Manufacture of silicon-carbon composite materials

Abstract

Silicon-carbon composite materials and related methods are disclosed that overcome the challenge of providing amorphous nano-sized silicon entrained within porous carbon. Compared to other inferior materials and methods described in the prior art, the materials and methods disclosed herein are more preferably used in a variety of applications, including energy storage devices such as lithium ion batteries.

Description

Background Art Technical Field

[0001] Embodiments of the present invention generally relate to methods for manufacturing silicon-carbon composite materials having properties that overcome the challenge of providing amorphous nanosized silicon entrained within porous carbon. The silicon-carbon composite materials are produced via chemical infiltration chemical vapor infiltration to impregnate amorphous nanosized silicon into the pores of a porous support. Suitable porous supports include, but are not limited to, porous carbon supports, such as carbon having a pore volume including micropores (less than 2 nm), mesopores (2 to 50 nm), and / or macropores (greater than 50 nm). Suitable precursors for the carbon support include, but are not limited to, sugars and polyols, organic acids, phenolic compounds, crosslinking agents, and amine compounds. Suitable composite materials include, but are not limited to, silicon materials. Precursors for the silicon include, but are not limited to, silicon-containing gases, such as silane, higher-order silanes (e.g., disilane, trisilane, and / or tetrasilane) and / or chlorosilanes (e.g., monochlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane) and mixtures thereof. Silicon chemical vapor infiltration (CVI) into the pores of the porous support material is achieved by exposing the porous support to a silicon-containing gas (e.g., silane) at an elevated temperature. The porous carbon support can be particulate porous carbon.

[0002] The key achievements in this regard are to obtain silicon in the desired form and shape, i.e., amorphous nanosized silicon. In addition, another key achievement is to achieve impregnation of silicon into the pores of the porous carbon. Still another key achievement is to achieve a high utilization rate of the silicon-containing gas, i.e., to achieve conversion of a high proportion of the silicon introduced into the CVI reactor into silicon impregnated into the pores of the porous carbon in the form of amorphous nanosized silicon. Such manufacturing methods and the materials produced thereby, such as silicon-carbon composite materials, can be used as anode materials for energy storage devices (e.g., lithium-ion batteries).

[0003] Description of Related Art

[0004] CVI is a method in which a gaseous substrate reacts within a porous support material. This method can be used to produce composite materials, such as silicon-carbon composite materials, where a silicon-containing gas decomposes within a porous carbon support at an elevated temperature. Although this method can be used to manufacture various composite materials, particular attention is paid to silicon-carbon (Si-C) composite materials. Such Si-C composite materials have practical applications, such as as energy storage materials, e.g., as anode materials within lithium-ion batteries (LIBs). LIBs have the potential to replace devices currently used in many applications. For example, current lead-acid automotive batteries are not suitable for next-generation all-electric and hybrid electric vehicles due to the formation of irreversible, stable sulfates during discharge. Lithium-ion batteries are a viable alternative to current lead-based systems due to their capacity and other considerations.

[0005] For this reason, there has been a strong interest in developing new LIB anode materials, especially silicon, which has a weight capacity 10 times higher than conventional graphite. However, silicon exhibits large volume changes during cycling, leading to electrode degradation and solid electrolyte interphase (SEI) instability. The most common improvement method is to reduce the silicon particle size, such as D V,50 <150 nm, such as D V,50 <100 nm, such as D V,50 <50 nm, such as D V,50 <20 nm, such as D V,50 <10 nm, such as D V,50 <5 nm, such as D V,50 <2 nm, as discrete particles or within a matrix. To date, the techniques used to fabricate nanoscale silicon involve high-temperature reduction of silicon oxides, extensive particle refinement, multi-step toxic etching, and / or other costly methods. Similarly, common matrix methods involve expensive materials such as graphene or nanographite, and / or require complex processing and coating.

[0006] It is known from the scientific literature that non-graphitizable (hard) carbon is beneficial as a LIB anode material (Liu Y, Xue, JS, Zheng T, Dahn, JR. Carbon 1996, 34:193–200; Wu, YP, Fang, SB, Jiang, YY. 1998, 75:201–206; Buiel E, Dahn JR. Electrochim Acta 1999 45:121-130). The reason for this improved performance lies in the disordered nature of the graphene layers, which allows Li ions to be embedded on either side of the graphene plane, thus theoretically doubling the stoichiometric content of Li ions relative to crystalline graphite. In addition, in contrast to graphite where lithiation can only occur parallel to the stacked graphene planes, the disordered structure improves the rate capability of the material by allowing isotropic Li ion insertion. Despite these desirable electrochemical properties, amorphous carbon has not been widely adopted in commercial Li-ion batteries mainly due to its low FCE and low bulk density (<1 g / cc). Instead, amorphous carbon has been more commonly used as a low-mass additive and coating for other active material components of the battery to improve conductivity and reduce surface side reactions.

[0007] In recent years, amorphous carbon as a LIB battery material has received considerable attention as a coating for silicon anode materials. Such silicon-carbon core-shell structures have the potential not only to improve conductivity but also to buffer the expansion of silicon upon lithiation, thereby stabilizing its cycling stability and minimizing issues related to particle pulverization, insulation, and SEI integrity (Jung, Y, Lee K, Oh, S. Electrochim Acta 2007 52:7061–7067; Zuo P, Yin G, Ma Y.. Electrochim Acta 2007 52:4878–4883; Ng SH, Wang J, Wexler D, Chew SY, Liu HK. J Phys Chem C 2007 111:11131–11138). Issues associated with this strategy include the lack of suitable silicon starting materials for coating processes and the inherently lack of engineered void space within the carbon-coated silicon core-shell composite particles to accommodate the expansion of silicon during lithiation. This inevitably leads to cycling stability failure due to the disruption of the core-shell structure and the SEI layer (Beattie SD, Larcher D, Morcrette M, Simon B, Tarascon, J-M. J Electrochem Soc 2008 155:A158-A163).

[0008] An alternative to the core-shell structure is one in which amorphous nano-sized silicon is uniformly distributed within the pores of a porous carbon scaffold. Porous carbon has desirable properties: (i) carbon porosity provides void volume to accommodate the expansion of silicon during lithiation, thereby reducing the net composite particle expansion at the electrode level; (ii) the disordered graphene network provides increased conductivity to silicon, enabling faster charge / discharge rates, (iii) the nanoporous structure acts as a template for silicon synthesis, thereby prescribing its size, distribution, and morphology.

[0009] To this end, the desired inverse hierarchical structure can be achieved by employing CVI, in which a silicon-containing gas can fully penetrate the nanoporous carbon and decompose into nano-sized silicon within it. The CVI method has several advantages in terms of silicon structure. One advantage is that the nanoporous carbon provides nucleation sites for growing silicon while prescribing the maximum particle shape and size. Confining the growth of silicon within the nanoporous structure reduces the susceptibility to cracking or pulverization and contact loss due to expansion. Additionally, this structure promotes the nano-sized silicon to remain in the amorphous phase. This property provides high charge / discharge rates, especially when combined with the regions near silicon within the conductive carbon scaffold. The system provides a solid-state lithium diffusion path for high-rate capabilities of directly delivering lithium ions to the nano-scale silicon interface. Another benefit of providing silicon via CVI within the carbon scaffold is the suppression of unwanted crystalline Li 15Formation of the Si4 phase. Another advantage is that the CVI method provides void space within the particles.

[0010] To quantify the percentage loading of silicon in a silicon-carbon composite, thermogravimetric analysis (TGA) can be used. For this purpose, the silicon composite is heated from 25 °C to 1100 °C. Without being bound by theory, this specifies that all carbon is burned off and all silicon is oxidized to SiO2. Thus, the % of silicon constituting the silicon-carbon composite is calculated as

[0011] % Si = 100 x [[M1100 x (28 / (28+(16x2)))] / M°]

[0012] where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M° is the minimum mass of the silicon-carbon composite between 30 °C and 200 °C when the silicon-carbon composite is heated in air from approximately 25 °C to approximately 1100 °C, as determined by thermogravimetric analysis.

[0013] To measure the relative amount of silicon impregnated into the pores of the porous carbon, thermogravimetric analysis TGA can be used. TGA can be used to evaluate the fraction of silicon residing within the pores of the porous carbon relative to the total silicon present (i.e., the sum of the silicon within the pores and on the particle surface). When the silicon-carbon composite is heated in air, the sample shows a mass increase starting at approximately 300 °C to 500 °C, which reflects the beginning of the oxidation of silicon to SiO2; then the sample shows a mass loss due to the burning off of carbon; then the sample shows a mass increase, which reflects the continued conversion of silicon to SiO2, increasing to an asymptotic value near a temperature of 1100 °C when the oxidation of silicon is complete. For the purposes of this analysis, it is assumed that the minimum mass recorded when the sample is heated from 800 °C to 1100 °C represents the point at which the carbon is completely burned off. Any additional mass increase beyond this point corresponds to the oxidation of silicon to SiO2, and the total mass at the end of oxidation is SiO2. Thus, the percentage of unoxidized silicon after carbon burning, expressed as a proportion of the total silicon, can be determined using the following formula:

[0014] Z = 1.875 x [(M1100 - M) / M1100] x 100

[0015] where M1100 is the mass of the sample at the end of oxidation at a temperature of 1100 °C, and M is the minimum mass recorded when the sample is heated from 800 °C to 1100 °C.

[0016] Without being bound by theory, the temperature at which silicon is oxidized under TGA conditions is related to the length scale of the oxide coating on the silicon due to the diffusion of oxygen atoms through the oxide layer. Thus, silicon residing within the carbon pores will oxidize at a lower temperature than silicon deposits on the particle surface, as there must be a thinner coating on these surfaces. In this way, the calculation of Z is used to quantitatively evaluate the fraction of silicon not impregnated within the pores of the porous carbon scaffold. SUMMARY OF THE INVENTION

[0017] Silicon-carbon composites and related methods are disclosed that overcome the challenge of providing amorphous nanosized silicon entrained within porous carbon. Compared to other inferior materials and methods described in the prior art, the materials and methods disclosed herein are more preferably used in a variety of applications, including energy storage devices such as lithium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 . Relationship between Z and average coulombic efficiency for various silicon-carbon composites.

[0019] Figure 2 . Differential capacity versus voltage plot for the second cycle of silicon-carbon composite 3 using a half cell.

[0020] Figure 3 . Differential capacity versus voltage plots for the second to fifth cycles of silicon-carbon composite 3 using a half cell.

[0021] Figure 4 . dQ / dV versus V plots for various silicon-carbon composites.

[0022] Figure 5 . For silicon-carbon composite 3 Calculation example.

[0023] Figure 6 . Z for various silicon-carbon composites versus Figure.

[0024] Figure 7 . Y for various silicon-carbon composites CVI versus X Si Figure.

[0025] Figure 8 . Silane utilization (%) determined by Fourier transform infrared spectroscopy (FTIR) as a function of run time for the preparation of sample 21. DETAILED DESCRIPTION

[0026] In the following description, certain specific details are set forth in order to provide a thorough understanding of the various embodiments. However, those skilled in the art will understand that the present invention may be practiced without these details. In other instances, well-known structures have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. Unless the context otherwise requires, throughout the specification and the appended claims, the word "comprise" and its variations (e.g., "comprises" and "comprising") shall be interpreted in an open, inclusive sense, i.e., as "including, but not limited to". In addition, the headings provided herein are for convenience only and do not interpret the scope or meaning of the claimed invention.

[0027] As used throughout this specification, the phrase "in one embodiment" or "in an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" throughout the specification are not necessarily all referring to the same embodiment. Moreover, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Further, as used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its sense including "and / or" unless the context clearly dictates otherwise.

[0028] A. Porous scaffold material

[0029] For the purposes of the embodiments of the present invention, a porous scaffold into which silicon is to be impregnated may be used. Herein, the porous scaffold may comprise various materials. In some embodiments, the porous scaffold material mainly comprises carbon, such as hard carbon. Other allotropes of carbon are also contemplated in other embodiments, such as graphite, amorphous carbon, diamond, C60, carbon nanotubes (e.g., single-walled and / or multi-walled), graphene, and / or carbon fibers. The introduction of pores into the carbon material can be achieved in various ways. For example, the pores in the carbon material can be achieved by adjusting the polymer precursor and / or processing conditions to produce the porous carbon material, which is described in detail in the subsequent sections.

[0030] In other embodiments, the porous scaffold comprises a polymeric material. To this end, a variety of polymers are contemplated for use in various embodiments, including but not limited to inorganic polymers, organic polymers, and addition polymers. Examples of inorganic polymers herein include but are not limited to homo-chain polymers of silicon-silicon, such as polysilanes, silicon carbide, polygermanes, and polystannanes. Other examples of inorganic polymers include but are not limited to heterochain polymers, such as polyborazylene, polysiloxanes (such as polydimethylsiloxane (PDMS), polymethylhydrosiloxane (PMHS), and polydiphenylsiloxane), polysilazanes (such as perhydropolysilazane (PHPS)), polyphosphazenes, and poly(dichlorophosphazene), polyphosphoric (acid or salts), polythiazyl, and polysulfides. Examples of organic polymers include but are not limited to low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), nylon, nylon 6, nylon 6,6, Teflon (polytetrafluoroethylene), thermoplastic polyurethane (TPU), polyureas, poly(lactide), poly(glycolide), and combinations thereof, phenolic resins, polyamides, polyaramides, polyethylene terephthalate, polychloroprene, polyacrylonitrile, polyaniline, polyimides, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PDOT:PSS), and other materials known in the art. Organic polymers can be of synthetic or natural origin. In some embodiments, the polymer is a polysaccharide, such as starch, cellulose, cellobiose, amylose, amylopectin, gum arabic, lignin, etc. In some embodiments, the polysaccharide is derived from the charring of monosaccharides or oligosaccharides (such as fructose, glucose, sucrose, maltose, raffinose, etc.).

[0031] In certain embodiments, the porous scaffold polymeric material comprises a coordination polymer. Coordination polymers herein include but are not limited to metal-organic frameworks (MOFs). Techniques for producing MOFs and exemplary materials of MOFs are known and described in the art (“The Chemistry and Applications of Metal-Organic Frameworks, Hiroyasu Furukawa et al., Science 341, (2013); DOI: 10.1126 / science.1230444). Examples of MOFs herein include but are not limited to Basolite TM materials and zeolitic imidazolate frameworks (ZIFs).

[0032] With a variety of polymers envisioned as having the potential to provide porous substrates, various processing routes are envisioned in various embodiments to achieve the porosity. In this context, as is known in the art, the general methods for creating porosity within various materials are numerous and include, but are of course not limited to, the following methods: including emulsification, micelle generation, gasification, dissolution followed by removal of the solvent (e.g., freeze-drying), axial compaction and sintering, gravity sintering, powder rolling and sintering, isostatic compaction and sintering, metal spraying, metal coating and sintering, metal injection molding and sintering, etc. Other routes for producing porous polymer materials are also envisioned, including the production of porous gels, such as freeze-dried gels, aerogels, etc.

[0033] In certain embodiments, the porous scaffold material includes a porous ceramic material. In certain embodiments, the porous scaffold material includes a porous ceramic foam. In this context, as is known in the art, the general methods for creating porosity within ceramic materials are diverse and include, but are of course not limited to, creating porosity. In this context, the general methods and materials suitable for forming porous ceramics include, but are not limited to, porous alumina, zirconia-toughened porous alumina, porous partially stabilized zirconia, porous alumina, porous sintered silicon carbide, sintered silicon nitride, porous cordierite, porous zirconia, clay-bonded silicon carbide, etc.

[0034] In certain embodiments, the porous scaffold includes porous silica or other oxygen-containing silicon materials. The production of silica gels (including sol-gels) and other porous silicas is known in the art.

[0035] In certain embodiments, the porous material includes porous metal. In this regard, suitable metals include, but are not limited to, porous aluminum, porous steel, porous nickel, porous Inconcel, porous Hasteloy, porous titanium, porous copper, porous brass, porous gold, porous silver, porous germanium, and other metals capable of forming porous structures, as is known in the art. In certain embodiments, the porous scaffold material includes a porous metal foam. The types of metals and their manufacturing methods are known in the art. Such methods include, but are not limited to, casting (including foaming, infiltration, and low-foam casting), deposition (chemical and physical), gas eutectic formation, and powder metallurgy techniques (e.g., powder sintering, compaction in the presence of a foaming agent, and fiber metallurgy techniques).

[0036] B. Porous Carbon Scaffold

[0037] Methods for preparing porous carbon materials from polymer precursors are known in the art. For example, methods for preparing carbon materials are described in U.S. Pat. Nos. 7,723,262, 8,293,818, 8,404,384, 8,654,507, 8,916,296, 9,269,502, 10,590,277 and U.S. Patent Application 16 / 745,197, the entire disclosures of which are incorporated herein by reference in their entirety for all purposes.

[0038] Thus, in one embodiment, the present disclosure provides a method for preparing any of the above carbon materials or polymer gels. The carbon material can be synthesized by pyrolysis of a single precursor, such as a saccharide material, such as sucrose, fructose, glucose, dextrin, maltodextrin, starch, amylopectin, amylose, lignin, gum arabic and other saccharides known in the art, and combinations thereof. Alternatively, the carbon material can be synthesized by pyrolysis of a composite resin, such as using a polymer precursor (such as phenol, resorcinol, bisphenol A, urea, melamine and other suitable compounds known in the art, and combinations thereof) with a crosslinking agent (such as formaldehyde, hexamethylenetetramine, furfural and other crosslinking agents known in the art, and combinations thereof) in a suitable solvent (such as water, ethanol, methanol and other solvents known in the art, and combinations thereof) using a sol-gel method. The resin can be acidic or basic and can contain a catalyst. The catalyst can be volatile or non-volatile. The pyrolysis temperature and residence time can vary as known in the art.

[0039] In some embodiments, the method includes a sol-gel method, a condensation method or a crosslinking method involving a monomer precursor and a crosslinking agent, two existing polymers and a crosslinking agent, or a single polymer and a crosslinking agent to prepare a polymer gel, followed by pyrolysis of the polymer gel. The polymer gel can be dried (e.g., freeze-dried) before pyrolysis; however, drying is not necessarily required.

[0040] The target carbon properties can be derived from various polymer chemistries, as long as the polymerization reaction produces a resin / polymer with the desired carbon backbone. Different polymer families include linear phenolic resins, resolvable phenolic resins, acrylates, styrenics, urethanes, rubbers (such as chloroprene, styrene-butadiene, etc.), nylons, etc. Any of these polymer resins can be prepared via many different methods, including sol-gel, emulsion / suspension, solid state, melt state, etc. for the polymerization and crosslinking processes.

[0041] In some embodiments, an electrochemically active modifier is incorporated into a material that is a polymer. For example, an organic or carbon-containing polymer, such as RF, is copolymerized with a polymer containing an electrochemically active modifier. In one embodiment, the polymer containing the electrochemically active modifier contains silicon. In one embodiment, the polymer is tetraethyl orthosilicate (TEOS). In one embodiment, a TEOS solution is added to the RF solution before or during polymerization. In another embodiment, the polymer is a polysilane having organic side groups. In some cases, these side groups are methyl groups, in other cases, these groups are phenyl groups, and in other cases, the side chains include phenyl, pyrrolidone, acetate, vinyl, siloxane segments. In some cases, the side chains include Group 14 elements (silicon, germanium, tin, or lead). In other cases, the side chains include Group 13 elements (boron, aluminum, boron, gallium, indium). In other cases, the side chains include Group 15 elements (nitrogen, phosphorus, arsenic). In other cases, the side chains include Group 16 elements (oxygen, sulfur, selenium).

[0042] In another embodiment, the electrochemically active modifier includes silole. In some cases, it is phenol-silole or silafluorene. In other cases, it is polysilole or polysilafluorene. In some cases, silicon is replaced with germanium (germole or germafluorene), tin (stannole or stannafluorene), nitrogen (carbazole), or phosphorus (phosphole or phosphafluorene). In all cases, the heteroatom-containing material can be a small molecule, oligomer, or polymer. The phosphorus atom can also be bonded to oxygen or can be non-bonded to oxygen.

[0043] In some embodiments, the reactant contains phosphorus. In some other embodiments, the phosphorus is in the form of phosphoric acid. In some other embodiments, the phosphorus can be in the form of a salt, where the anion of the salt contains one or more phosphate, phosphite, phosphide, hydrogen phosphate, dihydrogen phosphate, hexafluorophosphate, hypophosphite, polyphosphate, or pyrophosphate ions, or a combination thereof. In some other embodiments, the phosphorus can be in the form of a salt, where the cation of the salt contains one or more phosphonium ions. Any of the non-phosphate anions or cations pairs in the above embodiments can be selected for those known and described in the art. In this case, exemplary cations paired with phosphate-containing anions include, but are not limited to, ammonium ions, tetraethylammonium ions, and tetramethylammonium ions. In this case, exemplary anions paired with phosphate-containing cations include, but are not limited to, carbonate ions, bicarbonate ions, and acetate ions.

[0044] In some embodiments, the catalyst includes a basic volatile catalyst. For example, in one embodiment, the basic volatile catalyst includes ammonium carbonate, ammonium bicarbonate, ammonium acetate, ammonium hydroxide, or a combination thereof. In other embodiments, the basic volatile catalyst is ammonium carbonate. In another other embodiment, the basic volatile catalyst is ammonium acetate.

[0045] In other embodiments, the method includes mixing the acids. In certain embodiments, the acid is a solid at room temperature and pressure. In some embodiments, the acid is a liquid at room temperature and pressure. In some embodiments, the acid is a liquid at room temperature and a pressure that does not provide for the dissolution of one or more other polymer precursors.

[0046] The acid can be selected from a number of acids suitable for use in the polymerization process. For example, in some embodiments, the acid is acetic acid, and in other embodiments, the acid is oxalic acid. In other embodiments, the acid is mixed with a first solvent or a second solvent in an acid-to-solvent ratio of 99:1, 90:10, 75:25, 50:50, 25:75, 20:80, 10:90, or 1:90. In other embodiments, the acid is acetic acid and the first solvent or the second solvent is water. In other embodiments, the acidity is provided by adding a solid acid.

[0047] The total content of the acid in the mixture can vary to alter the properties of the end product. In some embodiments, the acid is present in the mixture at about 1% to about 50% by weight. In other embodiments, the acid is present at about 5% to about 25%. In other embodiments, the acid is present at about 10% to about 20%, such as about 10%, about 15%, or about 20%.

[0048] In certain embodiments, the polymer precursor components are blended together and then maintained at a time and temperature sufficient to effect polymerization. One or more of the polymer precursor components can have a particle size less than about 20 mm, such as less than 10 mm, such as less than 7 mm, such as less than 5 mm, such as less than 2 mm, such as less than 1 mm, such as less than 100 microns, such as less than 10 microns. In some embodiments, during the blending process, the particle size of one or more of the polymer precursor components is reduced.

[0049] Blending of one or more polymer precursor components without a solvent can be achieved by methods described in the art and while controlling process conditions (e.g., temperature), such methods in the art as ball milling, jet milling, Fritsch milling, planetary mixing, and other mixing methods for mixing or blending solid particles. The mixing or blending process can be achieved before, during, and / or after incubation at the reaction temperature (or a combination thereof).

[0050] The reaction parameters include aging the blended mixture at a temperature and for a time sufficient to cause one or more polymer precursors to react with each other and form a polymer. In this regard, suitable aging temperatures are from about room temperature to a temperature at or near the melting point of one or more polymer precursors. In some embodiments, suitable aging temperatures are from about room temperature to a temperature at or near the glass transition temperature of one or more polymer precursors. For example, in some embodiments, the solvent-free mixture is aged at a temperature from about 20°C to about 600°C, such as from about 20°C to about 500°C, such as from about 20°C to about 400°C, such as from about 20°C to about 300°C, such as from about 20°C to about 200°C. In certain embodiments, the solvent-free mixture is aged at a temperature from about 50°C to about 250°C.

[0051] The reaction duration is typically sufficient to cause the polymer precursors to react and form a polymer. For example, the mixture can be aged for any time from 1 hour to 48 hours, more or less depending on the desired result. Typical embodiments include aging for a period of about 2 hours to about 48 hours. For example, in some embodiments, aging is for about 12 hours, and in other embodiments, aging is for about 4 - 8 hours (e.g., about 6 hours).

[0052] In certain embodiments, an electrochemically modifying agent is incorporated during the polymerization process described above. For example, in some embodiments, an electrochemically modifying agent in the form of metal particles, metal slurries, metal salts, metal oxides, or molten metal can be dissolved or suspended in the mixture that produces the gel resin.

[0053] Exemplary electrochemically modifying agents for producing composite materials can fall into one or more chemical classes. In some embodiments, the electrochemically modifying agent is a lithium salt, such as but not limited to lithium fluoride, lithium chloride, lithium carbonate, lithium hydroxide, lithium benzoate, lithium bromide, lithium formate, lithium hexafluorophosphate, lithium iodate, lithium iodide, lithium perchlorate, lithium phosphate, lithium sulfate, lithium tetraborate, lithium tetrafluoroborate, and combinations thereof.

[0054] In certain embodiments, the electrochemically modifying agent includes a metal, and exemplary substances include but are not limited to aluminum isopropoxide, manganese acetate, nickel acetate, iron acetate, tin chloride, silicon chloride, and combinations thereof. In certain embodiments, the electrochemically modifying agent is a phosphoric (acid) compound, including but not limited to phytic acid, phosphoric acid, ammonium dihydrogen phosphate, and combinations thereof. In certain embodiments, the electrochemically modifying agent includes silicon, and exemplary substances include but are not limited to silicon powder, silicon nanotubes, polysilicon, nanocrystalline silicon, amorphous silicon, porous silicon, nanosized silicon, silicon with nanoscale features, silicon with nanosize and nanoscale features, silicyne, and black silicon, and combinations thereof.

[0055] Electrochemical modifiers can be combined with various polymer systems through physical mixing or chemical reactions with latent (or secondary) polymer functional groups. Examples of latent polymer functional groups include, but are not limited to, epoxy groups, unsaturated groups (double and triple bonds), acid groups, alcohol groups, amine groups, and basic groups. Crosslinking with latent functional groups can occur via heteroatoms (e.g., vulcanization with sulfur, acid / base / ring-opening reactions with phosphoric acid), reactions with organic acids or bases (as described above), coordination with transition metals (including, but not limited to, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ag, Au), ring-opening or ring-closing reactions (rotaxanes, spiro compounds, etc.).

[0056] Electrochemical modifiers can also be added to polymer systems by physical blending. Physical blending can include, but is not limited to, melt blending of polymers and / or copolymers, addition of discrete particles, chemical vapor deposition of the electrochemical modifier, and co-precipitation of the electrochemical modifier and the primary polymer material.

[0057] In some cases, the electrochemical modifier can be added via a metal salt solid, solution, or suspension. The metal salt solid, solution, or suspension can contain acids and / or alcohols to improve the solubility of the metal salt. In another variant, the polymer gel (before or after an optional drying step) is contacted with a slurry containing the electrochemical modifier. In another variant, the polymer gel (before or after an optional drying step) is contacted with a metal or metal oxide sol containing the desired electrochemical modifier.

[0058] In addition to the electrochemical modifiers exemplified above, the composite material can contain one or more other forms (i.e., allotropes) of carbon. In this regard, it has been found that including different allotropes of carbon (e.g., graphite, amorphous carbon, conductive carbon, carbon black, diamond, C60, carbon nanotubes (e.g., single-walled and / or multi-walled), graphene, and / or carbon fibers) in the composite material is effective for optimizing the electrochemical properties of the composite material. The various allotropes of carbon can be incorporated into the carbon material at any stage of the preparation methods described herein. For example, during the solution stage, during the gelation stage, during the curing stage, during the pyrolysis stage, during the grinding stage, or after grinding. In some embodiments, a second carbon form is incorporated into the composite material by adding the second carbon form before or during the polymerization of the polymer gel as described in more detail herein. The polymer gel containing the second carbon form is then processed according to the general techniques described herein to obtain a carbon material containing the second allotrope of carbon.

[0059] In a preferred embodiment, carbon is produced from a precursor having little or no solvent required for processing (solvent-free). The structure of the polymer precursor suitable for a low-solvent or substantially solvent-free reaction mixture is not particularly limited as long as the polymer precursor is capable of reacting with another polymer precursor or with a second polymer precursor to form a polymer. Polymer precursors include amine-containing compounds, alcohol-containing compounds, and carbonyl-containing compounds. For example, in some embodiments, the polymer precursor is selected from alcohols, phenols, polyols, sugars, alkylamines, aromatic amines, aldehydes, ketones, carboxylic acids, esters, ureas, acyl halides, and isocyanates.

[0060] In one embodiment employing a low-solvent or substantially solvent-free reaction mixture, the method includes using a first polymer precursor and a second polymer precursor. And in some embodiments, the first polymer precursor or the second polymer precursor is a carbonyl-containing compound and the remaining first polymer precursor or second polymer precursor is an alcohol-containing compound. In some embodiments, the first polymer precursor is a phenolic compound and the second polymer precursor is an aldehyde compound (e.g., formaldehyde). In one embodiment of the method, the phenolic compound is phenol, resorcinol, catechol, hydroquinone, phloroglucinol, or a combination thereof; and the aldehyde compound is formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, benzaldehyde, cinnamaldehyde, or a combination thereof. In other embodiments, the phenolic compound is resorcinol, phenol, or a combination thereof, and the aldehyde compound is formaldehyde. In other embodiments, the phenolic compound is resorcinol and the aldehyde compound is formaldehyde. In some embodiments, the polymer precursors are an alcohol and a carbonyl compound (e.g., resorcinol and acetaldehyde), and they are present in a ratio of about 0.5:1.0, respectively.

[0061] Polymer precursor materials suitable for low-solvent or substantially solvent-free reaction mixtures as disclosed herein include (a) alcohol compounds, phenolic compounds, and other mono- or polyhydroxy compounds, and (b) aldehydes, ketones, and combinations thereof. As used herein, representative alcohols include straight-chain and branched-chain, saturated and unsaturated alcohols. Suitable phenolic compounds include polyhydroxybenzenes, such as dihydroxybenzenes or trihydroxybenzenes. Representative polyhydroxybenzenes include resorcinol (i.e., 1,3-dihydroxybenzene), catechol, hydroquinone, and phloroglucinol. In this regard, other suitable compounds are bisphenols, such as bisphenol A. Mixtures of two or more polyhydroxybenzenes may also be used. Phenol (monohydroxybenzene) may also be used. Representative polyhydroxy compounds include sugars, such as glucose, sucrose, fructose, chitin, and other polyols, such as mannitol. As used herein, aldehydes include: straight-chain saturated aldehydes, such as methanal / formaldehyde, ethanal / acetaldehyde, propanal / propionaldehyde, butanal / butyraldehyde, etc.; straight-chain unsaturated aldehydes, such as ketene and other ketones, propenal / acrylaldehyde, 2-butenal (crotonaldehyde), 3-butenal, etc.; branched-chain saturated and unsaturated aldehydes; and aldehydes of the aromatic type, such as benzaldehyde, salicylaldehyde, hydrocinnamaldehyde, etc. Suitable ketones include: straight-chain saturated ketones, such as acetone and 2-butanone, etc.; straight-chain unsaturated ketones, such as propenone, 2-butenone, and 3-butenone (methyl vinyl ketone), etc.; branched-chain saturated and unsaturated ketones; and ketones of the aromatic type, such as methyl benzyl ketone (phenylacetone), ethyl benzyl ketone, etc. The polymer precursor material may also be a combination of the above-described precursors.

[0062] In some embodiments, one polymer precursor in the low-solvent or substantially solvent-free reaction mixture is an alcohol-containing material, and the other polymer precursor is a carbonyl-containing material. The relative amounts of the alcohol-containing material (e.g., an alcohol, a phenolic compound, and a mono- or polyhydroxy compound or a combination thereof) reacting with the carbonyl-containing material (e.g., an aldehyde, a ketone, or a combination thereof) can vary significantly. In some embodiments, the ratio of the alcohol-containing material to the aldehyde material is selected such that the total number of moles of reactive alcohol groups in the alcohol-containing material is approximately the same as the total number of moles of reactive carbonyl groups in the aldehyde material. Similarly, the ratio of the alcohol-containing material to the ketone material can be selected such that the total number of moles of reactive alcohol groups in the alcohol-containing material is approximately the same as the total number of moles of reactive carbonyl groups in the ketone material. When the carbonyl-containing material comprises a combination of an aldehyde material and a ketone material, the same approximate 1:1 molar ratio applies.

[0063] In other embodiments, the polymer precursor in a low-solvent or substantially solvent-free reaction mixture is a urea- or amine-containing compound. For example, in some embodiments, the polymer precursor is urea, melamine, hexamethylenetetramine (HMT), or a combination thereof. Other embodiments include polymer precursors selected from isocyanates or other reactive carbonyl compounds (such as acyl halides, etc.).

[0064] Some embodiments of the disclosed methods include preparing a low-solvent or solvent-free polymer gel (and carbon material) comprising an electrochemical modifier. Such electrochemical modifiers include, but are not limited to, nitrogen, silicon, and sulfur. In other embodiments, the electrochemical modifier includes fluorine, iron, tin, silicon, nickel, aluminum, zinc, or manganese. The electrochemical modifier can be included in any step of the preparation process. For example, in some cases, the electrochemical modifier is mixed with the mixture, polymer phase, or continuous phase.

[0065] Blending one or more polymer precursor components without solvent can be achieved by methods described in the art and while controlling process conditions (such as temperature), such as ball milling, jet milling, Fritsch milling, planetary mixing, and other mixing methods for mixing or blending solid particles. The mixing or blending process can be achieved before, during, and / or after (or a combination thereof) incubation at the reaction temperature.

[0066] The reaction parameters include aging the blended mixture at a temperature and for a time sufficient for one or more polymer precursors to react with each other and form a polymer. In this regard, a suitable aging temperature is from about room temperature to a temperature equal to or close to the melting point of one or more polymer precursors. In some embodiments, a suitable aging temperature is from about room temperature to a temperature equal to or close to the glass transition temperature of one or more polymer precursors. For example, in some embodiments, the solvent-free mixture is aged at a temperature of about 20°C to about 600°C, such as about 20°C to about 500°C, such as about 20°C to about 400°C, such as about 20°C to about 300°C, such as about 20°C to about 200°C. In certain embodiments, the solvent-free mixture is aged at a temperature of about 50°C to about 250°C.

[0067] A porous carbon material can be achieved via pyrolysis of a polymer generated from a precursor material as described above. In some embodiments, the porous carbon material includes amorphous activated carbon, which is produced by pyrolysis, physical or chemical activation, or a combination thereof in a single process step or sequential process steps.

[0068] The temperature and residence time of pyrolysis can vary. For example, the residence time can vary from 1 min to 10 min, 10 min to 30 min, 30 min to 1 hour, 1 hour to 2 hours, 2 hours to 4 hours, 4 hours to 24 hours. The temperature can vary. For example, the pyrolysis temperature can vary from 200 °C to 300 °C, 250 to 350 °C, 350 °C to 450 °C, 450 °C to 550 °C, 540 °C to 650 °C, 650 °C to 750 °C, 750 °C to 850 °C, 850 °C to 950 °C, 950 °C to 1050 °C, 1050 °C to 1150 °C, 1150 °C to 1250 °C. Pyrolysis can be carried out in an inert gas (such as nitrogen or argon).

[0069] In some embodiments, alternative gases are used to further achieve carbon activation. In certain embodiments, pyrolysis and activation are combined. Suitable gases for achieving carbon activation include but are not limited to carbon dioxide, carbon monoxide, water (steam), air, oxygen, and other combinations thereof. The temperature and residence time of activation can vary. For example, the residence time can vary from 1 min to 10 min, 10 min to 30 min, 30 min to 1 hour, 1 hour to 2 hours, 2 hours to 4 hours, 4 hours to 24 hours. The temperature can vary. For example, the pyrolysis temperature can vary from 200 °C to 300 °C, 250 to 350 °C, 350 °C to 450 °C, 450 °C to 550 °C, 540 °C to 650 °C, 650 °C to 750 °C, 750 °C to 850 °C, 850 °C to 950 °C, 950 °C to 1050 °C, 1050 °C to 1150 °C, 1150 °C to 1250 °C.

[0070] Before pyrolysis, and / or after pyrolysis, and / or after activation, the carbon can be size-reduced. Size reduction can be achieved by various techniques known in the art, such as jet milling in the presence of various gases, including air, nitrogen, argon, helium, supercritical vapor, and other gases known in the art. Other size reduction methods are also contemplated, such as grinding, ball milling, jet milling, water jet milling, and other methods known in the art.

[0071] The porous carbon scaffold can be in the form of particles. The particle size and particle size distribution can be measured by various techniques known in the art and can be described based on fractional volume. In this regard, the Dv,50 of the carbon scaffold can be from 10 nm to 10 mm, such as from 100 nm to 1 mm, such as from 1 μm to 100 μm, such as from 2 μm to 50 μm, such as from 3 μm to 30 μm, such as from 4 μm to 20 μm, such as from 5 μm to 10 μm. In certain embodiments, the Dv,50 is less than 1 mm, such as less than 100 μm, such as less than 50 μm, such as less than 30 μm, such as less than 20 μm, such as less than 10 μm, such as less than 8 μm, such as less than 5 μm, such as less than 3 μm, such as less than 1 μm. In certain embodiments, the Dv,100 is less than 1 mm, such as less than 100 μm, such as less than 50 μm, such as less than 30 μm, such as less than 20 μm, such as less than 10 μm, such as less than 8 μm, such as less than 5 μm, such as less than 3 μm, such as less than 1 μm. In certain embodiments, the Dv,99 is less than 1 mm, such as less than 100 μm, such as less than 50 μm, such as less than 30 μm, such as less than 20 μm, such as less than 10 μm, such as less than 8 μm, such as less than 5 μm, such as less than 3 μm, such as less than 1 μm. In certain embodiments, the Dv,90 is less than 1 mm, such as less than 100 μm, such as less than 50 μm, such as less than 30 μm, such as less than 20 μm, such as less than 10 μm, such as less than 8 μm, such as less than 5 μm, such as less than 3 μm, such as less than 1 μm. In certain embodiments, the Dv,0 is greater than 10 nm, such as greater than 100 nm, such as greater than 500 nm, such as greater than 1 μm, such as greater than 2 μm, such as greater than 5 μm, such as greater than 10 μm. In certain embodiments, the Dv,1 is greater than 10 nm, such as greater than 100 nm, such as greater than 500 nm, such as greater than 1 μm, such as greater than 2 μm, such as greater than 5 μm, such as greater than 10 μm. In certain embodiments, the Dv,10 is greater than 10 nm, such as greater than 100 nm, such as greater than 500 nm, such as greater than 1 μm, such as greater than 2 μm, such as greater than 5 μm, such as greater than 10 μm.

[0072] In some embodiments, the surface area of the porous carbon scaffold can include a surface area greater than 400 m 2 / g, such as greater than 500 m 2 / g, such as greater than 750 m 2 / g, such as greater than 1000 m 2 / g, such as greater than 1250 m 2 / g, such as greater than 1500 m 2 / g, such as greater than 1750 m 2 / g, such as greater than 2000 m2 / g, e.g., greater than 2500 m 2 / g, e.g., greater than 3000 m 2 / g. In other embodiments, the surface area of the porous carbon scaffold can be less than 500 m 2 / g. In some embodiments, the surface area of the porous carbon scaffold is 200 to 500 m 2 / g. In some embodiments, the surface area of the porous carbon scaffold is 100 to 200 m 2 / g. In some embodiments, the surface area of the porous carbon scaffold is 50 to 100 m 2 / g. In some embodiments, the surface area of the porous carbon scaffold is 10 to 50 m 2 / g. In some embodiments, the surface area of the porous carbon scaffold can be less than 10 m 2 / g.

[0073] In some embodiments, the pore volume of the porous carbon scaffold is greater than 0.4 cm 3 / g, e.g., greater than 0.5 cm 3 / g, e.g., greater than 0.6 cm 3 / g, e.g., greater than 0.7 cm 3 / g, e.g., greater than 0.8 cm 3 / g, e.g., greater than 0.9 cm 3 / g, e.g., greater than 1.0 cm 3 / g, e.g., greater than 1.1 cm 3 / g, e.g., greater than 1.2 cm 3 / g, e.g., greater than 1.4 cm 3 / g, e.g., greater than 1.6 cm 3 / g, e.g., greater than 1.8 cm 3 / g, e.g., greater than 2.0 cm 3 / g. In other embodiments, the pore volume of the porous carbon scaffold is less than 0.5 cm3, e.g., 0.1 cm 3 / g to 0.5 cm 3 / g. In certain other embodiments, the pore volume of the porous carbon scaffold is 0.01 cm 3 / g to 0.1 cm 3 / g.

[0074] In some other embodiments, the porous carbon scaffold is an amorphous activated carbon with a pore volume of 0.2 to 2.0 cm 3 / g. In certain embodiments, the carbon is an amorphous activated carbon with a pore volume of 0.4 to 1.5 cm 3 / g. In certain embodiments, the carbon is an amorphous activated carbon with a pore volume of 0.5 to 1.2 cm 3Amorphous activated carbon of / g. In certain embodiments, the carbon has a pore volume of 0.6 to 1.0 cm 3 Amorphous activated carbon of / g.

[0075] In some other embodiments, the porous carbon support has a tapped density of less than 1.0 g / cm 3 For example, less than 0.8 g / cm 3 For example, less than 0.6 g / cm 3 For example, less than 0.5 g / cm 3 For example, less than 0.4 g / cm 3 For example, less than 0.3 g / cm 3 For example, less than 0.2 g / cm 3 For example, less than 0.1 g / cm 3 .

[0076] The surface functionality of the porous carbon support can vary. One property that can be predicted for the surface functionality is the pH of the porous carbon support. The porous carbon support disclosed in the present invention has a pH value of less than 1 to about 14, for example less than 5, 5 to 8, or greater than 8. In some embodiments, the pH of the porous carbon is less than 4, less than 3, less than 2, or even less than 1. In other embodiments, the pH of the porous carbon is about 5 to 6, about 6 to 7, about 7 to 8, 8 to 9, or 9 to 10. In other embodiments, the pH is high and the pH range of the porous carbon is greater than 8, greater than 9, greater than 10, greater than 11, greater than 12, or even greater than 13.

[0077] The pore volume distribution of the porous carbon support can vary. For example, the % micropores can account for less than 30%, for example less than 20%, for example less than 10%, for example less than 5%, for example less than 4%, for example less than 3%, for example less than 2%, for example less than 1%, for example less than 0.5%, for example less than 0.2%, for example less than 0.1%. In certain embodiments, there is no detectable micropore volume in the porous carbon support.

[0078] The mesopores constituting the porous carbon support can vary. For example, the % mesopores can account for less than 30%, for example less than 20%, for example less than 10%, for example less than 5%, for example less than 4%, for example less than 3%, for example less than 2%, for example less than 1%, for example less than 0.5%, for example less than 0.2%, for example less than 0.1%. In certain embodiments, there is no detectable mesopore volume in the porous carbon support.

[0079] In some embodiments, the pore volume distribution of the porous carbon scaffold includes greater than 50% macropores, such as greater than 60% macropores, such as greater than 70% macropores, such as greater than 80% macropores, such as greater than 90% macropores, such as greater than 95% macropores, such as greater than 98% macropores, such as greater than 99% macropores, such as greater than 99.5% macropores, such as greater than 99.9% macropores.

[0080] In certain preferred embodiments, the pore volume of the porous carbon scaffold comprises a blend of micropores, mesopores, and macropores. Thus, in certain embodiments, the porous carbon scaffold comprises 0 - 20% micropores, 30 - 70% mesopores, and less than 10% macropores. In certain other embodiments, the porous carbon scaffold comprises 0 - 20% micropores, 0 - 20% mesopores, and 70 - 95% macropores. In certain other embodiments, the porous carbon scaffold comprises 20 - 50% micropores, 50 - 80% mesopores, and 0 - 10% macropores. In certain other embodiments, the porous carbon scaffold comprises 40 - 60% micropores, 40 - 60% mesopores, and 0 - 10% macropores. In certain other embodiments, the porous carbon scaffold comprises 80 - 95% micropores, 0 - 10% mesopores, and 0 - 10% macropores. In certain other embodiments, the porous carbon scaffold comprises 0 - 10% micropores, 30 - 50% mesopores, and 50 - 70% macropores. In certain other embodiments, the porous carbon scaffold comprises 0 - 10% micropores, 70 - 80% mesopores, and 0 - 20% macropores. In certain other embodiments, the porous carbon scaffold comprises 0 - 20% micropores, 70 - 95% mesopores, and 0 - 10% macropores. In certain other embodiments, the porous carbon scaffold comprises 0 - 10% micropores, 70 - 95% mesopores, and 0 - 20% macropores.

[0081] In certain embodiments, the pore volume percentage of pores in the porous carbon scaffold that are 100 to 1000 Å (10 to 100 nm) accounts for greater than 30% of the total pore volume, such as greater than 40% of the total pore volume, such as greater than 50% of the total pore volume, such as greater than 60% of the total pore volume, such as greater than 70% of the total pore volume, such as greater than 80% of the total pore volume, such as greater than 90% of the total pore volume, such as greater than 95% of the total pore volume, such as greater than 98% of the total pore volume, such as greater than 99% of the total pore volume, such as greater than 99.5% of the total pore volume, such as greater than 99.9% of the total pore volume.

[0082] In certain embodiments, the pycnometric density of the porous carbon scaffold is from about 1 g / cc to about 3 g / cc, such as from about 1.5 g / cc to about 2.3 g / cc. In other embodiments, the skeletal density is from about 1.5 cc / g to about 1.6 cc / g, from about 1.6 cc / g to about 1.7 cc / g, from about 1.7 cc / g to about 1.8 cc / g, from about 1.8 cc / g to about 1.9 cc / g, from about 1.9 cc / g to about 2.0 cc / g, from about 2.0 cc / g to about 2.1 cc / g, from about 2.1 cc / g to about 2.2 cc / g, or from about 2.2 cc / g to about 2.3 cc / g, from about 2.3 cc to about 2.4 cc / g, such as from about 2.4 cc / g to about 2.5 cc / g.

[0083] C. Production of silicon by chemical vapor infiltration (CVI)

[0084] Chemical vapor deposition (CVD) is a method in which a substrate provides a solid surface that includes a first component of a composite, and a gas thermally decomposes on the solid surface to provide a second component of the composite. For example, this CVD method can be employed to produce an Si-C composite material in which silicon coats the outer surface of silicon particles. Alternatively, chemical vapor infiltration (CVI) is a method in which a substrate provides a porous scaffold that includes a first component of a composite, and a gas thermally decomposes into the pores (into the holes) of the porous scaffold material to provide a second component of the composite.

[0085] In an embodiment, silicon is produced within the pores of a porous carbon scaffold by subjecting the porous carbon particles to a silicon-containing precursor gas in the presence of an elevated temperature and a silicon-containing gas (preferably silane) to decompose the gas into silicon. In some embodiments, the silicon-containing gas can include higher-order silanes (such as disilane, trisilane, and / or tetrasilane), chlorosilanes (such as monochlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane), or mixtures thereof.

[0086] The silicon-containing precursor gas can be mixed with other inert gases, such as nitrogen gas, or hydrogen gas, or argon gas, or helium gas, or combinations thereof. The temperature and time of the process can vary. For example, the temperature can be from 200 to 900 °C, such as from 200 to 250 °C, such as from 250 to 300 °C, such as from 300 to 350 °C, such as from 300 to 400 °C, such as from 300 to 500 °C, such as from 350 to 450 °C, such as from 350 to 400 °C, such as from 350 to 500 °C, such as from 350 to 550 °C, such as from 400 to 500 °C, such as from 500 to 600 °C, such as from 600 to 700 °C, such as from 700 to 800 °C, such as from 800 to 900 °C, such as from 600 to 1100 °C.

[0087] The gas mixture may contain 0.1 - 1% silane and the balance being an inert gas. Alternatively, the gas mixture may contain 1% - 10% silane and the balance being an inert gas. Alternatively, the gas mixture may contain 10% to 20% silane and the balance being an inert gas. Alternatively, the gas mixture may contain 20% to 50% silane and the balance being an inert gas. Alternatively, the gas mixture may contain more than 50% silane and the balance being an inert gas. Alternatively, the gas may be substantially 100% silane gas. Suitable inert gases include, but are not limited to, hydrogen, nitrogen, argon, and combinations thereof.

[0088] The pressure of the CVI method can vary. In some embodiments, the pressure is atmospheric pressure. In some embodiments, the pressure is below atmospheric pressure. In some embodiments, the pressure is above atmospheric pressure.

[0089] C. Physical and Electrochemical Properties of Silicon-Carbon Composites

[0090] Without wishing to be bound by theory, it is believed that due to filling certain desired pore volume structures of the porous carbon scaffold, silicon of nanoscale dimensions (e.g., silicon filling pores in the range of 5 to 1000 nm or other ranges disclosed elsewhere herein) and the favorable properties of other components of the composite (including low surface area, low pycnometric density) result in a composite material having different and favorable properties (e.g., electrochemical performance when the composite constitutes the anode of a lithium-ion energy storage device).

[0091] In certain embodiments, the embedded silicon particles embedded within the composite include nanoscale features. The characteristic length scale of the nanoscale features can preferably be less than 1 μm, preferably less than 300 nm, preferably less than 150 nm, preferably less than 100 μm, preferably less than 50 nm, preferably less than 30 nm, preferably less than 15 nm, preferably less than 10 nm, preferably less than 5 nm.

[0092] In certain embodiments, the shape of the silicon embedded within the composite is spherical. In certain other embodiments, the porous silicon particles are non-spherical, such as rod-like or fibrous structures. In some embodiments, the silicon exists as a layer coating the interior of the pores within the porous carbon scaffold. The depth of this silicon layer can vary, e.g., the depth can be 5 nm to 10 nm, e.g., 5 nm to 20 nm, e.g., 5 nm to 30 nm, e.g., 5 nm to 33 nm, e.g., 10 nm to 30 nm, e.g., 10 nm to 50 nm, e.g., 10 nm to 100 nm, e.g., 10 to 150 nm, e.g., 50 nm to 150 nm, e.g., 100 to 300 nm, e.g., 300 to 1000 nm.

[0093] In some embodiments, the silicon embedded within the composite is nanosized and resides within the pores of the porous carbon scaffold. For example, the embedded silicon can be impregnated, deposited by CVI, or otherwise suitably introduced into the pores within the porous carbon particles, which have pore sizes of 5 to 1000 nm, such as 10 to 500 nm, such as 10 to 200 nm, such as 10 to 100 nm, such as 33 to 150 nm, such as 20 to 100 nm. Other ranges of carbon pore sizes with respect to fractional pore volume are also contemplated, whether micropores, mesopores, or macropores.

[0094] In some embodiments, the pore volume distribution of the carbon scaffold can be described as the number or volume distribution of pores determined based on gas adsorption analysis (such as nitrogen adsorption analysis) as known in the art. In some embodiments, the pore size distribution can be represented by the pore size at which a certain fraction of the total pore volume lies or is below. For example, the pore size at which 10% of the pores lie or are below can be designated as DPv10.

[0095] The DPv10 of the porous carbon scaffold can vary. For example, the DPv10 can be from 0.01 nm to 100 nm, such as 0.1 nm to 100 nm, such as 1 nm to 100 nm, such as 1 nm to 50 nm, such as 1 nm to 40 nm, such as 1 nm to 30 nm, such as 1 nm to 10 nm, such as 1 nm to 5 nm.

[0096] The DPv50 of the porous carbon scaffold can vary. For example, the DPv50 can be from 0.01 nm to 100 nm, such as 0.1 nm to 100 nm, such as 1 nm to 100 nm, such as 1 nm to 50 nm, such as 1 nm to 40 nm, such as 1 nm to 30 nm, such as 1 nm to 10 nm, such as 1 nm to 5 nm. In other embodiments, the DPv50 is from 2 to 100, such as 2 to 50, such as 2 to 30, such as 2 to 20, such as 2 to 15, such as 2 to 10.

[0097] The DPv90 of the porous carbon scaffold can vary. For example, the DPv90 can be from 0.01 nm to 100 nm, such as 0.1 nm to 100 nm, such as 1 nm to 100 nm, such as 1 nm to 50 nm, such as 1 nm to 50 nm, such as 1 nm to 40 nm, such as 1 nm to 30 nm, such as 1 nm to 10 nm, such as 1 nm to 5 nm. In other embodiments, the DPv50 is from 2 nm to 100 nm, such as 2 nm to 50 nm, such as 2 nm to 30 nm, such as 2 nm to 20 nm, such as 2 nm to 15 nm, such as 2 nm to 10 nm.

[0098] In some embodiments, DPv90 is less than 100 nm, such as less than 50 nm, such as less than 40 nm, such as less than 30 nm, such as less than 20 nm, such as less than 15 nm, such as less than 10 nm. In some embodiments, the carbon scaffold comprises a pore volume of greater than 70% micropores (and DPv90 is less than 100 nm, such as DPv90 is less than 50 nm, such as DPv90 is less than 40 nm, such as DPv90 is less than 30 nm, such as DPv90 is less than 20 nm, such as DPv90 is less than 15 nm, such as DPv90 is less than 10 nm, such as DPv90 is less than 5 nm, such as DPv90 is less than 4 nm, such as DPv90 is less than 3 nm. In other embodiments, the carbon scaffold comprises a pore volume of greater than 80% micropores and DPv90 is less than 100 nm, such as DPv90 is less than 50 nm, such as DPv90 is less than 40 nm, such as DPv90 is less than 30 nm, such as DPv90 is less than 20 nm, such as DPv90 is less than 15 nm, such as DPv90 is less than 10 nm, such as DPv90 is less than 5 nm, such as DPv90 is less than 4 nm, such as DPv90 is less than 3 nm.

[0099] The DPv99 of the porous carbon scaffold can vary, for example, DPv99 can be from 0.01 nm to 1000 nm, such as from 0.1 nm to 1000 nm, such as from 1 nm to 500 nm, such as from 1 nm to 200 nm, such as from 1 nm to 150 nm, such as from 1 nm to 100 nm, such as from 1 nm to 50 nm, such as from 1 nm to 20 nm. In other embodiments, DPv99 is from 2 nm to 500 nm, such as from 2 nm to 200 nm, such as from 2 nm to 150 nm, such as from 2 nm to 100 nm, such as from 2 nm to 50 nm, such as from 2 nm to 20 nm, such as from 2 nm to 15 nm, such as from 2 nm to 10 nm.

[0100] Embodiments of the composites with extremely persistent lithium insertion disclosed herein improve the properties of any number of electrical energy storage devices (e.g., lithium ion batteries). In some embodiments, the silicon-carbon composites disclosed herein exhibit a Z of less than 10, such as less than 5, such as less than 4, such as less than 3, such as less than 2, such as less than 1, such as less than 0.1, such as less than 0.01, such as less than 0.001. In certain embodiments, Z is 0.

[0101] In certain preferred embodiments, the silicon-carbon composites comprise the desired low Z in combination with another desired physicochemical and / or electrochemical property or in combination with more than one other desired physicochemical and / or electrochemical property. Table 1 provides a description of certain embodiments of the property combinations of the silicon-carbon composites.

[0102] Table 1. Embodiments of silicon-carbon composites with implemented properties.

[0103]

[0104]

[0105] According to Table 1, the silicon-carbon composite can include

[0106] Combinations of various properties. For example, the silicon-carbon composite can include a Z less than 10, a surface area less than 100 m 2 / g, a first-cycle efficiency greater than 80% and a reversible capacity of at least 1300 mAh / g. For example, the silicon-carbon composite can include a Z less than 10, a surface area less than 100 m 2 / g, a first-cycle efficiency greater than 80% and a reversible capacity of at least 1600 mAh / g. For example, the silicon-carbon composite can include a Z less than 10, a surface area less than 20 m 2 / g, a first-cycle efficiency greater than 85% and a reversible capacity of at least 1600 mAh / g. For example, the silicon-carbon composite can include a Z less than 10, a surface area less than 10 m 2 / g, a first-cycle efficiency greater than 85% and a reversible capacity of at least 1600 mAh / g. For example, the silicon-carbon composite can include a Z less than 10, a surface area less than 10 m 2 / g, a first-cycle efficiency greater than 90% and a reversible capacity of at least 1600 mAh / g. For example, the silicon-carbon composite can include a Z less than 10, a surface area less than 10 m 2 / g, a first-cycle efficiency greater than 90% and a reversible capacity of at least 1800 mAh / g.

[0107] In addition to further including a carbon scaffold having properties also described in this embodiment, the silicon-carbon composite can also include combinations of the above properties. Thus, Table 2 provides a description of certain embodiments of combinations of properties of the silicon-carbon composite.

[0108] Table 2. Embodiments of silicon-carbon composites with implemented properties.

[0109]

[0110] As used herein, the percentages of "micropores", "mesopores", and "macropores" respectively refer to the percentages of micropores, mesopores, and macropores in the total pore volume. For example, a carbon scaffold having 90% micropores is a carbon scaffold in which 90% of the total pore volume of the carbon scaffold is formed by micropores.

[0111] According to Table 2, the silicon-carbon composite can include

[0112] Combinations of various properties. For example, the silicon-carbon composite may include a Z of less than 10, a surface area of less than 100 m 2 / g, a first cycle efficiency greater than 80%, a reversible capacity of at least 1600 mAh / g, a silicon content of 15% - 85%, and a total pore volume of the carbon scaffold of 0.2 - 1.2 cm 3 / g, wherein the scaffold pore volume comprises >80% micropores, <20% mesopores, and <10% macropores. For example, the silicon-carbon composite may include a Z of less than 10, a surface area of less than 20 m 2 / g, a first cycle efficiency greater than 85%, a reversible capacity of at least 1600 mAh / g, a silicon content of 15% - 85%, and a total pore volume of the carbon scaffold of 0.2 - 1.2 cm 3 / g, wherein the scaffold pore volume comprises >80% micropores, <20% mesopores, and <10% macropores. For example, the silicon-carbon composite may include a Z of less than 10, a surface area of less than 10 m 2 / g, a first cycle efficiency greater than 85%, a reversible capacity of at least 1600 mAh / g, a silicon content of 15% - 85%, and a total pore volume of the carbon scaffold of 0.2 - 1.2 cm 3 / g, wherein the scaffold pore volume comprises >80% micropores, <20% mesopores, and <10% macropores. For example, the silicon-carbon composite may include a Z of less than 10, a surface area of less than 10 m 2 / g, a first cycle efficiency greater than 90%, a reversible capacity of at least 1600 mAh / g, a silicon content of 15% - 85%, and a total pore volume of the carbon scaffold of 0.2 - 1.2 cm 3 / g, wherein the scaffold pore volume comprises >80% micropores, <20% mesopores, and <10% macropores. For example, the silicon-carbon composite may include a Z of less than 10, a surface area of less than 10 m 2 / g, a first cycle efficiency greater than 90%, a reversible capacity of at least 1800 mAh / g, a silicon content of 15% - 85%, and a total pore volume of the carbon scaffold of 0.2 - 1.2 cm 3 / g, wherein the scaffold pore volume comprises >80% micropores, <20% mesopores, and <10% macropores.

[0113] Without being bound by theory, the filling of silicon within the pores of the porous carbon traps the porosity within the porous carbon scaffold particles, creating an inaccessible volume, such as a nitrogen-inaccessible volume. Thus, the silicon-carbon composite may exhibit a pycnometric density of less than 2.1 g / cm 3 , for example less than 2.0 g / cm 3 , such as less than 1.9 g / cm 3 , for example less than 1.8 g / cm 3 , such as less than 1.7 g / cm 3, for example, less than 1.6 g / cm 3 , for example, less than 1.4 g / cm 3 , for example, less than 1.2 g / cm 3 , for example, less than 1.0 g / cm 3 .

[0114] In some embodiments, the pycnometric density exhibited by the silicon-carbon composite can be from 1.7 g·cm3 to 2.1 g / cm 3 , for example, from 1.7 g·cm3 to 1.8 g / cm 3 、from 1.8 g·cm3 to 1.9 g / cm 3 , for example, from 1.9 g·cm3 to 2.0 g / cm 3 , for example, from 2.0 g·cm3 to 2.1 g / cm 3 . In some embodiments, the pycnometric density exhibited by the silicon-carbon composite can be from 1.8 g·cm3 to 2.1 g / cm 3 . In some embodiments, the pycnometric density exhibited by the silicon-carbon composite can be from 1.8 g·cm3 to 2.0 g / cm 3 . In some embodiments, the pycnometric density exhibited by the silicon-carbon composite can be from 1.9 g·cm3 to 2.1 g / cm 3 .

[0115] The pore volume of the composite material that exhibits extremely durable lithium insertion can be from 0.01 cm 3 / g to 0.2 cm 3 / g. In certain embodiments, the pore volume of the composite material can be from 0.01 cm 3 / g to 0.15 cm 3 / g, for example, from 0.01 cm 3 / g to 0.1 cm 3 / g, for example, from 0.01 cm 3 / g to 0.05 cm2 / g.

[0116] The particle size distribution of a composite material that exhibits extremely durable lithium intercalation is important for determining power performance as well as volumetric capacity. As packing improves, the volumetric capacity can increase. In one embodiment, the distribution is a Gaussian distribution that is unimodal, bimodal, or multimodal (> 2 distinct peaks, e.g., trimodal) in shape. The nature of the particle size of the composite can be described by D0 (the smallest particle in the distribution), Dv50 (the average particle size), and Dv100 (the largest dimension of the largest particle). The optimal combination of particle packing and performance will be some combination of the following size ranges. Reduction of the particle size in such embodiments can be carried out as is known in the art, e.g., by jet milling in the presence of various gases including air, nitrogen, argon, helium, supercritical vapors, and other gases known in the art.

[0117] In one embodiment, the Dv0 of the composite material can be from 1 nm to 5 microns. In another embodiment, the Dv0 of the composite is 5 nm to 1 micron, e.g., 5 - 500 nm, e.g., 5 - 100 nm, e.g., 10 - 50 nm. In other embodiments, the Dv0 of the composite is 500 nm to 2 microns, or 750 nm to 1μm, or 1 - 2μm. Microns to 2 microns. In other embodiments, the Dv0 of the composite is 2 - 5μm, or > 5μm.

[0118] In some embodiments, the Dv50 of the composite material is 5 nm to 20μm. In other embodiments, the Dv50 of the composite is 5 nm to 1 micron, e.g., 5 - 500 nm, e.g., 5 - 100 nm, e.g., 10 - 50 nm. In other embodiments, the Dv50 of the composite is 500 nm to 2 microns, 750 nm to 1μm, 1 - 2μm. In still other embodiments, the Dv50 of the composite is 1 to 1000μm, e.g., 1 - 100μm, e.g., 1 - 10μm, e.g., 2 - 20μm, e.g., 3 - 15μm, e.g., 4 - 8μm. In certain embodiments, Dv50 > 20μm, e.g., > 50μm, e.g., > 100μm.

[0119] The span (Dv50) / (Dv90 - Dv10) where Dv10, Dv50, and Dv90 represent the particle sizes at 10%, 50%, and 90% of the volume distribution can vary, e.g., from 100 to 10, 10 to 5, 5 to 2, 2 to 1; in some embodiments, the span can be less than 1. In certain embodiments, a composite comprising a particle size distribution of carbon and porous silicon materials can be multimodal, e.g., bimodal or trimodal.

[0120] The surface functionality of the composite materials disclosed in the present invention that exhibit extremely durable lithium intercalation can be altered to obtain desired electrochemical properties. One property of the surface functionality that can be predicted is the pH of the composite material. The composite materials disclosed in the present invention have a pH value of less than 1 to about 14, such as less than 5, 5 to 8, or greater than 8. In some embodiments, the pH of the composite material is less than 4, less than 3, less than 2, or even less than 1. In other embodiments, the pH of the composite material is about 5 to 6, about 6 to 7, about 7 to 8, or 8 to 9, or 9 to 10. In other embodiments, the pH is high and the pH range of the composite material is greater than 8, greater than 9, greater than 10, greater than 11, greater than 12, or even greater than 13.

[0121] The silicon-carbon composite material can contain different amounts of carbon, oxygen, hydrogen, and nitrogen measured by CHNO analysis by gas chromatography. In one embodiment, the carbon content of the composite is greater than 98 wt.% or even greater than 99.9 wt.%, measured by CHNO analysis. In another embodiment, the carbon content of the silicon-carbon composite is about 10 - 90%, such as 20 - 80%, such as 30 - 70%, such as 40 - 60%.

[0122] In some embodiments, the nitrogen content of the silicon-carbon composite material is 0 - 90%, such as 0.1 - 1%, such as 1 - 3%, such as 1 - 5%, such as 1 - 10%, such as 10 - 20%, such as 20 - 30%, such as 30 - 90%.

[0123] In some embodiments, the oxygen content is 0 - 90%, such as 0.1 - 1%, such as 1 - 3%, such as 1 - 5%, such as 1 - 10%, such as 10 - 20%, such as 20 - 30%, such as 30 - 90%.

[0124] The silicon-carbon composite material can also be doped with an electrochemical modifier, and the electrochemical modifier is selected to optimize the electrochemical performance of the unmodified composite. The electrochemical modifier can be doped within the pore structure and / or on the surface of the porous carbon scaffold, within the embedded silicon, or within the final carbon layer, or within the conductive polymer, within the coating, or doped in any number of other ways. For example, in some embodiments, the composite material includes a coating of an electrochemical modifier (such as silicon or Al2O3) on the surface of the carbon material. In some embodiments, the composite material contains more than about 100 ppm of the electrochemical modifier. In certain embodiments, the electrochemical modifier is selected from iron, tin, silicon, nickel, aluminum, and manganese.

[0125] In certain embodiments, the electrochemical modifier comprises an element (e.g., silicon, tin, sulfur) capable of lithiating at 3 to 0 V relative to lithium metal. In other embodiments, the electrochemical modifier comprises a metal oxide (e.g., iron oxide, molybdenum oxide, titanium oxide) capable of lithiating at 3 to 0 V relative to lithium metal. In other embodiments, the electrochemical modifier comprises an element that does not lithiate at 3 to 0 V relative to lithium metal (e.g., aluminum, manganese, nickel, metal phosphates). In other embodiments, the electrochemical modifier comprises a non-metallic element (e.g., fluorine, nitrogen, hydrogen). In other embodiments, the electrochemical modifier includes any one or any combination of the foregoing electrochemical modifiers (e.g., tin-silicon, nickel-titanium oxide).

[0126] The electrochemical modifier can be provided in a variety of forms. For example, in some embodiments, the electrochemical modifier comprises a salt. In other embodiments, the electrochemical modifier comprises one or more elements in elemental form, such as elemental iron, tin, silicon, nickel, or manganese. In other embodiments, the electrochemical modifier comprises one or more elements in oxidized form, such as iron oxide, tin oxide, silicon oxide, nickel oxide, aluminum oxide, or manganese oxide.

[0127] The electrochemical properties of the composite material can be modified at least in part by the amount of the electrochemical modifier in the material, where the electrochemical modifier is an alloy material, such as silicon, tin, indium, aluminum, germanium, gallium. Thus, in some embodiments, the composite material comprises at least 0.10%, at least 0.25%, at least 0.50%, at least 1.0%, at least 5.0%, at least 10%, at least 25%, at least 50%, at least 75%, at least 90%, at least 95%, at least 99%, or at least 99.5% of the electrochemical modifier.

[0128] Compared to the non-lithiated state, the particle size of the composite material can expand upon lithiation. For example, the expansion factor is defined as the ratio of the average particle size of a composite material comprising a porous silicon material upon lithiation to the average particle size under non-lithiated conditions. As is known in the art, this expansion factor for previously known non-optimal silicon-containing materials can be relatively large, e.g., about 4X (corresponding to a 400% volume expansion upon lithiation). The inventors have found that a composite material comprising a porous silicon material can exhibit a lower degree of expansion. For example, the expansion factor can vary from 3.5 to 4, 3.0 to 3.5, 2.5 to 3.0, 2.0 to 2.5, 1.5 to 2.0, 1.0 to 1.5.

[0129] It is contemplated that in certain embodiments, the composite material will comprise a portion of the interception pore volume, i.e., the void volume inaccessible to nitrogen as detected by nitrogen adsorption measurement. Without being bound by theory, this interception pore volume is important because it provides a volume into which silicon can expand upon lithiation.

[0130] In certain embodiments, the ratio of the interception void volume to the volume of silicon constituting the composite particles is from 0.1:1 to 10:1. For example, the ratio of the interception void volume to the volume of silicon constituting the composite particles is from 1:1 to 5:1 or from 5:1 to 10:1. In an embodiment, in order to effectively accommodate the maximum degree of expansion of silicon upon lithiation, the ratio of the interception void volume to the volume of silicon constituting the composite particles is from 2:1 to 5:1, or about 3:1.

[0131] In certain embodiments, the electrochemical properties of the composites disclosed herein are tested in a half-cell; alternatively, the properties of the composites with extremely durable lithium insertion disclosed herein are tested in a full cell (e.g., a full cell button battery, a full cell pouch battery, a prismatic cell, or other battery configurations known in the art). As is known in the art, the anode composition comprising the composites with extremely durable lithium insertion disclosed herein may further comprise various substances. Additional formulation components include, but are not limited to, conductive additives such as conductive carbon (e.g., Super C45, Super P, Ketjenblack carbon, etc.), conductive polymers, etc., binders such as styrene-butadiene rubber carboxymethyl cellulose sodium (SBR-Na-CMC), polyvinylidene fluoride (PVDF), polyimide (PI), polyacrylic acid (PAA), etc., and combinations thereof. In certain embodiments, the binder may comprise lithium ions as counter ions.

[0132] Other substances constituting the electrode are known in the art. The % by weight of the active material in the electrode may vary, e.g., 1 to 5%, e.g., 5 to 15%, e.g., 15 to 25%, e.g., 25 to 35%, e.g., 35 to 45%, e.g., 45 to 55%, e.g., 55 to 65%, e.g., 65 to 75%, e.g., 75 to 85%, e.g., 85 to 95%. In some embodiments, the active material accounts for 80 to 95% of the electrode. In certain embodiments, the amount of the conductive additive in the electrode may vary, e.g., 1 to 5%, 5 to 15%, e.g., 15 to 25%, e.g., 25 to 35%. In some embodiments, the amount of the active material in the electrode is 5 to 25%. In certain embodiments, the amount of the binder may vary, e.g., 1 to 5%, 5 to 15%, e.g., 15 to 25%, e.g., 25 to 35%. In certain embodiments, the amount of the conductive additive in the electrode is 5 to 25%.

[0133] As is known in the art, silicon-carbon composite materials can be prelithiated. In certain embodiments, prelithiation is achieved electrochemically, e.g., in a half-cell, before assembling a lithium anode comprising a porous silicon material into a full-cell lithium-ion battery. In certain embodiments, prelithiation is achieved by doping the cathode with a lithium-containing compound, such as a lithium salt. In this context, examples of suitable lithium salts include, but are not limited to, lithium(II) tetrabromonickelate, lithium(II) tetrachlorocuprate, lithium azide, lithium benzoate, lithium bromide, lithium carbonate, lithium chloride, lithium cyclohexanebutyrate, lithium fluoride, lithium formate, lithium hexafluoroarsenate(V), lithium hexafluorophosphate, lithium hydroxide, lithium iodate, lithium iodide, lithium metaborate, lithium perchlorate, lithium phosphate, lithium sulfate, lithium tetraborate, lithium tetrachloroaluminate, lithium tetrafluoroborate, lithium thiocyanate, lithium trifluoromethanesulfonate, lithium trifluoromethanesulfonate, and combinations thereof.

[0134] Anodes comprising silicon-carbon composite materials can be paired with a variety of cathode materials to yield full-cell lithium-ion batteries. Examples of suitable cathode materials are known in the art. Examples of such cathode materials include, but are not limited to, LiCoO2 (LCO), LiNi 0.8 Co 0.15 Al 0.05 O2 (NCA), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NMC), LiMn2O4 and variants (LMO), and LiFePO4 (LFP).

[0135] For full-cell lithium-ion batteries comprising an anode that also comprises a silicon-carbon composite material, the pairing of the cathode and the anode can be varied. For example, the ratio of cathode to anode capacity can vary from 0.7 to 1.3. In certain embodiments, the ratio of cathode to anode capacity can vary from 0.7 to 1.0, such as from 0.8 to 1.0, such as from 0.85 to 1.0, such as from 0.9 to 1.0, such as from 0.95 to 1.0. In other embodiments, the ratio of cathode to anode capacity can vary from 1.0 to 1.3, such as from 1.0 to 1.2, such as from 1.0 to 1.15, such as from 1.0 to 1.1, such as from 1.0 to 1.05. In other embodiments, the ratio of cathode to anode capacity can vary from 0.8 to 1.2, such as from 0.9 to 1.1, such as from 0.95 to 1.05.

[0136] For a full cell lithium ion battery comprising an anode that also includes a silicon-carbon composite material, the voltage window for charging and discharging can be varied. In this regard, the voltage window can vary as is known in the art, depending on the various properties of the lithium ion battery. For example, the choice of cathode plays a role in the selected voltage window, as is known in the art. For example, instances of voltage windows vary in potential relative to Li / Li+ from 2.0 V to 5.0 V, such as 2.5 V to 4.5 V, such as 2.5 V to 4.2 V.

[0137] For a full cell lithium ion battery comprising an anode that also includes a silicon-carbon composite material, the strategy for conditioning the battery can vary as is known in the art. For example, conditioning can be accomplished by one or more charge and discharge cycles at various rates (e.g., at a rate slower than the desired cycling rate). As is known in the art, the conditioning process can also include the steps of unsealing the lithium ion battery, evacuating any gas generated therein during conditioning, and subsequently resealing the lithium ion battery.

[0138] For a full cell lithium ion battery comprising an anode that also includes a silicon-carbon composite material, the cycling rate can vary as is known in the art. For example, the rate can be C / 20 to 20C, such as C10 to 10C, such as C / 5 to 5C. In certain embodiments, the cycling rate is C / 10. In certain embodiments, the cycling rate is C / 5. In certain embodiments, the cycling rate is C / 2. In certain embodiments, the cycling rate is 1C. In certain embodiments, the cycling rate is 1C, where the rate is periodically reduced to a slower rate, e.g., cycling at 1C, where every 20th cycle employs a C / 10 rate. In certain embodiments, the cycling rate is 2C. In certain embodiments, the cycling rate is 4C. In certain embodiments, the cycling rate is 5C. In certain embodiments, the cycling rate is 10C. In certain embodiments, the cycling rate is 20C.

[0139] The first cycle efficiency of the extremely durable lithium insertion composite disclosed herein is determined by comparing the lithium inserted into the anode during the first cycle with the lithium deinserted from the anode during the first cycle (prior to prelithiation modification). When insertion and deinsertion are equal, the efficiency is 100%. As is known in the art, the anode material can be tested in a half cell where the counter electrode is lithium metal, the electrolyte is 1M LiPF6 1:1 ethylene carbonate:diethyl carbonate (EC:DEC), and a commercially available polypropylene separator is used. In certain embodiments, the electrolyte can include various additives known to provide improved performance, such as fluoroethylene carbonate (FEC) or other related fluorinated carbonate compounds, or ester co-solvents such as methyl butyrate, vinylene carbonate, and other electrolyte additives known to improve the electrochemical performance of silicon-containing anode materials.

[0140] The Coulombic efficiency can be averaged, for example, when tested in a half-cell, averaged from cycle 7 to cycle 25. The Coulombic efficiency can be averaged, for example, when tested in a half-cell, averaged from cycle 7 to cycle 20. In certain embodiments, the average efficiency of a composite with extremely durable lithium insertion is greater than 0.9 or 90%. In certain embodiments, the average efficiency is greater than 0.95 or 95%. In certain other embodiments, the average efficiency is 0.99 or greater, such as 0.991 or greater, such as 0.992 or greater, such as 0.993 or greater, such as 0.994 or greater, such as 0.995 or greater, such as 0.996 or greater, such as 0.997 or greater, such as 0.998 or greater, such as 0.999 or greater, such as 0.9991 or greater, such as 0.9992 or greater, such as 0.9993 or greater, such as 0.9994 or greater, such as 0.9995 or greater, such as 0.9996 or greater, such as 0.9997 or greater, such as 0.9998 or greater, such as 0.9999 or greater.

[0141] In other embodiments, the present disclosure provides a composite material that exhibits extremely durable lithium insertion, wherein when the composite material is incorporated into an electrode of a lithium-based energy storage device, the volumetric capacity of the composite material is at least 10% greater than when the lithium-based energy storage device includes a graphite electrode. In some embodiments, the lithium-based energy storage device is a lithium-ion battery. In other embodiments, the volumetric capacity of the composite material in the lithium-based energy storage device is at least 5%, at least 10%, at least 15% greater than the volumetric capacity of the same electrical energy storage device having a graphite electrode. In other embodiments, the volumetric capacity of the composite material in the lithium-based energy storage device is at least 20%, at least 30%, at least 40%, at least 50%, at least 200%, at least 100%, at least 150% or at least 200% greater than the volumetric capacity of the same electrical energy storage device having a graphite electrode.

[0142] As is known in the art, the composite material can be prelithiated. These lithium atoms may or may not be separated from the carbon. The number of lithium atoms relative to six carbon atoms can be calculated by techniques known to those skilled in the art:

[0143] #Li = Q x 3.6 x MM / (C% x F)

[0144] where Q is the lithium deintercalation capacity measured in mAh / g relative to lithium metal between a voltage of 5 mV and 2.0 V, MM is the molecular weight of 72 or six carbons, F is the Faraday constant of 96,500, and C% is the mass percentage of carbon present in the structure measured by CHNO or XPS.

[0145] The characteristics of the composite material can lie in the ratio of lithium atoms to carbon atoms (Li:C), which can vary from about 0:6 to 2:6. In some embodiments, the Li:C ratio is from about 0.05:6 to about 1.9:6. In other embodiments, the maximum Li:C ratio where lithium is in ionic form rather than metallic form is 2.2:6. In certain other embodiments, the Li:C ratio is from about 1.2:6 to about 2:6, from about 1.3:6 to about 1.9:6, from about 1.4:6 to about 1.9:6, from about 1.6:6 to about 1.8:6, or from about 1.7:6 to about 1.8:6. In other embodiments, the Li:C ratio is greater than 1:6, greater than 1.2:6, greater than 1.4:6, greater than 1.6:6, or even greater than 1.8:6. In even other embodiments, the Li:C ratio is about 1.4:6, about 1.5:6, about 1.6:6, about 1.6:6, about 1.7:6, about 1.8:6, or about 2:6. In a specific embodiment, the Li:C ratio is about 1.78:6.

[0146] In certain other embodiments, the Li:C ratio of the composite material is from about 1:6 to about 2.5:6, from about 1.4:6 to about 2.2:6, or from about 1.4:6 to about 2:6. In other embodiments, the composite material may not necessarily contain lithium, but have the ability to absorb lithium (i.e., the ability to absorb a certain amount of lithium), such as when cycling the material between two voltage conditions (in the case of a lithium-ion half-cell, an exemplary voltage window is between 0 and 3V, such as 0.005 to 2.7V, such as 0.005 to 1V, such as 0.005 to 0.8V). Although not wishing to be bound by theory, it is believed that the lithium absorption ability of the composite material contributes to their excellent performance in lithium-based energy storage devices. The lithium absorption ability is expressed as the ratio of lithium atoms absorbed by the composite material. In certain other embodiments, the lithium absorption ability of the composite material showing extremely durable lithium intercalation is from about 1:6 to about 2.5:6, from about 1.4:6 to about 2.2:6, or from about 1.4:6 to about 2.2:6.

[0147] In certain other embodiments, the lithium absorption ability is from about 1.2:6 to about 2:6, from about 1.3:6 to about 1.9:6, from about 1.4:6 to about 1.9:6, from about 1.6:6 to about 1.8:6, or from about 1.7:6 to about 1.8:6. In other embodiments, the lithium absorption ability is greater than 1:6, greater than 1.2:6, greater than 1.4:6, greater than 1.6:6, or even greater than 1.8:6. In even other embodiments, the Li:C ratio is about 1.4:6, about 1.5:6, about 1.6:6, about 1.6:6, about 1.7:6, about 1.8:6, or about 2:6. In a specific embodiment, the Li:C ratio is about 1.78:6.

[0148] Examples

[0149] Example 1. Preparation of silicon-carbon composite materials by CVI. The properties of the carbon scaffold (carbon scaffold 1) used to prepare the silicon-carbon composite are shown in Table 3. Using carbon scaffold 1, a silicon-carbon composite (silicon-carbon composite 1) was prepared by CVI as follows. Place 0.2 grams of amorphous porous carbon in a 2-inch by 2-inch ceramic crucible and place it in the center of a horizontal tube furnace. Seal the furnace and continuously purge with nitrogen at 500 cubic centimeters per minute (ccm). Raise the furnace temperature to a peak temperature of 450 °C at a rate of 20 °C / min and equilibrate it at this peak temperature for 30 minutes. At this time, turn off the nitrogen, then introduce silane and hydrogen at flow rates of 50 ccm and 450 ccm respectively, with a total residence time of 30 minutes. After this residence time, turn off the silane and hydrogen, and introduce nitrogen into the furnace again to purge the internal atmosphere. At the same time, turn off the furnace heat and let it cool to ambient temperature. Subsequently, the completed Si-C material was removed from the furnace.

[0150] Table 3. Description of the carbon scaffold used in Example 1.

[0151]

[0152] Example 2. Analysis of various silicon composite materials. Use a variety of carbon scaffold materials, and characterize the carbon scaffold materials by nitrogen adsorption gas analysis to determine the specific surface area, total pore volume, and the fraction of pore volume including micropores, mesopores, and macropores. The characterization data of the carbon scaffold materials are shown in Table 4, that is, the data of the carbon scaffold surface area, pore volume, and pore volume distribution (% micropores, % mesopores, and % macropores), all determined by nitrogen adsorption analysis.

[0153] Table 4. Properties of various carbon scaffold materials.

[0154]

[0155] Use the carbon scaffold samples described in Table 4 to prepare various silicon-carbon composite materials using the CVI method in a static bed configuration as generally described in Example 1. These silicon-carbon samples were prepared using a range of process conditions: silane concentration from 1.25% to 100%, dilution gas as nitrogen or hydrogen, and the starting mass of the carbon scaffold from 0.2 g to 700 g.

[0156] The surface area of the silicon-carbon composite was measured. The silicon-carbon composite was also analyzed by TGA to determine the silicon content and Z. The silicon-carbon composite material was also tested in a half-cell button battery. The anode of the half-cell button battery can include 60-90% of the silicon-carbon composite, 5-20% of Na-CMC (as a binder), and 5-20% of Super C45 (as a conductive enhancer), and the electrolyte can include ethylene carbonate:diethylene carbonate in a ratio of 2:1, 1M of LiPF6, and 10% of vinylene carbonate. The half-cell button battery can be cycled at a rate of C / 5 for 5 cycles at 25 °C and then at a rate of C / 10. The voltage can be cycled between 0 V and 0.8 V, alternatively, the voltage can be cycled between 0 V and 1.5 V. Based on the half-cell button battery data, the maximum capacity can be measured, as well as the average Coulombic efficiency (CE) in the cycle range from cycle 7 to cycle 20. The physicochemical and electrochemical properties of various silicon-carbon composite materials are shown in Table 5.

[0157] Table 5. Properties of various silicon-carbon materials.

[0158]

[0159] ND = Not Determined

[0160] A graph of the average Coulombic efficiency as a function of Z is shown in Figure 1 . It can be seen that for the silicon-carbon samples with low Z, the average Coulombic efficiency increases significantly. In particular, all silicon-carbon samples with Z less than 10.0 exhibit an average Coulombic efficiency > 0.9941, and it is observed that all silicon-carbon samples with Z greater than 10 (silicon-carbon composite sample 12 to silicon-carbon composite sample 16) have an average Coulombic efficiency < 0.9909. Without being bound by theory, the higher Coulombic efficiency of the silicon-carbon samples with Z < 10 provides excellent cycle stability in full-cell lithium-ion batteries. Other examinations of the table revealed a surprising and unexpected finding that the combination of Z < 10 and a carbon scaffold containing > 69.1 micropores in the silicon-carbon composite sample provides an average Coulombic efficiency > 0.9969.

[0161] Thus, in a preferred embodiment, the silicon-carbon composite material comprises a Z less than 10, such as a Z less than 5, such as a Z less than 3, such as a Z less than 2, such as a Z less than 1, such as a Z less than 0.5, such as a Z less than 0.1, or a Z of 0.

[0162] In certain preferred embodiments, the silicon-carbon composite material comprises a carbon scaffold with a Z value less than 10 and >70% micropores, such as a Z value less than 10 and >80% micropores, such as a Z value less than 10 and >90% micropores, such as a Z value less than 10 and >95% micropores, such as a Z value less than 5 and >70% micropores, such as a Z value less than 5 and >80% micropores, such as a Z value less than 5 and >90% micropores, such as a Z value less than 5 and >95% micropores, such as a Z value less than 3 and >70% micropores, such as a Z value less than 3 and >80% micropores, such as a Z value less than 3 and >90% micropores, such as a Z value less than 3 and >95% micropores, such as a Z value less than 2 and >70% micropores, such as a Z value less than 2 and >80% micropores, such as a Z value less than 2 and >90% micropores, such as a Z value less than 2 and >95% micropores, such as a Z value less than 1 and >70% micropores, such as a Z value less than 1 and >80% micropores, such as a Z value less than 1 and >90% micropores, such as a Z value less than 1 and >95% micropores, such as a Z value less than 0.5 and >70% micropores, such as a Z value less than 0.5 and >80% micropores, such as a Z value less than 0.5 and >90% micropores, such as a Z value less than 0.5 and >95% micropores, such as a Z value less than 0.1 and >70% micropores, such as a Z value less than 0.1 and >80% micropores, such as a Z value less than 0.1 and >90% micropores, such as a Z value less than 0.1 and >95% micropores, such as a Z value of 0 and >70% micropores, such as a Z value of 0 and >80% micropores, such as a Z value of 0 and >90% micropores, such as a Z value of 0 and >95% micropores.

[0163] In certain preferred embodiments, the silicon-carbon composite material comprises a carbon scaffold with a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 100 m 2 / g; for example, a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 50 m 2 / g; for example, a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 30 m 2 / g; for example, a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 10 m 2 / g; for example, a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 5 m 2 / g; for example, a Z value less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 50 m 2 / g; e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 30 m 2 / g; e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 10 m 2 / g; e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 5 m 2 / g; e.g., Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 50 m 2 / g; e.g., Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 30 m 2 / g; e.g., Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 10 m 2 / g; e.g., Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 5 m 2 / g; e.g., Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 50 m 2 / g; e.g., Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 30 m 2 / g; e.g., Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 10 m 2 / g; e.g., Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon, and the surface area is less than 5 m 2 / g.

[0164] In certain preferred embodiments, the silicon-carbon composite material comprises a carbon scaffold with Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 100 m 2 / g; e.g., Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g; e.g., Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m 2 / g; e.g., Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g; e.g., Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g; e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g; e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m 2 / g; e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g; e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g; e.g., Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g; e.g., Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m 2 / g; e.g., Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g; e.g., Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g; e.g., Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g; e.g., Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m 2 / g; e.g., Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g; e.g., Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g.

[0165] Example 3. dV / dQ of various silicon composites. Differential capacity curves (dQ / dV vs. voltage) are commonly used as non-destructive tools to understand phase transformations as a function of voltage in lithium battery electrodes (M.N. Obrovac et al., Structural Changes in Silicon Anodes during Lithium Insertion / Extraction, Electrochemical and Solid-State Letters, 7(5) A93-A96 (2004); Ogata, K. et al., Revealing lithium–silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy. Nat. Commun. 5:3217). The differential capacity plots presented here were calculated from data obtained by galvanostatic cycling at 5 mV to 0.8 V at a rate of 0.1 C in a half-cell coin cell at 25 °C. Typical differential capacity curves of silicon-based materials with lithium in half-cells can be found in many references (Loveridge, M.J. et al., Towards High Capacity Li-Ion Batteries Based on Silicon-Graphene Composite Anodes and Sub-micron V-doped LiFePO4 Cathodes. Sci. Rep. 6, 37787; doi:10.1038 / srep37787 (2016); M.N. Obrovac et al., Li15Si4 Formation in Silicon Thin Film Negative Electrodes, Journal of The Electrochemical Society, 163(2) A255-A261 (2016); Q. Pan et al., Improved electrochemical performance of micro-sized SiO-based composite anode by prelithiation of stabilized lithium metal powder, Journal of Power Sources 347(2017) 170-177). The first-cycle lithiation behavior depends on factors such as the crystallinity and oxygen content of silicon.

[0166] After the first cycle, prior amorphous silicon materials in the art showed two specific phase change peaks in the lithiation dQ / dV vs. V plot, and correspondingly two specific phase change peaks in the delithiation dQ / dV vs. V plot. For lithiation, one peak corresponding to the lithium-poor Li-Si alloy phase appears at 0.2 to 0.4 V, while another peak corresponding to the lithium-rich Li-Si alloy phase appears below 0.15 V. For delithiation, one delithiation peak corresponding to lithium deintercalation appears below 0.4 V, while another peak appears at 0.4 V to 0.55 V. If the Li15Si4 phase forms during lithiation, it delithiates at ~0.45 V and exhibits a very narrow and sharp peak.

[0167] Figure 2 The dQ / dV vs. voltage curve for cycle 2 of the silicon-carbon composite corresponding to silicon-carbon composite 3 of Example 1 is depicted. Silicon-carbon composite 3 contains 0.6 of Z. For ease of identification, the figure is divided into regions I, II, II, IV, V, and VI. Regions I (0.8 V to 0.4 V), II (0.4 V to 0.15 V), III (0.15 V to 0 V) constitute the lithiation potential, and regions IV (0 V to 0.4 V), V (0.4 V to 0.55 V), VI (0.55 V to 0.8 V) include the delithiation potential. As described above, prior amorphous silicon-based materials in the art exhibited phase change peaks in two regions (regions II and III) in the lithiation potential and in two regions (regions IV and V) in the delithiation potential.

[0168] As can be seen from Figure 2 the dQ / dV vs. voltage curve reveals surprising and unexpected results. Silicon-carbon composite 3 (which contains 0.6 of Z) includes two additional peaks in the dQ / dV vs. voltage curve, namely region I in the lithiation potential and region VI in the delithiation potential. All 6 peaks are reversible and are also observed in subsequent cycles, as shown in Figure 3

[0169] Without being bound by theory, this three-peak behavior of the dQ / dV vs. V curve is novel and equally reflects a novel form of silicon.

[0170] Notably, the new peaks observed in regions I and VI are more prominent in some scaffold matrices and are completely absent in other samples exemplifying the prior art (silicon-carbon composite samples with Z > 10, see the explanation and the table below).

[0171] Figure 4 ​Shows the dQ / dV vs. V curve of silicon-carbon composite 3, where new peaks in regions I and VI are evident compared to silicon-carbon composites 15, 16, and 14 (all three with Z > 10 and whose dQ / dV vs. V curves have no peaks in regions I and VI).

[0172] Without being bound by theory, these new peaks observed in regions I and VI pertain to the nature of silicon impregnated into the porous carbon scaffold, i.e., to the interactions between and among the properties of the porous carbon scaffold, silicon impregnated into the porous carbon scaffold via CVI, and lithium. To provide a quantitative analysis, we define in this article a parameter which is calculated as the normalized peak I with respect to peak III:

[0173]

[0174] where dQ / dV is measured in a half-cell button cell, and region I is 0.8V - 0.4V and region III is 0.15V - 0V; the half-cell button cell is produced as known in the art. If the Si-C sample shows a peak related to graphite in region III of the differential curve, it is omitted when calculating the D factor, and a Li-Si related phase change peak is used instead. For this example, the half-cell button cell includes an anode that contains 60 - 90% silicon-carbon composite, 5 - 20% SBR-Na-CMC, and 5 - 20% Super C45. In Figure 5 shows the calculation example of silicon-carbon composite 3. In this case, the maximum peak height in region I is -2.39 and is found at a voltage of 0.53V. Similarly, the maximum peak height in region III is -9.71 at 0.04V. In this case, the can be calculated using the above formula to obtain values determined from the half-cell button cell data of various silicon-carbon composites given in Example 2. These data are summarized in Table 6.

[0175] Table 6. Properties of various silicon-carbon materials.

[0176]

[0177] ND = Not determined; * These data for the first cycle efficiency in parentheses were measured for a voltage window of 5 mV to 1.5V.

[0178] The data in Table 6 reveal an unexpected relationship between reducing Z and increasing All silicon-carbon composites with Z < 10 have And all silicon-carbon composites with Z > 10 have In fact, all silicon-carbon composites with Z > 10 have This relationship also exists in Figure 6 and is demonstrated therein. Without being bound by theory, the silicon material containing For example corresponds to a new form of silicon. Alternatively, the silicon material containing corresponds to a new form of silicon. Without being bound by theory, the silicon material containing is characteristic of the silicon material, where the silicon is amorphous, nano-sized silicon, confined within pores, such as pores of a porous carbon scaffold. Silicon-carbon composites including those containing For example correspond to novel silicon-carbon composites. Alternatively, the silicon-carbon composites containing correspond to novel silicon-carbon composites.

[0179] In certain embodiments, the silicon-carbon composite contains or In some embodiments, In some embodiments, or

[0180] In certain embodiments, the silicon-carbon composite contains a carbon scaffold with Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further contains 30%-60% silicon, and the surface area is less than 100 m 2 / g, For example, Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further contains 30%-60% silicon, and the surface area is less than 50 m 2 / g, For example, Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further contains 30%-60% silicon, and the surface area is less than 30 m 2 / g, For example, Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further contains 30%-60% silicon, and the surface area is less than 10 m 2 / g, For example, Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further contains 30%-60% silicon, and the surface area is less than 5 m 2 / g,

[0181] In certain embodiments, the silicon-carbon composite material comprises a carbon scaffold with a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 100 m 2 / g, e.g., a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 50 m 2 / g, e.g., a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 30 m 2 / g, e.g., a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 10 m 2 / g, e.g., a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 5 m 2 / g,

[0182] In certain embodiments, the silicon-carbon composite material comprises a carbon scaffold with a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 100 m 2 / g, e.g., a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g, e.g., a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m 2 / g, e.g., a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g, e.g., a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g,

[0183] In certain embodiments, the silicon-carbon composite material comprises a carbon scaffold with a Z value less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 100 m 2 / g, For example, Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 50 m 2 / g, For example, Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 30 m 2 / g, For example, Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 10 m 2 / g, For example, Z less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 5 m 2 / g,

[0184] In certain embodiments, the silicon-carbon composite comprises a carbon scaffold with Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 100 m 2 / g, For example, Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g, For example, Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m 2 / g, For example, Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g, For example, Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g,

[0185] In certain embodiments, the silicon-carbon composite comprises a carbon scaffold with Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 100 m 2 / g, For example, Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 50 m 2 / g, For example, Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 30 m2 / g, e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 10 m 2 / g, e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 5 m 2 / g,

[0186] In certain embodiments, the silicon-carbon composite comprises a carbon scaffold with Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 100 m 2 / g, e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g, e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m 2 / g, e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g, e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g,

[0187] In certain embodiments, the silicon-carbon composite comprises a carbon scaffold with Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 100 m 2 / g, e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 50 m 2 / g, e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 30 m 2 / g, e.g., Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 10 m 2 / g, For example, Z less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 5 m 2 / g,

[0188] In certain embodiments, the silicon-carbon composite comprises a carbon scaffold with Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 100 m 2 / g, For example, Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g, For example, Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m 2 / g, For example, Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g, For example, Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g,

[0189] In certain embodiments, the silicon-carbon composite comprises a carbon scaffold with Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 100 m 2 / g, For example, Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 50 m 2 / g, For example, Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 30 m 2 / g, For example, Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 10 m 2 / g, For example, Z less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 5 m 2 / g,

[0190] In certain embodiments, the silicon-carbon composite material comprises a carbon scaffold with a Z value less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 100 m 2 / g, e.g., a Z value less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g, e.g., a Z value less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m 2 / g, e.g., a Z value less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g, e.g., a Z value less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g,

[0191] In certain embodiments, the silicon-carbon composite material comprises a carbon scaffold with a Z value less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 100 m 2 / g, e.g., a Z value less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 50 m 2 / g, e.g., a Z value less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 30 m 2 / g, e.g., a Z value less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 10 m 2 / g, e.g., a Z value less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 5 m 2 / g,

[0192] In certain embodiments, the silicon-carbon composite material comprises a carbon scaffold with a Z value less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 100 m 2 / g, For example, Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g, For example, Z less than 5 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m 2 / g, For example, Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g, For example, Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g,

[0193] In certain embodiments, the silicon-carbon composite comprises a carbon scaffold with Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 100 m 2 / g, For example, Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 50 m 2 / g, For example, Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 30 m 2 / g, For example, Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 10 m 2 / g, For example, Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 5 m 2 / g,

[0194] In certain embodiments, the silicon-carbon composite comprises a carbon scaffold with Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 100 m 2 / g, For example, Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 50 m 2 / g, For example, Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 30 m2 / g, such as Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 10 m 2 / g, such as Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon, and the surface area is less than 5 m 2 / g,

[0195] In certain embodiments, the silicon-carbon composite material comprises a carbon scaffold with Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 100 m 2 / g, such as Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 50 m 2 / g, such as Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 30 m 2 / g, such as Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 10 m 2 / g, such as Z less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon, and the surface area is less than 5 m 2 / g,

[0196] Example 4. Particle size distribution of various carbon scaffold materials. The particle size distribution of various carbon scaffold materials was determined by using a laser diffraction particle size analyzer known in the art. Table 7 gives the data, specifically Dv,1, Dv10, Dv50, Dv,90 and Dv,100.

[0197] Table 7. Properties of various carbon scaffold materials.

[0198]

[0199] Example 5. For the preparation of various silicon-composites, the influence of CVI process variables on the conversion fraction of silicon-containing gas to elemental silicon. Table 8 shows several key CVI process parameters for the production of various silicon-carbon materials. For these examples, two reactor types were used, a fixed-bed (SB) type and a horizontal moving-bed (HMB) type. In the fixed-bed (SB) type, the bed of the porous carbon skeleton is fixed and resides in the heating zone of the reactor. In the horizontal moving-bed (HMB) type, the bed of the porous carbon moves horizontally through the hot zone. Silicon-carbon composite sample 4, silicon-carbon composite sample 5, silicon-carbon composite sample 7, and silicon-carbon composite sample 8 were prepared using the HMB configuration, while all other silicon-carbon composite samples listed in Table 8 were prepared using the SB configuration. Other reactor types are envisioned. In other embodiments, the CVI reactor type can vary. For example, the CVI reactor can be a vibration-thermal assisted CVI (VTA-CVI) reactor. In other embodiments, the CVI reactor type can be a convection-thermal assisted CVI (CTA-CVI) reactor. In other embodiments, the CVI reactor type can be a rotary CVI kiln. In other embodiments, the CVI reactor type can be a fluidized-bed CVI (FB-CVI) reactor. In the examples of the present invention, the CVI process is carried out as an intermittent process for 1 to 6 hours. In other embodiments, the CVI process can be run as a semi-batch process. In certain other embodiments, the CVI process can be run as a continuous process.

[0200] Table 8. CVI process data for the production of various silicon-carbon materials.

[0201]

[0202]

[0203] *For this sample, the silane flow rate was changed. Therefore, in this case, Y CVI is calculated as the total moles of silane per hour, i.e., calculated as the total moles of silane delivered to the CVI reactor divided by the total CVI reaction time.

[0204] As shown in Table 8, for the samples produced according to this example, the CVI temperature varied from 400 °C to 525 °C. The CVI process can employ other temperature ranges, such as 350 °C to 550 °C, such as 350 °C to 500 °C, such as 350 °C to 450 °C, such as 375 °C to 450 °C, such as 380 °C to 450 °C, such as 385 °C to 450 °C, such as 390 °C to 450 °C.

[0205] For samples produced according to this embodiment, Table 8 also shows that the silicon-containing precursor gas is silane, and the concentration of silane varies from 1.25% to 100% expressed as a mass fraction of the total gas composition. For samples in which silane gas is mixed with a dilution gas, the dilution gas is variable, either hydrogen (H2) or nitrogen (N2). Other dilution gases can be contemplated, such as argon.

[0206] The CVI process can be carried out when the gas introduced into the CVI reactor contains 100% silane. Alternatively, the gas introduced into the CVI reactor contains less than 100% silane and also contains a dilution gas including hydrogen, nitrogen, argon, or a combination thereof.

[0207] For samples produced according to this embodiment, Table 8 also shows that the areal loading of the starting carbon support material in the bed varies from 0.0039 g / cm 2 to 0.5434 g / cm 2 . In other contemplated embodiments, the areal loading of the carbon support material in the bed can vary, for example, from 0.001 g / cm 2 to 10 g / cm 2 . In other embodiments, the areal loading of the carbon support material in the bed can vary, for example, from 1 g / cm 2 to 5 g / cm 2 . In other contemplated embodiments, the areal loading of the carbon support material in the bed can vary, for example, from 5 g / cm 2 to 10 g / cm 2 . In other contemplated embodiments, the areal loading of the carbon support material in the bed can be greater than 10 g / cm 2 .

[0208] Alternatively, the areal loading of the carbon support material in the bed can vary, for example, from 0.0001 g / cm 2 to 1 g / cm 2 . For example, the areal loading of the carbon support material in the bed can vary to 0.001 g / cm 2 to 1 g / cm 2 , or 0.002 g / cm 2 to 1 g / cm 2 , or 0.003 g / cm 2 to 1 g / cm 2 , or 0.004 g / cm 2 to 1 g / cm 2 , or 0.005 g / cm 2 to 1 g / cm 2 . In some embodiments, the areal loading of the carbon support material in the bed can vary to 0.001 g / cm 2from 0 to 1 g / cm 2 .

[0209] For samples produced according to this example, it is also shown in Table 8 that the silane flow rate into the CVI reactor can be normalized with respect to the carbon support. Thus, the silane flow rate normalized to the carbon support can vary. Since 1 mole of silane gas contains 1 mole of silicon, it can also be described that the silicon flow rate normalized to the carbon support can vary. This process parameter can be expressed as:

[0210]

[0211] In the current example, since the silicon-containing gas used for the CVI process is silane and each mole of silane contains one mole of silicon, the above equation can alternatively be expressed as:

[0212]

[0213] Surprising and unexpected results include the utilization rate of silane gas during the CVI process for preparing the silicon-carbon composite. The utilization rate expressed as a percentage can be defined as:

[0214]

[0215] where the number of moles of silicon in the silicon-carbon composite is determined by the % silicon in the silicon-carbon composite measured by TGA after completion of the CVI process. Still for this determination, the number of moles of silicon raw material is the total number of moles of silicon introduced into the CVI reactor in the form of silicon-containing gas during the CVI process to convert the porous carbon support and the silicon-containing gas into the silicon-carbon composite. For embodiments where the silicon-containing gas is silane, 1 mole of silicon is present per mole of silane, thus:

[0216]

[0217] In certain embodiments, the silane flow rate remains constant during the duration of the CVI reaction. In this case, the number of moles of silane / hour used to calculate Y CVI is the molar flow rate of silane in mol / h. In some embodiments, the silane flow rate can vary, for example, in a stepwise manner and / or in a uniformly varying manner. In some embodiments, the silane flow rate is lower at the start and end of the CVI reaction duration. In cases where the flow rate has varied, Y CVI is calculated as the total number of moles of silane / hour, for example, calculated as the total number of moles of silane delivered to the CVI reactor divided by the total CVI reaction time.

[0218] Table 8 includes the data of X Si . It can be seen that as Y CVI decreases, X SiSignificantly increased (see Figure 7 ). In some embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 1 and X Si > 50%. In a preferred embodiment of using CVI to manufacture silicon-carbon composites, Y CVI < 0.5 and X Si > 50%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.4 and X Si > 60%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.3 and X Si > 70%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.2 and X Si > 70%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.3 and X Si > 80%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.2 and X Si > 80%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.3 and X Si > 85%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.2 and X Si > 85%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.3 and X Si > 90%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.2 and X Si > 90%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.3 and X Si > 95%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.2 and X Si > 95%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.2 and X Si > 99%. In other preferred embodiments of using CVI to manufacture silicon-carbon composites, Y CVI < 0.1 and X Si> 90%. In other preferred embodiments of manufacturing silicon-carbon composites using CVI, Y CVI <0.1 and X Si > 95%. In other preferred embodiments of manufacturing silicon-carbon composites using CVI, Y CVI <0.1 and X Si > 99%. In other preferred embodiments of manufacturing silicon-carbon composites using CVI, Y CVI <0.05 and X Si > 90%. In other preferred embodiments of manufacturing silicon-carbon composites using CVI, Y CVI <0.05 and X Si > 95%. In other preferred embodiments of manufacturing silicon-carbon composites using CVI, Y CVI <0.05 and X Si > 99%. In other preferred embodiments of manufacturing silicon-carbon composites using CVI, Y CVI <0.01 and X Si > 90%. In other preferred embodiments of manufacturing silicon-carbon composites using CVI, Y CVI <0.01 and X Si > 95%. In other preferred embodiments of manufacturing silicon-carbon composites using CVI, Y CVI <0.01 and X Si > 99%.

[0219] Example 6. On-line process monitoring of silane utilization during the CVI process as determined by Fourier transform infrared (FTIR) spectroscopy. Fourier transform infrared (FTIR) spectroscopy is a suitable method for quantifying the gas concentration in the gas phase of silane gas. For this purpose, in order to prepare the silicon-carbon composite 21, the gas leaving the reactor was introduced into an airtight FTIR cell in an FTIR spectrometer. The silane concentration % of the gas leaving the reactor was quantified by expressing the silane concentration of the gas leaving the reactor as a percentage of the silane concentration entering the reactor: the peak height at 979 cm-1 in the FTIR spectrum of the gas leaving the reactor was measured, and this value was divided by the peak height at 979 cm-1 in the FTIR spectrum of the control (i.e., unreacted silane gas), and this value was multiplied by 100 to convert it into a percentage. Then the silane utilization % was calculated as 100 minus the silane concentration % of the gas leaving the reactor. Figure 8 On-line process data of silane utilization % as a function of the time of preparing sample 21 are described. It can be seen that the peak utilization is 98%. Without being bound by theory, based on the analysis from the previous examples, the silane flow rate during the initial and final CVI reaction stages can be adjusted (i.e., reduced) in order to increase the silane utilization during these stages. In this way, X can be further increasedSi , such as X Si greater than 85%, or X Si greater than 90%, or X Si greater than 95%, or X Si greater than or equal to 98%. Without being bound by theory, these data also demonstrate the feasibility of the CVI process in a continuous reactor, where an X greater than or equal to 98% can be achieved Si .

[0220] Example 7. A CVI process including recycle or recycle with a purge stream. The process for producing silicon-carbon composite particles can include a recycle stream. Thus, the gas leaving the CVI reactor can contain unreacted silane gas, hydrogen (produced due to the consumed silane), and a diluent gas (if used), and this gas stream can be reintroduced as one or more feed streams returning to the CVI reactor. In certain embodiments, the CVI reactor includes multiple zones, and the silane recycle stream can be fed as one or more feed streams into one or more of the zones of the CVI reactor. In certain embodiments, the recycle stream includes a purge stream. Thus, any hydrogen or diluent gas present in the recycle stream can be separated from the silane present in the recycle stream, for example, by gas separation techniques such as distillation or membrane gas separation. Using such a recycle stream or a recycle stream with a purge can further increase the net silane utilization rate, resulting in an X Si greater than 50%, such as greater than 60%, such as greater than 70%, such as greater than 85%, such as greater than 90%, such as greater than 95%, such as greater than 98%, such as greater than 99%.

[0221] Specific embodiments

[0222] Embodiment 1. A method for preparing silicon-carbon composite particles, the method comprising:

[0223] a. Providing a carbon support comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0224] b. Heating the porous carbon support to a temperature of 350 °C to 550 °C;

[0225] c. Providing a silane gas corresponding to Y CVI less than 0.5, wherein Y CVI =(moles of silane per hour) / (moles of carbon support); and

[0226] d. wherein the X of the method Si is greater than 50%, wherein X Si= 100 × (moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), where the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0227] Embodiment 2. A method for preparing silicon-carbon composite particles, the method comprising:

[0228] a. Providing a carbon support comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0229] b. Heating the porous carbon support to a temperature of 350 °C to 550 °C;

[0230] c. Providing a silane gas corresponding to Y CVI less than 0.5, where Y CVI = (moles of silane per hour) / (moles of carbon support);

[0231] d. Wherein X of the method Si is greater than 50%, where X Si = 100 × (moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), where the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0232] e. Wherein the silicon-carbon composite comprises:

[0233] i. A Z less than 10, where Z = 1.875x[(M1100 - M) / M1100]x100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from about 25 °C to about 1100 °C, as determined by thermogravimetric analysis.

[0234] Embodiment 3. A method for preparing silicon-carbon composite particles, the method comprising:

[0235] a. Providing a carbon support comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0236] b. Heating the porous carbon support to a temperature of 350 °C to 550 °C;

[0237] c. Providing a silane gas corresponding to Y CVI less than 0.5, where Y CVI = (moles of silane per hour) / (moles of carbon support);

[0238] d. Wherein X of the method Si is greater than 50%, where XSi = 100 × (the number of moles of silicon in the silicon-carbon composite) / (the number of moles of the silane raw material), where the number of moles of silicon in the silicon-carbon composite is determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0239] e. where the silicon-carbon composite comprises:

[0240] I. a where where dQ / dV is measured in a half-cell button battery, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0241] Embodiment 4. A method for preparing silicon-carbon composite particles, the method comprising:

[0242] a. providing a carbon support having a pore volume, where the pore volume comprises more than 70% micropores;

[0243] b. heating the porous carbon support to a temperature of 350°C to 550°C;

[0244] c. providing a silane gas corresponding to Y CVI less than 0.5, where Y CVI =

[0245] (the number of moles of silane per hour) / (the number of moles of the carbon support);

[0246] d. where X of the method Si is greater than 50%, where X Si = 100 × (the number of moles of silicon

[0247] - in the carbon composite) / (the number of moles of the silane raw material), where

[0248] the number of moles of silicon in the silicon-carbon composite is determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0249] e. where the silicon-carbon composite comprises:

[0250] i. a silicon content of 30% to 60% by weight;

[0251] ii. a Z less than 10, where Z = 1.875x[(M1100 -

[0252] (M) / M1100] x 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from approximately 25 °C to approximately 1100 °C, determined by thermogravimetric analysis;

[0253] iii. A surface area of less than 30 m 2 / g; and

[0254] iv. Greater than or equal to 0.1 where

[0255] where dQ / dV is measured in a half-cell button cell, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0256] Embodiment 5. A method for preparing silicon-carbon composite particles, the method comprising:

[0257] a. Providing a carbon scaffold comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0258] b. Heating the porous carbon scaffold to a temperature of 350 °C to 550 °C;

[0259] c. Providing a silane gas corresponding to Y CVI less than 0.4, where Y CVI =

[0260] (moles of silane per hour) / (moles of carbon scaffold); and

[0261] d. Wherein X of the method Si is greater than 60%, where X Si = 100 × (moles of silicon in the silicon

[0262] -carbon composite) / (moles of silane feedstock), where

[0263] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0264] Embodiment 6. A method for preparing silicon-carbon composite particles, the method comprising:

[0265] a. Providing a carbon scaffold comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0266] b. Heating the porous carbon scaffold to a temperature of 350 °C to 550 °C;

[0267] c. Providing a corresponding to YCVI Silane gas less than 0.4, where Y CVI =

[0268] (moles of silane per hour) / (moles of carbon support);

[0269] d. where X of the method Si is greater than 60%, where X Si = 100×(silicon

[0270] - moles of silicon in the carbon complex) / (moles of silane feedstock), where

[0271] the moles of silicon in the silicon - carbon complex are determined from the silicon content in the silicon - carbon complex by thermogravimetric analysis; and

[0272] e. where the silicon - carbon complex contains:

[0273] i. Z less than 10, where Z = 1.875x[(M1100 -

[0274] M) / M1100]x 100, where M1100 is the mass of the silicon - carbon complex at 1100 °C, and M is the minimum mass of the silicon - carbon complex between 800 °C and 1100 °C when the silicon - carbon complex is heated in air from about 25 °C to about 1100 °C, determined by thermogravimetric analysis.

[0275] Embodiment 7. A method for preparing silicon - carbon composite particles, the method comprising:

[0276] a. Providing a carbon support having a pore volume, where the pore volume contains more than 70% micropores;

[0277] b. Heating the porous carbon support to a temperature of 350 °C to 550 °C;

[0278] c. Providing silane gas corresponding to Y CVI less than 0.4, where Y CVI =

[0279] (moles of silane per hour) / (moles of carbon support);

[0280] d. where X of the method Si is greater than 60%, where X Si = 100×(silicon

[0281] - moles of silicon in the carbon complex) / (moles of silane feedstock), where

[0282] the moles of silicon in the silicon - carbon complex are determined from the silicon content in the silicon - carbon complex by thermogravimetric analysis; and

[0283] e. wherein the silicon-carbon composite comprises:

[0284] i. Greater than or equal to 0.1 in

[0285] Where dQ / dV is measured in a half-cell coin cell and region I is 0.8V-0.4V and region III is 0.15V-0V.

[0286] Embodiment 8. A method for preparing silicon-carbon composite particles, the method comprising:

[0287] a. Providing a carbon scaffold comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0288] b. heating the porous carbon support to a temperature of 350°C to 550°C;

[0289] c. Provide the corresponding CVI Less than 0.4 silane gas, where Y CVI =

[0290] (moles of silane / hour) / (moles of carbon scaffold);

[0291] d. wherein the method X Si Greater than 60%, where X Si =100×(Silicon

[0292] -(moles of silicon in the carbon composite) / (moles of silane raw material), wherein

[0293] The number of moles of silicon in the silicon-carbon composite is determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0294] e. wherein the silicon-carbon composite comprises:

[0295] i. a silicon content of 30% to 60% by weight;

[0296] ii. Z less than 10, where Z = 1.875x[(M1100-

[0297] M) / M1100] x 100, wherein M1100 is the mass of the silicon-carbon composite at 1100° C., and M is the minimum mass of the silicon-carbon composite between 800° C. and 1100° C. when the silicon-carbon composite is heated from about 25° C. to about 1100° C. in air, as determined by thermogravimetric analysis;

[0298] iii. Less than 30m 2 / g surface area; and

[0299] iv. greater than or equal to 0.1 wherein

[0300] wherein dQ / dV is measured in a half-cell button battery, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0301] Embodiment 9. A method for preparing silicon-carbon composite particles, the method comprising:

[0302] a. providing a carbon scaffold comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0303] b. heating the porous carbon scaffold to a temperature of 350°C to 550°C;

[0304] c. providing a silane gas corresponding to Y CVI less than 0.2, where Y CVI = (moles of silane per hour) / (moles of carbon scaffold); and

[0305] d. wherein X of the method Si is greater than 70%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0306] Embodiment 10. A method for preparing silicon-carbon composite particles, the method comprising:

[0307] a. providing a carbon scaffold comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0308] b. heating the porous carbon scaffold to a temperature of 350°C to 550°C;

[0309] c. providing a silane gas corresponding to Y CVI less than 0.2, where Y CVI = (moles of silane per hour) / (moles of carbon scaffold);

[0310] d. wherein X of the method Si is greater than 70%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0311] e. wherein the silicon-carbon composite comprises:

[0312] i. Z less than 10, where Z = 1.875x[(M1100 - M) / M1100]x100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from about 25 °C to about 1100 °C, as determined by thermogravimetric analysis.

[0313] Embodiment 11. A method for preparing silicon-carbon composite particles, the method comprising:

[0314] a. providing a carbon scaffold comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0315] b. heating the porous carbon scaffold to a temperature of 350 °C to 550 °C;

[0316] c. providing a silane gas corresponding to Y CVI less than 0.2, where Y CVI =

[0317] (moles of silane per hour) / (moles of carbon scaffold);

[0318] d. wherein X of the method Si is greater than 70%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), where

[0319] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0320] the moles of silicon in the silicon-carbon composite are measured by thermogravimetric analysis from the silicon content in the silicon-carbon composite; and

[0321] e. wherein the silicon-carbon composite comprises:

[0322] i. greater than or equal to 0.1 where

[0323] where dQ / dV is measured in a half-cell button battery, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0324] Embodiment 12. A method for preparing silicon-carbon composite particles, the method comprising:

[0325] a. providing a carbon scaffold comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0326] b. Heat the porous carbon support to a temperature of 350°C to 550°C;

[0327] c. Provide a silane gas corresponding to Y CVI less than 0.2, where Y CVI =

[0328] (moles of silane per hour) / (moles of carbon support);

[0329] d. Where X Si of the method is greater than 70%, where X Si = 100 × (moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), where

[0330] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0331]

[0332] e. Where the silicon-carbon composite comprises:

[0333] i. A silicon content of 30% to 60% by weight;

[0334] ii. A Z less than 10, where Z = 1.875x[(M1100 -

[0335] M) / M1100] x 100, where M1100 is the mass of the silicon-carbon composite at 1100°C and M is the minimum mass of the silicon-carbon composite between 800°C and 1100°C when the silicon-carbon composite is heated in air from about 25°C to about 1100°C, determined by thermogravimetric analysis;

[0336] iii. A surface area less than 30 m 2 / g; and

[0337] iv. A greater than or equal to 0.1 where

[0338] where dQ / dV is measured in a half-cell button battery and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0339] Embodiment 13. A method for preparing silicon-carbon composite particles, the method comprising:

[0340] a. Provide a carbon support having a pore volume, where the pore volume comprises greater than 70% micropores;

[0341] b. Heat the porous carbon support to a temperature of 350°C to 550°C;

[0342] c. Provide corresponding to Y CVI a silane gas less than 0.2, where Y CVI =

[0343] (moles of silane per hour) / (moles of carbon support); and

[0344] d. where X of the method Si is greater than 85%, where X Si = 100×(moles of silicon in the silicon

[0345] -carbon composite) / (moles of silane feedstock), where

[0346] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0347] Embodiment 14. A method for preparing silicon-carbon composite particles, the method comprising:

[0348] a. Providing a carbon support having a pore volume, where the pore volume contains greater than 70% micropores;

[0349] b. Heating the porous carbon support to a temperature of 350 °C to 550 °C;

[0350] c. Providing a silane gas corresponding to Y CVI less than 0.2, where Y CVI =

[0351] (moles of silane per hour) / (moles of carbon support);

[0352] d. where X of the method Si is greater than 85%, where X Si = 100×(silicon

[0353] -carbon composite moles of silicon) / (moles of silane feedstock), where

[0354] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0355] e. where the silicon-carbon composite comprises:

[0356] i. a Z less than 10, where Z = 1.875x[(M1100 -

[0357] M) / M1100] x 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from about 25 °C to about 1100 °C, determined by thermogravimetric analysis.

[0358] Embodiment 15. A method for preparing silicon-carbon composite particles, the method comprising:

[0359] a. Providing a carbon support comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0360] b. Heating the porous carbon support to a temperature of 350 °C to 550 °C;

[0361] c. Providing a silane gas corresponding to Y CVI less than 0.2, where Y CVI =

[0362] (moles of silane per hour) / (moles of carbon support);

[0363] d. Wherein X Si of the method is greater than 85%, where X Si = 100 × (moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), where

[0364] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0365] e. Wherein the silicon-carbon composite comprises:

[0366] i. greater than or equal to 0.1

[0367] where where

[0368] where dQ / dV is measured in a half-cell button battery, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0369] Embodiment 16. A method for preparing silicon-carbon composite particles, the method comprising:

[0370] a. Providing a carbon support comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0371] b. Heating the porous carbon support to a temperature of 350 °C to 550 °C;

[0372] c. Providing a silane gas corresponding to Y CVISilane gas less than 0.2, where Y CVI =

[0373] (moles of silane per hour) / (moles of carbon support);

[0374] d. where X of the method Si is greater than 85%, where X Si = 100×(moles of silicon in the silicon

[0375] -carbon composite) / (moles of silane feedstock), where

[0376] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0377] e. where the silicon-carbon composite comprises:

[0378] i. a silicon content of 30% to 60% by weight;

[0379] ii. a Z less than 10, where Z = 1.875x[(M1100 -

[0380] M) / M1100]x 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from about 25 °C to about 1100 °C, determined by thermogravimetric analysis;

[0381] iii. a surface area less than 30 m 2 / g; and

[0382] iv. greater than or equal to 0.1 of where

[0383] where dQ / dV is measured in a half-cell button cell, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0384] Embodiment 17. A method for preparing silicon-carbon composite particles, the method comprising:

[0385] a. providing a carbon support having a pore volume, where the pore volume comprises greater than 70% micropores;

[0386] b. heating the porous carbon support to a temperature of 350 °C to 550 °C;

[0387] c. providing silane gas corresponding to Y CVI less than 0.2, where Y CVI =

[0388] (moles of silane per hour) / (moles of carbon support); and

[0389] d. wherein X of the method Si is greater than 90%, where X Si = 100 × (moles of silicon in the silicon

[0390] -carbon composite) / (moles of silane feedstock), where

[0391] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0392] Embodiment 18. A method for preparing silicon-carbon composite particles, the method comprising:

[0393] a. providing a carbon support having a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0394] b. heating the porous carbon support to a temperature of 350 °C to 550 °C;

[0395] c. providing a silane gas corresponding to Y CVI less than 0.2, where Y CVI =

[0396] (moles of silane per hour) / (moles of carbon support);

[0397] d. wherein X of the method Si is greater than 90%, where X Si = 100 × (silicon

[0398] -carbon composite moles of silicon) / (moles of silane feedstock), where

[0399] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0400] e. wherein the silicon-carbon composite comprises:

[0401] i. a Z less than 10, where Z = 1.875x[(M1100 -

[0402] M) / M1100] x 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from about 25 °C to about 1100 °C, as determined by thermogravimetric analysis.

[0403] Embodiment 19. A method for preparing silicon-carbon composite particles, the method comprising:

[0404] a. Providing a carbon scaffold comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0405] b. Heating the porous carbon scaffold to a temperature of 350 °C to 550 °C;

[0406] c. Providing a silane gas corresponding to Y CVI less than 0.2, wherein Y CVI =

[0407] (moles of silane per hour) / (moles of carbon scaffold);

[0408] d. Wherein X Si of the method is greater than 90%, wherein X Si = 100 × (silicon

[0409] - moles of silicon in the carbon composite) / (moles of silane feedstock), wherein

[0410] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0411] e. Wherein the silicon-carbon composite comprises:

[0412] i. greater than or equal to 0.1 of wherein

[0413] wherein dQ / dV is measured in a half-cell button battery, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V. Embodiment 20. A method for preparing silicon-carbon composite particles, the method comprising:

[0414] a. Providing a carbon scaffold comprising a pore volume, wherein the pore volume comprises greater than 70% micropores;

[0415] b. Heating the porous carbon scaffold to a temperature of 350 °C to 550 °C;

[0416] c. Providing a silane gas corresponding to Y CVI less than 0.2, wherein Y CVI =

[0417] (moles of silane per hour) / (moles of carbon scaffold);

[0418] d. Wherein X Si of the method is greater than 90%, wherein X Si = 100 × (silicon

[0419] (moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), where

[0420] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0421] e. where the silicon-carbon composite comprises:

[0422] i. a silicon content of 30% to 60% by weight;

[0423] ii. a Z less than 10, where Z = 1.875 x [(M1100 -

[0424] M) / M1100] x 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from about 25 °C to about 1100 °C, as determined by thermogravimetric analysis;

[0425] iii. a surface area less than 30 m 2 / g; and

[0426] iv. a where where dQ / dV is measured in a half-cell button battery, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0427] Embodiment 21. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 20, wherein the pore volume comprises more than 80% micropores.

[0428] Embodiment 22. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 21, wherein the pore volume comprises more than 90% micropores.

[0429] Embodiment 23. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 22, wherein the pore volume comprises more than 95% micropores.

[0430] Embodiment 24. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 23, wherein the temperature is 400 °C to 525 °C.

[0431] Embodiment 25. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 24, wherein the silicon-carbon composite contains a silicon content of 40-60%.

[0432] Embodiment 26. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 25, wherein the silicon-carbon composite contains a Z of less than 5.

[0433] Embodiment 27. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 26, wherein the silicon-carbon composite has a surface area of less than 10 m 2 / g.

[0434] Embodiment 28. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 27, wherein the silicon-carbon composite contains a wherein wherein dQ / dV is measured in a half-cell button battery, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0435] Embodiment 29. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 28, wherein the silicon-carbon composite contains a wherein wherein dQ / dV is measured in a half-cell button battery, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0436] Embodiment 30. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 29, wherein the silicon-carbon composite has a Dv50 of 5 nm to 20 microns.

[0437] Embodiment 31. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 30, wherein the silicon-carbon composite has a capacity of greater than 900 mAh / g.

[0438] Embodiment 32. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 31, wherein the silicon-carbon composite has a capacity of greater than 1300 mAh / g.

[0439] Embodiment 33. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 32, wherein the silicon-carbon composite has a capacity greater than 1600 mAh / g.

[0440] Embodiment 34. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 33, wherein the method is a batch method.

[0441] Embodiment 35. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 34, wherein the method is a continuous method.

[0442] Embodiment 36. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 35, wherein the reactor type is a fixed-bed reactor, a horizontal moving-bed reactor, a vibration-thermal assisted reactor, a convection-thermal assisted reactor, or a fluidized-bed reactor.

[0443] Embodiment 37. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 36, wherein the concentration of the silane is 1.25% to 100% in terms of the mass fraction of the total gas composition.

[0444] Embodiment 38. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 36, wherein the gas includes silane and an inert gas selected from nitrogen, hydrogen, argon, or helium or a combination thereof.

[0445] Embodiment 39. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 38, wherein the areal loading of the carbon support is 0.001 g / cm 2 to 10 g / cm 2 .

[0446] Embodiment 40. An energy storage device comprising the silicon-carbon composite prepared according to any one of Embodiments 1 to 39.

[0447] Embodiment 41. A lithium-ion battery comprising the silicon-carbon composite prepared according to any one of Embodiments 1 to 39.

[0448] Embodiment 42. A method for preparing silicon-carbon composite particles, the method comprising:

[0449] a. Providing a carbon support comprising a pore volume, wherein the pore volume comprises one or more micropores and one or more mesopores;

[0450] b. Heat the porous carbon support to a temperature of 350 °C to 550 °C in the presence of silane gas; and

[0451] c. wherein X of the method Si is greater than 50%, where X Si = 100 × (moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0452] Embodiment 43. A method for preparing silicon-carbon composite particles, the method comprising:

[0453] a. Providing a carbon support comprising a pore volume, wherein the pore volume comprises one or more micropores and one or more mesopores;

[0454] b. Heating the porous carbon support to a temperature of 350 °C to 550 °C in the presence of silane gas;

[0455] c. wherein X of the method Si is greater than 50%, where X Si = 100 × (silicon

[0456] - moles of silicon in the carbon composite) / (moles of silane feedstock), where

[0457] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0458] d. wherein the silicon-carbon composite comprises:

[0459] ii. Z less than 10, where Z = 1.875x[(M1100 -

[0460] M) / M1100]x 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from about 25 °C to about 1100 °C, determined by thermogravimetric analysis.

[0461] Embodiment 44. A method for preparing silicon-carbon composite particles, the method comprising:

[0462] a. Providing a carbon support comprising a pore volume, wherein the pore volume comprises one or more micropores and one or more mesopores;

[0463] b. Heating the porous carbon support to a temperature of 350 °C to 550 °C in the presence of silane gas;

[0464] c. wherein X of the methodSi Greater than 50%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), where

[0465] the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0466]

[0467] d. where the silicon-carbon composite comprises:

[0468] ii. greater than or equal to 0.1 of where

[0469] where dQ / dV is measured in a half-cell button cell, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0470] Embodiment 45. A method for preparing silicon-carbon composite particles, the method comprising:

[0471] a. providing a carbon scaffold comprising a pore volume, where the pore volume comprises one or more micropores and one or more mesopores;

[0472] b. heating the porous carbon scaffold to a temperature of 350°C to 550°C in the presence of silane gas;

[0473] c. where the X of the method Si is greater than 50%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane feedstock), where the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and

[0474] d. where the silicon-carbon composite comprises:

[0475] v. a silicon content of 30% to 70% by weight;

[0476] vi. a Z less than 10, where Z = 1.875x[(M1100 - M) / M1100]x100, where M1100 is the mass of the silicon-carbon composite at 1100°C, and M is the minimum mass of the silicon-carbon composite between 800°C and 1100°C when the silicon-carbon composite is heated in air from about 25°C to about 1100°C, as determined by thermogravimetric analysis;

[0477] vii. a surface area less than 30 m 2 / g; and ​

[0478] viii. greater than or equal to 0.1 wherein where dQ / dV is measured in a half-cell button cell, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

[0479] Embodiment 46. The method for preparing silicon-carbon composite particles according to Embodiment 42, wherein X Si is greater than 60%, wherein X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0480] Embodiment 47. The method for preparing silicon-carbon composite particles according to Embodiment 43, wherein X Si is greater than 60%, wherein X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0481] Embodiment 48. The method for preparing silicon-carbon composite particles according to Embodiment 44, wherein X Si is greater than 60%, wherein X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0482] Embodiment 49. The method for preparing silicon-carbon composite particles according to Embodiment 45, wherein X Si is greater than 60%, wherein X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0483] Embodiment 50. The method for preparing silicon-carbon composite particles according to Embodiment 42, wherein X Si is greater than 70%, wherein X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0484] Embodiment 51. The method for preparing silicon-carbon composite particles according to Embodiment 43, wherein X Si is greater than 70%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0485] Embodiment 52. The method for preparing silicon-carbon composite particles according to Embodiment 44, wherein X Si is greater than 70%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0486] Embodiment 53. The method for preparing silicon-carbon composite particles according to Embodiment 45, wherein X Si is greater than 70%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0487] Embodiment 54. The method for preparing silicon-carbon composite particles according to Embodiment 42, wherein X Si is greater than 85%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0488] Embodiment 55. The method for preparing silicon-carbon composite particles according to Embodiment 43, wherein X Si is greater than 85%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0489] Embodiment 56. The method for preparing silicon-carbon composite particles according to Embodiment 44, wherein X Si is greater than 85%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0490] Embodiment 57. The method for preparing silicon-carbon composite particles according to Embodiment 45, wherein X Si is greater than 85%, wherein X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0491] Embodiment 58. The method for preparing silicon-carbon composite particles according to Embodiment 42, wherein X Si is greater than 90%, wherein X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0492] Embodiment 59. The method for preparing silicon-carbon composite particles according to Embodiment 43, wherein X Si is greater than 90%, wherein X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0493] Embodiment 60. The method for preparing silicon-carbon composite particles according to Embodiment 44, wherein X Si is greater than 90%, wherein X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0494] Embodiment 61. The method for preparing silicon-carbon composite particles according to Embodiment 45, wherein X Si is greater than 90%, wherein X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane raw material), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

[0495] Embodiment 62. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 61, wherein the silane gas includes a recycle stream.

[0496] Embodiment 63. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 61, wherein the silane gas includes a recycle stream, and the recycle stream includes a purge stream.

[0497] Embodiment 64. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 64, wherein for a voltage window of 5 mV to 0.8 V, when measured in a half-cell, the silicon-carbon composite particles have a first-cycle efficiency of >75%.

[0498] Embodiment 65. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 64, wherein for a voltage window of 5 mV to 0.8 V, when measured in a half-cell, the silicon-carbon composite particles have a first-cycle efficiency of >80%.

[0499] Embodiment 66. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 64, wherein for a voltage window of 5 mV to 1.5 V, when measured in a half-cell, the silicon-carbon composite particles have a first-cycle efficiency of >85%.

[0500] Embodiment 67. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 64, wherein for a voltage window of 5 mV to 1.5 V, when measured in a half-cell, the silicon-carbon composite particles have a first-cycle efficiency of >90%.

[0501] Embodiment 68. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 64, wherein for a voltage window of 5 mV to 1.5 V, when measured in a half-cell, the silicon-carbon composite particles have a first-cycle efficiency of >91%.

[0502] Embodiment 69. The method for preparing silicon-carbon composite particles according to any one of Embodiments 1 to 64, wherein for a voltage window of 5 mV to 1.5 V, when measured in a half-cell, the silicon-carbon composite particles have a first-cycle efficiency of >92%.

[0503] It can be understood from the above that although specific embodiments of the present invention have been described herein for illustrative purposes, various modifications can be made without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited except as limited by the appended claims.

[0504] All U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications, and non-patent publications mentioned in this specification and / or listed in the application data sheet, including but not limited to U.S. application serial number 16 / 996,694 filed on August 18, 2020, U.S. provisional patent application serial number 63 / 075,566 filed on September 8, 2020, and U.S. provisional patent application serial number 63 / 078,806 filed on September 15, 2020, are hereby incorporated by reference in their entirety.

Claims

1. A method for preparing silicon-carbon composite particles, the method comprising: a. Provide a carbon scaffold comprising a pore volume, wherein the pore volume comprises more than 70% micropores; b. Heat the carbon scaffold to a temperature of 350 °C to 550 °C; c. Contact the carbon support with a silane source gas corresponding to Y CVI less than 0.5, where Y CVI = (moles of silane source gas per hour) / (moles of carbon support); and d. Wherein X of the method Si is greater than 60%, where X Si = 100 × (moles of silicon in the silicon-carbon composite) / (moles of silane feed gas), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; wherein the silicon-carbon composite particles comprise a Z of less than 10, where Z = 1.875 × [(M1100 - M) / M1100] × 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from 25 °C to 1100 °C, as determined by thermogravimetric analysis.

2. A method for preparing silicon-carbon composite particles, the method comprising: a. Provide a carbon scaffold comprising a pore volume, wherein the pore volume comprises more than 70% micropores; b. Heat the carbon scaffold to a temperature of 350 °C to 550 °C; c. Contact the carbon support with a silane source gas corresponding to Y CVI less than 0.3, where Y CVI = (moles of silane source gas per hour) / (moles of carbon support); and d. wherein X of the method Si is greater than 70%, where X Si = 100 × (moles of silicon in the silicon-carbon composite) / (moles of silane feed gas), where the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; wherein the silicon-carbon composite particles comprise a Z of less than 10, where Z = 1.875 × [(M1100 - M) / M1100] × 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from 25 °C to 1100 °C, as determined by thermogravimetric analysis.

3. The method for preparing silicon-carbon composite particles according to claim 2, wherein X Si of the method is greater than 85%, where X Si = 100×(moles of silicon in the silicon-carbon composite) / (moles of silane feed gas), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis.

4. A method for preparing silicon-carbon composite particles, the method comprising: a. Provide a carbon scaffold comprising a pore volume, wherein the pore volume comprises more than 90% micropores; b. Heat the carbon scaffold to a temperature of 350 °C to 550 °C; c. Contact the carbon support with a silane source gas corresponding to Y CVI less than 0.3, where Y CVI = (moles of silane source gas per hour) / (moles of carbon support); d. wherein X of the method Si is greater than 85%, where X Si = 100 × (moles of silicon in the silicon-carbon composite) / (moles of silane feed gas), wherein the moles of silicon in the silicon-carbon composite are determined from the silicon content in the silicon-carbon composite by thermogravimetric analysis; and e. wherein the silicon-carbon composite particles comprise: i. a silicon content of 40% to 60% by weight; ii. a Z of less than 10, where Z = 1.875 × [(M1100 - M) / M1100] × 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from 25 °C to 1100 °C, as determined by thermogravimetric analysis; iii. less than 30 m 2 / g surface area; and iv. greater than or equal to 0.1 wherein wherein dQ / dV is measured in a half-cell button cell, and Region I is 0.8V - 0.4V and Region III is 0.15V - 0V.

5. The method for preparing silicon-carbon composite particles according to claim 1, wherein the pore volume comprises more than 90% micropores.

6. The method for preparing silicon-carbon composite particles according to claim 2, wherein the pore volume comprises more than 90% micropores.

7. The method for preparing silicon-carbon composite particles according to claim 3, wherein the pore volume comprises more than 90% micropores.

8. The method for preparing silicon-carbon composite particles according to claim 1, wherein the silicon-carbon composite particles have a surface area of less than 10 m 2 / g.

9. The method for preparing silicon-carbon composite particles according to claim 2, wherein the silicon-carbon composite particles have a surface area of less than 10 m 2 / g.

10. The method for preparing silicon-carbon composite particles according to claim 3, wherein the silicon-carbon composite particles have a surface area of less than 10 m 2 / g.

11. The method for preparing silicon-carbon composite particles according to claim 4, wherein the silicon-carbon composite particles have a surface area of less than 10 m 2 / g.

12. The method for preparing silicon-carbon composite particles according to claim 1, wherein the silicon-carbon composite particles have a Dv50 of 5 nm to 20 microns.

13. The method for preparing silicon-carbon composite particles according to claim 2, wherein the silicon-carbon composite particles have a Dv50 of 5 nm to 20 microns.

14. The method for preparing silicon-carbon composite particles according to claim 3, wherein the silicon-carbon composite particles have a Dv50 of 5 nm to 20 microns.

15. The method for preparing silicon-carbon composite particles according to claim 4, wherein the silicon-carbon composite particles have a Dv50 of 5 nm to 20 microns.

16. The method for preparing silicon-carbon composite particles according to claim 1, wherein the silicon-carbon composite particles have a wherein wherein dQ / dV is measured in a half-cell button battery, and Region I is 0.8 V - 0.4 V and Region III is 0.15 V - 0 V.

17. The method for preparing silicon-carbon composite particles according to claim 1, wherein the silicon-carbon composite particles comprise: a. a silicon content of 40% to 60% by weight; b. a Z of less than 10, where Z = 1.875 × [(M1100 - M) / M1100] × 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated in air from 25 °C to 1100 °C, as determined by thermogravimetric analysis; c. a surface area of less than 30 m 2 / g; and d. greater than or equal to 0.1 wherein where dQ / dV is measured in a half-cell button battery, and Region I is 0.8 V - 0.4 V and Region III is 0.15 V - 0 V.

18. The method for preparing silicon-carbon composite particles according to claim 2, wherein the silicon-carbon composite particles comprise: a. a silicon content of 40% to 60% by weight; b. a Z less than 10, where Z = 1.875 × [(M1100 - M) / M1100] × 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated from 25 °C to 1100 °C in air, as determined by thermogravimetric analysis; c. a surface area less than 30 m 2 / g; and d. greater than or equal to 0.1 wherein where dQ / dV is measured in a half-cell button battery, and Region I is 0.8 V - 0.4 V and Region III is 0.15 V - 0 V.

19. The method for preparing silicon-carbon composite particles according to claim 3, wherein the silicon-carbon composite particles comprise: a. a silicon content of 40% to 60% by weight; b. a Z less than 10, where Z = 1.875 × [(M1100 - M) / M1100] × 100, where M1100 is the mass of the silicon-carbon composite at 1100 °C, and M is the minimum mass of the silicon-carbon composite between 800 °C and 1100 °C when the silicon-carbon composite is heated from 25 °C to 1100 °C in air, as determined by thermogravimetric analysis; c. a surface area less than 30 m 2 / g; and d. greater than or equal to 0.1 wherein where dQ / dV is measured in a half-cell button battery, and Region I is 0.8 V - 0.4 V and Region III is 0.15 V - 0 V.

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