It can have a pore volume of / g.

[0040] P1 can have a value in the range of 0.4 to 0.6. This corresponds to a small pore volume in the form of micropores and / or mesopores.

[0041] Alternatively, P1 can have a value of at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, or at least 0.8, or at least 0.85, or at least 0.9, or at least 0.95, or at least 1, or at least 1.05, or at least 1.1, or at least 1.2. The use of a high-porosity carbon skeleton is advantageous because it allows more silicon to be accommodated within the pore structure, and it has been found that a high-porosity carbon skeleton, whose pore volume is mainly in the form of micropores and even smaller mesopores, has sufficient strength to adapt to the volume expansion of the electroactive material without the porous carbon skeleton breaking or otherwise degrading.

[0042] P1 can have a value of 2.5 or less, or 2.2 or less, or 2 or less, or 1.8 or less, or 1.6 or less, or 1.5 or less, or 1.4 or less, or 1.3 or less, or 1.2 or less. Preferably, the internal pore volume of the porous carbon skeleton is limited to a value such that the increase in the fragility of the porous carbon skeleton outweighs the benefit of an increased pore volume that accommodates a larger amount of electroactive material.

[0043] The value of P1 can be in the range of 0.4 to 2.5, or 0.6 to 2.5, or 0.7 to 2, or 0.7 to 1.2.

[0044] Volume fraction of micropores (φ a ) can be at least 0.1, or in the range of 0.1 to 0.9. a Preferably, it is greater than 0.5, more preferably greater than 0.6, more preferably greater than 0.7, and more preferably greater than 0.8.

[0045] Pore ​​fractions with diameters in the larger mesopore range can be advantageous because they facilitate the access of electrolytes to the electroactive material in the final product. Therefore, 10 nm to 50 Pores having diameters in the range of nm (i.e., larger mesopores) can optionally constitute at least 1%, at least 2%, at least 5%, or at least 10% of the total micropore and mesopore volume of the porous carbon skeleton.

[0046] The pore size distribution of a porous carbon skeleton can be unimodal, bimodal, or multimodal. As used herein, the term "pore size distribution" refers to the distribution of pore sizes relative to the cumulative total internal pore volume of the porous carbon skeleton. Bimodal or multimodal pore size distributions may be preferred because the proximity of the smallest pores to the larger diameter pores provides the advantage of efficient ion transport through the porous network to the electroactive material. Therefore, composite particles made from porous carbon skeletons exhibit improved rate performance due to their high ion diffusivity.

[0047] Preferably, the bimodal or multimodal pore size distribution includes peak pore sizes in the micropore range and peak pore sizes in the mesopore range, which differ from each other by 5 to 20 times, more preferably by about 10 times. For example, a porous carbon skeleton may have a bimodal pore size distribution with a peak at 1.5 nm and a peak at 15 nm. A porous carbon skeleton may have a bimodal pore size distribution with a peak at 2 nm and a peak at 20 nm. A porous carbon skeleton may have a bimodal pore size distribution with a peak at 1.2 nm and a peak at 12 nm.

[0048] The total volume of micropores and mesopores, as well as the pore size distribution of micropores and mesopores, were determined using the rapid solid density functional theory (QSDFT) according to the standard methodology specified in ISO 15901-2 and ISO 15901-3, at 77K for 10 -6 This is determined using nitrogen gas adsorption up to a relative pressure p / p0. Nitrogen gas adsorption is a technique for characterizing the porosity and pore size distribution of a material by condensing a gas within the pores of a solid. As the pressure is increased, the gas initially condenses in the pores with the smallest diameter, and the pressure is increased until a saturation point is reached where all pores are filled with liquid. Then, the nitrogen gas pressure is gradually decreased to evaporate the liquid from the system. Pore volume and pore size distribution can be determined by analyzing the adsorption isotherms and desorption isotherms, as well as the hysteresis between them. Suitable instruments for measuring pore volume and pore size distribution by nitrogen gas adsorption include the TriStar II porosity analyzer and TriStar II, available from Micromeritics Instrument Corporation in the United States. Examples include the Plus porosity analyzer and the Autosorb IQ porosity analyzer available from Quantachrome Instruments.

[0049] Nitrogen gas adsorption is effective for measuring pore volume and pore size distribution of pores with a diameter of up to 50 nm, but becomes unreliable for pores with much larger diameters. Therefore, for the purposes of this invention, nitrogen adsorption is used to determine pore volume and pore size distribution only for pores with a diameter of 50 nm or less. As described above, the value of P1 is determined considering only pores with a diameter of 50 nm or less (i.e., only micropores and mesopores), and similarly, PD n , and φ a , φ b , φ 20 , φ 10 The values ​​of φ5 (discussed below) are determined for the total volume of micropores and mesopores only.

[0050] Given the limitations of available analytical techniques, it is impossible to measure pore volume and pore size distribution across the entire range of micropores, mesopores, and macropores using a single method. When a porous carbon skeleton contains macropores, the volume of pores greater than 50 nm and up to 100 nm is P2 cm² as specified herein. 3 It is specified by a value of / g and measured by the mercury intrusion method. The P2 value relates to the pore volume of the porous carbon skeleton when measured alone, i.e., when there is no electroactive material or other material occupying the pores of the porous carbon skeleton.

[0051] To avoid misunderstanding, the P2 value refers to pores with a diameter between 50 nm and 100 nm. Only the volume of macropores with a maximum diameter of 100 nm is considered. That is, the value of P2 includes only the volume of macropores with a maximum diameter of 100 nm. Any pore volume measured by mercury intrusion at pore diameters of 50 nm or less is ignored for the purpose of determining the value of P2. Pore volumes measured by mercury intrusion at pores greater than 100 nm are assumed to be interparticle porosity for the purposes of this invention, and this pore volume is also not considered when determining the value of P2. As described above, nitrogen adsorption is used to characterize mesopores and micropores.

[0052] The mercury intrusion method is a technique for characterizing the porosity and pore size distribution of a material by applying various levels of pressure to a sample of material immersed in mercury. The pressure required to penetrate the pores of the sample with mercury is inversely proportional to the pore size. The values ​​obtained by the mercury intrusion method reported herein were obtained according to ASTM UOP578-11, with a surface tension γ of mercury at room temperature of 480 mN / m and a contact angle φ of 140°. The density of mercury at room temperature is 13.5462 g / cm³. 3 Many high-precision mercury intrusion devices are commercially available, such as the AutoPore IV series automatic mercury intrusion gauges from Micromeritics Instrument Corporation in the United States. For a complete report on mercury intrusion methods, refer to "Analytical Methods in Fine Particle Technology, 1997, Micromeritics Instrument Corporation" by PA Webb and C. Orr (ISBN 0-9656783-0).

[0053] The volume of macropores (i.e., the value of P2) is preferably smaller than the volumes of micropores and mesopores (i.e., the value of P1). While some macropores may be useful for facilitating electrolyte access to the pore network, the advantages of the present invention are substantially obtained by accommodating silicon in micropores and even smaller mesopores.

[0054] Therefore, according to the present invention, the total volume of macropores in a porous carbon skeleton is measured by the mercury intrusion method, P2cm 3 / g, where P2 preferably has a value of 0.2 × P1 or less, or 0.1 × P1 or less, or 0.05 × P1 or less, or 0.02 × P1 or less, or 0.01 × P1 or less, or 0.005 × P1 or less.

[0055] In preferred embodiments, P2 has a value of 0.3 or less, or 0.25 or less, or 0.20 or less, or 0.15 or less, or 0.1 or less, or 0.05 or less. As discussed above in relation to larger mesopores, small pore volume fractions in the macropore range may be advantageous in facilitating electrolyte access to the electroactive material in the final product.

[0056] The pore network optionally includes a hierarchical pore structure, i.e., a pore structure in which smaller pores branch off from larger pores and the pore diameters have a certain order.

[0057] It will be understood that intrusion methods such as gas adsorption and mercury intrusion are effective only for determining the pore volume of pores that are accessible to nitrogen or mercury from outside the porous carbon framework. The porosity values ​​(P1 and P2) specified herein are understood to refer to the volume of openings, i.e., pores that are accessible to fluid from outside the porous carbon framework. Completely enclosed pores that cannot be identified by nitrogen adsorption or mercury intrusion are not considered herein when specifying the porosity values. Similarly, any pore volume located in pores small enough to be below the detection limit by nitrogen adsorption is not considered in determining the value of P1.

[0058] The porous carbon skeleton may include crystalline carbon, amorphous carbon, or a mixture of amorphous and crystalline carbon. The porous carbon skeleton may be either a rigid carbon skeleton or a flexible carbon skeleton, and can preferably be obtained by known procedures including the thermal decomposition of a polymer or organic material.

[0059] As used herein, the term “hard carbon” refers to carbon atoms that are primarily composed of nanoscale polycyclic aromatic domains sp. 2 This refers to a disordered carbon matrix that takes on a hybrid state (three-way bonding). These polycyclic aromatic domains are cross-linked by chemical bonds, such as COC bonds. Because the polycyclic aromatic domains are chemically cross-linked with each other, hard carbon cannot be converted to graphite at high temperatures. The high G band (approximately 1600 cm⁻¹) in the Raman spectrum...-1 As is evident from the results, hard carbon has graphite-like properties. However, in the Raman spectrum, the high D band (approximately 1350 cm⁻¹) -1 As is evident from the above, carbon is not entirely like graphite.

[0060] The term "soft carbon" as used herein also refers to carbon atoms that are primarily polycyclic aromatic domains with dimensions in the range of 5 nm to 200 nm. 2 This refers to a disordered carbon matrix that takes on a hybrid state (three-way bonding). In contrast to hard carbon, the polycyclic aromatic domains in soft carbon are bonded by intermolecular forces rather than by chemical bonds. That is, soft carbon can graphitize at high temperatures. The porous carbon skeleton preferably has at least 50% sp when measured by XPS. 2 It contains hybrid carbon. For example, the porous carbon skeleton preferably contains 50% to 98% sp 2 Hybrid carbon, 55%~95% sp 2 Hybrid carbon, 60%~90% sp 2 Mixed carbon, or 70%-85% sp 2 It can contain hybrid carbon.

[0061] Various different materials can be used to produce a suitable porous carbon skeleton. Examples of organic materials that can be used include plant biomass, including lignocellulosic materials (such as coconut shells, rice husks, and wood), and fossil carbon sources such as coal. Examples of polymer materials that form a porous carbon skeleton by thermal decomposition include phenolic resins, novolac resins, pitch, melamine, polyacrylate, polystyrene, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers containing monomer units of acrylate, styrene, α-olefin, vinylpyrrolidone, and other ethylenically unsaturated monomers. Depending on the starting materials and the conditions of the thermal decomposition process, various different rigid carbon materials are available in this art.

[0062] To increase the volume of mesopores and micropores, a chemical or gas activation process can be performed on the porous carbon skeleton. A preferred activation process involves contacting the thermally decomposed carbon with one or more of oxygen, steam, CO, CO2, and KOH at a temperature in the range of 600°C to 1000°C.

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

[0064] The porous carbon skeleton is preferably at least 750m 2 / g, or at least 1000m 2 / g, or at least 1250m 2 / g, or at least 1500m 2 It has a BET surface area of ​​4000 m² / g. As used herein, the term "BET surface area" is interpreted to mean the surface area per unit mass calculated from measurements of physicoadsorption of gas molecules onto a solid surface using the Brunauer-Emmett-Teller theory in accordance with ISO 9277. Preferably, the BET surface area of ​​the conductive porous particle framework is 4000 m² / g. 2 / g or less, or 3500m 2 / g or less, or 3250m 2 / g or less, or 3000m 2 It is less than / g.

[0065] As described above, the inventors have found that because the carbon skeleton contains micropores and / or mesopores, the desired properties are retained in the product even after grinding. Therefore, the present invention can target the desired properties of composite particle products by controlling the pore structure of the porous carbon skeleton. Certain classes of porous carbon skeletons are described below, and the present invention applies to them. By utilizing this, it is possible to provide a specific class of composite particle products. It will be understood that the characteristics of the porous carbon skeleton of the class described below should be considered in combination with the characteristics of the porous carbon skeleton described above, such as particle size.

[0066] Porous carbon skeleton 1 Porous carbon skeleton 1 has a P1 value of at least 0.5 and a PD of 5 nm or less. 50 It is characterized by its pore size.

[0067] The value of P1 is preferably at least 0.75, or at least 0.8, or at least 0.85, or at least 0.9, or at least 0.95, or at least 1, for example, at least 1.05, or at least 1.1, or at least 1.15, or at least 1.2.

[0068] The value of P1 can be up to 2.5. Preferably, the value of P1 can be 2.2 or less, or 2 or less, or 1.8 or less, or 1.6 or less, or 1.5 or less, or 1.4 or less, or 1.3 or less, or 1.2 or less, or 1.1 or less, or 1.0 or less, or 0.9 or less. More preferably, the value of P1 is 1.2 or less, or 1.1 or less, or 1.0 or less, or 0.9 or less.

[0069] The value of P1 can preferably be in the range of 0.7 to 1.5, or 0.75 to 1.4, or 0.7 to 1.3, or 0.75 to 1.3, or 0.7 to 1.2, or 0.75 to 1.2, or 0.75 to 1.2, or 0.7 to 1, or 0.75 to 1, or 0.7 to 0.9, or 0.75 to 0.9.

[0070] PD of porous carbon skeleton 1 50 The pore size is preferably 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less. PD of porous carbon skeleton 50The pore size is preferably at least 0.8 nm, or at least 1 nm, or at least 1.2 nm. Therefore, it is particularly preferable that 50% or more of the total micropore and mesopore volume is in the form of micropores.

[0071] More preferably, at least 80% of the total micropore and mesopore volume of the porous carbon skeleton 1 has a pore morphology with a diameter of 5 nm or less. Therefore, the PD of the porous carbon skeleton 1 80 The pore size is preferably 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less.

[0072] The volume of larger mesopores in the porous carbon skeleton 1 is preferably PD 90 The pore size is limited to 20 nm or less, or 15 nm or less, or 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less.

[0073] Preferably, PD 95 The pore size is 20 nm or less, or 15 nm or less, or 12 nm or less, or 10 nm or less.

[0074] Porous metallic skeleton 2 The porous carbon skeleton 2 has a P1 value of at least 0.6 and a micropore volume fraction φ in the range of 0.1 to 0.9. a It is characterized by:

[0075] The porous carbon skeleton 2 is also characterized by a pore volume that is substantially strained toward smaller pores, such that at least 75% of the total micropore and mesopore volume has a pore morphology with a diameter of 20 nm or less. The volume ratio of pores with a diameter of 20 nm or less (relative to the total pore volume) is indicated by the sign φ. 20 It is represented by the sign φ 10 The symbols φ5 and φ5 are used to define the volume fractions corresponding to pores with diameters of 10 nm or less and 5 nm or less, respectively.

[0076] The value of P1 is preferably at least 0.65, or at least 0.7, or at least 0.75, or at least 0.8, or at least 0.85, or at least 0.9, or at least 0.95, or at least 1. P1 can optionally be at least 1.05, or at least 1.1, or at least 1.15, or at least 1.2. The value of P1 can be at most 2.2. The value of P1 is more preferably 2.2 or less, or 1.8 or less, or 1.6 or less, or 1.5 or less, or 1.4 or less, or 1.3 or less, or 1.2 or less.

[0077] The value of P1 is preferably, for example, in the range of 0.6 to 1.4, or 0.65 to 1.4, or 0.7 to 1.4, or 0.75 to 1.4, or 0.6 to 1.3, or 0.65 to 1.3, or 0.7 to 1.3, or 0.75 to 1.3, or 0.6 to 1.2, or 0.65 to 1.2, or 0.7 to 1.2, or 0.75 to 1.2, or 0.6 to 1, or 0.65 to 1, or 0.7 to 1, or 0.75 to 1, or 0.6 to 0.9, or 0.65 to 0.9, or 0.7 to 0.9, or 0.75 to 0.9.

[0078] φ a The value of φ is preferably in the range of 0.15 to 0.85, more preferably in the range of 0.2 to 0.8. In some embodiments, in order to particularly utilize the high capacitance retention rate due to the very fine nanostructures of the electroactive material located within the micropores, φ a is preferably in the range of 0.45 to 0.85, or 0.5 to 0.8, or 0.6 to 0.8. In other cases, in order to particularly utilize the opportunity of a high filling amount of the electroactive material, φ a is preferably in the range of 0.2 to 0.5, or 0.3 to 0.5.

[0079] φ 20Preferably, it is at least 0.8, more preferably at least 0.85, and more preferably at least 0.9.

[0080] φ relative to the total volume of micropores and mesopores 10 Preferably, φ5 is at least 0.75, or at least 0.8, or at least 0.85. The φ5 relative to the total volume of micropores and mesopores is preferably at least 0.75, or at least 0.8, or at least 0.85. Thus, at least 75% of the total volume of micropores and mesopores in the porous carbon skeleton has a pore morphology with a diameter of preferably 10 nm or less, more preferably 5 nm or less.

[0081] Porous carbon skeleton 3 The porous carbon skeleton 3 has a P1 value of at least 0.6 and a PD of 2 nm or less. 50 It is characterized by its pore size.

[0082] The value of P1 is preferably at least 0.75, or at least 0.8, or at least 0.85. P1 can optionally be at least 0.9, or at least 0.95, or at least 1, or at least 1.05, or at least 1.1, or at least 1.15, or at least 1.2. The value of P1 can usually be 2.5 or less. The value of P1 is more preferably 2.4 or less, or 2.2 or less, or 2 or less, or 1.8 or less, or 1.6 or less, or 1.5 or less, or 1.4 or less, or 1.3 or less, or 1.2 or less, or 1.1 or less, or 1.0 or less, or 0.9 or less.

[0083] The value of P1 can preferably be in the range of 0.6 to 1.4, or 0.65 to 1.4, or 0.7 to 1.4, or 0.75 to 1.4, or 0.7 to 1.3, or 0.75 to 1.3, or 0.7 to 1.2, or 0.75 to 1.2, or 0.7 to 1, or 0.75 to 1, or 0.7 to 0.9, or 0.75 to 0.9.

[0084] PD of the porous carbon framework 3 50 The pore diameter is preferably 1.8 nm or less, or 1.6 nm or less, or 1.4 nm or less, or 1.2 nm or less, or 1 nm or less.

[0085] Preferably, at least 80% of the total micropore and mesopore volume of the porous carbon framework 3 has the form of pores with a diameter of 5 nm or less. Therefore, the PD of the porous carbon framework 3 80 The pore diameter is preferably 5 nm or less, or 4.5 nm or less, or 4 nm or less, or 3.5 nm or less, or 3 nm or less, or 2.5 nm or less, or 2.2 nm or less, or 2 nm or less, or 1.8 nm or less, or 1.6 nm or less.

[0086] PD 90 The pore diameter is preferably 10 nm or less, or 8 nm or less, or 6 nm or less, or 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less.

[0087] PD 95 The pore diameter is preferably 15 nm or less, or 12 nm or less, or 10 nm or less.

[0088] CVI / FBR For depositing an electroactive material into the micropores and / or mesopores of the framework by CVI by contacting the porous carbon framework with a gas mixture containing a gaseous precursor (e.g., silane) of the electroactive material, a laboratory-scale FBR can be used. As the inert fluidizing gas, nitrogen gas can be used, but other inert gases such as argon, hydrogen, or helium can also be used. It will be understood that in the method of the present invention, the porous carbon framework is fluidized in the FBR.

[0089] In the method of the present invention, CVI of a gaseous precursor of an electroactive material into the pore structure of the porous carbon framework is used. The gaseous precursor is preferably a silicon-containing gas.

[0090] Suitable silicon-containing precursors include silane (SiH4), disilane (Si2H6), trisilane (Si3H8), and tetrasilane (Si4H 10 Examples include chlorosilanes such as ) or trichlorosilane (HSiCl3), or methylchlorosilanes such as methyltrichlorosilane (CH3SiCl3) or dimethyldichlorosilane ((CH3)2SiCl2). The silicon-containing precursor is preferably a silane.

[0091] In the CVI process, doped electroactive materials can also be deposited in the micropores and / or mesopores of a porous carbon skeleton using gaseous precursors of the dopant material. When the dopant is boron, suitable precursors include borane (BH3), triisopropyl borate ([(CH3)2CHO]3B), triphenylborane ((C6H5)3B), and tris(pentafluorophenyl)borane ((C6F5)3B), with borane being preferred. When the dopant is phosphorus, a suitable precursor is phosphine (PH3).

[0092] The precursor can be used either in its pure form or, more commonly, as a diluted mixture with an inert carrier gas such as nitrogen or argon. For example, the precursor may be used in an amount of 0.5% to 20% by volume, or 1% by volume, relative to the total volume of the precursor and the inert carrier gas. It can be used in quantities ranging from 10% to 10% by volume, or from 1% to 5% by volume. The CVI process is preferably carried out with the total pressure below atmospheric pressure (101.3 kPa) (for example, in the range of 50 kPa to 101.3 kPa) to lower the partial pressure of the gaseous precursor, and the remaining partial pressure is controlled by an inert padding gas such as hydrogen, nitrogen, or argon to create an atmosphere. It becomes pressure.

[0093] The temperature of the CVI process is selected so that the precursor is thermally decomposed into an electroactive material. The CVI process is preferably carried out at temperatures in the range of 200°C to 1250°C, or 400°C to 700°C, or 400°C to 600°C, or 400°C to 550°C, or 450°C to 550°C, or 450°C to 500°C. The CVI process is preferably carried out at temperatures in the range of 400°C to 500°C, preferably 400°C to 450°C or 450°C to 500°C. The CVI process is preferably carried out at or above the minimum fluidization rate (Umf) of the particulate material. The empty velocity is preferably greater than the minimum fluidization rate (Umf) of the particulate material. The minimum fluidization rate (Umf) is typically a measured quantity whose value varies with particle size, particle density, and gas viscosity. The minimum fluidization rate (Umf) specifies the flow rate of gas to be supplied to the reactor vessel to achieve the rate at which the particles are swept up into a "fluid-like" state. The flow rate in the CVI process is preferably selected to provide good solid-solid and solid-gas mixing and minimize particle carryover from the reactor. The CVI process is preferably carried out in the range of 1 to 20 times the minimum fluidization rate (Umf).

[0094] While we do not wish to be bound by theory, controlling the particle size of the porous carbon skeleton in the manner described above is thought to kinetically control the penetration of electroactive materials. Kinetic control of penetration is thought to result in composite particles in which the electroactive material is uniformly distributed throughout. This could potentially cause pore blockage throughout the entire volume of the skeleton after a certain amount of electroactive material has been deposited. Controlling the particle size of the porous carbon skeleton has the advantage of enabling high penetration efficiency in the temperature and concentration range used in the CVI process, and also makes the skeleton suitable for fluidization in the classical sense (Geldert's Group A, etc.).

[0095] Crushing The method of the present invention includes the step of grinding intermediate particles to obtain the composite particles. The grinding step is carried out such that the particle size of the composite particles is smaller than the particle size of the particulate porous carbon skeleton. The advantage of the present invention is that the grinding step provides a final product with a small particle size suitable for use in metal-ion batteries, while enabling the use of CVI in FBRs, which is a process suitable for large-scale commercial use.

[0096] During the CVI process in FBRs, some aggregation of the porous carbon framework is possible. Therefore, the particle size of the intermediate particles may be larger than the particle size of the porous carbon framework.

[0097] Grinding can be carried out using various types of grinding equipment, such as wet mills, ball mills, jet mills, high-shear agitators, and ultrasonic devices. Considering the reactivity of intermediate particles immediately after infiltration is complete, grinding is preferably carried out with a dry mill, as electroactive materials deposited in the CVI process may become reactive. For example, silicon deposited from silane contains a considerable amount of Si-H bonds. These bonds are reactive with organic molecules and water. Therefore, the presence of oxygen or organic solvents can trigger exothermic reactions, potentially leading to partial destruction of the Si / C composite material and / or degradation to a quality lower than that required for commercially available metal-ion battery materials.

[0098] Among dry mills, jet mills are preferred because they have the ability to grind materials to even smaller sizes. Jet mills use a high-speed jet of compressed air or inert gas to grind particles. The materials are made to collide with each other. Jet mills can be used with starting materials up to approximately 1 mm in size, and are known to easily achieve a size of about 1 μm with relatively low energy input.

[0099] There are various types of jet mills, such as rotary (rotational motion) and flow-opposed jet mills. In rotary mills, the tangential force of gas from a wall is used to accelerate particles. In flow-opposed jet mills, multiple jets separated at equal angles to each other work together to collide particles on opposing collision trajectories. Flow-opposed jet mills are more suitable when higher capacity is desired. In both types of mills, the grinding action is achieved by collisions between particles rather than with hard objects. This particular mode of action results in a pulverized material with a narrow particle size distribution, which is beneficial when incorporated into electrodes for metal-ion batteries. Furthermore, using an inert grinding gas with a controlled composition (limited oxygen and moisture content) results in higher purity of the pulverized material.

[0100] Whether designed as a rotary jet mill (e.g., a spiral jet mill) or a flow-opposed jet mill, it can be used with a diameter ranging from 0.04 m to several meters, a grinding gas pressure of 50 kPa to 1000 kPa, and a maximum starting particle size of 1 mm. The grinding gas is either an inert gas such as nitrogen or argon, or a mixture of these with low partial pressure air, water, or oxygen.

[0101] The crushed particles can optionally be classified by size, for example, by centrifugation or sieving.

[0102] Before the grinding process, intermediate particles can be passivated. That is, the particle surface is treated to reduce its chemical reactivity, preferably minimizing or preventing further oxidation of the particle surface in subsequent process steps or handling. For example, intermediate particles can be passivated in a low-oxygen environment, such as with an oxygen concentration of less than 10% by volume. Intermediate particles can be passivated using an inert gas such as nitrogen. A low-oxygen gas mixture can also be used. Passivation of intermediate particles has the advantage of suppressing undesirable further reactions of the intermediate particles. For example, passivation of intermediate particles can remove reactive Si-H bonds. This helps maintain the structure of electroactive material deposited in the pores of the porous carbon skeleton resulting from the CVI process. This is beneficial when composite particles are used in metal-ion batteries. The grinding process can also be carried out in a low-oxygen environment, such as with an inert gas or a low-oxygen gas mixture. For convenience, the grinding process can be carried out in the same atmosphere as any passivation process.

[0103] Before the grinding process, the intermediate particles can optionally be cooled in combination with a passivation process. Cooling can be performed to temperatures below 100°C, below 50°C, or down to ambient temperature. Cooling the intermediate particles has the advantage of making it easier to transfer them to the grinding apparatus.

[0104] The method of the present invention may be a continuous method or a batch method. In the continuous method, the passivation step and the cooling step must be carried out in a container separate from the FBR. The container separate from the FBR can be a grinding device.

[0105] Composite particle products An advantage of the present invention is that the properties of the composite particle product can be controlled by selecting the properties of the porous carbon skeleton starting material. This is because the inventors have found that since the functional units of the composite particles are on a nanometer length scale, while the fracture is on a micrometer length scale, pulverization can occur without causing significant damage. This is thus achieved. In other words, the grinding process provides the desired particle size to the composite particle product while maintaining the desired nanostructure obtained from depositing electroactive material in a porous carbon framework containing micropores and / or mesopores using CVI. For example, both intermediate particles and composite particles may contain multiple nanoscale domains of the elemental form of electroactive material located within the micropores and / or mesopores of the porous carbon framework. As used herein, the term “nanoscale domain” refers to a nanoscale body of electroactive material located within the pores of the porous carbon framework. The maximum dimension of a nanoscale silicon domain is defined by the pore diameter of the pore in which the silicon is located.

[0106] Composite particles are generally particulate materials in which nanoscale domains of an electroactive material occupy the pore volume of a porous carbon skeleton having pore volumes including micropores and / or mesopores. This particle structure has been shown to provide an electroactive material with very high gravimetric and volumetric capacities when lithium-ionized, and with a high reversible capacity retention rate over multiple charge-discharge cycles.

[0107] While not bound by theory, it is believed that the location of nanoscale electroactive domains within micropores and / or mesopores provides, firstly, a fine electroactive structure that can be lithitated and delithiated without excessive structural stress. These extremely fine electroactive domains are thought to have lower resistance to elastic deformation and higher fracture resistance than larger electroactive structures. By ensuring that a relatively high proportion of the pore volume is occupied by the electroactive material, the composite particles can have high capacity. Furthermore, the location of nanoscale electroactive domains within micropores and / or mesopores limits the formation of SEIs because only a small area of ​​the electroactive surface can access the electrolyte.

[0108] In some cases, the composite particles produced by the present invention may include pores in which the completely enclosed voids are covered with an electroactive material such that electrolytes cannot access these voids.

[0109] The particle size of the composite particles can be controlled by controlling the grinding process and, optionally, the process of classifying the particles by size, thereby providing a desirable particle size distribution for the end application.

[0110] As a result of grinding the intermediate particles in process (c), the D of the composite particles 50 Particle size is D of the porous carbon skeleton 50 The particle size becomes smaller than the particle diameter. Therefore, the composite particles obtained in step (c) are D of the porous carbon skeleton. 50 As long as the particle size is even larger, for example, up to 50 μm D 50 The particle size may be 40 μm or less, or 30 μm or less, or 25 μm or less. 50 It can have a particle size.

[0111] The composite particles are D, which is less than 20 μm in size. 50 It is preferable that the particle size be 15 μm or less, or 12 μm or less, or 10 μm or less, or 9 μm or less, or 8 μm or less, or 7 μm or less, or 6.5 μm or less, or 6 μm or less, or 5.5 μm or less, or 5 μm or less, or 4.5 μm or less, or 4 μm or less, or 3.5 μm or less. 50 It can have a particle size.

[0112] The composite particles are D, which is at least 1 μm, or at least 2 μm, or at least 3 μm, or at least 4 μm, or at least 5 μm. 50 It can have a particle size.

[0113] The composite particles are preferably in the range of 0.5 μm to 20 μm, or 0.5 μm to 15 μm, or 0.5 μm to 12 μm, or 0.5 μm to 10 μm, or 0.5 D in the range of μm to 8 μm, or in the range of 0.5 μm to 9 μm, or in the range of 0.5 μm to 7 μm 50The particles have a particle size. Composite particles within these size ranges and having the porosity and pore size distribution described herein are dispersible in slurries, structurally robust, maintain capacity over repeated charge-discharge cycles, and are suitable for forming dense electrode layers with a uniform thickness in the conventional range of 20 μm to 50 μm, making them ideally suited for use in anodes for metal-ion batteries.

[0114] The composite particles have a diameter of at least 0.2 μm, or at least 0.5 μm, or at least 0.8 μm, or at least 1 μm, or at least 1.5 μm, or at least 2 μm. 10 It can have a particle size.

[0115] The composite particles are 40 μm or less, or 30 μm or less, or 20 μm or less, or 15 μm or less, or 10 μm or less, or 8 μm or less, or 6 μm or less. 90 It can have a particle size.

[0116] In step (a), the porous carbon skeleton is at least 30 μm thick. 50 D has a particle size and the composite particles obtained in step (c) are 20 μm or less. 50 It is preferable that the particle size is at least 40 μm. 50 D has a particle size and the composite particles obtained in step (c) are 20 μm or less. 50 It is more preferable that the particle size is at least 50 μm. 50 D has a particle size and the composite particles obtained in step (c) are 20 μm or less. 50 It is more preferable that the particles have a certain size.

[0117] The composite material of the present invention is preferably 300m 2 / g or less, or 250m 2 / g or less, or 200m 2 / g or less, or 150m 2 / g or less, or 100m 2 / g or less, or 80m 2 / g or less, or 60m 2 / g or less, or 40m 2 / g or less, or 30m 2 / g or less, or 25m 2 / g or less, or 20m 2 / g or less, or 15m 2 / g or less, or 10m 2 The BET surface area is less than or equal to / g. Generally, a small BET surface area is preferred to minimize the formation of a solid electrolyte interface (SEI) layer on the surface of the composite particles during the first charge-discharge cycle of an anode containing the particulate material of the present invention. However, an excessively small BET surface area leads to unacceptably low charge rates and capacities because metal ions in the surrounding electrolyte cannot access most of the electroactive material. For example, the BET surface area is preferably at least 0.1 m². 2 / g, or at least 1m 2 / g, or at least 2m 2 / g, or at least 5m 2 It is / g. For example, the surface area of ​​BET is 1m 2 / g~25m 2 Range of / g, more preferably 2m 2 / g~15m 2 It can be in the range of / g.

[0118] Preferably at least 90% by weight, more preferably at least 95% by weight, more preferably at least 98% by weight, and more preferably at least 99% by weight of the electroactive mass in the composite particles is located within the internal pore volume of the porous carbon skeleton, such that there is little to no electroactive material located on the outer surface of the composite particles.

[0119] The volumes of micropores and mesopores in the composite particles (i.e., in the presence of electroactive material), as measured by nitrogen gas adsorption, are preferably 0.15 × P1 or less, or 0.10 × P1 or less, or 0.05 × P1 or less, or 0.02 × P1 or less.

[0120] The weight ratio of electroactive material such as silicon to the porous carbon skeleton in composite particles can be determined by elemental analysis. Elemental analysis is used to determine the weight ratio of both electroactive material and carbon in the composite particles. Optionally, the amounts of hydrogen, nitrogen, and oxygen can also be determined by elemental analysis. Elemental analysis can be used to determine the carbon in the porous carbon skeleton only. It is also preferable to optionally use this to determine the weight percentages of hydrogen, nitrogen, and oxygen. By determining the weight percentage of carbon in the porous carbon skeleton alone, the possibility that this porous carbon skeleton contains small amounts of heteroatoms within its molecular framework can be taken into account. By performing both measurements together, the weight percentage of silicon to the entire porous carbon skeleton can be reliably determined.

[0121] The content of electroactive material (e.g., silicon) is preferably determined by ICP-OES (inductively coupled plasma emission spectroscopy). Available from ThermoFisher Scientific. Many ICP-OES analyzers are commercially available, such as the iCAP® 7000 series. The carbon content (and, if necessary, the hydrogen, nitrogen, and oxygen content) in composite particles and porous carbon skeletons is preferably determined by IR absorption. A suitable instrument for determining the carbon, hydrogen, nitrogen, and oxygen content is the TruSpec® Micro elemental analyzer, available from Leco Corporation.

[0122] Preferably, when the electroactive material is silicon, the composite particles contain 30% to 80% by weight of silicon, more preferably 45% to 65% by weight of silicon.

[0123] The composite particles preferably have a low total oxygen content. 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. The total oxygen content of the composite particles is preferably less than 15% by weight, more preferably less than 10% by weight, more preferably less than 5% by weight, for example less than 2% by weight, or less than 1% by weight, or less than 0.5% by weight.

[0124] When the electroactive material is silicon, the weight ratio of silicon to the porous carbon skeleton in the composite particles is preferably in the range of [0.5×P1 to 2.2×P1]:1. This relationship defines a silicon weight ratio in which approximately 20% to 95% of the pore volume is occupied by silicon, taking into account the silicon density and the pore volume of the porous carbon skeleton.

[0125] The composite particles typically have a specific charge capacity of 1200 mAh / g to 2340 mAh / g upon initial lithiumization. Preferably, the composite particles have a specific charge capacity of at least 1400 mAh / g upon initial lithiumization.

[0126] As described above, by using a specific class of porous carbon skeleton, a specific class of composite particle products can be targeted. It will be understood that the pore structure of the porous carbon skeleton, such as micropores and / or mesopores, is maintained in the composite particle product. A specific class of composite particle products will be described below. It will be understood that the characteristics of the composite particles of the class described below should be considered in combination with the characteristics of the composite particles described above, such as particle size.

[0127] Composite particle 1 The composite particle 1 produced by the method of the present invention is (a) A porous carbon skeleton containing micropores and / or mesopores, Micropores and / or mesopores have a total pore volume of P1cm² measured by gas adsorption. 3 / g, where P1 represents a natural number having a value of at least 0.7, and PD measured by gas adsorption 50 A porous carbon skeleton with a pore size of 5 nm or less, (b) Multiple elemental nanoscale silicon domains located within the micropores and / or mesopores of the porous carbon skeleton, Includes, The weight ratio of silicon to porous carbon skeleton in the composite particles is in the range of [0.5×P1~1.3×P1]:1. This is because the volume of silicon (in an uncharged state) is within the total micrometers. This corresponds to approximately 20% to 55% of the pore / mesopore volume.

[0128] The composite particle 1 can be manufactured using the porous carbon skeleton 1 as the starting material. Therefore, the pore structure of the porous carbon skeleton 1 may be present in the composite particle 1.

[0129] The weight ratio of silicon to carbon is preferably in the range of [0.55×P1~1.1×P1]:1, or [0.6×P1~1.1×P1]:1, or [0.6×P1~1×P1]:1, or [0.6×P1~0.95×P1]:1, or [0.6×P1~0.9×P1]:1, or [0.65×P1~0.9×P1]:1, or [0.65×P1~0.85×P1]:1, or [0.65×P1~0.8×P1]:1, or [0.7×P1~0.8×P1]:1.

[0130] Silicon preferably accounts for about 25% to about 45%, more preferably about 25% to about 40%, of the internal pore volume of the porous carbon framework. Within these preferred ranges, the pore volume of the porous carbon framework is effective in accommodating the expansion of silicon during charging and discharging, and excess pore volume that does not contribute to the volumetric capacity of the particulate material is avoided. However, the amount of silicon is also not so large that it hinders effective lithiation due to insufficient metal ion diffusion rate or insufficient expansion volume, resulting in mechanical resistance to lithiation.

[0131] Composite particle 1 is D in the range of 0.5 μm to 50 μm. 50It can have a particle size. D 50 The particle size can be any size, and can be 20 μm or less.

[0132] Composite particle 1 is, for example, D in the range of 1 μm to 25 μm, or 1 μm to 20 μm, or 2 μm to 20 μm, or 2 μm to 15 μm, or 3 μm to 15 μm. 50 It can have a particle size.

[0133] Composite particles 2 The composite particle 2 produced by the method of the present invention is (a) A porous carbon skeleton including micropores and mesopores, (i) Micropores and mesopores have a total pore volume of P1cm² measured by gas adsorption. 3 / g, where P1 has a value of at least 0.6, (ii) Volume ratio of micropores to the total volume of micropores and mesopores (φ a ) is in the range of 0.1 to 0.9, (iii) Volume ratio of pores with a diameter of 20 nm or less relative to the total volume of micropores and mesopores (φ 20 ) is at least 0.75, and, (iv) The porous carbon skeleton is less than 20 μm 50 A porous carbon skeleton having particle size, (b) Multiple nanoscale elemental silicon domains located within the micropores and / or mesopores of the porous carbon skeleton, Includes, The weight ratio of silicon to porous carbon skeleton in the composite particles is in the range of [1×P1~2.2×P1]:1.

[0134] The composite particle 2 can be manufactured using the porous carbon skeleton 2 as the starting material. Therefore, the pore structure of the porous carbon skeleton 2 may be present in the composite particle 2.

[0135] Composite particle 2 is particularly suitable for use in "hybrid" electrodes that include a combination of graphite and composite particles.

[0136] The weight ratio of silicon to porous carbon skeleton in composite particles is [1 × P1 ~ 2.2 × The range is P1:1. The weight ratio of [1×P1]:1 is such that the density of silicon is approximately 2.3 g / cm³. 3 This corresponds to a pore occupancy rate of approximately 43 v / v% in the porous carbon skeleton made of silicon. The upper limit of the above weight ratio [2.2 × P1]:1 corresponds to a pore occupancy rate of approximately 95 v / v% in the porous carbon skeleton made of silicon.

[0137] The weight ratio of silicon to porous carbon skeleton is preferably at least 1.1 × P1, more preferably at least 1.15 × P1, more preferably at least 1.2 × P1, more preferably at least 1.25 × P1, more preferably at least 1.3 × P1, more preferably at least 1.35 × P1, and more preferably at least 1.4 × P1.

[0138] When the porous carbon skeleton has a relatively high ratio of mesopores to micropores (for example, φ a If the ratio is in the range of 0.2 to 0.5 or 0.3 to 0.5, the weight ratio of silicon to carbon can be further increased, for example, to at least 1.45 × P1, more preferably at least 1.5 × P1, more preferably at least 1.55 × P1, more preferably at least 1.6 × P1, more preferably at least 1.65 × P1, and more preferably at least 1.5 × P1.

[0139] In a more preferred embodiment, the minimum weight ratio of silicon to porous carbon skeleton is at least [φ b The value given by +0.75] × P1, or at least [φ b The value given by +0.8] × P1, or at least [φ b The value given by +0.9] × P1, or at least [φ b The value given by [φ +1] × P1, or at least [φ b This is the value given by +1.1 × P1. Therefore, the mesoporosity (φb When the value of ) is higher, the amount of silicon in composite particle 2 also increases. The correlation between this mesoporosity and the minimum weight ratio of silicon to the porous carbon skeleton means that porous carbon skeletons with higher mesoporosity are occupied to a greater extent by silicon, thereby optimizing the volumetric capacity of composite particle 2. In porous carbon skeletons with higher mesoporosity, the larger minimum amount of silicon reduces the possibility of larger micropores being partially occupied by silicon, thereby reducing the silicon surface area exposed to the electrolyte and limiting the formation of undesirable SEIs.

[0140] In further embodiments, the maximum weight ratio of silicon to porous carbon skeleton is [φ b [φ] is less than or equal to the value given by +1.6 × P1, more preferably less than or equal to [φ b It is less than or equal to the value given by [+1.5] × P1. Due to the correlation between this mesoporosity and the maximum weight ratio of the porous carbon skeleton, porous carbon skeletons with higher microporosity are not overfilled with silicon.

[0141] Composite particle 2 is D in the range of 0.5 μm to 20 μm. 50 It can have a particle size. Composite particle 2 D 50 The particle size is preferably 12 μm or less, or 10 μm or less, or 8 μm or less.

[0142] Composite particle 2 is, for example, D in the range of 1 μm to 12 μm, or 1 μm to 10 μm, or 2 μm to 10 μm, or 3 μm to 8 μm. 50 It can have a particle size.

[0143] Composite particle 2's D 10 The particle size is preferably at least 0.5 μm.

[0144] Composite particle 2's D 90 The particle size is preferably 12 μm or less, or 10 μm or less.

[0145] Composite particles 3 The composite particles 3 produced by the method of the present invention are (a) A porous carbon skeleton containing micropores and / or mesopores, Micropores and mesopores have a total pore volume of at least 0.7 cm³ as measured by gas adsorption. 3 / g PD measured by gas adsorption 50 A porous carbon skeleton with a pore size of 2 nm or less, (b) comprising an electroactive material located within the micropores and / or mesopores of a porous carbon skeleton, The composite particles are D 10 μm or smaller. 90 It has a particle size.

[0146] The composite particle 3 can be manufactured using the porous carbon skeleton 3 as the starting material. Therefore, the pore structure of the porous carbon skeleton 3 may be present in the composite particle 3.

[0147] The composite particle 3 relates to a particulate material in which the porous carbon skeleton has a relatively high total volume of micropores and mesopores, and pores with a diameter of 2 nm or less constitute at least 50% of the total pore volume. This pore structure may originate from the porous carbon skeleton 3. The composite particle 3 has a particle size distribution that is heavily biased toward particles with a diameter of 10 μm or less. It has been found that the combination of small particle size and highly divided pore volume provides an electroactive material with high resistance to mechanical degradation during electrode manufacturing.

[0148] Composite particle 3 D 90 The particle size is preferably 9.5 μm or less, or 9 μm or less, or 8.5 μm or less, or 8 μm or less, or 7.5 μm or less, or 7 μm or less, or 6.5 μm or less, or 6 μm or less, or 5.5 μm or less, or 5 μm or less, or 4.5 μm or less, or 4 μm or less.

[0149] The composite particles 3 are preferably D in the range of 0.5 μm to 7 μm. 50 It has a particle size. D 50The particle size can be any size, at least 1 μm, at least 1.5 μm, at least 2 μm, at least 2.5 μm, or at least 3 μm.

[0150] D 50 The particle size can be any of the following: 6.5 μm or less, 6 μm or less, 5.5 μm or less, 5 μm or less, 4.5 μm or less, 4 μm or less, or 3.5 μm or less.

[0151] The composite particle 3 is, for example, in the range of 1 μm to 6.5 μm, or 1.5 μm to 6 μm, or 2 μm to 5.5 μm, or 2.5 μm to 5 μm, or 3 μm to 4.5 μm. 50 It can have a particle size.

[0152] Composite particle 3 D 10 The particle size is preferably at least 0.5 μm.

[0153] Composite particle 3 D 99 The particle size is preferably 25 μm or less.

[0154] The amount of electroactive material in the composite particle 3 is preferably selected such that the electroactive material occupies about 55% or less of the internal pore volume of the porous carbon skeleton (in an uncharged state). Preferably, the electroactive material occupies about 25% to about 45% of the internal pore volume of the porous carbon skeleton, more preferably about 25% to 40%.

[0155] When the electroactive material is silicon, the weight ratio of silicon to porous carbon skeleton is preferably [0.5×P1~1.3×P1]:1. The weight ratio of silicon to carbon is more preferably in the range of [0.55×P1~1.1×P1]:1, or in the range of [0.6×P1~1.1×P1]:1, or in the range of [0.6×P1~1×P1]:1, or in the range of [0.6×P1~0.95×P1]:1, or in the range of [0.6×P1~0.9×P1]:1, or in the range of [0.65×P1~0.9×P1]:1, or in the range of [0.65×P1~0.85×P1]:1, or in the range of [0.65×P1~0.8×P1]:1, or in the range of [0. The range is 7×P1 to 0.8×P1:1.

[0156] Carbon coating The method of the present invention may optionally include a further step of depositing a conductive film, preferably a carbon-based film, onto the composite particles. Preferably, the conductive carbon-based film can be obtained by chemical vapor deposition (CVD). CVD is a methodology known in the art and involves the thermal decomposition of a volatile carbon-containing gas (e.g., ethylene) on the surface of a particulate material. Alternatively, the carbon-based film can be formed by depositing a solution of a carbon-containing compound onto the surface of a particulate material, followed by thermal decomposition. The conductive film (carbon-based film, etc.) has sufficient permeability to allow lithium to access the interior of the composite particles without excessive resistance, so as not to degrade the rate performance of the composite particles. For example, the thickness of the conductive film can preferably be in the range of 2 nm to 30 nm. The conductive film may optionally be porous and / or only partially cover the surface of the composite particles.

[0157] The conductive coating smooths out any surface defects and the remaining microstructure (microporosity) of the surface. By filling the gaps, the BET surface area of ​​the composite particles is further reduced, which has the advantage of further reducing the initial cycle loss. In addition, the conductive coating improves the conductivity of the composite particle surface, reducing the need for conductive additives in the electrode composition, and also forms an optimal surface for the formation of a stable SEI layer, improving the capacity retention rate during cycling.

[0158] The BET surface area of ​​the composite particles after the conductive coating has been deposited is preferably 50 m². 2 Less than / g, 30m 2 Less than / g, 20m 2 Less than / g, more comfortably, 10m 2 Less than / g, or 5m 2 It is less than / g.

[0159] End use of the product The method of the present invention may optionally include a further step of forming an electrode composition comprising composite particles (wherein the composite particles are optionally coated with a conductive carbon film). The electrode composition may include at least one other component selected from (i) a binder, (ii) a conductive additive, and (iii) additional particulate electroactive material.

[0160] The method of the present invention may optionally include a further step of forming a slurry comprising composite particles (wherein the composite particles are optionally coated with a conductive carbon film) and a solvent.

[0161] Product-by-process The present invention also provides particulate materials containing composite particles that can be obtained by the method of the present invention. The nanostructure of electroactive materials deposited by the CVI process of the present invention is different from the nanostructure of electroactive materials deposited by other means. Furthermore, since the composite particles are produced from the CVI process and a subsequent grinding process, they can be distinguished from particles of similar size produced without the subsequent grinding step. For example, the grinding step produces fracture surfaces that can be observed under a microscope. Therefore, the composite particles that can be obtained by the method of the present invention can be distinguished from composite particles obtained by other means. [Modes for carrying out the invention] [Examples]

[0162] Silicon-carbon composite particles were synthesized in a vertical fluidized bed reactor equipped with a stainless steel cylindrical container with an inner diameter of 83 mm. The BET surface area was 1777 m². 2 / g, total pore volume of 0.78 cm³ 3 / g, PD 10 0.97nm, PD 50 1.15nm, PD 90 is 2.23nm, and φ a 126g of a premixture of porous carbon particles (61%) is placed in the reactor. Inert gas (nitrogen) is injected into the reactor at a low flow rate to remove oxygen. Then the reactor is heated to 420°C~4 The reactor was heated to a reaction temperature of 40°C, and 1.25 v / v% monosilane gas, diluted with nitrogen, was supplied to the bottom of the reactor at a flow rate sufficient to fluidize the carbon skeleton particles for 32.3 hours (Sample 1) or 37 hours (Sample 2). As soon as the reaction time was complete, the atmosphere of the reactor was switched to pure nitrogen while maintaining fluidity, and this purge was continued for 30 minutes. The reactor was then heated to ambient temperature over several hours. After reaching ambient temperature, the atmosphere of the reactor was gradually switched to air over several hours.

[0163] The product was added to an MC DecJet® 30 mil feed tray and ground in an inert atmosphere. The ring pressure was set to 650 kPa and the venturi pressure to 700 kPa. The product was pulverized and then collected in a suitable container. The material properties of the two composite materials are shown in Table 1.

[0164] [Table 1]

[0165] Fabrication of the negative electrode Negative electrode coatings (anodes) were prepared from the materials of Sample 1 and Sample 2. A CMC binder dispersion of carbon black Super P (trademark) (conductive carbon) was mixed in a Thinky (trademark) mixer. A Si-C composite material was added to this mixture and mixed in a Thinky (trademark) mixer for 30 minutes. Next, an SBR binder was added to make the CMC:SBR ratio 1:1, and a slurry was obtained in which the weight ratio of Si-C composite material:CMC / SBR:carbon black was 70%:16%:14%. The slurry was mixed in a Thinky (trademark) mixer for another 30 minutes, and then coated onto a 10 μm thick copper substrate (current collector). After drying at 50°C for 10 minutes, the negative electrode was formed by further drying at 110°C for 12 hours.

[0166] Cell manufacturing and cycle Manufacturing of full cells A full coin cell was fabricated using a circular negative electrode with a radius of 0.8 cm, cut from a coating formed from samples 1 and 2 (as described above), a porous polyethylene separator, and a nickel-manganese-cobalt (NMC532) positive electrode. The positive and negative electrodes were designed to form a well-balanced pair such that the capacity ratio of the positive electrode to the negative electrode was 0.9. Then, an electrolyte containing 1 M LiPF6 was added to the cell in a 7:3 EMC / FEC (ethylene methyl carbonate / fluoroethylene carbonate) solution containing 3 wt% vinylene carbonate before sealing.

[0167] A full coin cell was cycled as follows: The anode was lithiumized by applying a constant current at a rate of C / 25 with a cutoff voltage of 4.3V. Once the cutoff voltage was reached, a constant voltage of 4.3V was applied until the cutoff current of C / 100 was reached. The cell was then left to rest for 10 minutes in the lithiumized state. Next, the anode was delithiated with a constant current of C / 25 at a cutoff voltage of 2.75V. The cell was then left to rest for 10 minutes. After this initial cycle, the anode was lithiumized by applying a constant current of C / 2 at a cutoff voltage of 4.3V, followed by applying a constant voltage of 4.3V with a cutoff current of C / 40, and a rest period of 5 minutes. Next, the anode was delithiated with a constant current of C / 2 at a cutoff voltage of 2.75V. It was then converted to thium. This process was then repeated for the desired number of cycles.

[0168] The charging (lithiumization) and discharging (delithiumization) capacities for each cycle are calculated per unit mass of the silicon-carbon composite material, and the capacity retention value is calculated for each discharge capacity as a percentage of the discharge capacity of the second cycle. The first cycle loss (FCL) is (1 - (initial delithiumization capacity / initial lithiumization capacity)) × 100%. The main values ​​averaged across three coin cells for each material are shown in Table 2.

[0169] [Table 2]

Claims

1. (a) containing micropores and / or mesopores, and having at least 20 μm of D ５０ To prepare a particulate porous carbon skeleton having a particle size, (b) In a fluidized bed reactor, an electroactive material selected from silicon, tin, aluminum, germanium, and their alloys is deposited in the micropores and / or mesopores of the porous carbon skeleton using a chemical vapor impregnation process to obtain intermediate particles. (c) Crushing the intermediate particles to obtain composite particles, A method for producing composite particles containing [a certain substance].

2. The method according to claim 1, further comprising transferring the intermediate particles to a grinding device before step (c).

3. The method according to claim 1 or 2, wherein the electroactive material is silicon.

4. The method according to any one of claims 1 to 3, wherein the intermediate particles and the composite particles include a plurality of nanoscale domains of the electroactive material in elemental form located within the micropores and / or mesopores of the porous carbon skeleton.

5. The method according to any one of claims 1 to 4, wherein the chemical vapor impregnation process is carried out at a temperature in the range of 200°C to 1250°C, or 400°C to 700°C, or 450°C to 550°C, or 450°C to 500°C.

6. The method according to any one of claims 1 to 5, further comprising the step of cooling the intermediate particles before grinding the intermediate particles, wherein the cooling is optionally performed to a temperature of less than 100°C, less than 50°C, or to ambient temperature.

7. The method according to any one of claims 1 to 6, further comprising a step of passivating the intermediate particles before grinding the intermediate particles, wherein the passivation is optionally carried out in an inert gas or in an environment with an oxygen concentration of less than 10% by volume.

8. The method according to any one of claims 1 to 7, wherein the grinding device is a jet mill.

9. The method according to any one of claims 1 to 8, wherein the step of grinding the intermediate particles is carried out in an inert gas or in an environment with an oxygen concentration of less than 10% by volume.

10. The method according to any one of claims 1 to 9, wherein it is a continuous method or a batch method.

11. The micropores and / or mesopores of the porous carbon skeleton have a total pore volume measured by gas adsorption of P １ cm ３ / g, where P １ The method according to any one of claims 1 to 10, wherein has a value of at least 0.4, or at least 0.5, or at least 0.6, or at least 0.7, or at least 0.75, or at least 0.8, or at least 0.85, or at least 0.9, or at least 0.95, or at least 1, or at least 1.05, or at least 1.1, or at least 1.

2.

12. The micropores and / or mesopores of the porous carbon skeleton have a total pore volume measured by gas adsorption of P １ cm ３ / g, where P １ The method according to any one of claims 1 to 11, wherein the value is 2.5 or less, or 2.2 or less, or 2 or less, or 1.8 or less, or 1.6 or less, or 1.5 or less, or 1.4 or less, or 1.3 or less.

13. The micropores and / or mesopores of the porous carbon skeleton have a total pore volume measured by gas adsorption of P １ cm ３ / g, where the value of P １ is in the range of 0.4 to 2.5, or 0.6 to 2.5, or 0.7 to 2, or 0.7 to 1.

2. The method according to claim 12

14. The porous carbon skeleton is in the range of 60 μm to 150 μm. ５０ The method according to any one of claims 1 to 13, having a particle size.

15. The porous carbon skeleton is made of D, which is at least 30 μm, or at least 40 μm, or at least 50 μm, or at least 60 μm, or at least 70 μm, or at least 80 μm. ５０ The method according to any one of claims 1 to 14, having a particle size.

16. The porous carbon skeleton has a diameter of 1000 μm or less, or 500 μm or less, or 250 μm or less, or 150 μm or less. ５０ The method according to any one of claims 1 to 15, having a particle size.

17. The porous carbon skeleton is made of D, which is at least 5 μm, or at least 15 μm, or at least 40 μm, or at least 50 μm, or at least 60 μm, or at least 70 μm. １０ The method according to any one of claims 1 to 16, having a particle size.

18. The porous carbon skeleton has a diameter of 1500 μm or less, or 1000 μm or less, or 750 μm or less, or 500 μm or less, or 200 μm or less. ９０ The method according to any one of claims 1 to 17, having a particle size.

19. The porous carbon skeleton has a diameter of 1550 μm or less, or 1050 μm or less, or 800 μm or less, or 550 μm or less, or 250 μm or less. ９８ The method according to any one of claims 1 to 18, having a particle size.

20. The porous carbon skeleton is at least 750 m ２ / g, or at least 1000m ２ / g, or at least 1250m ２ / g, or at least 1500m ２ The method according to any one of claims 1 to 19, having a BET surface area of ​​1 / g.

21. The porous carbon skeleton is 4000 m ２ / g or less, or 3500m ２ / g or less, or 3250m ２ / g or less, or 3000m ２ The method according to any one of claims 1 to 20, having a BET surface area of ​​less than or equal to / g.

22. The porous carbon skeleton is 1500 m ２ / g to 3000m ２ The method according to claim 21, having a BET surface area of ​​1 / g.

23. The porous carbon skeleton was measured by gas adsorption PD ５０ The method according to any one of claims 1 to 22, wherein the pore diameter is 5 nm or less, or 4 nm or less, or 3 nm or less, or 2.5 nm or less, or 2 nm or less, or 1.5 nm or less, or 1 nm or less.

24. The composite particles are in the range of 0.5 μm to 20 μm. ５０ The method according to any one of claims 1 to 23, having a particle size.

25. The composite particles are at least 1 μm, or at least 2 μm, or at least 3 μm, or at least 4 μm, or at least 5 μm of D ５０ The method according to claim 24, having a particle size.

26. The composite particles are 20 μm or less, or 15 μm or less, or 12 μm or less, or 10 μm or less, or 9 μm or less, or 8 μm or less, or 7 μm or less, or 6.5 μm or less, or 6 μm or less, or 5.5 μm or less, or 5 μm or less, or 4.5 μm or less, or 4 μm or less, or 3.5 μm or less. ５０ The method according to claim 24 or 25, having a particle size.

27. The composite particles are at least 0.2 μm, or at least 0.5 μm, or at least 0.8 μm, or at least 1 μm, or at least 1.5 μm, or at least 2 μm of D １０ The method according to any one of claims 1 to 26, having a particle size.

28. The composite particles are 80 μm or less, or 60 μm or less, or 40 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less, or 10 μm or less D ９０ The method according to any one of claims 1 to 27, having a particle size.

29. The method according to any one of claims 1 to 28, wherein the composite particles have a particle size distribution span of 5 or less, or 4 or less, or 3 or less, or 2 or less, or 1.5 or less.

30. The electroactive material is silicon, and the pore volume of the composite particles is P １ cm ３ Expressed in units of / g, and the weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.5 × P １ ~2.2 x P １ ]: Range of 1, or [1 × P １ ~2.2 x P １ ]: Range of 1, or [0.5 × P １ ~1.3 x P １ The method according to any one of claims 1 to 29, wherein the range is 1.

31. The method according to any one of claims 1 to 30, wherein the electroactive material is silicon, and the composite particles contain 30% to 80% by weight of silicon, or 45% to 65% by weight of silicon.

32. The method according to any one of claims 1 to 31, wherein the composite particles contain 15% by weight or less of oxygen, or 10% by weight or less of oxygen.

33. A particulate material comprising composite particles that can be obtained by the method described in any one of claims 1 to 32.

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