Silicon-carbon composite materials and methods

Abstract

The present invention provides a method for providing composite material particles having a carbon coating, and a core-shell particulate material obtained thereby. [Solution] The method comprises the step of heat-treating a plurality of precursor composite material particles by contacting them with a pyrolytic carbon precursor, wherein the outer shell of the pyrolytic conductive carbon material is formed on the precursor composite material particles, and the heat treatment is performed at a temperature of 700°C or lower.

Description

[Technical Field]

[0001] The present invention relates to a method for preparing core-shell composite particles containing electroactive materials such as carbon and silicon. The present invention also relates to particulate materials containing silicon and carbon and having a core-shell structure. [Background technology]

[0002] Rechargeable metal-ion batteries are widely used in portable electronic devices such as mobile phones and laptops. Furthermore, the rapid development of electric and hybrid vehicle technologies is creating a large new market for high-performance rechargeable batteries. Typically, the anode of a metal-ion battery has a metal current collector provided with a layer of electroactive material (defined here as a material capable of inserting and releasing metal ions during charging and discharging of the battery). When a metal-ion battery is charged, metal ions are transported from the metal-ion-containing cathode layer through the electrolyte and inserted into the anode material.

[0003] Conventional lithium-ion batteries use graphite as the electroactive material for the anode. When the graphite-containing anode is charged, lithium is intercalated between the graphite layers, and the empirical formula Li x A material having C6 (where x is greater than 0 and less than or equal to 1) is formed. This means that in lithium-ion batteries, graphite has a maximum theoretical capacity of 372 mAh / g, but the actual capacity is somewhat lower (approximately 340 to 360 mAh / g). The development of portable electronic devices and electric vehicles with high energy demands means there is a need for electroactive materials that offer improvements in the gravimetric and volumetric capacities of graphite.

[0004] Materials such as silicon, tin, and germanium have significantly higher intercalated lithium atom capacities compared to graphite. In particular, silicon has been recognized as a promising alternative to graphite for the manufacture of rechargeable metal-ion batteries with high gravimetric and volumetric capacities due to its extremely high lithium capacity (see, for example, Winter, M. et al., "Intercalated Electrode Materials for Rechargeable Lithium Batteries," Adv. Mater. 1998, 10, No. 10). In lithium-ion batteries, silicon has a theoretical maximum specific capacity of approximately 3,600 mAh / g at room temperature (Li 15 (Based on Si4)

[0005] The high specific capacity of silicon results in large volume changes during charging and discharging. Intercalation of lithium into bulk silicon increases the volume of the silicon material by up to 400% of its original volume. Consequently, repeated charge-discharge cycles generate significant mechanical stress on the silicon material, resulting in fracture and delamination of the silicon anode material, as well as deformation of other battery components. The shrinkage of silicon particles during delithiation can lead to loss of electrical contact between the anode material and the current collector. Another problem is that, as a result of electrolyte deposition, a solid electrolyte boundary (SEI) layer forms on the nascent silicon surface during the initial charge cycle. This SEI layer lacks sufficient mechanical durability to adapt to the expansion and contraction of silicon and delaminates from the silicon surface. Subsequently, the newly exposed silicon surface leads to further electrolyte decomposition, increasing the thickness of the SEI layer and resulting in irreversible lithium consumption. The combination of these failure mechanisms results in unacceptable losses of electrochemical capacity over continuous charge-discharge cycles.

[0006] Numerous approaches have been proposed to overcome the problems associated with volume changes observed when charging silicon-containing anodes. One approach involves using a form of microstructured silicon as the electroactive material. Microsilicon structures with a cross-section of less than approximately 150 nm, such as silicon films and silicon nanoparticles, are more resistant to volume changes during charging and discharging compared to silicon particles in the micron size range. However, in their unmodified forms, neither is particularly suitable for commercial-scale applications. Nanoscale particles are difficult to prepare and handle, and silicon films do not provide sufficient bulk capacity. Furthermore, the relatively high surface area of ​​microstructured silicon leads to unacceptable capacity loss due to excessive SEI formation during the first charging cycle.

[0007] To address the lack of available silicon-containing electroactive materials, the inventors have developed a type of composite material particle in which silicon is deposited within the pores of a porous conductive material (e.g., a carbon-containing porous material such as activated carbon material). The median value of the pore diameter is approximately 5 to 10 nm or less. By carefully controlling the total pore volume, the pore size distribution of the conductive material, and the weight ratio of silicon to the conductive material, it has been confirmed that it is possible to obtain materials with controlled expansion properties, limited SEI formation, and high reversible capacity retention. However, further improvements in the properties of these materials can be achieved by suppressing the surface area. Suppressing the surface area has several advantages, including further reduction of SEI formation and reduction of the amount of binder required to form the electrode active layer. Excess binder can contribute to a decrease in velocity properties. [Overview of the project] [Problems that the invention aims to solve]

[0008] Therefore, there is a need for electroactive materials that have the aforementioned types of composite material particles while also having a conductive carbon coating that helps reduce the surface area of ​​the particles, improve the kinetic properties of the composite material, and provide improved conductivity for the electrode active layer having core-shell particles. However, the aforementioned composite material particles are characterized by an extremely fine microstructure with fine silicon domains and fine pore walls. The fine microstructure of the composite material particles is crucial for their function as an electroactive material at the anode, but it is incompatible with conventional techniques for applying conductive carbon coatings. [Means for solving the problem]

[0009] In a first aspect of the present invention, a method for preparing core-shell composite material particles, (a) Below: (i) A porous carbon skeleton having micropores and / or mesopores, wherein the total pore volume of the micropores and mesopores, as measured by gas adsorption, is at least 0.4 cm³. 3 / g, and the PD of the porous carbon skeleton 50 Pore ​​diameter is 10 nm or less, porous carbon skeleton, and (ii) Multiple nanoscale electroactive material domains arranged together with the porous carbon skeleton, A step of providing multiple precursor composite material particles including, (b) A step of heat-treating the plurality of precursor composite material particles by contacting them with a pyrolytic carbon precursor, wherein the outer shell of the pyrolytic conductive carbon material is formed on the precursor composite material particles, and the heat treatment is performed at a temperature of 700°C or lower. A method is provided that has the following characteristics.

[0010] A key aspect of the present invention is that the thermal decomposition of the pyrolytic carbon precursor is carried out at a temperature of 700°C or lower. Generally, conventional processes for forming pyrolytic carbon coatings require temperatures above 700°C, for example, in the range of 800°C to 1200°C. However, it has been found that the fine microstructure of the aforementioned precursor composite material particles is not suitable for such high temperatures and is subject to various thermally induced changes, including heat treatment and crystallization processes. Heat treatment of the particle microstructure can lead to the removal of void spaces that accommodate the expansion of electroactive materials, such as silicon. Furthermore, since amorphous silicon exhibits good properties as an electroactive material, the crystallization of silicon is problematic. Additionally, excessive temperatures during the formation of the pyrolytic carbon coating can lead to the formation of undesirable compounds with little or no electrochemical activity, such as silicon carbide and silicon nitride. Combined, these processes impair the properties of the carbon coating particles as an electroactive material in the anode of a lithium-ion battery.

[0011] Surprisingly, it was found that low-temperature carbon coating treatment is effective in providing a carbon coating with sufficient graphite properties and the necessary conductivity for the coating, without adversely affecting the underlying structure of the precursor composite material particle core. Therefore, the method of the present invention provides an effective method for preparing core-shell composite material particles with high properties as electroactive materials.

[0012] Another advantage of the method of the present invention is that the surface area and pore volume are 100 m³ each. 2 It is applicable to materials exceeding 0.1 mL / g and 0.1 mL / g. In the open void system, carbon partially penetrates into the pore structure, allowing conductive tendrils to extend from the pyrolysis carbon coating into the interior of the particle. The coating combined with these conductive tendrils has the effect of shortening the average electron transport length in core-shell composite material particles. Instead, electrons can be transported to or from the current collector via the highly conductive carbon matrix during lithium insertion and emission.

[0013] The heat treatment temperature in step (b) is preferably less than 700°C. The heat treatment may be carried out at temperatures of, for example, 680°C or lower, 660°C or lower, 650°C or lower, 640°C or lower, 620°C or lower, or 600°C or lower.

[0014] The lower limit of the heat treatment temperature in step (b) is not limited. However, generally, the deposition of carbon coatings increases with increasing temperature. The minimum required temperature also depends on the type of carbon precursor used in the deposition step. The heat treatment temperature in step (b) is preferably at least 300°C, for example, at least 500°C, at least 520°C, at least 540°C, at least 560°C, or at least 580°C.

[0015] The carbon precursor may be in contact with the precursor composite material particles in one of two ways: 1. Contact of steam systems, 2. Contact with liquids or solutions.

[0016] A certain carbon precursor is suitable for only one of these two contact methods.

[0017] Another carbon precursor is suitable for both contact methods, depending on the temperature at which contact occurs. These carbon precursors may be in liquid form at low temperatures and sublimate into vapor precursors above the set temperature before thermal decomposition at high temperatures. They may also be placed in the precursor composite particle as liquids, if necessary. Examples of such compounds include camphor, anthracene, pentacene, and metal phthalocene complexes.

[0018] The pyrolysis carbon precursor may be in contact with the precursor composite material particles as a vapor, preferably as hydrocarbon vapor, during the heat treatment process. Suitable hydrocarbons include polycyclic hydrocarbons containing 10 to 25 carbon atoms and any 1 to 3 heteroatoms, and if necessary, the polycyclic hydrocarbons are selected from naphthalene, substituted naphthalenes such as di-hydroxynaphthalene, anthracene, tetracene, pentacene, fluorene, acenaphthene, phenanthrene, fluorene, pyrene, chrysene, perylene, coronene, fluorenone, anthraquinone, anthrone, and their alkyl-substituted derivatives. Also suitable pyrolysis carbon precursors include bicyclic monoterpenoids, and if necessary, the bicyclic monoterpenoids are selected from camphor, borneol, eucalyptol, camphene, carene, sabinene, thujene, and pinene. 10 Or C2~C 10 The hydrocarbons included are, if necessary, selected from alkanes, alkenes, alkynes, cycloalkanes, cycloalkenes, and arenes, such as methane, ethylene, propylene, acetylene, and cyclohexane. Other suitable pyrolysis carbon precursors include phthalocyanine, sucrose, starch, graphene oxide, reduced graphene oxide, pyrene, perhydropyrene, triphenylene, tetracene, benzopyrene, perylene, coronene, and chrysene. Preferably, the carbon precursor has acetylene, and more preferably, the carbon precursor is acetylene.

[0019] The hydrocarbon vapor may be contacted with a transition metal catalyst at a temperature of at least 500°C before contacting the precursor composite material particles. The transition metal catalyst may be selected from nickel, iron, cobalt, copper, and mixtures thereof, with nickel being most preferred. The transition metal catalyst may also be in the form of a mesh, which is placed in the vapor flow path before contacting the precursor composite material particles.

[0020] Alternatively, the transition metal catalyst may be placed on the surface of the precursor composite material particles. For example, prior to step (b), gaseous nickel carbonyl may be thermally decomposed to deposit nickel on the surface of the precursor composite material particles. If necessary, the nickel deposition may be carried out in the same reactor as in the heat treatment described above. A suitable temperature for the decomposition of nickel carbonyl is about 220 to 250°C. If necessary, after the deposition of the carbon coating, the nickel may be returned to nickel carbonyl vapor by contacting the coated particles with carbon monoxide gas, for example, at a temperature of 50 to 60°C. Thus, the nickel carbonyl gas may be recycled.

[0021] Transition metal catalytic treatment offers further improvements in the formation of pyrolytic carbon coatings at low temperatures. Furthermore, the recovery and recycling of nickel in the form of nickel carbonyl gas enhances the cost-effectiveness of the process.

[0022] Alternatively, the pyrolytic carbon precursor may be in contact with the precursor composite material particles in liquid form. In particular, the precursor composite material particles may be in contact with a dispersion or solution of the pyrolytic carbon precursor in a solvent, after which the solvent is removed, and precursor composite material particles coated with the pyrolytic carbon precursor are provided before heat treatment. Suitable pyrolytic carbon precursors for contact with precursor composite material particles in liquid form include oligomers containing polymers and carbon-containing backbones, for example, polyvinylpyrrolidone (PVP), or copolymers of vinylpyrrolidone with one or more other ethylenically unsaturated monomers.

[0023] Carbon precursor compounds that can be formed from solution include polydopamine, poly(diallyldimethylammonium chloride) (PDDA), citric acid, mixtures containing citric acid and ethanol, polyacrylonitrile (PAN), PAN derivatives, polymerized polypyrrole (PPy) complexes, melamine resins such as melamine-formaldehyde resin, pitch, glucose, sucrose, phenolic resins, polyvinyl alcohol (PVA), polyacrylic acid (PAA), resorcinol-formaldehyde resin, poly(methyl methacrylate) (PMMA), camphor, anthracene, pentacene, and metal phthalocene complexes.

[0024] If necessary, dopant materials may be introduced into the carbon coating. The dopant material may be introduced into the coating by incorporating a dopant precursor. Preferably, the dopant is boron or phosphorus. Doping of the pyrolytic carbon coating further enhances the conductivity of the coating. It is also preferable that electroactive material domains are doped by incorporating dopant materials into the carbon coating, further enhancing their conductivity.

[0025] If the pyrolysis carbon precursor is provided as a vapor, it may be used together with the gaseous precursor of the dopant material. When the dopant is boron, suitable gaseous dopant precursors include borane (BH3), diborane (B2H6), triisopropyl borate ([(CH3)2CHO]3B), triphenylborane ((C6H5)3B), and tris(pentafluorophenyl)borane (C6F5)3B, with diborane being preferred. When the dopant is phosphorus, a suitable gaseous dopant precursor is phosphine (PH3).

[0026] Furthermore, if the pyrolysis carbon precursor is a volatile liquid, the dopant may be introduced as a volatile liquid. In the case of boron, a suitable dopant precursor is triethylborane. In the case of phosphorus, a suitable dopant precursor is triethylphosphine.

[0027] When the pyrolysis carbon precursor is supplied as a solution or suspension, suitable boron dopant precursors include boric acid (H3BO3), sodium tetraborate (Na2[B4O5(OH)4].8H2O), borazine (B3H6N3), and ammonia borane (BH6N), with boric acid being the preferred source. When the dopant is phosphorus, suitable precursors include phosphoric acid (H3PO4), or phosphonates and phosphonic acid.

[0028] Another option when using a liquid, solution phase, or suspended pyrolytic carbon precursor is: For example, the dopant is introduced into the reactor as a gas in an inert gas stream supplied to the reactor headspace. Suitable gaseous dopant precursors include those mentioned above.

[0029] The outer shell of the conductive carbon material formed by the method of the present invention preferably has a thickness of 10 nm or less, 5 nm or less, 4 nm or less, 2 nm or less, or 1 nm or less after thermal decomposition.

[0030] The outer shell of the conductive carbon material formed by the method of the present invention may be amorphous, crystalline, or have both amorphous and crystalline domains. Preferably, the carbon coating is amorphous carbon. Preferred types of crystalline carbon coatings are graphite and graphene.

[0031] The porous carbon skeleton has a three-dimensionally interconnected network of open pores, which have micropores and / or mesopores, and optionally a small amount of macropores. According to conventional IUPAC terminology, in this application the term "macropore" is used to describe pores with a diameter of less than 2 nm, the term "mesopore" is used to describe pores with a diameter of 2 to 50 nm, and the term "macropore" is used to describe pores with a diameter greater than 50 nm.

[0032] References to the volumes of micropores, mesopores, and macropores in the porous carbon framework, as well as references to the pore volume distribution in the porous carbon framework, are intended to define the pore structure of the porous carbon framework when separation is considered. As a result of the occupation of pores by nanoscale electroactive material domains, a measurable decrease in pore volume occurs. However, this is not considered for the purpose of defining the pore structure of the porous carbon framework.

[0033] Using the quenched solid density functional theory (QSDFT) by the standard methods defined in ISO 15901-2 and ISO 15901-3, at 77 K, 10 -6 of the relative pressure p / p0 (or less than that) of nitrogen gas adsorption method, the total volume of micropores and mesopores and the pore size distribution of micropores and mesopores were determined. The nitrogen gas adsorption method is a technique for characterizing the porosity and pore diameter distribution of a material by condensing gas in the pores of a solid. As the pressure increases, gas first condenses in the pores with the smallest diameter, and the pressure increases until a saturation point where all pores are filled with liquid is reached. Next, the nitrogen gas pressure is gradually decreased so that the liquid evaporates from the system. By analyzing the adsorption and desorption isotherms and the hysteresis between them, the pore volume and pore diameter distribution are determined. Apparatus suitable for measuring the pore volume and pore diameter distribution by the nitrogen gas adsorption method include the TriStar II and TriStar II Plus porosity analyzers available from Micromeritics Instrument Corporation in the United States, and the Autosorb IQ porosity analyzer available from Quantachrome Instruments.

[0034] The nitrogen gas adsorption method is effective for measuring the pore volume and pore size distribution of pores with diameters up to 5 nm, but is less reliable for pores with larger diameters. Therefore, the nitrogen adsorption method for the purpose of the present invention is used to measure the pore volume and pore size distribution of only pores having a diameter of up to 50 nm (i.e., only micropores and mesopores). Similarly, PD 50This is determined only for the total volume of micropores and mesopores.

[0035] When measured by gas adsorption, porous conductive particles are found to be at least 0.4 cm 3 It is characterized by the total volume of micropores and mesopores per g (i.e., the total pore volume in the range of 0 to 50 nm). Typically, porous carbon skeletons contain both micropores and mesopores. However, the use of porous carbon skeletons that contain micropores but not mesopores, or porous carbon skeletons that contain mesopores but not micropores, is not ruled out.

[0036] More preferably, the total volume of micropores and mesopores in the porous conductive particles is at least 0.45 cm³. 3 / g, at least 0.5cm 3 / g, at least 0.55cm 3 / g, at least 0.6cm 3 / g, at least 0.65cm 3 / g, at least 0.7cm 3 / g, at least 0.75cm 3 / g, at least 0.8cm 3 / g, at least 0.85cm 3 / g, at least 0.9cm 3 / g, at least 0.95cm 3 / g, or at least 1cm 3 The value is / g. The use of conductive particles with high porosity is significant because it allows for the inclusion of a larger amount of silicon within the pore structure.

[0037] The internal pore volume of the porous conductive particles is appropriately capped at a value where the increased embrittlement of the porous conductive particles outweighs the benefits of increased pore volume in accommodating a larger amount of silicon. Preferably, the total volume of micropores and mesopores in the porous conductive particles is 2.2 cm³. 3 / g or less, 2cm 3 / g or less, 1.8cm 3 / g or less, 1.6cm 3 / g or less, 1.5cm 3 / g or less, 1.45cm3 / g or less, 1.4cm 3 / g or less, 1.35cm 3 / g or less, 1.3cm 3 / g or less, 1.25cm 3 Less than / g, or 1.2cm 3 It is less than / g.

[0038] In one example, the total volume of micropores and mesopores in porous conductive particles ranges from 0.7 to 2.2 cm³. 3 Range of / g, 0.7 to 2cm 3 Range of / g, 0.8 to 2cm 3 Range of / g, 0.8 to 1.8 cm 3 Range of / g, 0.9 to 1.8 cm 3 Range of / g, 0.9 to 1.6 cm 3 Range of / g, 1 to 1.6cm 3 Range of / g, or 1.1 to 1.6 cm 3 The range of / g is also acceptable.

[0039] In other examples, the total volume of micropores and mesopores in porous conductive particles ranges from 0.4 to 0.75 cm³. 3 / g, 0.4 to 0.7cm 3 / g, 0.4 to 0.65cm 3 / g, 0.45 to 0.75cm 3 / g, 0.45 to 0.7cm 3 / g, 0.45 to 0.65cm 3 / g, or 0.45 to 0.6 cm 3 The range of / g is also acceptable.

[0040] In other examples, the total volume of micropores and mesopores in porous conductive particles ranges from 0.6 to 2 cm³. 3 / g, 0.6 to 1.8cm 3 / g, 0.7 to 1.8cm 3 / g, 0.7 to 1.6 cm 3 / g, 0.8 to 1.6cm 3 / g, 0.8 to 1.5cm 3 / g, 0.8 to 1.4cm 3 / g, 0.9 to 1.5cm 3 / g, 0.9 to 1.4cm 3 / g, or 1 to 1.4cm 3 The range of / g is also acceptable.

[0041] The pore size distribution of porous conductive particles may be monomodal, bimodal, or multimodal. As used in this application, the term "pore size distribution" refers to the distribution of pore size relative to the cumulative total internal pore volume of the porous conductive particles. Bimodal or multimodal pore size distributions are preferred because the close accessibility between micropores and larger diameter pores provides the advantage of efficient ion transport to nanoscale electroactive material domains through the porous network.

[0042] Given the limitations of available analytical techniques, it is difficult to measure pore volume and pore size distribution across the entire range of micropores, mesopores, and macropores using a single technique. When a porous carbon skeleton has macropores, the volume of pores with diameters in the range of over 50 nm and under 100 nm can be measured by mercury porosimetry, which is preferably 0.3 cm². 3 Less than / g, or 0.20cm 3 Less than / g, or 0.1cm 3 Less than / g, or 0.05cm 3 It is preferable that the ratio is less than or equal to / g. A low proportion of macropores is beneficial in facilitating access of the electrolyte to the pore network, but the advantages of the present invention are substantially obtained by housing silicon in micropores and even smaller mesopores.

[0043] Pore ​​volumes measured by mercury porosimetry for pore sizes of 50 nm or less are ignored (as mentioned above, when using the nitrogen adsorption method, mesopores and micropores are characterized). Pore volumes measured by mercury porosimetry for pore sizes exceeding 100 nm are assumed to be interparticle porosity for the purposes of this invention and are therefore ignored.

[0044] Mercury porosimetry is a technique for characterizing the porosity and pore diameter 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 size of the pores. The values ​​obtained by the mercury porosimetry described herein were obtained in accordance with ASTM UOP578-11, with a surface tension γ of 480 mN / m and a contact angle φ of 140° for mercury at room temperature. The density of mercury at room temperature was 13.5462 g / cm³. 3 This method is adopted. Many high-precision mercury porosimetry meters are commercially available, such as the AutoPore IV series of automated mercury porosimetry meters sold by Micromerics Instrument Corporation in the United States. For a complete review of mercury porosimetry methods, see "Analytical Methods in Fine Particle Technology, 1997, Micromeritics Instrument Corporation, ISBN 0-9656783-0" by PAWebb and C. Orr.

[0045] It is understood that intrusion techniques such as gas adsorption and mercury porosimetry are effective only when determining the pore volume of pores that nitrogen or mercury can access from the outside of porous conductive particles. It is understood that the porosity values ​​specified in this application represent the volume of open pores, i.e., pores that are accessible to fluid from the outside of the porous carbon framework. When determining the porosity value, pores that are completely enclosed and cannot be identified by nitrogen adsorption or mercury porosimetry are not considered. Similarly, any pore volume located in pores so small that they fall below the detection limit by nitrogen adsorption is not considered.

[0046] The general term used in this application is "PD" n "Pore diameter" refers to the pore diameter as a percentage of the total volume of micropores and mesopores. For example, the term "PD" as used in this application. 90 "Pore diameter" is less than that, P 1PD represents the pore diameter in which 90% of the total volume of micropores and mesopores is observed. 50 The pore diameter is defined as the median pore diameter below which 50% of the total micropore and mesopore volume is observed.

[0047] Porous carbon skeleton PD 90 The pore diameter may be 20 nm or less, or 15 nm or less. Preferably, PD 90 The pore diameter is 12 nm or less, 10 nm or less, 8 nm or less, or 6 nm or less. Preferably, a porous carbon skeleton PD 90 The pore diameter is at least 3 nm, at least 3.2 nm, at least 3.5 nm, at least 3.8 nm, or at least 4 nm.

[0048] Porous carbon skeleton PD 30 The pore diameter is preferably 1.6 nm or less, 1.5 nm or less, 1.4 nm or less, 1.3 nm or less, 1.2 nm or less, 1.1 nm or less, or 1 nm or less. Preferably, the porous carbon skeleton PD 30 The pore diameter is preferably at least 0.45 nm, at least 0.5 nm, at least 0.6 nm, or at least 0.7 nm.

[0049] PD with a conductive multipore particle framework 50 The pore diameter is preferably 8 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, 3 nm or less, 2.5 nm or less, 2 nm or less, or 1.5 nm or less. Preferably, the porous carbon skeleton PD 50 The pore diameter is at least 1 nm, at least 1.1 nm, or at least 1.2 nm. Therefore, in the present invention, it is preferable that at least 50% of the total volume of micropores and mesopores within the conductive porous particle framework are in the form of pores with a diameter of less than 8 nm.

[0050] To avoid any ambiguity, macropore volume (pore diameter greater than 50 nm) is defined as PD. 50 It is not considered for the purpose of determining the value.

[0051] Generally, precursor composite material particles are in the range of 1 to 50 μm. 50 The particle diameter may be. Optionally, the D of the precursor composite material particles. 50 The particle diameter may be at least 1.5 μm, at least 2 μm, at least 3 μm, at least 4 μm, or at least 5 μm. If necessary, the D of the precursor composite material particles. 50 The particle diameter may be 40 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 18 μm or less, 15 μm or less, 12 μm or less, or 10 μm or less.

[0052] For example, the precursor composite material particles are in the range of 1 to 25 μm, 1 to 20 μm, 2 to 25 μm, 2 to 20 μm, 2 to 18 μm, 3 to 20 μm, 3 to 18 μm, 3 to 15 μm, 4 to 18 μm, 4 to 15 μm, 4 to 12 μm, 5 to 15 μm, 5 to 12 μm, or 5 to 10 μm. 50 The particles may have a particle diameter. Precursor composite material particles within these size ranges and having the porosity and pore diameter distribution described in this application are ideally suited for the preparation of composite material particles used in the anodes of metal-ion batteries. These particles provide core-shell composite material particles that exhibit good dispersibility in slurries, structural robustness, high capacity retention over repeated charge-discharge cycles, and suitability for forming dense electrode layers of uniform thickness in the conventional 20 to 50 μm thickness range.

[0053] To avoid ambiguity, the term "particle diameter" as used in this application refers to the equivalent spherical diameter (esd), i.e., the diameter of a sphere having the same volume as a given particle, and the particle volume is understood to include the volume of any pores within the particle. 50 " and "D 50 "Particle diameter" refers to the volume-based median particle diameter, i.e., the diameter below which less than 50% of the particle population is recognized. The term "D" as used in this application. 10 " and "D 10 "Particle diameter" refers to the median particle diameter based on 10 percent volume, i.e., the diameter below which less than 10 volume percent of the particle population is recognized. The term "D" as used in this application. 90" and "D 90 "Particle diameter" refers to the median particle diameter based on 90 percent volume, i.e., the diameter below which less than 90 percent of the particle population is observed.

[0054] Particle diameter and particle size distribution can be measured by standard laser diffraction methods in accordance with ISO 13320:2009. Laser diffraction relies on the principle that particles scatter light at angles that vary with particle size, and that the aggregate of particles forms a pattern of scattered light determined by intensity and angle correlated with the particle size distribution. Many laser diffraction devices are commercially available for rapid and reliable particle size distribution measurement. Unless otherwise specified, the particle size distribution measurements described or reported in this application were measured using a conventional Malvern Mastersizer™ 3000 particle size analyzer manufactured by Malvern Instruments. The Malvern Mastersizer™ 3000 particle size analyzer operates by irradiating a helium-neon gas laser beam through a transparent cell containing particles of interest suspended in an aqueous solution. The light beam irradiated onto the particles is scattered at angles inversely proportional to the particle size, and a photodetector array measures the intensity of the light at several predetermined angles. The intensities measured at different angles are processed by a computer using standard theoretical principles to determine the particle size distribution. The laser diffraction values ​​described in this application are obtained using the wet dispersion of particles in distilled water. The particle refractive index is 3.50, and a dispersant index of 1.330 is used. The particle size distribution is calculated using the Mie scattering model.

[0055] D of precursor composite material particles 10 The particle diameter is preferably at least 0.2 μm, at least 0.5 μm, at least 0.8 μm, at least 1 μm, at least 1.5 μm, or at least 2 μm. 10 By maintaining a particle diameter of 0.2 μm or larger, the possibility of undesirable aggregation of submicron-sized particles is reduced, resulting in improved flow behavior and better dispersibility of the formed composite material particles.

[0056] D of the precursor composite material particles 90 The particle diameter is preferably 40 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less. The use of larger precursor composite material particles results in non-uniform formation packing of the core-shell composite material particle product in the electrode active layer, thus preventing the formation of a dense electrode layer, particularly an electrode layer having a thickness in the range of 20 to 50 μm.

[0057] The precursor composite material particles preferably have a narrow size distribution span. For example, the particle size distribution span ((D 90 -D 10 ) / D 50 as defined) is preferably 5 or less, more preferably 4 or less, more preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. By maintaining a narrow size distribution span, it becomes possible to easily achieve efficient packing of the core-shell composite material particle product for a dense electrode layer.

[0058] The porous carbon skeleton preferably contains at least 80% by mass of carbon, more preferably at least 90% by mass of carbon, more preferably at least 95% by mass of carbon, and, if necessary, at least 98% by mass or at least 99% by mass of carbon. The carbon may be crystalline carbon, or amorphous carbon, or a mixture of amorphous and crystalline carbon. The porous carbon particles may be either hard carbon particles or soft carbon particles and may be suitably obtained by known procedures including thermal decomposition of polymers. Porous carbon particles of various different specifications are available from commercial suppliers.

[0059] The precursor composite particles may have different ranges of electroactive material loads. For example, the amount of electroactive material in the precursor composite particles may be selected such that the electroactive material occupies at least 25% and up to 80% or more of the internal pore volume of the porous carbon skeleton. For example, the electroactive material may occupy 25% to 60%, 25% to 55%, 25% to 50%, 25% to 45%, or 25% to 40% of the internal pore volume of the porous carbon skeleton. Within these preferred ranges, the pore volume of the porous carbon skeleton effectively accommodates the expansion of the electroactive material during charging and discharging, avoiding excess pore volume that does not contribute to the volumetric capacity of the core-shell composite particles. However, the amount of electroactive material is not high enough so that effective lithiation is hindered by an inadequate metal ion diffusion rate or mechanical resistance to lithiation arises due to an inadequate expansion volume.

[0060] The electroactive material in the precursor composite particle is preferably selected from silicon, tin, germanium, aluminum, and mixtures thereof. The preferred electroactive material is silicon.

[0061] When the electroactive material is silicon, the preferred mass ratio of silicon to the porous carbon skeleton is [0.5 × P 1 The range is from 1.3 × P1:1, where P1 is a dimensionless quantity representing the magnitude of the total pore volume of micropores and mesopores in porous conductive particles, and cm 3 / g units (for example, porous carbon particles are 1.2cm 3 If the total volume of micropores and mesopores is given by / g, P1 is expressed as P1 = 1.2). This formula takes into account the density of silicon and the pore volume of porous conductive particles, and, assuming that silicon is completely contained within the internal pore volume, determines the weight ratio of silicon that occupies approximately 20% to 55% of the pore volume.

[0062] In practice, it is preferable that at least 90% by weight, more preferably at least 95% by weight, and even more preferably at least 98% by weight of the electroactive material in the precursor composite particles be located within the internal pore volume of the porous carbon skeleton, and that very little or no silicon is located on the outer surface of the precursor composite particles. Preparation of precursor composite particles by chemical vapor impregnation (CVI) is an effective method that can ensure that only a very small amount of electroactive material is located on the external surface. This is because the reaction rate of the CVI process is favorable for silicon deposition into small pores, and therefore preferential silicon deposition occurs on the internal surface of the porous conductive particles.

[0063] The heat treatment in step (b) may preferably be carried out for 1 to 3 hours.

[0064] Step (a) of providing multiple precursor composite material particles may include contacting the electroactive material precursor with multiple porous carbon particles at a temperature of 200 to 800°C, thereby forming an electroactive material film within the pores of the carbon particles. The electroactive material may be selected from silicon, tin, germanium, aluminum, and mixtures thereof. A preferred electroactive material is silicon.

[0065] Suitable gaseous precursors for silicon film deposition include silane (SiH4) and trichlorosilane (SiHCl3). The CVI method is particularly useful for preparing the electroactive materials disclosed herein because it causes very little damage to the geometric shape of the porous substrate.

[0066] Suitable silicon-containing precursors include silane (SiH4), disilane (Si2H6), trisilane (Si3H8), and tetrasilane (Si4H 10) or chlorosilanes such as trichlorosilane (HSiCl3), or methylchlorosilanes such as methyltrichlorosilane (CH3SiCl3) or dimethyldichlorosilane ((CH3)2SiCl2). Preferably, the silicon-containing precursor is silane. Suitable tin-containing precursors include bis[bis(trimethylsilyl)amino]tin(II) ([(CH3)3Si]2N)2Sn), tetraallyltin (((H2C=CHCH2)4Sn), tetrakis(diethylamide)tin(IV) ([(C2H5)2N]4Sn), tetrakis(dimethylamide)tin(IV) ([(CH3)2N]4Sn), tetramethyltin (Sn(CH3)4), tetravinyltin (Sn(CH=CH2)4), tin(II) acetylacetonate (C 10 H 14 O4Sn), trimethyl(phenylethynyl)tin (C6H5C≡CSn(CH3)3), and trimethyl(phenyl)tin (C6H5Sn(CH3)3). Preferably, the tin-containing precursor is tetramethyltin.

[0067] Suitable aluminum-containing precursors include aluminum tris(2,2,6,6-tetramethyl-3,5-heptanedionate) (Al(OCC(CH3)3CHCOC(CH3)3)3), trimethylaluminum ((CH3)3Al), and tris(dimethylamide)aluminum(III) (Al(N(CH3)2)3). Preferably, the aluminum-containing precursor is trimethylaluminum.

[0068] Suitable germanium-containing precursors include germane (GeH4), hexamethyldigermane ((CH3)3GeGe(CH3)3), tetramethylgermanium ((CH3)4Ge), tributylgermanium hydride ([CH3(CH2)3]3GeH), triethylgermanium hydride ((C2H5)3GeH), and triphenylgermanium hydride ((C6H5)3GeH). Preferably, the germanium-containing precursor is germane.

[0069] [[ID=1The CVI process may also utilize a gaseous precursor of the dopant material to deposit the doped electroactive material onto micropores and / or mesopores of a porous carbon skeleton. When the dopant is boron, suitable precursors include borane (BH3), diborane (B2H6), triisopropyl borate ([(CH3)2CHO]3B), triphenylborane ((C6H5)3B), and tris(pentafluorophenyl)borane (C6F5)3B, preferably borane. When the dopant is phosphorus, a suitable precursor is phosphine (PH3).

[0070] The precursor may be used in its pure form or, more commonly, as a mixture diluted with an inert carrier gas such as nitrogen or argon. For example, the precursor may be used in amounts ranging from 0.5 to 20 vol%, or 1 to 10 vol%, or 1 to 5 vol%, relative to the total volume of the precursor and the inert carrier gas. The CVI process is preferably carried out at a low partial pressure of the gaseous precursor, with a total pressure of 101.3 kPa (i.e., atmospheric pressure, 1 atm) or close to it, and the remaining partial pressure is brought to atmospheric pressure using an inert padding gas such as hydrogen, nitrogen, or argon. The presence of oxygen must be minimized, following conventional procedures operated in an inert atmosphere, to prevent undesirable oxidation of the deposited electroactive material. Preferably, the oxygen content is less than 0.01 vol%, more preferably less than 0.001 vol%, relative to the total volume of gas used in step (b).

[0071] The temperature of the CVI process is preferably selected to thermally decompose the precursor into an electroactive material. The CVI process is preferably carried out at temperatures in the range of 200 to 800°C, 400 to 700°C, 400 to 600°C, 400 to 550°C, 450 to 550°C, and 450 to 500°C. Preferably, the CVI process is carried out at temperatures in the range of 400 to 500°C, more preferably 450 to 500°C.

[0072] The surface of electroactive materials deposited by the CVI method is reactive to oxygen, and when exposed to atmospheric oxygen, a native oxide layer is formed. In the case of silicon, when the silicon surface is exposed to oxygen, an amorphous silicon dioxide film is rapidly formed. The formation of the native oxide layer is a reactive process, and therefore careful process control is required to prevent overheating or combustion of the particulate material during manufacturing. The presence of the native oxide layer can lead to irreversible capacity loss and shortened cycle life, and therefore can be detrimental to the properties of electroactive materials in lithium-ion batteries. Therefore, it is preferable that electroactive materials are not exposed to oxygen before the deposition of lithium-ion permeable filler materials.

[0073] More preferably, step (b) of the method of the present invention further comprises the step (b2) of bringing the surface of the deposited electroactive material into contact with a passivating agent, wherein the electroactive material is not exposed to oxygen before contact with the passivating agent. Here, the passivating agent is defined as a compound that can modify the surface of the electroactive material in such a way as to inhibit or prevent the formation of surface oxides.

[0074] Suitable passivators include compounds containing alkenes, alkynes, or carbonyl functional groups, more preferably compounds containing terminal alkenes, terminal alkynes, or aldehyde groups.

[0075] Suitable passivators include one or more of the following chemical formulas: (i) R - CH = CH - R; (ii) RC ≡ CR; (iii) O = CH - R; Here, R represents an H or an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, preferably 2 to 10 carbon atoms, or the two R groups in formula (i) form an unsubstituted or substituted hydrocarbyl ring structure containing 3 to 8 carbon atoms. Particularly preferred passivators include one or more compounds of the following formulas: (i) CH2 = CH-R; (ii) HC ≡ CR; Here, R is defined as described above. Preferably, R is unsubstituted.

[0076] Examples of suitable compounds include ethylene, propylene, 1-butene, butadiene, 1-pentene, 1,4-pentadiene, 1-hexene, 1-octene, styrene, divinylbenzene, acetylene, phenylacetylene, norbornene, norbornadiene, and bicyclo[2.2.2]octo-2-ene. Mixtures of different passivators may also be used.

[0077] It is understood that the alkenes, alkynes, or carbonyl groups of passivators undergo insertion reactions via MH groups on the surface of electroactive materials (where M represents an atom of the electroactive material), forming a covalently passivated surface resistant to oxidation by air. When silicon is the electroactive material, the passivation reaction between the silicon surface and the passivator may be understood as a form of hydrosilylation, as schematically shown below.

[0078] [ka] Other suitable passivators include compounds containing active hydrogen atoms bonded to oxygen, nitrogen, sulfur, or phosphorus. For example, the passivator may be an alcohol, amine, thiol, or phosphine. It is understood that the reaction between the -XH group and the hydroxyl group on the surface of the electroactive material results in the removal of H2 and the formation of a direct bond between X and the surface of the electroactive material.

[0079] Suitable passivators in this category include compounds of formula HX-R, where X represents O, S, NR, or PR, and each R is independently defined as above. The two R groups in formula (iv) may form an unsubstituted or substituted hydrocarbyl ring structure containing 3 to 8 carbon atoms. Preferably, X represents O or NH, and optionally, R represents a substituted aliphatic or aromatic group having 2 to 10 carbon atoms. The amine group may also be incorporated into a 4 to 10-membered aliphatic or aromatic ring structure, such as pyrrolidine, pyrrole, imidazole, piperazine, indole, or purine. The contact step between the electroactive material and the passivator in step (b2) may be carried out at a temperature in the range of 25 to 700°C. For example, step (b2) may be appropriately carried out within the preferred temperature range of step (b) and / or step (c) described herein. Preferably, step (c) is carried out at the same temperature as step (b2), or at a higher temperature. For example, step (b2) may be carried out at a temperature in the range of 25°C to less than 500°C, and step (c) may be carried out at a temperature in the range of 500°C to 700°C.

[0080] After passivation of the electroactive material surface, a lithium-ion permeable filler material may be deposited in step (c) as described above. The R groups of the passivating agent may be incorporated into the lithium-ion permeable filler via the passivating agent so as to form covalent bonds between the lithium-ion permeable filler and the surface of the electroactive material.

[0081] If the lithium-ion permeable filler material is a conductive pyrolytic carbon material, the same compound may function as both a passivator and a pyrolytic carbon precursor. For example, if styrene is selected as the pyrolytic carbon precursor, it will also function as a passivator if the electroactive material is not exposed to oxygen before contact with the styrene. Thus, step (c) may include a step of depositing a conductive pyrolytic carbon material by a CVI process. The pyrolytic carbon precursor is the same as the passivator used in step (b2). In this case, the passivation in step (b2) and the deposition of the conductive carbon material in step (c) may be carried out simultaneously at a temperature, for example, in the range of 500 to 700°C. Alternatively, the passivation in step (b2) and the deposition of the conductive carbon material in step (c) may be carried out sequentially using the same material as the passivator and pyrolytic carbon precursor, except that step (c) is carried out at a higher temperature than step (b2). For example, step (b2) may be carried out at a temperature in the range of 25°C to less than 500°C, and step (c) may be carried out at a temperature in the range of 500°C to 700°C.

[0082] Alternatively, different compounds may be used as the passivator in step (b2) and the pyrolysis carbon precursor in step (c). For example, the electroactive material may first be contacted with a passivator in step (b2), and then a conductive pyrolysis carbon material film may be formed in step (c), where the pyrolysis carbon precursor used in step (c) is different from the passivator used in step (b2). For example, the passivator in step (b2) may be styrene, and the pyrolysis carbon precursor in step (c) may be a compound such as cyclohexane. Cyclohexane is a compound that can form a pyrolysis carbon material but cannot passivate the surface of the electroactive material. If the passivator and the pyrolysis carbon precursor are different materials, steps (b2) and (c) may be carried out at the same temperature, for example, in the range of 500 to 700°C. Alternatively, step (c) may be carried out at a higher temperature than step (b2). For example, step (b2) may be carried out at a temperature in the range of 25°C to less than 500°C, and step (c) may be carried out at a temperature in the range of 500°C to 700°C.

[0083] Another suitable passivating agent is ammonia. Therefore, step (b2) may include contacting the surface of the deposited electroactive material with ammonia at a temperature in the range of 200 to 800°C, preferably in the range of 400 to 700°C. For example, if the passivating agent is ammonia, step (b2) may be carried out at the same temperature used when depositing the electroactive material in step (b). The temperature may then be raised to the range of 500 to 1,000°C if necessary, to the crystalline nitride surface (e.g., SiN). x A silicon nitride surface (where x ≤ 4 / 3) is formed. Thus, passivation with ammonia provides another means of suppressing the oxidation of the electroactive material. Since substoichiometric silicon nitride is conductive, this step further leads to the formation of a conductive network that allows for faster charging and discharging of the electroactive material.

[0084] When the electroactive material is silicon, it is preferable that the silicon be amorphous. The amorphous nature of silicon can be measured by X-ray diffraction (XRD), and Figure 3 shows the case of Example 4.

[0085] One of the advantages of the present invention is that the temperature of the carbon coating process can suppress or substantially avoid annealing of the microstructure of the composite material particles. The microstructure of the composite material particles can be evaluated by TGA analysis. This analytical method is based on the principle that when elemental silicon is oxidized to silicon dioxide (SiO2) in air at high temperatures, a weight increase is observed. The mechanism of Si oxidation is temperature-dependent. Silicon atoms on the surface of silicon nanostructures are oxidized at a lower temperature than silicon atoms in the bulk of the silicon nanostructure (Reference: Bardet et al., Phys.Chem.Chem.Phys. (2016), 18, 18201). TGA analysis can quantify the relative amount of surface silicon based on the weight increase observed when silicon is oxidized to silicon dioxide (SiO2) in air at high temperatures. By plotting the weight increase against temperature, fine silicon and coarse silicon in the sample can be distinguished and quantified.

[0086] As shown in Figure 1, the amount of unoxidized surface silicon is determined from the property TGA traces of these materials. After an initial decrease in mass continues up to about 300°C (shown in Figure 1 as the mass decrease from (a) to (b)), a large mass increase is observed starting at about 400°C, with a peak between 550°C and 650°C (shown in Figure 1 as the mass increase from (b) to (c)). Subsequently, as the porous carbon skeleton is oxidized to CO2 gas, a mass decrease is observed (mass decrease from (c)), and then, above about 800°C, a mass increase is observed again in response to the continuous change of silicon to SiO2. This increases towards an asymptotic value above 1000°C as the oxidation of silicon approaches completion (mass increase from (d) to (e)). The temperature at which the weight increase occurs is related to the structure of silicon; on the surface of the silicon structure, silicon is oxidized at lower temperatures, while bulk silicon is oxidized at higher temperatures. Therefore, at higher temperatures, the silicon domains become coarser, and more oxidation is observed.

[0087] In this application, coarse silicon is defined as silicon that is oxidized above 800°C as measured by TGA. Here, TGA is performed under air with a heating rate of 10°C / min. This is shown in Figure 1 as the mass increases from (d) to (e). Therefore, the coarse bulk silicon content is determined according to the following formula: Z = 1.875 × [(M f -M 800 ) / M f ] × 100% Here, Z is the percentage of unsilicon oxide at 800°C, and M 800 This is the mass of the sample at 800°C (mass (d) in Figure 1), M fThis is the mass of ash at the completion of oxidation at 1400°C (mass (e) in Figure 1). In this analysis, any mass increase at temperatures above 800°C corresponds to the oxidation of silicon to SiO2, and it is assumed that the total mass at the completion of oxidation is SiO2. For perfection, 1.875 is understood to be the molar mass ratio of SiO2 to O2 (i.e., the mass ratio of formed SiO2 to the mass increase due to the addition of oxygen).

[0088] In a second aspect of the present invention, a particulate material is provided comprising a plurality of core-shell composite material particles obtained by the method described above.

[0089] In a third aspect of the present invention, A particulate material composed of multiple core-shell composite material particles, The core-shell composite material particles are (a) core, (i) A porous carbon skeleton having micropores and / or mesopores, wherein the micropores and / or mesopores are measured by gas adsorption and are at least 0.4 cm 3 The total pore volume of the porous carbon skeleton is PD 50 A porous carbon skeleton having a pore diameter of 10 nm or less, preferably 5 nm or less, (ii) A plurality of electroactive material domains arranged within the micropores and / or mesopores of the porous carbon skeleton, A core having, (b) an outer shell of a pyrolytic conductive carbon material surrounding at least a portion of the core, A particulate material having the following characteristics is provided.

[0090] If necessary, the thermally decomposable conductive carbon coating may also penetrate into the pores of the porous carbon skeleton.

[0091] Core-shell composite material particles may have different ranges of electroactive material fillers. For example, the amount of electroactive material in the precursor composite material particles may be selected such that the electroactive material occupies at least 25% and up to 80% or more of the internal pore volume of the porous carbon skeleton. For example, the electroactive material may occupy 25% to 60%, 25% to 55%, 25% to 50%, 25% to 45%, or 25% to 40% of the internal pore volume of the porous carbon skeleton. Within these preferred ranges, the pore volume of the porous carbon skeleton effectively accommodates the expansion of the electroactive material during charging and discharging, and excess pore volume that does not contribute to the volumetric capacity of the core-shell composite material particles is avoided. However, the amount of electroactive material is not high enough to create mechanical resistance to lithiation due to inadequate metal ion diffusion rates or inadequate expansion volume, thereby hindering effective lithiation.

[0092] The electroactive material in the precursor composite particle is preferably selected from silicon, tin, germanium, aluminum, and mixtures thereof. The preferred electroactive material is silicon.

[0093] The core-shell composite material particles are preferably substantially free of silicon carbide. The core-shell composite material particles are preferably substantially free of silicon nitride. The presence or absence of silicon carbide and silicon nitride can be determined by X-ray diffraction (XRD) analysis. Suitable apparatus and methods for this are well known to those skilled in the art.

[0094] Core-shell composite material particles are in the range of 1.5 to 60 μm. 50 It is preferable that the particles have a diameter.

[0095] If necessary, D of core-shell composite material particles 50 The particle diameter may be at least 2 μm, at least 3 μm, at least 4 μm, or at least 5 μm. If necessary, the D of the core-shell composite material particles. 50The particle diameter may be 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 18 μm or less, or 15 μm or less.

[0096] For example, core-shell composite material particles are in the range of 2 to 50 μm, 2 to 40 μm, 2 to 30 μm, 3 to 30 μm, 3 to 25 μm, 3 to 20 μm, 4 to 25 μm, 4 to 20 μm, 4 to 18 μm, 5 to 20 μm, 5 to 18 μm, and 5 to 15 μm. 50 The particles may have a particle diameter. Core-shell composite material particles within these size ranges and having the porosity and pore diameter distribution described herein are ideally suited for the preparation of composite material particles used in anodes for metal-ion batteries. This is due to their good dispersibility in slurries, structural robustness, high capacity retention over repeated charge-discharge cycles, and suitability for forming dense electrode layers of uniform thickness in the conventional thickness range of 20 to 50 μm.

[0097] Core-shell composite material particles are 50m 2 It is preferable to have a BET surface area of ​​30m² or less, and preferably 30m². 2 / g or less, more preferably 15m 2 / g or less, or 12m 2 / g or less, or 10m 2 / g or less, or 8m 2 / g or less, or 6m 2 / g or less, or 5m 2 The amount is less than / g. The composite material particles are at least 0.1m 2 / g, or at least 0.5m 2 / g, at least 1m 2 / g, or at least 2m 2 / g, or at least 3m 2 It has a BET surface area of ​​ / g.

[0098] The particulate material of the present invention may have a specific capacity of 1200 to 2340 mAh / g when lithium-ionized. This is measured per unit gram of particulate material.

[0099] A fourth aspect of the present invention provides a composition comprising a particulate material according to the second or third aspect of the present invention and at least one other component, the at least one other component which may be preferably selected from one or more of (i) a binder, (ii) a conductive additive, and (iii) an additional particulate electroactive material. The composition according to the fourth aspect of the present invention may be used in particular as an active layer in the anode of a metal-ion battery.

[0100] The composition may contain 1 to 95% by weight, 2 to 90% by weight, 5 to 85% by weight, or 10 to 80% by weight of the particulate material of the present invention, based on the total dry weight of the composition.

[0101] The binder may be present in an amount of 0.5 to 20% by weight, or 1 to 15% by weight, or 2 to 10% by weight, based on the total dry weight of the electrode composition.

[0102] One or more conductive additives may be present in a total amount of 0.5 to 20% by weight, or 1 to 15% by weight, or 2 to 10% by weight, based on the total dry weight of the electrode composition.

[0103] Any at least one additional particulate electroactive material may be selected from graphite, hard carbon, silicon, tin, germanium, gallium, aluminum, and lead.

[0104] In a fifth aspect, the present invention provides an electrode having a particulate material according to a second or third aspect of the present invention, which is electrically in contact with a current collector. If necessary, the particulate material may be in the form of a composition according to a fourth aspect of the present invention.

[0105] In a sixth aspect, the present invention provides a rechargeable metal-ion battery, (i) an anode comprising an electrode according to a fifth aspect of the present invention, (ii) A cathode having a cathode active material that can release and reabsorb metal ions, (iii) The electrolyte between the anode and the cathode, A rechargeable metal-ion battery having the following properties is provided.

[0106] In a seventh aspect, the present invention provides the use of a particulate material according to a second or third aspect of the present invention as an anodic active material. In this use, the particulate material may be in the form of a composition of the present invention.

[0107] The present invention will be described below with reference to examples and accompanying drawings. [Brief explanation of the drawing]

[0108] [Figure 1] This figure shows a characteristic TGA trace of the particulate material according to the present invention, with a low level of coarse silicon. [Figure 2] This figure shows the thermogravimetric analysis (TGA) data for Example 4. [Figure 3] This figure shows the X-ray diffraction (XRD) data for Example 4. [Figure 4] This figure shows the cell data for Example 5. [Figure 5] This figure shows the effect of temperature on the coarse silicon content in Example 4. [Figure 6] This figure shows the XRD data for Example 6. [Figure 7] This figure shows the effect of temperature on the amount of coarse silicon in Example 7. [Figure 8] This figure shows the effect of temperature on capacity retention over 100 cycles. The numbers for each data point indicate the level of coarse silicon. [Figure 9] This figure shows the effect of temperature on capacity retention over 200 cycles. The numbers for each data point indicate the level of coarse silicon. [Modes for carrying out the invention]

[0109] (example) The porous carbon skeletons C1 to C3 used in the following examples have the characteristics shown in Table 1.

[0110] [Table 1] (Example 1: Preparation of particulate materials in a fluidized bed reactor) Silicon-carbon composite particles were prepared in a vertical-bubble fluidized bed reactor having a stainless steel cylindrical container with an inner diameter of 83 mm. The amount of carbon skeleton particle powder having the properties described in Table 1 was placed in the reactor. An inert gas (nitrogen) was injected into the reactor at a low flow rate to remove oxygen. The reactor was then heated to a reaction temperature between 430 and 500°C, and 4 vol% monosilane gas diluted with nitrogen was supplied to the bottom of the reactor at a flow rate sufficient to fluidize the carbon skeleton particles over a length sufficient to deposit the target mass of silicon. The reactor was purged under nitrogen for 30 minutes and then cooled to room temperature over several hours. The atmosphere was then gradually switched to air over 2 hours by switching the gas flow from nitrogen to air from a compressed air supply.

[0111] (Example 2: Preparation of particulate materials in a static furnace) Silicon-carbon composite particles were prepared by arranging 1.8 g of particulate porous framework having the properties described in Table 1 on a stainless steel plate, with a constant thickness of 1 mm along its entire length. The plate was then placed inside a stainless steel tube with an outer diameter of 60 mm. This tube had gas inlet and outlet lines located in the high-temperature zone of a retort furnace. After purging the furnace tube with nitrogen gas for 30 minutes at room temperature, the sample temperature was raised from 450 to 475°C. The nitrogen gas flow rate was adjusted to ensure a gas residence time of at least 90 seconds in the furnace tube and to maintain this flow rate for 30 minutes. Next, the gas supply was switched from nitrogen to a mixed gas containing 1.25 vol% monosilane in nitrogen. Monosilane administration was carried out over a period of up to 5 hours. The reactor pressure was maintained at 101.3 kPa (1 atm). After administration was complete, the gas flow rate was kept constant while the silane was purged from the furnace with nitrogen. After the furnace is purged under nitrogen for 30 minutes, it is cooled to room temperature over several hours. Next, the atmosphere is gradually switched to air over two hours by switching the gas flow from nitrogen to air from a compressed air supply.

[0112] (Example 3: Measurement of weight % of coarse silicon) The procedure used to calculate the coarse silicon content for the composite materials in the examples was as follows: 10-20 mg of the test sample was packed into a 70 μL crucible. The sample was loaded into a Mettler Toledo TGA / DSC3+ instrument. Ar purge gas, N2 padding gas, and air reaction gas were used at a rate of 100 mL / min. The chamber of the TGA furnace was heated from 25°C to 1400°C at a rate of 10°C / min. Data was collected at 1-second intervals.

[0113] The amount of coarse silicon was determined by calculating the final mass of the ash at the end of the TGA test and its mass at 800°C. The coarse silicon (Z) value was calculated using the formula described above.

[0114] (Example 4 - Heat treatment of uncoated particles) Silicon-carbon composite particles were prepared using 125 g of carbon C1 and the method of Example 1. The silicon-carbon composite particles were separated into five samples. Next, each sample was individually jet-milled for 25 minutes using a Hosokawa Alpine 50 AS spiral jet mill at a supply gas pressure of 8 bar and a supply speed of 8 rpm. After jet milling, and before any heat treatment step, the obtained volume particle size distribution was measured using laser diffraction as described above, and Table 2 was obtained.

[0115] The first sample was used as a reference sample and was not subjected to any other processing. The remaining four samples were flashed in an argon stream at a flow rate of 1 L / min for 30 minutes, then heated at a rate of 5°C / min to the corresponding heat treatment temperatures of 600°C, 700°C, 800°C, or 900°C, and held at the heat treatment temperature for 1 hour. After heat treatment, the properties of the silicon-carbon composite precursor particles were measured and compared with the reference sample.

[0116] (result) Reference samples and heat-treated samples were subjected to various analyses, and the effects of different temperatures on material properties were compared.

[0117] Thermogravimetric analysis (TGA) in air (Figure 2) revealed that samples subjected to heat treatment at 800°C and 900°C suffered from heat treatment of the fine micropore structure and the formation of larger silicon domains through the fusion of nanoscale silicon domains within the pore structure. Samples heat-treated at 600°C showed a TGA profile very similar to the reference sample, indicating that the carbon coating process on these silicon-carbon composite precursor particles is highly unlikely to damage the fine micropore structure. This is highly desirable for the use of particulate materials in anodes.

[0118] Figure 5 shows the amount of coarse silicon measured by the method of Example 3 for each sample. The reference sample is represented as 430, and the other samples are represented by the temperature of the heat treatment process to which they were subjected. Fine silicon is preferable to coarse silicon in the final product. Figure 5 shows that in any treatment process carried out at temperatures above 700°C, the final particulate product tends to have a higher proportion of coarse silicon compared to products treated at temperatures below 700°C (e.g., carbon-coated products).

[0119] The total pore volume and BET surface area were evaluated using the method described above.

[0120] [Table 2] These data indicate that the total pore volume decreases as the processing temperature increases. The total pore volume obtained for samples at 800°C and 900°C was reduced to an undesirable level, which can be explained by the heat treatment of the pores at these high temperatures.

[0121] The total pore volume and BET surface area depend on the particle size of the sample. The increase in BET surface area and total pore volume of the sample heat-treated at 600°C compared to the reference sample is explained by the fact that the sample heat-treated at 600°C has a larger particle size than all other samples because the sample was individually jet-milled.

[0122] The chemical composition of the five samples was further analyzed using X-ray diffraction (XRD). The results are shown in Figure 3.

[0123] Up to 700°C, and especially broadly up to 600°C, the characteristics of amorphous silicon, i.e., broad peaks, are observed. In the samples at 700°C, 800°C, and 900°C, the degree of change in crystalline silicon is observed, which is particularly pronounced in the 800°C and 900°C samples.

[0124] Furthermore, evidence of silicon carbide is clearly visible even in samples at 900°C. The formation of silicon carbide is undesirable for silicon-carbon composite particles because it does not exhibit electrochemical activity and has poor conductivity. Therefore, the formation of this compound reduces the overall effectiveness of the product in relation to the anode.

[0125] Furthermore, electrodes were tested. Each electrode was fitted with one of the particulate material test samples.

[0126] (Example 5 - Electrochemical Test) A test coin cell was fabricated using a negative electrode containing a composite material prepared as described in Example 4. Carbon Super P (conductive carbon) was dispersed in a CMC binder and mixed in a Thinky™ mixer. A silicon-based material was added to the mixture and mixed in a Thinky™ mixer for 30 minutes. Next, an SBR binder was added to achieve a 1:1 CMC:SBR ratio to obtain a slurry with a weight ratio of silicon-based material:CMC / SBR:conductive carbon of 70%:16%:14%. The slurry was further mixed in a Thinky™ mixer for 30 minutes. Next, it was coated onto a 10 μm thick copper substrate (current collector) and dried at 50°C for 10 minutes. Further drying at 110°C for 12 hours formed an electrode with an active layer on the copper substrate.

[0127] Using an annular electrode with a radius of 0.8 cm cut from an electrode, a coin half-cell was prepared containing a porous polyethylene separator, lithium foil as a counter electrode, and an electrolyte containing 1 M LiPF6 in a 7:3 EC / FEC (ethylene carbonate / fluoroethylene carbonate) solution containing 3 wt% vinylene carbonate.

[0128] Using these half-cells, the initial volumetric energy density (VED2, mAh / cm³) is calculated. 3The first cycle loss (FCL) and the first delithiation capacity of the active layer (DC1) were measured. Half a cell was evaluated by applying a constant current of C / 25 (where "C" represents the specific capacity of the electrode in mAh units and "25" represents 25 hours), and the electrode with porous particles was lithified with a cutoff voltage of 10 mV. When the cutoff was reached, a constant voltage of 10 mV was applied. The cutoff current was C / 100. The cell was then left to rest for 10 minutes in the lithified state. Next, the electrode was delithiated with a cutoff voltage of 1 V and a constant current of C / 25, and then the cell was left to rest for 10 minutes. Next, the cell was subjected to a second lithiation with a constant current of C / 25 and a cutoff voltage of 10 mV. Next, a constant voltage of 10 mV was applied with a cutoff current of C / 100, and the cell was left to rest for 5 minutes.

[0129] Figure 4 shows the effect of silicon carbide formation on cell characteristics. As mentioned above, the delithiation capacity measured decreased significantly in the 900°C heat-treated sample, suggesting that silicon carbide formation has an adverse effect on anode characteristics.

[0130] Figure 4 also shows the change in the thickness of the electrode coating (excluding the current collector) of the electrode prepared and evaluated using a half-cell as described above. In the lithium-ion half-cell, the anode was removed after lithiation, delithiation, and the second lithiation cycle, and the change in thickness in the charged state was measured as a percentage ex situ. In other words, the change in thickness was measured for the anode in the lithified state.

[0131] The anode incorporating particulate material subjected to heat treatment at 900°C showed the greatest increase in thickness, suggesting that a carbon coating process at the same temperature unfavorably affects the usefulness of the particulate material in the anode. Normally, the degree of electrode expansion is expected to have a positive correlation with the amount of active silicon. However, the opposite was observed in the electrode containing the 900°C sample. While we do not wish to be bound by theory, the fact that this electrode showed the highest degree of expansion among all samples suggests that the structural and chemical relationships within the particulate material deteriorated in a very poor direction, and particle expansion was no longer controlled. This excessive expansion is expected to lead to isolated particles and low cycle retention.

[0132] Each participant measured further electrode characteristic data for an anode incorporating one of the samples. The results of these tests are shown in Table 3 and Figure 4.

[0133] These data show that as the heat treatment temperature of the sample incorporated into the electrode increases, both the first lithiumization capacity and the first delithiation capacity decrease. Furthermore, the percentage of active silicon relative to the total particle mass decreased with increasing heat treatment temperature. The active silicon content of the composite material particles was calculated by dividing the initial delithiation capacity of the half-cell (per unit mAh of composite material particles) by the theoretical capacity of silicon (3579 mAh / g), and the result was expressed as a percentage. The loss in the first cycle increased with increasing heat treatment temperature, and was particularly large for samples treated at 900°C. Anode thickness increased in all samples after 1.5 cycles. However, while the increase in thickness was nearly constant for the reference sample, 600°C treated sample, and 700°C sample, the electrode thickness increased significantly for the 800°C and 900°C treated samples. For batteries, it is desirable to maintain the electrode thickness as constant as possible.

[0134] Overall, the anode volumetric capacity was nearly identical for samples treated at 600°C and the reference sample. It decreased slightly for samples treated at 700°C, and significantly for samples treated at 800°C and 900°C.

[0135] These tests were conducted in half-cells containing silicon-carbon composite precursor particles without carbon coating. However, these results are expected to be reproducible even with carbon coating, suggesting that high-temperature carbon coating processes adversely affect the properties of carbon-coated particulate silicon-carbon composite products.

[0136] [Table 3-1] (Example 6 - Uncoated sample) Evaluation Procedure Silicon-carbon composite material particles were prepared using 125 g of carbon C1 and the method of Example 2. The heat treatment test procedure of Example 4 was repeated, except that the jet milling step prior to the heat treatment step was omitted and the heat treatment step was performed in a nitrogen atmosphere instead of an argon atmosphere.

[0137] (result) XRD was used to analyze the heat-treated samples and the reference sample. The results are shown in Figure 6. The heat-treated temperature for each sample is shown to the right of the XRD plot, with the XRD trace for the 600°C sample shown in the foreground and the XRD trace for the 900°C sample shown in the background.

[0138] A significant effect observed to be temperature-dependent was compound formation. In particular, non-electroactive compounds such as Si3N4 and SiC formed in samples treated at 800°C and 900°C. This is an undesirable result because it reduces the overall capacity of the material, thereby decreasing its value as an anode material. Furthermore, SiC is even more undesirable because it has poor electrical conductivity, and the presence of SiC in the final product can interfere with the lithiumization of silicon within the granular material.

[0139] A significant advantage is that silicon nitride formation does not occur after heat treatment at temperatures below 700°C. This is because it demonstrates that the method of the present invention can be carried out in a nitrogen atmosphere instead of an argon atmosphere.

[0140] Similarly, silicon crystallization was observed in the samples at 800°C and 900°C, which is undesirable. In other words, the preferred form of silicon for these materials is amorphous silicon.

[0141] In the 700°C sample, a mixture of amorphous and crystalline silicon was observed from the XRD data. At this temperature, a small peak of crystalline silicon overlaps with a broader amorphous peak. Furthermore, if silicon crystallization occurs, this is considered an indication of an increase in the average length scale of silicon domains within the particulate material resulting from the heat treatment.

[0142] The carbon coating deposition process in the present invention requires approximately the same amount of time as the samples were held at each temperature in these tests. By evaluating uncoated particles, the effect of temperature on the micro-internal structure of composite material particles can be observed more easily than when they are coated. A similar effect is expected when carbon deposition is performed at the same temperature.

[0143] Therefore, in the present invention, in which carbon film deposition is carried out at temperatures below 700°C, it is expected that the harmful effects observed at 800°C and 900°C in this experiment will be avoided or mitigated, thereby obtaining the advantages of conductive coatings and pore caps, while maintaining the significant microstructure previously developed by the inventors. At temperatures below 600°C, the material properties of the particles are even more suitable for use at the anode.

[0144] (Example 7: Carbon coating) A series of composite material particle samples were prepared using carbon skeletons C2 and C3 according to the method of Example 1. The precursor particles had the properties described in Table 3. The amount of coarse silicon was determined using the TGA method described in Example 3. All composite material particle samples contained less than 4 wt% coarse silicon.

[0145] [Table 3-2] The composite material particulate samples listed in Table 3 were carbon-coated by the following method: Mixed particles (60 g) were placed in a stainless steel tube (57 mm in diameter, 500 mm in length) filled (sealed) in the heating zone of a rotary furnace. The reactor space was purged with 0.2 L / min of nitrogen for 30 minutes. The furnace temperature was raised to the temperatures listed in Table 4 in the presence of a nitrogen stream. The excess amount of styrene was placed in a dresser bottle and heated to a maximum of 75°C in a water bath. After stabilizing the furnace temperature for 10 minutes, styrene was introduced into the reactor tube for a maximum of 90 minutes by bubbling 2 L / min of nitrogen into the dresser bottle (as shown in Table 4). Next, the reactor was purged with nitrogen and cooled to ambient temperature under nitrogen to obtain the carbon-coated material.

[0146] The elemental composition and coarse silicon content of the carbon-coated particles from Example 7 were analyzed using the TGA method described in Example 3. The results are shown in Table 4 and Figure 7. S1 (58m) 2 / g) and S10 (22m 2 Except for / g), in all carbon-coated particles, 6 to 12m2 The BET surface area in the range of / g was obtained.

[0147] [Table 4] *Comparative Example The data in Table 4 shows that when carbon coating is performed at temperatures below 700°C, the relative increase in coarse silicon is less than 190% in all cases. However, above 700°C, the amount of coarse silicon increases significantly. This suggests that particles coated at temperatures above 700°C undergo heat treatment of the fine micropore structure and the nanoscale silicon domains within the pore structure, resulting in the formation of large silicon domains. Therefore, this supports the hypothesis in Example 4 that the changes in silicon domains observed during heating of uncoated particles are also observed during the carbon coating process.

[0148] (Example 8 - Electrochemical evaluation of coated particles) Using the Si-C composite materials shown in Table 4, a negative electrode coating (anode) was prepared and tested in a full coin cell. To prepare the electrode, a carbon black dispersion was mixed with a CMC binder in a Thinky™ mixer. The Si-C composite material was added to the mixture and mixed in the Thinky™ mixer for 30 minutes. Next, an SBR binder was added to achieve a CMC:SBR ratio of 1:1 to form a slurry with a weight ratio of Si-C composite material:CMC / SBR:carbon black 70%:16%:14%. The slurry was mixed further in the Thinky™ mixer for another 30 minutes, then coated onto a 10 μm thick copper substrate (current collector) and dried at 50°C for 10 minutes. It was then dried further at 110°C for 12 hours, resulting in a coating density of 0.7 ± 0.5 g / cm³. 3 The negative electrode was formed.

[0149] A full coin cell was fabricated using a 0.8 cm radius annular anode cut from the negative electrode, with a porous polyethylene separator and a cobalt nickelmanganate (NMC532) positive electrode. The positive and negative electrodes were designed to form a balanced pair such that the capacity ratio of the positive electrode to the negative electrode was 0.9. Next, an electrolyte containing 1 M LiPF6 was added to the cell before sealing, in a solution of fluoroethylene carbonate, ethylene carbonate, and ethyl methyl carbonate containing 3 wt% vinylene carbonate.

[0150] The coin cell was cycled as follows: A constant current of C / 25 was applied to lithiumize the anode. The cutoff voltage was 4.3V. Once the cutoff 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 stand 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 stand for 10 minutes. After this first cycle, a constant current of C / 2 was applied to lithiumize the anode at a cutoff voltage of 4.3V, and then a constant voltage of 4.3V was applied with a cutoff current of C / 40 after a 5-minute standing period. The anode was then delithiated with a constant current of C / 2 at a cutoff of 2.75V. This was then repeated for the desired number of cycles. Capacitance retention at 100 cycles (CR100) and 200 cycles (CR200) ​​was calculated. This, along with the first lithium capacity, the first delithiation capacity, and the first cycle loss (FCL), is shown in Table 5.

[0151] The charge (lithiation) and discharge (delithiation) 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 in the second cycle. The first cycle loss (FCL) is (1 - (first delithiation capacity / first lithium capacity)) × 100%. The values ​​in Table 5 are averaged across three coin cells for each material.

[0152] As shown in Example 5, the active silicon level is determined from the half-cell experiment.

[0153] The data in Table 5 shows that the increase in coarse silicon weight% with increasing carbon coating temperature is reflected in the degradation of electrochemical properties. As the level of coarse silicon increases, the amount of active silicon in the material (determined from the half-cell) decreases, reducing the initial lithiation and delithiation capacity of the material and decreasing the normalized capacity retention over multiple charge-discharge cycles. Figures 8 and 9 show the normalized capacity retention of these materials.

[0154] [Table 5] *Comparative Example **To facilitate comparison between samples with different initial capacities, the volume retention values ​​in Table 5 have been normalized to 45 wt% active silicon by multiplying the volume retention percentage by the active Si value and dividing by 45.**

Claims

1. A method for preparing core-shell composite material particles, (a) Below: i. A porous carbon skeleton having micropores and / or mesopores, wherein the total pore volume of the micropores and mesopores is at least 0.4 cm³. 3 / g, and the PD of the porous carbon skeleton 50 The pore diameter is 10 nm or less, and the total pore volume of the micropores and mesopores, and the PD of the porous carbon skeleton are... 50 Pore ​​diameter is relative pressure p / p 0 10 -6 The porous carbon skeleton, as determined by the nitrogen gas adsorption method at 77K up to, and ii A plurality of nanoscale electroactive material domains arranged within the porous carbon skeleton, wherein the electroactive material is silicon, The steps include providing multiple precursor composite material particles, (b) A step of heat-treating the plurality of precursor composite material particles by contacting them with a pyrolytic carbon precursor, wherein the outer shell of the pyrolytic conductive carbon material is formed on the precursor composite material particles, and the heat treatment is performed at a temperature of 700°C or lower. It has, Step (a) of providing the plurality of precursor composite material particles includes contacting a plurality of porous carbon particles with a silicon precursor gas at a temperature between 200°C and 550°C, thereby forming a silicon film on the pores of the carbon particles. The method further comprises step (a) bringing the surface of the deposited silicon into contact with a passivation agent, wherein the silicon is not exposed to oxygen prior to contact with the passivation agent.

2. The method according to claim 1, wherein the heat treatment is carried out at 680°C or lower, 660°C or lower, 650°C or lower, 640°C or lower, 620°C or lower, or 600°C or lower.

3. The method according to claim 1 or 2, wherein the heat treatment is carried out at at least 500°C, at least 520°C, at least 540°C, at least 560°C, or at least 580°C.

4. The method according to any one of claims 1 to 3, wherein the pyrolytic carbon precursor is brought into contact with the composite material particles as a vapor or liquid.

5. The method according to claim 4, wherein the pyrolysis carbon precursor that is contacted with the composite material particles as vapor or liquid is hydrocarbon vapor.

6. The method according to claim 5, wherein the hydrocarbon is selected from polycyclic hydrocarbons having 10 to 25 carbon atoms and any 1 to 3 heteroatoms.

7. The method according to claim 6, wherein the polycyclic hydrocarbon is selected from naphthalene, anthracene, tetracene, pentacene, fluorene, acenaphthene, phenanthrene, fluoranthrene, pyrene, chrysene, perylene, coronene, fluorenone, anthraquinone, anthrone, and alkyl-substituted derivatives thereof.

8. The method according to claim 5, wherein the hydrocarbon is selected from bicyclic monoterpenoids.

9. The method according to claim 8, wherein the bicyclic monoterpenoid is selected from camphor, borneol, eucalyptol, camphene, careen, sabinene, thujien, and pinene.

10. The hydrocarbon is selected from C2 to C10 hydrocarbons. The method according to claim 5, wherein the hydrocarbon is selected from alkanes, alkenes, alkynes, cycloalkanes, cycloalkenes, and arenes.

11. The method according to claim 10, wherein the hydrocarbon is selected from methane, ethylene, propylene, and acetylene.

12. The method according to any one of claims 4 to 11, wherein the pyrolytic carbon precursor vapor is contacted with a transition metal catalyst at a temperature of at least 500°C before contacting the composite material particles.

13. The method according to claim 12, wherein the transition metal catalyst comprises nickel, iron, cobalt, copper, and mixtures thereof.

14. The transition metal catalyst is in the form of a mesh, The method according to claim 12 or 13, wherein the mesh is placed in the flow path of the hydrocarbon vapor before it comes into contact with the composite material particles.

15. The method according to claim 12 or 13, wherein the transition metal catalyst is disposed on the surface of the composite material particles.

16. The method according to any one of claims 1 to 11, wherein gaseous nickel carbonyl is thermally decomposed before step (b) to form a nickel film on the surface of the composite material particles.

17. The method according to claim 16, wherein, after step (b), the carbon-coated particulate material is brought into contact with carbon monoxide gas to form gaseous nickel carbonyl, thereby removing nickel from the carbon-coated composite material particles.

18. Step (b) is, The steps include bringing the composite material particles into contact with a dispersion or solution of a thermally decomposed carbon precursor in a solvent, The steps include removing the solvent before the heat treatment and providing composite material particles coated with the pyrolysis carbon precursor, The method according to any one of claims 1 to 3, comprising:

19. The method according to claim 18, wherein the pyrolysis carbon precursor is a polymer or oligomer containing a carbon-containing skeleton.

20. The method according to claim 18 or 19, wherein the pyrolysis carbon precursor is polyvinylpyrrolidone (PVP), or a copolymer of vinylpyrrolidone and one or more other ethylenically unsaturated monomers.

21. The method according to any one of claims 1 to 20, wherein the outer shell of the pyrolytic conductive carbon material has a thickness of 10 nm or less, 5 nm or less, 4 nm or less, 2 nm or less, or 1 nm or less.

22. The total pore volume of micropores and mesopores measured by the gas adsorption method is at least 0.45 cm 3 / g, at least 0.5 cm 3 / g, at least 0.55 cm 3 / g, at least 0.6 cm 3 / g, at least 0.65 cm 3 / g, at least 0.7 cm 3 / g, at least 0.75 cm 3 / g, at least 0.8 cm 3 / g, at least 0.85 cm 3 / g, at least 0.9 cm 3 / g, at least 0.95 cm 3 / g, at least 1 cm 3 / g, at least 1.05 cm 3 / g, or at least 1.1 cm 3 / g, The method according to any one of claims 1 to 21.

23. The total pore volume of micropores and mesopores measured by gas adsorption is 2.2 cm³. 3 / g or less, 2cm 3 / g or less, 1.8cm 3 / g or less, 1.6cm 3 / g or less, 1.5cm 3 / g or less, 1.4cm 3 / g or less, 1.3cm 3 Less than 1.2 cm / g, or 1.2 cm 3 The method according to any one of claims 1 to 22, wherein the amount is less than or equal to / g.

24. The PD of the porous carbon skeleton 50 The method according to any one of claims 1 to 23, wherein the pore diameter is 8 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, 3 nm or less, 2.5 nm or less, 2 nm or less, 1.5 nm or less, or 1 nm or less.

25. The method according to any one of claims 1 to 24, wherein the step (a) of providing the plurality of precursor composite material particles comprises the step of contacting the plurality of porous carbon particles with a silicon precursor gas at a temperature of 200°C to 500°C, thereby forming a silicon film on the pores of the carbon particles.

26. The aforementioned silicon precursor gas is silane (SiH 4 ), disilane (Si 2 H 6 ), trisilane (Si 3 H 8 ) Tetrasilane (Si 4 H 10 The method according to any one of claims 1 to 25, wherein the method is selected from chlorosilane and methylchlorosilane, and preferably from silane.

27. The precursor composite material particles are at least 1 μm, at least 2 μm, at least 3 μm, at least 4 μm, or at least 5 μm in size. 50 The method according to any one of claims 1 to 26, having a particle diameter.

28. The precursor composite material particles are 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, 12 μm or less, or 10 μm or less. 50 The method according to any one of claims 1 to 27, having a particle diameter.

29. The method according to any one of claims 1 to 28, wherein the volume fill factor of the electroactive material in the porous carbon skeleton, based on the volume of the micropores and / or mesopores, is 85% or less, 75% or less, 65% or less, 55% or less, or 45% or less.

30. The method according to any one of claims 1 to 29, wherein the volume packing ratio of the electroactive material within the porous carbon skeleton, based on the volume of the micropores and / or mesopores, is at least 20% or at least 25%.

31. The method according to any one of claims 1 to 30, wherein the porous carbon skeleton comprises at least 80% by mass of carbon, at least 85% by mass of carbon, at least 90% by mass of carbon, or at least 95% by mass of carbon.

32. The method according to any one of claims 1 to 31, wherein the duration of the heat treatment in step (b) is 1 to 3 hours.

33. The passivator is given by the following formula: (i) R - CH = CH - R; (ii) R - C ≡ C - R; and (iii) O = CH - R; Selected from one or more compounds, Here, R represents H, or an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, preferably 2 to 10 carbon atoms, or The method according to any one of claims 1 to 32, wherein the two R groups in formula (i) form an unsubstituted or substituted hydrocarbyl ring structure containing 3 to 8 carbon atoms.

34. The method according to claim 33, wherein the passivating agent is selected from the group consisting of ethylene, propylene, 1-butene, butadiene, 1-pentene, 1,4-pentadiene, 1-hexene, 1-octene, styrene, divinylbenzene, acetylene, phenylacetylene, norbornene, norbornadiene, and bicyclo[2.2.2]octo-2-ene, or mixtures thereof.

35. The passivating agent is represented by the formula HX-R, Here, X represents O, S, NR, or PR. Each R independently represents H, or an unsubstituted or substituted aliphatic or aromatic hydrocarbyl group having 1 to 20 carbon atoms, preferably 2 to 10 carbon atoms, or The method according to any one of claims 1 to 32, wherein the two R groups in formula (i) form an unsubstituted or substituted hydrocarbyl ring structure comprising 3 to 8 carbon atoms.

36. The method according to any one of claims 1 to 35, wherein step (b) is carried out at the same temperature as step (a2) or at a higher temperature than step (a2).

37. Step (a2) is the method according to any one of claims 1 to 36, performed within the temperature range of step (a).

38. The method according to any one of claims 1 to 37, wherein step (a2) is carried out at a temperature in the range of 25°C to 500°C.

39. The method according to claim 38, wherein step (b) is carried out at a temperature in the range of 500°C to 700°C.

40. Step (b) comprises the step of forming a conductive pyrolysis carbon material by the CVI process, The method according to any one of claims 1 to 39, wherein the pyrolytic carbon precursor is the same as the passivator used in step (a2).

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